# New insights into the diversity of strepsirrhine primates from the late early – early middle Eocene of North Africa (Algeria and Tunisia)

Laurent Marivaux, Anne-Lise Charruault, Mohammed Adaci, Mustapha Bensalah, Mahammed Mahboubi, Fateh Mebrouk, Hayet Khayati Ammar, El Mabrouk Essid, Wissem Marzougui, Rim Temani, et al.

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## To cite this version:

Laurent Marivaux, Anne-Lise Charruault, Mohammed Adaci, Mustapha Bensalah, Mahammed Mahboubi, et al. New insights into the diversity of strepsirrhine primates from the late early – early middle Eocene of North Africa (Algeria and Tunisia). Journal of Human Evolution, 2025, 206, pp.103729. 10.1016/j.jhevol.2025.103729. hal-05125090

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Submitted on 21 Jul 2025

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New insights into the diversity of strepsirrhine primates from the late early – early middle Eocene of North Africa (Algeria and Tunisia)

Laurent Marivaux a, *, Anne-Lise Charruault a, Mohammed Adaci b, Mustapha Bensalah b, Mahammed Mahboubi c, Fateh Mebrouk d, Hayet Khayati Ammar e, El Mabrouk Essid e, Wissem Marzougui e, Rim Temani e, Rodolphe Tabuce a

ORCID numbers (available):

Laurent Marivaux: 0000-0002-2882-0874

Anne-Lise Charruault: 0009-0005-0721-4081

Mohammed Adaci: 0000-0002-9839-716X

Mustapha Bensalah: 0000-0002-2890-2669

M'Hammed Mahboubi: 0000-0002-8934-2167

Fateh Mebrouk: 0000-0002-5221-7530

El Mabrouk Essid: 0000-0003-3357-8258

Wissem Marzougui: 0000-0001-7643-0697

Rim Temani: 0000-0001-8508-1767

Rodolphe Tabuce: 0000-0002-4713-3981

<footnote>a Laboratoire de Paléontologie, Institut des Sciences de l'Évolution de Montpellier (ISE-M, UMR 5554, CNRS/UM/IRD/EPHE), c.c. 064, Université de Montpellier, place Eugène Bataillon, F-34095 Montpellier Cedex 05, France</footnote>

<footnote>b Laboratoire de Recherche n°25, Université de Tlemcen Abou Bekr Belkaïd, BP. 119, Tlemcen 13000, Algeria</footnote>

<footnote>c Laboratoire de Paléontologie, Stratigraphie et Paléoenvironnement, Université d'Oran 2, BP. 1524, El M'Naouer, Oran 31000, Algeria</footnote>

<footnote>d Laboratoire de Génie Civil et Environnement (LGCE) & Département des Sciences de la Terre et de l'Univers, Faculté des Sciences de la Nature et de la Vie, Université Mohamed Seddik Ben Yahia - Jijel, BP. 98 Cité Ouled Aïssa, 18000 Jijel, Algeria</footnote>

<footnote>e Office National des Mines (ONM), 24 rue 8601, 2035 La Charguia, Tunis, Tunisia</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: Laurent.Marivaux@UMontpellier.fr (L. Marivaux)</footnote>
ABSTRACT

The Gour Lazib Complex in Algeria and Djebel Chambi in Tunisia are the only African regions with abundant fossil records of diverse mammals dating from the late early to early middle Eocene. Among these mammals, primates, documented by few dental remains, have long attracted much attention for their possible role in the African origin of the group to which we belong, the anthropoids. Continuing fieldwork at these localities has uncovered new dental, cranial and postcranial remains of these primates, shedding new light on their phylogenetic status. These primates, Azibiidae and Djebelemuridae, are now recognized as 'advanced' stem strepsirrhines, i.e., more closely related to crown Strepsirrhini (tooth-combed primates) than to any Adapiformes (other stem strepsirrhines, lacking a tooth-comb). Here, we illustrate and describe new fossil specimens (dental only) recently recovered from these two former sites. From the Gour Lazib Complex (including Glib Zegdou), in addition to the previously known azibiid taxa, *Azibius trerki* and *Algeripithecus minutus*, we describe a new, larger azibiid, *Azibius magnus* sp. nov., and a tiny new taxon, *Lazibadapis anchomomyinopsis* gen. et sp. nov., which could be a basal djebelemurid. New deciduous teeth and illustrations of earlier fossil taxa are also provided. From Chambi, in addition to *Djebelemur martinezi*, we identify a small azibiid, previously recognized among *Djebelemur* paratypes, and describe a new species, *Algeripithecus minimissimus* sp. nov., based on additional dental material. These new fossils extend our knowledge of the paleodiversity of these two extinct strepsirrhine families, and reveal their wider paleogeographic distribution across North Africa at the onset of the Eocene. Azibiidae were highly specialized, likely feeding on a mixed diet of exudates and fruit. This specialization allowed for remarkable diversity but ultimately led to their extinction, possibly due to ecological constraints, although the factors remain unclear due to gaps in the fossil record. The less specialized Djebelemuridae, which had an insectivorous diet, lasted longer but also went extinct by the early Oligocene. These findings have significant implications for the macroevolutionary, paleobiological and paleogeographical history of early primates in Africa during the Eocene.

Keywords: Paleogene; Northern Africa; Maghreb; Gour Lazib; Chambi; Strepsirrhini; Azibiidae; Djebelemuridae
# 1. Introduction

During the Cenozoic, Afro-Arabia was one of the major centers of primate diversification, not only of strepsirrhines but also of anthropoids (e.g., Godinot, 2010; Seiffert et al., 2010; Seiffert, 2012), and in particular the cradle of the emergence of our own group (e.g., Simons, 1965; Harrison, 2010; MacLatchy et al., 2010). However, even today, compared to Eurasia and North America, very little is known about the earliest primate forms that inhabited Africa at the beginning of this era. The few fossils that document Africa's first primates come from a handful of localities, mainly situated in the Maghreb region in the north of the continent (Morocco, Algeria, and Tunisia), but also in sub-Saharan Africa (Namibia), where only one locality is known. In addition to *Altiatlasius* from the latest Paleocene of Adrar Mgorn (Morocco; Sigé et al., 1990; Gheerbrant et al., 1998), which is one of the oldest crown Primates candidates, *Azibius* and *Algeripithecus* (Sudre, 1975; Godinot and Mahboubi, 1992, 1994; Tabuce et al., 2009) as well as *Djebelemur* (Hartenberger and Marandat, 1992; Marivaux et al., 2013) from the late early to early middle Eocene of the Gour Lazib Complex (Algeria) and Djebel Chambi (Tunisia), respectively, cf. *?Altiatlasius* from the middle Eocene of Aznag (Morocco; Tabuce et al., 2005), and *Namadapis* and *Notnamaia* from the middle Eocene of Sperrgebiet-Black Crow (Namibia; Pickford et al., 2008; Godinot et al., 2018), are so far the only undoubted primates to be known for this early Cenozoic time window in Africa. *Altiatlasius* remains an enigmatic primate taxon due to its primitive dental pattern, which makes it difficult to elucidate its phylogenetic affinities (e.g., Sigé et al., 1990; Hooker et al., 1999; Beard, 2004, 2006; Marivaux, 2006; Seiffert et al., 2010; Seiffert, 2012; Ni et al., 2013). In contrast, regardless of their controversial original status based on limited dental evidence, *Azibius*<fnref n="1" /> and *Algeripithecus*<fnref n="2" /> (Azibiidae) as well as *Djebelemur*<fnref n="3" /> (Djebelemuridae) are now all considered to be ‘advanced’ stem strepsirrhines (also known as ‘pre-tooth-combed’ primates<fnref n="4" />) in light of the more complete morpho-paleontological data gathered in recent decades (Tabuce et al., 2009; Marivaux et al., 2011a, 2013; Benoit et al., 2013). *Azibius* and *Algeripithecus* are highly specialized, particularly autapomorphous in their upper and lower premolar patterns, and have been regarded as representing ‘an aberrant group of stem strepsirrhines’ (Tabuce et al., 2009, pp. 4093), if not ‘some of the more bizarre primates’.

<footnote n="1">¹ Plesiadapiform status (Sudre, 1975; Tabuce et al., 2004), but also other taxonomic affinities (see Szalay, 1975; Gingerich, 1976; Sudre, 1979; Holroyd and Simons, 1991; Hartenberger et al., 1997; for a historical summary, see Tabuce et al., 2009).</footnote>

<footnote n="2">² Anthropoid status (Godinot and Mahboubi, 1992, 1994; Godinot, 1994; Beard, 2002; Seiffert et al., 2005a, 2010).</footnote>

<footnote n="3">³ Strepsirrhine/adapiform *versus* anthropoid status (Hartenberger and Marandat, 1992; Godinot, 1994; Godinot in Hartenberger et al., 1998) or cercamoniine lying very ‘near the prosimian-anthropoidean transition’ (Simons and Rasmussen, 1994).</footnote>

<footnote n="4">⁴ Godinot (2006, pp. 454) introduced the terms of ‘pre-tooth-combed lemuriforms, or stem lemuriforms preceding tooth comb acquisition’ to describe the taxonomic status of the Djebelemurinae. Tabuce and Marivaux in Tabuce et al. (2009), then Marivaux et al. (2013) extended this concept by associating the Azibiidae with the Djebelemuridae, and introducing the terms ‘advanced stem strepsirrhines or pre-tooth-combed primates’.</footnote>
known from the Eocene of any continent' (Seiffert, 2012, pp. 243; see also Godinot, 2015). Last, *Namadapis* and *Notnamaia* from Namibia are interpreted as strepsirrhine adapiforms (Adapidae, Caenopithecinae; Godinot et al., 2018; Godinot, 2022). Another mammal taxon from Chambi in Tunisia, documented only by two isolated teeth (lower molars), could testify to the presence of a primate relatively larger in this region of northern Africa at that time. In the original description of this fossil dental material, Court (1993) emphasized the possible affinities of this taxon with certain advanced, more recent adapiforms (Asian sivaladapids), but also with non-primate hyopsodontid 'condylarths'. Due to the lack of comparative paleontological material from this geological epoch in Africa in the early 1990's, the status of this taxon from Chambi remained as an 'enigmatic mammal' at the time of its description (Court, 1993). Subsequent discoveries and recognition of highly specialized caenopithecine adapids in the late Eocene of the Fayum in Egypt (e.g., Simons et al., 1995; Simons and Miller, 1997; Godinot, 1998; Seiffert et al., 2009; Seiffert et al., 2018), as well as in the middle Eocene of Namibia (Godinot et al., 2018; Godinot, 2022), led to the view that this group of medium-sized to large adapiform primates must have undergone a significant diversification during the middle Eocene in Africa; a view that revived and strengthened the possible adapiform affinities of the 'enigmatic mammal' from Chambi (e.g., Seiffert, 2012; Godinot et al., 2018; Seiffert et al., 2018). One observation today, based on our current knowledge of the Afro-Arabian fossil record, is that no representative of the Anthropoidea clade is known from this landmass at the beginning of the Paleogene (except if we consider the possible anthropoid status of *Altiatlasius*; for a summary see e.g., Beard, 2006; Seiffert, 2012). Anthropoids only make their first appearance in the African fossil record later, at least at the end of the middle Eocene epoch (Tunisia, *Amamria*; Marivaux et al., 2014), and their record is noticeably abundant in deposits dating from the late Eocene, primarily in North Africa (for a summary, see Seiffert, 2012; Marivaux et al., 2024, fig. 8).

Early known djebelemurids (i.e., *Djebelemur*) were hitherto documented only in Tunisia, from deposits of Djebel Chambi dating from the late early to early middle Eocene. However, the group existed over several million years, as attested by the presence of some of its representatives in North Africa and Arabia during the late Eocene (Fayum, Egypt; Simons, 1997; Seiffert et al., 2005b; Seiffert, 2012) and the early Oligocene (Sultana of Oman and Atlantic Sahara/Dakhla; Gheerbrant et al., 1993; Godinot, 2006, 2010; Seiffert, 2012; Marivaux et al., 2024). In contrast, azibiids (i.e., *Azibius* and *Algeripithecus*) have so far only been recorded in deposits dating from the late early to early middle Eocene, primarily from the Gour Lazib Complex in western Algeria, and presumably also from Tunisia. Indeed, two isolated upper molars ($M^2$ and $M^3$) from Chambi, originally assigned to *Djebelemur martinezi* (Hartenberger and Marandat, 1992, fig. 3d-e), have long been judged to be too bunodont (e.g., Godinot, 1994, 2006, 2010; Seiffert et al., 2010) to correspond to the dental pattern condition of the holotype of this species (a hemi-mandible bearing $P_3-M_3$ and alveoli for $P_2$ and canine; Hartenberger and Marandat, 1992, fig. 3a-c). This possible mismatch was confirmed by the subsequent discovery at Chambi of an almost complete and morphologically distinct upper toothrow, formally attributed to *Djebelemur martinezi* (Marivaux et al., 2013,
fig. 4). The two upper molars from Chambi, formerly attributed to *Djebelemur*, would indeed testify to the presence of a diminutive azibiid taxon (cf. *Algeripithecus*; e.g., Godinot, 2006; Tabuce et al., 2009; Seiffert et al., 2010; Seiffert, 2012; Marivaux et al., 2013). The existence of two distinct tiny strepsirrhines at Chambi was also advocated by the discovery of isolated petrosal bones of comparable size and of unequivocal strepsirrhine primate affinities, but that display subtle morphological dissimilarities in the bony labyrinth structure, possibly pointing to an alpha taxonomic distinctiveness (Benoit et al., 2013).

Continuing processing of the highly indurated sediments of Chambi (locus 1, named CBI-1; Fig. 1) has recently yielded additional primate dental remains, helping to formalize the presence of a diminutive azibiid species, described herein as a new species of the genus *Algeripithecus*. Likewise, the continued processing of the indurated sediments of Glib Zegdou in the Gour Lazib Complex (layer HGL50; Fig. 1) has led to the discovery of further primate dental remains, otherwise attesting to the presence of a larger species of the genus *Azibius*. The earlier discovery in the Glib Zegdou HGL50 fossil-bearing locality of a medium-sized primate talus, harboring strepsirrhine affinities, already foreshadowed this larger form of Azibiidae (Marivaux et al., 2011a). Processing of the Glib Zegdou sediments also revealed the presence of a tiny primate, documented by half a dozen isolated teeth. Despite the limited number of fossils recovered, the simple and unique morphology of these teeth allows us to describe a new taxon, a possible basal representative of the Djebelemuridae.

Here, we illustrate and describe this set of new fossil dental specimens, which expand our knowledge of the diversity of primates from these two North African fossil-bearing localities. We take the opportunity of this publication to refigure the best-preserved dental material of *Algeripithecus minutus*, *Azibius trerki* and *Djebelemur martinezi*, as well as the two isolated lower molars of the so-called 'enigmatic mammal' from Chambi, with renderings of surface reconstruction from three-dimensional digital models. New dental specimens from Glib Zegdou (HGL50), in particular possible deciduous premolars of *Algeripithecus minutus* and *Azibius trerki*, are also presented and described here. All these new fossils, as well as others previously described and revisited here, are discussed with a special emphasis on the macroevolutionary, paleobiological and paleobiogeographical implications for the early evolutionary history of primates in Africa.

## 2. Materials and methods

### 2.1. Fossil recovery and extraction

For the two Eocene fossil-bearing localities (Chambi CBI-1 and Glib Zegdou HGL50), we extracted several hundred kilograms of sediments (lacustrine limestone and fluvio-lacustrine limestone to calcareous sandstone, respectively; Fig. 1C, F), preferably using hammers and chisels, and occasionally a jackhammer for the most indurated levels (especially in Chambi).
The fossil material presented in this paper was obtained after several rounds of acid etching (10 % acetic acid) and screen-washings of the indurated calcareous matrices (Fig. 1C-D, F-G). This specific sediment processing was made possible thanks to the dedicated facilities of the paleontology lab at Montpellier (France). These repetitive operations have led to the recovery of several dental, cranial and postcranial fossil remains of aquatic and terrestrial vertebrates including fishes, turtles, crocodiles, squamates, amphibians (Rage et al., 2021; Georgalis et al., 2024), birds (Mourer-Chauviré et al., 2011, 2013, 2016; Garcia et al., 2020) and mammals such as marsupials, rodents, primates, bats, eulipotyphlans, hyaenodonts, elephant shrews, and hyracoids (for a summary, see Sudre, 1979; Hartenberger et al., 1997, 2001; Adaci, 2012; Adaci et al., 2016; Marivaux et al., 2015; Ravel et al., 2015, 2016) (SOM Table S1). The new fossil specimens (mainly dental) of primates described here were recently extracted from the last remaining sediment blocks, collected during previous field campaigns in Algeria (Gour Lazib Complex, 2004-2011) and Tunisia (Djebel Chambi, 2008-2012).

## 2.2. Fossil repository

The fossils from Djebel Chambi (Tunisia), referenced (CBI-1-xx), described and figured in this paper are housed in the paleontological collections of the museum of the *Office National des Mines* (ONM) of Tunis, Tunisia. The fossils from Glib Zegdou (Gour Lazib Complex, Hammada du Dra, Algeria), referenced (HGL50-xx), described and figured in this paper are housed at the *Institut des Sciences de l'Évolution de Montpellier* (ISE-M) in the paleontological collections of the *Université de Montpellier* (UM), France. The fieldwork that produced the fossils studied here was carried out as part of joint and collaborative paleontological programs (ISE-M - ONM and ISE-M - Universities of Tlemcen, Oran and Jijel) in the Lower Cenozoic of North Africa.

## 2.3. Nomenclature and measurements

The terminology for the primate dentition (SOM Fig. S1) follows Marivaux et al. (2023, 2024), modified after Kay (1977), Szalay and Delson (1979), and Marivaux (2006). Teeth were measured (maximum buccolingual width [BLW] and maximum mesiodistal length [MDL]) using either a stereomicroscope (Leica M205 C) connected to a digital camera (Leica DFC420 C) with the LAS V4.13 measurement tools (Table 1), or a measuroscope (Nikon 10) coupled with a digital counter (CM-6S) (SOM Table S2).
## 2.4. High-resolution µCT scan

In this work, we used X-ray micro-computed tomography (µCT) to obtain three-dimensional (3D) digital models of the dental specimens. Each fossil specimen was scanned with a resolution of 5.9 µm using the µCT-scanning station EasyTom 150 / Rx Solutions of the Montpellier RIO Imaging facility (ISE-M, Montpellier, France). The crown and roots of each fossil tooth were virtually delimited by manual segmentation under AVIZO 2020.2 (Visualization Sciences Group). For this, teeth were prepared within a 'Label Field' module of AVIZO, using the segmentation threshold selection tool. When certain fossil specimens were unavailable, and only epoxy casts were available, we scanned these copies using the same scanning equipment with similar resolution as the fossils, but at lower energy. The views of the specimens (fossils and epoxy casts) presented in this paper (Figs 2–8 and SOM Figs S2–S5) are surface reconstructions based on 3D digital models. The 3D digital models of the tooth surface of the different azibiid and djebelemurid primates described and/or discussed in this paper are available at MorphoMuseuM (Marivaux et al., 2025), an online open access platform that aims to enhance accessibility to 3D models (https://morphomuseum.com).

## 2.5. Body mass estimation

For all taxa from Glib Zegdou (layers HGL50 & HGL51) and Chambi (CBI-1), estimates of adult body masses (BM) were predicted using the 'prosimian' regression equations provided by Egi et al. (2004: table 2), based on molar and premolar areas (maximum MDL times maximum BLW; Table 1 and SOM Table S2). A correction for logarithmic transformation bias, known as the ratio estimator (RE; Smith, 1993), was applied to each adult BM estimate as the predicted BM times the RE (see Egi et al., 2004: table 2). In order to compare and discuss the body sizes of the different taxa presented in this article, averages of the BM estimates were calculated from the different loci of upper and lower molars only, using the best-preserved specimens.

