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Hello everyone, This post is really late, but better late than never right! Several months ago, I posted a tooth that I found in Late Mississippian Pennington Formation in East Tennessee in the Fossil ID section, whereupon I was referred to some experts in the UK. After a conversation with two experts about the tooth I had found, it was identified as a Megactenopetalus sp. tooth, an extremely rare and unique chimaeraform from the Carboniferous and Permian shallow seas. This type of tooth is not only remarkable because of its rarity, but also because it fills a niche in the chondricthyan family tree that few other genera fit into. It is a petalodontid...with dentine tubule structures. For those who are familiar with Paleozoic shark teeth, the bradyodonts are known for these features, often appearing on "crusher" teeth as small little dots on the surface of the teeth. The petalodonts on the other hand, are almost exclusively smooth, without exposed dentine tubules. One of the exceptions to this is the Megactenopetalus, which sports a pallet of petalodont-shaped, but bradyodont-textured teeth. Also, this tooth is most likely the earliest occurence of this genera. The majority of the teeth found are from the Permian, with a few exceptions coming from the Pennsylvanian. This tooth was found in a slab of tan mudstone, which eroded from near the top of the Pennington Formation, very near the base of the Pennsylvanian contact of the Raccoon Mountain Formation. It was found near a marine Psephodus sp. tooth, and also a branch of terrestrial Lepidonendron root, indicating to me that this animal likely inhabited a subtidal lagoon setting, which is also further supported by several professional studies that have been performed on the Pennington Formation. Shortly after posting it here on TFF, a member here (Carl) who works at the American Museum of Natural History expressed the museum's interest in acquiring this tooth. I then filled out the paperwork, packed it up carefully, and shipped it to its new home at AMNH! I must say, I was sad to see it leave my collection, but I thing it went to a great home and will be studied sometime in the future. It is now classified as AMNH FF 21096! Some information and photos of the tooth prior to donation. Megactenopetalus sp. crown and root Late Mississippian (Early Carboniferous) Pennington Formation East Tennessee, USA 2016 Roughly 1cm per crown