Andrew Vik
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Dear Andrew K.

Thank you for the interesting perspective on relict groups. Australia also has
a few other unique molluscan living fossils, such as Campanile symbolicum
(last surviving member of a once widespread family) and Salinator fragilis
(one of only two species of operculate pulmonate gastropods in the world).

I have noticed a small correlation between animal groups which survived the
Cretaceous-Tertiary cataclysm in eastern North America and eastern Asia. There
are only two species of Alligator in the world, one in China and one in the
southeast USA. And the horseshoe crab, Limulus, only exists in the waters of
S.E.Asia and the S.E.USA. Is there a true connection here, or just
coincidence?

Yours, Andrew V.

Andrew K. Rindsberg wrote:

> Here's a nifty website on the Cretaceous trigoniid bivalve, Pterotrigonia
> (Scabrotrigonia) thoracica, which is the State Fossil of Tennessee (USA):
>
> http://www.utm.edu/departments/artsci/ggp/geo/fossil.html
>
> The only living genus of trigoniids is Neotrigonia, found in the warm seas
> around Australia, and it is a very pretty shell. Lucky Australians!
> Australia was on the opposite side of the world when the asteroid hit
> Yucatan. North American molluscan faunas were hit hard. Oh, yeah, the
> dinosaurs went extinct then too.
>
> A list of other US State Fossils is also given.
>
> Andrew K. Rindsberg
> Geological Survey of Alabama