# Kembawacela yajuwayeyi n. sp., a new cistecephalid species (Dicynodontia: Emydopoidea) from the Upper Permian of Malawi

R. Araújo, Z. Macungo, V. Fernandez, E.G. Chindebvu, L.L. Jacobs

► To cite this version:

R. Araújo, Z. Macungo, V. Fernandez, E.G. Chindebvu, L.L. Jacobs. Kembawacela yajuwayeyi n. sp., a new cistecephalid species (Dicynodontia: Emydopoidea) from the Upper Permian of Malawi. Journal of African Earth Sciences, 2022, 196, pp.104726. 10.1016/j.jafrearsci.2022.104726. hal-05074747

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# Kembawacela yajuwayeyi n. sp., a new cistecephalid species (Dicynodontia: Emydopoidea) from the Upper Permian of Malawi

R. Araújo<sup>a, *</sup>, Z. Macungo<sup>b</sup>, V. Fernandez<sup>c</sup>, E.G. Chindebvu<sup>d</sup>, L.L. Jacobs<sup>e</sup>

<figure><img src="image_3.png" /></figure>

## ARTICLE INFO

**Keywords:**

Permian
Cistecephalidae
Anomodontia
Wuchiapingian
Therapsida
Malawi

## ABSTRACT

Cistecephalidae are a relatively basal clade of dicynodonts, well-nested within emydopoids, and known to have multiple adaptations to a fossorial lifestyle. In recent years cistecephalid taxonomic diversity has been progressively increasing and important insights into the osteology, soft-tissue anatomy, and paleobiology of the clade have improved considerably. Here we describe a new species of the cistecephalid *Kembawacela* from the Chiweta Beds (northern Malawi, Wuchiapingian), a poorly sampled area of Karoo sediments. Due to the minute dimensions and delicate nature of specimen DMMM-PK-16-1, we utilized propagation phase-contrast synchrotron X-ray micro-computed tomography, revealing conspicuous contrast between rock matrix and bone and allowing reconstruction of its cranial osteology in great detail. DMMM-PK-16-1 is here recognized as a new species based on the morphology of the crista oesophagea of the pterygoid, which has an acute posterior process separate from its contralateral. Despite the affinities with *Kembawacela kitchingi* there are various distinguishable features absent in the taxon (e.g., posterior border of the pterygoids is smoothly concave, rather than interdigitating with the basipostsphenoid). The erection of a new species in this region seems to support the growing evidence for species-level diversity in East African Karoo basins when contrasted to the Main South African Karoo basin. Furthermore, the anatomical resolution obtained allowed us to reconstruct the osseous labyrinth, the paths for several nerve branches, arteries and veins for the first time in cistecephalids, and we develop new hypotheses for their paths and nomenclature for dicynodonts. We found remarkable resemblance in the brain endocast of DMMM-PK-16-1 and another cistecephalid, *Kawingasaurus*, which is distinct from other dicynodonts in which it is known.

## 1. Introduction

Knowledge of the enigmatic fossorial clade Cistecephalidae has been significantly increased in recent years with descriptions of new taxa (Angielczyk et al., 2019; Kammerer et al., 2016) and new insights into the anatomy and paleobiology of the clade (Nasterlack et al., 2012; Laaß, 2015; Macungo et al., 2022). Cistecephalidae is generally accepted as an emydopoid clade; however, intrarelationships among Emydopoidea are controversial with alternative topologies published in recent years (Castanhinha et al., 2013; Boos et al., 2016; Kammerer, 2016, 2019; Olroyd et al., 2017; Angielczyk and Kammerer, 2017; Kammerer et al., 2019; Angielczyk et al., 2019; Macungo et al., 2022). Description and addition of new taxa, including the species here described based on

specimen DMMM-PK-16-1 from Malawi, address phylogenetic issues. Furthermore, the discovery of another new species in an East African Karoo basin seems to provide additional evidence supporting species-level divergence when compared to the Main African Karoo basin (e.g., *Endothiodon tolani*, *Dicynodon angielczyki*, Cox and Angielczyk, 2015; Macungo et al., 2020; Kammerer, 2019a,b; Kammerer et al., 2022). Newly prepared specimens from the Luangwa Basin in Zambia and the Metangula Graben in Mozambique of *Dicynodontoides*, *Oudenodon* or *Daptocephalus* may add strength to this growing pattern (KDA pers. communication, RA pers. observation).

Propagation phase-contrast synchrotron X-ray micro-computed tomography (PPC-SRµCT) and segmentation allows a close look at minute specimens, in this case a cistecephalid, with outstanding detail. These

<footnote><sup>a</sup> Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais 1, Lisboa, Portugal</footnote>

<footnote><sup>b</sup> Museu Nacional de Geologia, Av 24 de Julho n°355, Maputo, Mozambique</footnote>

<footnote><sup>c</sup> European Synchrotron Radiation Facility, 71 avenue des Martyrs, 38000, Grenoble, France</footnote>

<footnote><sup>d</sup> Ministry of National Unity, Private Bag B400, Lilongwe 3, Malawi</footnote>

<footnote><sup>e</sup> Roy M. Huffington Department of Earth Sciences, Southern Methodist University, Dallas, TX, 75275, USA</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: ricardo.araujo@tecnico.ulisboa.pt (R. Araújo).</footnote>
advances in technology available to paleontologists, together with recent developments in understanding the soft-tissue anatomy of extant animals (e.g., Porter and Witmer, 2015; Jones et al., 2019), allow reconstruction of soft-tissue anatomy in extinct clades with an elevated degree of confidence (Witmer and Thomason, 1995). Here we have a fresh look at multiple osteological structures with questionable or poorly understood soft-tissue relationships in dicynodonts by providing an extended anatomical description of a new Malawian cistecephalid recovered from the Chiweta Beds (Fig. 1, Jacobs et al., 2005). We reexamine and reinterpret the soft-tissue functional roles of bony structures that are common to dicynodonts, such as the pineal foramen, quadrate foramen, palatine foramen, lateral palatal foramen, nasolacrimal canal, and the pila antotica. Additionally, we analyze the brain endocast and endosseous labyrinth of the new taxon and recognize some similarities with the cistecephalid *Kawingasaurus* (Laaß, 2015; Laaß and Kaestner, 2017).

## 1.1. *Institutional abbreviations*

BP, Evolutionary Studies Institute (formerly the Bernard Price Institute for Palaeontological Research), University of the Witwatersrand, Johannesburg, South Africa; BSP, Bayerische Staatssammlung für Paläontologie und Historische Geologie, Munich, German; DMMM-PK, Department of Museums and Monuments of Malawi, Lilongwe (PK stands for Permian Karoo) GPIT, Paläontologische Sammlung, Eberhard Karls Universität Tübingen, Tübingen, Germany; MBR, Museum für Naturkunde, Berlin, Germany; SAM, Iziko, The South African Museum, Cape Town, South Africa.

# 2. Materials and methods

## 2.1. *Geology and geographical location*

DMMM-PK-16-1 was recently found in 2016 in the Chiweta Beds, in northern Malawi near the western shore of Lake Malawi (Fig. 1). Preliminary fieldwork in the Mount Waller Area was conducted by Andrew and Bailey (1910). The Chiweta Beds, recognized by F. Dixey (1926), were known as Group 4 by Andrew and Bailey (1910). DMMM-PK-16-1 was collected from the Lower Bone Bed, the main fossiliferous layer, known as Bed No. 5 by Dixey (1926) and “B1” in Haughton (1926). The Lower Bone Beds consist mainly of conglomerate interbedded with purple and grey mudstones and limestone (Dixey, 1926). On the first survey, F. Dixey found gorgonopsians including the rubidgeine *Aelurognathus nyasaensis*, *Chiwetasaurus dixeyi*, and the rhinesuchid temnospondyl *Rhineceps nyasaensis*, all described by Haughton (1926), but see taxonomic revisions by Sigogneau-Russell (1989), Kammerer (2016),

and Marsicano et al. (2017). More recently a new biarmosuchian, *Lende chiweta*, was described (Jacobs et al., 2005; Kruger et al., 2015). In terms of dicynodonts, Haughton (1926) described *Dicynodon* cf. *grandis* and *Dicynodon* cf.? *ictinops*. However, these specimens were subsequently revised by Jacobs et al. (2005) and attributed to *Oudenodon bainii*. Angielczyk et al. (2009) reported the presence of *Dicynodontoides* and *Sidor* et al. (2013) specified *Dicynodontoides nowacki*, listing *Endothiodon uniseries* and *Kitchinganomodon crassus* as well. However, a taxonomic revision and update of Malawian dicynodonts is necessary.

## 2.2. *Propagation phase-contrast synchrotron X-ray micro-computed tomography and segmentation*

DMMM-PK-16-1 was scanned at the beamline BM05 of the European Synchrotron Radiation Facility (ESRF, Grenoble, France), using PPC-SRµCT. The experimental set-up comprised: filtered white beam (2 pole bending magnet 0.85 T; filtration, Cu 3 mm, Al 2 mm, 8 Al rod of 5 mm in diameter and 100 mm in length place horizontally) with a total integrated detected energy of 114 keV; an indirect detector comprising a 2 mm thick LuAG scintillator, 0.5x magnification obtained with a set of Hasselblad photographic lenses (Victor Hasselblad AB, Gothenburg, Sweden) and a PCO.edge 4.2 USB3 cameralink sCMOS detector (PCO, Kelheim, Germany). The sample-detector distance was set to 4.5 m for PPC-SRµCT. In this configuration, the measured pixel size was 11.36 µm. The data acquisition comprised 6000 projections of 0.06 s each over a rotation of 360°. Each projection resulted from the accumulation of 5 frames of 0.012 s each. The centre of rotation was laterally shifted by 10.22 mm (900 pixels) to increase the reconstructed horizontal field of view (i.e., half-acquisition protocol Carlson et al., 2011). Forty-four acquisitions were performed, using a vertical step of 1.8 on the vertical axis, ensuring an approximate 50% vertical overlap to compensate for the vertical beam profile.

Prior to the tomographic reconstruction, radiographs were stitched on the vertical axis. The tomographic reconstruction of the stitched dataset was performed using the single distance phase retrieval approach of the software PyHST2 (Mirone et al., 2014; Paganin et al., 2002). The resulting 32-bit data were converted to a stack of 16-bit tiff images using the minimum and maximum values excluding 0.001% of voxels on both sides of the 3D histogram generated by PyHST2. Additional processing of the data included: ring correction Lyckegaard et al. (2011), normalization of artefactual grey level gradients and metallic inclusions (Cau et al., 2017), cropping of the dataset and binning 2 × 2 × 2 to reduce the size of the data.

Volume processing and rendering was undertaken using the software Amira 5.3.3 (Thermo Fisher Scientific, Hillsborough, OR, USA). Manual segmentation was carried out using the brush tool only. For generating a

A

<figure><img src="image_4.png" /></figure>

B

<figure><img src="image_5.png" /></figure>

C

<figure><img src="image_6.png" /><figcaption>**Fig. 1.** – A – Geographical location of the Chiweta Beds in northern Malawi, where the new cistecephalid species was discovered. B – dorsal view of the specimen as collected from the field. Note that the palatal region of the specimen is entirely covered in matrix. C – propagation phase-contrast synchrotron X-ray micro-computed tomography three-dimensional render of DMMM-PK-16-1 in dorsal view.</figcaption></figure>
surface, we used SurfaceGen tool with constrained smoothing and minimal edge length of 0.4. We present some sections of areas of difficult observation or interpretation in Fig. 2. We divided the segmentation of the near-complete and articulated skull (Fig. 3) to facilitate observation of all anatomical structures into skull roof (Fig. 4), palate (Fig. 5) and basicranium (Fig. 6). We also provide the three-dimensional models of these various components of DMMM-PK-16-1 (Supplementary Information as Morphobank Project P3810. To visualize the three parts of the three-dimensional models the freeware Meshlab can be used. Despite some of the aspects of the basicranium having already been described in Macungo et al. (2022), we maintain them in the current description for completeness.

