Patella?

[endorph1n]

Found this at guana park (between ponte Vedra and st Augustine) on the beach. I showed it to an orthopedic surgeon/fossil expert I know and he thought it might be a sloth patella. I honestly don't know.  I also found a nice shark's tooth in the same area. I'm pretty sure it's a great white. 

[sixgill pete]

Yes, I would say the tooth is a great white. As far as the bone, to me it just looks like a random piece of bone. However, I am definitely not an expert.

[Harry Pristis]

Here's a sloth patella for comparison:

 

 

[endorph1n]

Thank you for the reply. I'm thinking yes for patella but no for a sloth.  It appears to be completely intact (ie not a bone fragment).  Any other ideas?

[endorph1n]

[Plax]

If you see a lot of pores the bone isn't intact. Not saying it isn't a patella (I have no idea).

[endorph1n]

This might be semantics. If by "porous", you mean it's missing bone matrix, then yes.  By intact, I mean there is no fracture, it's the complete bone...

[Fossildude19]

21 minutes ago, endorph1n said:

This might be semantics. If by "porous", you mean it's missing bone matrix, then yes.  By intact, I mean there is no fracture, it's the complete bone...

 

I think  what Plax is saying is, that this is a extremely waterworn fragment of a larger bone. 

 

The porous texture isn't usually readily visible on intact bones. So at some time in the past, this was broken. But it has spent allot of time rolling around in either surf or river environments.

Wave action (sand and water tumbling )  does a number on glass in a short time - think about something getting broken, then buried, then getting wave tumbled after thousands or millions of years. 

The sharp fragments or splinters get worn away, and polished fairly quickly, geologically speaking.  

Regards,

[endorph1n]

Ok gotcha, I didnt realize that and thank you for that clarification. It looked intact to me but, if it is just a bone fragment, I suppose it could be a lot of different things. 

[Fossildude19]

1 minute ago, endorph1n said:

Ok gotcha, I didnt realize that and thank you for that clarification. It looked intact to me but, if it is just a bone fragment, I suppose it could be a lot of different things. 

 

True. The first thing I thought of was that it looks like an end of a long bone, but the flat side is throwing me off. 

 

You could just label it as "Chunkosaurus problematicus."  

[endorph1n]

Lol. I'm an MD and former biology major but, I have to admit non human bones (over millions of years) throw me for a loop. I'm amazed and quite impressed with some of the IDs made here, it's fun to see. The one biggest clue (I believe), is the smooth, long oval, articular surface where it joined another bone. (I think it's an articular surface anyway). 

 

Could this be a whale vertebrae with the transverse and spinous processes worn off?

 

Thx again 

[endorph1n]

PS my orthopedic surgeon colleague tells me that the hole with the tiny seashell stuck in it is a bone cyst.  

[Fossildude19]

I think the hole with the shell may be a boring hole from a piddock clam. 

It could be a whale vertebra, but, again, with so much wear it is hard to tell. 

The "articular" surface may just be wear as well. I think it might be difficult to ID any further than Mammal bone frag.

Regards,

 

[Harry Pristis]

I'm interested in this because I've recently struggled to identify nondescript bones which turned out to be sesamoids (patellae are not the only intermembranous bones).  i'm not certain about the mystery bone here, but there's a decent chance it's a patella or another, less diagnostic, sesamoid.  Here are some images of a rather large sesamoid that I haven't been able to ID to a particular animal.

 

Here is a description taken from Palaeo-Electronica (March 2010) which divides mammal bones into two types:

 1. endochondral bones (which ossify directly from an embryonic cartilaginous precursor, often constrained by joints and articular surfaces). These would include all limb bones, for example, and,

 2. intermembranous bones which are less constrained. 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. Humans have only one sesamoid, the pisiform in the carpus.

 Sooo... How can a collector identify a sesamoid or patella when he's sifting gravel or checking another collector's discard pile? Sesamoids (particularly pisiforms) and patellae have articular facets, often two facets, on what may be an otherwise undistinguished lump of bone.  How can you identify them to species? ...You'll have to take 'em to the local museum where they may be able to help you.
 _________________________

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."

[endorph1n]

Interesting.  Thank you

[minnbuckeye]

19 hours ago, Harry Pristis said:

 "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

This statement brings back memories of when I injured my knee many years ago. I visited Mayo Clinic's Orthopedic Department. After an exam and taking X-rays, I met back with the Doctor to discuss my problem. When she entered the room, there were about 8 other individuals with her. She explained they were students and asked if I minded their presence. I did not. Next she proceeded to bring up the images of my knee and began to ask questions to the students. They seemed like a very knowledgeable group until she pointed at 2 structures on the screen and asked what they were. Silence permeated the room until I could take it no longer. I blurted out sesamoid bones.  All eyes including the Doc turned towards me and looks of bewilderment abounded when she said that I was correct!! I thought how can these Docs to be not know this, never realizing people do not have sesamoids. I guess I must be low on the evolutionary tree. Maybe that explains my tail!

[siteseer]

I've been puzzling over this for the past half-hour or so.  From the first view, I had no idea, but from the second, it had the general form of a magnum, a carpal bone.  If so, it would be a large animal - as large or larger than an elephant seal which leads me to walrus if I had to make a guess based on such thin evidence.  The problem is that first view (and third) do not resemble another view of what I expect of a magnum.  It is worn, though - hard to say.

 

Jess

 

 

[endorph1n]

Interesting!  After doing some searching, I think you might be right.  Is that the same thing as a "capitate" bone?  Thank you for the information.