Thursday, January 14, 2010

Fossil of the Week

1/14/10 – Half shell on the Half Shell

Fossils are not always perfect, and here is a good example. This is a syntype* of a freshwater clam, named Anodonta cornelliana by Carlotta Maury in Bulletins of American Paleontology no. 15 in June 1902. It is Oligocene in age (approximately 30 million years old), from Chalk Hills, near Rosefield in northeastern Louisiana, and was named in honor of Cornell University.

The specimen: This specimen is the posterior half of one of the two valves of the clam – in other words, it’s only one quarter of the bivalve. It is furthermore a cast**; all of the original shell is long gone. The pointed end at the bottom is the real posterior end of the clam. The wide end at the top is the broken edge. Other specimens (in this case, other syntypes – Maury illustrated four in her paper) were needed for the author to describe the rest of the mollusk. This done, she estimated that the intact shell would have been 3 inches long by a little over 1 inch in height. It was originally thin shelled, with a sharp carina or ridge from the beak (umbo) to the posterior point. That ridge shows clearly on this specimen as the elevated ridge down the mid-line of the shell.

The scientist: Carlotta Joaquina Maury (1874-1938) specialized in Tertiary mollusks. She was born into a family with significant scientific interests and accomplishments (her older sister Antonia was a Harvard astronomer). Maury attended Cornell University, where despite academic programs designed to prepare women for occupations considered suitable for them, and the prejudice of male faculty, she obtained a PhD under Gilbert Harris (who would found PRI in 1932). When she was not promoted at Barnard College (a women’s liberal arts college in New York City), she accepted a position at a college in South Africa. Expeditions there, in New York, Louisiana, Trinidad, and one that she personally led to Santo Domingo gave her ample material for scientific publications. The paper in which this species was described – “A Comparison of the Oligocene of Western Europe and the Southern United States” – was the published version of Maury’s Ph.D. dissertation.

*See Fossil of the Week 11/11/09 - Bellerophon calcifer for a definition of "syntype."

**See Fossil of the Week 12/30/09 – Fossil Cast for a description of how casts are formed.

Text by Paula Mikkelsen

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