Happy New Year!
On Friday I gave you these two bones to compare, asking whether you thought they were from the same species.
There were some excellent responses with useful observations reflecting some of the difficulties faced when trying to identify postcrania. Unlike skulls which are composed of several bones forming a composite structure, including highly diagnostic elements (teeth for example), postcrania tend to be a bit more limited in the number of diagnostic characters visible. That said, the shape of the articulation points, the grooves and crests from tendons and ligaments, the scars from muscle attachments and the holes from nerves and blood vessels can all provide clues as to what a bone belonged to.
Size can also provide a clue, but as pointed out by Debi Linton:
…there’s a size differential, that could nevertheless be intraspecific variation…
This is a valid point – size can vary within a species for all sorts of reasons, the most obvious being the age or sex of the animal. However, in this instance the size difference is accompanied by quite a substantial set of differences in shape that go beyond what you would expect to find within a species. So well done to Dave Godfrey, Jamie Revell and Jake for making that deductive leap! That said, Debi also deserves congratulations for identifying the differences and then exercising caution in the light of insufficient information – it may be unsatisfying to say I’m not sure, but it’s often the only truly correct answer available.
That said, I’m a little surprised that nobody worked out what these femurs were from. The bottom one (B) has a small area of damage on the proximal end (the end nearest the body), which shows a honey-comb structure in the bone beneath. Jake also spotted that the angle at which these femurs would articulate with the hip would be unlike a deer – or other mammal in fact. These are the femurs of two species of bird – very big birds for that.
Any idea which species?