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RE: JFC-ceratosaurus battling allosaurus, tooth-slpping?

The roots of theropod dinosaur teeth are pretty long, sometimes much longer, 
than the exposed crown of the tooth, and mostly this root lies inside the 
socket of the jawbone. Above the root, though not conclusively defined as such, 
the crown is limited to the extent enamel extends down the tooth: the gum of 
the jaw -- the oral epithelium -- should extend up to and beyond the position 
of the enamel. In many *Ceratosaurus* jaws, including the little baby at the 
Carnegie, the enamel of the tooth is half the exposed tooth's height in most of 
the maxillary teeth, suggesting that the tooth is mostly out of its socket. 
This is being argued without reference to X-ray or CT of the jaw in question. 

Now, theropods have continuously deciduous dentition, in which teeth are 
constantly replaced. New replacement teeth are formed to the inside and beneath 
the old teeth, and as they grow they "push" the previous tooth out. This 
happens in phases, with every second, third, or fourth tooth being pushed out 
in order, so that a functional dentition is always present. The timing of this, 
and the pattern, is called Zahnreihen. If you see this term show up in papers, 
it is because they are assessing the timing of appearance of specific teeth (in 
mammals) and in the phases of reptile tooth replacement in alternating 

But a lot of theropods, and even some pterosaur, fossils show evidence of 
extensive protrusion of their teeth. We would think that this is a problem, 
because if most of the teeth on a side were replaced at once, depending on the 
speed of eruption of the next set, this would leave the animals without a 
functional set of teeth for a few days. This would mean for a homeothermic, 
tachymetabolic animal -- like, as is suggested, *Ceratosaurus* -- that the 
animal would be deprived of means of processing food for several days, and that 
is unlikely. 

So the argument I would make (note that this is unpublished, so take with a 
grain of salt) is that the "extra long teeth" in some fossils are evidence of 
tooth slipping, that
ntal bonds that hold them in place within their sockets. Further support for 
this would be the relative absence of adequately-erupted replacement teeth 
beneath them. Whether tooth slipping actually occurs in fossils is a taphonomic 
one, and so far only adequately testable in thecodont (socket-toothed) 

This is, as I hinted at the two links below this paragraph, what probably 
happened in *Dilophosaurus wetherilli*, *Daemonosaurus chauliodus*, and 
*Ceratosaurus* sp.


It may have also happened in *Epidexipteryx hui*:


And I further discussed this issue in specific here:



  Jaime A. Headden
  The Bite Stuff (site v2)

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 

> Date: Tue, 7 Jan 2014 05:37:50 -0800
> From: hammeris1@att.net
> To: dinosaur@usc.edu
> Subject: Re: JFC-ceratosaurus battling allosaurus, tooth-slpping?
> Doing a look at google-images on "ceratosaurus skulls" there is a wide 
> variation in the dentures .... of course, some of those are 
> reconstructions-artist renditions, but a few look like some had the long 
> fangs and others more uniform.  If these are not species-differences, by 
> "tooth slippage" do you mean something that has occurred over time to the 
> fossils?