# 3. Results

## 3.1. Systematic paleontology

- Class Mammalia Linnaeus, 1758

- Order Primates Linnaeus, 1758

- Suborder Strepsirrhini Geoffroy Saint-Hilaire, 1812
*Included genera* *Azibius* Sudre, 1975; *Algeripithecus* Godinot and Mahboubi, 1992.

**Emended diagnosis** Azibiids differ from all other primates in having high, mesiodistally aligned trigonid cuspids of P₃-₄ (resulting from a significant distobuccal displacement of the metaconid and a mesiobuccally positioned paraconid), forming a high-crowned and serrated blade-like structure; P₃-₄ also present a slight exodaenodonty and a degree of tooth overlapping associated with a mesial crown elevation and an inclination of the lingual cingulid. Lower molars are characterized by a pronounced rising and sharpening of the trigonid from M₃ to M₁; M₁-₂ have a distobuccally offset metaconid (much more pronounced on M₁), display a tiny paraconid mesial to the protoconid, have no hypoconulid, and exhibit a narrow, limited in surface and sub-circular talonid basin, which is open lingually by a deep notch in front of the entoconid; M₂-₃ display a narrow trigonid, closed lingually by the presence of a premetacristid, which is lacking on M₁, leaving the trigonid open lingually on this tooth. P³⁻⁴ have a peak-shaped lateral profile resulting from the buccally inclined protocone and the very high and vertical sharp edge aspect of the ectoloph. The bunodont M¹⁻² have gently sloping buccal and lingual margins (particularly on M², with a notable buccal expansion of the paracone), display a large hypocone and a thick lingual cingulum that is often incomplete (i.e., interrupted), exhibit a buccolingually straight to convex distal crown margin (not invaginated), show a variable development of the metaconule on a well-defined but low metacrista complex, and are virtually, if not entirely devoid of hypoparacrista, hypometacrista and postprotocrista.

Genus *Algeripithecus* Godinot and Mahboubi, 1992

*Type species* *Algeripithecus minutus* Godinot and Mahboubi, 1992.

*Referred species* *Algeripithecus minimissimus* sp. nov.

*Geographic and stratigraphic ranges* North Africa (western Algeria to Tunisia), late early to early middle Eocene.

**Emended generic diagnosis** Genus comprising smaller species than those of the genus *Azibius*. Differs from *Azibius* in having a stronger development of the metaconid on P₃-₄, especially on P₃, which gives this tooth a blade-like morphology with a more serrated appearance; M₃ with shorter trigonid and talonid (smaller tooth), as well as a smaller, narrower hypoconulid lobe; M₂ having a paracristid with a strong obliquity and showing a distinct configuration of the cristid obliqua, which connects to the distobuccal aspect of the metaconid (as on M₁) instead of to the middle of the distal trigonid wall. Upper teeth also differ from those of *Azibius*, particularly P⁴, which displays a more clearly defined parastyle, distinctly separated from the paracone, a poorly developed metacone, an almost non-existent or even absent paraconule,
the presence of a thin endoprotocrista, and the absence of a postprotocrista; M¹⁻² characterized by the variable presence of a tiny but well-defined metaconule, a more pronounced and sub-complete lingual cingulum, and by distal crown margins that are more rectilinear buccolingually than convex.

*Algeripithecus minimissimus* sp. nov.

**Etymology** Epithet from the Latin *minimus* (very small) with the superlative suffix *-issimus*, in reference to the status of this species as the smallest known.

**Holotype** ONM-CBI-1-1205, fragment of right mandible preserving M₁⁻₃ and the distal root of P₄ on the dentary bone (Fig. 2A-D).

**Hypodigm** In addition to the holotype, ONM-CBI-1-38, right P³ (Fig. 3D-F); ONM-CBI-1-37, right P⁴ (Fig. 3A-C); ONM-CBI-1-36, left M² (Fig. 3G-I; figured in Hartenberger and Marandat, 1992, fig. 3e [under the original accession number CBI 36]); ONM-CBI-1-35, left M³ (Fig. 3J-L; figured in Hartenberger and Marandat, 1992, fig. 3d [under the original accession number CBI 35]); ONM-CBI-1-1206, right P₄ (Fig. 3M); ONM-CBI-1-1207, right P₄ (Fig. 3N-P); ONM-CBI-1-1208, right M₂ (damaged buccally; Fig. 3Q); ONM-CBI-1-1209, left M₂ (Fig. 3R-T). Dental measurements are reported in Table 1.

**Type locality** Chambi locus 1 (CBI-1), Djebel Chambi, central-western Tunisia (Fig. 1).

**Age** Late early to early middle Eocene (Hartenberger et al., 1985, 1997, 2001; Marivaux et al., 2015; Ravel et al., 2015, 2016).

**Diagnosis** Diminutive species, less than half the size of *Algeripithecus minutus*. Differs from *Al. minutus* in having lower molars without buccal cingulid; M₁ with a talonid basin particularly short and narrow, compared with the more expanded talonid of M₂ and M₃; lower teeth with lesser crown overlap; upper molars, notably M² and M³, with a metacone less lingually offset from the mesiodistal axis containing the paracone; upper premolars, especially P⁴ and P³, with a more rounded/oval crown outline (instead of being triangular with a buccolingual long axis); P⁴ bearing a conspicuous metastyle (faintly developed to absent on P⁴ of *Al. minutus*), a less prominent parastyle (strongly developed, high on P⁴ of *Al. minutus*), and a dominating conical paracone, more centrally positioned on the buccal crown margin (rather than markedly displaced distally as is the case on P⁴ of *Al. minutus*), flanked at mid-slope of its mesial and distal edges by the parastyle and metastyle, respectively, both of identical size; P³ bearing a small but much better-defined protocone (remaining well inferior to the paracone), and as on P⁴, a better differentiated hypocone on the distal part of the lingual cingulum.

**Nomenclatural remark** This new species must be referred to as *Algeripithecus minimissimus* Marivaux, 2025, following the article 50.1 and the 'recommendation 50A concerning multiple authors' of the International Code of Zoological Nomenclature (ICZN, 1999).
## Description and comparisons

**Lower dentition** The holotype (ONM-CBI-1-1205; Fig. 2A-C) is a damaged fragmentary right mandible bearing M₁ to M₃, and the distal root of P₄. Mesially, the dentary bone is broken clean (vertical fracture) at the level of the mesial alveolus of P₄, and distally, it retains only a small part of the base of the ramus and a short part of the mesial region of the angular process. In the lingual aspect of the dentary, the latter two branches are separated by a deep, horizontal fossa, the mesial region of which houses the mandibular foramen, lying almost directly beneath the distal end of the posterior root of M₃ (Fig. 2C). The mandibular corpus holding the roots of the teeth is robust (bulging mediolaterally) but shallow ventrally, having its maximum depth under M₂ (~ 2.5 mm), and tapering forwards from M₁ (Fig. 2B-C). The tooth roots occupy almost the entire depth of the mandibular corpus (Fig. 2B-D), as is the case on the UM-HGL50-397 hemi-mandible of *Algeripithecus minutus* (SOM Fig. S2A-D). The mandibular canal has an oval cross-section (mediolateral long axis, visible through the break that provides a frontal section; Fig. 2D), is located in the lowest part of the mandibular corpus, between the root apex and the ventral thin cortical bone. Although the dentary bone is broken along the mesial alveolus of P₄, a very slight medial inflection of the mandibular corpus suggests a slight lingual flaring (Fig. 2A), probably testifying to the onset of the mandibular symphysis, as is also observed on the hemi-mandible of *Al. minutus* (Fig. 4A; see also SOM Fig. S2). The preserved teeth on the dentary are corroded, buccally worn, and fractured (especially M₁). The crown of P₄ is missing on the dentary, and only the distal root is preserved, whose section is compressed mesiodistally (buccolingual long axis) with a central constriction (Fig. 2A), making the section '8'-shaped, which could testify to the fusion of two distal roots. The mesial alveolus of P₄ is partly preserved, showing that the mesial and distal roots of this premolar were aligned mesiodistally.

The crown morphology of P₄ is documented by two isolated specimens (Fig. 3M-N), particularly well-preserved and of similar morphology (ONM-CBI-1-1206 and -1207, the crown surface of the former being somewhat smoother due to a slight corrosion; Fig. 3M). As in *Algeripithecus minutus* (Fig. 4A; SOM Fig. S2), this new species has large, high-crowned P₄s, similar in length to the first molar, but oval (mesiodistal long axis) rather than rectangular in outline, and bordered at cervix by a cingulid around the entire tooth periphery. On both specimens, the crown displays two main cuspids in a central position, and two secondary, much smaller mesial and distal cuspids (Fig. 3M-N). The two main cuspids consist of a massive, dominant protoconid and a strong, slightly smaller metaconid (Fig. 3M-N, P). These two cuspids are close to each other and almost twinned. The metaconid is greatly displaced buccally so that these two main cuspids are aligned on a mesiodistal axis. The mesial secondary cuspid (likely a small paraconid occupying a very buccal position) is aligned on the protoconid-metaconid axis, while the distal secondary cuspid (possibly a small hypoconid or entoconid) is lingually offset from the alignment of the other three cuspids (Fig. 3M-N, O). The mesialmost small cuspid is virtually incorporated into the anterior flank of the protoconid,
while the distalmost small cuspid is isolated on the distolingual margin of the crown, lying on
the distal cingulid (Fig. 3O). The protoconid and metaconid both display pre- and post-
cristids, which are aligned mesiodistally. In lateral view (Fig. 3P), this alignment of cuspids and
cristids gives these high-crowned P4s a serrated blade-like morphology, an unusual pattern
that is otherwise identical to that characterizing the P4s of *Algeripithecus minutus* (Fig. 4A;
SOM Fig. S2), but also of *Azibius trerki* (Fig. 4E; SOM Fig. S5B-C). In frontal and distal
perspectives (Fig. 3O), the crown outline of these P4s is triangular, due to the conical
appearance of the cuspids (swollen bases and acute apices) and their alignment.
Furthermore, still in frontal or distal view, the width of the root(s) is less than the width of the
crown, and the enamel of the buccal aspect of the teeth slightly protrudes beyond the
inferior margin of the lingual aspect of the teeth, thereby exhibiting a slight buccal
exodaenodont pattern. P4 exodaenodonty is also characteristic of *Al. minutus* and *Az. trerki*.

The morphology of M₁ and M₃ is documented only by the damaged teeth preserved on
the holotype ONM-CBI-1-1205 mandible (Fig. 2A-C), while for M₂, better-preserved, pristine
specimens were found separated/isolated (Fig. 3Q-R), enabling us to appreciate the
morphology of this dental locus more accurately than from the damaged tooth preserved on
the mandible. As in *Al. minutus* (Fig. 4A; SOM Fig. S2), the lower molars are bunodont,
moderately high-crowned, showing a decrease in crown height from M₁ to M₃ (Fig. 2B-C),
and an increase in front-to-back tooth length. In occlusal view, the crown is much narrower at
the top of the occlusal surface (acute, salient apices of the main cuspids) than at its base,
which is flared (inflated base of the main cuspids). There is a pronounced rising and
sharpening of the trigonid from M₃ to M₁. The protoconid, which occupies a standard buccal
position on M₃ (i.e., mesial to the hypoconid and mesiobuccal to the metaconid) becomes
increasingly mesial and central from M₂ to M₁, while the metaconid gradually moves buccally
from M₂ to M₁, being almost fully distal to the protoconid on M₁. In other words, the
protoconid and metaconid become increasingly massive and progressively aligned
mesiodistally from M₃ to M₁, a configuration which is consistent with the adjacent cuspid
alignment that characterizes the serrated blade-like pattern of the high-crowned P₄. Such a
transformation of the trigonid configuration from M₃ to M₁ (and P₄) is also observed in *Al.
minutus*, where the serrated blade-like cuspid alignment pattern also applies to P₃ (Fig. 4A;
SOM Fig. S2A-D). This unusual pattern of the lower dentition is also characteristic of *Az.
trerki* (Fig. 4E; SOM Fig. S5B-C), with the subtle difference that the transformations of the trigonid
configuration from M₃ to M₁, although present, are somewhat less pronounced than in
species of *Algeripithecus*.

On the ONM-CBI-1-1205 mandible, M₁ displays a very short and narrow talonid basin
compared with the more extensive talonid basin of M₂ and M₃ (Fig. 2A), a talonid reduction
that is present but less marked on the M₁ of *Al. minutus* (Fig. 4A; SOM Fig. S2A-B). The
numerous cracks on the crown surface of that M₁ prevent a precise reading of its occlusal
morphology. However, it is noticeable that on the trigonid of this first molar, the protoconid
seems to be the largest cuspid of the crown. It is mesio-centrally positioned and nearly
twinned with a slightly smaller metaconid (presence of a short protocristid), which is strongly
displaced distobuccally. The protoconid displays a long, high, mesiobuccally oriented
preprotocristid, instead of being mesiolingually oriented as on M₁ of *Al. minutus* (Fig. 4A; SOM
Fig. S2A-B). Also, the mediolingual paracristid and premetacristid are both absent (as on M₁
of *Al. minutus*; Fig. 4A; SOM Fig. S2A-B), leaving consequently the trigonid wide open
lingually. This lingual configuration of the trigonid is also characteristic of M₁s of *Az. trerki* (Fig.
4E; SOM Fig. S4K) and *Az. magnus* sp. nov. (Figs 4G and 5U). In contrast, M₂ and M₃ preserved
on the ONM-CBI-1-1205 mandible display low but well-defined paracristid and
premetacristid, which close together the trigonid basin lingually (Figs 2A and 3R), as is the
case on M₂-₃ of *Al. minutus* (Fig. 4A; SOM Fig. S2A-B) and *Az. trerki* (Fig. 4E; SOM Fig. S5B). On
the two isolated pristine M₂s (ONM-CBI-1-1208 and -1209; Fig. 3Q-R), the short
preprotocristid bears in its mesial end a minute but well-defined cuspid-like enamel swelling.
The latter occupies a mesial, slightly lingual position to the protoconid, and corresponds to a
buccally displaced paraconid. Lower molars (especially M₁-₂) of *Al. minutus*, as well as *Az.
trerki* and *Az. magnus* nov. sp. (Fig. 4), display a similar small paraconid, buccally displaced,
and virtually mesial to the protoconid. This buccal position of the paraconid on molars is
consistent with that observed on the premolars, characterizing the anterior mesiodistal
alignment of the cuspids. On M₂ and M₃, a low, cingulid-like paracristid links the paraconid to
the mesial end of the short, gently sloping premetacristid (Figs 2A and 3R). Given the mesial
position of the protoconid and paraconid with respect to the metaconid/premetacristid, the
paracristid is oblique, directed backwards (i.e., on a mesiobuccal-distolingual axis), strongly so
on M₂ (Figs 2A and 3R) and much less so on M₃ (Fig. 2A). The strong obliquity of the
paracristid on M₂ is also a characteristic of *Al. minutus* (Fig. 4A; SOM Fig. S2A-B), a dental trait
which is not observed on M₂ of *Az. trerki* (Fig. 4E; SOM Fig. S5B).

The buccal flanks of the molars (M₁-3) preserved on the ONM-CBI-1-1205 mandible are
corroded (Fig. 2A-B), which prevents us from observing the presence of a mesiobuccal
cingulid, as is the case for the lower molars of *Al. minutus* (Fig. 4A; SOM Fig. S2A-C). However,
from the two isolated, virtually pristine M₂s of the hypodigm (ONM-CBI-1-1208 and -1209), it
is clear that there is no strong mesiobuccal cingulid, but instead some enamel bulging at the
base of the crown (Fig. 3Q-R, T). The buccal cingulid is barely visible and limited to the
hypoflexid area on lower molars of *Az. trerki* (Fig. 4E; SOM Fig. S5B-C), whereas in *Az. magnus*
sp. nov., it is particularly conspicuous and extends along the entire length of the teeth (Fig.
4G). On the M₂ of the ONM-CBI-1-1205 mandible and on the two isolated M₂s associated, the
cristid obliqua is slightly curved, running from the hypoconid partly up the distal wall of the
trigonid (i.e., short protocristid connecting the protoconid to the metaconid), to reach the
distobuccal aspect of the metaconid (Figs 2A-B and 3Q-R, T). The M₁ preserved on the
mandible is damaged, preventing an accurate assessment of the cristid obliqua configuration.
Nevertheless, this cristid appears very short, extending up the distal wall of the trigonid, and
seems to connect to the metaconid, as on M₂. The hypoflexid on both loci (M₁-2) is shallow
and only slightly extended transversely due to the large, swollen, expanded buccal flank of the
protoconid (Figs 2A-B and 3Q-R, T). In contrast, on M₃, the cristid obliqua is more buccal and
oriented mesiodistally, running from the hypoconid to reach the distal wall of the trigonid at a
point distal to the protoconid, thereby limiting the lingual expansion of the hypoflexid (Fig.
2A-B). These configurations of the buccal margin structures of M<sub>1-2</sub> and M<sub>3</sub> are very similar to
those of the respective lower molars in *Al. minutus*. Although the configuration of the cristid
obliqua of M<sub>1</sub> is similar between *Algeripithecus* and *Azibius*, the configuration of this cristid on
M<sub>2</sub> is distinct between these genera. On the M<sub>2</sub> of *Az. trerki*, the cristid obliqua ends partly up
the distal wall of the trigonid, but does not reach the distobuccal aspect of the metaconid;
instead, it reaches the trigonid wall at a point distolingual to the protoconid (i.e., on the
protocristid; Fig. 4E; SOM Fig. S5B-C).

As in *Al. minutus*, *Az. trerki* and *Az. magnus* sp. nov., the lower molars of the new species
from Chambi have well-defined talonid main cuspids with salient apices, much higher than
the talonid cristids (Figs 2A-C and 3Q-T). On M₁ and M₂, the entoconid is slightly more
distally positioned than the hypoconid (on a buccolingual axis), and clearly offset lingually
from the metaconid (on a mesiodistal axis). This apparent lingual displacement of the
entoconid is actually linked to the buccal displacement of the metaconid, a topology which is
characteristic of M₁-₂ of Azibiidae (Fig. 4). The pre-entocristid and postmetacristid are very
weakly developed, short, steep-sided, and meet only at their base, leaving the talonid basin
virtually open lingually. In lingual view, this lingual talonid opening has the appearance of a
deep notch, either V-shaped or U-shaped (depending on the specimen; Fig. 2B-C and 3S-T).
This configuration of the lingual talonid margin somewhat contrasts with that observed on
lower molars of *Al. minutus*, where the postmetacristid and pre-entocristid are more
developed, high and sharp, closing the talonid basin lingually (SOM Fig. S2). This lingual
closure of the talonid basin is not developed on M₁-₂ of *Az. trerki* (Fig. 4E; SOM Figs S4K-M
and S5B-C), whereas in *Az. magnus* sp. nov., the basin is almost entirely walled lingually (Fig.
4G), leaving only a wide V-shaped notch in lingual view (Fig. 5P), with the postmetacristid and
pre-entocristid very close together, but not fused. On the ONM-CBI-1-1208 and -1209 M₂s
and the M₂ of the holotype ONM-CBI-1-1205 mandible, the hypoconid and entoconid are
linked by a continuous, arched and un-notched postcristid, formed by long hypocristid and
postentocristid, respectively. There is no clear evidence of a hypoconulid at the junction of
the hypocristid and postentocristid on the midline of the crown. Only a trace of distal cingulid
(enamel bulging) can be noted, running up the distal flank of the crown to the hypocristid-
postentocristid junction, generating a very slight bulge in the most lingual part of the
hypocristid. A tiny hypoconulid-like bulge is particularly visible on the M₂ preserved on the
ONM-CBI-1-1205 mandible (Fig. 2A-C), but a crack located just at this point makes it
impossible to assess whether this is a true hypoconulid. The presence of a hypoconulid on the
lower molars (M₁-₂) of Azibiidae is not obvious, and the enamel swelling often observable in
the middle of the postcristid (or just slightly buccal to midline), is the result of the junction of
the hypocristid-postentocristid with a weak distal cingulid that runs up the distal flank of the
crown (Fig. 4). Such a hypoconulid-like bulge is particularly marked in *Az. magnus* sp. nov.,
where lower molars display a strong distal cingulid running up the distal flank of the crown
and joining the hypocristid-postentocristid junction, thereby generating an enamel swelling (Fig. 4G).

