From the collections room (Xiphodolamia)

While our shark tooth collection at VMNH is dominated by Carmel Church specimens, we do have some from other localities. I recently came across this tooth mixed in with invertebrate remains from the Pamunkey River in Hanover County, Virginia. 

It caught my eye because at first glance it seemed to be a deformed tooth from a mako shark (genus Isurus). Upon closer examination I realized it is an anterior tooth from a different genus, Xiphodolamia ensis. It seems that Xiphodolamia is fairly rare, but has been reported from North America (the genotype is from New Jersey), Europe, Africa, and Asia. It is known from the Chesapeake Bay region, but as far as I know it hasn’t been specifically reported from Virginia in published literature. It seems to be restricted to the Eocene, and this particular specimen is from the lower Eocene Nanjemoy Formation. As far as I know, this is the only specimen of Xiphodolamia in our collection (there may be others that have not yet been identified).

Taxonomically, Xiphodolamia is a bit of a mystery. At various times it has been referred either to the hexanchiforms (cow sharks) or to the lamnids (mackerel sharks); the latter interpretation seems to be more accepted currently. (Isurus, my initial misidentification, is a lamnid.)

Jim Bourdon has an excellent page about Xiphodolamia on elasmo.com that includes photos of several specimens (follow the “Faunas” link to the Nanjemoy Formation).

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