page_title: Orthacanthus
section_title: Paleoecology
hierarchical_section_title: Orthacanthus / Paleoecology
caption_attribution_description: Italiano: Fossil of Orthacanthus, an extinct fish--
context_page_description: Orthacanthus is an extinct genus of fresh-water xenacanthid sharks, named by Louis Agassiz in 1836, ranging from the Upper Carboniferous until the Lower Permian. Orthacanthus lived in marine environments and had a nektobenthic life habitat, with a carnivorous diet. Multiple sources have also discovered evidence of cannibalism in the diet of Orthacanthus and of "filial cannibalism" where adult Orthacanthus preyed upon juvenile Orthacanthus. The genus Orthacanthus has been synonymized with Dittodus, Didymodus, and Diplodus.
  About 260 million years ago, Orthacanthus was the apex predator of freshwater swamps and bayous in Europe and North America. Mature Orthacanthus reached nearly 3 meters in length. Orthacanthus teeth have a minimum of three cusps, two principal cusps, and an intermediate cusp, where the principal cusps are variously serrated, with complex base morphology. Additionally, Orthacanthus can be diagnosed by major transverse axes of proximal ends at a 45 degree angle to and often almost parallel to the labial margin of the base between the cusps. Deformed teeth are characteristic of the xenacanth sharks and of Orthacanthus.
context_section_description: The palaeobiogeographical distribution of O. platypternus suggests ontogenetic habitat partitioning. Ontogenetic niche theory predicts that individuals may change their habitat or diet to maintain optimal growth rates or to improve trade-offs between mortality risk and growth. While smaller individuals likely lived in shallower waters such as in small ponds and stream channels of the coastal plain, larger individuals likely lived in deeper water such as the fluvio-lacustrine (rivers and lakes) and marginal marine areas. 
  The oldest known specimen of Orthacanthus, Diplodus problematicus was found in New Brunswick, Canada, from the Emsian, ranging between 407 and 393 million years ago. Other specimens have been found in locations including the US, the United Kingdom, Poland, and France.
caption: O. senckenbergianus
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