### 3. Systematic paleontology

THERAPSIDA Broom, 1905a.

ANOMODONTIA Owen (1860).

DICYNODONTIA Owen (1860).

EMYDOPOIDEA Van Hoepen, 1934.

KISTECEPHALIA Seeley (1894).

CISTECEPHALIDAE Broom (1903).

KEMBAWACELA Angielczyk et al., (2019).

Type species. Kembawacelai kitchingi Angielczyk et al., (2019).

*Emended diagnosis.* Kembawacela can be diagnosed on the basis of paired ellipsoidal foramina between the postparietal and the supraoccipital (ef, Fig. 6) which are separated by a short, ventrally-oriented, blunt median process of the postparietal; the presence of ovoid depressions in the palatal component of the maxilla; the posterior border of

<figure><img src="image_7.png" /><figcaption>**Fig. 2.** – DMMM-PK-16-1 selected coronal tomographies. A—section at the anterior region of the right orbit; B –section at the anterior limit of the preserved specimen; C – section at the anterior region of the right orbit; D – section at the orbital midlength; E – section through the infraorbital bar; F – section at the level of the posterior part of the orbit; G – section at the level of the pineal foramen; H – section at midlength of the parietals. Abbreviations: ecpt - ectopterygoid, ch - choana, mx - maxillary, mxa - maxillary antrum, pmx - premaxilla, v - vomer.</figcaption></figure>
<figure><img src="image_8.png" /><figcaption>**Fig. 3.** – *K. yajuwayeyi* complete skull. A – anterior view, B – posterior view, C – right lateral view, D – lateral left view, E – dorsal view, F – ventral view. Abbreviations: fm – foramen magnum, ib – infraorbital bar, o – orbit, ptf – posttemporal fenestra, rn – rostrum notch, tf – temporal fenestra, zp – zygomatic process.</figcaption></figure>

the parietals has three distinct processes; foot-like ventral portion of the jugal; a trough on the ventral surface of the mid-ventral vomerine plate (Angielczyk et al., 2019 and Supplementary Information in Morphobank); and an interparietal that has a pair of anterior processes that extend onto the dorsal surface of the skull, flanking the pineal foramen, but is otherwise restricted to the occipital surface (Angielczyk et al., 2019 and Fig. 3).

Kembawacela yajuwayeyi sp. nov.

LSID. urn:lsid:zoobank.org:pub:FA2AE1D2-B755-4BDF-9D4A-2E014183D3DC.

*Derivation of name.* The species name is in honor of our friend Dr. Yusuf Juwayeyi, accomplished archaeologist, university professor, facilitator of international cooperative research, former head of the Malawi Department of Antiquities, and former Ambassador and Permanent Representative of the Republic of Malawi to the United Nations. Ya- is the Chichewa possessive prefix.

### 3.1. Holotype

DMMM-PK-16-1, a skull missing the anterior portion of the snout, the
<figure><img src="image_9.png" /><figcaption>**Fig. 4.** – *K. yajuwayeyi* digitally isolated skull roof. A – dorsal view, B – tomography section showing the overlapping relationship of the prefrontal, frontal and, postorbital, C – ventral view, D – ventral view with further details of the postorbital, E – lateral right view, F – lateral left view, G-I – dorsal (G), anteroventral (H) and ventral (I) view of the lacrimal and nasolacrimal canal, and J-L – dorsal (J), lateral (K), (I) ventral view of the maxilla and maxillary canal. Anatomical abbreviations: apj – ascending process of the jugal, aorf – anterior ovoid recesses of the frontal, anpj – anterior process of the jugal, arep – ascending ramus of the epipterygoid, dff – descending flanges of the frontals, dfp – descending flanges of the parietal, dpp – descending process of the postorbital, ep – epipterygoid, f – frontal, fee – frontal ellipsoid excavations, fep – epipterygoid footplate, j – jugal, mc – maxillary canal, mipp – middle posterior process of the parietal, mpp – medial posterior process of the parietal, mrp – median ridge of the parietals, pob – postorbital bulge, pf – prefrontal, lf – lacrimal foramen, na – nasal, nlc – nasolacrimal canal, l – lacrimal, p – parietal, po – postobital, por – parietal ovoid recesses, ppj – posterior process of the jugal, ppp – posterolateral process of the parietal, sep – subrectangular portion of the epipterygoid, skpf – skull roof component of the prefrontal, sq – squamosal, tcp – temporal component of the postorbital, trn – transverse ridge of the nasal, vpc – ventral prefrontal crest, zsq – zygomatic process of the squamosal.</figcaption></figure>
<figure><img src="image_10.png" /><figcaption>**Fig. 5.** – *K. yajuwayeyi* digitally isolated palate. A – ventral view, B – dorsal view, C – inset vomer vertical foramen in posterodorsolateral view, D – inset on the morphology of the pterygoid crista oesophagea in ventral view, E – right lateral view, E – left lateral view. Anatomical abbreviations: arpt – anterior ramus of the pterygoid, ch – choana, co – crista oesophagea, cpv – cultriform process of the vomer, dcv – dorsal crests of the vomer, ipv – interpterygoid vacuity, ecpt – ectopterygoid, fcmx – facial component of the maxilla, la – lacrimal, lpf – lateral palatal foramen, mrpmx – median ridge of the premaxilla, mrv – median ridge of the vomer, mvv – mid-ventral vomerine plates, mx – maxilla, odpmx – ovoid depressions of the premaxilla, pal – palatine, paf – palatine foramen, plmx – posterolateral portion of the maxilla, pmx – premaxilla, ppco – posterior process of the crista oesophagea, pshr – parasphenoid rostrum, qrpt – quadrate ramus of the pterygoid, srpt – subtriangular recess of the pterygoid, vcv – ventral crests of the vomer, vf – vertical foramen, vkpt – ventral keel of the pterygoid, vvc – vomer vertical crests, vg – vascular groove.</figcaption></figure>

left zygomatic arch and postorbital bar, as well as some portions of the
occiput.

3.2. Age

Kruger et al. (2015) correlate Chiweta with the *Cistecephalus*
Assemblage Zone of South Africa, which ranges in age from close to

256.247 Ma to 255.2 Ma (Rubidge et al., 2013; Smith, 2020; Smith et al., 2020). This interval is contained within the Wuchiapingian Stage (259 ± 0.5–254.14 ± 0.07 Ma; Liu et al., 2019; Shen et al., 2013; Shen et al., 2019) of the Upper Permian.
<figure><img src="image_11.png" /><figcaption>**Fig. 6.** Comparison between *K. kitchingi* and *K. yajuwayeyi* of the details of the median pterygoid plate region. A – ventral view of *K. kitchingi* (NHCC LB 18), photo credit: Kenneth D. Angielczyk, B – ventral view of *K. yajuwayeyi* (DMMM-PK-16-1), C – interpretation of *K. kitchingi* (NHCC LB 18) median pterygoid plate region, D – forcing the two pterygoids of DMMM-PK-16-1 to meet at the median sagittal plane would result in a significantly different morphology than that seen for *K. kitchingi* in that: a) the angle between the anterior rami of the pterygoids is significantly smaller in *K. yajuwayeyi*, b) the resulting median pterygoid plate is proportionately much longer in *K. yajuwayeyi*, c) the posterior border of the median pterygoid plate is smoothly concave and does not interdigitate with the basipostsphenoid. Question mark denotes that forcing the pterygoids to meet together at the midline is hypothetical, not the observed anatomy. We cannot discard though that the observed anatomy is the result of dorsoventral compression potentially leading to splayed pterygoids.</figcaption></figure>

### 3.3. Diagnosis

*Kembawacela yajuwayeyi* exhibits the following autapomorphy: the crista oesophagea of the pterygoid has an acute posterior process separate from its contralateral (ppco, Figs. 5 and 6).

*Possible autapomorphies pending computed tomography confirmation in other dicynodonts:* crest-like dorsum sellae; presence of transverse crests and lateral recess on the anterior surface of the supraoccipital; pila antotica with thickened anterior and posterior edges on its lateral aspect, thereby forming an acute subtriangular recess and a medial recess; and the presence of distinct ampullae in all semicircular canals.

*Unique combination of characters:* nasal is ornamented by subcircular pits that sculpture the lateral aspect; absence of the median lobe of the supraoccipital; the presence of the nasal transverse ridge.

*Differential diagnosis:* It can be distinguished from *K. kitchingi* by the ascending process of the jugal, which mostly forms the medial aspect of the postorbital bar; the anterior process of the jugal is significantly taller; the maxillary canal is immediately anterior to the maxillary antrum (Fig. 7); smoothly rounded posterior contact of the frontal to the parietal, frontal possesses minute pits (but is not ornamented by visible foramina); the posterior edge of the pterygoid median plate does not interdigitate with the basipostsphenoid, but it is smoothly concave
<figure><img src="image_12.png" /><figcaption>**Fig. 7.** – *K. yajuwayeyi* maxillary canal, lacrimal gland and maxillary antrum. A – comparison with *K. kitchingi* maxillary canal and antrum in lateral view (NHCC LB18). Coronal red line denoting approximate region in NHCC LB18 until where DMMM-PK-16-1 is preserved. Image credit: Julien Benoit. B – schematics of the maxillary antrum and canal in DMMM-PK-16-1. C – lacrimal gland (salmon color), maxillary antrum (light green) and canal (yellow) as rendered after segmentation. D – relationship of the maxillary antrum and lacrimal gland with surrounding bones of DMMM-PK-16-1. Note that only the medialmost portion of the maxillary antrum was segmented; this corresponding region in NHCC LB18 (*K. kitchingi*) has an anteriorly projecting tapered region, see A. E – lacrimal canal, maxillary canal and antrum of DMMM-PK-16-1 in relation with surrounding bones including a semi-transparent maxilla (light blue). Abbreviations: f – frontal, j – jugal, l – lacrimal, lg – lacrimal gland, max antrum – maxillary antrum, max canal – maxillary canal, mx – maxilla, n – nasal, pfr – prefrontal.</figcaption></figure>

(Fig. 6C and D); and the angle between the palatal rami of the pterygoids is significantly smaller (~46°; whereas *K. kitchingi* is ~61°, Fig. 6 C and D).

It can be differentiated from *Sauroscaptor tharavati* by the absence of a (bipartite) nuchal crest and the transverse ridge on the skull roof is at the level of the nasal (not the frontal).

It can be differentiated from *Cistecephalus microrhinus* because the anterior border of the parietals are smoothly convex (do not form an anteriorly directed angle), the rostrum notch does not form a right angle with temporal bar, being significantly more smoothly convex laterally; the opisthotic has divergent crests on the posterior aspect.

It can be differentiated from *Kawingasaurus fossilis* by having semi-circular canals that are distant from the vestibule (i.e., does not have a highly inflated vestibule), by lacking the prootic anterior groove near the lateral opening of the facial foramen and it has a developed crista oesophagea on the ventral surface of the median pterygoid plate.

It can be differentiated from *Cistecephaloides boonstrai* by having a smoothly concave posterior border of the median pterygoid plate (i.e., the posterior border of the median pterygoid plate does not interdigitate with the basipostsphenoid), by having a box-like skull shape (i.e., not subtriangular), and by having a rostrum notch.

