GAVIALOIDEA Hay, 1930

Zouhri, Samir, Gingerich, Philip D., Khalloufi, Bouziane, Bourdon, Estelle, Adnet, Sylvain, Jouve, Stéphane, Elboudali, Najia, Amane, Ayoub, Rage, Jean-Claude & Tabuce, Rodolphe, 2021, Middle Eocene vertebrate fauna from the Aridal Formation, Sabkha of Gueran, southwestern Morocco, Geodiversitas 43 (5), pp. 121-150 : 138

Superfamily GAVIALOIDEA Hay, 1930

Gavialoidea indet.

EXAMINED MATERIAL. — FSACBouj-401, 403 and 404, anterior and posterior portion of left maxilla; 407, posterior portion of a left maxilla; 402, mid-portion of a right maxilla. All these specimens are from the same individual. Also 405, portion of a left dentary.

DESCRIPTION

The reconstruction of the maxillae shows a slender snouted form with 16 preserved teeth but more teeth were probably present ( Fig. 7 L-N). The snout is wider than high and the palate is lower than the tooth row, so that the tooth row is underlined. The diameter of the alveoli is nearly constant along the tooth row and the interalveolus distances are equal or slightly longer than the alveolus diameter. The lateral margin of the maxilla is marked with shallow grooves visible in dorsal view for the occlusion of dentary teeth. FSAC Bouj-405 consists of a left portion of dentary, ( Fig. 7K ).Its lateral margin is marked by deep natural notches that indicate occlusal grooves for the maxillary teeth. The mandible was more than twice wider than high, and the symphysis was probably very long. Its morphology suggests than it is probably from the same species as the maxillary fragments. FSAC Bouj-407 is a fragment of the posterior portion of the left maxilla and with two complete teeth.

Teeth are preserved. They are moderately long, circular in cross section (posteriormost being slightly compressed lateromedially) and their surfaces are smooth and bear anterior and posterior carinae.

COMPARISON AND DISCUSSION

All recovered vertebrae are procoelous, suggesting eusuchian affinity. The material belongs to at least two species, and both are longirostrine forms. FSAC Bouj-355 has a different morphology from other mandibular and maxillary fragments ( Fig. 7I ). It has large alveoli and its symphysis is slightly wider than high. The second form, represented by maxillae and portions of left and right dentaries ( Fig. 7 K-P), has its symphysis much wider than high with smaller alveoli than the first species.Two groups of longirostrine eusuchians have been described from the late Eocene: the gavialoids and the tomistomines ( Brochu 2003). FSAC Bouj-355 is too fragmentary to be attributed with certainty to any group, but its symphysis slightly wider than high with a straight lateral margin, the short distance between the left and right alveoli and their offset margins clearly differ from what is found in gavialoids and tomistomines. Even if no amphycoelous vertebra has been found, it cannot be excluded that this mandible pertains to a dyrosaurid, a group of non-eusuchian crocodyliformes , in which previously cited characters are present ( Jouve et al. 2019). These neosuchians survived to the Lutetian in Africa and Burma ( Buffetaut 1978). Awaiting more diagnostic material, FSAC Bouj-355 is thus considered as Crocodyliformes indet. The second mandible has laterally opened alveoli and its alveolar margin is not leveled with the palate, characters that are found in gavialoids ( Hua & Jouve 2004; Jouve et al. 2006, 2014). Gavialoids are particularly scarce in the Eocene and Oligocene of the Peri-Tethys deposits, and only three gavialoids are known: “ Gavialis ” dixoni Owen, 1849, from the early-middle Eocene of England and now considered as a nomen dubium ( Brochu 2007), unidentified Bartonian gavialoid remains from Dur At-Talah (Southern Libya) ( Llinas Agrasar 2004), and Eogavialis africanum ( Andrews, 1901) from the Priabonian and Rupelian of Fayum Egypt, ( Müller 1927). The remains from Gueran strongly resemble Eogavialis africanum , but they are too poorly preserved for an in-depth comparison. Therefore, the Gueran gavialoid is here considered as Gavialoidea indet. ( Jouve et al. 2019).

Figures

FIG. 7. — Crocodyliformes remains from Gueran: A-J, Eusuchia indet.: A, FSAC BOUJ-410, last cervical (ninth) vertebra in left lateral view; B, FSAC BOUJ- 1b, anterior cervical vertebra in left lateral view; C, FSAC BOUJ-400, posterior dorsal vertebra in left lateral view; D, FSAC BOUJ-1a, first caudal vertebra in left lateral view; E, FSAC BOUJ-124, caudal vertebra in left lateral view; F, FSAC BOUJ-94, osteoderm in dorsal view; G, FSAC BOUJ-96, posterior portion of a dorsal osteoderm; H, FSAC BOUJ-96, lateral portion of a dorsal osteoderm in dorsal views; I, J, Crocodyliformes indet.: I, FSAC BOUJ-355, mid portion of a dentary in dorsal view; J, FSAC BOUJ-406, posterior fragment of a left mandibular ramus in dorsal view; K-P, Gavialoidea indet.: K, FSAC BOUJ-405, portion of a left dentary in dorsal view; L, FSAC BOUJ-402, mid portion of a right maxilla in ventral view; M, N, FSAC BOUJ-404, FSAC BOUJ-403 and FSAC BOUJ-401, anterior (M) and mid portion (N) of left maxilla in ventral views; O, P, FSAC BOUJ-407, posterior portion of a left maxilla in lateral (O) and ventral (P) views. Scale bar: 1 cm.