Catching up with some of the latest developments in ornithischian dinosaur research. For example, late last year, a new saurolophine hadrosaurid dinosaur from New Mexico was formally described.  Named Ahshislesaurus wimani, it reinforces the view that hadrosaurs were among the dominant large herbivorous dinosaurs present in southern Laramidia during the last ten million years of the Cretaceous.

Ahshislesaurus wimani life reconstruction. Picture credit: Sergey Krasovskiy.

Picture credit: Sergey Krasovskiy

Ahshislesaurus wimani

The research team erected a new hadrosaur taxon based on the study of skull bones as well as postcranial material. The bones that would be identified as Ahshislesaurus were uncovered in San Juan County (northwestern New Mexico), by famed collector John B. Reeside, Jr. in 1916. In 1935, the fossils were classified as belonging to another hadrosaurid named Kritosaurus navajovius. However, this new research identified distinctions between these fossils and all known hadrosaurids, including several key differences in the animal’s skull.

Ahshislesaurus (pronounced Ah-shi-sle-sore-us), is estimated to have reached lengths in excess of eleven metres.  It might have weighed more than eight tonnes. The fossil material comes from the lower Hunter Wash Member of the lower Kirtland Formation (Campanian faunal stage). The paper describing the new species was published in the Bulletin of the New Mexico Museum of Natural History and Science.  It is a journal managed by the New Mexico Museum of Natural History and Science.

Co-author of the paper, Dr Anthony Fiorillo, Executive Director of the New Mexico Museum of Natural History and Science stated:

“Discoveries like this remind us that science truly is a community. Our team of researchers spanning five institutions and two countries were able to build upon research that started nearly a century ago and now advances our understanding of what our state looked like during the Late Cretaceous Period.”

Right jugal of the holotype of Ahshislesaurus wimani gen. et sp. nov., (USNM VP-8629); in A, lateral view; B, medial view. Picture credit: Dalman et al.

Picture credit: Dalman et al

Dr Fiorillo examined the fossils alongside his colleague Dr Spencer Lucas.  In addition, Sebastian Dalman (Montana State University), the lead author and co-authors Steven Jasinski (Harrisburg University), Edward Malinzak (Pennsylvania State University), and Martin Kundrát (Pavol Jozef Šafárik University in Slovakia) were involved in the research.

De Lucas commented:

“It seems like palaeontologists are discovering new dinosaurs in New Mexico every few months. This new hadrosaur just adds to my conviction that there are many, many new dinosaurs still out there waiting to be unearthed!”

To read an article from 2018 about the discovery of a new species of armoured dinosaur in New Mexico: A New Nodosaur from New Mexico.

A new species of chasmosaurine ceratopsian from New Mexico: The Chasmosaurine Bisticeratops.

A Novel Clade of Flat-headed Saurolophine Hadrosaurids

Although only some isolated skull material has been found, the scientists postulate that Ahshislesaurus lacked a head crest. The skull of Ahshislesaurus wimani preserves several taxonomically informative characters that show close affinities with the stratigraphically younger Naashoibitosaurus ostromi from the De-na-zin Member. Together with Naashoibitosaurus, Ahshislesaurus forms a potentially novel clade of flat-headed saurolophine hadrosaurids. This clade suggests the saurolophines were a taxonomically diverse group, which, during the last twenty million years of the Cretaceous, were among the dominant herbivorous dinosaurs in southern Laramidia.

Scientists are building up a detailed picture of the dinosaur fauna from the Late Cretaceous of New Mexico. Similar types of dinosaurs existed in southern Laramidia as those in more northerly parts of the landmass. However, the genera are different.  For example, the herbivorous Ahshislesaurus wimani co-existed with ankylosaurids and horned dinosaurs like Navajoceratops.  The apex predator was a tyrannosaur – Bistahieversor.

Proximal cervical vertebrae of the holotype of Ahshislesaurus wimani gen. et sp. nov., (USNM VP-8629); in right lateral view. Picture credit: Dalman et al.

Picture credit: Dalman et al

What’s in a Name?

This new hadrosaur taxon was named for the Ah-shi-sle-pah Wilderness in San Juan County, where its fossils were found. The specific epithet, “wimani”, honours the first Swedish professor of palaeontology, Carl Wiman (1867–1944), from Uppsala University, who worked on fossil vertebrates from the San Juan Basin. Recognition of a new hadrosaurid species from New Mexico also provides further evidence for latitudinal variation in the hadrosaurid fauna during the Late Cretaceous in Laramidia. In addition to the holotype of A. wimani, several specimens from the same strata may also belong to this newly identified species, including a well-preserved left dentary and a partial skeleton, as well as two humeri, one belonging to a large adult and the other to a juvenile.

The scientific paper: “A new saurolophine hadrosaurid (Ornithischia: Hadrosauridae) from the Upper Cretaceous (Campanian) Hunter Wash Member, Kirtland Formation, San Juan Basin, New Mexico” by Sebastian Dalman, Steven E. Jasinski, Dale Edward Malinzak, Spencer G. Lucas, Martin Kundrát and Anthony R. Fiorillo published in the New Mexico Museum of Natural History and Science Bulletin.

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