Torvosaurus tanneri (“Nathan E. Tanner’s savage lizard”) was one of the largest theropod dinosaurs in the Morrison Formation. It measured 35 feet long, the same size as Allosaurus. However, Torvosaurus came from a more primitive line of theropods, the megalosaurs. As such, it retained some more primitive features compared to more advanced theropods living at that time like Allosaurus, and was probably less intelligent than Allosaurus (although not by much, apparently, since Allosaurus wasn’t exactly the brightest bulb either, according to studies of Allosaurus’ brain).
Torvosaurus and Allosaurus may have lived in the same location at the same time, but Allosaurus was clearly the most numerous theropod in the Morrison Formation. Very few remains of its competitor have been found. The first fossils of this animal were discovered in Colorado in 1971, and the species was officially named and described in 1979. Another species, T. gurneyi, was found in Portugal’s Lourinhã Formation, also dated to the late Jurassic. Although known from incomplete remains, it’s evident that the European species has a more boxy rectangular skull than its North American counterpart.
Torvosaurus and Allosaurus had the same length, but they possessed different physical proportions. These anatomical differences no doubt drove these two species to develop different hunting styles. It seems that Torvosaurus was a Jurassic analog for a tyrannosaur, since it had an unusually large head and unusually small arms in proportion to its body. Its body was long and shallow, whereas the body of Allosaurus was short and deep – good for a large heart and lungs, indicating an active lifestyle. Torvosaurus’ neck was short and muscular, while Allosaurus’ neck was longer and more sinuous. Torvosaurus had short arms and small hands (but unusually large thumb claws), while Allosaurus had longer arms, huge hands, and absolutely huge claws – obviously used for grabbing and ripping things. Torvosaurus seems to be rather front heavy (good for physically slamming it’s jaws onto prey) while the weight on Allosaurus appears to be more evenly distributed. Allosaurus also had an unusually long tail in proportion with its body – a definite feature of an agile runner. Therefore, it seems that Torvosaurus was primarily a short-distance chase ambush hunter who relied upon its jaws to do most of the work. By contrast, Allosaurus was a very active energetic predator who was capable of impressive speed and quick turns.
This drawing took a long time, as you can assume from its high amount of detail. Every individual scale was drawn one by one. To give you a better appreciation of the time to draw this, in real life this drawing frome nose-tip to tail-tip is only 21 inches long – 1/20 scale, as most of my prehistoric drawings are. Medium was No. 2 pencil on copy paper, along with some touch-up on my computer to fix the places where the two pieces of paper were joined together.
Keep your pencils sharp, everybody.