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Re: Sauropod Biology





From: Tim Williams <twilliams_alpha@hotmail.com>
Reply-To: twilliams_alpha@hotmail.com
To: dinosaur@usc.edu
Subject: Re: Sauropod Biology
Date: Sat, 28 Jan 2006 15:13:40 -0600


Sim Koning wrote:

There were probably specialist sauropods such as Brachiosaurus and
Dicraeosaurus. With its high shoulders, Brachiosaurus was likely a high browser like giraffes and Indricotherium,
[snip]
As with all specialists, these forms were prone to extinction, which is probably why the Brachiosaurs died out not long after the Jurassic.


David's already mentioned _Sauroposeidon_ (Aptian), and there was also slightly earlier post-Jurassic forms like _Pelorosaurus_. Also, although the Brachiosauridae (sensu stricto) appears to have died out by the end of the Early Cretaceous, the titanosauriforms as a whole thrived in the Late Cretaceous. The 'brachiosaurs' of traditional usage comprise forms that we know recognize as basal titanosauriforms, including (but not limited to) true brachiosaurids (e.g., _Brachiosaurus_, _Sauroposeidon_, probably _Pelorosaurus_, _Atlasaurus_).

My point was simply that the extremely derived, high shouldered forms seemed to have gone into decline after the Jurassic. There is some evidence that they may have survived into the late cretaceous though.


Complicating things further is the fact that some titanosaurs ate grass (based on coprolite contents), which suggests they were low grazers - at least some of the time.

I never said that sauropods were not low grazers. The point of my post was to show that the group as a whole was not limited to low grazing or high grazing, but were instead capable of both, with some forms being more specialized for one or the other.


Well... *Sauroposeidon*, which was bigger rather than smaller than *Brachiosaurus*, is... how old? Aptian? That would be, like, 120 Ma... that's 25 Ma after the end of the Jurassic... Dicraeosaurids (*Amargasaurus*) and rebbachisaurids survived for a similar length of time.

Rebbachisaurids persisted into the Late Cretaceous. If the teeth named _"Titanosaurus" rahiolensis_ belong to a rebbachisaurid, then the group survived until close to the end of the Cretaceous period. (This is a big "if" though.)


Cheers

Tim