Scientists discover 94-million-year-old mosasaur fossil in Utah

Once dominants of the sea in the dinosaur age, fossil specimen in the mosasaur taxon family similar to the modern Komodo Dragon.
Shubhangi Dua
Remains of a prehistoric mosasaur that dominated the ocean found in Utah
Remains of a prehistoric mosasaur that dominated the ocean found in Utah

MR1805 / iStock 

A seemingly extinct group of marine-adapted reptiles, mosasaurs were last known to have lived 82 to 66 million years ago during the last period of the Mesozoic era. 

Recently, scientists found traces of a mosasaur fossil dating back 94 million years. The research was organized by the Bureau of Land Management (BLM) and led by Dr Barry Albright, a faculty member at the University of North Florida (UNF).

UNF says that the team of researchers unlocked new evolutionary information following the discovery of the prehistoric mosasaur.

Additionally, the team exclusively spotted the remains of a single specimen of the mosasaur taxon called Sarabosaurus dahli.

Study shows that significant portions of the skull and axial postcranial skeleton were identified that matched the prehistoric specimen. 

Uncovering fossils 

These fossilized remains were unearthed in the lower Turonian area in the gray shale badlands of the National Park Service Glen Canyon National Recreation Area in southern Utah.

The notion to look for fossilized remains of marine creatures commenced when a volunteer under Dr Alright, Scott Richardson looked to uncover mosasaurs hailing from the seaway in the middle of North America during the Late Cretaceous Period ranging between 84 to 95 million years ago.

“In March 2012, Richardson found numerous small skull fragments and vertebrae of what proved to be an early mosasaur scattered across a broad shale slope,” UNF said.

The research continued for eleven years after the finding of the skull fragments of a mosasaur. 

Dr Albright said that when the Tropic Shale was being deposited nearly 94 million years ago, mosasaurs were still very small, primitive, and in the early evolutionary stages of becoming fully marine adapted. Due to this, their fossils have been extremely rare and difficult to find.

The joint team of paleontologists recovered close to 50 percent of the specimen. The team included a volunteer, Steve Dahl whose name was honored in the species name, Sarabosaurus dahli, known as “Dahl’s reptile of the mirage.”

The name reflects both the vanished ancient seaway where the animal harbored and also identifies with the mirages associated with the region’s intense summer heat.

Researcher Dr Michael J. Polcyn of the University of Utrecht, Netherlands, and Southern Methodist University, Dallas says that Sarabosaurus sheds light on long-standing questions regarding the relationship of some early-branching mosasaurid species. 

Scientific findings

“It also provides new insights into the evolution and antiquity of a novel cranial blood supply seen in a particular group of mosasaurs,” he added. 

Over time mosasaurs evolved into gigantic lizard-like marine predators from just being 3 feet long, study finds. These predators dominated the oceans during the latter part of the dinosaur age

Similar to their land-dwelling ancestors the modern Komodo Dragon, the marine animal developed streamlined bodies, paddle-like fins, and tails that equipped them to survive in water. 

The main difference between the early forms of mosasaurs to Sarabosaurus was the latter had a new type of blood circulation in its brain. While the older counterpart was more lizard-like in appearance and retained relatively primitive tails and limbs, UNF said.

 Dr Alan Titus, BLM Paria River District paleontologist says, “Mosasaurs from younger rocks are relatively abundant, but mosasaurs are extremely rare in rocks older than about 90 million years. Finding one that preserves so much informative data, especially one of this age, is truly a significant discovery.”

The study was published on 14 June in Cretaceous Research, read here.

Abstract

We describe and name a new mosasaur taxon, Sarabosaurus dahligen. et sp. nov., from the lower Turonian part of the Tropic Shale in Utah, USA. The holotype specimen preserves significant portions of the skull and axial postcranial skeleton. It was found in the upper part of the Watinoceras devonense Ammonite Zone, bounded by radioisotopic dates above and below, and is thus about 93.7 Ma, the oldest mosasaurid taxon known from the Western Interior Seaway. The new taxon possesses a vascular pattern of the basisphenoid heretofore only seen in late diverging plioplatecarpine mosasaurids. Reevaluation of the morphology of the basisphenoid of previously described Turonian mosasaurs using μCT techniques reveals the derived condition is also present in Yaguasaurus and the incipient condition in Tethysaurus and Russellosaurus. In these two taxa, the canals enter the basisphenoid, but do not pass into the basioccipital. Instead, they exit only high on the posterior wall of the sella turcica, in a position similar to the basilar artery of other lizards. This vascular pattern, both in its incipient and derived states, is unique among squamates and supports inclusion of the aforementioned taxa in a monophyletic Plioplatecarpinae, for which we provide an emended diagnosis. Phylogenetic analysis recovers Sarabosaurus dahli gen. et sp. nov. as the sister taxon to Yaguarasaurus and all other later diverging plioplatecarpines, with Russellosaurus and Tethysaurus as successive sister taxa. Tylosaurine mosasaurids retain the primitive condition of the basisphenoid vascularization pattern and implies a tylosaurine-plioplatecarpine divergence in the late Cenomanian or earliest Turonian.

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