Fossil of mosasaur with bizarre 'screwdriver teeth' found in Morocco


Date:
May 18, 2023
Source:
University of Bath
Summary:
Scientists have discovered a new species of mosasaur, a sea-dwelling
lizard from the age of the dinosaurs, with strange, ridged teeth
unlike those of any known reptile. Along with other recent finds
from Africa, it suggests that mosasaurs and other marine reptiles
were evolving rapidly up until 66 million years ago, when they were
wiped out by an asteroid along with the dinosaurs and around 90%
of all species on Earth.


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FULL STORY ========================================================================== Scientists have discovered a new species of mosasaur, a sea-dwelling
lizard from the age of the dinosaurs, with strange, ridged teeth unlike
those of any known reptile. Along with other recent finds from Africa, it suggests that mosasaurs and other marine reptiles were evolving rapidly
up until 66 million years ago, when they were wiped out by an asteroid
along with the dinosaurs and around 90% of all species on Earth.

The new species, Stelladens mysteriosus, comes from the Late Cretaceous
of Morocco and was around twice the size of a dolphin.

It had a unique tooth arrangement with blade-like ridges running down
the teeth, arranged in a star-shaped pattern, reminiscent of a cross-head screwdriver.

Most mosasaurs had two bladelike, serrated ridges on the front and back
of the tooth to help cut prey, however Stelladens had anywhere from four
to six of these blades running down the tooth.

"It's a surprise," said Dr Nick Longrich from the Milner Centre for
Evolution at the University of Bath, who led the study. "It's not like
any mosasaur, or any reptile, even any vertebrate we've seen before."
Dr Nathalie Bardet, a marine reptile specialist from the Museum of
Natural History in Paris, said: "I've worked on the mosasaurs of Morocco
for more than 20 years, and I'd never seen anything like this before --
I was both perplexed and amazed!" That several teeth were found with
the same shape suggests their strange shape was not the result of a
pathology or a mutation.

The unique teeth suggest a specialised feeding strategy, or a specialised
diet, but it remains unclear just what Stelladens ate.

Dr Longrich said: "We have no idea what this animal was eating, because
we don't know of anything similar either alive today, or from the
fossil record.

"It's possible it found a unique way to feed, or maybe it was filling
an ecological niche that simply doesn't exist today. The teeth look like
the tip of a Phillips-head screwdriver, or maybe a hex wrench.

"So what's it eating? Phillips head screws? IKEA furniture? Who knows."
The teeth were small, but stout and with wear on the tips, which seemed
to rule out soft-bodied prey. The teeth weren't strong enough to crush
heavily armoured animals like clams or sea urchins, however.

"That might seem to suggest it's eating something small, and lightly
armoured - - thin-shelled ammonites, crustaceans, or bony fish -- but
it's hard to know," said Longrich. "There were weird animals living
in the Cretaceous- ammonites, belemnites, baculites -- that no longer
exist. It's possible this mosasaur ate something, and occupied a niche,
that simply doesn't exist anymore, and that might explain why nothing
like this is ever seen again.

"Evolution isn't always predictable. Sometimes it goes off in a unique direction, and something evolves that's never been seen before, and
then it never evolves again." The mosasaurs lived alongside dinosaurs
but weren't dinosaurs. Instead, they were giant lizards, relatives of
Komodo dragons, snakes, and iguanas, adapted for a life at sea.

Mosasaurs evolved around 100 million years ago, and diversified up to
66 million years ago, when a giant asteroid hit the Yucatan Peninsula
in Mexico, plunging the world into darkness.

Although scientists have debated the role of environmental changes
towards the end of the Cretaceous in the extinction, Stelladens, along
with recent discoveries from of Morocco, suggests that mosasaurs were
evolving rapidly up to the very end -- they went out at their peak,
rather than fading away.

The new study shows that even after years of work in the Cretaceous of
Morocco, new species are continuing to be discovered. The reason may be
that most species are rare.

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

"We're not even close to finding everything in these beds," said Longrich, "This is the third new species to appear, just this year. The amount of diversity at the end of the Cretaceous is just staggering." Nour-Eddine
Jalil, a professor at the Natural History Museum and a researcher at
Univers Cadi Ayyad in Morocco, said: "The fauna has produced an incredible number of surprises -- mosasaurs with teeth arranged like a saw, a
turtle with a snout in the form of snorkel, a multitude of vertebrates
of various shapes and sizes, and now a mosasaur with 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."
* RELATED_TOPICS
o Plants_&_Animals
# New_Species # Nature # Frogs_and_Reptiles
o Earth_&_Climate
# Ecology # Environmental_Awareness # Exotic_Species
o Fossils_&_Ruins
# Dinosaurs # Evolution # Fossils
* RELATED_TERMS
o Ichthyosaur o Dinosaur o Feathered_dinosaurs o
Recent_single-origin_hypothesis o Homo_(genus) o Jurassic o
Homo_heidelbergensis o Timeline_of_evolution

========================================================================== Story Source: Materials provided by University_of_Bath. Note: Content
may be edited for style and length.


========================================================================== Related Multimedia:
* The_teeth_with_strange_ridges ========================================================================== Journal Reference:
1. Nicholas R. Longrich, Nour-Eddine Jalil, Xabier Pereda-Suberbiola,
Nathalie Bardet. Stelladens mysteriosus: A Strange New
Mosasaurid (Squamata) from the Maastrichtian (Late Cretaceous)
of Morocco. Fossils, 2023; 1 (1): 2 DOI: 10.3390/fossils1010002 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/05/230518120907.htm

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