Azzabaremys moragjonesi Gaffney, Moody & Walker, 2001

Martín-Jiménez, Marcos & Pérez-García, Adán, 2025, The first neuroanatomical study of a marine pleurodire (the large Paleocene bothremydid Azzabaremys moragjonesi) reveals convergences with other clades of pelagic turtles, Fossil Record 28 (1), pp. 1-15 : 1-15

publication ID	https://doi.org/10.3897/fr.28.e130418
publication LSID	lsid:zoobank.org:pub:913406A6-5CC1-41EE-BE6D-440A9D8970A7
DOI	https://doi.org/10.5281/zenodo.14592329
persistent identifier	https://treatment.plazi.org/id/C1A2701A-877D-58CD-A930-0347F2BC9767
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scientific name	Azzabaremys moragjonesi Gaffney, Moody & Walker, 2001
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Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5

Type locality.

North of In Fargas, Samit, eastern Mali.

Horizon and depositional environment.

Shallow marine sediments of the Teberemt Formation, Paleocene (see Moody and Sutcliffe 1990, 1991, 1993).

Holotype.

NHMUK R 16370, corresponding to a complete skull without the mandible, being the only material currently known for this taxon (Figs 1 View Figure 1 , 2 View Figure 2 ).

Neuroanatomical description.

The cranial inner cavities (i. e., endocranial, nasal, and labyrinths), the canals of the carotid and anterior maxillary arteries, the canalis and sulcus cavernosus, and the canals of most nerves that cross the bones were completely reconstructed for this skull (Figs 1 C, D, F View Figure 1 , 2 C, D, F View Figure 2 , 3 View Figure 3 ). The canal of the abducens nerve (cranial nerve VI) cannot be observed due to the brightness of the sections in that area, and most of the canal of the vidian branch of the facial nerve (CN VII) is absent, because this nerve was not covered by bone. The anterior foramen for the exit of the glossopharyngeal nerve (CN IX) had not been observed.

The dorsal surface of the endocranial cavity forms an angle of 133.8 ° between the forebrain and the hindbrain (Fig. 3 C, D View Figure 3 ). The forebrain is slightly dorsally directed to reach the dorsal protuberance [dural peak sensu Evers et al. (2019) or cartilaginous rider sensu Werneburg et al. (2021)]. The olfactory bulbs are weakly developed (Fig. 3 A View Figure 3 ). The cerebral hemispheres are weakly expanded laterally, its width corresponding to 23.8 % of the total length of the endocranial cavity (Fig. 3 A View Figure 3 ). The ratio between the width of hemispheres and that of the medulla oblongata is 1.32. The dural peak is a dorsomedial protuberance of the endocranial cavity (Fig. 3 A, C, D View Figure 3 ), being bulbous and oval in dorsal view. This structure is relatively tall, being equivalent to 9.6 % of maximum height of the endocranial cavity. The peak represents 12 % of the total length of the endocranial cavity. The pituitary fossa is located ventral to the hemispheres (Fig. 3 B View Figure 3 ). This cavity is small and oval, being wider than long. The dorsal surface of the medulla oblongata descends to reach the foramen magnum (Fig. 3 C, D View Figure 3 ).

The sulcus that housed the olfactory nerve (CN I) is deep and wide. The olfactory nerve was long, equivalent to 44 % of the endocranial cavity length (Fig. 3 A View Figure 3 ). The nerve was posterodorsally directed and connected the nasal cavity with the olfactory bulbs region. The trigeminal nerve (CN V) exited from the endocranial cavity through the foramen nervi trigemini (Fig. 3 C, D View Figure 3 ). This foramen is a big oval-shaped opening, ventral to the cerebral hemispheres. The nerve reached the canalis cavernosus laterally. The anterior region of the canalis cavernosus is not covered by bone at the level of the trigeminal foramen (Fig. 3 A – C View Figure 3 ). Thus, it shows a gap between the canal and the sulcus cavernosus. Posteriorly, the canalis cavernosus contacts the canalis stapedio-temporalis, which is short and anterodorsally directed (Fig. 3 A View Figure 3 ). The sulcus cavernosus continues anteriorly ventral to the endocranial cavity (Fig. 3 A – C View Figure 3 ). The facial and the vestibulocochlear (CN VIII) nerves exited laterally to the endocranial cavity through two foramina located in the fossa acustico-facialis of the prootic (Fig. 3 A, B, D View Figure 3 ). This fossa is located posterior to the trigeminal foramen. The facial nerve reached the geniculate ganglion into the canalis cavernosus. The vidian branch of the facial nerve exited ventrally through a short canalis pro ramo nervi vidiani, and posteriorly entered the canalis caroticus internus (Fig. 4 B View Figure 4 ). The vidian nerve ran anteriorly without the presence of a canalis nervi vidiani and it anteriorly pierced the pterygoid by a small canal (Fig. 4 C View Figure 4 ). The nerve continued across the sulcus palatinopterygoideus. The distal hyomandibular branch of the facial nerve exited laterally from the canalis cavernosus (Fig. 3 B View Figure 3 ). The vestibulocochlear nerve entered the labyrinthic cavity to innervate the inner ear anteriorly (Fig. 3 D View Figure 3 ). The vagus (CN X) and the spinal accessory (CN XI) nerves crossed the foramen jugulare anterius and reached the recessus scalae tympani (Fig. 3 D View Figure 3 ). These nerves exited the skull posteriorly through the foramen jugulare posterius (Fig. 3 E View Figure 3 ). The foramen jugulare posterius is an opening separated by bone from the fenestra postotica. The distal region of the glossopharyngeal nerve crossed the skull through a canal from the recessus scalae tympani (Fig. 3 A – B View Figure 3 ). The canal splits and the nerve exited the skull by two foramina located in the opisthotic, between the foramen jugulare posterius and the fenestra postotica (Figs 3 E View Figure 3 , 5 View Figure 5 ). The hypoglossal nerve (CN XII) exited the endocranial cavity through a single foramen with a canal that bifurcates (Fig. 3 A, B View Figure 3 ). Two external foramina are observed for the right exoccipital but only a foramen is present in the left one (Fig. 3 E View Figure 3 ).

