It’s the last day of 2010, so I thought I’d see the old year out by trying something a little bit different for this week’s mystery object. Rather than giving you one object and asking for an identification, I’m giving you two and asking whether they are from two individuals of the same species or if they are from two different species. Obviously there is kudos riding on identifying the species involved as well.
So here you go – can you spot any differences between A and B and are they enough to suggest that A and B are from different species?
As usual, please add your observations, questions and suggestions below and I’ll do my best to provide what information I deem appropriate. Good luck and a very Happy New Year!
Zygoma 
do both the bones bone each other?
and if so, do they have viable bonespring?
The bones don’t come from the same place, so they couldn’t have met to produce bonespring. however, the same is true for the individuals of many species.
ok, they’re two variants on the same genetic theme.
from two isolated populations, so even if systematists call them the same species, Ernst Mayr would have to disagree.
Ernst Mayr would definitely disagree in this instance…
They are right humerus from something big heavy and slow.
I don’t know if they are from the same animal because they look so different from any of my bones already.
Certainly from something big, although not necessarily slow… and they’re not humeri (that’s the plural of humerus) believe it or not!
I did mean thigh bone, honest ! I know it’s a back leg bone.
Firstly, obviously, there’s a size differential, that could nevertheless be intraspecific variation – without a larger sample I’d assume that.
There appears to be curvature on the greater trochanter of B, creating a sort of lip curving towards the head. And the lateral condyles may be a different shape but I suspect this is the angle of the photograph
Otherwise the biggest differences look like they’re in the neck region – the head of A is more pronounced fromm the neck, which tapers just under the head. B’s head transitions more smoothly into the neck (kind of like my Dad). B’s neck also appears to be an a shallower angle to the shaft, and extends down the shaft some way.
However, I’m buggered if I know whether these differences are enough for speciation. I’d be happier with a largwer sample size.
Aha – sample size, I was hoping someone would pick up on that. Your observations are good and you are right in being cautious.
The specimens were photographed at the same relative orientation, so pretty much all of the variation comes from the specimen morphology rather than from angle, although this is another good point, since photographs can be misleading!
On my deer humeruses the bit near the “knee” is flat. On these, the bit near the knee is an an angle. Maybe the humerus comes away from the hip at an angle instead of straight down.
FEMUR !
😉
This is a very good observation – the angle of this femur in relation to the hip is very different to that of a deer!
I reckon they could be from completely different genera. We could be looking at a group where the postcrania are all much of a muchness, but soft tissues or skull morphology might be really distinctive.
Another good point. Postcrania require a lot more expertise (or at least access to good comparative material) to identify than skulls do. The objects here are single bones, whereas a skull is made up of numerous bones (and in some cases teeth) which provides more scope for variability.
I want to say they look a bit like something a dog would chew on… but thats just a gut instinct. I haven’t the faintest idea beyond that.
I wouldn’t give one of these to a dog – it might choke…
As others have said, they’re femurs. As to whether they are of different species, I’m going to guess that they are. I suspect the difference in size means little, since obviously not all animals are the same size (just for starters, one might be a male and one a female).
But the lateral condyles (lump on bottom left corner) do not appear to be the same shape, and the intercondylar fossa (notch thing between lumps on the left end) is noticeably deeper and narrower on the upper specimen, with the linea aspera (ridge-like thing running down the length of the bone) also appearing to be more deflected laterally on the lower specimen. I’d guess these are sufficient for them to be from different species, although I fully admit that is just a guess.
Guessing the species is rather beyond my expertise!
Neatly described reasons for opting for them being from different species!
I think they might be different types of rhinos, but it’s only a guess.
I think they are different types because they are different sizes and the top and bottom have fused on so they have stopped growing. The groove at the knee end looks different too and B’s groove is wider.
Great observations – the legs have indeed stopped growing, so these aren’t just from animals at different stages in their growth.
Not Rhino though!