Carpal id

[garyc]

I’ve been seeing more posts lately of carpals and sesamoid bones where people are having some success getting ids. Here’s one I’ve had tucked away, waiting for a rainy day to post. It’s a little worn, but maybe in good enough shape to narrow it down. It’s roughly 80mm by 78mm. 

[ClearLake]

Interesting one.  My best guess at the moment is a pisiform (accessory carpal) from something cow sized or a bit larger.  My reasoning: the general shape is similar, the lack of obvious, large facets, and the groove or slash most visible in your last picture.  I have one from a cow that looks fairly similar, but not exactly like it.  Yours would be a bit larger I believe. 

 

Check out this image below of a bison pisiform.  If you go to the website, it is a 3-D image that you can rotate to look at all sides and I think it has a lot of similarities to yours.  The rounded edge at the top (in the picture below) looks a lot like the feature I see on your second to last picture (above) by your fingers.

https://virtual.imnh.iri.isu.edu/Paleo/View/Bison/1053

 

 

[Balance]

@ClearLake the model is awesome. That’s the idea I’m thinking of for photographing my collections best example of different species shapes and nuances. The program uses photos to create the 360 rotation.  
 

I like how the museum put the fossil with the sketch. Very handy. 
 

Jp

[Harry Pristis]

I don't think this find looks much like a pisiform.  It does remind me - the ligamental groove, in particular - of this sesamoid which I think of as sloth:

 

[ClearLake]

I'm a bit confused @Harry Pristis, aren't those bones in your last picture actually pisiforms, not sesamoids?

[Harry Pristis]

3 hours ago, ClearLake said:

I'm a bit confused @Harry Pristis, aren't those bones in your last picture actually pisiforms, not sesamoids?

Pisiform bones are sesamoids, intermembranous bones with a name . . . like patellae.

 

Comparative Variability of
Intermembranous and Endochondral Bones in Pleistocene Mammals
Kristina R. Raymond and Donald R. Prothero
Palaeo-Electronica (March 2010)

 "The topic of intermembranous and endochondral bone growth, size and variability is one that is not commonly touched upon, except briefly in passing, in paleontological literature. Generally, intermembranous bones are measured and discussed as only a slightly relevant topic in regards to larger studies of species or interspecific variation and sexual size dimorphism.

 "Intermembranous bones form directly from the connective tissue late in embryological development and after birth through intramembranous ossification. Some intermembranous bones, such as the kneecap (patella), are almost always ossified in adult mammals (with minor exceptions).

 “Other intermembranous bones, known as sesamoids, occur only in areas where a tendon passes over a joint, and ossify in irregular and unpredictable patterns (Vickaryous and Olson 2007).

 "The number and shape of intermembranous bones vary greatly within the Mammalia, and are highly taxon-dependent. Humans have the patella and only one sesamoid (the pisiform) in the carpus. 

 “In many mammals, such bones include the patella and large sesamoids in the manus and pes. In ungulates, on the other hand, the only [relatively] large intermembranous element is the patella. The sesamoids in the manus or pes are small nodular ossifications in the digital flexor tendons, both at the metapodial-phalangeal joint and the distal interphalangeal joint; suids have as many as 13 sesamoids in the manus alone." 

[garyc]

Thanks for all the attention! @ClearLake and @Harry Pristis I checked out the virtual bison site. My bone is significantly larger, so I do not think it is bison. There are some similarities to the bone that Harry posted, so I am thinking it is more like sloth as well.

[ClearLake]

@Harry Pristis Thank you very much for your informative response.  Count me in as learning something new.  I had been familiar with sesamoids as the small bones near the carpals/metacarpals of many animals (always a bit of a pain in many skeletons I have reconstructed), but not really up on the more definitive/inclusive definition of the term.  I will rephrase my question concerning the last picture you posted: Aren't those sesamoid bones more specifically pisaforms?  At least the Equus one looks very much like all the modern horse pisiforms I find on the internet.

 

@garyc,glad you are feeling more comfortable with an ID for your piece.  I find it enjoyable trying to ID these items, even when I don't quite get it right.  

[garyc]

1 hour ago, ClearLake said:

 

 

@garyc,glad you are feeling more comfortable with an ID for your piece.  I find it enjoyable trying to ID these items, even when I don't quite get it right.  

I’m always happy to get a correct ID with the help of the forum. I’m ecstatic on those rare occasions when I come up with a correct ID on my own

[Harry Pristis]

1 hour ago, ClearLake said:

... Aren't those sesamoid bones more specifically pisaforms?  At least the Equus one looks very much like all the modern horse pisiforms I find on the internet.

They are pisiforms.  I have a handful of these bones.  They appeal to me because I have the obscure facts about their intermembranous origin . . . I'm happy to share those facts.

These pisiforms are relatively easy to identify, but sesamoid bones in general can be difficult.  They don't appear much in print for ID purposes.  Someone here recently pointed out my faulty ID of some sesamoids from 10 years ago, so we are becoming more aware with time and exposure.