**Remarks:** The absence of a median pterygoid plate (ergo, exposing the parasphenoid rostrum ventrally and separating the pterygoids) could be a differentiating character from *K. kitchingi*, however, another

specimen of *K. yajuwayeyi* with a preserved palate is needed to assure the biological relevance of this character. The dorsoventral compression of DMMM-PK-16-1 could have resulted in splaying the pterygoids, thus leading to a taphonomical origin of their separation. It is, nevertheless, conceivable that the absence of the median pterygoid plate is of biological significance as, rarely, demonstrated in some taxa such as *Cistecephaloides, Delectosaurus* or *Idelesaurus*. However, if the pterygoids are forced to contact each other, an important difference at the level of the median pterygoid plate becomes apparent (Fig. 6 D). The anteroposterior extension of the median pterygoid plate is proportionately longer compared to *K. kitchingi*. For instance, in comparing the range of variation of this feature in *Cistecephalus microrhinus*, another well-known cistecephalid, the range of variation of the ratio between length and width of the median pterygoid plate in *K. yajuwayeyi* (0.57) seems to be significantly different from that of *K. kitchingi* (0.99). We collected data from photographs (courtesy of Christian Kammerer) of various *Cistecephalus microrhinus* specimens, as follows: BSPG1932 (0.62), BSPG1932-I-56 (0.76), SAM-PK-K11187 (0.75), MBR1001 (0.58), BP2 (0.64). The range of variation is ~30% in this feature in *Cistecephalus*, significantly lower than the variation between *K. yajuwayeyi* and *K. kitchingi* (~70%). Similarly, as mentioned above, the angle between the two anterior rami of the pterygoid is significantly disparate if we compare with the intra-specific variation in *Ciscephalus microrhinus* (BSP1932-I-502: 51.8°, BSPG1932-I-56: 52.6°, SAM-PK-K11187: 53.4°, MBR1001: 53.0°, BP2:
53.7°; range of variation: ~4%). The angle between the anterior rami of the pterygoid varies ~32%, which is significantly above the intra-specific variation observed in a related cistecephalid species.

# 4. Comparative anatomical description

## 4.1. Skull

DMMM-PK-16-1 comprises a nearly complete skull (Figs. 1B and 3), whose anatomy is easily discernible using the synchrotron computed tomography protocol described above. However, DMMM-PK-16-1 is riddled with minute fractures, which can make recognition of the boundaries between bones difficult. We specified these regions in the anatomical description below and Fig. 2. The anteriormost part of the snout is missing, including the skull roof component of the premaxillae and the entirety of the septomaxillae. The sphenethmoid, scleral ossicles, and stapes are not preserved. Additionally, the left zygomatic arch and postorbital bar are not preserved. The right dorsoposterior corner of the skull is slightly weathered away affecting parts of the occipital plate. Small portions of the left posterodorsal occipital plate are missing.

Dorsoventral compression is among the most common taphonomic deformational patterns in dicynodonts (Kammerer et al., 2020). The dorsoventral taphonomic compression makes the skull look like *Cistecephaloides* in that the posterior edge of the skull roof slopes. However, if the skull was not taphonomically modified, it probably resembled more the *Cistecephalus* and *K. kitchingi* condition (see Fig. 7 of Angielczyk et al., 2019), in which the transition between the skull roof and occipital plate is sharp. The skull seems to be proportionally broader posteriorly compared to other cistecephalids and the snout is proportionately broader than other cistecephalids at the level of the rostral notch, again probably as a result of taphonomic distortion. This taphonomic pattern makes the orbits proportionally placed more posteriorly and seem larger when compared to well-preserved cistecephalids. In lateral view the skull roof is nearly as flat as in *Sauroscaptor*, not convex as in *K. kitchingi* (NHCC LB18, BP/1/3591, and BP/1/3612) and *Cistecephaloides*. This variation with *K. kitchingi* should be considered carefully due to important dorsoventral deformation in DMMM-PK-16-1. As in *K. kitchingi* the mandibular articulation is rotated anteriorly, contrasting with a much less rotated *Sauroscaptor* mandibular articulation.

The palate configuration and proportions overlap well with that of *K. kitchingi*, except the anterior extension of the parabasisphenoid, which seems to be longer in the latter. As typical for cistecephalids and emydopoids, there is a broad intertemporal area, with the exception of the emydopoid *Cistecephaloides* (Cox, 1959).

The condylobasal length of *K. yajuwayeyi* is estimated to be 45.34 mm based on the *Cistecephalus* skull SAM-PK-K7852 and 45.17 mm on the *Cistecephaloides* skull SAM-PK-6243. It is the second smallest cistecephalid when compared with other well-known taxa, being only slightly larger than *Kawingasaurus* (33.9–40.7 mm; Angielczyk et al., 2019). The dorsoventral taphonomic deformation emphasizes the orientation of the orbits dorsally; it is thus conceivable that frontally-oriented orbits were present in DMMM-PK-16-1 as in *K. kitchingi*, *Sauroscaptor* and *Cistecephalus* (Nasterlack et al., 2012; Kammerer et al., 2016; Angielczyk et al., 2019), unlike the anterodorsally oriented orbits of *Kawingasaurus* and *Cistecephaloides* (Figs. 1 and 3).

## 4.2. Premaxilla

Only the palatal portion of the premaxilla on the ventral aspect of the skull is preserved. The preserved portion does not extend to the choanae posteriorly, contacts the maxilla along most of its lateral extension, and sutures the vomer medially (Figs. 2A and 3F). The right and left premaxillae are coossified and no suture is discernible. The anterior portion of the premaxilla is not preserved. The general shape of the preserved premaxilla is arched, with a dorsal convexity as in *Cistecephalus* (Keyser,

1973), *Emydops* (Fourie, 1993), *Sauroscaptor* (Kammerer et al., 2016), and *K. kitchingi* (Angielczyk et al., 2019). Most of the preserved premaxilla is a thin sheet of bone, but on the dorsal side a thickening follows the maxilla extension. There are no premaxillary teeth.

In dorsal view, the posterior border of the premaxilla is concave laterally. However, the median anterior projection of the vomer overlaps a large portion of the premaxilla. In the tomographies, a clear distinction between the vomerine portion and the premaxillary portion of the median ridge is visible (Fig. 2B). In ventral view, the premaxillary portion of the median ridge extends a short distance posteriorly giving it a subtriangular shape that becomes flush with the palatal surface of the premaxilla, immediately anterior to the anterior edge of the ovoid depressions of the maxilla. An incipient vascular groove lies lateral to the median ridge on the palatal surface of the premaxilla (Character 7), as in all other cistecephalids.

## 4.3. Septomaxilla

The septomaxillae are not preserved.

## 4.4. Maxilla

The maxilla is preserved comprising most of the palatal component (Fig. 3), the posterolateral ramus that articulates with the jugal posterodorsally, and the facial component, whose anterior extension is missing (Figs. 3 and 4). The palatal component of the maxilla has a medial contact with the premaxilla; this contact runs posteromedially, oblique to the sagittal plane. The maxilla contacts the ectopterygoid via an interdigitating suture (Fig. 2C). The maxilla contacts the palatine posteriorly, forms the anterior border of the choanae, and contacts the vomer posteromedially.

The palatal component has two ovoid depressions (odpmx, Fig. 4A), as in *K. kitchingi* (Angielczyk et al., 2019), near the medial contact with the vomers that extend posteriorly nearly to the level of the choanae and anteriorly to the level at which the vomers begin to flatten. Similar distinct depressions occur also in *Cistecephalus*, but do not close anteriorly and resemble furrows (Keyser, 1973).

The facial component of the maxilla comprises a contact in which the nasal overlaps the maxilla dorsally, followed by the contact with the lacrimal, which allows a lateral contact between the maxilla with the jugal. The posterior tip of the maxilla possibly contacts the zygomatic process of the squamosal. The contact with the squamosal posteriorly is inferred because the bones are displaced taphonomically and do not contact each other. The facial component of the maxilla is abundantly ornamented with subcircular pits and anteroposteriorly-oriented furrows, which are vascularized by a network of canals (see Fig. 4J-L). This network of canals, given its location anterior to the maxillary antrum, seems to be the posteriormost portion of the maxillary canal. The location of the maxillary canal (mc, Fig. 4J-L) relative to the maxillary antrum is distinct from *K. kitchingi*, whose maxillary canal departs from the lateral side of the maxillary antrum and runs lateral to it posteriorly (Benoit et al., 2018). There is an ample maxillary antrum (Figs. 2A and 7) that opens into the lacrimal posteriorly, as in *Cistecephalus* (Keyser, 1973). The maxillary antrum is formed by the lacrimal dorsally, the maxilla anteriorly and ventrally, the prefrontal and jugal laterally, thus being partially engulfed by the suborbital bar as well. This region is here interpreted as the lacrimal gland bony enclosure. The nasal is excluded from the maxillary antrum as this bone is a simple sheet of bone that overlaps the maxilla. Notably, such simple structure of the nasal does not prevent the maxilla from contacting the prefrontal internally. Unfortunately, this condition cannot be confirmed in other cistecephalids (e.g., Angielczyk et al., 2019).

The preserved maxillary contribution to the rostrum is wide anteriorly but swiftly slopes ventrally as the bone projects posteriorly, giving a teardrop appearance to the bone in lateral view. There is no postnarial depression as in most other cistecephalids (Brink, 1950; Keyser, 1973),
thus resembling the condition in *Sauroscaptor* (Kammerer et al., 2016). A caniniform process is not preserved, and there is no evidence of maxillary teeth or tusks.

### 4.5. Nasal

The posterior portion of the nasals is preserved; however, their anterior contact with the premaxilla is eroded off. The nasal contacts the maxilla anterolaterally, a small lateral flange of bone contacts the lacrimal laterally, followed by an extensive lateral contact of the prefrontal posterolaterally and the frontal posteriorly. The nasal contacts its contralateral counterpart along an extensive and firmly coossified median suture. Despite being mostly broken along its anteroposterior length, the suture is discernible posteriorly in the PPC-SRµCT data (Fig. 2D). The nasals are dorsally convex, and the ventral side of the bones is featureless.

The sheet-like structure of the nasals leads to a simple contact with the maxilla as an overlapping flap of bone. The contact with the lacrimal occurs at the inception of the suborbital bar. The suture with the prefrontal is made along a concave suture that continues posteriorly to meet the frontal, and the posteriormost corner inflects at a right angle being straight along most of the frontonasal suture. The nasal is ornamented by subcircular pits that sculpture mostly the flanks of the bone. On the dorsal aspect of the anterior region of the nasal, a ridge extends mediolaterally (ntr, nasal transverse ridge, Fig. 4), being raised relative to the anterior part of the skull. A similar transverse ridge is observed in *Sauroscaptor* (Kammerer et al., 2016). However, a single incipient nasal boss, as in *Cistecephalus*, *Cistecephaloides* or *K. kitchingi* (Angielczyk et al., 2019), is absent in the preserved portion of this specimen.

### 4.6. Prefrontal

The prefrontal is well preserved on both sides of the skull and has a crescentic shape with the concavity facing the orbit in dorsal view. The prefrontal makes up most of the medial orbital border, but does not preclude the frontal from participation in the orbit. This is not only because there is a small portion of the frontal between the prefrontal and postorbital, but also the frontal covers the prefrontal until it reaches the orbit. The prefrontal contacts the lacrimal anterolaterally, and the nasal along nearly half its medial extension. The lack of a superficial prefrontal-maxilla contact resembles the condition in *K. kitchingi* (Angielczyk et al., 2019), which contrasts with other cistecephalids (Cox, 1972; Cluver, 1974a). The sutures with the surrounding bones are highly interdigitated (Fig. 2A, D). The inflection of the prefrontal from the skull roof to the orbital component forms a distinct rim (pfr, prefrontal rim, Fig. 4E). The orbital component of the prefrontal is a subrectangular sheet of bone that is slightly more ventrally-projecting anteriorly. A small concavity lies on the ventral border of the orbital component midlength ventrally. In the ventral aspect of the prefrontal, a well-defined anteriorly rounded recess opens posteriorly as the delimiting ventral prefrontal crest (vpc, Fig. 4) fades posteriorly. The prefrontal dorsal surface is finely ornamented by minute pits and striations. No prefrontal boss or supraorbital ridges occur; the latter present in *Cistecephalus* (Nasterlack et al., 2012).

