The identification of a novel genus and species of predatory herrerasaurian dinosaur has been proclaimed, based on an incomplete yet remarkably preserved cranial specimen unearthed in the northern reaches of New Mexico, United States.
An artistic rendition of Ptychotherates bucculentus. Image credit: Megan Sodano / Virginia Tech.
This newly identified dinosaur inhabited Earth approximately 201 million years ago, during the Rhaetian epoch, marking the very end of the Triassic period.
Designated Ptychotherates bucculentus, this discovery provides an infrequent glimpse into a period of dinosaur history that remains poorly elucidated.
“The genesis of dinosaurs occurred during the Carnian stage (spanning from 237 to 227 million years ago), the earliest phase of the Late Triassic epoch, following which they diversified into three lineages that endured into the Jurassic: Ornithischia, Theropoda, and Sauropodomorpha,” stated Virginia Tech paleontologists Simba Srivastava and Sterling Nesbitt.
“The vast majority of the most ancient dinosaur fossil evidence originates from the high-latitude southern expanse of Pangea (encompassing present-day Brazil, Argentina, Zimbabwe, and India). Conversely, lower-latitude regions (specifically, Late Triassic deposits in the American Southwest and Morocco) yield scarce, if any, definitively identifiable dinosaur remains from comparable geological ages.”
The fossilized remnants of Ptychotherates bucculentus, which include an almost complete skull with an intact braincase and a substantial portion of the cranial roof, were exhumed in 1982 from the Coelophysis Quarry situated in northern New Mexico.
The skull itself measures approximately 22 cm (9 inches) in length, suggesting a dinosaur characterized by a notably elongated and narrow cranial structure.
“The cranial morphology reveals that the species possessed pronounced cheekbones, a broad braincase, and likely a short, deep muzzle,” observed the paleontologists.
“These features represented a novel combination for early dinosaurs, indicating a continuous process of evolutionary adaptation.”
Ptychotherates bucculentus is classified within one of the most ancient lineages of predatory dinosaurs, known as Herrerasauria.
This species exhibits a close phylogenetic relationship with two other Triassic dinosaurs: Tawa hallae and Chindesaurus bryansmalli.
These organisms collectively constitute a recently defined clade, Morphoraptora, which displays a mosaic of anatomical traits characteristic of both more basal dinosaurs and later theropods.
“Through comparative anatomical analysis with other Triassic archosaurs and its incorporation into phylogenetic investigations, we affirm Ptychotherates bucculentus as a new taxon of saurischian dinosaur closely allied with Tawa hallae,” the researchers reported.
“More broadly, our findings position Ptychotherates bucculentus as a member of Morphoraptora, a clade exclusively known from Upper Triassic strata in the southwestern United States.”
Prior to this discovery, scientific consensus suggested that by the concluding stages of the Triassic period, the earliest predatory dinosaur lineages had largely vanished, supplanted by more advanced theropods.
However, the existence of Ptychotherates bucculentus now suggests that certain of these groups persisted for a significantly longer duration than previously hypothesized, at least within the equatorial regions of the ancient supercontinent Pangea.
“Ptychotherates bucculentus was discovered in geological formations that may predate the major extinction event at the close of the Triassic period. The absence of any other known members of their family thereafter could indicate that this dinosaur group succumbed to that mass extinction event,” stated the scientists.
“This necessitates a reassessment of the impact of the end-Triassic extinction, recognizing it not only as a factor that eliminated competitors to dinosaurs but also as a cause of the demise of certain long-established dinosaur lineages themselves,” added Srivastava.
“Furthermore, given that no herrerasaurians have been identified from such a late Triassic period anywhere else, the region currently known as the American Southwest may have served as their last refuge and final stronghold.”
The scientific reporting of the Ptychotherates bucculentus discovery is detailed in a paper published this week in the journal Papers in Palaeontology.
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Simba Srivastava & Sterling J. Nesbitt. 2026. A new taxon of saurischian dinosaur from the Coelophysis Quarry of New Mexico, USA (Triassic: latest Norian or Rhaetian) highlights herrerasaurian diversity in the latest Triassic. Papers in Palaeontology 12 (2): e70069; doi: 10.1002/spp2.70069
