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Our last post left off just before the Permian so this is where the students will learn about the series extinction events known as The Great Dying. One of the really interesting points in shark evolution is the survival of sharks during this period. They survived by adapting to a vastly different climate and a much different aquatic world. This is when the Hydobonts really emerge and the age of the modern shark starts. The first species we cover are the xenacanthids. We originally placed the Eel Sharks in the Golden Age of Sharks section but I wanted to illustrate that some that while a few xenacanthid sharks survived the Permian extinction, they died off shortly after. They were apex predators in freshwater ecosystems until 266 mya. The adaptations we hit on are the forked teeth and eel like body. Despite being an apex predator and some initially surviving the Permian, they were unable to survive long term either due to being unable to adapt to long term changes in the aquatic environments they formally dominated or were out competed by animals better adapted or both. The Hybodonts first start appearing in the fossil record in the Carboniferous era and much of the diversity of the family was lost during Permian but Hybodonts would became the dominant shark of the Triassic and lasted until the Miocene. They were varied in form, size, and habitat. Hybodont sharks lived in freshwater environments and marine environments. They are known from fossil formations that are shallow and deep. They evolved to fill a variety of ecological niches. They had different kinds of teeth for different kinds of prey. We specifically touch on Hybodus obtusus, Lissodes minimus, and the tiny, fairly recently described Reticulodus synergus as those are the species we have. My son's early sketch of Reticulodus is super cool. Given that this is smallest shark we are discussing, the art work is the hook more than the micro fossil. This is the one spot in the shark program that is a little visually underwhelming from a fossil standpoint. We have only a few small items so it lacks the visual appeal of the weirdness of earlier sharks and the WOW effect of the giant sharks that follow. This is a very fixable issue for us. I found a source for Orthacanthus teeth and we are planning on picking up a nice dentition set to go with our partial spine. Carter drew his Orthacanthus in a position that will match the dentition and spine when we have the teeth. A weakness now will be a visual strength in a month or two. I would really love to pick up an Anstercanthus tooth and spine too. They seem to be out there on the market from time to time. We plan on grabbing a few more Lissodes teeth and Reticulodus teeth too. A number of small teeth can make a nice display. Here are the fossils we currently have for the presentation Pic 1 Orthacanthus texanus tooth and partial spine of an unidentified Orthacanthus. Both are from Oklahoma I believe. Pic 2 Hybodus obtusus tooth. A small tooth and one that needs some additional material. Pic 3 A picture of all the fossils for the presentation including Lissodes minimus and Reticulodus synergus. Yup the dots are cool shark teeth lol I actually love the tiny sharks and this will be one of my favorite spots in the presentation because we deliver these right before we get into the giant animals that follow.