# New Pipimorphs from the Late Cretaceous of Niger

Alfred Lemierre, Salvador Bailon, Annelise Folie, Michel Laurin

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Alfred Lemierre, Salvador Bailon, Annelise Folie, Michel Laurin. New Pipimorphs from the Late Cretaceous of Niger. Annales de Paléontologie, 2025, 10.1016/j.annpal.2024.102751. hal-05018914

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New Pipimorphs from the Late Cretaceous of Niger

Nouveaux pipimorphes du Crétacé supérieur du Niger

Alfred Lemierre,ª, *, Salvador Bailonᵇ, Annelise Folieᶜ, Michel Laurinᵈ

ªRoyal Tyrrell Museum of Palaeontology, Box 7500 Drumheller, Alberta, Canada, T0J 0Y0;
alfred.lemierre@gov.ab.ca

ᵇDépartement Homme & Environnement, Muséum national d'Histoire naturelle, UMR 7194
HNHP and UMR 7209 AASPE, MNHN-CNRS, 43 rue Buffon, Paris, 75005, France

ᶜScientific Survey of Heritage, Royal Belgian Institute of Natural Sciences, 29 Vautier Street,
1000 Brussels, Belgium

ᵈCR2P- Centre de recherche en Paléontologie-Paris, CNRS/MNHN/Sorbonne Université,
Bâtiment de Géologie, 43 rue Buffon, Paris, 75005, France

<footnote>* Corresponding author at: Royal Tyrrell Museum of Palaeontology, Box 7500 Drumheller, Alberta, Canada, T0J 0Y0.</footnote>
ABSTRACT

In Becetèn, in southeast Niger, is one of the few mid-Upper Cretaceous (Coniacian-
Santonian) fossiliferous localities in Africa where multiple anuran taxa are known. Two of
them, *Pachycentrata taqueti* and *Inbecetenanura ragei*, have been described from In Becetèn.
Both are pipids, a clade composed of exclusively aquatic anurans. Beside these two pipids,
numerous isolated bones have also been referred to anurans within the site, but never referred
to any known less inclusive taxa. Here we describe several identified cranial and postcranial
bones referable to Pipidae or its stem-group, which together constitute Pipimorpha. Among
these elements, three cranial elements are referred to two unnamed pipimorphs. One of these
has gondwanomorph affinities (pipids + South-American and African extinct pipimorphs).

These conclusions are supported by our phylogenetic analyses. Numerous postcranial
elements are not referable to any of the four pipimorph taxa identified at In Becetèn, although
some ilia might be tentatively referred to ?*Pachycentrata* sp. The presence of at least four
distinct anuran taxa makes In Becetèn the most diverse anuran site in Mesozoic Africa. It is
also the first site in the Mesozoic where four pipimorph taxa are identified. The dominance of
pipimorphs in the anuran diversity of the site suggests that In Becetèn was likely more
lacustrine than previously thought.

Keywords: Anura, Pipidae, Cretaceous, Africa, Phylogeny
## RESUME

In Becetèn, dans le Sud-Est du Niger, est une des rares localités fossilifères du Crétacé supérieur (Coniacien-Santonien) africain où plusieurs taxons d'anoures sont connus. Deux d'entre eux, *Pachycentrata taqueti* et *Inbecetenanura ragei*, ont été formellement décrits d'après des spécimens provenant d'In Becetèn. Ces derniers sont rattachés aux pipidés, un clade d'anoures exclusivement aquatiques. En plus de ces deux pipidés, de nombreux os isolés ont également été attribués aux anoures, mais n'ont jamais été attribués à un taxon plus précis. Nous décrivons ici des éléments crâniens et postcrâniens attribuables au taxon Pipidae ou à son groupe-total, qui ensemble forment le taxon des Pipimorpha. Parmi ces éléments, trois éléments crâniens sont attribués à deux nouveaux pipimorphes que nous ne désignons que par des noms informels. L'un deux a des affinités avec les gondwanomorphes (pipidés + pipimorphes éteints sud-américains et africains). Ces conclusions sont supportés par nos analyses phylogénétiques. De nombreux éléments postcrâniens ne peuvent être attribués à l'un des quatre taxons de pipimorphes identifiés à In Becetèn, bien que certains ilions soient provisoirement attribués à *?Pachycentrata* sp. La présence d'au moins quatre taxons d'anoures distincts fait d'In Becetèn le site le plus diversifié pour ce taxon dans le Mésozoïque africain. C'est également le premier site Mésozoïque où quatre pipimorphes sont identifiés. Cette domination des pipimorphes dans la diversité des anoures suggère que le paléoenvironnement d'In Becetèn était plus lacustre que précédemment proposé.