### 4.7. Lacrimal

The lacrimal is only preserved on the right side of the specimen (Figs. 3 and 4). The lacrimal contributes to the anteroventral side of the orbit, and has an extensive anteroventral contact with the maxilla, a medial contact with prefrontal, and a broad engulfing scarf joint with the anterior process of the jugal. As in *Cistecephalus* (Keyser, 1973), it forms an important portion of the maxillary antrum. The lacrimal is not covered by the prefrontal in dorsal view as in *Niassodon* (Castanhinha et al., 2013). The medial extension of the lacrimal is thus wedged between the jugal and the posterior process of the maxilla.

The lacrimal foramen runs horizontally and obliquely to the sagittal axis of the skull, where the anterior extent is directed medially (Fig. 4G-I). The lacrimal foramen has a relatively uniform subcircular cross-section, approximately 760 µm in diameter. The lacrimal foramen originates anteriorly at the inception of the suborbital bar, dorsal to the maxillary antrum, at the interior surface of the skull roof. It is visible on the ventral side of the skull roof and it is bordered medially by a small ridge (Fig. 2E) that runs along the same direction as the foramen. The lacrimal foramen exits close to the prefrontal contact, where the orbital component of the lacrimal meets the facial component of the bone at the orbital rim.

### 4.8. Jugal

The jugal forms much of the posterior and medial portion of the postorbital bar, and the anterior inception of the zygomatic arch. The ascending process of the jugal (apj, Fig. 3) has an extensive contact with the postorbital laterally, the anterior process of the jugal is mostly received by the lacrimal medially and ventrally, and the zygomatic process of the squamosal contacts the posterior extension of the jugal laterally. All jugal sutures are scarf joints. Whereas in *K. kitchingi* the ascending process forms mostly the posterior aspect of the postorbital bar (Angielczyk et al., 2019), in *K. yajuwayeyi* it seems to form mostly the medial aspect, as in *Diictodon* (Sullivan and Reisz, 2005). This does seem to be a biologically significant difference because dorsoventral compression, if having an effect, would emphasize the posterior exposure of the ascending process of the jugal due to the nature of the joint with the postorbital.

The anterior process (anpj, Fig. 3) is somewhat ellipsoidal with a medial torsion to conform to the suborbital bar. The ventral border of the anterior process bows significantly ventrally to near the ventral aspect of the suborbital bar, which is shared with *K. kitchingi*. However, this region is significantly taller in DMMM-PK-16-1 than in *K. kitchingi* (Angielczyk et al., 2019). The posterior process (ppj, Fig. 3) is significantly smaller than the anterior process, and its posterior tip is subtriangular.

### 4.9. Frontal

The frontal has a subrectangular shape, contacting the nasal anteriorly, the prefrontal anterolaterally, the postorbital laterally, the parietal posteriorly, and its contralateral medially. A small portion of the frontal participates on the posterodorsal border of the orbit (Fig. 4E). The nasofrontal suture is straight and indents medially into each frontal (somewhat similar to *K. kitchingi*, Angielczyk et al., 2019), whereas the frontal overlaps with a flange of the prefrontal. Also, the postorbital-frontal suture is smoothly concave laterally as visible on the right side, as the left side is significantly abraded. The frontoparietal suture is gently concave posteriorly. This is similar to the condition in *Sauroscaptor*, although straighter in this species (Kammerer et al., 2016). However, the posterior part of the frontal is somewhat triangular in *K. kitchingi* (Angielczyk et al., 2019). The median frontal suture is well visible from the PPC-SRµCT data, extending to near the anterior median border of the pineal foramen (Fig. 2D, and Supplementary Information in Morphobank). The median frontal suture is irregular through its anteroposterior extension but is more a transverse slot joint anteriorly (Fig. 2F, see Jones et al., 2011 for joint nomenclature), becoming a scarf joint posteriorly with the left frontal overlapping the right counterpart. The suture of the parietal coincides with a fracture; however, clear structural patterns are visible at certain points. It may be that the frontoparietal suture is a structurally weak area biomechanically, which was probably also subjected to forces during fossilization opening the suture further. The sutures with the nasal, postorbital and prefrontal are interdigitated. The frontal is unornamented, possessing only minute pits visible in the PPC-SRµCT data, contrary to *K. kitchingi* that possesses visible foramina (Angielczyk et al., 2019).
The descending flanges of the parietals continue anteriorly onto the frontals, as in *Niassodon* (Castanhinha et al., 2013). In the ventral aspect of the frontals, conspicuous ellipsoidal recesses occur at the level of the postorbital bar, presumably to support olfactory bulbs in life (Supplementary Information in Morphobank, Fig. 10). If this is the correct interpretation, the olfactory bulbs of *K. yajuwayeyi* alongside *Kawinga-saurus* seem to have been among the relatively largest and most prominent among dicynodonts (Laaß and Kaestner, 2017). Separating the ellipsoid excavations (fee, frontal ellipsoid excavations, Fig. 4) is a shallow broad ridge, hourglass in shape. Anterior to the frontal ellipsoidal excavation there is a thin crest that delimits other ovoid recesses (aorf, anterior ovoid recess of the frontal, Fig. 4) that remain open anteriorly. These excavations seem to differ from the anatomy in *K. hitchingi* in that there is no evident ophthalmic tract anterior to it (Angielczyk et al., 2019).

### 4.10. Postfrontal

As in other cistecephalids there is no postfrontal (Broili and Schröder, 1935; Brink, 1950; Cox, 1972; Keyser, 1973; Cluver, 1974a; Kammerer et al., 2016; Angielczyk et al., 2019).

### 4.11. Preparietal

As it has been proposed for other cistecephalids (Broili and Schröder, 1935; Brink, 1950; Cox, 1972; Keyser, 1973; Cluver, 1974a; Kammerer et al., 2016; Angielczyk et al., 2019), the preparietal is absent. However, there are discrete fragments of the parietal surrounding the pineal foramen (Fig. 2H).

### 4.12. Parietal

The parietal is a paired element with subtriangular shape and the apex of the triangle at the posterolateral corner of the skull roof as in other cistecephalids (Kammerer et al., 2016; Angielczyk et al., 2019). The parietal has an anterior convex border that contacts the frontal and has a rugged posterior border that contacts the postparietal medially. The parietal would also have contacted the squamosal laterally if it was preserved. The postparietal-parietal contacts via an interdigitating suture, clearly visible in the tomographic sections. The parietal-parietal suture is a horizontal slot joint (Fig. 2I). The parietal contacts the postorbital laterally via a stepped tongue and groove joint (Fig. 2F, see Jones et al., 2011).

The posterior border of the parietals has three distinct processes similar to the condition in *K. hitchingi* (Angielczyk et al., 2019): a medial process (mpp, medial parietal process, Fig. 4A), a middle process that results from a ventral buttress on the parietal (mipp, middle parietal process, Fig. 4A), and a posterolateral process (ppp, Fig. 4A). The medial process is the largest and is subrectangular in shape. The middle process results from a ventral subtriangular thickening of the parietal. The posterolateral processes are short and follow the posterior extension of the postorbitals to form the medial wall of the adductor chamber. In ventral view, the parietals form distinct ventrally-projecting crests also known as the descending flanges (dfp, Fig. 4C). The descending flanges of the parietals are parallel to each other and are thicker at the base, thinning out ventrally (Fig. 4C and D), the posterior corner of the descending flanges of the parietal contacts the epipterygoid. The parietals are slightly domed between the descending flanges of the parietals (por, parietal ovoid recesses, Figs. 2H and 4), and there is a very faint median ridge separating the recesses (mrp, Fig. 4C, Supplementary Information in Morphobank). In ventral aspect, the parietal flanges thin ventrally, and more anteriorly, also formed by the frontals.

### 4.13. Postorbital

The postorbital, as in all dicynodonts, is constituted by two main

anatomical subunits: the descending process (dpp, Fig. 4) that forms most of the postorbital bar together with the jugal, and the temporal component (tcp, Fig. 4) that constitutes the lateral surface of the skull roof. The postorbital contacts the jugal along most of the descending process, the frontal medially, as well as the parietal more posteriorly, and the squamosal posteroventrally. The descending process of the left postorbital is broken, and the posteriormost portion of the temporal component of the right postorbital is damaged. The dorsal surface of the descending process of the postorbital is not well preserved. However, the medial aspect of postorbital descending process forms a shallow concavity that receives the jugal. The angle between the medial and the anterior border of the descending process is smoothly rounded, and the posterior border seems to be sharp, but preservation may hinder visualization of the actual anatomy. Nevertheless, at some points of the descending process the anterior border envelops the jugal slightly. The descending process tapers towards its ventral tip.

The temporal component of the postorbital is laterally convex and is well exposed dorsally. The postorbital temporal component is smoothly curved in cross-section through most of its anteroposterior extent, yet it has a biplanar postorbital temporal component (Kammerer et al., 2015; Angielczyk and Kammerer, 2017). In ventral view, the postorbital temporal component shows a significant bulge (pob, postorbital bulge, Fig. 4C and D) running along the medial border of the adductor chamber, which tapers posteriorly into a pointed process to reach the lateral aspect of the squamosal dorsal process. The posteriormost postorbital temporal component bends ventrally to conform to the occipital plate. Most of the postorbital is overlain by the frontal, being only visible in the ventral side of the skull roof.

### 4.14. Squamosal

The squamosal can be divided into three components as in all dicynodonts: the dorsal process, the ventral process, and the zygomatic process. Neither of the squamosals is complete; the right squamosal possesses the entirety of the zygomatic process but parts of the dorsal process (dpsq, Fig. 8) are missing, and the left squamosal is missing the zygomatic process, a lateral portion of the dorsal process, and most of the ventral process. The zygomatic process of the squamosal contacts the jugal anteromedially, and the lacrimal and maxilla along the anteriormost tip of the bone. The squamosal ventral process contacts the quadrate and quadratojugal anteriorly, the opisthotic medially, and the supraoccipital half way toward the squamosal dorsal process. The dorsal process contacts the postorbital dorsally, and typically in dicynodonts it would have contacted the tabular and postparietal medially. However, due to preservation we cannot ascertain these contacts.

The zygomatic process runs subhorizontally, tapers anteriorly to a pointed end, and is transversely expanded. The zygomatic process of the squamosal bows slightly medially towards the sagittal plane and imparts a dorsal convexity to the bone. Near the occipital plane the zygomatic process flares into the dorsal and ventral processes posteriorly. Ventral to the connection between the zygomatic process to the dorsal and ventral processes is a laterally bulging process (lpsq, lateral process of the squamosal, Fig. 8D), giving a subtriangular aspect to the squamosal in posterior view. This is clearer on the right side of the specimen.

The squamosal ventral process (vpsq, Fig. 8D) possesses a deep ellipsoidal embayment anteriorly to receive the posterior aspect of the quadrate.

