Mean atmospheric O2
Geologic Time Scale
Allosaurus meets Stegosaurus
A dinosaur theropod of the genus Allosaurus stumbles upon a grazing armored stegosaurid dinosaur of the genus Stegosaurus in a Jurassic redwood forest 150 million years ago in what is today North America.
While it's probable that the 30 foot, 2 ton Allosaurus preyed upon large herbivores, it is doubtful that one would have risked a direct confrontation with an adult Stegosaurus, which could weigh as much as 5 tons and wields a powerful tail tipped with 3-foot spikes. Adding to its survivability, Stegosaurus' front legs may have been strong enough to allow it to pivot and swing its entire backside around to ward off an assault.
In addition to redwoods and varieties of fern, this Jurassic-period forest includes the now extinct seed fern from the genus Pachypteris, an arboreal plant that grew to a height of 10 feet and populated every major continent 160 million years ago (in this image the Stegosaurus is stepping back onto a Pachypteris, obliging a much smaller lizard to abandon its roost).
About that Allosaurus--were they really striped like Siberian tigers? Fossilized impressions of dinosaur skins reveal combinations of smooth and bony scales--and even feathers for some--but nothing has been preserved that would tell us what colors may have adorned them. Nevertheless, there are plenty of colorful modern reptiles for us to refer to, and birds, which may be the dinosaurs' closest living descendents, are among the most colorful vertebrates of all. Allosaurus reigned for 10 million years, so there was plenty of opportunity for them to evolve a wide variety of coloring schemes, if required.
Copyright © Walter B. Myers. All rights reserved.
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