*Mots-clés* : Anoures, Pipidés, Afrique, Crétacé, Phylogénie.
# 1. Introduction

Pipidae are a clade composed of exclusively aquatic anurans. This particularity and the osteological characteristics linked to this lifestyle have made fossils of this clade more easily identifiable than other anurans in Africa (Gardner and Rage, 2016). As such, pipimorphs (a larger clade that includes pipids) possess one of the most extensive fossil records of all anurans in Gondwana. Their oldest representative, *Aygroua anoualensis*, is known in the Late Jurassic-Early Cretaceous of Northern Africa (Lasseron et al., 2020). Pipimorphs are also known during the Cretaceous throughout Europe, South America and Africa (Lemierre et al., 2023 and included references). The geologically oldest taxa attributed to its crown-clade Pipidae were found in the earliest Late Cretaceous of Africa (Rage and Dutheil, 2008; Lemierre et al., 2023). These taxa are *Oumtkoutia anae*, *Pachycentrata taqueti* and *Inbecetenanura ragei*. Among them, two taxa, *P. taqueti* and *I. ragei*, were described from the site of In Becetèn (Niger), one of the most diverse Mesozoic sites for anurans and pipimorphs in Africa (Gardner and Rage, 2016). *P. taqueti* was identified (but not named) as a strange pipid in a preliminary study (Broin et al., 1974), subsequently redescribed and named as *Pachybatrachus taqueti* by Báez and Rage (1998), and finally, the replacement name *Pachycentrata taqueti* was proposed by Báez and Rage (2004). This taxon is now known by several braincases and vertebral elements. *Inbecetenanura ragei* was recently described (Lemierre et al., 2023) based on a braincase and vertebral elements. Phylogenetic analyses placed the latter and *P. taqueti* within Pipidae, making In Becetèn the oldest co-occurrence of at least two pipid taxa in a given locality.

As part of an ongoing study on the anurans of In Becetèn, we here describe two new, unnamed, pipimorph taxa, based on cranial and vertebral elements. We also include these new taxa in phylogenetic analyses of pipimorph taxa to test their affinities with Pipidae and we add a brief description of cranial and postcranial elements (angulars, centra, scapulae, humeri, ilia,
femora and tibiofibulae) assigned to two unnamed pipimorphs. Finally, we discuss the implications of identifying at least four pipimorph taxa for the anuran diversity as well as the paleoenvironment of In Becetèn.

**2. Geological Context**

All specimens came from the site of In Becetèn (also known as In Becetem, In Beceten, In'Betetén, In Béceten, Ibesseten and erroneously Ibeceten; pers. com. D. Dutheil, Dec. 2021), and were collected during three field trips in 1970, 1972 and 1973, organized by the Muséum national d'Histoire naturelle de Paris (France), led by P. Taquet and D. Russell (Broin et al., 1974). The site is located in southwestern Niger (Lemierre et al., 2023: fig. 1) and has been dated to the Coniacian-Santonian (see Lemierre et al., 2023 for more information).

**3. Material and Methods**

**3.1. Institutional abbreviations**

**MNHN**: Muséum national d'Histoire naturelle, Paris, France. All specimens are stored within the Paleontological collection of the MNHN of Paris (France) in the Amphibians and Reptiles section, under the collection number MNHN.F.IBC.

**3.2. Terminology and comparisons**
The anatomical terminology used herein is based on Roček (1980) and Biton et al. (2016) for cranial features, Sanchíz (1998) for postcranial features and Gómez and Turazzini (2016) for ilial features. Anatomical comparisons are made with 3D models of extant pipids, as well as with several extinct pipimorphs, based on direct observation on fossil specimens when possible (see Table S1).

### 3.3. Phylogenetic analysis

Our data matrix (Appendix S1) includes 44 taxa and 176 osteological characters and is derived from that of Lemierre et al. (2023). A phylogenetic analysis performed by Carvalho et al (2019) included the new taxon *Cratopipa novaolindensis*. Later, Baez et al. (2019) redescribed the specimen and performed a new phylogenetic analysis. That updated dataset was incorporated into Lemierre et al.’s (2023) phylogenetic analyses. We here add the two new unnamed pipimorphs described below to the dataset. The analysis was performed using TNT v.1.5 (Goloboff and Catalano, 2016) under equal weights. All analyses were conducted with cline characters ordered (characters 18, 32, 33, 36, 38, 39, 59, 74, 82, 97, 98, 120, 141, 149), for reasons explained by Rineau et al. (2015; 2018). The analysis consisted of heuristic searches with 1000 random addition sequences of taxa, followed by tree bisection reconnection (TBR) branch swapping, holding 10 trees in each sequence. The final trees were rooted on *Ascaphus truei* (Ascaphidae), and when more than one most parsimonious tree was found, a strict consensus was obtained.

## 4. Systematic Paleontology

Anura Duméril, 1805
Pipoidea Ford and Cannatella, 1993

Pipimorpha Ford and Cannatella, 1993

**Unnamed pipimorph 1**

**Referred material.** One right prooticooccipital (MNHN.F.IBC 1626) and one atlantal complex (MNHN.F.IBC 1968).

**Description.** Prooticooccipital: Only the right prooticoccipital (MNHN.F.IBC 1626) is preserved (Fig. 1A-J). There is no lateral extension of the crista parotica. The dorsal surface is smooth (Fig. 1A). On the posterior margin of the dorsal surface, a small shallow groove opens into the foramen for the arteria occipitalis (Fig. 1A, B). In ventral view, the Eustachian canal is narrow posteromedially and widens anterolaterally (Fig. 1C, D). The otic capsule is large but not expanded ventrally, forming a faint ventral bulge (Fig. 1C, I).

In posterior view, the occipital condyle is crescentic and located ventrolateral to the foramen magnum (Fig. 1F). Lateral to the occipital condyle, the condyloid fossa is circular and is half the dorso-ventral height of the occipital condyle (Fig. 1E-F). The jugular foramen (medial foramen in the condyloid fossa) is larger than the inferior perilymphatic foramen (lateral foramen in the condyloid fossa) and opens posteromedially (Fig. 1E, F). Dorsal to the condyloid fossa, a small superior perilymphatic foramen is visible (Fig. 1E, F). In lateral view (Fig. 1G, H), the fenestra ovalis is located very anteriorly on the otic capsule, at the level of the Eustachian canal (Fig. 1G, H). The fenestra is small and circular. Two small foramina-like openings are visible dorsal to the fenestra ovalis (Fig. 1G, H). They all represent part of the semi-circular canals that are exposed and visible due to breakage of the external surface of the bone. Another small opening, located anterior to the fenestra ovalis, is visible and is here interpreted as the jugular foramen (Fig. 1G, H). Although partially infilled with matrix, this small opening
connects to a large and deep fossa within the braincase (see below). Due to its position, we
interpret this opening as the hyomandibular nerve foramen (cranial nerve VII). In medial view
(Fig. 1I, J), the jugular foramen opens as the posteriormost foramen. Midlength of the medial
wall of the cavum cranii, the paired acoustic foramina open as two separated small openings.
Dorsal to the foramina, the endolymphatic foramen is small and circular (Fig. 1J). On the
anterior region of the medial wall of the cavum cranii, a large fossa is preserved (Fig. 1I). It
opens extracranially on the lateral surface of the prooticoccipital (Fig. 1G, I). This fossa
probably housed the Gasserian ganglion (= trigeminofacial ganglion).

