[Rockhounds] Tyrannosaurus rex may have been misunderstood

[Kreigh Tomaszewski]

Few dinosaurs exude the same mystique as Tyrannosaurus rex
<https://www.cnn.com/2021/04/15/world/t-rex-billions-intl-scli-scn/index.html>,
but the tyrant lizard king that once roamed across North America might have
been misunderstood.
A new analysis of the bones and teeth of 37 T. rex specimens suggests that
the dinosaur might need to be regrouped into three separate species -- with
the fearsome predator that lived 90 million to 66 million years ago
potentially getting two sibling species: tyrant lizard queen and tyrant
lizard emperor.


The study, published in the journal Evolutionary Biology, said it had long
been recognized that the "stoutness" of adult Tyrannosaur skeletons varied
considerably. This had been explained by sex differences -- with female T.
rex perhaps more petite than their male counterparts. Alternatively, it
could be explained by developmental stages
<https://www.cnn.com/2020/11/24/world/dinosaur-growth-t-rex-study-scn/index.html>,
or simply individual variation in traits.


Other differences include its banana-size teeth -- some T. rex jaws have a
single D-shaped incisor that is substantially smaller than the next tooth,
while others have two of these smaller D-shaped teeth.


The researchers compared the length and circumference of the femur, or
thigh bone, of 24 T. rex specimens. They also measured the base of the
teeth or space in the jaw to understand if 12 of the dinosaurs had one or
two slender incisor teeth. The study team's conclusion was that T. rex was
not a single, unchanging dinosaur but may have had two equally terrifying
sibling species.
"All three species were 6-7 tonnes with similar skulls and bodies. It would
be like the difference between being attacked by a lion or tiger. Not
much," said study author Gregory Paul, the author of "The Princeton Field
Guide to Dinosaurs."


The differences were "subtle," similar to how "skeletons of lion (Panthera
leo) and tiger (Panthera tigris) are hard to tell apart even among
experts," he said.
https://www.cnn.com/2022/02/28/world/t-rex-three-different-dinosaurs-scn/index.html