### 4.15. Vomer

The vomer is an unpaired median element of the palate that has two main anatomical components: the mid-ventral vomerine plate (mvv, Fig. 5), and the cultriform process of the vomer (cpv, Fig. 5). The vomer is mostly engulfed by both premaxillae anteriorly and laterally, but the mid-ventral vomerine plate contacts the palatine anteriorly in a simple butt joint. The vomer contacts the cultriform process of the
<figure><img src="image_13.png" /><figcaption>**Fig. 8.** – *K. yajuwayeyi* digitally isolated occiput and zygomatic process. A – anterior view, B – inset of the anterolaterodorsal view of the braincase, C – lateral right view, D – posterior view. Anatomical abbreviations: acp – alar component of the prootic, afmcq – anterior flange of the medial condyle of the quadrate, apc – anterior postparietal crests, bocc – basioccipital, arp – anterior ridge of the postparietal, bsht – basisphenoidal tubera, dce – dorsal component of the exoccipital, dpq – dorsal process of the quadrate, dpsq – dorsal process of the squamosal, ef – ellipsoidal fenestra, exocc – exoccipital, ff – floccular fossa, fm – foramen magnum, fnf – facial nerve foramen, igq – intercondylar groove of the quadrate, j – jugal, jf – jugular foramen, lcq – lateral condyle of the quadrate, lps – lateral process of the supraoccipital, lpsq – lateral process of the squamosal, lq – left quadrate, mcq – medial condyle of the quadrate, mss – medial section of the supraoccipital, mppa – median posterior process of the postparietal, op – opisthotic, osr – opisthotic subtriangular recess, oce – occipital component of the exoccipital, odc – opisthotic divergent crests, pa – pila antotica, pashr – parasphenoid rostrum, pasr – pila antotica subtriangular recess, pac – pila antotica ridges, psr – prootic-supraoccipital recess, pqj – plate component of the quadratojugal, ptf – posttemporal fenestra, pp – postparietal, pro – prootic, q – quadrate, qj – quadratojugal, rq – right quadrate, slr – supraoccipital lateral recess, spcc – supraoccipital-prootic coronal crests, sq – squamosal, stc – supraoccipital transverse crest, vpqj – ventral process of the quadratojugal, vpsq – ventral process of the squamosal, t – tabular, tr – trochlea, tn – trigeminal notch.</figcaption></figure>
parasphenoid posteromedially and the medial wall of the pterygoid anterior process posterolaterally. The vomer forms the median wall of the choanae and extends posteriorly to the basisphenoidal region. The cultriform process has subparallel double crests dorsally (dcv, dorsal crests of the vomer, Fig. 5) that extend to near the anterior contact of the premaxillae (contrary to *Cistecephalus* and *Cistecephaloides*, but as in *K. hitchingi*; Angielczyk et al., 2019), where the crests fade acutely. These double crests broaden slightly at the level of the choanae, where they are also thickest.

In ventral view, near the pterygoid contact the vomer forms two sharp, ventrally-directed crests (vcv, ventral crests of the vomer, Fig. 5), that unite at the level of the choanae. The cultriform process of the vomer terminates at the posteriormost level of the mid-ventral vomerine plate, where the palate continues as a rod formed by the cultriform process of the basipresphenoid.

The mid-ventral vomerine plate is a dome-shaped subtriangular process that expands ventrally from the dorsal edge of the vomer, in contrast with the subtrapezoidal shape in *Diictodon* (Sullivan and Reisz, 2005). The choanal space mostly formed by the mid-ventral vomerine plate curves steeply ventrally imparting a hyperbolic shape to this part of the bone. There is no anterior expansion as in pylaecaphalids (*Angielczyk and Rubidge, 2013*). There are two posteriorly-directed processes that bound the cultriform process of the basipresphenoid, which are present in *Cistecephalus* as well (RA pers. observation). A well-developed dorsal crest develops in the lateral extension of the mid-ventral vomerine plate near the choanae and bears a vertical sub-circular palatine foramen (vvc, palatine vertical crest, and, vf, palatine vertical foramen, Fig. 5B,C), which we interpret to be the passage for the sphenopalatine artery and pterygopalatine nerve (see below).

### 4.16. Palatine

The palatine is a pad-like element forming a small portion of the secondary palate of *K. yajuwayeyi*, being pierced by a large palatine foramen (paf, palatine foramen, Fig. 5A) as in *K. hitchingi* (*Angielczyk et al.*, 2019) but in contrast to *Diictodon* and *Niassodon* (Sullivan and Reisz, 2005; Castanhinha et al., 2013). The palatine is subtriangular, it is generally ventrally convex, and forms most of the lateral border of the choanae (Fig. 5). The palatine sutures the maxillae along its anterior border, contacts the ectopterygoid laterally, and the mid-ventral vomerine plate posteromedially. The palatine foramen is circular and it is placed posteromedially near the contact with the mid-ventral vomerine plate. The lateral palatal foramen is located at midlength of the palatine.

### 4.17. Ectopterygoid

The ectopterygoid is a small anteroposteriorly elongate bone bordering the lateral aspect of the palate (Fig. 5). The ectopterygoid has an extensive medial contact with the palatine and an interdigitating suture with the pterygoid posteriorly and the maxilla anteriorly. The lateral aspect of the ectopterygoid forms part of the ventromedial aspect of the orbit. The anterior half of the ectopterygoid forms the lateral border of an ellipsoidal lateral palatal foramen (lpf, Fig. 5A). The long axis of the ellipse is oriented anterolaterally to posteromedially. The lateral palatal foramen is located posterior to the palatine foramen. This condition is similar to the position of the lateral palatine foramen in *Diictodon*, *K. hitchingi*, or *Niassodon* (Castanhinha et al., 2013; Angielczyk et al., 2019; Sullivan and Reisz, 2005). As in these taxa, the lateral palatine foramen is placed at the suture between the palatine and ectopterygoid.

### 4.18. Pterygoid

As usual in most dicynodonts the pterygoid has three parts: the anterior ramus, the median pterygoid plate, and the quadrate ramus.

Both pterygoids are distinguishable and do not meet medially (see Remarks above), contrary to the condition observed in *K. hitchingi* (*Angielczyk et al.*, 2019) but similar to the condition in *Cistecephaloides* (*Cluver, 1974a*). The pterygoids suture through interdigititation with the ectopterygoids anteriorly, they are overlain by the parabasisphenoid complex dorsally, and the posteriormost lateral wall of the quadrate ramus of the pterygoid contacts the medial facet of the quadrate.

The anterior ramus is indented by the ectopterygoid medially, but it is straight as in *K. hitchingi*, *Dicynodontoides*, and *Compsodon* (Cox, 1959; Angielczyk and Kammerer, 2017; Angielczyk et al., 2019). It does not broaden anterolaterally as in *Pristerodon* or *K. hitchingi* (*Angielczyk et al.*, 2019; Macungo et al., 2022), but resembles more the condition in *Sauropscaptor* and *Myosaurus* (Kammerer et al., 2016; Macungo et al., 2022). The anterior ramus of the pterygoid has a subtriangular ventral keel anteriorly (vkpt, ventral keel of the pterygoid, Fig. 5), as *K. hitchingi* (*Angielczyk et al.*, 2019), presumably where part of the pterygoideus musculature would have inserted. The ventral keel is angled anterodorsally. There is no median pterygoid plate as the specimen is preserved but the medial aspect of the ventral surface of the pterygoids form a ventrally-directed crest, the crista oesophagea (co, Fig. 5). The pterygoid portion of the crista oesophagea is parallel to its contralateral along most of its anteroposterior length in opposition to *K. hitchingi*, *Pristerodon*, *Cistecephalus* and *Myosaurus* (*Angielczyk et al.*, 2019; Macungo et al., 2022; Broili and Schröder, 1935; Brink, 1950; Keyser, 1973). These crista oesophagea have a small acute posterior process on the ventral aspect of the bone that are separate from each other even if the contact between the pterygoids would be forced (ppco, Fig. 5A,D, 6). The angle between the anterior ramus and the quadrate ramus is ~90–105°. The quadrate ramus is blade-like and subtriangular in shape, possessing a dorsally-directed crest near the median pterygoid plate. The ventral border of the quadrate ramus is incipiently expanded medially. The lateral surface of the quadrate ramus is concave and forms a subtriangular recess (srpt, subtriangular recess of the pterygoid, Fig. 5F).

### 4.19. Epipterygoid

Portions of both epipterygoids are preserved. Only the footplate and the dorsalmost portion of the left epipterygoid are preserved. Most of the ascending ramus and dorsal end of the right epipterygoid also are present, but the footplate is not preserved on that side. The epipterygoid articulates with the descending flanges of the parietals. The epipterygoid footplate contacts the dorsal aspect of the quadrate ramus of the pterygoid. The dorsal portion of the ascending ramus of the epipterygoid is widely expanded anteroposteriorly, resulting in a subrectangular shape (sep, Fig. 4), which steeply tapers ventrally into the ascending ramus (arep, Fig. 4), in contrast with the slightly less expanded dorsal portion in *Niassodon* (Castanhinha et al., 2013). The dorsal portion of the *Diictodon* epipterygoid is not expanded (Sullivan and Reisz, 2005). The ascending ramus is subcircular in cross-section. Although broken in several parts, the ascending ramus of the epipterygoid is straight or bows slightly anteriorly. The epipterygoid footplate is not expanded and conforms to the dorsal aspect of the quadrate ramus by curving posteriorly, in contrast with the bowed footplate in *Diictodon* (Sullivan and Reisz, 2005).

### 4.20. Parabasisphenoid

The parabasisphenoid is a compound bone composed of a dermal parasphenoid and likely two basisphenoidal ossification centers (Araújo et al., 2017). In *K. yajuwayeyi*, as in other dicynodonts, it seems that the parasphenoid coossifies with the basipresphenoid, and more posteriorly, articulating with the basioccipital is the basipostsphenoid (Araújo et al., 2017). The parasphenoid rostrum and basipresphenoid are laid between the pterygoids (pshr, Fig. 5E). This region in lateral view has a subtriangular shape with the anterior portion being taller and swiftly tapering posteriorly. As preserved, the pterygoids do not meet medially,
the parasphenoid-basipresphenoid is visible ventrally, similar to *Cistecephaloides*.

The basipostsphenoid region, contrary to the condition of *Niassodon* (Castanhinha et al., 2013), contains the carotid foramina, which adjoin dorsally to form the base of the cerebral carotid pathway. The two carotid foramina are visible dorsally (Surkov and Benton, 2004) and ventrally but are not displayed along the same coronal axis, thus being asymmetrical probably due to taphonomical distortion. The carotid foramina are subcircular. The sella turcica is dished as in *Niassodon* (Castanhinha et al., 2013), ellipsoid, and located posterior to the carotid foramina. It is posteriorly delimited by a crest-like dorsum sellae that separates it from the basioccipital, in contrast with the relatively flat sella turcica and absence of a dorsum sellae in *Diictodon* (Surkov and Benton, 2004; Sullivan and Reisz, 2005). Thin lateral walls of the basi-sphenoid continue to form the pila antoticae of the prootic and are probably homologous to the clinoid processes. No tuberculum sellae is present as the basipostsphenoid continues seamlessly towards the parasphenoid + basipresphenoid complex.

### 4.21. Sphenethmoid

The sphenethmoid is not preserved in *K. yajuwayeyi*; therefore, reliable boundaries for segmenting the ventral portion of the brain endocast are difficult to establish.

