Dunkleosteus

Dunkleosteus is an extinct genus of large arthrodire ("jointed-neck") fish that existed during the Late Devonian period, about 382–358 million years ago. It was a pelagic fish inhabiting open waters, and one of the first vertebrate apex predators of any ecosystem. Fossils of Dunkleosteus have been found in the United States, Canada, Poland, Belgium, Morocco, and Russia. Dunkleosteus consists of ten species, some of which are among the largest placoderms ("plate-skinned") to have ever lived: D. terrelli, D. belgicus, D. denisoni, D. marsaisi, D. magnificus, D. missouriensis, D. newberryi, D. amblyodoratus, D. raveri, and D. tuderensis. However, the validity of several of these species is unclear. The largest and best known species is D. terrelli, the type species. Since body shape is not known, various methods of estimation put the living total length of the largest known specimen of D. terrelli between 4.1 to 10 m (13 to 33 ft) long and its weight around 1–4 t (1.1–4.4 short tons). However, current evidence suggests length of less than 5 metres (16 ft) was more likely, with the most recent and extensive studies on the body shape and size of D. terrelli producing estimated lengths of approximately 3.4 metres (11 ft) for typical adults and 4.1 metres (13 ft) for exceptionally large individuals of this species. It has been suggested that Dunkleosteus could quickly open and close its jaw, possibly creating suction like modern-day suction feeders, and had an extremely high bite force, but both claims have recently been questioned.