page_title: Helicoprion
section_title: H. davisii
hierarchical_section_title: Helicoprion / Species / H. davisii
caption_attribution_description: Helicoprion ferrieri (Hay, 1907) fossil shark jaw from the Permian of Texas, USA (public display, FMNH PF 7445, Field Museum of Natural History, Chicago, Illinois, USA). This remarkable fossil is a symphyseal tooth whorl from the lower jaw of an edestoid shark. It is in fossiliferous limestone of the Decie Ranch Member of the Skinner Ranch Formation (Wolfcampian Series, lower Lower Permian) from Dugout Mountain, northern Brewster County, Glass Mountains, western Texas, USA. Sharks have a cartilaginous skeleton and mineralized, phosphatic teeth (as are all vertebrate teeth). Helicoprion is undoubtedly the oddest shark in geologic history (see reconstructions elsewhere in this photo album). The specimen shown here is described in Kelly &amp; Zangerl (1976) - Helicoprion (Edestidae) in the Permian of West Texas. Journal of Paleontology 50: 992-994. Classification: Animalia, Chordata, Vertebrata, Chondrichthyes, Elasmobranchii, Eugeneodontida, Edestoidea, Agassizodontidae/Helicoprionidae
context_page_description: Helicoprion is a genus of extinct, shark-like eugeneodontid holocephalid fish. Almost all fossil specimens are of spirally arranged clusters of the individuals' teeth, called "tooth whorls"— the cartilaginous skull, spine, and other structural elements have not been preserved in the fossil record, leaving scientists to make educated guesses as to its anatomy and behavior. Helicoprion lived in the oceans of the early Permian 290 million years ago, with species known from North America, Eastern Europe, Asia, and Australia. The closest living relatives of Helicoprion are the chimaeras.
context_section_description: H. davisii was described initially from a series of 15 teeth found in Western Australia. They were described by H. Woodward in 1886 as a species of Edestus, E. davisii. Upon naming H. bessonowi, Karpinsky also reassigned this species to Helicoprion, an identification subsequently supported by the discovery of two additional and more complete tooth whorls in Western Australia. The species is characterized by a tall and widely spaced tooth whorl, with these becoming more pronounced with age. The teeth also noticeably curve forwards. During the Kungurian and Roadian, this species was very common worldwide.
  H. ferrieri was originally described as a species of the genus Lissoprion in 1907, from fossils found in the Phosphoria Formation of Idaho. An additional specimen, tentatively referred to H. ferrieri, was described in 1955. That specimen was found in Wolfcampian-age quartzites exposed on China Mountain, six miles southeast of Contact, Nevada. The 100-mm-wide fossil consists of one and three-quarters whorls and about 61 preserved teeth. Due to weathering, the rest of the fossil was lost and the preserved section is distorted from slippage of the host rock. While initially differentiated using the metrics of tooth angle and height, Tapanila and Pruitt considered these characteristics to be intraspecifically variable, reassigning H. ferrieri to H. davisii.
  H. jingmenense was described in 2007 from a nearly complete tooth whorl with four and a third volutions (part and counterpart) found in the Lower Permian Qixia Formation of Hubei Province, China. It was discovered during road construction. The specimen is very similar to H. ferrieri and H. bessonowi, though it differs from the former by having teeth with a wider cutting blade, and a shorter compound root, and differs from the latter by having fewer than 39 teeth per volution. Tapanila and Pruitt argued that the specimen was partially obscured by the surrounding matrix, resulting in an underestimation of tooth height. Taking into account intraspecific variation, they synonymized it with H. davisii.
caption: H. davisii (=H. ferrieri) tooth-whorl, Glass Mountains, Texas
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