The nasal cavity of Azzabaremys moragjonesi is relatively enlarged (Fig. 3 A – D View Figure 3 ), being more than a half (54.2 %) the total volume of the cranial cavities (i. e., including the endocranial and the nasal cavities). The nasal opening is wide (Fig. 1 D – F View Figure 1 ) and the vestibulum of the nasal cavity is anteroposteriorly short (Fig. 3 C, D View Figure 3 ). The posterodorsal olfactory region of the nasal cavity is slightly expanded dorsally. The nasopharyngeal ducts are wide and short. They are posteriorly directed in a straight trajectory (Fig. 3 B View Figure 3 ).

The interorbital foramen is largely expanded in lateral view (Figs 1 G – I View Figure 1 , 2 G – I View Figure 2 ). The septum orbitotemporale is present in Azzabaremys moragjonesi , as in the rest of pleurodiran turtles. Until recently, this structure was identified as exclusive to Pleurodira . However, recent studies have shown that it is more widespread than previously reported, being present in other groups such as Paracryptodira and Trionychidae (e. g., Evers et al. 2020, 2021, 2023). The septum has a large opening that widely connects the orbital and temporal fossae (Fig. 3 E View Figure 3 ). The dorsal surface of the maxilla shows an anteroposteriorly directed sulcus crossing the ventral surface of the orbital fossa (Fig. 4 D View Figure 4 ). This sulcus enters the maxilla ahead of the level of the anterior margin of the orbit.

The inner ear cavity presents relatively robust semicircular canals (Fig. 3 F – I View Figure 3 ). They are slightly expanded dorsally. The anterior semicircular canal is the longest, displaying a wide anterior ampulla. The diameter of all semicircular canals is relatively wide (i. e., with a range between 2.53 and 3.37 mm, and a ratio between its maximum diameter and its length that varies from 0.37 to 0.63). The inner spaces formed by the semicircular canals and the vestibulum are oval, with a reduced diameter. The dorsal area of the anterior and posterior semicircular canals is at the same level than the dorsal surface of the crus communis, forming a horizontal surface (Fig. 3 F, G View Figure 3 ). Anteroposteriorly, the crus communis is very long. The angle formed between the vertical semicircular canals is acute, being 77 ° for the left inner ear and 77.4 ° for the right one (Fig. 3 H, I View Figure 3 ).

The carotid artery entered the skull through the foramen posterius canalis carotici interni, which is in the ventral surface of the pterygoid (Fig. 3 E View Figure 3 ). The artery ran into the canalis caroticus internus reaching the posterior end of the pituitary fossa (Fig. 3 B – D View Figure 3 ). The carotid canals form an angle of almost 89 ° (Fig. 3 B View Figure 3 ). The lateral canal for the palatine artery is absent. The arteria inframaxillaris crossed the ventral region of the septum orbitotemporale and continued anteriorly through the canalis infraorbitalis, located into the maxilla (Fig. 3 A-C View Figure 3 ). This canal bifurcates at the level of the nasopharyngeal duct. The anterior branch contained the nasal posterior artery, which irrigated the anteroventral region of the nasal cavity. The canalis alveolaris superior contained the alveolar superior artery, which also bifurcates, irrigating the lateral portion of the nasal cavity.