Eotyrannus

Name:

Eotyrannus (Greek for "dawn tyrant"); pronounced EE-oh-tih-RAN-us

Habitat:

Woodlands of Western Europe

Historical Period:

Early Cretaceous (125-120 million years ago)

Size and Weight:

About 15 feet long and 300-500 pounds

Diet:

Meat

Distinguishing Characteristics:

Small size; relatively long arms with grasping hands

The tiny tyrannosaur Eotyrannus lived during the early Cretaceous period, about 50 million years before more famous relatives like Tyrannosaurus Rex--and, following a common theme in evolution, this dinosaur was much smaller than its giant descendant (the same way the first, mouse-sized mammals of the Mesozoic Era were much smaller than the whales and elephants that evolved from them). In fact, the 300- to 500-pound Eotyrannus was so slender and wiry, with relatively long arms and legs and grasping hands, that to the untrained eye it might look more like a raptor; the giveaway is the lack of single, giant claws on each of its hind feet, as sported by the likes of Velociraptor and Deinonychus. (One paleontologist speculates that Eoraptor was actually a non-tyrannosaur theropod closely related to Megaraptor, but this idea is still being digested by the scientific community.)

One of the most remarkable things about Eotyrannus is that its remains were discovered on England's Isle of Wight--western Europe isn't exactly famous for its tyrannosaurs! From an evolutionary point of view, however, this makes sense: we know that the earliest tyrannosaurs (like the 25-pound, feathered Dilong) lived a few million years before Eotyrannus in eastern Asia, while the largest tyrannosaurs (like the multi-ton T. Rex and Albertosaurus) were indigenous to late Cretaceous North America. One possible scenario is that the very first tyrannosaurs migrated west from Asia, quickly evolving to Eotyrannus-like sizes, and then reached the culmination of their development in North America. (A similar pattern held with horned, frilled dinosaurs, the tiny progenitors of which originated in Asia and then made their way westwards to North America, spawning multi-ton genera like Triceratops.)