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A new non-mammaliaform eucynodont from the Carnian-Norian Ischigualasto Formation, Northwestern Argentina

2013; Volume: 16; Issue: 1 Linguagem: Inglês

10.4072/rbp.2013.1.05

2236-1715

Ricardo N. Martínez, Eliana Fernández, Oscar A. Alcober,

Paleontology and Stratigraphy of Fossils

The record of non-mammaliaformes eucynodonts from the Carnian-Norian Ischigualasto Formation is diverse and abundant, including a medium to large size herbivore and small carnivores.Here is described a new small eucynodont from the Ischigualasto Formation, on the basis of a partial skull.The new taxon is characterized by palatal process of the premaxilla extending posterior to the level of the fi rst postcanine; deep and large maxillary laterodorsal fossa that opens at the level of the root of the upper canine; and postorbital bar diverging posterolaterally at very low angle (35.6°) from the anteroposterior axis of the skull.Results from a phylogenetic analysis supports the new genus placement as a probainognathian eucynodont, more derived than Probainognathus Romer, and more closely related to Ecteninion Martinez, May & Forster and Trucidocynodon Oliveira, Soares & Schultz than to any other eucynodont.Ecteniniidae is proposed as a new clade including the new genus, Ecteninion and Trucidocynodon, and in the phylogenetic hypothesis represents the sister-group of Prozostrodontia (Prozostrodon Bonaparte & Barberena, Tritylodontidae and Mammaliaformes).Additionally, the new taxon from the Ischigualasto Formation shows that the Scaphonyx-Exaeretodon-Herrerasaurus biozone has similar cynodont diversity than the supposedly contemporaneous Hyperodapedon Assemblage Zone of Santa Maria 2 Sequence, in Southern Brazil.