Atlantal complex: MNHN.F.IBC 1968 is a complete atlantal complex (vertebrae I + II) compressed dorsoventrally (Fig. 1K-N). It bears a posterior cotyle, indicating an opisthocoelous condition for the vertebrae. Its centrum is wider than long (Fig. 1M) and the vertebral canal is large and circular (Fig. 1K, L). The paired occipital cotyles are dorsoventrally shallow, crescentic and located ventrolateral to the vertebral canal (Fig. 1K). A thin lip of bone separates the two articular surfaces, a configuration that corresponds to the Type II of Lynch (1971; occipital cotyles confluent but forming two distinct articular facets). The posterior cotyle is small and oval (compressed dorsoventrally, Fig. 1L). There is no neural spine. The posterior half of the dorsal surface of the neural arch bears ornamentation in the form of irregular ridges slightly projecting posteriorly, and thus making this atlantal complex imbricated (Fig. 1M). In lateral view, a large spinal foramen (filled with sediment) is visible below the broken base a slightly cylindrical transverse process (Fig. 1N).

**Discussion.** MNHN.F.IBC 1626 can be differentiated from the braincase of *Pachycentrata taqueti* (Baez and Rage, 1998: fig. 1H-K) in (i) lacking pachyosteosclerosis, (ii) lacking dorsal and ventral ornamentation, (iii) lacking a lateral expansion of the crista parotica and (iv) having the fenestra ovalis opening more anteriorly. It cannot be attributed to a juvenile of *Pachycentrata*, because all braincases of the latter taxon, even those smaller than
MNHN.F.IBC 1626, display dorsal ornamentation (Báez and Rage, 1998, which suggests that the ornamentation is not exostosis, sensu Georgalis et al. 2023). It can also be differentiated from the braincase of *Inbecetenanura ragei* in (i) lacking a lateral expansion of the crista parotica, (ii) having crescentic occipital condyles (ovoid in *I. ragei*) and (iii) having occipital condyles ventrolateral to the foramen magnum (ventral in *I. ragei*).

MNHN.F.IBC 1968 can be distinguished from atlantal complexes of *Pachycentrata taqueti* in (i) lacking a neural spine, (ii) lacking pachyosteosclerosis, (iii) dorsally bearing ridges rather than vermicular ornamentation and (iv) having more confluent occipital cotyles. MNHN.F.IBC 1968 can also be differentiated from the atlantal complex of *Inbecetenanura ragei* in having a crescentic occipital cotyle (likely ovoid in *I. ragei* as inferred by the occipital condyles of its braincase; Lemierre et al., 2023). However, the atlantal complex (MNHN.F.IBC 1968) and the braincase (MNHN.F.IBC 1626) share (i) crescentic occipital condyle/cotyles and (ii) occipital condyle/cotyles ventrolaterally placed to the foramen magnum. Both the braincase MNHN.F.IBC 1968 and the atlantal complex MNHN.F.IBC 1626 are therefore here attributed to the same taxon, an unnamed pipimorph also characterized by (i) the absence of a posterolateral expansion of the parasphenoid (as indicated by Eustachian canals visible in ventral view) and (ii) the presence of opisthocoelous vertebrae (all synapomorphies of Pipimorpha; Gómez, 2016; Lemierre et al., 2023). Unfortunately, the known material is too fragmentary to erect a new taxon; hence, it will be referred to as "Unnamed pipimorph 1". Nevertheless, it represents a third pipimorph taxon in In Becetèn that could be named in the future if more complete material is discovered.

?Gondwanomorpha Lemierre, Bailon, Folie and Laurin, 2023

Unnamed pipimorph 2
**Referred material.** One right prooticoccipital (MNHN.F.IBC 2075).

**Description.** The prooticoccipital is almost fully preserved, with the otic capsule broken (leaving a large ventral opening, Fig. 2). The dorsal surface of the prooticoccipital bears shallow dorsal ornamentation on its medial region composed of narrow and dispersed grooves (Fig. 2A-B). There is no lateral expansion of the crista parotica. In ventral view, the Eustachian canal forms a narrow groove along the anterior margin of the otic capsule, before widening posteromedially (Fig. 2C-D). A foramen of unknown homology pierces the Eustachian canal midway along its length (Fig. 2C-D). The otic capsule is broken, but all fragments have been collected and glued back together. It is large and forms an expanded ventral bulge. The occipital condyle is broken off (Fig. 2E and F), but judging by its preserved base, it was likely crescentic in posterior view. There is no superior perilymphatic foramen. In medial view (Fig. 2G, H), the jugular foramen opens as the posteriormost foramen. Midway along the horizontal length of the medial wall of the cavum cranii, the fused acoustic foramina open as the largest opening. Dorsal to this opening, the endolymphatic foramen is small and circular. On the anterior region of the medial wall of the cavum cranii, a large fossa is preserved. It opens extracranially on the lateral surface of the prooticoccipital (Fig. 2I, J). This fossa probably housed the Gasserian ganglion (= trigeminofacial ganglion).

