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| Asiatosuchus oenotriensis Narváez, de Celis, Escaso, de Jesús, Pérez-García & Ortega, 2024 |
Abstract
The eusuchian crocodyliforms recorded in the Eocene levels of the Spanish Duero Basin belong to three lineages: Planocraniidae, with the species Duerosuchus piscator; Alligatoroidea, represented by several specimens of the genus Diplocynodon; and Crocodyloidea, which includes several specimens traditionally attributed to Asiatosuchus. The genus Asiatosuchus, established in 1940 based on a middle Eocene species from Mongolia, has subsequently served as a wastebasket taxon for Paleogene remains belonging to several species, not only from Asia but also belonging to the European and North American records. Many of these species are known by highly fragmentary remains, sharing the presence of characters such as a flat and triangular skull, and long symphyses in the lower jaw, recognized as characteristic for the crocodyloids. In addition to isolated cranial remains, among the material traditionally attributed to Asiatosuchus at the Duero Basin stands out a nearly complete skull and a left mandible, from the middle Eocene area of Casaseca de Campeán (Zamora Province). The present study analyses in detail these specimens, previously reported during the 1980s, but analyzed in a very preliminary way. They are included for the first time in a phylogenetic analysis to establish the systematic position of this Spanish form. The results confirm that it corresponds to a new species of basal crocodyloid, defined here as Asiatosuchus oenotriensis sp. nov.
Keywords: Asiatosuchus oenotriensis sp. nov., Crocodylidae, Lutetian, Spanish record, Zamora Province
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| Asiatosuchus oenotriensis sp. nov. |
SYSTEMATIC PALEONTOLOGY
Crocodylomorpha Walker, 1970.
Crocodyliformes Hay, 1930.
Eusuchia Huxley, 1875.
Crocodylia Gmelin, 1789.
Crocodyloidea Fitzinger, 1826.
Asiatosuchus Mook, 1940.
Type species: A. grangeri Mook, 1940.
Distribution: Lutetian (middle Eocene) of Asia and Europe.
Asiatosuchus oenotriensis sp. nov.
Diagnosis. Basal crocodyloid characterized by the following exclusive combination of characters respect to other non Crocodylidae and non Mekosuchinae Crocodyloidea (sensu Rio & Mannion, 2021): nasals not contacting the external naris; palatine process extending significantly beyond the anterior margin of the suborbital fenestrae, reaching anteriorly the level of the eighth maxillary alveoli; ectopterygoid maxillary ramus forming more than two-thirds of the suborbital fenestra lateral margin; and presence of shallow depressions on the sutural intersection of the frontal with the postorbital and parietal.
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Etymology. oenotri- refers to Oenotria (from the Greek, “the Land of Wine”) in reference to Tierra del Vino, the name of the natural region where the type locality is located; and -ensis, from the Latin, “belonging to.”
Type locality and horizon. Lutetian (middle Eocene) of Casaseca de Campeán (Zamora Province, Duero Basin, Castile and Leon Autonomous Community, central Spain) (see Ortega et al., 2022; and references therein).
CONCLUSIONS:
A detailed study of the remains of a crocodyloid from the middle Eocene of Casaseca de Campeán (Province of Zamora, Spain) reveals a set of exclusive characters allowing the establishment of a new crocodyloid taxon, A. oenotriensis sp. nov. Regardless of the phylogenetic analysis carried out, A. oenotriensis sp. nov. is recovered as an early branching crocodyloid closely related to the German synchronous species A. germanicus. Asiatosuchus oenotriensis sp. nov. can be distinguished from the other “Asiatosuchus-like complex” taxa from the European Paleogene on the basis of a unique combination of characters such as the absence of contact between the nasals and the external naris, the presence of a palatine process that extends significantly beyond the anterior end of the suborbital fenestrae, an ectopterygoid maxillary ramus forming more than two-thirds of the lateral margin of the suborbital fenestra, and shallow depressions on the sutural intersection of the frontal with the postorbital and parietal.
In addition, A. oenotriensis sp. nov. shares several characters widely observed in specimens related to the “Asiatosuchus-like complex”, such as the length of the mandibular symphysis, a large medial jugal foramen, the position of the surangular-angular suture, and a short dorsal premaxillary process. Among the “Asiatosuchus-like complex,” A. oenotriensis sp. nov. shows features only shared with the species A. germanicus, such as the participation of the splenial in the mandibular symphysis, a splenial having an anterior perforation for the mandibular branch of cranial nerve V, the presence of 16 mandibular alveoli, a lingual dental occlusion, and a linear frontoparietal suture with a modest entry into the supratemporal fenestrae.
Finally, the recognition of this new middle Eocene basal crocodyloid species increases knowledge on the diversity and distribution of the “Asiatosuchus-like complex” taxa, and adds valuable information to the knowledge of the systematics of the relatively diverse crocodyliform fauna from the Spanish Duero Basin.
Iván Narváez, Ane de Celis, Fernando Escaso, Santiago Martín de Jesús, Adán Pérez-García and Francisco Ortega. 2024. A New Crocodyloidea from the middle Eocene of Zamora (Duero Basin, Spain). The Anatomical Record. DOI: 10.1002/ar.25422
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