Finally, the M₃ preserved on the ONM-CBI-1-1205 mandible, although damaged and corroded, especially its buccal aspect (Fig. 2A-B), has similar shape and proportion as the M₃ of *Al. minutus* (Fig. 4A), characterized by a short (mesiodistally pinched), lingually closed trigonid, and a large talonid bearing a strong hypoconulid, which extends distally beyond the remainder of the talonid, forming a lobe. On this tooth, the protocristid connecting the protoconid to the metaconid appears longer than on M₁ and M₂, due to the position of the metaconid, which is not buccally displaced (as is the case on M₁ and M₂), and thus more distant from the protoconid. Because of the damage, we cannot assess whether the talonid is narrower than the trigonid, as is the case on the M₃s of *Al. minutus* and *Az. trerki*. The hypoconulid lobe is narrower than the talonid breadth, a trait that characterizes M₃s of *Algeripithecus*, whereas in *Azibius*, the hypoconulid lobe is more buccolingually extensive, almost as wide as the width of the talonid (Fig. 4E). On the M₃ of ONM-CBI-1-1205, the entoconid is well defined, positioned transversely to the hypoconid and distal to the metaconid, and isolated from other cuspids (absence of pre-entoconid and postentoconid cristids). As such, it appears cuspidate rather than crestiform, the latter condition being present on M₃s of *Al. minutus* (Fig. 4A) and *Az. trerki* (Fig. 4E). Due to the absence of pre-entocristid and the weak development of the postmetacristid, the talonid basin remains open lingually while it is closed in *Al. minutus* and *Az. trerki* (as a result of the development and fusion of the buccal cristids aforementioned). Over the entire length that the postentocristid would normally occupy, a small, well-defined accessory cuspulid (i.e., *tuberculum sextum*) is developed between the entoconid and the hypoconulid, a trait which is barely visible in *Al. minutus*, and more pronounced in *Az. trerki* (Fig. 4).

**Upper dentition** Only two premolars (P³ and P⁴) and two molars (M² and M³) were extracted from the indurated sediment of Chambi. The two molars were described in the early 1990s and included in the hypodigm of *Djebelemur martinezi* by Hartenberger and Marandat (1992). However, their generic assignment has often been questioned (e.g., Godinot, 1994, 2006, 2010; Seiffert et al., 2010), due to their marked bunodonty compared to the more crested, less bunodont pattern of the teeth preserved on the holotype of this genus (a mandible bearing P₃–M₃). The subsequent discovery at Chambi of an almost complete upper toothrow, morphologically distinct and much more compatible with the holotype of *Djebelemur* (Marivaux et al., 2013), confirmed the suspected original mismatch and thus the formal presence of two different primate species at Chambi, including an azibiid represented by these two upper molars. Here, we re-describe these two upper molars with more specific comparisons, and add the description of two previously unpublished premolars.

The two upper premolars are very similar in occlusal morphology. ONM-CBI-1-38 (Fig. 3D-F) differs from ONM-CBI-1-37 (Fig. 3A-C) in being slightly smaller and in having slightly less pronounced cusps, styles and crests. We tentatively interpret ONM-CBI-1-37 as a P⁴, inasmuch as this tooth is larger, with a more transversely extended crown outline, and
because it displays stronger styles. These two teeth have a rounded/oval crown outline, quite distinct from the more triangular outline with a buccolingual long axis of the P⁴s and P³s of *Al. minutus* (Fig. 4B; SOM Fig. S3F, K). The ONM-CBI-1-38 P³ displays a minute but much better-defined protocone than the condition observed on P³ of *Al. minutus* (and *Az. trerki*), as well as a better differentiated hypocone on the distal part of the lingual cingulum. These upper premolars are particular in their 'peak'-like aspect in distal view (Fig. 3C, F). The teeth are dominated by a strong conical paracone, positioned at the center of the buccal margin, and clearly much taller than the small protocone located in an opposite lingual position (Fig. 3B, E). This paracone appears as a dagger-like cusp, being extended mesiodistally and flanked mid-slope of its mesial and distal margins by a parastyle and a metastyle, respectively. On both premolars, these two buccal styles are practically the same size, but they are clearly more prominent on ONM-CBI-1-37 (Fig. 3B) than on ONM-CBI-1-38 (Fig. 3E). If the tooth we refer to as P⁴ (ONM-CBI-1-37) really corresponds to this dental locus, then it presents a quite distinct dental pattern from the P⁴s attributed to *Al. minutus* (Fig. 4B; SOM Fig. S3K-O). This distinction is particularly noticeable in the arrangement and development of the buccal tubercles. The dental pattern of the ONM-CBI-1-37 P⁴ is actually quite expected (standard) for an upper fourth premolar; rather it is the P⁴s of *Al. minutus* that show unusual transformations. The ONM-CBI-1-37 P⁴ displays a conspicuous metastyle, which is weakly developed or absent on P⁴s of *Al. minutus*, and a much less prominent parastyle, which is surprisingly strongly developed and very high on P⁴s of *Al. minutus* (Fig. 4B; SOM Fig. S3L-M). The dominating conical paracone is centrally positioned on the buccal crown margin of the ONM-CBI-1-37 P⁴ (Fig. 3A-B), whereas it is markedly displaced distally on P⁴s of *Al. minutus* (Fig. 4B; SOM Fig. S3K-M). All these anatomical differences underline the uniqueness of the P⁴s of *Al. minutus* compared with ONM-CBI-1-37, and even the P⁴s of *Az. trerki* (Fig. 4F; SOM Fig. S4F-J). The P⁴s of *Az. trerki* are somewhat 'molariform', being relatively large compared to the first upper molars, and characterized by a strongly developed, high metacone (or a very large metastyle?), but which remains slightly smaller than the dominant conical paracone. In *Az. trerki*, the parastyle of P⁴s is well defined, mesial to the strong paracone (incorporated mid-slope of its mesial flank), and well inferior to the latter (SOM Fig. S4G-H), a condition resembling the parastyle configuration on ONM-CBI-1-37 P⁴, and contrasting with the very strong, cusp-like parastyle of the P⁴s of *Al. minutus* (SOM Fig. S3L-M). Although the base of the buccal margin of the ONM-CBI-1-37 and -38 premolars is missing (broken), the small mesial portion preserved indicates that a buccal cingulum was present (Fig. 3A, D). It probably extended along the entire length of the teeth, as is the case on the molars (Fig. 3G, J). The presence of a buccal cingulum is also characteristic of premolars and molars of *Al. minutus* (Fig. 4B; SOM Fig. S3F-D'), whereas this feature is much less frequent, or even more weakly developed to absent on the upper premolars and molars of *Az. trerki*. ONM-CBI-1-37 and -38 both display a long, straight, oblique mesial cingulum that spans the entire width of the teeth, and that is continuous with the buccal cingulum. A tiny enamel bulge in its center indicates the presence of a possible paraconule, in which case the buccal branch of the cingulum joining the buccal cingulum would be a preparaconule crista. The development and size of a
paraconule are variable in the upper premolars of *Al. minutus* and *Az. trerki*. In *Al. minutus*, the paraconule is either tiny or absent on P⁴s, and absent on P³s. In *Az. trerki*, the paraconule is always present on P⁴s and very weak to absent on P³s. In the latter taxon, the mesial cingulum is very weakly developed to absent, and when present, it is very short, barely visible. The paraconule is not carried by the mesial cingulum, but connected to the buccal end of the preprotocrista, a crest that is absent on P⁴s of *Al. minutus* and on ONM-CBI-1-37. Mesiolingually, the mesial cingulum on ONM-CBI-1-37 and -38 wraps around the small protocone and continues distolingually via a lingual cingulum. The latter is variably developed on P⁴s of *Al. minutus*, being either absent or present, and in the latter case complete (Fig. 4B) or interrupted directly lingual to the protocone (SOM Fig. S3K-L). In *Az. trerki*, the lingual cingulum is always absent on both P⁴s and P³s (Fig. 4F; SOM Fig. S4F-G). On this taxon, the lingual, as well as buccal, aspects of the crowns are strongly expended/inflated and gently sloping, a configuration not observed on upper premolars of species of *Algeripithecus*. On ONM-CBI-1-37, a short, thin crestule (entoprotocrista) links the protocone to the lingual cingulum (Fig. 3A). Another thin, short, buccally oriented crest extends from the buccal aspect of the protocone to the base of the paracone, and possibly corresponds to an endoprotocrista. This very short crest is present on both specimens (ONM-CBI-1-37 and -38; Fig. 3A, D), and is also visible on some P⁴s of *Al. minutus* (Fig. 4B; SOM Fig. S3K). In *Az. trerki*, this endoprotocrista is absent but a well-marked, long postprotocrista extends from the distobuccal aspect of the protocone to the base of the metacone (Fig. 4F; SOM Fig. S4F-J). Distolingually, the lingual cingulum on ONM-CBI-1-37 and -38 bears a minute but cuspate hypocone, which remains low, lingual and well inferior to the protocone. A long, arcuate distal cingulum extends from the hypocone to the distal part of the buccal cingulum. The distal crown margin shows no signs of invagination and is, on the contrary, well circular with a short radius of curvature.

The two upper molars (ONM-CBI-1-36 M² and ONM-CBI-1-35 M³; Fig. 3G-L) are bunodont, with rounded cusps, low relief, and weakly developed shearing crests. Both teeth are transversely elongated, rectangular, without any invagination of the distal crown margin. M² has four main cusps, including a strong hypocone, almost the same size as the protocone and metacone, although all three are slightly smaller than the paracone (Fig. 3G-I). M³ is only tri-cusped, without hypocone, and with a metacone smaller than the protocone, the latter being twice as small as the paracone (Fig. 3J-L). Both teeth show an azibid characteristic consisting in the buccal expansion of the paracone, which is the largest and taller cusp of the crown. In contrast, their metacone is less lingually offset (not only on M³ but also on M²) from the mesiodistal axis containing the paracone, than the condition observed on M²⁻³ of *Al. minutus* and *Az. trerki* (Fig. 4B, F). As on upper molars of *Al. minutus*, the base of the buccal crown margin is bordered by a complete, arcuate cingulum, extending from the mesial aspect of the paracone to the distal aspect of the metacone. This buccal cingulum is present but thinner in *Az. trerki*. As in *Al. minutus* and *Az. trerki*, there is no parastyle and metastyle at the extremity of the very short preparacrista and postmetacrista, respectively. Mesiodistally aligned with the latter, the postparacrista and premetacrista are also weakly developed, but
high enough to close the trigon basin buccally. The lingual flank of the crowns of both teeth is
not inflated as on the upper molars of *Al. minutus*, and more particularly *Az. trerki*. On the
ONM-CBI-1-35 M³, there is a complete lingual cingulum, linking the short mesial cingulum to
the long distal cingulum (Fig. 3J-L). On the ONM-CBI-1-36 M², the enamel is lacking on the
distolingual part of the crown, but the thickness of the lingual cingulum, directly beneath the
protocone, suggests that the lingual cingulum was also strong and complete (Fig. 3G-I). The
lingual cingulum is also present in upper molars of *Al. minutus*, but often broken, interrupted
between the hypocone and the protocone (Fig. 4B; SOM Fig. S3U-V, Z-A'). In *Az. trerki*, the
lingual cingulum of upper molars is virtually absent, and the lingual flank of the crowns
appears swollen (gently sloping; Fig. 4F; SOM Fig. S4A-B). As on M²s of *Al. minutus* and *Az. trerki*,
the ONM-CBI-1-36 M² has a strong hypocone, incorporated in the distolingual part of
the cingulum, and situated slightly lingual to the protocone. As in other azibiids, on the ONM-
CBI-1-35 M³, the hypocone is absent, but the distolingual cingulum is flared distally, forming a
well-marked cingular shelf as on M³s of *Al. minutus* (Fig. 4B; SOM Fig. S3Z-A'), but not as
extended distally as on M³s of *Az. trerki* (Fig. 4F). Both upper molars from Chambi display a
very small but distinct paraconule, marginally located on the mesial edge of the crowns and
on the midline. Distally and also on the midline, midway between the metacone and the
protocone, a faintly visible enamel swelling indicates the presence of a very small
metaconule. The presence of the two conules is also characteristic of azibiid upper molars,
although the metaconule is variably developed, rather well-defined in *Al. minutus*, and from
barely visible to absent on M¹⁻³ of *Az. trerki*. The paraconule is connected to a short
preprotocrista, which is only slightly developed (Fig. 3G-H, J-K), but nevertheless stronger
than on the molars of *Al. minutus* (Fig. 4B) and *Az. trerki* (Fig. 4F). The mesial cingulum
terminates at the lingual base of the paraconule. A preparaconule crista extends
mesiobuccally from the paraconule to join the mesiolingual part of the buccal cingulum, at
the level of the very short preparacrista. The arrangement of all these mesial structures is
similar to that found on upper molars of *Al. minutus* and *Az. trerki*. As in the case of these
taxa, on the M² and M³ of Chambi, there is no postprotocrista. Only a very low, thin crista
obliqua (or metacrista), consisting of a hypometaconule crista connects the metaconule to
the distobuccal flank of the protocone, thereby closing the trigon basin distally. Both
specimens also show a very short hypometacrista, connecting the lingual base of the
metacone to the metaconule, as can also be seen in *Al. minutus* (Fig. 4B) and *Az. trerki* (Fig.
4F).

Genus *Azibius* Sudre, 1975

Type species *Azibius trerki* Sudre, 1975.

Referred species *Azibius magnus* sp. nov.

Geographic and stratigraphic ranges Western Algeria, late early to early middle Eocene.
**Emended generic diagnosis** Genus with species larger than those of the genus *Algeripithecus*. Differs from *Algeripithecus* in that P₃-₄ have a less development of the metaconid, particularly on P₃, giving this tooth a less serrated morphology; M₃ with a longer trigonid and talonid, and a wider, more distally extended hypoconulid lobe; M₂ having a paracristid with no obliquity and with the cristid obliqua connecting to the middle of the distal trigonid wall rather than to the distobuccal aspect of the metaconid (as on M₁). Upper teeth also differ from those of *Algeripithecus*, particularly P⁴, which displays a smaller parastyle that is situated closer to the paracone, a more clearly defined and cuspate metacone, the presence of a tiny paraconule, a strong, long postprotocrista, and the absence of endprotocrista; M¹⁻² have virtually no metaconule (reduced to a trace), their lingual cingulum is practically non-existent or at least very widely interrupted, and their distal crown margins are convex rather than rectilinear buccolingually.

*Azibius magnus* sp. nov.

**Etymology** Epithet from the Latin adjective *magnus* (great), in reference to the status of this species as the greatest known.

**Holotype** UM-HGL50-264, right M₁ (Fig. 5M-P).

**Hypodigm** In addition to the holotype, UM-HGL50-258, right P³ or P⁴ (distobuccally damaged, crushed; Fig. 5A-C); UM-HGL50-260, right M² (heavily corroded and cracked in its mesiobuccal region; Fig. 5D-F); UM-HGL50-261, left M³ (heavily corroded; Fig. 5G-H); UM-HGL50-263, left P₃ (distalmost region broken; Fig. 5I-L); UM-HGL50-265, right M₁ (broken, lingual region missing; Fig. 5Q-R); UM-HGL50-266, right M₂ (heavily corroded, lacking the enamel layer; Fig. 5S-T); UM-HGL50-467, right talus (see Marivaux et al., 2011a). Dental measurements are reported in Table 1.

**Type locality** Glib Zegdou outlier level 50 (HGL50), Gour Lazib Complex, western Algeria (Fig. 1).

**Age** Late early to early middle Eocene (Sudre, 1979; Mahboubi, 1995; Mebrouk et al., 1997; Mebrouk and Feist, 1999; Mahboubi et al., 2002; Adaci et al., 2007, 2016; Mebrouk, 2011; Coster et al., 2012; Ravel et al., 2015, 2016).

**Diagnosis** Species almost two-thirds larger than *Azibius trerki*. Differs from *A. trerki* in having lower molars with well-defined, more strongly developed, continuous and contiguous buccal and mesiolingual cingulids, with a talonid basin almost entirely walled off lingually due to a stronger development of the postmetacristid, and more crowded teeth (overlapping crowns of molars and premolars); upper molars with distal crown margins more circular and extended distally, resulting in an enlarged talon; and in having morphologically simpler upper and lower (third and/or fourth) premolars.
**Nomenclatural remark** This new species must be referred to as *Azibius magnus* Marivaux, 2025, following the article 50.1 and the 'recommendation 50A concerning multiple authors' of the International Code of Zoological Nomenclature (ICZN, 1999).

## Description and comparisons

**Lower dentition** A single isolated tooth, which we identified as a lower third premolar due to its simpler occlusal pattern than that expected for a fourth premolar (UM-HGL50-263 P₃; Fig. 5I-K), is attributed to this new species. This attribution relies on its compatible size with other dental specimens of this species, and the presence of certain anatomical features otherwise found only on the lower molars of this species. The tooth is almost pristine, but lacks its distalmost region due to a break. Given the limited surface of breakage (Fig. 5I-J), only a very small part seems to be missing, suggesting that the talonid heel was very small, severely restricted buccolingually and mesiodistally. Although the roots are not preserved, the two circular areas of fracture visible under the cervix indicate that this tooth was double-rooted (Fig. 5J, L). The crown is oval in occlusal outline, longer than it is wide, dominated by a strong, tall main cuspid, the protoconid, and bears a continuous surrounding cingulid at the cervix. The buccal cingulid is particularly marked and bulging, conforming to the varying relief of the crown base (Fig. 5L), as on the lower molars referred to as the same species (UM-HGL50-264 and -265; Fig. 5N, Q). Mesially, the crown forms a large promontory overhanging the mesial root. A contact facet can be seen on the ventral side of this promontory (Fig. 5K), thereby indicating that the crown of this tooth substantially overlapped the distal part of the crown of the preceding premolar (P₂). A slight premolar crowding is also observed in *Az. trerki* (Fig. 4E; SOM Fig. S5B-C) and *Al. minutus* (Fig. 4A; SOM Fig. S2D). This case of crown overlap is also expected for the molars attributed to this new species (see molar description below). In mesial view (Fig. 5K), the enamel of the buccal aspect of the crown protrudes noticeably beyond the inferior margin of the lingual aspect of the tooth, thus describing a buccal exodaenodonty. In occlusal view, the protoconid is mesiodistally extended and particularly narrow (buccolingually compressed). On its mesial and distal flanks, it displays a thin, sharp preprotocristid and lateral protocristid, respectively, both aligned mesiodistally (Fig. 5I). The preprotocristid is shorter than the protocristid, but both have a similar inclination (gently sloping), giving the protoconid a dagger-like shape in lingual or buccal perspective (Fig. 5J, L). The mesial end of the preprotocristid and distal end of the protocristid are connected to very small but well-defined secondary cuspids, which could be interpreted as a paraconid and a metaconid, both buccally displaced and aligned with the protoconid on a mesiodistal axis. This mesiodistal cuspid alignment is characteristic of the premolar pattern of the Azibiidae (Fig. 4A, C, E). A key distinction between the P₃ of *Azibius* and that of *Algeripithecus* is the development of the metaconid, which is very small in *Azibius* (Fig. 4E; SOM Fig. SB-C; also in this new species, Fig. 5I-J, L) and very large in *Algeripithecus* (Fig. 4A; SOM Fig. S2B-D). Finally, on the UM-HGL50-263 P₃, it is worth noting a low, accessory enamel ridge, which is 'plated' on the lingual aspect of the protoconid (Fig. 5I-J). It runs obliquely (mesiobuccal -
distolingual orientation) up the protoconid flank, and its two extremities are free, i.e., without any connection with the apex of the protoconid and at the base of the crown on the cingulid.