### 4.22. Basioccipital

The basioccipital is a structural bone of the occipital plate, contacting the parabasisphenoid anteriorly, the prootics anterolaterally, the opisthotics laterally, and the exoccipitals posterolaterally (Fig. 8). The basioccipital condyle is poorly preserved; therefore, its original shape cannot be determined. The dorsal surface of the basioccipital is shallowly concave with lateral crests rising dorsally forming the dorsal walls of the oval window that fade at the level of the prootic contact. The contact of the prootic is oblique and the contact with the parabasisphenoid follows the coronal axis, thus giving a subtrapezoidal shape to the anterior borders of the basioccipital, as in *Myosaurus* (Macungo et al., 2022), but distinct from the relatively straight contact as in *Diictodon* and *Niassodon* (Castanhinha et al., 2013; Sullivan and Reisz, 2005). There is an unissued zone between the basioccipital and the basipostsphenoid (Supplementary Information in Morphobank). In ventral view, the basioccipital condyle is better preserved possessing a subtriangular shape that steeply slopes into a flat anterior portion of the ventral basioccipital floor. The ventral basioccipital floor is flanked by two ventrally sloping basioccipital tubera that flow onto the basi-sphenoidal tubera. However, this region is hard to discern due to poor preservation. There is no ventromedial ridge as in *Myosaurus* (Macungo et al., 2022).

### 4.23. Stapes

The stapes is not preserved in *K. yajuwayeyi*.

### 4.24. Quadrate

Although the periosteum is better preserved on the left side, both quadrates are complete. The quadrate sits in a deep excavation on the anterior surface of the squamosal. The quadrate-quadratojugal form a complex because the ventral crest-like portion of the quadratojugal isossified with the dorsal surface of the lateral condyle. The quadrate in *K. yajuwayeyi* has an inverted Y-shape. The tips of the Y-shape correspond to the trochlea (tr, Fig. 8) composed of lateral and medial condyles (mcq, lcq, Fig. 8), separated by an intercondylar groove (igq, Fig. 6). The single tip of the inverted Y forms the dorsal plate (dpq, Fig. 8). In contrast to *Kawingasaurus* and *Cistecephaloides*, the articular condyles are easily distinguishable (Cluver, 1974a; Laaß, 2015). The

lateral condyle is longer than the medial condyle, but the medial condyle is mediolaterally thicker. Whereas the lateral condyle is slightly convex ventrally, the medial condyle is straight. A small anteriorly-directed flange (afmcq, anterior flange of the medial condyle of the quadrate, Fig. 8) rises from the dorsal border of the medial condyle. The intercondylar groove is broad and well defined, and uniformly thick anteroposteriorly. The intercondylar groove is distinguished from that of *Niassodon* and *Endothiodon tolani* by being strongly angled in *E. tolani* (Castanhinha et al., 2013; Cox and Angielczyk, 2015), rather than smooth. In ventral view, the quadrate has a convex anterior border and concave posterior border, whereas both lateral and medial borders are convex. The dorsal plate has a rounded ellipsoidal dorsal border, which curves laterally. Near the contact between the medial condyle and the dorsal plate, a broad recess hosts the lateral aspect of the quadrate ramus of the pterygoid. On the opposite lateral side, a more deeply excavated recess, together with the ventral rod of the quadratojugal, forms a subcircular quadrate foramen. The lateral aspect of the quadrate dorsal plate is concave and the medial aspect is convex.

### 4.25. Quadratojugal

The distinction between the quadratojugal from the squamosal is particularly difficult to delineate. The quadratojugal is a plate-like element (pqj, Fig. 8) that tapers into a crest-like ventral process (vpqj, Fig. 8), which fuses to the dorsal aspect of the lateral condyle of the quadrate. The ventral process crest extends anteroposteriorly, closely resembling the condition in *Niassodon* (Castanhinha et al., 2013). The quadratojugal twists slightly and expands dorsally to fit the anterior aspect of the squamosal; however, the shape of this plate-like portion is not possible to determine due to poor preservation.

### 4.26. Postparietal (“interparietal”)

The postparietal location and shape is closest to *K. kitchingi* in that it forms a considerable portion of the median dorsal aspect of the occipital plate. A noticeable gap occurs between the dorsal border of the supraoccipital and the ventral border of the postparietal, which appears to form two small ellipsoidal fenestrae (ef, Fig. 8). These ellipsoidal foramina are separated by a short blunt median process (mppa, median process of the postparietal, Fig. 8). In anterior view, a dorsally convex rim separates the median process of the postparietal (arp, anterior rim of the postparietal, Fig. 8), also present in *K. kitchingi*. The posterior surface of the postparietal is smooth and flat as there is no nuchal crest as in *K. kitchingi* (Angielczyk et al., 2019), but this could be a preservational artifact. The preserved anatomy points to a different condition than that seen in the *Sauroscaptor* condition, bearing a bipartite nuchal crest (Kammerer et al., 2016). On the other hand, there are two subparallel crests on the anterior surface of the postparietal (apc, anterior postparietal crests, Fig. 5), which are confluent with those of the parietal and supraoccipital. These crests are long and thin, possessing the same ventral depth throughout their anteroposterior length.

### 4.27. Tabular

The tabulars are very poorly preserved and their shape is not determinable, although small fragments are located on the anterodorsal region of the occipital plate. However, the identity of these bone fragments should be considered cautiously as the tabulars are often absent in cistecephalids (Angielczyk et al., 2019).

### 4.28. Supraoccipital

The right side of the supraoccipital is nearly complete only missing the dorsal region of the lateral process, whereas the left side of the supraoccipital is missing most of the lateral process. The lateral contact with the squamosal is mostly missing, with only the ventralmost region
near the posttemporal fenestra remaining, where it lightly touches the opisthotic. The supraoccipital forms a central portion of the occipital plate, including the dorsal border of the foramen magnum and post-temporal fenestra. The posttemporal fenestra is particularly large compared to other cistecephalids and is ellipsoidal in shape with the major axis oriented along the horizontal axis, whereas in *Niassodon* it is subcircular (Castanhinha et al., 2013). The dorsal median lobe of the supraoccipital is not present in *K. yajuwayeyi* as well as *K. kitchingi* (Angielczyk et al., 2019), contrary to *Niassodon* and *Pristerodon* (Castanhinha et al., 2013; Macungo et al., 2022).

Most of the anatomical structures of the supraoccipital are present on the anterior surface. The supraoccipital forms the posterior part of the floccular fossa (present, see Surkov and Benton, 2004). A transverse crest represents the continuation from the postparietal (supraoccipital transverse crest, stc, Fig. 8). The anterior region of the supraoccipital contacting the prootic and opisthotic is particularly complex. It possesses a mediolaterally-oriented crest from the dorsal border of the foramen magnum, which makes the suture between the prootic and supraoccipital (spcc, supraoccipital-prootic coronal crests, Fig. 8A and B). These are in turn well defined by two depressions immediately posterior to the crest: the supraoccipital-opisthotic lateral recess (slr, Fig. 8A and B), and lateral to it the prootic-supraoccipital recess (psr, Fig. 8A and B). The supraoccipital-prootic coronal crests are present in *Myosaurus* and *Pristerodon* (Macungo et al., 2022). The floccular fossa is formed by the opisthotic and prootic and possesses a nearly perfect spheroidal shape (ff, floccular fossa, Fig. 8). Dorsal to the floccular fossa is a strongly excavated fossa, the supraoccipital lateral recess. This recess is medially subcircular, but precipitously opens laterally into a subtriangular, shallow excavated area. The supraoccipital lateral recess is flanked by the supraoccipital transverse crest, which is markedly angled medially, but fades laterally. However, poor preservation of the lateral extent does not allow a complete determination of the rest of its anatomy.

### 4.29. Exoccipital

The exoccipital, as in many dicynodonts, is composed of a dorsal component and an occipital component, the latter contributing to the occipital condyle (Fig. 8). The exoccipital contacts the supraoccipital dorsally, the opisthotic laterally, the basioccipital ventrally, and the contralateral exoccipital medially. The occipital component is bulbous and somewhat D-shaped, with the flat part of the 'D' rotated to the foramen magnum. A single hypoglossal foramen lies at the transition between the occipital component and the dorsal component. This foramen is subcircular and exits at the jugular foramen. The dorsal component is subtriangular in posterior view and forms the dorsal border of the jugular foramen. It is significantly proportionately smaller compared with that of *Kawingasaurus*. It differs from that of *Myosaurus* in which it is subrectangular, and from *Pristerodon* in which it is hourglass-shaped (Macungo et al., 2022). The exoccipitals do not contribute to the post-temporal fenestra.

### 4.30. Opisthotic

The opisthotic forms the ventromedial part of the occipital plate, being most visible posteriorly by the strong paroccipital process. The opisthotic forms the ventral border of the posttemporal fenestra and the dorsal border of the jugular foramen (jf, jugular foramen, Fig. 8). The paroccipital process has a somewhat hourglass shape, oriented horizontally. Therefore, the dorsal and ventral border are strongly concave and the lateral contact with the squamosal is simple along a convex suture. A short posterior projection, not well preserved on the left side, is present on the posterolateral corner of the paroccipital process; the tympanic process. This posteriorly-directed projection differs from *Myosaurus*, *Pristerodon*, and *Kawingasaurus* as in these taxa it projects vertically (Macungo et al., 2022). The opisthotic posterior surface is

convex medially, but forming two dorsoventrally-divergent crests (odc, opisthotic divergent crests, Fig. 8) towards the lateral side of the bone. These crests bound a posteriorly concave subtriangular recess (osr, opisthotic subtriangular recess, Fig. 8). The presence of this sub-triangular excavation bounded by the dorsoventrally-diverging crests is the most striking difference from *Myosaurus* and *Pristerodon* (Macungo et al., 2022). Although this morphology vaguely resembles *Kawingasaurus* and *K. kitchingi* (Angielczyk et al., 2019; Macungo et al., 2022), the condition in *K. yajuwayeyi* is significantly more pronounced as preserved. The opisthotic forms most of the bony cover for the lagena and vestibule of the endosseous labyrinth (Supplementary Information in Morphobank).

### 4.31. Prootic

Although fused with the opisthotic in several dicynodont taxa (e.g., Angielczyk et al., 2019), the prootic sutures are discernible in *K. yajuwayeyi*. Notably, the periotic does not contact the parietal (Surkov and Benton, 2004). The prootic is formed by an alar component (acp, alar component of the prootic, Fig. 8) that supports the pila antotica (pa, pila antotica, Fig. 8). The prootic alar component is subtriangular in lateral view with a broadly convex surface. The angle between the anterior border of the alar component and the pila antotica is slightly obtuse and the resulting recess forms the trigeminal notch. The trigeminal notch is deeply excavated, contrary to the pylaecephalid *Diictodon*, which has a straight anterior border of the prootic (Sullivan and Reisz, 2005; Surkov and Benton, 2004). The pila antotica is long and anterodorsally directed, with a broad base and two faint anterior and posterior crests delimiting it (pac, pila antotica crests, Fig. 8), thus forming an acute subtriangular recess (pasr, pila antotica subtriangular recess, Fig. 8). The pila antotica is readily distinguished from that of *Myosaurus*, which is anteroposteriorly broad, possesses a sigmoidal dorsal edge, the angle between the alar component and the pila antotica is narrower, and two anterior crests occur at the base of the pila antotica (Macungo et al., 2022). The prootic can be readily distinguished from that of *Pristerodon* in that the alar component is marked by a thin and anteriorly directed dorsal process, the prootics are overall significantly more robust, two crests occur at the base of the posterior edge of the pila antotica, and a well-pronounced bulge occurs on the lateral aspect of the prootic, while this bulge is significantly less pronounced in *K. yajuwayeyi* (Macungo et al., 2022). The pilae antoticae bow laterally in *K. yajuwayeyi*.

### 4.32. Endosseous labyrinth

The most distinguishing feature of the *K. yajuwayeyi* endosseous labyrinth is the prominence of the vestibule (Fig. 9). However, it does not reach the condition seen in *Kawingasaurus*, in which the vestibule is so inflated it nearly touches all the semicircular canals (Laaß et al., 2017). All semicircular canals in *K. yajuwayeyi* are ellipsoidal, but the horizontal canal has the highest eccentricity. The eccentricity of the anterior semicircular canal is 1.90, the posterior semicircular canal is 2.38, and 2.78 for the horizontal semicircular canal. The posterior semicircular duct is the thickest. The anterior semicircular canal duct is 618 µm in diameter, the posterior semicircular canal is 720 µm, and horizontal semicircular canal is 396 µm.

