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Quiz - Identify This Bone If You Can.


Harry Pristis

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Here's a quiz: What is this bone and what taxon does it represent?

There are representatives of this taxon found world-wide over a long span of geological time. You might find a homologue in NJ or VA or MD or TX or many other places (not a geographical clue...just a tease for all the collectors in those states!).

Share your deductive reasoning. Partial answers may earn approbrium but win no gold.

post-42-12530486994787_thumb.jpg

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Marine or terrestrial?

I will give an answer to this query even though this is not a "20 Questions" format: . . . Yes. :rolleyes:

The image shows a Miocene specimen from Florida; but, this is a conservative taxon, so you could expect to see a similar shape in homologues both earlier and later.

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I'll take a wild guess, based on a picture in a book and the size of the bone. And that is seems to have multiple joint surfaces. Is it a crocadilian Astragulus?

Dan

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I will give an answer to this query even though this is not a "20 Questions" format: . . . Yes. :rolleyes:

...

Come on Harry; are you trying to humer us? :D

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I'll take a wild guess, based on a picture in a book and the size of the bone. And that is seems to have multiple joint surfaces. Is it a crocadilian Astragulus?

Dan

I too was thinking along those lines, however I was thinking calcaneum...but to what I am not sure.

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I too was thinking along those lines, however I was thinking calcaneum...but to what I am not sure.

I was thinking along these lines as well, but I think it is not long enough for a calcaneum.

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I was thinking along these lines as well, but I think it is not long enough for a calcaneum.

Agreed most appear to be elongate, perhaps the tarsals or carpals.

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Agreed most appear to be elongate, perhaps the tarsals or carpals.

I think that is closer... something like a scaphoid? I'm really not very good at isolated bones.

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I'll take a wild guess, based on a picture in a book and the size of the bone. And that is seems to have multiple joint surfaces. Is it a crocadilian Astragulus?

Dan

Yes, John, I was trying to avoid answering the question. When you find such a bone in stream lag deposits, there won't be any opportunity to ask 20 questions.

For the sake of this quiz, assume that you just found this bone on a gravel bar at the mouth of a river where it meets the sea. All the surrounding sediments you can identify are Tertiary in age. You're alone on the beach with only three or four field guides in your backpack to help with an ID. :unsure:

Now, 'Pool Man' has the right idea . . . take the bit of information you have, and make some comparisons and deductions. His guess of "crocodilian astragalus" fits the clues nicely, though it is wrong. I'm not sure I've ever found a crocodilian astragalus . . . anyone have an image?

So, don't give up. This bone is a common fossil, though not very common (in my experience) from this well-known animal. I'm not sure why that is.

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Here's a quiz: What is this bone and what taxon does it represent?

There are representatives of this taxon found world-wide over a long span of geological time. You might find a homologue in NJ or VA or MD or TX or many other places (not a geographical clue...just a tease for all the collectors in those states!).

Share your deductive reasoning. Partial answers may earn approbrium but win no gold.

post-42-12530486994787_thumb.jpg

I thought I had a specimen just like that but maybe I just saw one recently. Is it a sea turtle calcaneum?

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I thought I had a specimen just like that but maybe I just saw one recently. Is it a sea turtle calcaneum?

Turtle is what I've been thinking since this was posted, but I couldn't even begin to guess which bone.

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Several posters are dancing around the correct answer.

One or two have the correct bone, but the wrong taxon. One or two have the correct taxon but the wrong bone. Most have deduced the correct SUPERLEGION or even the correct SUPERCOHORT (I was looking for an excuse to use new words!). :)

I take that to mean we're close to the point of diminishing returns for this quiz.

There's still a golden kudo waiting for the most persistent; but, I'll post the answer tomorrow mid-day.

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Astragali of a Tapir ? :unsure::unsure:B)B)B):)

A tapir astragulus looks much like that of a horse - the single pulley as opposed to the double pulley of an artiodactyl.