A small foramen opens within the cavum cranii anteriorly. The foramen is compressed anteroposteriorly (Fig. 2I-J). Due to its position, it is interpreted as a prootic foramen. On the lateral surface of the prooticoccipital, a small foramen and a groove for the hyomandibular ramus of nerve VII are preserved (Fig. 2K-L). Although broken, remnants of the foramen ovale show that it was located on the anterior part of the crista parotica.
**Discussion.** This unique specimen can be differentiated from the braincase of *Pachycentrata taqueti* in lacking (i) pachyosteosclerosis (giving a thickened and bloated aspect of the braincase; Báez and Rage, 1998: fig. 1), (ii) ventral ornamentation and (iii) a superior perilymphatic foramen. It can also be differentiated from the braincase of *Inbecetenanura ragei* in (i) lacking a lateral expansion of the crista parotica, (ii) probably having crescentic occipital condyles (ovoid in *I. ragei*), (iii) having shallow ornamentation on the dorsal surface of the prooticoccipital and (iv) having a foramen of unknown homology piercing the Eustachian canal.

Finally, this braincase (MNHN.F.IBC 2075) is similar to the unnamed pipimorph 1 mentioned above in having (i) crescentic occipital condyles and (ii) an inferior perilymphatic foramen lateral to the jugular foramen. However, it can be differentiated from the latter taxon in (i) lacking a superior perilymphatic foramen; (ii) having shallow ornamentation on the dorsal surface of the prooticoccipital, (iii) having lateral occipital condyles (ventrolateral in Pipimorpha indet. 1) and (iv) having a foramen of unknown homology piercing the Eustachian canal. Except for the ornamentation, these differences cannot be linked to sexual dimorphism or ontogeny.

In summary, this braincase (MNHN.F.IBC 2075) can be differentiated from all three other known pipimorph taxa from In Becetèn. It can be referred to Pipimorpha by lacking a posteromedial expansion of the parasphenoid (as indicated by the Eustachian canal visible in ventral view; Gómez, 2016; Lemierre et al., 2023). Unfortunately, as for Unnamed pipimorph 1, the known material is too fragmentary to propose a new name; hence, it is here referred to as "unnamed pipimorph 2", and represent a fourth, albeit unnamed, pipimorph taxon.

**Pipimorpha indet.**
Numerous fragmentary bones from pipimorphs also were identified at In Becetèn. It was
not possible to attribute the bones to any of the four known taxa, or to another distinct taxon.
They are nevertheless here briefly described as Pipimorpha indet.

**Referred material.** Two angulars (MNHN.F.IBC 1631, 1964); 14 centra (MNHN.F.IBC 1997a-n); three scapulae (MNHN.F.IBC 1632, 1633 and 1974); 21 humeri (MNHN.F. IBC 1651-1655, 1977-1981); 51 ilia (MNHN.F.IBC 1635-1649, 1975; several ilia have been assigned the same collection number); four femora (MNHN.F.IBC 2000a-d); and six tibiofibulae (MNHN.F.IBC 2001a-f).

**Description.** Angulars: The two angulars both represent the posterior region of the bone. The processus coronoideus is large and extends into a flange (Fig. 3A-B; diagnostic for Pipimorpha; Gómez, 2016). The sulcus pro cartilagine Meckeli is closed posteriorly (Fig. 3A-B).

**Centra:** All centra are opisthocoelous. They are elongate anteroposteriorly (Fig. 3C). No bony accretion is present, so they cannot be attributed to *Pachycentrata* and presacral centra (excluding atlantal complexes) are unknown for *Inbecetenanura* and for the third and fourth unnamed pipimorph taxa described above.

**Scapulae:** All three scapulae possess a similar gross morphology and likely belong to the same taxon. One of them (MNHN.F.IBC 1632) was briefly described but not illustrated by Báez and Rage (1998: 685). Scapulae are short and compressed dorsoventrally (Fig. 3D-E; diagnostic for Pipimorpha; Gómez, 2016). The greatest width (at the articulation with the suprascapular) is estimated to almost two-thirds of the length of the bone (Fig. 3D-F). The margo anterior is slightly concave in MNHN.F.IBC 1974, whereas it is straight in the others and bears a large crista anterior (Fig. 3E). The margo posterior is concave. A small articular facet is present on the margo anterior, implying that the clavicle was not fused to the scapula,
as previously suggested by Báez and Rage (1998). The processus glenoidalis seems to be
distinct from the pars acromialis (Fig. 3E).

Humeri: Twenty-one humeri have been recovered (MNHN.F.IBC 1651-1655, 1977-1981; some number refer to more than one humerus). All can be attributed to Pipimorpha based on (i) well-developed epicondyli (ulnaris and radialis), (ii) a small eminentia capitata (compared to maximum width of the humerus), (iii) a small crista medialis, (iv) a straight diaphysis and (v) a deep fossa cubitalis ventralis. Two morphotypes of uncertain biological significance (distinct taxa or sexual dimorphism), A and B, can be distinguished at In Becetèn. Humeral morphotype A is represented by ten humeri (MNHN.F.IBC 1651-1654, 1977, 1981). Humeral morphotype B is represented by nine humeri (MNHN.F.IBC 1655, 1979, 1980). Two humeri (MNHN.F.IBC 1978a-b) are poorly preserved and not referred to a morphotype.

