How is the Allosaurus related to the Tyrannosaurus Rex?

Answer 1

Allosaurus was only 28 feet long and weighed somewhere between 2,200 and 8,800 lb, depending on the weight estimate you use, while Tyrannosaurus was 40 feet long and weighed between 12,000 and 26,000 lb. Besides the massive size difference, Allosaurus had a smaller head in proportion to its body but much larger arms with three clawed fingers, and its arms could be used for hunting. Tyrannosaurus had tiny, functionless arms, but it had the most powerful bite force known. Allosaurus had a bite force weaker than that of a lion. Allosaurus also had a small semicircular crest above each eye, which Tyrannosaurus didn't have.

Answer 2

By external (superficial) appearances only. There are quite a few, albeit subtle, differences in the skull, back (vertebrae) and ankles that more plainly show Tyrannosaurus is more closely related to modern birds than to Allosaurus.

It is true they were both theropods - had three toes on each foot, a tail and ate meat - but that's really about where the true similarities end. While both appear to be very similar in build and shape, the fact is that the Allosaurus had three fingers on a slightly larger hand, compared to the T. Rex's two fingers on a much more diminutive hand. The Allosaurus was also an ''early bloomer'' on the dino-scene, appearing at approximately 80 million years before the T. Rex, who showed up in the late Cretaceous period.

Relatively, the Allosaurus was quite primitive. He was also much smaller than the T. Rex, sporting a smaller 28' body vs. the T. Rex's 40' body length (approximately). Keep in mind, on the subject of length, almost since day one, the bones, specifically the vertebrae, have been placed together, end-to-end, on the the dinosaur exhibits in museums and the like. It's actually far more likely that dinosaurs had quite a bit of supporting tissue between the bones, which would make their length(s) far, far more impressive than has previously been thought as this would add several feet to even the more modestly sized animals. Consider, for example, if a 40' T. Rex has some 72 vertebrae in his back and spine, and the supporting tissue between the vertebrae was only 1'' think, which is very thin, considering their massive size and weight, that's another 6' to add to the T. Rex's already impressive length. Also, keep in mind, T. Rex may have dwarfed Allosaurus, but Giganotosaurus was about 6 or so feet longer than T. Rex. And Spinosaurus was quite a bit longer than them all, weighing in at about 49'.