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Re: new dinosaurs and 16 Foot Man Eating Croc Caught In Uganda



Tim Donovan wrote:

Doesn't appear likely. See JVP September 1997 page 571. "The femur of D. aquiluguis resembles that of B. bredai much more closely that that of the abelisaurid T. salluvicus..."

I doubt that this is the final word on the issue. We need more _Betasuchus_ material in order to determine if this guy is a tyrannosauroid or not.


That would've been likely only if the Dryptosaurus environment were isolated, which doesn't appear to have been the case. I'd expect the more advanced types to supplant the basal ones, just like in the west.

Why?

To be honest, I'm not sold on the idea that "primitive" (= more basal) taxa are obliged to go extinct whenever a more "advanced" (= more derived) relative arrives on the scene. I can think of examples where this did not happen. The basal bird _Rahonavis_ comes from around the end of the Cretaceous, and so this _Archaeopteryx_-like bird was contemporary with much more derived avians. _Leptoceratops_ and _Triceratops_ lived in the same time and place, even though _Leptoceratops_ is a basal neoceratopsian, and _Triceratops_ is one of the most derived neoceratopsians. Going back to the Late Jurassic, _Allosaurus_ and _Ceratosaurus_ rubbed shoulders in Utah; ceratosaurids are more basal than allosaurids.

Dryptosaurus was large enough to have competed for the same niche.

This reminds me of the Wild West: "This town ain't big enough for the two of us." Nevertheless, we know that several medium- and large-sized theropods existed in the Morrison fauna of western North America, including ceratosaurids, basal tetanurans ("megalosaurs"), and allosaurids. Many of these were contemporary. Apparently, the Morrison habitat was big enough for them all.




Tim