Fossil of mosasaur with bizarre “screwdriver teeth” found in Morocco

Newswise — Researchers have unearthed an unfamiliar mosasaur variant, an aquatic reptile hailing from the prehistoric era, showcasing distinct, grooved dentition unlike any familiar reptilian species. Coupled with contemporary discoveries in Africa, this implies a swift evolutionary progression within mosasaurs and other marine reptiles until approximately 66 million years ago. At that juncture, an asteroid impact eradicated these creatures, alongside dinosaurs and approximately 90% of Earth's species.

Stelladens mysteriosus, the novel species, originates from Morocco's Late Cretaceous epoch, boasting dimensions approximately twice that of a dolphin.

Its teeth exhibited an exceptional configuration characterized by blade-like ridges, forming a star-shaped arrangement that evoked the resemblance of a cross-head screwdriver.

While the majority of mosasaurs typically possessed dual bladelike, serrated ridges on the anterior and posterior sides of their teeth to facilitate prey cutting, Stelladens diverged by featuring an elevated count of these blades. Ranging between four and six, these distinctive ridges extended along the length of its teeth.

"It's a remarkable revelation," expressed Dr. Nick Longrich of the Milner Centre for Evolution at the University of Bath, the lead researcher of the study. "This discovery deviates from the characteristics observed in any known mosasaur, reptile, or even vertebrate species we have encountered thus far."

Dr. Nathalie Bardet, a renowned expert in marine reptiles from the Museum of Natural History in Paris, exclaimed, "Having devoted over two decades to studying the Moroccan mosasaurs, this is a completely unprecedented find. I was left astounded and bewildered by its distinctive features, an amalgamation of both perplexity and awe!"

The discovery of multiple teeth exhibiting the same peculiar shape implies that the distinct morphology was not a consequence of pathology or mutation.

The distinctive teeth of Stelladens imply the presence of a specialized feeding strategy or diet. However, the specific dietary preferences or consumption habits of Stelladens remain unclear at present.

Dr. Longrich conveyed, "The enigma lies in the fact that we are uncertain about the diet of this creature since we have not encountered any living or fossilized counterparts resembling its unique characteristics."

"It is conceivable that this species developed a distinctive feeding method, or perhaps it occupied an ecological niche that is absent in the present era," suggested Dr. Longrich. "The tooth structure resembles the pointed end of a Phillips-head screwdriver or even a hex wrench, adding to the intrigue surrounding its feeding behavior."

“So what’s it eating? Phillips head screws? IKEA furniture? Who knows.”

Despite their small size, the stout teeth exhibited signs of wear on their tips, suggesting that soft-bodied prey was unlikely to be their primary target. On the other hand, the teeth lacked the strength required to crush heavily armored creatures such as clams or sea urchins.

Dr. Longrich commented, "The indications might point towards a diet comprising small and lightly armored prey such as thin-shelled ammonites, crustaceans, or bony fish, but it's challenging to ascertain with certainty." He further added, "During the Cretaceous period, there were peculiar creatures like ammonites, belemnites, and baculites that have vanished from the present-day. It is plausible that this mosasaur fed on an extinct prey species and occupied a unique ecological niche that no longer exists, potentially explaining the absence of similar findings in subsequent times."

Dr. Longrich expressed, "Evolution can exhibit unpredictability. Occasionally, it takes a distinct path, leading to the emergence of unprecedented forms that remain exclusive to a particular time period. Subsequently, such evolutionary developments may never reoccur in the future."

While mosasaurs coexisted with dinosaurs, it is important to note that they themselves were not dinosaurs. Rather, they were colossal marine lizards, belonging to the same reptilian group as Komodo dragons, snakes, and iguanas, but with adaptations that suited their life in the sea.

Mosasaurs originated approximately 100 million years ago and experienced a period of diversification until approximately 66 million years ago. During this time, a colossal asteroid impact occurred in the Yucatan Peninsula of Mexico, resulting in widespread darkness and significant global consequences.

While there has been ongoing scientific discourse regarding the factors contributing to the extinction event at the end of the Cretaceous period, the discovery of Stelladens, along with recent findings from Morocco, supports the notion that mosasaurs were undergoing rapid evolutionary advancements until their ultimate demise. Rather than fading away, it appears that mosasaurs were thriving and at the peak of their development when they faced extinction.

The recent study highlights the ongoing discovery of new species from the Cretaceous period in Morocco, suggesting that despite years of research, there are still numerous unidentified species waiting to be found. This phenomenon can potentially be attributed to the rarity of many species during that era, making their fossils less commonly encountered and thus requiring extensive efforts to uncover them. The continuous exploration of the Moroccan Cretaceous deposits underscores the significance of persistence and the potential for further revelations in paleontological research.

The authors of the study predict that in a very diverse ecosystem, it may take decades to find all of the rare species.

Dr. Longrich remarked, "Our current findings represent only a fraction of the species preserved in these sedimentary layers. We are far from exhausting the discoveries within these beds. Remarkably, this year alone, we have already encountered three new species. The level of diversity present at the end of the Cretaceous period is truly astonishing."

Nour-Eddine Jalil, a professor at the Natural History Museum and researcher at Univers Cadi Ayyad in Morocco, expressed, "The fauna from this region continues to astound us with its astonishing array of discoveries. We have encountered mosasaurs with saw-like tooth arrangements, turtles with snorkel-shaped snouts, an abundance of vertebrates exhibiting diverse shapes and sizes, and now, the unprecedented find of a mosasaur possessing star-shaped teeth."

“We would say the works of an artist with an overflowing imagination.

“Morocco’s sites offer an unparalleled picture of the amazing biodiversity just before the great crisis of the end of the Cretaceous.”

The new paper is published in the journal Fossils (DOI: 10.3390/fossils1010002).

Dr Longrich has also written a blog on these findings: A strange new mosasaur with screwdriver teeth from the Maastrichtian of Morocco