Hybodus
Hybodus (from , 'crooked' and 'tooth') is an extinct genus of shark that, in a strict sense, only lived during the Early Jurassic epoch. It is a wastebasket taxon that is 'broadly polyphyletic' and requires reexamination. The first fossilized teeth from Hybodus were found in England around 1845; since then teeth (and dorsal spines) have been recovered from Europe. During the Triassic, Jurassic, and Cretaceous periods, the hybodonts were especially successful and could be found in shallow seas around the world. For reasons that are not fully understood, the hybodonts became extinct near the end of the Late Cretaceous period . Description. "Hybodus" species grew to about in length, and are believed to have been opportunist predators. It was not very big, but had the classic streamlined shark shape, complete with two dorsal fins that would have helped it steer with precision. The mouth was not large, and rather than ruthlessly hunt large prey, "Hybodus", was capable of eating a wide range of foods. They had several distinct features that made them stand apart from other primitive sharks. Firstly, they had two different types of teeth, suggesting a wide diet. The sharper teeth would have been used to catch slippery prey , while the flatter teeth probably helped them crush shelled creatures. Secondly, they had a bony blade on their dorsal fin that probably served a defensive function. The males also possessed claspers, specialized organs that directly insert sperm into the female, and which are still present in modern sharks. Species Status. Several "Hybodus" species, including "H. butleri", "H. rajkovichi", and "H. montanensis", were later reassigned to "Meristodonoides". "H. basanus" and "H. fraasi" is now included in the genus "Egertonodus". "H. obtusus" represents a junior synonym of "Asteracanthus ornatissimus". A new species from Spain, "H. bugarensis", is described in 2013. Two new  species from China, "H. xinzhuangensis" and "H. chuanjieensis" are named in 2018, and "H. houtienensis" is considered, while other species from China and Thailand are no longer part of the genus and requires reassessment. However, "Hybodus" sensu stricto only refers to the type species "H. reticulatus" and the other species "H. hauffianus". The problem is that even those two species require reassessment. Media depictions. "Hybodus" was depicted in the third episode of the 1999 BBC television series Walking with Dinosaurs and within the 2003 BBC series  (Chased by Sea Monsters in the United States).