page_title: Frilled shark
section_title: Taxonomy and phylogeny
hierarchical_section_title: Frilled shark / Taxonomy and phylogeny
caption_attribution_description: English: Illustration of a frilled shark (Chlamydoselachus anguineus) that accompanied the species description.
context_page_description: The frilled shark and the southern African frilled shark are the two extant species of shark in the family Chlamydoselachidae. The frilled shark is considered a living fossil, because of its primitive, anguilliform physical traits, such as a dark-brown color, amphistyly, and a 2.0 m –long body, which has dorsal, pelvic, and anal fins located towards the tail. The common name, frilled shark, derives from the fringed appearance of the six pairs of gill slits at the shark's throat.
  The two species of frilled shark are distributed throughout regions of the Atlantic and the Pacific oceans, usually in the waters of the outer continental shelf and of the upper continental slope, where the shivers usually live near the ocean floor, near biologically productive areas of the ecosystem. To live on a diet of cephalopods, smaller sharks, and bony fish, the frilled shark practices diel vertical migration to feed at night at the surface of the ocean. When hunting food, the frilled shark moves like an eel, bending and lunging to capture and swallow whole prey with its long and flexible jaws, which are equipped with 300 recurved, needle-like teeth.
context_section_description: The zoologist Ludwig Döderlein first identified, described, and classified the frilled shark as a discrete species of shark. After three years (1879–1881) of marine research in Japan, Döderlein took two specimen sharks to Vienna, but lost the taxonomic manuscript of the research. Three years later, in the Bulletin of the Essex Institute (vol. XVI, 1884) the zoologist Samuel Garman published the first taxonomy of the frilled shark, based upon his observations, measurements, and descriptions of a 1.5-metre (4 ft 11 in)–long female shark from Sagami Bay, Japan. In the article “An Extraordinary Shark” Garman classified the new species of shark within its own genus and family, and named it Chlamydoselachus anguineus (eel-like shark with frills). The Graeco–Latin nomenclature of the frilled shark derives from the Greek chlamy (frill) and selachus (shark), and the Latin anguineus (like an eel); besides its common name, the frilled shark also is known as the "lizard shark" and as the "scaffold shark".
  Initially, marine scientists considered the frilled shark a living, evolutionary representative of the extinct elasmobranchii subclass of cartilaginous fish (rays, sharks, skates, sawfish); because the shark's body featured primitive anatomic traits, such as long jaws with trident-shaped, multi-cusp teeth; amphistyly, the direct articulation of the jaws to the cranium, at a point behind the eyes; and a quasi-cartilaginous notochord (a proto-spinal-column) composed of indistinct vertebrae. From that anatomy, Garman proposed that the frilled shark was related to the cladodont sharks of the Cladoselache genus that existed during the Devonian period (419–359 mya) in the Palaeozoic era (541–251 mya). In contrast to Garman's thesis, the ichthyologist Theodore Gill and the paleontologist Edward Drinker Cope, suggested that the frilled shark's evolutionary tree indicated relation to the Hybodontiformes (hybodonts), which were the dominant species of shark during the Mesozoic era (252–66 mya); and Cope categorized the Chlamydoselachus anguineus species to the fossil genus Xenacanthus that existed from the late Devonian period to the end of the Triassic period of the Mesozoic era.
  The anatomic traits of body, muscle, and skeleton phylogenically include the frilled shark to the neoselachian clade (modern sharks and rays) which relates it to the cow shark, in the order Hexanchiformes; nonetheless, as a systematist of biology, the ichthyologist Shigeru Shirai proposed the Chlamydoselachiformes taxonomic order exclusively for the C. anguinesis and the C. africana species of frilled sharks. As a marine animal, the frilled shark is a living fossil because of its relatively unchaged anatomy and physique, since first appearing in the primeval seas of the Late Cretaceous (ca. 95 mya) and the Late Jurassic (150 mya) epochs. In evolutionary terms, the frilled shark is an animal species of recent occurrence in the natural history of the Earth; the earliest discoveries of the fossilized teeth of the Chlamydoselachus anguineus species of shark date to the early Pleistocene epoch (2.58–11.70 mya). In 2009, marine biologists identified, described, and classified the Chlamydoselachus africana (southern African frilled shark) of the Atlantic waters of southern Angola and of southern Namibia as a species of frilled shark different from the Chlamydoselachus anguineus identified in 1884.
caption: In the article "An Extraordinary Shark", the zoologist Samuel Garman depicts a frilled shark (Clamydoselachus anguineus); the superior inset depicts dorsal and ventral views of the shark's head; the inferior inset depicts two, trident-shaped teeth. (Bulletin of the Essex Institute, vol. XVI, 1884)
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