Of the three lower molars, only UM-HGL50-264 (Fig. 5M-P), designated as the holotype of this new species, presents a complete and well-preserved occlusal crown surface, although several cracks can be seen. UM-HGL50-265 (Fig. 5Q-R) has approximately the same mesiodistal dimension and the same buccal characteristics, but it is missing a large part of its lingual region due to a fracture. UM-HGL50-266 (Fig. 5S-T) is complete but heavily corroded, and has lost its layer of enamel (the dentine is exposed), which alters the reading of its occlusal pattern. The comparable parts of the three teeth are morphologically very similar. These teeth have two roots, one mesial and one distal, which are mesiodistally compressed (buccolingual long axis). They are moderately crowned in lateral perspective, and bunodont with very bulbous main cusps, which are the protoconid, metaconid, hypoconid and entoconid. UM-HGL50-264 has a rectangular crown outline, longer than wide, with a trigonid that is only slightly narrower than the talonid (Fig. 5M). The trigonid is almost as long as the talonid, and slightly higher (Fig. 5N). The protoconid is very slightly more lingual than the hypoconid, positioned just buccal to the midline of the tooth. In contrast, the protoconid is markedly more mesial than the metaconid (Fig. 5M-N, P). However, it would appear that it is the metaconid that is distally displaced. The metaconid is also slightly more buccal than the entoconid on a mesiodistal axis. This distal and buccal displacement of the metaconid is one of the main characteristics of the first lower molars of the Azibiidae (Fig. 4A, C, E). On UM-HGL50-264 and UM-HGL50-265, the hypoconid is connected to a long and arcuate cristid obliqua, running partly up the distobuccal aspect of the metaconid (Fig. 5M-N, Q-R). The slightly lingual position of the protoconid, the distobuccal displacement of the metaconid, and the configuration of the cristid obliqua are among the main features that allow us to identify these teeth as M₁s. The corrosion and absence of enamel layer on UM-HGL50-266 limits the relief of the occlusal structures of this tooth. However, from the remanent relief of the enamel-dentine junction, it appears that the metaconid is less displaced distally, and that the cristid obliqua runs from the hypoconid partly up the distal wall of the trigonid, and does not seem to reach the metaconid (Fig. 5S-T). All these distinctions would suggest that UM-HGL50-266 is a M₂. At the base of the buccal aspect of their crown, UM-HGL50-264 and -265 display a well-marked, bulging cingulid, which is not observed on UM-HGL50-266 due to the absence of the enamel layer. This buccal cingulid is complete and continuous along the entire length of the crowns, wrapping around the protoconid and hypoconid, and continuing lingually on the mesial and distal crown margins up to the midline (Fig. 5M-O, Q-R). Distally, the buccal cingulid is particularly extensive, rising steeply up the distal flank of the crowns to reach the top of a strong postcristid (Fig. 5M-N, Q-R). Mesially, the buccal cingulid slopes gently up the buccal flank of the protoconid and continues lingually to span the mesiolingual base of the trigonid (Fig. 5M-O, Q-R). The development of a strong and long buccal cingulid is an autapomorphous condition of this species. This cingulid is present on the lower molars of *Az. trerki*, but is much thinner and generally incomplete, being absent around the hypoconid (Fig. 4E; SOM Fig. S4K-L). In *Al. minutus*, the buccal cingulid is well marked, but also
incomplete, missing around the hypoconid (Fig. 4A; SOM Fig. S2A-C). The mesiolingual cingulid can be present on some specimens attributed to this species. In contrast, in *Al. minimissimus* sp. nov., the buccal cingulid is almost non-existent, or reduced to a trace (Fig. 3Q-R, T). On UM-HGL50-264 and -265, the protoconid displays a markedly long and mesially directed preprotocristid, which show a small but well-distinct enamel swelling in its mesial extremity. As in *Az. trerki* (Fig. 4E), *Al. minutus* (Fig. 4A) and *Al. minimissimus* sp. nov. (Fig. 4C), this bulge, mesial to the protoconid, is interpreted as a small and buccally displaced paraconid (Fig. 4G). Similar to the $M_1$s of the above-mentioned taxa, UM-HGL50-264 has neither a paracristid (like UM-HGL50-265) nor a premetacristid, leaving the trigonid wide open lingually (Fig. 5M, P, R). The distal wall of the trigonid consists of a moderately notched protocristid (the lateral protocristid being stronger than the medial protocristid). On the UM-HGL50-264 $M_1$, the hypoflexid is transversely extended due to the configuration of the cristid obliqua that runs far lingually to reach the metaconid; but it remains shallow due to the swollen buccal flank of the protoconid, which obstructs it. On the talonid, the entoconid is slightly distal to the hypoconid, and displays a short pre-entocristid and a slightly longer postentocristid. The metaconid extends distally via a thin and gently sloping postmetacristid. The latter joins the mesial end of the pre-entocristid, almost completely closing the talonid basin lingually. The lingual margin of the talonid appears as a wide, open V-shaped notch (Fig. 5P), somewhat asymmetrical due to the difference in height between the metaconid and the entoconid (lower). Distally, the postentocristid is straight and extends buccally, joining a strong hypocristid of equal length on the crown midline. These two cristids make up the postcristid, which forms the distal crown margin. The junction of these two distal cristids is also the point where the distobuccal cingulid (running up the distal crown margin) meets. This triple junction results in a small bulge of enamel, which could be similar to a hypoconulid (Fig. 5M). Apart from the presence of a strong and complete buccal cingulid and the almost closed lingual margin of its talonid, the UM-HGL50-264 $M_1$ (Figs 4G and 5M-P) could be regarded as an enlarged version of the UM-HGL50-248 $M_1$ (Fig. 4E; SOM Fig. S4K-O) attributed to *Az. trerki*, due to its very similar occlusal pattern. Finally, as on the unique premolar ($P_3$) recovered and attributed to the same species, on UM-HGL50-264 and -265, the mesialmost part of their crown forms a promontory that overhangs the mesial root. On each of these teeth, a contact facet is visible on the ventral side of this promontory (Fig. 5N-P, Q). These interstitial marks indicate that the crown of these $M_1$s overlapped the distal part of the $P_4$. An overlapping of the crowns (inter-molar, molar-premolar and inter-premolar crowding) is also observed in *Az. trerki* (Fig. 4E; SOM Fig. S5B-C) and *Al. minutus* (Fig. 4A; SOM Fig. S2A-D), but to a lesser extent.

**Upper dentition** A single upper premolar (UM-HGL50-258; Fig. 5A-C) was found and is tentatively attributed to this new species on the basis of its size compatible with the molars and certain morphological features that are consistent with those of the upper and lower molars attributed to this species. The tooth is slightly crushed and shows several cracks, but retains its integrity. It was three-rooted, with two small buccal roots and one larger lingual root. Its occlusal outline is wider than it is long, almost rectangular, with a buccal margin
barely longer than the lingual margin (Fig. 5A). The distal crown margin is slightly invaginated, a somewhat surprising trait as it is not seen on the upper premolars or even the upper molars of *Azibius trerki*, and *Azibiidae* in general (Fig. 4B, D, F). The crown is bunodont with two main cusps: a massive, high paracone and a much smaller, squat (almost half as high) but well-cuspate protocone (Fig. 5A-C). These two main cusps are aligned on a buccolingual axis. The mesial and distal edges of the paracone are sharp and gently sloping, indicating the presence of a preparacrista and a postparacrista, respectively (Fig. 5A-B). These two buccal crests on either side of the paracone are aligned on a mesiodistal axis. The buccal side of the paracone is relatively steep, whereas its lingual side has a much gentler slope (Fig. 5C), with a smooth hypoparacrista in its center, demarcating a mesiolingual face and a distolingual face for this cusp. In mesiolingual perspective, the paracone takes the form of a pyramid (Fig. 5B). There is a weak but well-defined, continuous buccal cingulum, a trait that is common on the upper premolars of *azibiids* (Fig. 4B, D, F; SOM Fig. S3K). A low, continuous and sinuous distal cingulum extends along the entire width of the crown. Distobuccally, it is contiguous with the buccal cingulum, and distolingually, it is interrupted, ending at the base of the distal flank of the protocone. There is no trace of lingual cingulum, nor any hypocone development on the lingual terminus of the distal cingulum. The absence of lingual cingulum is a characteristic of the upper premolars of *Azibius* (*Az. trerki*; Fig. 4F; SOM Fig. S4F-J), whereas in species of *Algeripithecus*, upper premolars always have a lingual cingulum, with variable degree of development (Fig. 4B, D; SOM Fig. S3A-O). In contrast, UM-HGL50-258 does not show the strong expansion of the lingual margin, as can be seen in particular on P⁴s of *Az. trerki* (Fig. 4F; SOM Fig. S4F-J). A mesial cingulum is present, but it is very limited in length and restricted to the mesiolingual corner of the crown. The protocone displays a thin, very low and short preprotocrista, which connects to a very small enamel swelling, corresponding to a tiny paraconule, from which a preparaconule crista extends mesiobuccally to reach the buccal cingulum. There is neither postprotocrista, nor centrocrista, and the trigon is open distally. Mesiobuccally, the mesial end of the preparacrista is connected to a well-defined and cuspate parastyle (Fig. 5A-B). A similar development of the parastyle is observed on the P⁴s of *Az. trerki* (Fig. 4F; SOM Fig. S4F) and *Al. minimissimus* sp. nov. (Fig. 3 A-B), whereas on their respective P³s, this style is much less marked (Figs 3D-E and 4D, F). In contrast, in *Al. minutus*, the parastyle is particularly/unusually strong and protruding on P⁴s (Fig. 4B; SOM Fig. S3K-M), and much less developed on its single known P³ (Fig. 4B; SOM Fig. S3F-H). It remains difficult to determine whether UM-HGL50-258 is a P⁴ or a P³. This tooth has a transverse crown outline and displays a relatively strong protocone, as on the P⁴s of *Az. trerki* or *Al. minutus*, whereas this cusp can be much reduced on the P³s of these taxa. On the other hand, UM-HGL50-258 has no hypocone development, a cusp that is present in varying degrees of development on the P⁴s of these taxa, and weakly developed to absent on the P³s of these same taxa. In addition, UM-HGL50-258 shows no metacone and/or metastyle development, an absence that is usually observed on P³s of *Az. trerki* and species of *Algeripithecus*. On P⁴s of *Algeripithecus*, the metastyle or metacone remains weak, whereas in *Az. trerki*, the metacone
is strongly developed. Also, identifying UM-HGL50-258 as a P³ rather than a P⁴ could be an
appropriate option, although further material is still required to support this hypothesis.

The only two upper molars available to document this new species are particularly
corroded and/or abraded (Figs 4H and 5G–L). Their occlusal pattern is smoothed, which
attenuates or erases certain anatomical details, but the main structures remain legible. UM-
HGL50-260 is tentatively identified as a M² due to the size and position of its metacone, which
appears to be subtly smaller and only slightly more lingual than the paracone, as is the case
on the M²s of the other known Azibiidae (Fig. 4B, D, F). The tooth seems bunodont with four
main cusps, which are the paracone, protocone, metacone and hypocone. The paracone and
protocone are similar in size and slightly larger than the metacone and hypocone. The
paracone and metacone are connected by moderately developed and elevated postparacrista
and premetacrista, both of which meet and close the trigon basin buccally (Fig. 5D–E). In
contrast, there is neither development of the preparacrista and postmetacrista nor of the
buccal styles (parastyle and metastyle). One of the main and striking features of this tooth is
the conspicuous buccal expansion of the paracone and metacone, clearly much more marked
than on M²s of *Az. trerki* and species of *Algeripithecus*. This may be related to the smoothing
of the buccal wall of the crown, which possibly merges the swollen, expansive and gently
sloping buccal flanks of the paracone and metacone with a buccal cingulum. But there are no
structural clues as to whether a buccal cingulum is present or not (Fig. 5F). There is also a
strong lingual expansion of the protocone, as can be seen in the upper molars of *Az. trerki*.
The enamel layer appears to be missing at the cervix, making it impossible to determine
whether a lingual cingulum was present or not. The distal crown margin is also particularly
expansive. It is convex, well-circular with a great radius of curvature, which substantially
enlarges the surface area of the talon basin. The large hypocone appears to be buccally
displaced and positioned distal to the protocone, rather than lingual to the protocone as on
M¹⁻² of *Az. trerki* and species of *Algeripithecus* (Fig. 4B, D, F). Mesially, below the crown
midline, a tiny dentine pit surrounded by a slight enamel bulge testifies to the presence of a
paraconule, which is connected to the protocone by a seemingly strong and long
preprotocrista. A preparaconule crista seems to be present and to extend mesiobuccally, but
an enamel crack in this region of the crown does not allow its course to be followed. The
region distal to the protocone is too smooth, making it impossible to see whether this cusp
has a postprotocrista. On the other hand, the hypocone appears to have a short mesiobuccal
spur, which could be a small prehypocrista. This short and very low crest can be seen on M¹⁻²
of *Az. trerki* (Fig. 4F). The trigon basin appears closed distally. This closure, although low,
results from the presence of a low hypometacrista complex, a structure characterizing upper
molars of azibiids (Fig. 4B, D, F). On HGL50-260, the high degree of abrasion and smoothing
makes it impossible to observe whether a metaconule is present or absent.

UM-HGL50-261 (Fig. 5G–H) is identified as a left M³ due to its reduced size, transverse
(much wider than long) and oval crown outline, and especially its metacone which is strongly
offset lingually with respect to the paracone. This tooth is heavily corroded, but the remaining
occlusal relief indicates that the crown was dominated by two strong cusps, the paracone and protocone. The metacone is noticeably smaller, almost twice as small as the other two cusps. Despite of the corrosion and the advanced degree of wear, it seems that there was no lingual cingulum. The distal cingulum, which forms the distal margin of the crown, is convex, well-circular, with an important radius of curvature, as on M². As in other azibiids, it is distolingually flared, with no hypocone development. Mesially, the presence of a small dentine pit surrounded by an enamel bulge would indicate the presence of a paraconule, which is connected to the protocone by a short preprotocrista. A low but long preparaconule crista extends buccomesially from the paraconule to the mesial base of the paracone, into which it appears to merge. The buccal aspect of the crown is too corroded to assess the development of a buccal cingulum. The paracone appears inflated but its buccal expansion seems to have been erased by corrosion. A strong postparacrista meets a shorter, weaker premetacrista, thus closing the trigon basin buccally. As in other azibiids, there is neither development of the preparacrista and postmetacrista nor of the buccal styles (parastyle and metastyle).

Family ?Djebelemuridae Hartenberger and Marandat, 1992 (sensu Godinot, 2010)

Genus *Lazibadapis* gen. nov.

**Etymology** Refers to the Gour Lazib, a region of the Hammada du Dra, situated in the north-western edge of the Sahara in western Algeria, combined with *adapis* (ad., Latin preposition meaning ‘close to’, and *Apis*, Greek word derived from the deity *Hapis*, the ‘sacred bull’ of the Egyptian mythology), in reference to *Adapis* Cuvier, 1821 (the first named adapiform primate).

**Type and only known species** *Lazibadapis anchomomyinopsis* sp. nov.

**Geographic and stratigraphic ranges** Western Algeria, late early to early middle Eocene.

**Diagnosis** Tiny primate, about one-third smaller than the djebelemurid *Djebelemur martinezi*. Differs from known djebelemurids (*Djebelemur*, ‘*Anchomomys*’ *milleri*, *Omanodon*, and *Shizarodon*) in having lower molars without premetacristid development, shorter, non-sharp preprotocristid and much lower paracristid (cingulid-like cristid), making the trigonid basin shorter, non-expansive and open mesiolingually, and in bearing a smaller entoconid, faintly differentiated (barely cuspidate) on the long cristid forming the lingual crown margin; upper molars with a shorter postmetacrista and absence of buccal metastylar shelf; differs more specifically from *Djebelemur* in having upper molars with a less pronounced invagination of the distal crown margin; differs more particularly from *Omanodon* in that its upper molars show no trace of hypocone development in the distal part of their lingual cingulum.
**Etymology** Combination of anchomomyin and *opsis*, Greek for 'like', referring to the tribal morphological resemblance of this species (in reference to the Anchomomyini, a tribe of the Cercamoniinae Notharctidae, among the Adapiformes).

**Holotype** UM-HGL50-325, partial left mandible (without bone structure) preserving M<sub>2-3</sub> (Fig. 6L-N).

**Hypodigm** In addition to the holotype, UM-HGL50-326, right M<sup>1</sup> (broken, buccal region missing; Fig. 6G-H); UM-HGL50-169, right M<sup>2</sup> (heavily corroded, with virtually no enamel layer; Fig. 6E-F); UM-HGL50-170, right M<sup>3</sup> (or M<sup>2</sup>; Fig. 6A-D); UM-HGL50-290, left M<sub>3</sub> (distobuccally damaged; Fig. 6I-K). Dental measurements are reported in Table 1.

**Type locality** Glib Zegdou outlier level 50 (HGL50), Gour Lazib Complex, western Algeria (Fig. 1).

**Age** Late early to early middle Eocene (Sudre, 1979; Mahboubi, 1995; Mebrouk et al., 1997; Mebrouk and Feist, 1999; Mahboubi et al., 2002; Adaci et al., 2007, 2016; Mebrouk, 2011; Coster et al., 2012; Ravel et al., 2015, 2016).

**Diagnosis** As for the genus.

**Nomenclatural remark** This new genus and species must be referred to as *Lazibadapis anchomomyinopsis* Marivaux, 2025, following the article 50.1 and the 'recommendation 50A concerning multiple authors' of the International Code of Zoological Nomenclature (ICZN, 1999).

