Last week I gave you this gnarly looking skull from the Dead Zoo to identify:
I didn’t think it would be a difficult one, especially since it is a critter I’ve used as a mystery object before (although that was over 10 years ago!)
As I suspected, everyone figured out that this is the skull of an Alligator Snapping Turtle, but things have become a bit more complicated than they used to be over the last decade, since the single species that used to be in the genus Macrochelys has since been split.
The amount of splitting has varied, but at the moment it seems to have settled on two species being recognised; Macrochelys temminckii (Troost, 1835) and Macrochelys suwanniensis Thomas et al., 2014.
One of the key diagnostic features identified to differentiate between them is the angle of the squamosal (the bit of bone with the arrow pointing it above). In M. temminckii the angle is greater than 90° whereas in M. suwanniensis it’s less than 90°.
That suggests to me that the Dead Zoo specimen is probably the Suwannee Snapping Turtle Macrochelys suwanniensis Thomas et al., 2014. The only problem with this identification is that the collection locality is simply “Mississippi”, which doesn’t fit with the Suwannee river distribution of the species.
I’ll need to go back and look at a few other skeletal characters to confirm the identification once I’m back in the Dead Zoo, but my guess is simply that the collection locality wasn’t accurately recorded, since the specimen came from the natural history supplier Edward Gerrard rather being collected and properly documented by a researcher.
It certainly wouldn’t be the first time a representative locality has been given for a specimen meant for display or teaching rather than research!