page_title: Ohmdenia
section_title: Description
hierarchical_section_title: Ohmdenia / Description
caption_attribution_description: English: an assortment of the different forms present in Pachycormid fish, each scaled from specimens (noted in picture + colour coded)
context_page_description: Ohmdenia is an extinct genus of prehistoric bony fish that lived from the Toarcian stage of the Early Jurassic epoch.Ohmdenia was first described in 1953 by B. Hauff, based on a fossil found in the well-known Posidonia Shale in Holzmaden, Germany. For a long time this animal has been considered a close relative of Birgeria, a great predator typical of the Triassic period with an uncertain systematic position. Further studies have shown similarities with the pachicormiforms, a group of neopolitics considered close to the origin of teleosts and also including giant forms and planctives. Some studies have erroneously indicated Ohmdenia as a synonym of Saurostomus, other studies have instead placed Ohmdenia as an important evolutionary passage between the basal pachicormiforms and the more derived planktivore pachicormiformes.
context_section_description: This animal is known exclusively for an incomplete fossil, but sufficient to reconstruct (at least partially) its appearance. Ohmdenia must have been a large fish, at least two and a half meters long. Ohmdenia was therefore one of the largest bony fishes of the lower Jurassic, surpassed only by the great chondrostei such as Strongylosteus and Gyrosteus . The body had to be relatively slender, with a symmetrical and slender tail. The skull was long and short, and had a jaw equipped with numerous teethsmall, rather robust, rear-facing and placed in an area that extended along the dorsal margin of the jaw. The combination of a long and slender body and a low and elongated skull is unique among the fish related to Ohmdenia (the pachicormiforms).
caption: Size comparation with relatives (blue)
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