## Description

**Lower dentition** UM-HGL50-325 (holotype; Fig. 6L-N) represents a left M<sub>2-3</sub> from a single individual. The fragile and weathered dentary bone was disintegrated during the extraction of the specimen by acid etching procedures, despite all the usual precautions taken to protect the bone structures. The two teeth, by contrast, are perfectly preserved and almost pristine. The attrition wears on the apices of the main cuspids, however, indicate that these two molars (M<sub>3</sub> in particular) were erupted and functional. These molars are two-rooted, with their crown clearly wider and protruding further than the width of the root shaft (Fig. 6M-N). In occlusal view (Fig. 6L), the crowns are characterized by a very short trigonid compared with the very long, extensive talonid basin. On M<sub>3</sub> (UM-HGL50-325 as well as on the isolated UM-HGL50-290 specimen; Fig. 6I), the talonid is even more elongated due to the presence of a strong, distally protruding and lobate hypoconulid. The latter is situated on the midline of the crown. In lateral view (Fig. 6M-N), the trigonid is markedly higher than the talonid. The main trigonid cuspids are the protoconid and metaconid, which are both bulbous, conical, acute and much higher than the two main talonid cuspids, the hypoconid and entoconid (regardless
of the hypoconulid on M₃), which are much less cuspidate and not very prominent. These two
talonid cuspids are marginally located on the lingual and buccal edges of the crown, and the
outer flank of each is steep-sided (Fig. 6I). On both teeth, the trigonid is as wide as the
talonid, but lingually, while the metaconid is aligned with the entoconid on a mesiodistal axis,
buccally, the protoconid is more lingual than the hypoconid. Despite the more lingual position
of the protoconid apex compared to the hypoconid apex, the swollen, sloping buccal flank of
the protoconid makes the occlusal outline of the crown rectangular, with the trigonid and
talonid widths being equal (Fig. 6I-J, L-M). In addition, a slightly protruding buccal cingulid
wraps around the base of the protoconid (mesially and buccally), but does not extend
markedly distally beyond it. At the base of the hypoconid, the buccal cingulum is only a trace,
appearing as a barely pronounced enamel bulge. On the UM-HGL50-325 M₂, the buccal
cingulid does not span the hypoflexid; it interrupts abruptly just behind the protoconid (Fig.
6L-M). A shallow, concave notch along the buccal margin of the hypoflexid marks the break
of this cingulid. Lingually, whether on the single M₂ or the two M₃s, the metaconid is clearly
located distal to the protoconid on a buccolingual axis (Fig. 6I-N). The entoconid is also
positioned slightly distal to the hypoconid. The protoconid and metaconid are linked by a
strong, trenchant protocristid. This cristid, forming the distal wall of the trigonid, is
moderately notched, including the lateral protocristid and the medial protocristid, both of
equal length (Fig. 6I, L). A very short, barely developed preprotocristid extends mesially from
the protoconid. In its mesial end, a minute but well-defined enamel swelling indicates the
presence of a tiny paraconid, which occupies a very buccal position, almost mesial to the
protoconid (Fig. 6I, L). An oblique, very low, somewhat cingulid-like paracristid extends
distolingually from the paraconid up the base of the mesial flank of the metaconid. The latter
is swollen and does not show any premetacristid development. Due to the very low
paracristid and the absence of premetacristid, the trigonid basin remains lingually wide open
(Fig. 6I, K, L, N). A thin, sharp postmetacristid plunges distally from the apex of the metaconid
towards the entoconid. As the metaconid is much higher than the entoconid (which is very
low), the postmetacristid is very steep. The entoconid displays thin, sharp pre-entocristid and
postentocristid, and its apex barely protrudes in the middle of these two cristids. The pre-
entocristid joins the postmetacristid in the middle of the lingual crown margin, closing the
talonid basin lingually. On M₂ (UM-HGL50-325; Fig. 6L), the postentocristid is arched in its
lingual part, and remarkably long, extending buccally to join a shorter, oblique postcristid. At
the junction point, a small enamel swelling could be viewed as a minute hypoconulid (Fig.
6L-M). On the M₃s, the postentocristid and postcristid are oblique, backwardly directed and
converge to join the hypoconulid located very distally. Lingually, the hypoconid displays a
long, thin, cutting cristid obliqua, which extends mesiolingually and runs part way up the
distal wall of the trigonid, but without reaching the top of the protocristid (Fig. 6J, L-M). On
M₂, the cristid obliqua reaches the trigonid wall at the junction between the two branches of
the protocristid. On the M₃s, it reaches the trigonid wall slightly more buccally, at a point
distolingual to the protoconid, and thus the hypoflexid is less transversely extended on these
molars than on M₂ (Fig. 6I, L).
**Upper dentition** Three upper teeth are associated with the lower molars described above, given their compatibility both in size and occlusal structure. All three are molars, and only one is well preserved and complete (UM-HGL50-170; Fig. 6A-D); of the other two, one is broken (UM-HGL50-326, with its buccal part missing; Fig. 6G-H) and the other heavily corroded (UM-HGL50-169, with its enamel layer almost entirely lost; Fig. 6E-F). These three upper molars are characterized by an occlusal pattern comprising three acute, salient main cusps arranged in an almost isosceles triangle, the presence of well-defined cingula at the base of the crown, and by a network of moderately developed, sharp transverse and longitudinal crests. Based on UM-HGL50-169 and -170, which are unbroken, these upper molars are wider than they are long, with a sub-rectangular or even triangular occlusal outline (their buccal margin is slightly longer than their lingual margin), and they show a very slight invagination of their distal margin. UM-HGL50-326 shows a more pronounced invagination of its distal crown margin (Fig. 6G-H), suggesting that this tooth is more likely a M¹. UM-HGL50-169 has a paracone similar in size to the metacone, and these two buccal cusps are aligned on a mesiodistal axis, a configuration which suggests that this tooth is possibly a M². UM-HGL50-170 has a metacone that is smaller and slightly more lingual than the paracone, as well as a distal crown margin that is only slightly invaginated, a set of features suggesting that this tooth is more likely to be a M³ (there is otherwise no contact facet on the distal aspect of the crown). However, these possible hypotheses for assigning dental locus numbers to these isolated teeth remain open, given the paucity of the material available, and the limited criteria for distinguishing them. The development of the cingula cannot be assessed on UM-HGL50-169 (Fig. 6E) because the enamel layer has been lost. In contrast, on UM-HGL50-170 (Fig. 6A) and -326 (Fig. 6G), there is a faint, thin mesial cingulum over the entire lingual half of the crown, in continuity with a complete, uninterrupted lingual cingulum, which widens mesiodistally and extends distobuccally over the entire distal margin of the crown. This distal cingulum ends at the base of the distal flank of the metacone. Whatever the tooth concerned, there is no trace of hypocone on the distolingual section of the cingulum. On UM-HGL50-170, a weak but well-defined buccal cingulum runs along almost the entire length of the crown (Fig. 6A, C-D). Mesial to the paracone, and slightly offset buccally from this cusp, there is a small parastyle, which is not very high but otherwise more developed on the buccal side of the crown, appearing as a bulge of enamel (Fig. 6A-D). It is connected to the paracone by a short, very steep preparacrista. Distobuccally, the metacone displays a very low, smooth postmetacrista. It is barely visible, arching distobuccally and descending abruptly on the distobuccal flank of the metacone, to join the distal end of the buccal cingulum (Fig. 6A, D). The paracone and metacone are linked via the development of moderately high but trenchant postparacrista and premetacrista, respectively (Fig. 6A-B, D). These two shearing crests are mesiodistally aligned and their union closes the trigon basin buccally (high buccal wall in lingual view; Fig. 6B). On UM-HGL50-170, due to the difference in height between the paracone (higher) and the metacone (lower), the buccal wall of the trigon basin appears as an asymmetric, wide-open V-shaped notch in buccal and lingual views (Fig. 6B, D). With the addition of the preparacrista and the weak postmetacrista, the total buccal cutting-edge development (i.e.,
eocrista; see SOM Fig. S1) is M-shaped from a lateral perspective (Fig. 6D). Lingually, the protocone displays a preprotocrista and a postprotocrista, which are both low but well-defined and sharp. The preprotocrista extends mesiobuccally. It is long and gently sloping, joining a small, low paraconule located on the mesial margin and the midline of the crown (Fig. 6A–C). A long, low, almost cingulum-like preparaconule crista extends mesiobuccally, in line with the preprotocrista, and joins the parastyle (Fig. 6A–C). Regarding the postprotocrista, it is difficult to assess its length as it is continuous with a metacrista (= crista obliqua; see SOM Fig. S1). In mesial view, particularly on UM-HGL50-170 (Fig. 6C) and UM-HGL50-326, a subtle break in slope can be seen on this distal transverse crest, suggesting that the postprotocrista is short and merged with a long metacrista. On UM-HGL50-326, there is a very small enamel swelling on the metacrista, which could indicate the presence of a tiny, barely visible metaconule (in this case, the metacrista is a hypometaconule crista). On the three molars, a short, thin but well-defined hypometacrista is present, and connected to the metacrista (or hypometaconule crista), thereby forming a hypometacrista complex that completely closes the trigon basin distally. Mesially, there is no trace of hypoparacrista development on the lingual flank of the paracone, which remains free-standing and moderately steep-sided. This leaves the trigon basin open mesially.

## Comparisons

These few teeth are non-bunodont, with no lingual or buccal expansion of their crowns, and have a rather gracile general appearance, with acute cusp(-id)s and sharp, well-marked crests and cristids. The dental pattern of this small primate species from Glib Zegdou (HGL50) contrasts quite markedly with that of the larger, sympatric species that document the Azibiidae (*Algeripithecus minutus*, *Azibius trerki*, and *Az. magnus* sp. nov.). However, this species shares with azibiids a suite of strepsirrhine dental affinities that are otherwise found in another primate group from North Africa, the Djebelemuridae. This is particularly noticeable in the configuration of the lower molar trigonid, which is characterized by a reduced, buccally displaced paraconid, a mesiodistally oriented preprotocristid, and a low, oblique paracristid (mesiobuccally-distolingually oriented). The gracile general appearance, with acute cusp(-id)s and well-marked crests and cristids, is characteristic of one of the earliest Djebelemuridae known to date, *Djebelemur martinezi* (Fig. 4I–J), from the late early to early middle Eocene of Chambi in Tunisia (CBI-1; Hartenberger and Marandat, 1992; Marivaux et al., 2013). This taxon has long been known as the one and only oldest representative of this lineage of strepsirrhine primates that existed for several million years in Afro-Arabia, as attested by the presence of some of its last representatives recorded in the latest Eocene of Egypt/Fayum ('*Anchomomys' milleri*; Simons, 1997; Seiffert et al., 2005b) and in the early Oligocene of the Sultana of Oman/Taqah (*Omanodon minor* and *Shizarodon dhofarensis*; Gheerbrant et al., 1993; Godinot, 2006, 2010) and the Atlantic Sahara/Dakhla (cf. '*Anchomomys' sp.'; Marivaux et al., 2024). The taxon from HGL50 is almost a third smaller than *D. martinezi* (Fig. 4I–L) and differs from the latter, as well as from other more recent
djebelemurids, in having lower molars characterized by a shorter trigonid, due in part to the brevity of the preprotocristid. This cristid, which connects the protoconid to the tiny paraconid, is very weakly differentiated in these molars; it is very low and not very sharp. The same applies to the paracristid, which is much less developed and much lower than on the lower molars of djebelemurids, and appears as a cingulid-like mesial cristid. The HGL50 taxon also differs from *Djebelemur*, ‘*A.* milleri, *Omanodon* and *Shizarodon*, in the absence of a premetacristid on the mesial flank of the metaconid. The lack of development of this cristid and the very low elevation of the paracristid leave the trigonid basin largely open mesiolingually, a configuration that contrasts with the closed trigonid of *Djebelemur*, ‘*A.* milleri, *Omanodon* and *Shizarodon*. A mesiolingually open trigonid is found in azibiids, but only on their $M_1s$ (i.e., lack of premetacristid and very low to almost absent paracristid; Fig. 4A, C, E, G), which have a configuration that is otherwise very distinctive and divergent in other respects (cuspid displacement; see descriptions and comparisons earlier in the text). In azibiids, post-$M_1$ molars have their trigonid closed mesiolingually with accentuated premetacristid and paracristid development from $M_2$ to $M_3$ (Fig. 4A, C, E). As in *Djebelemur*, the lower molars of the HGL50 taxon are also characterized by a small, very discreet entoconid that barely protrudes from the lingual wall of the talonid basin. This condition of the talonid cuspid in these two coeval taxa contrasts sharply with the strongly cuspidate and prominent entoconid that forms a lobe on the distolingual angle of the lower molar talonid in the other three known and more recent Djebelemuridae ('*A.* milleri, *Omanodon*, and *Shizarodon*).

The few upper molars from HGL50 attributed to this taxon (Figs 4L and 6A–H) show a simple three-cusp structural pattern. With sharp crests, pointed and salient cusps, the absence of a hypocone, well-developed cingula and a very slight invagination of the distal crown margin, these specimens differ markedly from upper molars of the Azibiidae (Fig. 4B, D, F, H), and to some extent show more affinities with the Djebelemuridae. To date, only *Djebelemur* and *Omanodon* have documented the morphology of the upper molars of the Djebelemuridae (Gheerbrant et al., 1993; Marivaux et al., 2013). As with the upper molars of *Omanodon*, the HGL50 specimens (especially UM-HGL50-169 and -170) show very slight invagination of the distal crown margin and weak development of the postmetacrista. In contrast, these two features are strongly expressed on upper molars of *Djebelemur* (i.e., very deep invagination and long, distobuccally directed postmetacrista forming a full-fledged metastylar shelf), making the morphology of the upper molars of this taxon somewhat unique. However, UM-HGL50-169 is heavily corroded (Fig. 6E–F), an alteration that may have greatly attenuated both the shape of the distal crown margin and the appearance of the postmetacrista. UM-HGL50-326, broken and lacking the buccal region (Fig. 6G–H), is much less corroded and has a pronounced invagination of its distal margin. With regard to UM-HGL50-170 (Fig. 6A), if the identification of this tooth as a $M^3$ is correct, the minimal invagination of its distal margin and the very weak development of the postprotocrista could be expected conditions, as they correspond to those observed on the $M^3$s of *Djebelemur*. However, if this tooth is proven to be a $M^2$, its dental pattern diverges significantly from that
of the M²s of *Djebelemur*. In any case, none of these three upper teeth from HGL50 show the development of a hypocone on the lingual cingulum, as is also the case on the upper molars of *Djebelemur*, unlike *Omanodon*, whose M¹ shows a well-defined and cuspate hypocone, and M², a tiny enamel bulge on the distolingual cingulum (Gheerbrant et al., 1993, plate 2).

The morphological features of the lower molars of this small HGL50 taxon that are shared with the Djebelemuridae and Azibiidae (e.g., short trigonid, reduced and buccally displaced paraconid, oblique paracristid) are also found in the oldest known African representatives of the crown strepsirrhines from the late Eocene, such as *Wadilemur*, *Saharagalago*, *Karanisia* and *Plesiopithecus* (e.g., Seiffert et al., 2003, 2005b; Jaeger et al., 2010; Gunnell et al., 2018). However, as with the djebelemurids and azibiids, the specimens from HGL50 display a shorter and weaker preprotocristid, as well as a less-developed paracristid that remains low, appearing as a discrete mesial cingulid. They also lack a premetacristid; thus, the mesial flank of the metaconid is steep-sided and free-standing, leaving the trigonid basin open lingually (closed in the lower molars of early crown strepsirrhines). The upper molars of the HGL50 taxon also differ from those of *Karanisia*, *Wadilemur* and *Saharagalago* in the absence of hypocone development on the distolingual cingulum. Additionally, this cingulum does not extend distally to form a protruding lobe on the distolingual margin as it does on the upper molars of these early crown strepsirrhines. As a result, the distal crown margin of the HGL50 dental specimens is only faintly invaginated, in contrast to the pronounced and deep distal crown invagination observed in *Wadilemur* and *Saharagalago* (and to a lesser extent in *Karanisia*).

This dental material from HGL50, although limited, undoubtedly represents a new genus and species, based on a number of unique features and the estimated small body size. The small number of specimens available (including one broken and another corroded) and the lack of several dental loci (upper and lower premolars, lower first molar, etc.) prevent us from accessing the extent of the dental morphology of this taxon and, moreover, its variability. Although the morphological patterns of these lower and upper molars clearly distinguish this new taxon from the Azibiidae and, more broadly, from other more recent taxa representing the oldest known crown strepsirrhines, its affinities with the Djebelemuridae, although noteworthy, remain nonetheless tenuous due to the absence of certain diagnostic characters of this family (e.g., long and trenchant preprotocristid, high paracristid, and presence of premetacristid). As a result, the inclusion of this new taxon in the Djebelemuridae is proposed here on a provisional basis only, pending the discovery of further fossils.

It is worth mentioning that the morphology of the molars of this tiny new taxon from HGL50 (*Lazibadapis* gen. nov.), as is also the case for the molar pattern of djebelemurids and azibiids, is somewhat reminiscent of that of some anchomomyin cercamoniines (Notharctidae, Adapiformes) from the middle Eocene of Europe (e.g., *Anchomomys gaillardi*, *A. frontanyensis*, *Nievesia sossisensis*; e.g., Stehlin, 1916; Godinot, 1998, 2006, 2015; Marigó et al., 2011, 2013). It should be remembered here that at the time of their original description, *Djebelemur*, ‘A.’ milleri, *Omanodon* and *Shizarodon* (as well as *Wadilemur*) were
considered to be cercamoniine adapiforms due to their anchomomyin-like molar features (Hartenberger and Marandat, 1992; Gheerbrant et al., 1993; Simons, 1997). This is partly due to the morphology of their lower molars, which, as in anchomomyins, are characterized by a very short trigonid compared to the long talonid, a tendency for the paraconid to be strongly reduced (to absent) and shifted buccally, almost mesial to the protoconid and thus involving a mesiodistally oriented preprotocristid, and finally by the presence of a low, oblique paracristid (mesiobuccally-distolingually oriented). However, on the basis of the almost complete lower toothrows available only for *Djebelemur* and ‘*A.’ *milleri*, and in the light of subsequent fossil discoveries documenting crown strepsirrhines (especially *Wadilemur elegans*, a stem lorisiform from the latest Eocene of Egypt; Seiffert et al., 2005b), it turned out that the transformations observed on the ante-molars teeth of *Djebelemur* and ‘*A.’ *milleri* clearly distinguish them from the anchomomyin cercamoniines of Europe (Godinot, 2006, 2010; Seiffert, 2007a, 2012; Marivaux et al., 2013). Nevertheless, on the $M_{2-3}$ of *Lazibadapis*, the absence of a premetacristid leaving the trigonid open mesiolingually, is a condition found in most anchomomyins (with the exception of some specimens of *Buxella*; e.g., Godinot, 1988, 2006), which contrasts sharply with the closed condition of djebelemurids, azibiids (Fig. 4) and early crown strepsirrhines. In *Lazibadapis*, the paracristid is, however, much lower (cingulid-like cristid), and the entoconid is much less cuspidate than on the lower molars of anchomomyins. The upper molars of *Lazibadapis* also have many features in common with those of the anchomomyins, and differ only subtly, in particular they have a complete lingual cingulum, no sign of hypocone development, and display a much smaller paraconule. Overall, the available upper and lower molars attributed to *Lazibadapis* appear to be slightly less bunodont than the condition characterizing these teeth in anchomomyins.

A final comparison of this new taxon from Glib Zegdou deserves to be made with another group of strepsirrhine primates from the Paleogene of Africa, the Caenopithecinae (Adapidae, Adapiformes). This group of primates is well documented by very specialized/derived, large taxa from the late Eocene of Egypt (Fayum: *Aframonius dieides*, *Afradapis longicristatus*, and *Masradapis tahai*; Simons et al., 1995; Simons and Miller, 1997; Seiffert et al., 2009, 2018), but the occurrence of this adapid lineage in Africa can be traced back to the middle Eocene, particularly in Namibia (Sperrgebiet-Black Crow), with much less specialized taxa (*Notnamaia bogenfelsi* and *Namadapis interdictus*; Pickford et al., 2008; Pickford and Uhen, 2014; Godinot et al., 2018), and as such, more relevant for a comparison with *Lazibadapis*. Unfortunately, as with *Lazibadapis*, there are few fossil remains documenting these ancient taxa. Based on elements that can be compared (a fragment of maxilla for *Notnamaia* and a lower jaw for *Namadapis*), it is clear that the dental pattern of *Lazibadapis* differs substantially. The upper molars ($M^{2-3}$) of *Notnamaia* differ markedly from those of *Lazibadapis* in showing enlarged, bulbous cusps, strong transverse crests (post- and pre- protocristae), the absence of a lingual cingulum, non-invaginated distal crown margins, and $M^2$ having strong, well-defined, cuspate conules and a conspicuously large hypocone. The lower molars of *Namadapis* differ from those of *Lazibadapis* in many ways, especially in having bulbous, well-defined and cuspidate main cuspids, notably the entoconid, which is as large as the other cuspids, the development
of strong and trenchant cristids (protocristid, preprotocristid, cristid obliqua, and postcristid), a lingually open talonid basin (absence of lingual wall due to the very limited length of the postmetacristid and the absence of the pre-entocristid), in displaying a stronger buccal cingulid wrapping around the hypoconid and spanning the hypoflexid, and in the configuration of their trigonid, which is longer and much more extended mesiodistally, with a strong, very long, oblique, mesiolingually directed preprotocristid, connecting the protoconid to a very small, somewhat undifferentiated paraconid. The latter is located on the midline of the crown between the protoconid and the metaconid, but far mesially from the protocristid (as a result of the very long preprotocristid). The absence of a premetacristid leaves the trigonid wide open mesiolingually, as on lower molars of many adapiforms, and as is also the case in *Lazibadapis*.