Humeral morphotype A: The fossa cubitalis ventralis is ovoid, elongate anteroposteriorly and deep (Fig. 3G). In the best-preserved specimens, the distal end of the crista ventralis (= deltoid crest) is present as a thin sharp ridge (Fig. 3G). The epicondylus ulnaris (= medial epicondyle) protrudes medially at a greater distance from the humeri than the epicondylus radialis (= lateral epicondyle). However, both epicondyli are well developed, giving a symmetrical aspect to some humeri (Fig. 3G). A low crista medialis is present (Fig. 3G-H).

Humeral morphotype B: Humeri of this morphotype present a fossa cubitalis, which is reduced to a shallow groove pressed against the eminentia capitata (Fig. 3I). As in morphotype A, both epicondyles are well developed. However, the epicondylus ulnaris appears larger and more developed than the epicondylus radialis (Fig. 3I-J). It is also larger than the one found in morphotype A. As in morphotype A, the crista medialis is short. No crista lateralis has been identified.
In one specimen, MNHN.F.IBC 1980, which resembles humeri of morphotype B (Fig. 3K), a crista lateralis is present. However, its epicondylus radialis seems smaller than in Morphotype B. Hence the assignment of MNHN.F.IBC 1980 to morphotype B is putative.

Ilia: Fifty-one ilia have been identified as belonging to pipimorphs. This is based on (i) reduction or absence of a ventral acetabular expansion, (ii) the presence of a lateral oblique ridge on the shaft, (iii) the anteroventral portion of the acetabular rim protruding laterally and (iv) a large ilioischiatic junction. Twenty-two ilia can be attributed to two morphotypes. Morphotype A is represented by twenty ilia (MNHN.F.IBC 1635-1647, 1975) and Morphotype B by two ilia (MNHN.F.IBC 1648, 1649).

Ilial morphotype A: The dorsal prominence is small, triangular in lateral and medial views and projects slightly laterally. Its anterior margin is more steeply inclined than its posterior margin (Fig. 3L-M). Several specimens bear a dorsal protuberance that is more ovoid in outline instead of triangular. The medial oblique groove starts from the anterior edge of the dorsal prominence and extends anteriorly and slightly ventrally along the medial surface of the ilium. Ilia assigned to Morphotype A seem to lack a dorsal crest. A lateral oblique ridge is present and extends anteriorly from the acetabular rim (Fig. 3L). The ventral acetabular expansion (pars descendens) is strongly oriented medially, with a minimal exposure in lateral view. The dorsal acetabular expansion (pars ascendens) is indistinct from the dorsal surface (Fig. 3L-N). When preserved (such as on the specimen MNHN.F.IBC 1935, not figured), the ilioischiatic junction is large in posterior view. The interiliac tubercle is poorly preserved but seems ample at least ventrally (Fig. 3O).

Ilial morphotype B: This morphotype differs from morphotype A in (i) lacking a dorsal protuberance (Fig. 3P-Q) and bearing a bell-shaped, or almost rectangular dorsal prominence.

The remaining ilia are too fragmentary to be assigned to either morphotype.
Femora: Four incomplete femora (MNHN.F.IBC 2000a-d) are attributed to Pipidae due to the presence of a ventral crest on their ventral surface (Fig. 3R-S). The ventral crest is low, thin and sharp.

Tibiofibulae: Six incomplete tibiofibulae (MNHN.F.IBC 2001a-f) are attributed to Pipidae based on the presence of a medial and lateral crests on their diaphysis. The crests are shallow but well visible (Fig. 3T).

**Discussion.** Both humeral morphotypes represent common variation of humeri within pipimorphs (Gómez, 2016). Unfortunately, no unequivocal synapomorphies allow attribution of these morphotypes to any of the four pipimorph taxa of In Becetèn. In addition, two small differences between the two morphotypes, namely (1) slightly more developed epicondylus ulnaris and (2) larger size for morphotype B (compared to morphotype A) are often characteristic of sexual dimorphism in anurans (Lynch, 1971; Keeffe and Blackburn, 2020). This raises the possibility that morphotype B represents male humeri, whereas morphotype A represents female humeri. The similar number of humeri of both morphotypes (10 A and 9 B) is consistent with the hypothesis of sexual dimorphism but does not prove it.

Ilial morphotype A is similar to ilia of *Singidella latecostata* (recovered as a sister-taxon to *Pachycentrata taqueti*) and *Pseudohymenochirus* (an extant taxon close to *P. taqueti*) in having a triangular dorsal prominence and an inconspicuous dorsal acetabular expansion (Báez and Harrison, 2005). Among In Becetèn taxa, *P. taqueti* is considered to be closely related to *S. latecostata*, and both are placed as stem-Hymenochirini in most phylogenetic analyses (Báez and Harrison, 2005; Gómez, 2016; Lemierre et al., 2023). In addition, the frequency of ilia of morphotype A (90% of recovered pipid ilia) suggests that it might belong to the dominant pipimorph taxon. Thus, we could refer this morphotype to *Pachycentrata taqueti*. However, this attribution is very putative, and we refrain from using these specimens for phylogenetic analyses until their affinities are better established. Ilial morphotype B slightly resembles the
ilia of the pipimorph *Kuruleufenia xenopoides* (Gómez, 2016: fig.4L-N) in having a rather tall bell-shaped dorsal prominence. Contrary to the humerus, no sexual dimorphism is known for the ilium of anurans (Gómez and Turazzini, 2016). In any case, the great difference in number of elements (20 A and 2 B) makes the hypothesis that these two morphs represent sexual dimorphism of a single taxon very unlikely.

