Quiz - What Are These Odd Little Bones ?

[Harry Pristis]

Here's another quiz -- what are these odd little bones?

I'll tell you which animals produced these examples; but, you tell us what they are. A Golden Kudo for identifying the bones. Style points for amplification of your answer -- tell us what you can about them.

[Cris]

Navicular bones?

[Nicholas]

Radius bone?

[worthy 55]

I am going to say Proximal Sesamoids?

[Carl]

Pisiforms?

[TourmalineGuy]

I'm going to agree with Worthy, based on the clues. I'll add some detail though...sesamoids are bones that are completely surrounded by tendon and other connective tissue. The patella is a good example of a sesamoid bone that most people know about. There are plenty more details to be added, like their actual function, but I'll let someone else chime in.

Incidentally, if these are sesamoids, where in the world do you find references that help identify them. As some may be aware, I bring home a lot of odd lumpy bones....

[siteseer]

Here's another quiz -- what are these odd little bones?

I'll tell you which animals produced these examples; but, you tell us what they are. A Golden Kudo for identifying the bones. Style points for amplification of your answer -- tell us what you can about them.

Harry,

In another thread I pointed out that a fossil hunter checking out a quarry should first try going through previous collectors' dump piles before doing his own digging. Some small mammal bones look like rocks to the uninitiated and the ones you are showing are good examples.

Going by general shape I will say magnum, one of the wrist bones.

[Harry Pristis]

A Golden Kudo to 'Carl' who identified these three bones as pisiforms. Way to go, Carl!

No style points awarded, though 'TourmalineGuy' provided good information about sesamoids in general...he just had the wrong bone. Tarsal and carpal and sesamoid are guesses in the right neighborhood, but Carl was specific.

Pisiforms and patellae are a type of bone called sesamoids.

Here is a description 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 when he's sorting gravel or checking another collector's dump pile? Sesamoids 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.

Thank to all who participated.

--------Harry Pristis

Comparative Variability of

Intermembranous and Endochondral Bones in Pleistocene Mammals

Kristina R. Raymond and Donald R. Prothero

Palaeo-Electronica (March 2010)

"In particular, variability due to different styles of growth between endochondral bones (which ossify directly from an embryonic cartilaginous precursor, often constrained by joints and articular surfaces) and less constrained intermembranous bones, is highly relevant to these issues.

"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 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 sesamoid 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." [emphasis added]

[JohnJ]

Good info Harry. Thanks.

[worthy 55]

WTG Carl.

[TourmalineGuy]

Thanks Harry,

Your quiz posts always send on wonderful tangents of research. Now, what "minor exceptions" are Palaeo-Electronica referring to for the non-ossified adult patellae...?

[Harry Pristis]

Thanks Harry,

Your quiz posts always send on wonderful tangents of research. Now, what "minor exceptions" are Palaeo-Electronica referring to for the non-ossified adult patellae...?

I think it may be kangaroos that have poorly-ossified knee-caps. What with minimal predator-pressure, it's the reason they spend a lot of time lounging about.

[Carl]

A Golden Kudo to 'Carl' who identified these three bones as pisiforms. Way to go, Carl!

No style points awarded, though 'TourmalineGuy' provided good information about sesamoids in general...he just had the wrong bone. Tarsal and carpal and sesamoid are guesses in the right neighborhood, but Carl was specific.

Pisiforms and patellae are a type of bone called sesamoids.

Here is a description 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 when he's sorting gravel or checking another collector's dump pile? Sesamoids 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.

Thank to all who participated.

--------Harry Pristis

Comparative Variability of

Intermembranous and Endochondral Bones in Pleistocene Mammals

Kristina R. Raymond and Donald R. Prothero

Palaeo-Electronica (March 2010)

"In particular, variability due to different styles of growth between endochondral bones (which ossify directly from an embryonic cartilaginous precursor, often constrained by joints and articular surfaces) and less constrained intermembranous bones, is highly relevant to these issues.

"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 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 sesamoid 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." [emphasis added]

Woohoo! I just got lucky. I'm no mammal guy, but I found one of these on Jacksonville Beach in Florida years ago. I showed it to Malcolm McKenna who immediately IDed is as a horse pisiform. I've remembered that shape ever since.

[Harry Pristis]

Woohoo! I just got lucky. I'm no mammal guy, but I found one of these on Jacksonville Beach in Florida years ago. I showed it to Malcolm McKenna who immediately IDed is as a horse pisiform. I've remembered that shape ever since.

You did good, 'Carl'! I only hope that this thread will make a comparable impression on a few subscribers here.

[barefootgirl]

Thank you Harry. I always enjoy and love learning from your educational posts.

[Jesta384]

Navicular bones?

1 up.

i may be new to all this but it still loks like a tarsal bone to me. even hoough the quiz had ended. im still happy enoough with myself to have gotten fairly close

edit: even if the location is a little different then humans!

Edited April 10, 2010 by Jesta384

[Harry Pristis]

For folks interested where exactly in a horse the pisiform bone lies--take a look at the web page over at http://chestofbooks.com/animals/horses/Health-Disease-Treatment-2/Carpus-Or-Knee.html ; the pisiform is one of the truly odd little bones that helps articulate the carpus (or knee) area of the horse (front legs), an area analogous to the human wrist. As such, it is technically a carpal bone. You'll find at that web page that the pisiform (labeled "2") lies between the radius above ("1", the long bone below the humerus, which of course connects with the scapula, shoulder) and the outer small metacarpal bone ("5") below. There are seven, sometimes eight little compact bones in the carpus, all of which can be easily fossilized. For example, I've run across numerous trapazoids ("9") and scaphoids ("6) in the Middle Miocene Barstow Formation and the Upper Miocene Dove Spring Formation, Mojave Desert, California.

My idea, of course, was that the mystery bones represented cuboids. Those bones lie in the tarsus, or hock region--the main joint of the hind legs, between the tibia above (long lower leg bone) and the small and large metatarsals below. Take a look at the web site over at http://chestofbooks.com/animals/horses/Health-Disease-Treatment-2/The-Cuneiform-Parvum.html for a look at all the bones that comprise the hock; including the tibia and matatarsals, there are eight of them. Probably the most easily recognizable tarsal bone is the astragalus, which can be fossilized quite easily, owing to its compact nature.

Here's a camel astragalus I spotted a number of years ago in the Upper Miocene Dove Spring Formation, California.

http://inyo1.110mb.com/redrock/bones4.html

Hello, 'Inyo' . . . welcome to the Forum! I've admired your images in a different venue in the past.

Yes, pisiforms are both carpals and sesamoids. The terms all have slightly different meanings, and should be used with discrimination. But . . . pisiforms just get NO respect! Even in the illustration you offered us, pisiform is pointed out but is not illustrated very well. It's hidden behind the cuneiform. No respect, I tell ya'!

If you're into post-cranials, I am always interested in trading bones for comparative material.

------Harry Pristis

Edited April 13, 2010 by Harry Pristis