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As I was recently doing some research on the prehistoric shark genus Cladodus, I came across some info that classifies the genus as a member of the family Cladoselachidae, Order Cladoselachiformes. https://en.wikipedia.org/wiki/Cladoselachidae This is somewhat confusing to me as mindat and the Paleontological Database aka fossilworks list Cladodus as a member of the family Ctenacanthidae, Order Ctenacanthiformes. https://www.mindat.org/taxon-8657177.html http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=104838 I'm personally leaning more towards Cladodus being a member of at least the Ctenacanthiformes. But I'm curious what are the origins of this taxonomic confusion on the genus Cladodus's phylogenetic placement in the Chondricthyan family? Is Cladodus a member of the Cladoselachiformes or Ctenacanthiformes? What do you guys think?

My son and I are doing our first Shark Adaptation classroom education program in March. We are using fossils from across the timeline of sharks to explain to the students how sharks have managed to stick around this planet for some 430 or so million years. I am very proud of the relatively small fossil shark collection we have. The kids will get to see and in a lot of cases handle some fossils from badass sharks. I thought it would be fun to put some of that collection and bits of the information we present. Eventually I will include the art work my son is producing. He is 5 months away from graduating high school so I limit his time on this art while he works his final art projects for school. The first shark we cover is also one of the most fun for me. The Cladodont sharks are pretty cool and as I recently learned present a perfect opportunity to utilize them in two different spots in our presentation. They start off the program because of Cladoselache. They were not the first shark but they are the basic design for sharks that would be recognizable to 3rd and 4th grade students. They had body type that modern sharks use and they had some fearsome looking teeth. They may be really small teeth but they were deadly if you were a small fish. Science thought these little sharks went extinct during the Great Dying but in 2013 that theory was proven wrong. There were Cladodont teeth found in France that dated to 120 million years ago. They survived the Permian by moving to deeper waters. The small shallow water sharks apparently became very successful as smaller deep water sharks. The physical adaptations are important but the adaptive behavior of sharks is a huge part of how sharks have survived for so long. We only get a few minutes on each shark so that is the basic stuff we will tell the kiddos. Here are the teeth. Pic 1- the unidentified Cladodont tooth. I love this tooth. It is one of my favorites. Under the micro eye, it looks so freaking cool. It could be a Symmorium. It could be something else. It might even be something new. It is from Russia and dated to 320 million years. This will get donated for research at some point. Pic 2- Cladodus belifer. A Mississippian tooth from Biggsville Quarry in Illinois.