Friday mystery object #432 answer

Last week I gave you a mystery object from the Grant Museum of Zoology, UCL, with this old photo from my time as the Curator there:

This is one of those species that I have a bit of a soft spot for, due to the general weirdness of the skull. That does however make it quite recognisable as a specimen, even in a photo that hasn’t been taken for the purposes of identification – like this one.

Everyone who commented recognised that this is some sort of turtle, and thanks to that very flat skull with all the features towards the very front end, most people worked out that it’s a from a Mata-mata Chelus sp. Duméril, 1806.

Illustration of Chelus fimbriatus, by R. Mintern, 1885

Back in 2016, when I took the photo of the specimen, that would have been enough for a species identification (which would have been Chelus fimbriata), but today it’s simply not good enough, since molecular taxonomists determined a species level split in populations from the Amazon and Orinoco basins in 2020. Darn.

Fortunately, morphological differences between Mata-mata from different basins have been recognised for a while (link opens a pdf of ), reflecting the molecular split between species. Unfortunately, the main area of morphological difference is in the carapace, which isn’t in the photo I provided (if only I’d known that the species was going to split back in 2016…).

But fear not – back in 2018 Hannah Cornish did a Specimen of the Week blogpost about this very specimen, with some more useful images. The overall outline of the Grant specimen seems more rectangular than oval, which may indicate that it is an Amazon Mata-mata, making the original identification of Chelus fimbriata (Schneider, 1783) still correct – although a proper examination of the specimen would be needed to confirm that.

So a hearty congratulations to everyone who figured out what this was – and I would suggest taking a look through the comments from the mystery object, as there are some very interesting observations and discussions about that strange skull which are well worth a read. That’s the kind of thing that I love most about running this blog!

Friday mystery object #401 answer

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.

Variation of the squamosal in A. Macrochelys temminckii and C. Macrochelys suwanniensis. Adapted from Thomas et al. 2014. Zootaxa 3786(2):141–165

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!

Friday mystery object #87 answer

On Friday the mystery object was provided by Mark Carnall, the curator of the newly reopened Grant Museum of Zoology:

It’s not been an easy one to work out – I thought it was part of a fish skull when I first saw it and comments have ranged from a squashed frog to Yoda’s foot.

The closest suggestions came from Jamie Revell, Steven D. Garber, PhD and Helen (sort of…), this is the  Continue reading