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New Ancient Animals Found – Tiny “T Rex” and a Saber-Toothed Vegetarian

Dawn RunnerPaleontologists have recently uncovered the fossils of two small creatures that defied some basic “dinosaur rules”, and which have provided unique insights into the evolution of both carnivorous and plant-eating creatures.  Eodromaeus, christened the Dawn Runner, resembled a pint-sized Tyrannosaurus, and likely gave rise to the most ferocious predator of ancient times, T rex.  Tiarajudens eccentricus, on the other hand, ate plants yet was equipped with long, pointed fang-like teeth – a “saber-toothed cow” of sorts.

The Dawn Runner, Eodromaeus,

This 4-foot-long, 10-15 pound fellow likely made up in ferocity what it lacked in size.  Pondering its image (please see photo of skeleton and artist’s recreation in article below), I can’t help but think that “prehistoric herpers” would have surely made a pet of this one!  Of course, dinosaurs and humans did not inhabit earth at the same time, but if we had…

The Dawn Runner’s skeleton was unearthed in an area known as the Valley of the Moon, at the foot of the Andes Mountains in Argentina (please see photo…this valley is aptly named!). Studies of it are expected to provide a rare glimpse into the earliest days of the meat eating dinosaurs.  As we now far more about the dinosaurs demise than their origins, paleontologists are pleased with this possibility.

Long of neck and tail, and able to run on its rear legs, the Dawn Runner may be the first in the line of creatures that culminated with the mighty T. rex.  Also found near the Dawn Runner were the remains of small plant-eaters, such as Eoraptor, upon which the sawed off “terrible lizard” likely fed.

A Saber-Toothed Vegetarian, Tiarajudens eccentricus

 Tiarajudens eccentricus skullTo the formidable predators that stalked Brazil 250 million years ago, Tiarajudens might at first have appeared to be an easy mark.  Only dog-sized, it was a small beast for the times, yet it was stocky and so would provide a decent meal.  However, the little creature was not defenseless…it sported two huge fang-like teeth that were totally out-of-character for a vegetarian.

Paleontologists theorize that Tiarajudens displayed these teeth, which resembled those sported by Saber-Toothed Tigers (please see photo and recreation in article below) to ward off potential predators before they attacked; perhaps they were functional in battle as well.  The sabers might also have found use in territorial disputes with others of its kind, and could possibly have helped Tiarajudens to pull branches within reach when feeding.  The rest of its teeth were similar to those evolved by other plant-eaters.

Tiarajudens’ line died out in time, but its fossils offer a unique look at the origins of canine teeth.  The group in which it is classified, the Theraspids, are believed to have featured in the evolution of today’s mammals.  Today, saber-bearing plant eaters are rare but not unknown; please see this photo of Musk Deer skulls for a modern-day example (I have worked with these creatures – the only time I used gloves when handling deer!).

Further Reading

Artist’s re-creation of the Dawn Runner and video explaining its discovery

Artist’s re-creation of the Saber-Toothed Vegetarian and further info



Dawn Runner rendition image referenced from wikipedia and originally posted by Conty
Tiarajudens eccentricus skull image referenced from wikipedia and originally posted by Juan.Cisneros




About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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