**5. Phylogenetic Analysis**

A phylogenetic analysis performed under equal weight and cline characters ordered yielded 1343 MPTs with a score of 661 steps. The strict consensus (CI = 0.244 RI = 0.469; Fig. 4A) includes a large pipimorph polytomy that confirms *Aygroua* as the sister-taxon to all pipimorphs (Fig. 4A). The delimitation of Pipidae is unclear because its taxa form a large polytomy. Unnamed pipimorphs 1 and 2 are both recovered within this polytomy (Fig. 4A). This large polytomy likely results from the few scored characters for both unnamed pipimorphs 1 and 2 (see Appendix S1). Interestingly, in the majority consensus, unnamed pipimorph 2 is recovered within Gondwanomorpha (clade composed of Pipidae + Shelaniinae, and as such, composed of African and South American taxa) in 63% of all MPTs (Fig. 4B), whereas unnamed pipimorph 1 is recovered in an unresolved polytomy with the Gondwanomorpha, *Vulcanobatrachus mandelai* and *Avitabatrachus uliana*.

**6. Discussion**

**6.1. Phylogenetic analyses**
The phylogenetic position of *Pachycentrata taqueti* and *Inbecetenanura ragei* within Pipidae (albeit the composition of Pipidae is unclear, due to the poor resolution of the strict consensus tree, partly caused by the uncertain position of unnamed pipimorphs 1 and 2) is consistent with previous analyses (Gómez, 2016; Aranciaga Rolando et al., 2019; Lemierre et al., 2023). Unnamed pipimorphs 1 and 2 are recovered as pipimorph, minimally. This uncertainty is linked to the absence of several key skeletal elements and the very fragmentary materials. Most gondwanamorph and pipid synapomorphies are present on the sphenethmoid, ilium and sacrococcyx (Gómez, 2016; Lemierre et al., 2023), all elements missing for both unnamed pipimorphs. However, examination of all MPTs obtained suggests that both taxa possess very strong affinities with the gondwanamorphs. Thus, we attribute both unnamed pipimorphs 1 and 2 to Pipimorpha. The fact that unnamed pipimorph 2 has been recovered in a majority (63%) of MPTs as a gondwanamorph (Fig. 4B) leads us to consider that unnamed pipimorph 2 has putative gondwanamorph affinities.

## 6.2. *Anuran diversity of In Becetèn*

In Becetèn is one of the oldest sites yielding pipid taxa (de Broin et al., 1974; Báez and Rage, 1998; Lemierre et al., 2023). The presence of four pipimorph taxa makes it the richest Cretaceous site for the clade, surpassing the lagerstätte of the Crato Formation where currently two pipimorphs are known (Carvalho et al., 2019; Báez et al., 2021). In addition, several undescribed non-pipimorph anurans are present at In Becetèn (de Broin et al., 1974; Gardner and Rage, 2016; A. Lemierre, unpublished data). Containing at least five anuran and several urodelan taxa (Gardner and Rage, 2016), In Becetèn is the richest amphibian site of the Mesozoic and Paleogene (Early Cenozoic) of Africa. However, few sites have been studied on that continent (Gardner and Rage, 2016), and unstudied sites might harbor a similar or greater diversity.
Interestingly, *Pachycentrata taqueti* is by far the dominant anuran within In Becetèn. *Pachycentrata taqueti* represents around 16% of the total pipimorph specimens identified, and 67% of total anuran specimens attributed to a named genus or species-level taxon. This dominance within the site is likely due to the pachyosteosclerosis of its braincase and vertebrae. This feature explains the better preservation compared to other anuran taxa. In addition, the peculiar ornamentation (vermicular) and aspect (bloated and thickened bones) associated with this feature allows for easy attribution of incomplete elements.

In extant ecosystems, it is common for at least two pipid taxa to coexist (Tinsley, 1975; Tinsley et al., 1979; Kobel et al., 1981; Fouquet et al., 2022). A diversity of four pipid taxa or more (similar to In Becetèn) has been reported in the Amazonian Basin (Fouquet et al., 2022) and within the Great lakes in Africa (Tinsley, 1975; Tinsley et al., 1979). Both regions have been commonly considered biodiversity hotspots (Salzburger et al., 2014; Vasconcellos et al., 2020), and a similar claim could be made for In Becetèn. However, it is possible that all four taxa are not synchronous. In addition, co-existing *Xenopus* taxa are known to hybridize (Tinsley, 1975; Tinsley et al., 1979; Kobel et al., 1981), and possess few (if any) osteological differences (most taxa of *Xenopus* do not have any; Evans et al., 2015). Thus, it is likely that the pipimorph skeletal disparity at In Becetèn is much greater than in most extant ecosystems.

Pipids are known to be voracious anurophages (Vogt et al., 2017). Hence, predation among pipid taxa is high. It is likely that a similar interaction occurred in In Becetèn.

### 6.3. Paleoenvironmental implications

Current analyses of the paleoenvironment of In Becetèn have proposed a fluvio-lacustrine environment (Moody and Sutcliffe, 1991; Mateer et al., 1992). This is similar to other (and older) Cretaceous sites, like Gadoufaoua (northern Niger; Taquet, 1976) or the Kem Kem
(Morocco; Ibrahim et al., 2020). However, the presence of at least four pipimorph taxa at In Becetèn argues for a different paleoenvironment. Indeed, as extant pipids are known to dwell within calm lakes and ponds (Channing and Rödel, 2019), their diversity suggests that In Becetèn was a more lacustrine environment than previously thought.