### 3.2. *Possible deciduous teeth of Algeripithecus minutus and Azibius trerki*

**Studied specimens** UM-HGL50-294, left dP⁴ (Fig. 7A-C); UM-HGL50-295, left dP⁴ (Fig. 7D-F); UM-HGL50-166, right dP⁴ (Fig. 7G-I); UM-HGL50-270, fragment of right dP₄ (broken, mesial part of the trigonid missing; Fig. 7J-M). Dental measurements are reported in Table 1.

**Locality** Glib Zegdou outlier level 50 (HGL50), Gour Lazib Complex, western Algeria (Fig. 1).

**Age** Late early to early middle Eocene (Sudre, 1979; Mahboubi, 1995; Mebrouk and Feist, 1999; Mahboubi et al., 2002; Adaci et al., 2007, 2016; Mebrouk, 2011; Coster et al., 2012; Ravel et al., 2015, 2016).

## Description

Three upper teeth (Fig. 7A-M) are characterized by a remarkably thin enamel layer (observed from X-ray cross-sections). These teeth have sub-triangular crown outlines and are particularly brachydont and bunodont with strong, bulbous main cusps and very minimal development of transverse crests. They are tetra-cusped, including a strong hypocone occupying a position remarkably much more lingual than the protocone. One of the most striking features is the buccal and lingual expansion of the base of their crown, particularly of the flanks of the main cusps, and the virtual absence, if not total absence, of buccal and lingual cingulum development. A pronounced bunodonty, associated with both buccal and lingual expansion of the crown, are specific features of upper molars of the Azibiidae. Given the general dental characteristics mentioned above for these three upper teeth, their molariform appearance, the shape of their crown outline, and considering their size, we suggest that these specimens represent deciduous upper teeth, in particular fourth deciduous premolars (dP⁴) attributable to the Azibiidae.

UM-HGL50-294 (Fig. 7A-C) is almost as long as it is wide, but its occlusal outline is sub-triangular (i.e., its buccal length is greater than its lingual length), a shape that is accentuated
by the presence of a hypocone lobe protruding from the distolingual crown margin. The distal crown margin is straight buccolingually, while the mesial crown margin is oblique, even curved (convex), with the mesiolingual corner being set back distally from the mesiobuccal corner. The paracone, metacone and protocone are of equal size, whereas the hypocone is slightly smaller but almost equal in size to the two conspicuous conules, the paraconule and the metaconule. The buccal styles, parastyle and metastyle, are also present but are much less voluminous and more discreet (the parastyle being slightly larger than the metastyle; Fig. 7A-B). Only the mesial cingulum is present and well-marked. It is oblique and spans a short space between the protocone and the paraconule (Fig. 7A, C). Below the protocone, a lingual cingulum is also present, but it is very faint, appearing as a trace (i.e., non-functional). The conules are positioned somewhat lingually, appearing relatively close to the protocone, and as such distant from the buccal cusps. They are connected to the protocone by very thin, short and very low crests (protocone-paraconule: preprotocrista; protocone-metaconule: very short postprotocrista + very short hypometaconule crista). The paraconule displays a very low, cingulum-like preparaconule crista, which extends mesiobuccally to join the parastyle (Fig. 7A, C). The distal cingulum is not very pronounced, very low and not extensive mesiodistally, running transversely between the hypocone and the metastyle (Fig. 7A). There is neither hypoparacrista nor hypometacrista, and the lingual flanks of the paracone and metacone are free-standing and steep-sided (Fig. 7A, C). The trigon basin remains open mesially and distally. Buccally, it is closed by the moderate development of a postparacrista and a premetacrista, which represent the only shearing crests of the occlusal surface (Fig. 7A-C). A preparacrista and a postmetacrista, both very short, are also present, developed on the sloping mesial flank of the paracone (Fig. 7C) and the sloping distal flank of the metacone (Fig. 7A-B), and connected to the parastyle and metastyle, respectively. All these buccal crests on either side of the paracone and metacone, are aligned on a mesiodistal axis, and form a weak eocrista (weak buccal cutting-edge development). A bunodont dental pattern with strong cusps and conules, buccal and lingual crown expansion (cusp flanks), and the presence of a trace of a lingual cingulum are dental features found on the upper molars of *Algeripithecus minutus* (Fig. 4B). Based on its size and the dental features described above, this dP⁴ can most likely be attributed to *Al. minutus* (see SOM Fig. S6).

UM-HGL50-295 (Fig. 7D-F) and UM-HGL50-166 (Fig. 7G-I) are similar in size and virtually identical in occlusal structure. They may, however, have a slightly different appearance, particularly with regard to their crown outline. However, this distinction is linked to the fact that UM-HGL50-166 is an enamel capsule, which is irregularly damaged over a large part of its base (at the cervix). This makes the buccal margin of the crown of UM-HGL50-166, particularly the flanks of the paracone and metacone, artificially less bulbous and less expansive buccally (more steeply inclined; Fig. 7G-I), due to a fracture and resulting lack of enamel at the base of the crown (Fig. 7G-H). In contrast, the buccal margin of UM-HGL50-295 is complete and undeformed, and is characterized by a strong buccal expansion of the base of the paracone and metacone. There is a deep buccal invagination between the two expansions, generating an ectoflexus (Fig. 7D-E). Basically, regardless of their larger size,
these two upper teeth have an occlusal pattern and a crown outline shape that are very similar to those of the UM-HGL50-294 dP⁴ described above and attributed to *Al. minutus*. They differ in having more pronounced transverse crests, which nevertheless remain very thin and low, in the total absence of a lingual cingulum, and in showing a strongly reduced metaconule. The parastyle also appears slightly larger, whereas the metastyle is practically undifferentiated. The buccal cutting-edge appears somewhat more pronounced, with a slight increase in the development of the shearing crests forming the eocrista, especially the postparacrista and premetacrista, which are stronger. Mesiolingually, the mesial cingulum is better marked and much more extended mesiodistally than on UM-HGL50-294 (Fig. 7A), forming a small fovea on the two teeth (Fig. 7D, G). On UM-HGL50-166 (Fig. 7G, I), the mesial cingulum is slightly longer than on UM-HGL50-295 (Fig. 7D, F), and wraps more around the mesiolingual base of the protocone. On both teeth, and more markedly than on UM-HGL50-294, the protocone displays a short, gently sloping preprotocrista, which extends mesiobuccally, connecting to the lingual base of the paraconule, and a short but higher, distally oriented postprotocrista. The latter ends abruptly at a point distal to the protocone (it does not extend beyond the base of the distal flank of the protocone). On both teeth, the hypocone displays a short, thin, low prehypocrista, which extends mesiobuccally and connects to the distal end of the postprotocrista (Fig. 7D, G). The distal end of the postprotocrista is also the point where a short but well-defined hypometaconule crista (= metacrista or crista obliqua; see SOM Fig. S1) joins the postprotocrista almost perpendicularly. Unlike UM-HGL50-294, on UM-HGL50-166 and -295, there is a thin, short hypometacrista on the lingual flank of the metacone (mostly on its basal part), which connects to the metaconule (Fig. 7D, G). This distal transverse crest, composed of a hypometacrista contiguous with a metaconule and a hypometaconule crista, forms what we call a hypometacrista complex (see SOM Fig. S1). This suite of anatomical details is found in upper molars of azibiids, more especially in *Azibius trerki* (Fig. 4F). On the basis of their size, bunodont dental pattern with strong cusps, reduced metaconule, buccal and lingual crown expansion (cusp flanks), absence of lingual cingulum, and other characters described above, these two dP⁴s can most likely be attributed to *Az. trerki* (see SOM Fig. S6).

Finally, one lower half-tooth (UM-HGL50-270; Fig. 7J–M), whose dimensions are compatible with those of the two deciduous upper premolars described above and attributed to *Az. trerki*, could document a deciduous lower premolar of this taxon. This tooth is very bunodont and has markedly inflated and diverging buccal and lingual crown bases. This is particularly shown in distal view (Fig. 7M). The divergent crown bases are not re-entrant at the cervix, which might suggest that this lower tooth had two diverging distal roots, one extending lingually beyond the lingual edge of the crown, and the other extending buccally beyond the buccal edge of the crown. Although smaller in size and unfortunately broken (a small part of the trigonid is missing; Fig. 7J–L), the shape and occlusal pattern of this tooth are reminiscent of those of the M₁s of *Az. trerki* (Fig. 4E; SOM Fig. S4K). The cristids joining the main cuspid s are less developed, and the cuspid s are more protruding. However, on a mesiodistal axis, the metaconid appears to be less buccally displaced relative to the entoconid
than the condition observed on M₁s of *Az. trerki*. In contrast, the protoconid appears to be
much more shifted lingually, almost mesial (mesiobuccal) to the metaconid. Given the
structural similarity between this tooth and the M₁s of azibiids (Fig. 4A, E, G), UM-HGL50-270
could be identified as a dP₄. Its configuration also illustrates this tendency towards a
mesiodistal alignment of the cuspids. We might then expect the dental pattern of dP₃ in this
taxon to be similar to that of its permanent P₄ and P₃, i.e., with a serrated blade-like
morphology.

3.3. Possible large-bodied primate from Chambi

Studied specimens ONM-CBI-1-02, right M₁ (Fig. 8A–E; figured in Court, 1993, fig. 1 [under the original accession number UM-CBI 02]); ONM-CBI-1-01, left M₂ (worn and corroded; Fig. 8F–J; original accession number UM-CBI 01). Dental measurements are reported in Table 1.

Locality Chambi locus 1 (CBI-1), Djebel Chambi, central-western Tunisia (Fig. 1).

Age Late early to early middle Eocene (Hartenberger et al., 1985, 1997, 2001; Marivaux et al., 2015; Ravel et al., 2015, 2016).

## Description

Only the best-preserved specimen (ONM-CBI-1-02, M₁) was illustrated and described by Court (1993). We provide here new illustrations for this specimen (Fig. 8A–E), as well as for the second specimen (ONM-CBI-1-01; Fig. 8F–J). ONM-CBI-1-02 was adequately described by Court (1993). His description is reproduced below *in extenso* with adaptions to the dental terminology used in this article (SOM Fig. S1). We also add some further details to the description, considering the two specimens.

Adapted from Court (1993, pp. 267): 'UM-CBI 02 (ONM-CBI-1-02) is a somewhat elongated, crestiform lower molar, with the talonid slightly wider than the trigonid. The metaconid is slightly more robust than the protoconid and occupies a more posterior (distal) position; the strong protolophid (protocristid) is therefore obliquely oriented. A paracristid (preprotocristid) descends anteriorly (mesially) for a short distance from the protoconid before turning abruptly lingually to end in a minor swelling below the lingual part of the protoconid; the paraconid is evidently reduced. The hypoconid is set slightly more anteriorly (mesially) than the lingual talonid cusps (cuspidis) and is marginally more buccal in position than the protoconid. A straight cristid obliqua trends anterolingually (mesiolingually) from the hypoconid to contact the posterior (distal) wall of the trigonid just buccal to the metaconid. The entoconid and hypoconulid are fused (twinned), except for a narrow separation near the apices of the cusps (cuspidis). Although both cusps (cuspidis) are of equal height, the hypoconulid is more massive than the entoconid. Moreover, the hypoconulid is posterior (distal) to both the entoconid and hypoconid, and is only very slightly offset buccally from the
entoconid. A postcristid, oriented approximately parallel to the protolophid (protocristid), joins the hypoconid and hypoconulid. Lingually, there is a wide separation between entoconid and metaconid, with no suggestion of either pre-entocristid or postmetacristid. In buccal view [fig. 1B] (Fig. 8C), the protoconid is marginally higher than the hypoconid and both cusps (cuspid s) are slightly canted in a mesial direction. The cristid obliqua descends a little from the hypoconid before rising again to contact the trigonid. A swollen border around the base of the hypoconid extends to the posterior (distal) base of the protoconid, constituting all that remains of a buccal cingulid. In lingual view [fig. 1C] (Fig. 8B), the apical separation between entoconid and hypoconulid is visible; lingual cusps (cuspid s) of both the trigonid and talonid are approximately equal in height and are separated by the deep entoconid notch. A lingual cingulid is absent. In anterior (mesial) view (Fig. 8D), the metaconid is slightly taller than the protoconid and the crest (cristid) joining the two cusps (cuspid s) is shallowly U-shaped. A straight, narrow cingulid occurs below the paracristid (preprotocristid). In posterior (distal) view (Fig. 8E), the fused (twinned) entoconid and hypoconulid are somewhat taller than the hypoconid, and the postcristid declines a little from the hypoconid, giving it a shallow, notched appearance. Finally, a blunt crest (cristid) descends steeply in a posterobuccal (distobuccal) direction from the hypoconulid to merge with the posterobuccal (distobuccal) base of the hypoconid.'

The second specimen (ONM-CBI-1-01), only slightly larger, was not figured by Court (1993) due to its damaged and altered (corroded) state of preservation. We provide here several views (Fig. 8F-I) of the specimen (surface reconstructions of a 3D digital model). This lower tooth is interpreted as M<sub>2</sub> due to the configuration of the cristid obliqua, which does not terminate on the buccal flank of the metaconid (as on the ONM-CBI-1-02 M<sub>1</sub>), but runs up the distal wall of the trigonid, terminating at the top of the protocristid, at a point midway between the protoconid and the metaconid (Fig. 8F, J-H). Except for the orientation of the cristid obliqua, these two lower molars have similar arrangement and development of the cuspid s and cristids. The mesial cingulid of the ONM-CBI-01 M<sub>2</sub> is longer (Fig. 8F, I), extending over almost the entire width of the crown, whereas on ONM-CBI-02 M<sub>1</sub>, it is present only in the mesiobuccal region of the crown (Fig. 8A, D). On both teeth there is no trace of cingulid on the buccal margin of the crowns (but ONM-CBI-01 M<sub>2</sub> is damaged in this buccal region), and the buccal flanks of the protoconid and hypoconid are relatively steep-sided compared to the lingual flanks, which are more swollen and rounded. The absence of a cingulid beneath the hypoflexid results in a shallow invagination of the buccal aspect of the crown. This buccal invagination, combined with a slight lingual invagination, gives the tooth an 8-shaped outline, with a mesiodistal long axis (Fig. 8A, F). The postcristid, connecting the hypoconid to the hypoconulid, is straight, not curved like the distobuccal base of the crown. This change in shape from the base of the crown to the top of the postcristid results in a shallow but clearly visible depression (concavity) on the distobuccal wall of the crown (Fig. 8C, H). The two teeth show no premetacristid development and no lingual paracristid, so the mesial flank of the metaconid is free-standing but gently sloping. In the absence of a connection between the
metaconid and the mesially distant paraconid (lying slightly buccal to the midline of the crown), the trigonid remains wide open mesiolingually.

## Comparisons

At the time of the original description of these two lower teeth, the status of this taxon from Chambi remained as an 'enigmatic mammal' (Court, 1993). This was largely due to the lack of comparative paleontological material from this geological period in Africa in the early 1990s. However, Court (1993) pointed out the possible affinities of this taxon with certain more recent, advanced adapiform primates (the Sivaladapidae known in Asia from the late middle Eocene up to the middle Miocene; for a summary see e.g., Gilbert et al., 2017; Chavasseau et al., 2019), but also with non-primate mammals, notably the early Tertiary Euramerican 'hyopsodontid condylarths' (archaic hoofed mammals). The adapiform hypothesis for the status of this taxon has recently been revived in light of several fossil discoveries subsequent to the Court's work, in particular the recognition of highly specialized caenopithecine adapids in the late Eocene of the Fayum in Egypt (L-41 and BQ-2; e.g., Simons et al., 1995; Simons and Miller, 1997; Godinot, 1998; Seiffert et al., 2009; Seiffert, 2012; Seiffert et al., 2018), as well as in the middle Eocene of Sperrgebiet in Namibia (Black crow; Godinot et al., 2018). However, while it seems to be accepted that this Chambi taxon is related to this group of Adapidae from Africa (e.g., Seiffert, 2012; Godinot et al., 2018; Seiffert et al., 2018), there is actually no published work formally comparing these two molars with those of known caenopithecine taxa from Egypt (*Aframonius dieides*, *Afradapis longicristatus*, and *Masradapis tahai*) and Namibia (*Namadapis interdictus*), for which lower teeth are documented. Here we make this dental comparison, and provide new illustrations for these two specimens (Fig. 8).

Among the morphological features that may seem surprising on these two molars from Chambi is, firstly, the total absence of a buccal cingulid, which is otherwise always present, albeit often very reduced, on the molars of the caenopithecines. This buccal cingulid is often broken at the hypoconid (does not wrap around the buccal base of that cuspid in *Aframonius*, *Afradapis*, *Masradapis*, *Namadapis*, and even *Caenopithecus*), and sometimes at the protoconid (*Masradapis*). However, in all these taxa, the buccal cingulid is always present at the level of the hypoflexid, spanning its entire length and forming a platform at the base of the crown. On both teeth from Chambi, the absence of a cingulid at the base of the buccal flank of the hypoflexid, and the consequent lack of a platform, produces a marked invagination over the entire height of the crown (i.e., buccal flank of the cristid obliqua). The lingual aspect of the crown also exhibits a noticeable invagination (smooth depression) at its base, which can also be seen in some caenopithecines (e.g., *Afradapis*), but to a much lesser extent. These two buccal and lingual depressions result in the distinctive 8-shape occlusal outline of the molars. This peculiar crown outline can also be observed in lower molars of *Mescalerolemur*, an adapiform of uncertain familial affinities (close to *Mahgarita*) from the late middle Eocene of North America (Kirk and Williams, 2011; Godinot, 2015; see also
Seiffert et al., 2018), but this taxon has a less marked buccal invagination of the crowns (due to the presence of a moderately developed cingulid platform at the hypoflexid).

In addition to their unusual crown outline, these two molars from Chambi may also appear somewhat higher crowned compared to the lower molars of the Caenopithecinae (for comparison, see Godinot et al., 2018, fig. 5-6; Seiffert et al., 2018, fig. 6). This is particularly evident in lingual view (especially on the well-preserved ONM-CBI-1-02 M₁; Fig. 8B), where the base of the crown (above the cervix) is distinctly more elevated just before the differentiation of the two conical cuspids, and furthermore, the entoconid-hypoconulid complex is considerably tall, almost as high as the metaconid. This pronounced development in height of the entoconid (associated with the hypoconulid) is atypical, and would be a unique configuration among adapiforms if it turns out that these two teeth represent a species of this group. In contrast, a talonid basin that remains well open lingually (wide U- or V-shaped opening) is typical of the Caenopithecinae, as well as the Adapinae. The two molars from Chambi, however, show no postmetacristid development, a cristid that can be strongly developed, including a cuspidate metastylid (as on the lower molars of *Caenopithecus*, and to a lesser extent in *Aframonius*), or less prominent, less trenchant, gently sloping distolingually (e.g., as in the lower molars of *Afradapis*, *Masradapis*, and *Namadapis*). The presence and strong development (very long and sharp) of a postmetacristid is a particularly recurrent feature on lower molars of the Adapidae (especially in *Cryptadapis*, *Leptadapis*, and *Adapis*). Regarding the most distal cuspid of the talonid, i.e., the hypoconulid, its presence, development and position on M₁-₂ vary greatly in the Adapiformes. It is clear that a large hypoconulid in a distolingual position, very close to or twinned with the entoconid (with many variants), is a condition found only in the Sivaladapidae, as Court (1993) pointed out. A large hypoconulid twinned with the entoconid is also observed in certain anthropoid lineages (Oligopithecidae, Proteopithecidae, and some Eosimiiformes). In the Adapidae, especially within the Adapinae (e.g., certain *Adapis*), a minute hypoconulid-like enamel swelling, can occasionally be observed at the lingual end of the postcristid, positioned either distantly from the entoconid or in close proximity to it. In the Caenopithecinae, a very small hypoconulid (or enamel swelling) can be observed, usually subsumed within the postcristid and positioned in close proximity to the hypoconid (buccal to the crown midline) in *Caenopithecus* and certain *Aframonius* specimens; otherwise, this tubercle is absent on lower molars (M₁-₂) of *Afradapis*, *Masradapis* and *Namadapis*.