The anterior semicircular canal is slightly sigmoidal in dorsal view and the posterior semicircular canal is slightly inflated at midlength as seen in other dicynodont taxa (Angielczyk et al., 2016; Araújo et al., 2018). As in various dicynodont taxa the crus communis (Laaß, 2015, Angielczyk et al., 2016; Benoit et al., 2017; Araújo et al., 2018) is somewhat triangular. Importantly, all semicircular canals have developed ampullae. This is a unique feature of *K. yajuwayeyi*, which is not shared with any other endosseous labyrinths from other dicynodonts (Araújo et al., 2018). *Kawingasaurus*, *Emydops* and *Eodicynodon*, however, have a slightly developed horizontal semicircular canal ampulla
<figure><img src="image_14.png" /><figcaption>**Fig. 9.** – Endosseous labyrinth of *K. yajuwayeyi*. A –orthogonal view of the horizontal semicircular canal; B – orthogonal view of the posterior semicircular canal; C – lateral view of the endosseous labyrinth; D – orthogonal view of the anterior semicircular canal. Orthogonal views of the three semicircular canals were taken to facilitate measurements. Abbreviations: aa – anterior ampulla; ascc – anterior semicircular canal; cc – crus communis; ha – horizontal ampulla; hscc – horizontal semicircular canal; pa – posterior ampulla; pscc – posterior semicircular canal; v – vestibule.</figcaption></figure>

(Fourie, 1993; Laaß, 2015; Benoit et al., 2017).

# 5. Discussion

## 5.1. Affinities with Kembawacela kitchingi

The taxonomic kinship between *K. yajuwayeyi* and *K. kitchingi* has already been demonstrated by the phylogenetic analysis in Macungo et al. (2022), and throughout the description above various similarities have been noted (e.g., presence of ovoid depressions in the palatal component of the maxilla, foot-like ventral portion of the jugal). However, there are important differences between *K. yajuwayeyi* and *K. kitchingi*. Important potential confounding factors that have to considered to fully address the anatomy of *K. yajuwayeyi* and *K. kitchingi* is taphonomic deformation and intraspecific variation.

DMMM-PK-16-1 suffered mostly dorsoventral compression, whereas the best-preserved *K. kitchingi* specimen (NHCC LB18) suffered ante roventral shear. Such distinct taphonomic distortion modes could have impacted significantly interpretation such that the specimens would have similar anatomy if undeformed. Despite some features being affected by dorsoventral compression (e.g., nearly dorsal orientation of the orbits, height of the semicircular canals), which were not used for diagnosis, others could either not be affected by this mode of deforma tion, or would not have resulted in the observed anatomy. For instance, dorsoventral compression in *K. yajuwayeyi* would have resulted in a dorsoventrally shorter ventral portion of the jugal, not taller when compared to *K. kitchingi*, or the dorsoventral compression would potentially further lateral exposure of the ascending process of the jugal, but not complete occlusion by the descending process of the postorbital in *K. yajuwayeyi*. Analogously, the nature of the relationship between the maxillary canal and the maxillary antrum was not likely influenced by the taphonomic pattern displayed in DMMM-PK-16-1. An alteration of the relationship between the maxillary canal and antrum to show the pattern in *K. kitchingi* could have only been produced by lateral shearing of the skull, not dorsoventral compression. Nevertheless, we refrain to draw many conclusions on the maxillary antrum and maxillary canal morphology, as the inter- and intra-specific variation of these structures is only poorly known for a few dicynodonts (Benoit et al., 2018).

On the other hand, although we acknowledge that the presence of separate pterygoids could have been exacerbated by dorsoventral

compression, if the pterygoids are forced together at the midline (Fig. 6D), the result would be a much more anteroposteriorly long pterygoid median plate than observed for any *K. kitchingi* specimen. Importantly, disjunct pterygoids have already been described in the cistecephalid *Cistecephaloides* (Cluver, 1974a), which has not suffered dorsoventral compression. Disjunct pterygoids may be a feature more common in cistecephalids than previously thought. This type of tapho nomic distortion could also have influenced the morphology of the paired ellipsoidal foramina between the supraoccipital and postparietal. These structures are also visible in the holotype of *K. kitchingi*, more so on the left side than the right side. Due to taphonomical deformation and the nature of the contact between the postparietal and the supraoccipital the posterior exposure of these foramina seems to have been signifi cantly emphasized in DMMM-PK-16-1.

## 5.2. Cistecephalid brain endocast

The ventral aspect of the frontal denotes part of the brain endocast of *K. yajuwayeyi* (Fig. 10). The parietal ovoid recesses (por, Fig. 4) are followed by the frontal ellipsoid excavations (fee, Fig. 4) anteriorly. These significant depressions would give the brain endocast a shape similar to that in *Kawingasaurus* (Laaß and Kaestner, 2017) and *K. kitchingi* BP/1/3337 (Angielczyk et al., 2019). In *Kawingasaurus* the forebrain is bulged and compact, separated from each contralateral hemisphere by a conspicuous median sulcus (Laaß and Kaestner, 2017). Additionally, the olfactory bulbs are in close proximity to the forebrain (Laaß and Kaestner, 2017). These structures are visible mostly on the supraoccipital, which implies a severe retraction of the brain posteriorly. On the other hand, the shallowly excavated areas in the ventral aspect of the parietal in *K. yajuwayeyi* and *K. kitchingi*, bounded laterally by the parietal flanges, indicate where the forebrain was placed. A very faint but still visible median ridge would have divided the two hemispheres (mrp, Fig. 3). The olfactory bulbs would have fitted in the frontal ellipsoid excavations in *K. yajuwayeyi* and *K. kitchingi*. The olfactory tract would have developed anteriorly in the anterior ovoid recesses of the frontal (aorf, Fig. 3). This anatomy of the ventral aspect of the skull roof is similar to that of *Kawingasaurus* except that a larger portion of the olfactory tract endocast is preserved and the loci of contact of these brain regions has shifted significantly posteriorly.

Overall, the brain endocasts of *Kawingasaurus*, *K. kitchingi* and
<figure><img src="image_15.png" /><figcaption>**Fig. 10.** – Brain endocast of *K. yajuwayeyi*. A – right lateral view, B – right lateral view with the brain endocast transparent showing the relationship with the parietals and frontals, C – ventral view, D – ventral view showing the relationship of the brain endocast and the frontals and parietals, E – dorsal view. Abbreviations: mo – medulla oblongata, ce – cerebellum, fb – forebrain, ob + ot olfacotory bulb and tract, ponf – pontine flexure, en –epiphyseal nerve.</figcaption></figure>

*K. yajuwayeyi* are remarkably different from those of other dicynodonts not only in that the brain is overall more compact (*Castanhinha et al., 2013; Simão-Oliveira et al., 2020*), but also the forebrain is in close proximity to the olfactory bulbs (*Fig. 10*). Such anatomy is not only peculiar to *Kawingasaurus* but seems to be common to reported cistecephalids. *Kawingasaurus*, with the significant retraction to the forebrain to the supraoccipital region, is an even more derived condition relative to the intermediate more anteriorly positioned forebrain region in *K. yajuwayeyi* and *K. kitchingi* (*Fig. 10*). Whether unusual posterior positioning of the forebrain actually represents an analogous neocortex-like structure (*Laaß and Kaestner, 2017*) remains conjectural. The reorganization of the cistecephalid skull could have imposed architectural constraints to accommodate the brain. Particularly, in cistecephalids, the squared profile of the occipital plate, the reorientation of the occipital plate relative to the skull roof, and the reorientation of the orbits to accommodate forward-directed vision may have constrained the positioning of the brain within the brain cavity. This might be a more plausible explanation than the development of an entire *de novo* forebrain structure in a restricted highly-specialized clade of therapsids.

Mechanistically, the effects of the reorientation of the occiput among cistecephalids, has almost certainly played a major role in shaping the gross anatomy of the brain. With evolutionary reorganization of the skull's braincase, possibly linked to fossorial adaptations observed in

cistecephalids (Macungo et al., 2022), the dura mater became extremely thin in this clade. Therefore, the imprints of the brain on the ventral aspect of the skull roof became more visible as seen in *Kawingasaurus*, *K. kitchingi* and *K. yajuwayeyi*, than in other dicynodonts. We can rule out miniaturization as a driver to the peculiar morphology of the brain endocast in cistecephalids because, for example, the small-sized endothiodontid *Niassodon* (*Castanhinha et al., 2013*) is a miniaturized dicynodont taxon that possesses the typical brain endocast anatomy of dicynodonts.

### 5.3. Endosseous labyrinth and the inflated vestibule

The ampullae of each semicircular canal are well developed in *K. yajuwayeyi* (*Fig. 9*), contrary to other dicynodonts in which inner ear anatomy is known (Araújo et al., 2018). Despite large ampullae being described for *Myosaurus* (Cluver, 1974b) and other dicynodonts serially sectioned by Olson (1944) including *Brachyprosopus* (Angielczyk et al., 2016), this condition needs to be ascertained with micro-computed tomography. From what is known from micro-computed tomography renders of the inner ear endocast, the condition in *K. yajuwayeyi* is not only unusual among dicynodonts but also among multiple lineages of non-mammalian synapsids (RA pers. observation). As with the brain endocast, the unusual development of these structures may simply be related to architectural constraints resulting from extreme confinement
of the sensory system to an enclosed space correlated with the suite of
fossorial adaptations. Once again, despite *Niassodon* and *Emydops* being
miniaturized dicynodonts, they do not possess well-developed ampullae
(Fourie, 1993; Castanhinha et al., 2013), and they do not possess the
suite of adaptations as seen in derived cistecephalids for a fossorial
lifestyle (e.g., Macungo et al., 2022). Nevertheless, it is important to
note that well-developed ampullae is a common feature for many living
tetrapod clades including birds, squamates, and mammals, but not in
crocodyliformes or testudines (Gray, 1907, 1908; RA pers. obs.).

5.4. Pila antotica and oculomotor musculature

The functional role of the pila antotica has been poorly explored in
dicynodonts, mostly because it is a small and delicate structure well-
hidden within the basicranium. However, from what is known in
various specimens, its morphology varies widely from an expanded
complex structure (e.g., *K. yajuwayeyi*), to a rod-like structure (e.g.,
*Niassodon*), to absent in some Triassic dicynodonts (*Surkov and Benton,
2004*). In reptiles the pila antotica is typically described as a rod-like
component of the chondrocranium, posterior to the pila metoptica,
which attaches dorsally to the pila accessoria, eventually reaching the
planum supraseptale (e.g., *Bellairs and Kamal, 1981*, Paluh and Sheil,

2013). The pila antotica ossifies at its base in some reptiles (e.g., Säve-Söderbergh, 1946; Oelrich, 1956; Rieppel, 1980, Paluh and Sheil, 2013) but also in monotremes, and importantly, in multiple mammalian forerunner lineages (Olson, 1944). In monotremes it is a highly atrophied projection of the cranial base (Crompton et al., 2017). To our knowledge no function has been associated with the pila antotica in these taxa. However, an ossified pila antotica is known to serve as an attachment area for the levator bulbi muscles in anguimorph lizards and various archosaurs (Rieppel, 1980; Clark et al., 1993), and the base of the pila antotica serves as an attachment area of the retractor bulbi musculature in *Sphenodon*, *Varanus*, and *Lacerta* (Säve-Söderbergh, 1946). In *K. yajuwayeyi*, the region between the pila antotica and the alar portion of the prootic probably served as attachment for the prootic membrane as in *Ctenosaura* and various other tetrapods (Oelrich, 1956). This is a level II inference according to Witmer (1995).

