Paleontologists from the University of Bath and elsewhere have described a new genus and species of kritosaurin hadrosaurid dinosaur from a partial skull found in the Late Cretaceous Cerro Del Pueblo Formation.
Life reconstruction of Coahuilasaurus lipani. Image credit: C. Díaz Frías.
The newly-described species, named Coahuilasaurus lipani, had an estimated length of 8 m (26.2 feet).
It dates to the end of the Campanian age of the Late Cretaceous epoch around 72.5 million years ago.
Coahuilasaurus lipani belongs to Kritosaurini, an exclusive clade of duck-billed dinosaurs (Hadrosauridae) containing Kritosaurus navajovius and its relatives.
“Kritosaurins are one of the more diverse lineages of hadrosaur in North America, being represented by a plethora of species from the latest Cretaceous of the Western Interior,” said Dr. Nicholas Longrich from the University of Bath and his colleagues.
“The striking variation in jaw morphology suggests specialization for distinct ecological niches and foods.”
“The variation in cranial crest morphology in Kritosaurini also suggests that sexual selection drove the evolution of kritosaurins, as in the crested lambeosaurines and ceratopsids.”
“Although the bony crests of kritosaurins are not as elaborate, kritosaurins may have had elaborate soft-tissue structures.”
“The function of the kritosaurin crest is unclear,” the paleontologists said.
“It was conspicuous and so presumably functioned for display; in modern birds, cranial ornaments are occasionally used in intraspecific combat as well, for example, in hornbills, and the relatively robust crest could conceivably have performed a similar function.”
“The elaborate nasal chamber could also have been involved in vocalization, as proposed for lambeosaurs.”
The partial skull of Coahuilasaurus lipani came from the Cerro del Pueblo Formation of Coahuila, Mexico.
“A diverse assemblage of dinosaurs occurs in the Cerro del Pueblo Formation, including theropods and ornithischians,” the researchers said.
“Theropods include tyrannosaurids, the deinocheirid Paraxenisaurus normalensis, ornithomimids, caenagnathids, dromaeosaurids, and troodontids.”
“Ornithischians include ankylosaurs, ceratopsids, thescelosaurids, and hadrosaurids.”
The team’s analysis shows that Coahuilasaurus lipani differs from kritosaurins found further north in Laramidia.
It may be related to a kritosaurin hadrosaurid species called Gryposaurus monumentensis, suggesting it is part of a distinct, southern kritosaurin lineage.
“Along with specimens from the Naashoibito Member of the Kirtland Formation in New Mexico, Coahuilasaurus lipani documents the persistence of kritosaurins in the south after local extinction in northern Laramidia, a pattern also seen in Parasaurolophini and Lambeosaurini,” the scientists said.
“Southern faunas not only have distinct species, but different patterns of diversity change, compared to northern Laramidian faunas.”
“Differences in species composition and community structure in different parts of Laramidia mean that further work on the dinosaurs of Mexico and the American Southwest is needed to understand the evolution of dinosaur diversity in western North America.”
“Southern dinosaur faunas may have been characterized by both higher origination rates and lower extinction rates than northern faunas.”
The study was published September 1, 2024 in the journal Diversity.
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Nicholas R. Longrich et al. 2024. Coahuilasaurus lipani, a New Kritosaurin Hadrosaurid from the Upper Campanian Cerro Del Pueblo Formation, Northern Mexico. Diversity 16 (9): 531; doi: 10.3390/d16090531
