Thank you, Michael. Yes, ligament is commonly preserved in articulated,
very fresh fossil bivalves from the Coastal Plains of the eastern and
southern U.S. Gwen Daley and Andrew Bush, grad students at Virginia Tech,
have been studying the preservation and breakdown (taphonomy) of bivalve
ligament in fossils, particularly in the Pliocene and Pleistocene of
Virginia (1998, Geological Society of America, Abstracts with Papers, v.
30, no. 4, p. 9). Daley and Bush found that microscopic aragonitic spicules
can be preserved along with the tough organic tissue. The earliest record
of fossil ligament of which I am aware is that of T. A. Conrad, who noted
ligament in middle Eocene bivalves from Claiborne, Alabama in 1834-35. I
have seen preserved ligament in shells from several Alabama formations,
including the lower Eocene Hatchetigbee Formation at Hatchetigbee Bluff.
Incidentally, the large Venericardia from that site are commonly partly
silicified within the shell. It's interesting that the calcium carbonate
can be replaced by silicon dioxide without destroying the organic ligament.
 
But as to DNA in fossil ligament, I do not know of any studies. Perhaps
another Conchler does. It would certainly be worth a try.
 
Andrew K. Rindsberg
Geological Survey of Alabama
Tuscaloosa, Alabama, USA