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based on structure of the bone i would say its a calcaneum. I say it is some form of turtle calcaneum ( Testudines? ). Based upon the fact you mention its a conservative taxon, you could expect to see similar shape in homologues both earlier and later. Turtles first appeared in the cretaceous (approx 110mya) and have remained structurally similar over this period (conservative taxon) and due to this you can expect that the structure of their foot articulation would remain similar, homologous structures (between differring genus/species). They are extant, and quite common and have a global distribution, and as far as my research tells me turtle calcaneum are relativley rare. (couldnt find any examples on the web so really im sorta guessing....a relativley educated guess :P )

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based on structure of the bone i would say its a calcaneum. I say it is some form of turtle calcaneum ( Testudines? ). Based upon the fact you mention its a conservative taxon, you could expect to see similar shape in homologues both earlier and later. Turtles first appeared in the cretaceous (approx 110mya) and have remained structurally similar over this period (conservative taxon) and due to this you can expect that the structure of their foot articulation would remain similar, homologous structures (between differring genus/species). They are extant, and quite common and have a global distribution, and as far as my research tells me turtle calcaneum are relativley rare. (couldnt find any examples on the web so really im sorta guessing....a relativley educated guess :P )

Nice, detailed rationale for your guess, 'kauffy'! I can see that you are absorbing knowledge at a prodigious pace. But, it's not turtle. In fact, 'siteseer' has already proposed "sea turtle calcaneum."

The mystery bone is a calcaneum . . . hats off to those that identified the bone.

This calcaneum is crocodilian -- a late Miocene Alligator mississippiensis.

Superlegion REPTILIA

Sublegion ARCHOSAURIA

Supercohort CROCODYLOTARSI

Superorder CROCODYLOMORPHA

Order CROCODYLIA

Suborder BREVIROSTRES

In my experience, these are not very commonly found as fossils. (What's your experience, Nate?) I don't think I have ever found the articulating astragalus.

Thanks for participating!

post-42-12531262272321_thumb.jpgpost-42-12531261903023_thumb.jpg

Edited by Harry Pristis
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This was a very educational thread and very enjoyable. Thanks Harry and everyone who had input. This is just one of several reasons I love this forum.

But what do I know I think tracers cat is cool. But really thanks guys.

Edited by Seldom
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PrehistoricFlorida

In my experience, these are not very commonly found as fossils. (What's your experience, Nate?) I don't think I have ever found the articulating astragalus.

post-42-12531262272321_thumb.jpgpost-42-12531261903023_thumb.jpg

I have found several alligator astraguli, but only one calcaneum.

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Ah, the fact that it is crocodilian would explain its appearance to me... From my perspective anyway. It was fun.. Thank you

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Nice, detailed rationale for your guess, 'kauffy'! I can see that you are absorbing knowledge at a prodigious pace. But, it's not turtle. In fact, 'siteseer' has already proposed "sea turtle calcaneum."

The mystery bone is a calcaneum . . . hats off to those that identified the bone.

This calcaneum is crocodilian -- a late Miocene Alligator mississippiensis.

Superlegion REPTILIA

Sublegion ARCHOSAURIA

Supercohort CROCODYLOTARSI

Superorder CROCODYLOMORPHA

Order CROCODYLIA

Suborder BREVIROSTRES

In my experience, these are not very commonly found as fossils. (What's your experience, Nate?) I don't think I have ever found the articulating astragalus.

Thanks for participating!

post-42-12531262272321_thumb.jpgpost-42-12531261903023_thumb.jpg

oops i must have missed siteseer's post!

Great thread Harry! make some more, they are a lot of fun!

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oops i must have missed siteseer's post!

Great thread Harry! make some more, they are a lot of fun!

Yes, that was a great one. It had me looking through my books and articles (couldn't find one book that might have had the answer). I thought I had it with sea turtle because I have seen a bone like that from Sharktooth Hill where crocs are almost off the list (one or two teeth at the Buena Vista Museum) but sea turtles are merely uncommon (most often-found remains would be shell elements from a leatherback).

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