Paleonet: Polished clam identification?

Paula M Mikkelsen pmm37 at
Sun Nov 14 01:15:19 GMT 2010

Dear Paleonetters -
I am seeking help in identifying a polished Jurassic bivalve that seems to
be for sale everywhere, but is never fully identified. I purchased several
specimens at the GSA exhibition in Denver last week. They were simply
labelled "Paleozoic, Madagascar." On the web, I find them attributed to
Sakaraha, Majunga Basin, and Morondava Basin, all in Madagascar; and
Mesozoic rather than Paleozoic. I have seen only two with taxonomic names -
* Mercenaria *sp. (which seems unlikely) and "*Trigonia *Mussel Family"
(which also seems unlikely given the sculpture that remains). All of them
seem to be ca. 3 inches long, orange to white, double valved, with solid
infill. There is a distinct lunule and escutcheon - looks veneroid. Can
anyone identify this apparently common but mysterious clam, or point me in
the right direction in the literature?

See images of the clam at (scroll down
to polished fossilized clam) and

Baffled at PRI

Paula M. Mikkelsen, Ph.D.
Associate Director for Science
and Director of Publications
Paleontological Research Institution
1259 Trumansburg Road
Ithaca, NY 14850
Tel. (607) 273-6623, ext. 20
Fax (607) 273-6620
email  pmm37 at

"No passion in the world is equal to the passion to alter someone else's
draft."  -H. G. Wells

See "Seashells of Southern Florida: Living Marine Mollusks of the Florida
Keys and Adjacent Regions:
and BivAToL - Assembling the Bivalve tree of Life <>.

On Exhibit at Museum of the Earth:
*Science on the Half Shell: How and Why We Study Evolution* September 24,
2010 - January 17, 2011 With support from the National Science Foundation
and Maxie's Supper Club.

Mon. - Sat. 10 am - 5pm and Sun. 11 am - 5 pm.
Closed Tuesday and Wednesday (Labor Day to Memorial Day).

PRI and its Museum of the Earth <> are part
of Ithaca's Discovery Trail <>.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the Paleonet mailing list