A novel species of bipedal archosaur belonging to the shuvosaurid family has been documented by paleontologists in New Mexico, offering new insights into a lineage of creatures that inhabited North America over 200 million years prior, during the Triassic period.
Labrujasuchus expectatus navigated the world on two legs with tiny arms and a toothless mouth tipped in a beak. Image credit: Jorge Gonzalez / NHMLAC Dinosaur Institute.
Designated as Labrujasuchus expectatus, this represents the most recently identified member of the Shuvosauridae, an ancient group of crocodile relatives characterized by anatomical features that mirrored those of small-armed, bipedal theropod dinosaurs.
“Shuvosauridae constitutes a distinctive clade of Triassic poposauroid pseudosuchians originating from western North America and Argentina,” stated Dr. Alan Turner of Stony Brook University along with his research team.
“These pseudosuchian archosaurs, notable for their slender build, bipedal locomotion, and lack of teeth, exhibit a striking convergence with ornithomimid theropod dinosaurs from the Cretaceous period.”
“Presently, three shuvosaurid species are recognized: Shuvosaurus inexpectatus, unearthed from the Cooper Canyon Formation in Texas; Effigia okeeffeae, discovered in the Coelophysis Quarry of the uppermost Chinle Formation in northern New Mexico; and Sillosuchus longicervix, found within the lower Ischigualasto Formation of San Juan province, Argentina.”
The presence of Labrujasuchus expectatus helps to bridge a gap in the fossil record between Shuvosaurus inexpectatus and Effigia okeeffeae.
With an estimated age of approximately 212 million years, the fossilized remains were recovered from the Hayden Quarry in northern New Mexico, USA, situated within the Petrified Forest Member of the Chinle Formation.
The recovered assemblage comprised a partial skeleton found in association with other fossilized remnants.
According to the investigating paleontologists, Labrujasuchus expectatus exhibited only marginal anatomical deviations from its related species, underscoring a trend of pronounced skeletal consistency within the group.
“The minimal morphological distinctions between the definitive skeletal specimens of these species suggest that this sameness in form was preserved across Shuvosauridae for at least ten million years within western North America,” the researchers elucidated.
“Labrujasuchus expectatus aligns seamlessly with the concept of morphological conservatism and fits within the currently established stratigraphic range for North American shuvosaurids.”
This discovery further bolsters the prevailing hypothesis that shuvosaurids were predominantly indigenous to western North America, a characteristic that distinguishes them from numerous other peculiar reptile groups of the Triassic era.
“Our phylogenetic analysis places this new species within a clade shared with the other two North American shuvosaurids, supporting the existence of an endemic lineage of small, bipedal, edentulous forms in the American Southwest,” the research team concluded.
The team’s report was officially published on May 26 in the Journal of Vertebrate Paleontology.
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Alan H. Turner et al. A new shuvosaurid (Archosauria, Poposauroidea) from the Late Triassic (Norian) Hayden Quarry of New Mexico, U.S.A. Journal of Vertebrate Paleontology, published online May 26, 2026; doi: 10.1080/02724634.2026.2618182
