--- title: "Frilled Shark (Chlamydoselachus anguineus) | AnimalTracks.wiki" description: "A slow-swimming, six-gilled deep-sea shark whose lineage is estimated at 82 million years old and whose pregnancy may run three and a half years." image: "https://animaltracks.wiki/images/animals/frilled-shark-1.webp" published: "2026-09-06" updated: "2026-09-28" --- # Frilled Shark (*Chlamydoselachus anguineus*) > **Status**: Checked against 9 sources, listed under Sources below. > **Tagline**: A slow-swimming, six-gilled deep-sea shark whose lineage is estimated at 82 million years old and whose pregnancy may run three and a half years. > **Soundtrack Vibe**: Modern Alt-Metal & Post-Hardcore // Bring Me The Horizon, "Drown" > **Soundtrack Links**: [Spotify](https://open.spotify.com/track/6o39Ln9118FKTMbM4BvcEy) | [YouTube](https://www.youtube.com/watch?v=TkV5709EG5M) > **Vibe Match**: The frilled shark is among the slowest of shark species, working the continental slopes usually 120 to 1,500 meters down. Drown moves the same way: a slow, heavy verse that holds back before the chorus breaks. ## Biological Superpowers & Stats - **Taxonomy**: *Chlamydoselachus anguineus* - **Danger Level**: Medium - **Conservation Status**: Least Concern ([IUCN Red List](https://doi.org/10.2305/iucn.uk.2024-1.rlts.t41794a124416882.en)) - **Superpower**: Six frilly gill slits, tricuspid teeth, and a lineage estimated at 82 million years old. - **Habitat**: Continental slopes and outer shelves, usually at 120 to 1,500 meters, across the Atlantic and Pacific Oceans - **Diet**: Mostly squid, plus some fish and even smaller sharks - **Tags**: fish, ocean, deep-sea, carnivore, living-fossil, predator ## Natural History & Behavior ## An Eel Wearing a Shark's Head The **Frilled Shark** (*Chlamydoselachus anguineus*) looks like it was assembled from spare parts: a long, eel-like body, usually chocolate brown, that grows to an average total length of about 150 cm, with the largest on record at 196 cm. Most sharks breathe through five gill slits. This one has six, each edged with a frilly margin of skin, which is how it got its name. The teeth on both jaws each carry three long, sharp points, a shape scientists call tricuspid. It's also in no hurry. The frilled shark is among the slowest of shark species, and usually lives along outer continental shelves and continental slopes. ## Pregnant for Years Frilled sharks give birth to live young rather than laying eggs. Embryos hatch inside the mother's body at just 5.5 cm long, then keep growing on their own yolk supply until they're born at 40 to 60 cm, usually in litters of two to 10. One estimate puts the pregnancy at 3.5 years, which a 2020 study calls the longest gestation known for any vertebrate, though other estimates run as low as one to two years. > **Older Than It Looks Possible** Mitochondrial DNA analysis puts the frilled shark's own lineage at roughly 82 million years old, a figure that broadly matches the fossil record of its wider group, which goes back about 85 million years. ## Rare, Deep, and Split in Two Frilled sharks are rarely seen, with a wide-ranging but patchy distribution in the Atlantic and Pacific Oceans, usually at depths of 120 to 1,500 metres. They have been recorded as bycatch in trawl and bottom longline fisheries throughout their range. Sharks from off southern Angola, Namibia and South Africa, long believed to be the same species, turned out in 2009 to differ on the inside: in the structure of the skull and in their vertebra, spiral valve and fin-cartilage counts. They were named a species of their own, *Chlamydoselachus africana*. ## A Squid Eater With an Empty Stomach Stomach checks on 139 frilled sharks caught in Suruga Bay, Japan, between 1984 and 1988 found squid in most of the stomachs that held any food, and fish in some. Nearly three-quarters of the sharks had empty stomachs, an extremely high rate compared with other deep-water sharks. The 77 females in that sample weighed between 6.2 and 12.1 kg; the 62 males were smaller, between 3.2 and 5.7 kg. Separately, a 1,618 mm frilled shark caught off Choshi, Japan, had eaten a 590 g shark, *Apristurus japonicus*, reported as the first documented case of a frilled shark preying on another shark. ## Frequently Asked Questions ### Why is the frilled shark called a living fossil? A 1976 study of its teeth found their arrangement and shape closely resemble those of Cladoselache, a shark that swam during the Devonian period, and concluded the frilled shark has one of the most primitive types of shark teeth. *(Source: [Goto & Hashimoto 1976]())* ### What have scientists found in the frilled shark's immune system? A 1992 study, which described it as "the most primitive extant shark", found two distinct classes of antibody in its blood serum, a five-unit IgM and a second class built as pairs and single units. The authors called the second class of considerable interest for how the body recognises and removes foreign material. *(Source: [Kobayashi, Tomonaga & Tanaka 1992]())* ### Does anything hunt the frilled shark? Few of its predators are known, though other sharks are thought likely to take it. People sometimes catch it too, by accident, when bottom trawls or nets pull it up. *(Source: [Animal Diversity Web, University of Michigan]())* ## Sources 1. [Chlamydoselachus anguineus (frill shark). Animal Diversity Web, University of Michigan.]() 2. [Finucci & Charles (2024). Chlamydoselachus anguineus. The IUCN Red List of Threatened Species 2024: e.T41794A124416882.]() 3. [López-Romero et al. (2020). Growth trajectories of prenatal embryos of the deep-sea shark Chlamydoselachus anguineus (Chondrichthyes). Journal of Fish Biology.]() 4. [Tanaka et al. (2013). Evolutionary Relations of Hexanchiformes Deep-Sea Sharks Elucidated by Whole Mitochondrial Genome Sequences. BioMed Research International.]() 5. [Indurain et al. (2025). New record of Frilled shark Chlamydoselachus anguineus Garman, 1884 (Chondrichthyes: Hexanchiformes) in the South Pacific Ocean. PeerJ.]() 6. [Kubota, Shiobara & Kubodera (1991). Food habits of the frilled shark Chlamydoselachus anguineus collected from Suruga Bay, central Japan. Nippon Suisan Gakkaishi.]() 7. [Ebert & Compagno (2009). Chlamydoselachus africana, a new species of frilled shark from southern Africa (Chondrichthyes, Hexanchiformes, Chlamydoselachidae). Zootaxa.]() 8. [Kobayashi, Tomonaga & Tanaka (1992). Identification of a second immunoglobulin in the most primitive shark, the frill shark, Chlamydoselachus anguineus. Developmental & Comparative Immunology.]() 9. [Goto & Hashimoto (1976). Studies on the teeth of Chlamydoselachus anguineus, a living archaic fish. Japanese Journal of Oral Biology.]() *Published September 6, 2026. 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