**7. Conclusion**

Analysis of previously undescribed anuran fossils from In Becetèn led to the identification of two potential new, unnamed, pipimorph taxa. In addition, numerous pipimorph elements are present, but cannot be assigned to any of the four pipimorphs (*Pachycentrata taqueti*, *Inbecetenanura ragei*, unnamed pipimorphs 1 and 2) recognized at In Becetèn. Distinct morphotypes of humerus and ilium can be identified but their significance remains unclear.

Our phylogenetic analyses do not allow us to propose a very precise phylogenetic position for the two new taxa. This is mainly linked to the very few elements (a partial braincase and atlantal complex for the first and a partial braincase for the second) attributed to these taxa.

One of the two unnamed pipimorph taxa may represent a third gondwanomorph taxon from In Becetèn, and the fifth from Mesozoic Africa. This makes In Becetèn the most diverse pipimorph site in Gondwana during the Mesozoic and Paleogene. Finally, the presence of four pipimorph taxa implies that the paleoenvironment was more lacustrine than previously thought, in contrast to other Mesozoic western African sites, like Gadoufaoua or the Kem Kem, which are more fluvial.

**Acknowledgements**

We thank D. Germain (MNHN, Paris) for access to the collection, J. Gardner and M. Delfino for their previous comments on the manuscript, and G. Georgalis and F. I. Carvalho
for their reviews and comments on this manuscript. This study was funded by a grant from the

Fondation pour la Recherche sur la Biodiversité (FRB) to Alfred Lemierre.

**Appendix A. Supplementary data**

Supplementary data associated with this article can be found, in the online version,
at doi:10.1016/j.annpal.2024.102751.

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## Figure captions

<figure><img src="image_2.png" /><figcaption>**Fig. 1.** Unnamed pipimorph 1 of In Becetèn. A–H, right prooticoccipital (MNHN.F.IBC 1626) in A dorsal view, B interpretative drawing of A, C, in ventral view, D interpretative drawing of C, E in posterior view, F, interpretative drawing of E, G, in lateral view, H interpretative drawing of G, I, in medial view, J, interpretative drawing of I; K–N, atlantal complex</figcaption></figure>
(MNHN.F.IBC 1968) in K, anterior, L, posterior, M, dorsal, and N, right lateral views.
Abbreviations: accf, paired acoustic foramen; cdf, condyloid fossa; ec, Eustachian canal; elf, endolymphatic foramen; fao, foramen for the arteria occipitalis; fo, fenestra ovalis; ggf, Gasserian ganglion fossa; hrf, hyomandibular nerve foramen and groove; ipf, inferior perilymphatic foramen; jf, jugular foramen; ocd, occipital condyle; oct, occipital cotyle; or, ornamentation; pct, posterior cotyle; scc, semicircular canals; spf, spinal foramen; spyf, superior perilymphatic foramen; tp, transverse process. [full page width]

Pipimorphe 1 non nommé d'In Becetèn. A–H, prooticoccipital droit (MNHN.F.IBC 1626) A vue dorsale, B dessin interprétatif de A, C, vue ventrale, D dessin interprétatif de C, E vue postérieure, F, dessin interprétatif de E, G, vue latérale, H dessin interprétatif de G, I, vue médiale, J, dessin interprétatif de I; K–N, complexe atlantal (MNHN.F.IBC 1968) K, vue antérieure, L, vue postérieure, M, vue dorsale, et N, vue latérale droite. Abréviations: accf, foramens acoustiques paires; cdf, fosse condyloïde; ec, canal Eustachien; elf, foramen endolymphatique; fao, foramen pour l'arteria occipitalis; fo, fenestra ovalis; ggf, fosse pour le ganglion de Gasser; hrf, foramen et sillon pour le nerf hyomandibulaire; ipf, foramen périlymphatique inférieur; jf, foramen jugulaire; ocd, condyle occipital; oct, cotyle occipital; or, ornamentation; pct, cotyle postérieur; scc, canaux semicirculaires; spf, foramen spinal; spyf, foramen périlymphatique supérieur; tp, processus transverse.
<figure><img src="image_3.png" /><figcaption>**Fig. 2.** Right prooticoccipital (MNHN.F.IBC 2075) of unnamed pipimorph 2 from In Becetèn. Right prooticoccipital in A, in dorsal view, B, interpretative drawing of A, C, in ventral view, D, interpretative drawing of C, E, in posterior view, F, interpretative drawing of E, G, in medial view, H interpretative drawing of G, I, in anterior view, J, interpretative drawing of I, K, in lateral view and L, interpretative drawing of K. Abbreviations as in Figure 1, and: cp, crista parotica; otc, otic capsule; ukf, foramen of unknown homology. [full page width]</figcaption></figure>

*Prooticoccipital droit (MNHN.F.IBC 2075) du pipimorphe 2 non nommé d'In Becetèn. prooticoccipital droit en A, vue dorsale, B, dessin interprétatif de A, C, vue ventrale, D, dessin interprétatif de C, E, vue postérieure, F, dessin interprétatif de E, G, vue médiale, H dessin interprétatif de G, I, vue antérieure, J, dessin interprétatif de I, K, vue latérale et L,*
dessin interprétatif de K. Abpréviations comme dans la Figure 1, et: cp, crista parotica; otc, capsule otique; ukf, foramen d'homologie inconnue.

