I hope that you had a very merry festive season and that you didn’t spend too much time contemplating last week’s mystery object from a dig by Irish Archaeological Consultancy that’s been taking place in Dublin:
Because the object is still partly in the soil and I was unable to get images from every angle and I think that there are some helpful features still buried, so I apologise for that. Still, we can take a look at what we know and start narrowing down possibilities.
First of all, we know that this is the lower part of the hind limb of a bird. That much is clear due to the shape of the articulations, in particular the lobed shape of the distal end of the tarsometatarsus (or TMT, which is the long bone in the image that is intact apart from a hole in the midshaft).
Considering that based on the scale bar the total length of the TMT must be around 380mm, this is clearly from a VERY big bird. The largest bird species occurring in Ireland would be the Great Bustard, which has a TMT length of between 138 and 176mm in the males (which are significantly larger than the females). So that’s not even close.
There are birds common to Ireland which are smaller, but with longer legs, such as the Grey Heron. However, their TMT would seldom be greater than 210mm. Even the Common Crane, which has historcially be reported in Ireland, only has a TMT in the 200-250mm range – about the same as a Greater Flamingo, which is the kind of exotic bird that may have been brought to Ireland by humans as an ornamental in the last few hundred years. We need to look further afield.
The next obvious stop has to be the largest bird, to at least get a sense of just how big the TMT is likely to get. Ostriches have a TMT in the region of 448mm, so we’re not quite up to that size, but we’re also not all that far away. On a side note, as we mentioned earlier, the mystery object probably still has part of the distal articulation buried in the soil – but if it didn’t then it would be a good contender for a small Ostrich, since they only have two toes and their TMT would be missing the section of articulation that is likely buried here.
The next largest bird to consider would be the Emu, which has a TMT around 400mm. This is getting into the right sort or size range, but we should consider the other possible candidates. Staying with Antipodean species, the Southern Cassowary has a TMT in the region of 325mm long and the Northern Cassowary is around the same size. Then we jump over to South America and the rheas. The largest is the Greater Rhea, for which I could only find a measurement of 320mm, which was taken from one male specimen.
Based on size alone this suggests that Emu is the most likely option, but we all know how size can be a bit unreliable. The next thing to look at is probably the shape of the unguals (those are the ends of the digits where the claws would attach):
In most ratites the ungual on the middle digit seems to have quite a flat profile, but from the images I’ve seen of skeletons, the Emu appears to be the only one with a similarly curved middle ungual.
On balance (and I’d be happy to reconsider if I can get my hands on the fully excavated specimen) I think this is most likely to be the leg of an Emu Dromaius novaehollandiae (Latham, 1790) – an opinion shared by Adam Yates.
I realise there are some other extinct large ratites (various moas and the elephant birds) that may have found their way to Ireland as fairly complete fossils, but the lack of holes for wiring, and with the bones still in their correct orientation suggests that this specimen went into the ground with its skin still more or less intact.
I’d like to thank everyone for their suggestions – I’m not sure I’d call this a cut-and-dried answer, but hopefully I’ll get a chance to take a closer look at the specimen in 2022 and confirm the identity with more certainty.
Happy New Year to everyone!