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Re: Insane Yixian theropod diversity
HP Marjanovic wrote:
You've conflated the two parts of the Yixian Fm, which have different ages.
And you've added the Jiufotang Fm, which is quite a bit younger (source of
*Microraptor* including *Cryptovolans* and many if not most of the birds).
I was actually wondering about that when I was writing. Makes sense.
And don't forget the fact that there are lots of mammals, lizards, other
reptiles, etc. in the assemblage. So far, the Yixian carnivorous theropods
are not of a size that prevents them from being feeders on non-dinosaurs
contrast to, for example, Allosaurus or Tyrannosaurus, which really didn't
have the option of too many non-dino meals as adults...).
True. I knew there were a lot of other small things but I guess that was a
little dino-centric. Not much a Microraptor is going to do to a 7-meter
Jinzhousaurus anyway, I guess. But what WAS eating a 7-meter Jinzhousaurus?
Well, take a look at the rest of the fauna from the Yixian: there was an
incredible abundance of birds and several pterosaurs, many of which would
have represented prey species to several of the Yixian theropods.
On another perspective, there were also several different distinct
layers opf the Yixian with distinct taxa, including the lowermost
Lujiatun, the younger Sihetun, and so forth, which affect the actual
concentration of species.
See above. :)
Think of it: there must have been countless birds living in other
Cretaceous environments, but relatively few have been found. It is
probable that small non-avian theropods were likewise much more common
elsewhere than the fossil record indicates.
It seems like there are already more theropods known than any other group
(what's a group? subjective, I know)... maybe that's just because all
dinosaurian carnivores are theropods (pretty much) whereas herbivores are
spread throughout the tree. Add in size classes, niche partitioning, et
cetera and it's starting to make sense.
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