<figure><img src="image_4.png" /><figcaption>**Fig. 3.** Elements attributed to Pipimorpha indet. A-B, left angular (MNHN.F.IBC 1964) in A, medial and B, lateral; C, vertebra centrum (MNHN.F.IBC 1997e) in dorsal view; D-F, incomplete right scapula (MNHN.F.IBC 1974) in D, dorsal, E, ventral and F, medial views; G-</figcaption></figure>
H, left humerus (MNHN.F.IBC 1977a) assigned to humeral morphotype A in G, ventral and H, dorsal views; I-J, left humerus (MNHN.F.IBC 1655) assigned to humeral morphotype B in I, ventral and J, dorsal views; I-K, left humerus (MNHN.F.IBC 1980) in ventral view; L-O, left ilium (MNHN.F.IBC 1635) assigned to ilial morphotype A in L, lateral, M, medial, N, dorsal and O, posterior views; P-Q, left ilium (MNHN.F.IBC 1649) assigned to ilial morphotype B in P, lateral and Q, medial views; R-S, femur (MNHN.F.IBC 2000a) in R, ventral and S, lateral views; T, tibiofibula (MNHNF.IBC 2001a) in lateral view. Abbreviations: acd, anterior condyle; acf, acetabular fossa; acr, acetabular rim; acrpr, pars acromialis; afcl, articular facet for the clavicle; am, margo anterior; ca, crista anterior; cr, crest; crd, processus coronoideus; dpm, dorsal prominence; dpt, dorsal protuberance; emc, eminentia capitata; fc, fossa cubitalis ventralis; glpr, processus glenoidalis; ish, ilial shaft; isj, ilioischiatic juncture; lc, crista lateralis; lor, lateral oblique ridge; mc, crista medialis; mckg, sulcus pro cartilagine Meckeli; mog, medial oblique groove; mscp, margo suprascapularis; olsc, olecranon scar; pct, posterior cotyle; pm, margo posterior; pxcd, proximal condyle impression; recd, epicondylus radialis; uecd, epicondylus ulnaris; vae, ventral acetabular expansion; vc, crista ventralis. [full page width]

Eléments attribués à des Pipimorpha indéterminés. A-B, angulaire gauche (MNHN.F.IBC 1964) en vues A, médiale et B, latérale; C, centrum de vertèbre (MNHN.F.IBC 1997e) en vue dorsale; D-F, scapula droite incomplète (MNHN.F.IBC 1974) en vues D, dorsale, E, ventrale et F, médiale; G-H, humérus gauche (MNHN.F.IBC 1977a) attribué au morphotype huméral A en vues G, ventrale et H, dorsale; I-J, humérus gauche (MNHN.F.IBC 1655) attribué au morphotype huméral B en vues I, ventrale et J, dorsale; I-K, humérus gauche (MNHN.F.IBC 1980) en vue ventrale; L-O, ilion gauche (MNHN.F.IBC 1635) attribué au morphotype iliaque A en vues L, latérale, M, médiale, N, dorsale et O, postérieure; P-Q, ilion gauche (MNHN.F.IBC 1649) attribué au morphotype iliaque B en vues P, latérale et Q, médiale; R-S, fémur (MNHN.F.IBC 2000a) en vues R, ventrale et S, latérale; T, tibiofibula (MNHNF.IBC
2001a) en vue, latérale. Abréviations: acd, condyle antérieur condyle; acf, fosse acétabulaire; acr, bordure acétabulaire; acrpr, pars acromialis; afcl, facette articulaire pour la clavicule; am, margo anterior; ca, crista anterior; cr, crête; crd, processus coronoideus; dpm, proéminence dorsale; dpt, protubérance dorsale; emc, eminentia capitata; fc, fossa cubitalis ventralis; glpr, processus glenoidalis; ish, diaphyse iliaque; isj, jointure ilioischiatique; lc, crista lateralis; lor, crête oblique latérale; mc, crista medialis; mckg, sulcus pro cartilagine Meckeli; mog, crête oblique médiale; mscp, margo suprascapularis; olsc, cicatrice olécranienne; pct, cotyle postérieur; pm, margo posterior; pxcd, impression du condyle proximal; recd, epicondylus radialis; uecd, epicondylus ulnaris; vae, expansion acétabulaire ventrale; vc, crista ventralis.

<figure><img src="image_5.png" /></figure>
**Fig. 4.** Consensus trees from phylogenetic analysis. A, Strict consensus of 144 MPTs of 647 steps from the analysis performed under equal weight, cline multistate characters ordered (CI = 0.244 RI = 0.469); B, Reduced majority consensus from the same analysis, with only the pipimorph taxa present. † represents extinct taxa; unnamed pipimorphs from In Becetèn are represent in bold italic. In A dashed rectangle highlights pipimorph taxa; numbers above branches designate Bremer support; those below are bootstrap frequencies in A and % of MPTs where the clade was recovered in B. In B, dark gray branches represent phylogenetic position for unnamed pipimorph 1 on the MPTs; light gray branches represent phylogenetical position for unnamed pipimorphs 2 on the MPTs; dashed rectangle highlights gondwanomorph taxa.

[full width page]

Arbres de consensus obtenus par analyse phylogénétique. A, Consensus strict de 144 MPTs de 647 pas de l'analyse réalisée avec poids égaux, caractère à états multiples formant des clines ordonnés (CI = 0.244 RI = 0.469); B ; Consensus majoritaire réduit de la même analyse, avec uniquement les taxons de pipimorphes. † représente les taxons éteints; les pipimorphes non nommés d'In Becetèn sont en gras-italique. Dans A le rectangle en pointillé indique les taxons pipimorphes; les nombres sur le dessus des branches représentent le support de Bremer ceux en dessous sont les fréquences de bootstrap pour A et le % de MPTs où le clade a été retrouvé pour B. Dans B, les branches en gris foncé représentent les potentielles positions phylogénétiques pour le pipimorphe non nommé 1 dans les MPTs ; les branches en gris claires représentent les potentielles positions phylogénétiques pour le pipimorphe non nommé 2 dans les MPTs ; le rectangle en pointillé indique les taxons gondwanomorphes.