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Re: questions about the Odontochelys study
To continue my monologue:
I'll check out *Palaeochersis* and *Australochelys* tomorrow, but unless
filling in the thyroid fenestra was fashionable in the Triassic, it looks
like a safe bet that turtles ancestrally lack the thyroid fenestra.
*Australochelys* is only known from a skull. *Palaeochersis* lacks a
full-size thyroid fenestra according to the 2007 monograph on it; it may
just have an obturator foramen like *Proganochelys* or some kind of
So, it is one step more parsimonious to assume that turtles ancestrally lack
the thyroid fenestra, no matter what their sister-group is.
Incidentally, sauropterygians ancestrally have both an obturator foramen and
a thyroid fenestra: the obturator nerve does not have to pass through the
thyroid fenestra just because it's there.
However, *Placodus* hasn't got a thyroid fenestra either, just a little
- at least *Proganochelys* and *Odontochelys* lack even this notch, though.