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Re: Dinosaurs burrowed to keep warm



Well, I was going to publish this in something like the "journal of irreproducable results" (assuming I have the time) but I will bring it up anyway. Sauropod juveniles could have acted like earthworms. The tail would act as a guide allowing them to feel the burrow and clean it and the neck would allow them to attack surrounding vegetation. It makes for hilarious diagrams.

While the above is not possible... it is interesting to consider that elephants have been found salt mining. The reason for Sauropod forclaws could be right under our feet.

- Jonas Weselake-George


----- Original Message ----- From: "Tim Williams" <twilliams_alpha@hotmail.com>
To: <dinosaur@usc.edu>
Sent: Friday, March 23, 2007 11:05 PM
Subject: Re: Dinosaurs burrowed to keep warm



Denver Fowler wrote:

>How many potentially burrowing ornithischians were present in the late
>Maastrichtian?

In north america: one.

(Warning: Unadulterated speculation coming up.)

I don't know which one Denver had in mind, but it depends upon how prevalent this behavior was among ornithischians. _Thescelosaurus_ and _Bugenasaura_ were both late Maastrichtian "hypsilophodont"-grade ornithopods. Although these two are outside the _Orodromeus_-_Oryctodromeus_-_Zephyrosaurus_ clade (in Varricchio et al.'s analysis, anyway), burrowing behavior may have first evolved much earlier in Ornithischia, as Dann suggested.

A _Zephyrosaurus_-_Orodromeus_ clade has been found before (e.g., Weishampel and Heinrich, 1992), and was diagnosed by the presence of a jugal boss (unknown in adult _Oryctodromeus_). It is possible that the jugal boss is related to burrowing too (to help push dirt aside?). A jugal boss is also seen in heterodontosaurs and many marginocephalians. Weishampel and Heinrich (1992) proposed that the jugal boss is primitive for the Ornithopoda+Marginocephalia clade (Cerapoda), but was secondarily lost in most ornithopods (including the stiff-tailed iguanodonts). I'm not putting too much stock in this single character, or its association with burrowing; it's all just dodgy speculation on my part.

The thing is, burrowing behavior in _Oryctodromeus_ would probably not have been inferred from anatomical evidence alone. The anatomy of _Oryctodromeus_ was interpreted in light of the taphonomic evidence. The anatomy of the closely related taxa (_Zephyrosaurus_, _Orodromeus_) was then re-interpreted. If other ornithischian taxa turn up in burrows, then other characters might be re-interpreted as burrowing characters too.

Cheers

Tim

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