On the trigonid of the two molars from Chambi, the development and configuration of the preprotocristid, which descends mesially for a short distance from the protoconid before turning abruptly lingually to end in a minute, buccally displaced paraconid (buccal to the crown midline), is fairly standard for caenopithecines. In stark contrast, the absence of a paracristid on the two lower molars is unusual among caenopithecines, which display a long, straight or slightly curved paracristid, extending lingually and delineating the mesial margin of the trigonid basin. On the two molars, the trigonid basin remains wide open mesiolingually, whereas in caenopithecines, it remains open only lingually. Finally, on the two molars from
Chambi, the presence of a mesial cingulid below the location where a paracristid would normally occur (as in caenopithecines), confers a distinctive characteristic on this taxon.

From all these comparisons, it follows that, contrary to Seiffert (2012), Godinot et al. (2018) and Seiffert et al. (2018), it is not so clear and certain, at least for us, that these two lower molars from Chambi, belonging to a medium-sized taxon, could represent a Caenopithecinae of the same lineage as the primates from Namibia and Egypt. If a possible overall resemblance were to be expressed, it would only be with the molars of *Masradapis* (especially M2; see Seiffert et al., 2018, fig. 5C-E), although a suite of characters differentiates them distinctly (e.g., on ONM-CBI-1-01 and -02, absence of buccal cingulid, presence of mesial cingulid, absence of paracristid and postmetacristid, presence of a strong hypoconulid twinned with the entoconid, and higher crown). It is noteworthy that certain anatomical details (e.g., marked crown height above the cervix, no difference in the elevation of the buccal cuspids with a strong and tall entoconid-hypoconulid complex, absence of buccal cingulid at the hypoflexid, marked buccal and lingual invaginations of the crown, and presence of a mesial cingulid below the location where a paracristid would normally occur) are singular and not even observed in primates of this period, which raises the question as to the formal attribution of this taxon to this order. The new illustrations of these two specimens that we provide here will enable other experts to better appreciate the fine anatomy of these teeth. It is clear that the addition of new dental remains, especially upper molars, but also upper and lower premolars, will provide further clues to elucidate the taxonomic affinities of this taxon. The acid treatment of the indurated sediments of Chambi (CBI-1) and Glib Zegdou (HGL-50) is still in progress, and it is conceivable that further dental material documenting this taxon may be extracted in the near future. The mammalian affinities of this taxon could then be explored more in depth than current data allow.

# 4. Discussion

## 4.1. Primate paleodiversity inputs from the Eocene of Tunisia and Algeria

Over the past 40 years, a number of dental, cranial and post-cranial specimens of primates from the fossil-bearing localities of Djebel Chambi in central-western Tunisia and the Gour Lazib Complex in western Algeria have been presented (e.g., Sudre, 1975, 1979; Godinot and Mahboubi, 1992, 1994; Hartenberger and Marandat, 1992; Tabuce et al., 2004, 2009; Marivaux et al., 2011a, 2013; Benoit et al., 2013). Despite the misidentification of some of these fossils at the time of their initial description and considerable uncertainty about the phylogenetic status of others (largely due to a lack of paleontological and/or comparative material), these taxa have nevertheless contributed to our knowledge of the paleodiversity of early primates from North Africa. Here, we have illustrated and described a set of new fossil specimens (mainly dental remains) that have been extracted more recently from these two
former sites. They substantially expand our knowledge of the diversity of strepsirrhine primates from these two regions of North Africa during the late early to early middle Eocene time window. These two North African regions, which are part of the contemporary Maghreb, are the only locations on the Afro-Arabian plate that have produced a fossil record of mammals for this time interval of the early Cenozoic (e.g., Van Couvering and Delson, 2020). The discovery of a diminutive taxon that could be a basal representative of the Djebelemuridae at Glib Zegdou in Algeria (Lazibadapis anchomomyinopsis gen. et sp. nov.) would extend the geographic distribution of this family at that time, which was so far known only from Tunisia (Chambi). However, this family has proven to be a long-lived lineage over several million years and particularly widespread during the latest Eocene–early Oligocene time interval, from north-western Africa (Atlantic Sahara/Dakhla: cf. 'Anchomomys' milleri; Marivaux et al., 2024) to north-eastern Africa (Fayum, Egypt: 'A.' milleri; Simons, 1997; Seiffert et al., 2005b; Seiffert, 2012) and south-eastern Arabia (Sultana of Oman: Omanodon and Shizarodon; Gheerbrant et al., 1993; Godinot, 2006, 2010; Seiffert, 2012). Likewise, the discovery of additional primate dental material at Chambi led to the formal recognition of a tiny member of the Azibiidae in Tunisia (Algeripithecus minimissimus sp. nov.). In fact, this taxon had long been recognized by several primatologists on the basis of certain specimens from Chambi that had originally been misattributed to *Djebelemur martinezi* (Godinot, 1994, 2006, 2010; Tabuce et al., 2009; Seiffert et al., 2010; Seiffert, 2012; Benoit et al., 2013; Marivaux et al., 2013). The presence of an azibiid in Tunisia also highlights the wider geographic distribution of this group of primates at that time. However, these two geographic occurrences (i.e., western Algeria and central-western Tunisia) are the only references for the presence of the Azibiidae in Africa during the Cenozoic. Unlike djebelemurids, azibiids have so far been absent from more recent deposits in North Africa and sub-Saharan Africa (e.g., Van Couvering and Delson, 2020; see also Marivaux et al., 2024, fig. 8). The Gour Lazib Complex and Djebel Chambi represent only two snapshots in the evolutionary history of the Azibiidae, and thus do not provide any evidence of their geographical or temporal extent. Despite their limited fossil record, azibiids nevertheless appear to have been a flourishing group in the late early to early middle Eocene, as evidenced by their remarkable diversity, at least in North Africa. The diversity of the Azibiidae is primarily reflected in a wide range of body sizes, as exemplified by the two new taxa described here, *Azibius magnus* sp. nov. from Glib Zegdou (BM = ~ 760 g; i.e., the largest known species) and *Algeripithecus minimissimus* sp. nov. from Chambi (BM = ~ 62 g; i.e., the smallest known species), and including intermediate sizes with *Azibius trerki* (BM = ~ 245 g) and *Algeripithecus minutus* (BM = ~ 145 g), both from the Gour Lazib Complex. Concerning the other coeval strepsirrhines, if *Lazibadapis anchomomyinopsis* gen. et sp. nov. from Glib Zegdou turns out to be a djebelemurid, then it would be one of the smallest representatives of this family, with a BM estimate of ~ 100 g, *contra* ~ 135 g for *Djebelemur martinezi* from Chambi (SOM Table S2). It should be noted that these BM estimates, based here on the equations of Egi et al. (2004) for several molar loci, are higher than those calculated by Tabuce et al. (2009) for *Az. trerki* (115 to 160 g) and *Al. minutus* (65 to 85 g), or Marivaux et al. (2013) for *D. martinezi* (70 g) using the equations of Conroy (1987)
and Bajpai et al. (2008), based on the area of M₁ only (using ‘all-primates’ and ‘prosimian’ least-squares bivariate regression equations).

## 4.2. Origin(s), paleobiogeography and fate of the earliest strepsirrhine primates of the Arabo-African continent

At the time of their original description, the very limited and fragmentary state of the fossils, essentially dental, documenting *Azibius trerki* (Sudre, 1975, 1979) and *Algeripithecus minutus* (Godinot and Mahboubi, 1992, 1994), both from the Gour Lazib Complex, led to the proposal of phylogenetic affinities for the two taxa (for a summary, see the introduction of this paper), which proved to be erroneous in the light of the more abundant paleontological material collected in recent decades. A number of dental, cranial and post-cranial features (Tabuce et al., 2009; Marivaux et al., 2011a; Benoit et al., 2013) revealed their strepsirrhine status and, besides, their close relationship, uniting them in a full-fledged family: the Azibiidae (Gingerich, 1976 *sensu* Tabuce et al., 2009). Likewise, *Djebelemur martinezi* from Chambi (Hartenberger and Marandat, 1992), as well as more recent taxa such as '*Anchomomys*' *milleri* from the latest Eocene of Egypt (Simons, 1997), *Omanodon minor* and *Shizarodon dhofarensis* from the early Oligocene of Oman (Gheerbrant et al., 1993), were considered as cercamoniine adapiforms in their original description because of their anchomomyin-like molar features. All of these taxa are now considered to be allied, forming the family Djebelemuridae (Seiffert et al., 2003, 2005b; 2018; Godinot, 2006, 2010, 2015; Seiffert, 2012; Marivaux et al., 2013, 2024). Together with the Azibiidae, they are referred to as ‘advanced’ stem strepsirrhines, i.e., more closely related to the crown Strepsirrhini (tooth-combed primates) than any Adapiformes (other stem strepsirrhines, lacking a tooth-comb; e.g., Godinot, 2006, 2015; Tabuce et al., 2009; Marivaux et al., 2013). Djebelemuridae and Azibiidae share a number of lower molar characteristics that make them closely related to extinct and extant tooth-combed strepsirrhines. It is clear, however, that the Azibiidae, with their peculiar, somewhat odd transformation of their premolars (see below), represent a highly specialized group that was already very divergent from the coexisting Djebelemuridae. Among djebelemurids, only *Djebelemur* and '*A.' milleri* are documented by almost complete lower jaws, which illustrate premolar and canine conditions derived ‘towards’ a crown strepsirrhine-like adaptation (i.e., pre-tooth-comb). Whether Djebelemuridae or Azibiidae, their lower front teeth (ante-molars) clearly distinguish them from the anchomomyin cercamoniines (Notharctidae, Adapiformes) of Europe. However, the similarities in molar morphology, with only subtle differences, point to affinities and probable relationships, and thus to the plausible phylogenetic origin of the common ancestor of the Djebelemuridae and Azibiidae. The discovery at Glib Zegdou (HGL50) of *Lazibadapis anchomomyinopsis* gen. et sp. nov. is very critical in this respect. The ambiguous morphology of its lower molars, which do not display all the synapomorphies of the Djebelemuridae, but instead follow a more anchomomyin-like pattern, lends further credibility to the hypothesis that the root of the pre-
tooth-combed strepsirrhines – and hence the deep root of the tooth-combed strepsirrhines – is nested within a radiation of anchomomyin adapiforms (Seiffert et al., 2009, 2018; Tabuce et al., 2009; Boyer et al., 2010; Seiffert, 2012; Steiper and Seiffert, 2012; Marivaux et al., 2013; Marigó et al., 2016). *Lazibadapis* gen. nov. seems to be key to this phylogenetic issue. However, we refrain from conducting a cladistic assessment of the available dental evidence in the present study, due to the limited amount of paleontological material assembled to date, the incomplete and poorly preserved nature of some specimens, and the uncertainty in the identification of certain dental loci (particularly for the upper molars). The inclusion of this new taxon in the Djebelemuridae is proposed here on a provisional basis only. As the acid treatment of the indurated sediments from Glib Zegdou HGL-50 is underway, new and more complete fossils may be extracted in the future, in particular upper and lower ante-molar specimens documenting this taxon. These would be of undoubted interest for a more relevant phylogenetic assessment.

Based on our current knowledge of the fossil record of Africa, and a more precise understanding of the taxonomic status of the taxa recognized to date, this continent was clearly the theater of multiple colonizations by primates at the beginning of the Cenozoic. These colonizations involved several distinct phylogenetic clades (polyphyletic colonizations), which likely entered Africa in a temporally staggered fashion. Despite its enigmatic status, *Altiatlasius* from the latest Paleocene of Morocco (Sigé et al., 1990), has the potential to document an early phase in the colonization of Africa by primates. However, the geographic origin of this early phase remains undetermined due to the uncertainty surrounding the phylogenetic affinities of *Altiatlasius* within Primates (see Beard, 2006; Seiffert, 2012). The colonization of the common ancestor of the Djebelemuridae and Azibiidae, whose roots seem to lie in the anchomomyin notharctids of Europe, could represent another phase of colonization via a trans-Tethyan crossing. If these two groups of strepsirrhines do indeed share a common ancestry and differentiated in Africa, given the strong morphological divergence between the Azibiidae and the Djebelemuridae, their common ancestor can be expected to have entered Africa long before their first joint appearance in the fossil record (Djebel Chambi and Gour Lazib Complex), i.e., sometime during the first part of the early Eocene or even earlier. In this paper, we argue that the largest taxon from Chambi ('enigmatic mammal'; Court, 1993), which has been interpreted by some as one of the first representatives of the African caenopithecine adapids (Seiffert, 2012; Godinot et al., 2018; Seiffert et al., 2018), is in fact not a primate; an interpretation that invalidates the presence of an adapid at Chambi. In contrast, the two taxa from the middle Eocene of Namibia (*Namadapis* and *Notnamaia*) provide evidence for the presence of this group of Adapidae in Africa at that time (Godinot et al., 2018). The Caenopithecinae, a distinct group of adapiform strepsirrhines, represent therefore another case of primates colonizing Africa (from Eurasia; Godinot et al., 2018) during this early epoch of the Eocene. These adapid primates then became particularly successful in light of their late Eocene fossil record from northeast Africa (Fayum, Egypt; Simons et al., 1995; Simons and Miller, 1997; Godinot, 1998; Seiffert et al., 2009; Seiffert, 2012; Seiffert et al., 2018). Africa was therefore a major center of
diversification for strepsirrhine primates during most of the early and middle Eocene (e.g., Seiffert, 2012; Marivaux et al., 2013; Godinot et al., 2018). However, much of the evolutionary history of these primates during the middle Eocene remains so far undocumented paleontologically. Yet this time window is of particular significance for the history of primates in Africa, as it is during this period that the arrival of anthropoid primates from Asia is expected (e.g., Jaeger et al., 2010; Chaimanee et al., 2012, 2024; Seiffert, 2012; Marivaux et al., 2014; Beard, 2016). Based on all of the recently acquired paleontological field data and the reinterpretation of certain fossils, it appears now that anthropoid primates were not present on the African continent at the beginning of the Cenozoic (unless *Altiatlasius* turns out to be a basal anthropoid; for a summary, see Seiffert, 2012). Their first appearance in the African fossil record dates back only to the end of the middle Eocene (ca. 39.5 Ma; Marivaux et al., 2014), thereby suggesting a colonization of Africa sometime during the middle Eocene or the late middle Eocene. There is growing evidence that several clades of anthropoids colonized Africa at that time (e.g., Jaeger et al., 2010; Chaimanee et al., 2012, 2024; Marivaux et al., 2014, 2023; Beard, 2016; Jaeger et al., 2019). In any case, the record of anthropoids is remarkably abundant with diversified forms as early as the late Eocene, primarily in North Africa (for a summary, see Seiffert, 2012; Marivaux et al., 2024, fig. 8). From a macroevolutionary perspective, despite the long gap in the Eocene fossil record mentioned above, the Caenopithecinae and Djebelemuridae were clearly long-lived lineages on the Afro-Arabian continent, since some of the representatives of both families are found in the late Eocene (Fayum, Egypt) and also in the early Oligocene for the Djebelemuridae (Oman and Atlantic Sahara). In contrast, the Azibiidae have never been recorded outside of the Gour Lazib Complex and Chambi, i.e., they are exclusively recorded in North Africa and limited to the late early to early middle Eocene. The aforementioned gap in the fossil record for most part of the middle Eocene hinders our ability to trace their evolutionary history and fate. Their somewhat extreme morphological specialization (see below) may have been selectively advantageous for a time, as evidenced by their high diversity recorded in the Gour Lazib Complex plus Chambi, but ultimately resulted in low diversification, leading them into an evolutionary dead end. The absence of the Azibiidae from the fossil-bearing localities of the late middle Eocene (Bartonian) and the late Eocene in North Africa suggest that these primates may have become extinct, although we have no information on a possible widespread paleogeographic distribution for the group, particularly in Sub-Saharan Africa, where no favorable deposits are known. Azibiids are otherwise absent from the fossil record of the middle Eocene of Namibia, which does, however, attest to the presence of caenopithecine adapids. Azibiids may have been supplanted by their close relatives, the early members of the crown Strepsirrhini (tooth-combed primates; Lorisiformes and Lemuriformes), which were already well diversified in North Africa by the end of the Eocene (e.g., Simons and Rasmussen, 1994; Seiffert et al., 2003, 2005b; Seiffert, 2007a; Jaeger et al., 2010; Gunnel et al., 2018). It is also possible that the arrival of the anthropoids in Africa sometime during the middle Eocene, may have contributed to their extinction, as they may have had to face competition for their ecological niche from adaptively similar forms (i.e.,
Asian eosimiiforms and amphipithecid-like taxa). One of the oldest formally recognized basal anthropoids of Africa, but of still unknown origin, *Biretia*, from the early late Eocene of Algeria, Libya and Egypt (e.g., de Bonis et al. 1988; Seiffert et al., 2005a; Jaeger et al., 2010), has upper molars whose occlusal morphology is strikingly reminiscent of the upper molars of azibiids, so much so that it has led to confusion between *Biretia* and *Algeripithecus* in the past (e.g., Tabuce et al., 2001). *Biretia*, a basal representative of the Parapithecoidea (stem anthropoids) may thus have had a dietary ecology close to that of this ancient African strepsirrhine lineage. However, *Biretia* can be distinguished from the Azibiidae by several features on the lower molars and on the upper and lower ante-molar teeth, and otherwise shows no premolar specialization as is the case with the Azibiidae (see below). It is perhaps worth recalling here that *Algeripithecus* was initially identified as an anthropoid on the basis of the morphology of its upper molars (the only data available at the time; Godinot and Mahboubi, 1992). The discovery of paleontological data covering the unsampled Eocene time interval would be crucial in elucidating the factors and constraints that led to the demise of the Azibiidae in Africa. Djebelemurids and caenopithecine adapids have persisted longer than azibiids, and have co-occurred with early anthropoids in addition to early crown strepsirrhines. The environmental changes recorded at the beginning of the Oligocene epoch, resulting from a drastic global climatic cooling event that characterizes the Eocene/Oligocene transition (e.g., Zachos et al., 2008; Bohaty et al., 2012; Tramoy et al., 2016; Westerhold et al., 2020), may have driven these ancient African lineages of stem strepsirrhines (Adapidae and Djebelemuridae) into extinction. Crown strepsirrhines, which may have been more widespread during that period, may have had their latitudinal range constricted to equatorial Africa, which acted as a tropical refugium (e.g., Seiffert, 2007a, b, 2012; Gunnell et al., 2018; Marivaux et al., 2024).

### 4.3. *Paleoecological implications for Azibiidae and Djebelemuridae*

Although their fossil record is very fragmentary, the few cranial and post-cranial remains documenting the Azibiidae and Djebelemuridae indicate that these primates were most likely nocturnal (at least *Azibius trerki* and *Djebelemur martinezi*; Tabuce et al., 2009; Marivaux et al., 2013), and both engaged in a form of generalized, active arboreal quadrupedalism, with some ability to climb and leap (*Algeripithecus minutus*<fnref n="5" /> and *Azibius magnus* sp. nov.<fnref n="6" />; Marivaux et al., 2011a) and frequent horizontal leaping (*Djebelemur martinezi* or *Algeripithecus minimissimus* sp. nov.<fnref n="7" />; Marivaux et al., 2013).

