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What is this from the Wilson Clay Pit?


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My dad found this unusual specimen at the Wilson Clay Pit. Neither of us have any idea of what it could be. Could it be some type shark cartilage? I have no experience with Paleozoic shark cartilage. The scale is in centimenters...

post-18428-0-97181500-1469918920_thumb.jpg post-18428-0-29081300-1469918929_thumb.jpg

Thanks for any help you can offer...

As a side note, here is something else my dad found about a year ago at the Wilson Clay Pit. I thought it was drool-worthy... :)

post-18428-0-60255200-1469919458_thumb.jpg

Edited by dre464
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The last one is indeed droolworthy. The largest Petalodus tooth I have seen...and the detail is exquisite.

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If that is cartilage the striations look a bit like what I've seen on a large dorsal fin but if so it would be huge. I've also seen similar texture on the roots of some Pennsylvanian shark teeth but again, it would be a monster. There is so much we don't know about these fish your find could be important for study if Dr. Maisey confirms it is shark material.

Dallas Paleontological Society is considering having it's Brownwood area field trip sometime in October. It got rained out in the spring. Sometimes we manage to get permission to collect on private property in the area so keep up with our calendar if you want to join in.

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Canadawest - I'm so jealous of that tooth! When my dad found it, we had no idea what it was. We had never heard of a Petalodus before. Imagine our excitement when we discovered what it was!

DPS Ammonite - I'm going to send Dr. Maisey an email this evening. Hopefully he can shed some light on this, since we have several pieces that are similar...

BobWill - My dad, brothers and I were actually out at the Wilson Clay Pit on the day that the DPS was scheduled be there (not intentionally, we found out about the DPS trip a few days before we left). We found a back way in to the site after we discovered that the Jim Ned Creek was WAY out of its banks. I was hoping to meet some of y'all! The ground was a bit soggy, but it was a pleasant day and very little mud was tracked back into my van! I found the usual stuff (crinoids, brachiopods, etc.). Both of my brothers found trilobites. My dad found this piece, along with a rare echinocystid echinoid that I posted about here.

Anyway, my dad and I have discussed joining the DPS as well as the HGMS. We'll probably be joining soon! Thanks for the invite!

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I sent Dr. Maisey an email about this specimen. He was good enough to get back with me...

"Many thanks for your email and photos. This certainly has the appearance of chondrichthyan mineralized cartilage. The 'grainy' texture and scattered small pores suggest a form of "tessellated calcified cartilage", similar to that in modern sharks etc., in which the cartilage has a superficial 'rind' of small 'tesserae', like a Roman mosaic. In your example, many of the tesserae are partially fused to their neighbors, leaving the small pores marking their original boundaries. We rarely see this in modern sharks (the tesserae are usually always distinct), but I have seen semi-fusion of tesserae in big pieces of Carboniferous shark cartilage, usually in the back part of the braincase. Your piece doesn't look like it came from the braincase; it is flat and rather plate-like, and could have come from part of a jaw (that's just a guess).
Your scale bar shows that this was from a really large individual. I have been working on fragments of shark braincases from the Finis Shale (also late Pennsylvanian). I estimate that those sharks were approx 5m. total length, based on comparison with smaller but more complete fossils (I hope to submit a paper about them very soon).
Although I cannot identify what kind of shark your cartilage represents, the big Finis Shale fossils seem to be from ctenacanths. I also know of really large cladodont (Glikmanius-like) teeth from the same locality (Jacksboro Spillway), which is the normal tooth-type for a ctenacanth. I also know of a large partial braincase from the Cleveland Shale (undescribed, but perhaps even bigger than the Jacksboro sharks). There are also really big ctenacanth teeth in the Permian.
We don't find remains of sharks this big again until the Cretaceous, and those are all lamnids (as was 'megalodon' in the Mio-Pliocene). So it is possible that 'suspershark' status (somewhat arbitrary; = sharks over 5 meters long) evolved in only two shark lineages (ctenacanths and lamnids)."
My dad and I are very excited about the find. And Dr. Maisey was very generous in the time he took to help us identify it.
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Can you tell Dr. Maisey is excited about the new/old "supersharks"? We need to find enough of these (with associated teeth would be nice) to give these things a proper name. I thought he was going to submit the paper after he presented a poster on these at the last SVP annual meeting. Since then I heard about some even newer material. Maybe he got to have a look it at before sending the paper in.

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fifbrindacier

I sent Dr. Maisey an email about this specimen. He was good enough to get back with me...

"Many thanks for your email and photos. This certainly has the appearance of chondrichthyan mineralized cartilage. The 'grainy' texture and scattered small pores suggest a form of "tessellated calcified cartilage", similar to that in modern sharks etc., in which the cartilage has a superficial 'rind' of small 'tesserae', like a Roman mosaic. In your example, many of the tesserae are partially fused to their neighbors, leaving the small pores marking their original boundaries. We rarely see this in modern sharks (the tesserae are usually always distinct), but I have seen semi-fusion of tesserae in big pieces of Carboniferous shark cartilage, usually in the back part of the braincase. Your piece doesn't look like it came from the braincase; it is flat and rather plate-like, and could have come from part of a jaw (that's just a guess).
Your scale bar shows that this was from a really large individual. I have been working on fragments of shark braincases from the Finis Shale (also late Pennsylvanian). I estimate that those sharks were approx 5m. total length, based on comparison with smaller but more complete fossils (I hope to submit a paper about them very soon).
Although I cannot identify what kind of shark your cartilage represents, the big Finis Shale fossils seem to be from ctenacanths. I also know of really large cladodont (Glikmanius-like) teeth from the same locality (Jacksboro Spillway), which is the normal tooth-type for a ctenacanth. I also know of a large partial braincase from the Cleveland Shale (undescribed, but perhaps even bigger than the Jacksboro sharks). There are also really big ctenacanth teeth in the Permian.
We don't find remains of sharks this big again until the Cretaceous, and those are all lamnids (as was 'megalodon' in the Mio-Pliocene). So it is possible that 'suspershark' status (somewhat arbitrary; = sharks over 5 meters long) evolved in only two shark lineages (ctenacanths and lamnids)."
My dad and I are very excited about the find. And Dr. Maisey was very generous in the time he took to help us identify it.

Great finds, congratulations to both of you :yay-smiley-1:

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