The complex anatomy and solid ossification of the pila antotica in *K. yajuwayeyi* as well as in other dicynodonts (Olson, 1944; Macungo et al., 2022) renders this structure as more than delimiting the trigeminal ganglion and its nerve. The ventral and dorsal crests that are visible on the lateral aspect of the pila antotica in *K. yajuwayeyi* and *Kawingasaurus* (Macungo et al., 2022) appear to increase the surface area for muscle attachment or increase structural support or both. The

<figure><img src="image_16.png" /><figcaption>Fig. 11. – Soft-tissue reconstruction of the maxillary antrum region, the lateral palatal foramen and palatine foramen. A – medial view, B – ventral view, C – dorsal view. Abbreviations: ia – infraorbital artery, gpn + pa – greater palatine nerve and palatine artery, lg – lacrimal gland, lpn – lesser palatine nerve, lpf – lateral palatal foramen, paf – palatine foramen, sa + pn – sphenopalatine artery and pterygopalatine nerve.</figcaption></figure>
oculomotor function (i.e., eye movement) could have been assured in part by site of attachment at the pila antotica, as in other vertebrates (Säve-Söderbergh, 1946; Oelrich, 1956). Many features of dicynodont soft-tissue anatomy are remarkably reptilian (Castanhinha et al., 2013), so conservation of the oculomotor function is plausible. It is, nevertheless, somewhat surprising to observe that Triassic dicynodonts do not possess an ossified pila antotica (Surkov and Benton, 2004). Pending firm confirmation of this condition using micro-tomography scans in well-preserved specimens, it can imply that the support for oculomotor muscles becomes cartilaginous in these derived taxa.

## 5.5. Nasolacrimal canal and exocrine glands

In *K. yajuwayeyi* a small cavity contiguous from the maxillary antrum (or sinus) forms a small chamber within the lacrimal (Figs. 7 and 11). The nasolacrimal canal provided fluids directly to the canthus from subconjunctival ocular glands. This structure is virtually universal in tetrapods, with the exception of turtles, some salamanders, and occasionally mammals (Hillenius and Rehorek, 2005; Siegel et al., 2018; Rehorek et al., 2010, 2018). To our knowledge, the function in anomodonts of this detailed anatomy has not yet been resolved. This region of the skull, immediately anterior to the orbit, typically comprises parts of the exocrine system (Hillenius, 2000; Hillenius and Rehorek, 2005). Due to its location, we can rule out maxillary canal or respective sinuses (Benoit et al., 2016, 2019), as they are enclosed entirely by the maxilla. Meibomian glands can also be ruled out as they are typically palpebral (Tiffany, 1987).

Three glands of the exocrine system can be hypothesized to be hosted by the lacrimal chamber: Harderian glands, lacrimal glands, and a vomeronasal organ. The vomeronasal organ is typically located in the nasal capsule area in mammals and their predecessors as well as in squamates (Hillenius and Rehorek, 2005), more anteriorly than the preserved portion in *K. yajuwayeyi*. This would, therefore, be a Level III inference (Witmer, 1995) with no phylogenetic support. However, in squamates and caecilians the secretions from the lacrimal gland pass through the nasolacrimal canal and then onto the vomeronasal organ (Wake, 1985; Rehorek et al., 2000). Therefore, an intermediary function of the lacrimal chamber with the vomeronasal organ cannot be ruled out entirely.

The Harderian glands are not universally present in mammals, being atrophied or even absent in some primates, bats, and dolphins (Rehorek et al., 2010, 2018). Harderian glands are structures associated with maintenance of insulatory pelage in extant mammals (Harriman and Thiessen, 1983; Harlow, 1984; Lingham-Soliar, 2014). They also serve a wide variety of other functions such as extraretinal photoreception, pheromone production, regional immune response of the upper respiratory tract, extrarenal salt excretion, association to the vomeronasal sense, and even digestion (see review by Hillenius and Rehorek, 2005). The Harderian gland is located medial to the eyeball in squamates, birds, crocodiles, and mammals (Ali et al., 2019). However, these glands are not connected directly to the nasolacrimal canal (Sakai, 1992), although some authors argue that the ancestral path of the Harderian gland used this canal (Hillenius and Rehorek, 2005). Given the conservative pattern of the location and absence of nasolacrimal duct usage by the Harderian gland by most tetrapods it seems safe to assume that the lacrimal chamber was not used to host this gland.

The lacrimal glands secrete mucous or seromucous fluids to the eyes in tetrapods (Ali et al., 2019). The lacrimal glands can either supply conjunctival fluid by glands that are located ventral (e.g., Barone et al., 1973) or dorsal (as in humans), to the eyeball in various mammalian species and reach the eye by the nasolacrimal canal (Sakai, 1992). These lacrimal glands typically feed the outer canthus of the eye (Sakai, 1992). The nasolacrimal duct is divided into three regions: a palpebral portion posteriorly, a bony portion that forms the nasolacrimal canal, and a membranous portion, unsupported by bone that eventually reaches the vomeronasal organ (Ali et al., 2019). The infraorbital artery would have

passed alongside the nasolacrimal duct through the nasolacrimal canal (Oelrich, 1956; Porter and Witmer, 2015). The lacrimal gland seems to have bony support in *K. yajuwayeyi* (Figs. 7 and 11), and is the best candidate to be the soft-tissue supported by the lacrimal chamber. The lacrimal gland was enveloped by the maxilla anteriorly and laterally, and prefrontal, lacrimal and jugal posteriorly.

## 5.6. Palatine foramen and lateral palatal foramen functions

The palatine foramen and the lateral palatal foramen are two important conspicuous structures of the dicynodont palate (exceptions for some emydopoids, for example, see Angielczyk, 2019). However, the function of these structures has not yet been thoroughly discussed in the literature, given the new light shed by recent microcomputed-tomography anatomical, dual-vascular injection, or contrast enhancing studies that provide valuable insights into the vascular and nervous systems in multiple extant taxa. Previously, Klaauw and Roon (1942) and Cox (1968) suggested that the palatine artery passed through the interpterygoid vacuity (a much more posterior structure relative to the palatine foramen) but this posterior branching is not consistent with recent anatomical studies of the cranial vasculature in reptiles and mammals, and would necessarily result in a Level III inference according to Witmer (1995) rationale. Importantly, Cluver (1971) discusses these structures for *Lystrosaurus* and states that the lateral palatal foramen served for the passage of a trigeminal nerve branch. Although this statement is bracketed phylogenetically (Level I inference), it is not clear which branch of the trigeminal passed through the lateral palatal foramen.

The palatine artery is a branch of the infraorbital artery (Porter and Witmer, 2015; Netter, 2019; Singh, 2018), which passes through the nasolacrimal canal. In crocodiles it is the supraorbital + ophthalmotemporal artery that passes through the nasolacrimal canal (Sedlmayr, 2002). The nasolacrimal canal opens into the maxillary antrum that hosted the lacrimal gland (see above) plus the maxillary sinus that would have given rise to ramifications of the maxillary canal and alveolar rami anteriorly (Benoit et al., 2016, 2018, 2019). In *K. yajuwayeyi*, the infraorbital artery likely travelled medially to form the palatine artery (Sedlmayr, 2002; Porter and Witmer, 2015, Netter, 2019; Singh, 2018), the infranasal artery as in Oelrich (1956), as it enters through the lateral palatal foramen dorsally. Together with the palatine artery, the greater palatine nerve (Netter, 2019; Singh, 2018) passes from a different path. The greater palatine nerve is a branch of the pterygopalatine nerve (Netter, 2019; Singh, 2018) that seems to have passed along a canal on the dorsal aspect of the palate slightly oblique to the median sagittal axis of the skull (Fig. 9). Along the median sagittal axis of the skull, the parasphenoid rostrum and the dorsal excavation of the vomer are delimited by crests that supported the septal cartilage (Oelrich, 1956). This canal supported both the pterygopalatine nerve and the sphenopalatine artery (Sedlmayr, 2002; Porter and Witmer, 2015), both passing through a vertical foramen at the level of the anterior orbital border. The pterygopalatine nerve branches to the lesser palatine nerve (Netter, 2019; Singh, 2018) or the intermediate palatine nerve (Oelrich, 1956) that passes through the palatine foramen.

The sphenopalatine artery continues onto the maxillary antrum where it likely anastomosed with the infraorbital artery (Sedlmayr, 2002; Porter and Witmer, 2015) to form the palatine artery and pass through the lateral palatal foramen (Fig. 9). These inferences are bracketed phylogenetically by widely disparate taxa and, therefore, seem to be extremely conservative among tetrapods, resulting in Level I inferences according to Witmer (1995).

## 5.7. Quadrate foramen

Homologizing the quadrate foramen in mammals is not possible as the quadrate is incorporated into the middle ear. This region changed radically in cynodonts (Luo, 2011). Therefore, the quadrate foramen in
dicynodonts can only be compared with reptilians *sensu lato*. In birds, the mandibular branch of the trigeminal nerve (CN V₃) passes dorsal to the quadrate through a notch (Jones et al., 2019). The slit-like quadrate foramen in *K. yajuwayeyi* and other dicynodonts could have served for the passage of CN V₃. The configuration of the dicynodont skull would imply a posteriorly-directed path of the CN V₃ from the Gassarian ganglion, unlike birds. On the other hand, in archosaurs and squamates, the paraquadrate foramen carries neurovasculature for irrigation and innervation of the maxillomandibular regions of the skull along the quadrate-quadratojugal junction, namely the tempororbital artery and vein (Sedlmayr, 2002; Hendrickx et al., 2015; Porter and Witmer, 2015). Similar neurovascular patterns are here hypothesized for *K. yajuwayeyi* and other dicynodonts.

## 6. Conclusion

This study proves yet again the value of advanced imaging techniques to the study of ancient life. Specifically, visualization of the skull of *K. yajuwayeyi*, concealed in dense matrix, allowed its detailed anatomical description, leading to the definition of a new species of cistecephalid. The erection of a new species from one of the East African Karoo basins further confirms the importance of these basins in shaping the understanding of phylogenetic and speciation patterns of dicynodonts. The growing evidence for species-level differences from the Karoo basin may be further supported with a growing number of Mozambican and Zambian fossils being prepared and studied that also seem to point to this direction.

## Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Data availability

Data is available in Morphobank Project P3810.

## Acknowledgements

Financial support was provided by the Museu Nacional de Geologia and by the Fundação para a Ciência e a Tecnologia (R.A. postdoctoral fellowship SFRH/BPD/96205/2013), FCT - AGA KHAN Development Network grant number 333206718, National Geographic Society grant number CP-109R-17. Fieldwork at Chiweta was supported by ISEM at SMU, Dallas, Texas. The experiment HG111 was performed on beamline BM05 at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. We are grateful to the staff of BM05 and Paul Tafforeau for providing assistance in using beamline BM05. Harrison Simfukwe of the Cultural and Museum Centre Karonga, Malawi, assisted with fieldwork. Dale A. Winkler and Diana Vineyard of Southern Methodist University (SMU), and Myria L. Perez of the Perot Museum of Nature and Science, Dallas, assisted in numerous ways. This study benefited from useful discussions with Michael J. Polcyn (SMU). Kenneth Angielczyk and Christian Kammerer provided extremely insightful comments on the dicynodont anatomy and systematics, and offered ideas on the current paleontological context during the review process. Two additional reviewers (Jörg Fröbisch and an anonymous reviewer) also made relevant suggestions that improved the article.

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