Catalog Number: CG-0015
Finding a possible Petalodus tooth is one of the gateway fossils that lead to my love of fossil hunting. My first find was a bust, but finally I have found the real thing. This piece came from the huge shelf rocks that outcropped inches from the creek bed locally. We busted up the rock, and set pieces aside as we found them. I thought this was a winged brachiopod at first glance.
Petalodus is part of the Chondrichthyes class of cartilaginous fishes. The skeleton was made of cartridge, much like modern sharks and were not often preserved as fossils. The teeth were much harder and survive more readily as fossils. Out of the fossils I have found locally, this one is more rare. According to Wikipedia, the genus appears late in the Carboniferous and existed until the end of the Permian.
Update: Since finding this first tooth, I’ve found over a dozen more. I wrote a research article digging into the original holotype specimens of Petalodus.
Measurements and Remarks
The lateral portion of the tooth measures 23mm across the crown of the specimen. The horizontal portion of the crown is 6mm at its widest point in the middle giving a 23:6 ratio for it’s squashed diamond shape. The separating ridge between the crown and the root is approximately 2mm in width at the center. The root is 6mm long at its longest point throughout the center.
The right side of the exposed specimen shows 9mm of serration exposed fully. Apparent serration is shown continuing 3mm further until the apex of the serrated edge and another 3mm after the apex transition. After that, while it’s assumed a full serrated edge is available, the striation marks are fully covered 3mm past the apex until the left edge of the crown.
Further Reading About Petalodus
- Oceans of Kansas – Xystracanthus, Cladodus and Petalodus from the Carboniferous of Kansas. – J. Leidy
- Utah Geological Association – Taxonomic validity of Petalodus ohioensis (Chondrichthyes, Petalodontidae) based on a cast of the lost holotype – K. Carpenter, W. Itano
- Pennsylvania Geology Newsletter – Vol 48, No 2. Page 3-11, Summer 2018 – Reflections on Petalodus, a Common Late Paleozoic “Shark” Tooth Found in Western Pennsylvania’s Rocks – J. Harper
- British Geological Society – Fossil specimen : SM E 4291 – Holotype