Fossil Hand (Reptile? Therapsid?), Karoo Supergroup, Madagascar

[araucaria1959]

I bought this specimen many years ago on an exhibition. It was labeled "Saurichthys" (100 % wrong). All I know is that it's from the Karoo Supergroup of Madagascar. Since the Karoo Supergroup spans a lot of time (upper carboniferous until lower jurassic), it makes it especially difficult to asign the fossil to the "correct" order or family of tetrapods.

I don't think it's possible to identify the genus, but I would be glad to know the order.

araucaria1959

[Auspex]

Holy Toledo; Karoo material!

What size is it?

[araucaria1959]

O sorry, I forgot the scale: the longest finger about 4 cm long.

araucaria1959

[Auspex]

If I remember this correctly, one of the evolutionary hallmarks logged by the Therapsids was a more upright positioning of the legs, under the body, allowing them to breath while running (a sprawled leg posture requires a sinuous motion of the torso to run, impeding lung function). Getting the feet more on center led to more symmetrical feet, with the three inner toes longer that the two outer. Some of one outer toe is missing from your fossil, but what is there looks like it would be close to the three inner toes in size. If I have remembered this correctly, and if my assumption about the missing phalanges is correct, then this is not a Threapsid.

[araucaria1959]

Thank you very much - your ideas gave me reason to look at the counterpart, that I have, but it's condition is worse so I didn't pay so much attention to it and didn't post pics. But it shows four of the fives toes completely.

The phalange formula is: 2 - 3 - 4 - 5 - 3(or more) (last toe incomplete).

This does in fact exclude most orders of therapsids and points to reptiles or basal synapsids like pelycosauria, but it's also compatible with few therapsids like Cynodontia, and the size of the toes/digits increases from toe/digit 1 to 4.

Maybe the new pictures can help. I know it is very difficult to say something about that specimen except for someone who collected Karoo fossils himself.

araucaria1959

[sward]

Sorry I can't help with the identification, but it is a fascinating fossil.

I'll keep an eye on this thread to see what others have to say.

Thanks for posting it.

[Auspex]

Maybe dinodigger will see this thread and weigh in.

[piranha]

Is this possibly a large Mesosaurus?

[piranha]

Here are a couple of other Permian reptilesfrom Madagascar:

Claudiosaurus

Hovasaurus

[siteseer]

The last time I saw a specimen like that was maybe 12-15 years ago. It was from that site where they found the nodules with Triassic fishes (sometimes a coelacanth) and shrimp (shrimp-like at least) inside. Rare finds included feet of a reptile identified as Tangasaurus. It was weird that nodule formed around just a foot. As I recall, the toes were about the size you noted.

I bought this specimen many years ago on an exhibition. It was labeled "Saurichthys" (100 % wrong). All I know is that it's from the Karoo Supergroup of Madagascar. Since the Karoo Supergroup spans a lot of time (upper carboniferous until lower jurassic), it makes it especially difficult to asign the fossil to the "correct" order or family of tetrapods.

I don't think it's possible to identify the genus, but I would be glad to know the order.

araucaria1959

[Auspex]

It appears that Tangasaurus specimens from Madagascar have been renamed Thadeosaurus. LINK

[dinodigger]

Wow! COOOOOOOL!!! Very similar to our Permian pals here in North Texas; definitely looking towards reptile or synapsids as mentioned. I don't think Pelycosauria; I noticed the really flat distal ends of the toes; all of our Pelycosaurs have nicely rounded distal ends of their carpals and tarsals; on a stretch they are similar to the Captorhinids; I'm not too familiar with the paleontology of the area this specimen is from. Congrats. Great piece and it has A LOT to offer for osteology of this guy.

CF

[araucaria1959]

Thank you very much for the answers. It seems to be a basal diapsid. From the genera under discussion, Hovasaurus seems to fit best.

Captorhinus was too small with regard to the size of my specimen. In Mesosaurus, the metacarpals of the lower feet are much longer (relative to the phalanges) than in my specimen; in the upper feet (hand), the length of the longest digit does not exceed the length of ulna and radius as is the case in my specimen (if it is hand at all).

The group around Claudiosaurus fits better. If it's one of them, it can only be a lower foot because of its size; hands (upper feet) are smaller and more gracile and the distal end of the humerus is extended.

The distal phalanges of my specimen are curved, especially in (pedal) digits I und II and to a lesser extent in digits III and possibly IV; furthermore, the proximal phalanx of digit V is longer than the proximal phalanx of digit IV.

From the genera under discussion here, Hovasaurus fits best with that pattern. In Claudiosaurus, the distal phalanges are not curved, and the proximal phalanx of digit V is smaller than that of digit IV.

In Thadeosaurus, the curvature of the distal phalanges fits to my specimen, but the metacarpals of digits II, III and IV increase in length considerably (from II to IV), while they are about the same length in my specimen, at least in digits III and IV.

I didn't find good pictures of the skeleton or the feet of Tangasaurus to compare my specimen with that genus; maybe this is due to the suggestion that Tangasaurus is no longer valid.

In Hovasaurus, the distal phalanges are curved in the same way as in my specimen, metacarpals III and IV are of nearly equal size, the proximal phalanx of digit V is longer than that of digit IV, and the total length of digit IV (and possible III) (digit V is not fully preserved in my specimen) exceeds the length of tibia and fibula. Taken together, this is the closest match to the genera that have been proposed here - which doesn't exlude the possibility that there were allied genera that may even fit better.

http://www.google.de/imgres?q=Claudiosaurus&hl=de&tbm=isch&tbnid=pPDpv7T_eG2A3M:&imgrefurl=http://www.reptileevolution.com/claudiosaurus.htm&docid=DAlAL9C3kjkPqM&imgurl=http://www.reptileevolution.com/images/archosauromorpha/diapsida/enaliosauria/claudiosaurus588.jpg&w=588&h=265&ei=EIZ6UP_xGIS1hAeotoCoBw&zoom=1&iact=hc&vpx=69&vpy=495&dur=79&hovh=151&hovw=335&tx=149&ty=89&sig=117733986229181543847&page=1&tbnh=89&tbnw=197&start=0&ndsp=21&ved=1t:429,r:10,s:0,i:103&biw=1246&bih=857

So I suggest to label that specimen as "basal diapsid, probably basal younginiform, possibly Hovasaurus sp.; lower leg; upper permian or lower triassic" - at least until I know better.

Thanks again,

araucaria1959

[araucaria1959]

One correction:

For reasons I don't understand, the link in my post above leads to a page for Claudiosaurus (though the URL was copied directly from the Hovasaurus-page); to get to Hovasaurus, it is necessary to click on the word Hovasaurus in the fourth line.

araucaria1959