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title: "What the sources say about the Frilled Shark | AnimalTracks.wiki"
description: "51 claims from the Frilled Shark profile, each beside the words of the source that backs it."
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# What the sources say about the Frilled Shark (*Chlamydoselachus anguineus*)

> 51 claims from the Frilled Shark profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Frilled Shark](https://animaltracks.wiki/animals/frilled-shark/)

## Chlamydoselachus anguineus (frill shark). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Chlamydoselachus_anguineus/

| The page says | The source says |
| :--- | :--- |
| A slow-swimming | They are among the slowest of shark species (Parker & Parker, 1999). |
| six-gilled deep-sea shark | has six gill openings (most sharks have five) |
| usually chocolate brown | The body tends to be a chocolate brown color. |
| Most sharks breathe through five gill slits. This one has six | Chlamydoselachus anguineus has six gill openings (most sharks have five) |
| This one has six, each edged with a frilly margin of skin, which is how it got its name. | Chlamydoselachus anguineus has six gill openings (most sharks have five). The first gill is continuous across the throat, while all the gills are surrounded by frilly margins of skin-hence the name "frilled shark." (note: "which is how it got its name" paraphrases "hence the name") |
| The teeth on both jaws each carry three long, sharp points | The teeth are alike both on the upper and lower jaws, with three elongate, sharp cusps separated by two intermediate ones |
| The frilled shark is among the slowest of shark species | Chlamydoselachus anguineus is a slow-moving, deep water shark. They are among the slowest of shark species (Parker & Parker, 1999). |
| Few of its predators are known, though other sharks are thought likely to take it. | There are few known predators of frilled sharks. Other sharks are likely predators |
| People sometimes catch it too, by accident, when bottom trawls or nets pull it up. | humans may take these sharks incidentally as fishing bycatch. Becauses they occupy the benthos, they are sometimes caught during bottom trawling or in nets when they venture near the surface |
| dangerLevel: Medium | These are not dangerous sharks, but their teeth have lacerated the hands of the unwary scientist and or fisherman examining or holding them. |

## Finucci & Charles (2024). Chlamydoselachus anguineus. The IUCN Red List of Threatened Species 2024: e.T41794A124416882.

https://doi.org/10.2305/iucn.uk.2024-1.rlts.t41794a124416882.en

| The page says | The source says |
| :--- | :--- |
| Least Concern | IUCN Red List category: Least Concern (LC). Chlamydoselachus anguineus Garman, 1884, IUCN taxon 41794. (note: category read through GBIF's copy of the Red List, as the source pack instructs; the DOI is the assessment page itself) |

## López-Romero et al. (2020). Growth trajectories of prenatal embryos of the deep-sea shark Chlamydoselachus anguineus (Chondrichthyes). Journal of Fish Biology.

https://doi.org/10.1111/jfb.14352

| The page says | The source says |
| :--- | :--- |
| whose pregnancy may run three and a half years | The gestation period of C. anguineus is the longest period known for all vertebrates, lasting 3.5 years |
| and even smaller sharks | It is considered a benthopelagic shark feeding on cephalopods, bony fish and even smaller sharks |
| a long, eel-like body | It has an elongated, eel‐like body |
| grows to an average total length of about 150 cm | it grows up to an average total length (TL) of 150 cm |
| with the largest on record at 196 cm | with a maximum reported TL of 196 cm (Gudger & Smith, 1933) |
| Pregnant for Years | although the gestation period estimation can be as low as 1–2 years (Compagno, 1984; Gudger & Smith, 1933) (note: heading; every estimate, low (1-2 years) or high (3.5 years), is at least a year) |
| give birth to live young rather than laying eggs | Frilled sharks are aplacental viviparous with a year‐round mating and breeding season. (note: viviparous means live-bearing; "rather than laying eggs" is the definition) |
| Embryos hatch inside the mother's body at just 5.5 cm long | They hatch within the mother's uterus when they reach a TL of 5.5 cm |
| keep growing on their own yolk supply until they're born at 40 to 60 cm | remain there, feeding on their yolk sack until they are born at a TL of 40–60 cm |
| usually in litters of two to 10 | Usually there are two to 10 embryos in each litter. |
| One estimate puts the pregnancy at 3.5 years, which a 2020 study calls the longest gestation known for any vertebrate | The gestation period of C. anguineus is the longest period known for all vertebrates, lasting 3.5 years (note: the 3.5-year figure is Tanaka et al. 1990, reported by this 2020 paper; 2020 is the reference's own year) |
| other estimates run as low as one to two years | although the gestation period estimation can be as low as 1–2 years (Compagno, 1984; Gudger & Smith, 1933) |
| turned out in 2009 | Ebert and Compagno ( 2009 ) identified the populations around South Africa as separate species, Chlamydoselachus africana |

## Tanaka et al. (2013). Evolutionary Relations of Hexanchiformes Deep-Sea Sharks Elucidated by Whole Mitochondrial Genome Sequences. BioMed Research International.

