An artist's reconstruction of Tylosaurus rex swimming in the Cretaceous seas of North America. Image courtesy of Alderon Games/Path of Titans.
Joel Kontinen
There's a
new T. rex in town. However, this one didn't hunt on land. It ruled the
ancient seas.
Scientists
have described a new species of mosasaur, a member of a marine reptile group
that lived at the same time as dinosaurs during the Cretaceous period (145 million to 66 million years ago). The newly named species fits into an already known
genus: Tylosaurus. But its new species name, Tylosaurus
rex — T. rex, for short — sets it apart from the other mosasaur
species in the group.
The species
name means "king of the tylosaurs," according to a new study
published May 21 in the journal Bulletin of the American Museum of Natural
History. According
to evolution, the fossils are about 80 million years old and were discovered
mostly in northern Texas decades ago.
The
mosasaur T. rex measured up to 13 meters) long, or about the length of a tour bus. It had finely serrated teeth,
unusually powerful jaws, and evidence on its fossils of violent combat with its
own species.
While
examining a fossil in the American Museum of Natural History's collection,
Zietlow noticed that a specimen labeled as Tylosaurus
proriger — a
well-known mosasaur species first described in 1869 — didn't quite match others
of its kind. The unusual fossil was discovered in 1979 near an artificial
reservoir outside Dallas.
After
comparing the specimen with the original name-bearing fossil of T.
proriger held at Harvard's Museum of Comparative Zoology, Zietlow and her
colleagues found that it belonged to a newfound species
Compared
with T. proriger, the newly described T. rex was 4 metres longer, had finely serrated teeth
(which T. proriger lacked) and lived several million years later.
Most T. proriger fossils were discovered in what is now Kansas and
are roughly 84 million years old, while the fossils now identified as T.
rex are mostly from Texas and date to about 80 million years ago. At that
time, the Western Interior Seaway stretched from the Gulf of Mexico up to the
Arctic and was home to many sea creatures, including mosasaurs.
But the dates
in the millions of years are inflated.
Source:
Kenna Hughes-Castleberry 2026
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