RE: Differences between *Vancleavea* and thalattosaurs

[Jaime Headden <qi_leong@hotmail.com>]

David Marjanovic wrote:

<That's actually fairly common in taxa with subthecodont tooth implantation. 
It's not part of the definition, AFAIK.>

  I am not familiar with the precise definitions. I am not sure any have been 
codified. My understanding of subthecodonty is derived from taxa defined as 
being subthecodont. In this case, thecodonty is the presence of a socket where 
the underlying bone separating the erupted crown's root from unerupted germ 
teeth is missing (germinating and germinated teeth are in the same socket). 
Subthecodont animals possess a bony barrier between the germinating chamber and 
the tooth socket specifically. For the record, however, the lingual wall of the 
tooth socket in *Miodentosaurus* appears to be formed by the splenial (Wu et 
al., 2009), another feature that distinguishes it from *Vancleavea*.

Dave Peters wrote:

<Why is the orbit in the front half of the skull?>

  Unfortunately, you've run into one of those issues where a complex of 
features is assumed to be one feature, and the relative positions of various 
foramina and fenestrae in skulls is highly dependant on, of all things, the 
bones that define their margins. In this case, the preorbital skull is very 
short (as is the nasal and maxilla) while the postorbital skull is very long, 
exaggerated by the extreme length of the parietal, posterior rami of the jugal 
and postorbital, and the anterior ramus of the quadratojugal. These 
artificially (and interrelatedly) produce a foreshortened skull. The real trick 
here is scaling each region of the skull to a noncranial component that does 
not exhibit a lot of relative variation, and in this I would propose some axial 
lengths as the baseline as vertebrae MAY be more stable than cranial 
proportions. (Of course, I've not tested his hypothesis, so I have no idea HOW 
stable it may be.)

David Marjanovic wrote:

<The comments by referees _never_ spend a lot of space on listing the 
advantages of a manuscript. "It's good and interesting, let it through" is hard 
to say in 100 words. Listing problems and what to do about them, however, 
requires lots of space.>

  In the few manuscripts that I've shown to others, my reviewers (rather than 
referees) spend a lot of time picking the whole manuscript apart and hus the 
work has greatly benefitted another perspective. Referees talk to editors, 
who've also already received the reviews pre and post drafts, not to authors.

<Accusations of personal agendae are, consequently, rather laughable.>

  All due Latin aside, as the word "agenda" has entered the English language as 
a stable word and have even been modified wholly in English, the word now has 
an English plural.

Cheers,

Jaime A. Headden

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

"Human beings, who are almost unique in having the ability to learn from the 
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