<footnote n="5">⁵ Considering the new BM estimates calculated here, the UM-HGL50-466 talus, initially referred to *Az. trerki* (Marivaux et al., 2011, pp. 453), could be more appropriately attributed to *Al. minutus* due to a better match of estimated BMs.</footnote>

<footnote n="6">⁶ The large UM-HGL50-467 talus has dimensions and an estimated BM (Marivaux et al., 2011) compatible with those of *Az. magnus* sp. nov.</footnote>

<footnote n="7">⁷ Considering the new BM estimates calculated here, the ONM-CBI-1-545 talus, initially referred to *D. martinezi* (Marivaux et al., 2013, pp. 11), could be more appropriately attributed to *Al. minimissimus* sp. nov. due to a</footnote>
One of the most intriguing dental characteristics of the Azibiidae is the peculiar, even exceptional morphological transformation of their upper and lower premolars, a transformation that also affects the lower first molar. The most striking modification is certainly on the lower premolars, which exhibit a very high crown, an almost complete absence of a talonid heel, and a reshaped trigonid with the displacement and alignment along a mesiodistal long axis of the main cuspid, namely the paraconid, protoconid and metaconid. The latter two cuspid are notably strong and tall, resulting in a high-crowned, elongated and serrated blade-like configuration. These lower premolars (P₃-₄) appear relatively large and elongated compared to the molars, particularly the M₁. In all species of Azibiidae, the relatively large size of the premolars substantially (artificially) increases the BM estimates calculated from the surface area of these teeth, compared with the BMs estimated from the molars (see Table 1 and SOM Table S2). A comparable increase in the estimated BMs is also observed for the upper premolars, which likewise display unusual configurations (i.e., high crown, strong buccal cusps and styles that also form a serrated blade-like configuration) in line with those observed for the lower premolars. In addition to the peculiar morphology of the lower premolars, the lower molars show an increase in crown height and a pronounced rising and sharpening of the trigonid from M₃ to M₁. In fact, the protoconid and metaconid become increasingly massive and progressively aligned mesiodistally from M₃ to M₁ (i.e., the protoconid becomes increasingly mesial and central, while the metaconid progressively moves buccally, being almost distal to the protoconid on M₁). This configuration of the molars, especially M₁, is consistent with the adjacent cuspid alignment that characterizes the serrated blade-like pattern of the high-crowned P₄ (and P₃). These unusual configurations are found, with some variation, in the two species of *Algeripithecus* (*Al. minutus* and *Al. minimissimus* sp. nov.) and in *Azibius trerki*, for which sub-complete or composite toothrows are available. For *Azibius magnus* sp. nov., these premolar patterns are only suspected due to the limited documentation of the dental loci, although the only well-preserved M₁ available shows the same cuspid rearrangement trends as the M₁s of other Azibiidae, albeit less pronounced.

Questions then arise as to the function of these highly specialized dental structures and whether they imply a specific dietary ecology for the Azibiidae. The very peculiar serrated blade-like morphology of their third and fourth lower and upper premolars (to a lesser extent in the latter) seems to be suited for shredding and puncturing food. In the case of the molars, the pronounced bunodonty, basins with a reduced surface area and poorly developed shearing crests, give these teeth a crushing rather than a shearing function, and thus a morphology suggestive of fruit and/or gum consumption (e.g., Kay, 1975, 1984; Kay and Covert, 1984; Ramdarshan, 2011; Marivaux et al., 2013). In some small-bodied living strepsirrhines, such as *Euoticus elegantulus* and *Phaner furcifer*, which are specialized gum-eaters (although they also include insects, fruit and nectar in their diet, but to a lesser extent),

<footnote>better match of estimated BMs. However, the talar morphology of ONM-CBI-1-545 differs in some anatomical details from that of the azibiid tali (see Marivaux et al., 2011, 2013), which leaves doubt as to whether this talus is assigned to this diminutive species of *Algeripithecus* recorded at Chambi.</footnote>
modifications of their upper canine and their first upper and lower premolars ($C^1$, $P^2$ and $P_2$; i.e., high-crowned, buccolingually compressed and blade-like configuration) are involved in a forceful acquisition of exudates (e.g., Petter et al., 1975; Charles-Dominique and Petter, 1980; Nash, 1986; Burrows and Nash, 2010a, b; Burrows et al., 2020). Although these are not the same concerned dental loci, in the Azibiidae, the very peculiar serrated blade-like morphology of their third and fourth lower and upper premolars could represent an analogous adaptation for scraping, gnawing, or even 'gouging' into tree and branch bark to acquire hard-to-reach resources, such as exudates (e.g., gums and saps). The marked increase in surface area of the premolars, which also have long and robust roots (e.g., SOM Fig. S2), would further reflect the ability of these teeth to withstand compressive loads during vigorous twisting, prising or gnawing, and flicking away loose tree bark or hardened/dried exudates, to gain access to fresh gums (e.g., Eaglen, 1986; Burrows and Nash, 2010b; Burrows et al., 2020). If this is correct, it would suggest that these primates' feeding behavior often involved turning and rotating their heads sideways to engage the premolars. This highly specialized morphology of the premolars in the Azibiidae, interpreted as a possible adaptation to gum acquisition and thus to exudativory, would then be consistent with the very limited development of the shearing crests and the pronounced bunodonty of their molars (Ramdarshan, 2011; Marivaux et al., 2013). This would indicate a diet consisting mainly of gums and probably fruit, with little or no insects, and no leaves. Another detail, and not the least important, is the configuration of the lower front dentition in *Algeripithecus minutus*, deduced from the dental alveoli preserved on the UM-HGL50-397 dentary bone. This left hemi-mandible preserves $P_3-M_3$ and alveoli for the distal root of $P_2$ and the root of $C_1$ (see SOM Fig. S2). The alveolus of the canine is deep, thin and forwardly inclined, thereby suggesting that the lower canine in this azibiid could have been incisiform/styliform and procumbent (Tabuce et al., 2009, fig. 1d-f). This observation gave rise to the hypothesis that a certain type of functional incisor-canine unit could have existed in *Algeripithecus*, a condition which would have predated the tooth-comb of crown strepsirrhines (Tabuce et al., 2009; Marivaux et al., 2013). In the context of the exudativory considered above, these expected procumbent anterior teeth could have served as a scraping tool to stimulate gum flow (e.g., Martin, 1972; Burrows and Nash, 2010a; Génin et al., 2010). A dental microwear analysis could confirm whether gum consumption could have been a primary source of food for the Azibiidae. However, this type of analysis cannot be carried out because the microwear signal on the enamel of teeth has been erased during the chemical extraction of the fossils. This approach of fossil extraction, although damaging, is the only way to access fossils embedded in a highly indurated limestone matrix.

Among living strepsirrhine primates, most intensive or obligate gum-eaters tend to be small-sized, nocturnal and arboreal species (e.g., Burrows and Nash, 2010a; Burrows et al., 2020). Considering these characteristics, the hypothesis of exudativory, albeit with a somewhat unique dental adaptation for gum harvesting, is thus conceivable for the Azibiidae, especially for the two species of *Algeripithecus* (*Al. minimissimus* sp. nov. and *Al. minutus*) and *Azibius trerki*. Exudativory may have been an important part of their diet, in addition to the probable but smaller parts of frugivory and insectivory (Ramdarshan, 2011; Marivaux et al.,
2013). However, while a trend toward a size reduction in the lower last molar (M₃) has been observed in both intensive and moderate exudativores (Burrows et al., 2020), we do not observe any size reduction in this tooth in the Azibiidae. Among the Azibiidae, the case of *Azibius magnus* sp. nov. should perhaps be considered differently with regard to its possible exudativory. Unlike the other three azibiid species, *Az. magnus* sp. nov. is a larger species, with an estimated BM around 760 g (i.e., well above Kay's threshold of 500 g; Kay, 1975, 1984; Kay and Covert, 1984), thereby suggesting this primate may have incorporated leaves into its diet. The dental material documenting *Az. magnus* sp. nov. is very limited and, in particular, there is no P₄ available, which would have made it possible to observe whether the same morphological adaptations were present as those characterizing the P₄s of its counterparts. The single lower premolar, identified as a P₃ and referred to this species, shows less development of the distal cuspid, but is tall and blade-shaped. The only upper premolar, for which it is difficult to determine the dental locus (P⁴ or P³), shows marked differences from the upper premolars of other Azibiidae, in particular very poorly developed styles (see description and comparisons). As already mentioned above, the only well-preserved M₁ available of *Az. magnus* sp. nov. is bunodont and shows the same, albeit less pronounced, cuspid rearrangement trends as the M₁s of other Azibiidae. The two upper molars available (M² and M³), although heavily corroded, seem to share the same dental pattern as the other species, i.e., strong bunodonty, without any marked development of crests. Due to its larger size and a few distinct dental features (particularly on the premolars), this species probably had a different diet to the other azibiid species. However, molars of *Az. magnus* sp. nov. did not display the highly developed shearing crest pattern that would have been essential to process tough foods. The diet of *Az. magnus* sp. nov. was certainly much more fruit-based than leaf-based. Clarifying its feeding preferences (and those of the other azibiids) would require further material and analyses (i.e., dental topography; e.g., Boyer, 2008; Guy et al., 2013; Winchester et al., 2014; Fulwood et al., 2021; de Vries et al., 2024a, b).

With regard to the other strepsirrhines, the djebelemurid *Djebelemur* from Chambi, and the possible djebelemurid *Lazibadapis* gen. nov. from Glib Zegdou, both exhibit dental patterns characterized by well-developed shearing crests and by pointed, sharp cusps and cuspids. Given their diminutive size (135 g and 100 g, respectively), well below Kay's threshold, the presence of pronounced shearing crests would indicate a diet consisting of insects rather than leaves. However, with respect to *Djebelemur* specifically, as noted by Ramdarshan in Marivaux et al. (2013), this taxon, for which part of the maxillary bone is preserved, displays a relatively larger infraorbital foramen (IOF) than insectivorous taxa of similar size, such as *Tarsius syrichta*, *Galago demidoff*, or *Microcebus murinus*. According to Muchlinski (2008, 2010), if the IOF size can be correlated with certain ecological variables, particularly the diet (i.e., frugivores have significantly larger IOFs than either folivores or insectivores), then the IOF condition that characterizes *Djebelemur* could indicate that this taxon incorporated a significant amount of fruit into its diet. Based on the limited dental and osteological data available for *Djebelemur*, we can hypothesize that this small primate was primarily an insect-eater that most likely supplemented its diet with fruit.
4.4. Paleoenvironmental implications for the Gour Lazib Complex and Chambi

All interpretations of the paleoecology and paleobiology of these primates from the Gour Lazib Complex and Chambi must be considered tentative, given the paucity of fossil specimens. However, despite their incompleteness, these fossils from the Gour Lazib Complex in Algeria and Djebel Chambi in Tunisia provide valuable insights into documenting some aspects of primate diversity in North Africa during the late early to early middle Eocene. Obviously, the fossil species recovered from these two sites represent only a subset of the primate paleodiversity at that time. We may only have access to species that were preferentially preyed upon by selective predators, and thus a substantial component of these primate paleocommunities may be occulted by biased assemblages. Many other mammal species, including primates, that were part of these communities are certainly absent from the fossil record for taphonomic reasons, such as rarity, or because they were not subject to predation. Alternatively, these species may have inhabited areas different or distant from the paleoenvironments in which the Chambi and Glib Zegdou fossil-bearing levels were deposited. Nevertheless, these two localities of North Africa, despite being almost 1,500 km apart from east to west (Fig. 1), yield mammalian communities that, although incomplete, show a high degree of similarity (see SOM Table S1). This similarity in faunal composition has long been an argument for the relative temporal proximity of the two localities (e.g., Hartenberger et al., 2001; Adaci et al., 2007; Coster et al., 2012; Marivaux et al., 2015; Ravel et al., 2015, 2016; Solé et al., 2016). However, the alpha-taxonomic disparities, especially in primates and rodents (SOM Table S1), suggest that the two localities may be temporally staggered (i.e., not strictly contemporaneous) and/or reflect paleoenvironmental conditions that differed at the local scale (i.e., difference in habitats). In the absence of precise radiometric dating at Chambi and Glib Zegdou (and the Gour Lazib Complex in general), a temporal shift cannot be ruled out given the wide time window considered for both localities (i.e., late early Eocene to early middle Eocene). Regardless of a possible temporal difference between these two fossil-bearing localities, the paleoenvironmental conditions of these two regions of North Africa must have been particularly favorable in both cases to have sheltered strepsirrhine primates (Azibiidae and Djebelemuridae) and anomaluroid rodents (Zegdoumyidae). These two groups of tree-dwelling mammals recorded at Chambi and Glib Zegdou (e.g., Marivaux et al., 2011a, b, 2013, 2015, 2017), whose extant close relatives are arboreal and thermophilic species, living today in densely forested tropical environments of equatorial Africa among others (Galagidae and Lorisidae among Strepsirrhini; Anomaluridae and Zenkerellidae among Anomaluroidea; e.g., Nekaris, 2013a, b; Jackson, 2016), would indicate warm, forested paleoenvironmental conditions in these two regions of North Africa by the late early to early middle Eocene. The great diversity of squamates, serpents and lissamphibians recorded at Chambi and Glib Zegdou (SOM Table S1), also indicates warm, moist and vegetated to forested areas, nearby freshwater environments (Rage et al., 2021;
Georgalis et al., 2024; work in progress). The latter point is corroborated, at least in the Gour Lazib Complex, by the abundant charophyte and fish records (e.g., Mebrouk et al., 1997; Mebrouk and Feist, 1999; Adaci et al., 2007, 2016; Mebrouk, 2011), and in both localities by the limestones and/or calcareous sandstones of fluvio-lacustrine to palustrine origin that form the sedimentary matrix of the fossil-bearing levels (e.g., Hartenberger et al., 1997; Adaci et al., 2016). More hypothetically, the presence of a hyperossified ranoid (Rocekophryne) at HGL50 would indicate the existence of seasonality, with possible temporary moderately arid periods (Rage et al., 2021; after Seibert et al., 1974; Trueb, 1993).

## 5. Conclusions

In light of the paleontological data assembled to date, albeit incomplete, the African continent ranks as one of the major centers of primate diversification during the Cenozoic. At the beginning of this era, strepsirrhines clearly flourished during most of the early and middle Eocene, before the arrival of anthropoids. Paleontological data from western Algeria and central-western Tunisia are among the few resources available for understanding the early evolutionary history of primates on this landmass, making them particularly insightful. It now appears that the Azibiidae were a particularly successful but highly specialized group. We hypothesize here that their dental specialization was linked to a specific feeding ecology, likely a mixed diet consisting primarily of exudativory and frugivory. Our understanding of the subtleties of this specialization is certainly superficial, but it seems to have been selectively advantageous for a time, as reflected in the remarkable diversity of the group. However, for reasons that remain unclear, either paleoenvironmental changes or competition with other emerging strepsirrhine groups in Africa (i.e., the tooth-combed primates), or competition with the new-comers (i.e., the anthropoids and/or other mammal groups), their somewhat extreme specialization likely led to low diversification and ultimately extinction (evolutionary dead end). The more insectivorous and perhaps less specialized Djebelemuridae persisted longer, but also became extinct at the beginning of the Oligocene, without leaving any extant relatives. The same is true for the large-bodied caenopithecine adapids, which were specialized folivores that exhibited anthropoid-like adaptations (see Seiffert, 2012). The contingency of intra- and intercontinental dispersals has certainly led to fortuitous contacts between distantly related groups, which may or may not have resulted in biotic interactions (competition or niche sharing). These plausible interactions, combined and/or concomitant with independent, unpredictable climatic and environmental perturbations, have constrained the dynamics of the primate paleodiversity, and shaped the evolutionary history of its distinct subclades in Africa. The emergence and evolution of the strepsirrhines in Africa remain in many ways obscure due to the paucity of the paleontological data, which are still very fragmentary and patchily scattered across this huge continent. Only sustained field efforts, whenever possible, will allow new discoveries to be made, our knowledge to be renewed, and major advances to be achieved on this fascinating subject.
Acknowledgements

We are very grateful to Suzanne Jiquel, Bernard Marandat, Anusha Ramdarshan, Anthony Ravel and Monique Vianey-Liaud (ISE-M, France), Gilles Merzeraud† (Geosciences Montpellier, France), as well as Faouzi M'Nasri (ONM Tunis, Tunisia) for their assistance during one or several field seasons (2008–2012) in the Kassérine region situated in central-western Tunisia. We are grateful to the authorities of Kassérine, and in particular to the staff of the *Direction Générale des Forêts*, for allowing us access to the *Parc National de Chambi*. We are indebted to Mustapha Ben Haj Ali (former Head of the *Service Géologique*, ONM, Tunis) for his support and enthusiasm for our paleontological project in Tunisia. The Vice-Chancellor of the *Université de Tlemcen* (Algeria) and the authorities of the Béchar and Tindouf districts (Algeria) have facilitated field expeditions in the Gour Lazib area of the Sahara of western Algeria. We would like to thank the border guards (*groupement des gardes-frontières*, GGF 113 Zegdou) of the Algerian *Gendarmerie nationale*, who ensured our safety during the field campaigns in the Gour Lazib region. We are very thankful to many colleagues of French paleontological institutions for their help during the successive fieldtrips at Glib Zegdou (2004–2011): Pierre-Henri Fabre (ISE-M, France), Emmanuel Fara (Biogéosciences Dijon, France), Helder Gomes-Rodrigues (MNHN Paris, France), Lionel Hautier (ISE-M), Jean-Jacques Jaeger (PALEVOPRIM Poitiers, France), Vincent Lazzari (PALEVOPRIM), Renaud Lebrun (ISE-M), Stéphane Peigné† (MNHN), Anthony Ravel (ISE-M), Cornelis Schipper (La Fouillade, France), and Xavier Valentin (PALEVOPRIM). Special thanks to Hadj Belkheiri (El-Bayadh, Algeria), Messrs. Yahyaoui and Boudi (Béchar, Algeria), Abdelkrim Benmaamar† (*Université de Tlemcen*, Algeria), and Abdessamed Mahboubi (*Université d'Oran*, Algeria) for their much-appreciated support, comfort and hospitality in the field in Algeria at the 'gateway' to the 'Grand Sud'. Our gratitude also goes to the local people of Tunisia and Algeria for their great generosity and help in facilitating our work in the field. Many thanks to Jean-Louis Hartenberger (ISE-M), who offered us many documents and discussions about the fossil-bearing locality of Chambi. We are indebted to René Lavocat† and Jean Sudre (ISE-M), who provided us with much advice, discussion and memories of the Gour Lazib region. Anusha Ramdarshan is gratefully acknowledged for having analyzed some of the fossils presented in this article for palaeoecological (diet reconstruction) purposes during her PhD (2008–2011; ISE-M). We warmly thank Virgile Merzeraud (Lycée Georges Clemenceau Montpellier, France) for some of the micro-CT scan data processing, reconstructions and illustrations. We would also like to thank Killian Gernelle (ISE-M) for his much-appreciated advice and assistance to V. Merzeraud. Laurent Marivaux extends its deepest thanks to Marc Godinot (MNHN) for his insightful opinion and for sharing original data. We thank the two anonymous reviewers, as well as the editorial board of the journal, for their remarks and suggestions, which enhanced the revised version of the manuscript. Finally, we would like to express our gratitude to Nicole Pasteur (ISE-M) for giving us access to the 4WD vehicles (Land Rover Defender 90 and 110) of the *Institut Français de Recherche* (IFR-119, Montpellier-Environnement-Biodiversité), which
have enabled us to carry out all our field trips to North Africa from France over the years. The Montpellier RIO Imaging (MRI, France) and the LabEx CeMEB have provided access to the µCT-scanning station EasyTom 150/Rx Solutions (ISE-M). Fieldwork and fossil extraction were supported and performed in the framework of the ANR-ERC PALASIAFRICA (ANR-08-JCJC-0017; 2008-2013). They also benefited from funding via the CNRS-Eclipse program (2004-2006), the ISE-M UMR 5554 (2007), a PICS-CNRS program (2007-2009), and the CS-UM2 (2008). This is ISE-M publication n° 2025-111 SUD.

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