https://doi.org/10.1155/2013/147064

| The page says | The source says |
| :--- | :--- |
| whose lineage is estimated at 82 million years old | the divergence time of C. anguineus is estimated as 82.0 Mya (78.1 Mya~87.9 Mya) |
| Six frilly gill slits, tricuspid teeth, and a lineage estimated at 82 million years old. | the divergence time of C. anguineus is estimated as 82.0 Mya (78.1 Mya~87.9 Mya) (note: combined stats line; the gill/teeth parts reuse the adw-frilled-shark and record-2025 claims below) |
| Mitochondrial DNA analysis puts the frilled shark's own lineage at roughly 82 million years old | the divergence time of C. anguineus is estimated as 82.0 Mya (78.1 Mya~87.9 Mya) (note: the paper's method is full mitochondrial-genome sequencing) |
| broadly matches the fossil record of its wider group, which goes back about 85 million years | This estimation is largely consistent with the known fossil record of Chlamydoselachiformes (85 Mya) |

## Indurain et al. (2025). New record of Frilled shark Chlamydoselachus anguineus Garman, 1884 (Chondrichthyes: Hexanchiformes) in the South Pacific Ocean. PeerJ.

https://doi.org/10.7717/peerj.18992

| The page says | The source says |
| :--- | :--- |
| Continental slopes and outer shelves, usually at 120 to 1,500 meters, across the Atlantic and Pacific Oceans | This species usually inhabits outer continental and insular shelves and continental slopes at depths of 120–1,500 m |
| a shape scientists call tricuspid | the presence of tricuspid teeth |
| usually lives along outer continental shelves and continental slopes | This species usually inhabits outer continental and insular shelves and continental slopes |
| Frilled sharks are rarely seen | Although rarely observed, frilled sharks have been documented as bycatch in trawl and bottom longline fisheries throughout its range |
| with a wide-ranging but patchy distribution in the Atlantic and Pacific Oceans | C. anguineus has a wide-ranging but sporadic distribution in the Atlantic and Pacific Oceans |
| usually at depths of 120 to 1,500 metres | This species usually inhabits outer continental and insular shelves and continental slopes at depths of 120–1,500 m |
| They have been recorded as bycatch in trawl and bottom longline fisheries throughout their range. | frilled sharks have been documented as bycatch in trawl and bottom longline fisheries throughout its range |
| working the continental slopes usually 120 to 1,500 meters down | This species usually inhabits outer continental and insular shelves and continental slopes at depths of 120–1,500 m |

## Kubota, Shiobara & Kubodera (1991). Food habits of the frilled shark Chlamydoselachus anguineus collected from Suruga Bay, central Japan. Nippon Suisan Gakkaishi.

https://doi.org/10.2331/suisan.57.15

| The page says | The source says |
| :--- | :--- |
| Mostly squid, plus some fish | The food items of this shark were mostly decapodan cephalopods and fishes, which were found at the frequencies of 60.5% and 10.5%, respectively among the stomachs containing food. (note: the cephalopods identified by beak were squid (Todarodes pacificus, Sthenoteuthis oualaniensis, Gonatus sp.)) |
| Stomach checks on 139 frilled sharks caught in Suruga Bay, Japan, between 1984 and 1988 | a stomach content analysis of frilled shark Chlamydoselachus anguineus is presented based on 139 specimens caught incidentally by sergestid shrimp midwater trawling or bottom gill-net fishing conducted in Suruga Bay from 1984 to 1988 |
| found squid in most of the stomachs that held any food, and fish in some | The food items of this shark were mostly decapodan cephalopods and fishes, which were found at the frequencies of 60.5% and 10.5%, respectively among the stomachs containing food. |
| Nearly three-quarters of the sharks had empty stomachs | the empty stomach rate of frilled shark stood as high as 73.4% throughout almost the year |
| an extremely high rate compared with other deep-water sharks | The empty stomach rate of specimens examined was 73.4% showing an extremely high level as 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 | 77 females with a total body length ranging from 1,376 to 1,768mm and weighing between 6,230 and 12,120g, and 62 males with total body length ranging from 1,178 to 1,486mm and weighing between 3,234 and 5,740 g (note: kg figures are grams converted and rounded to one decimal) |
| 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 | Taniuchi8) reported that a frilled shark measuring 1,618mm in total length, from Choshi in Japanese coastal waters, preyed on an Apristurus japonicus of 590g, as the first documented case of predation on another shark by a frilled shark. |

## Ebert & Compagno (2009). Chlamydoselachus africana, a new species of frilled shark from southern Africa (Chondrichthyes, Hexanchiformes, Chlamydoselachidae). Zootaxa.

https://doi.org/10.11646/zootaxa.2173.1.1

| The page says | The source says |
| :--- | :--- |
| Rare, Deep, and Split in Two | is now known to contain at least two species (note: heading; "two" refers to the anguineus/africana split covered below it; "Rare" is the record-2025 "rarely observed" claim) |
| Sharks from off southern Angola, Namibia and South Africa, long believed to be the same species | long believed to be a monotypic family and genus, consisting of a single wide ranging species, Chlamydoselachus anguineus (Garman, 1884), is now known to contain at least two 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 | The new species, although difficult to distinguish externally from the well known C. anguineus, differ internally by the structural differences in the chondrocranium, lower total vertebral and spiral valve counts, and pectoral-fin radial counts. The new species, Chlamydoselachus africana, is known from off southern Angola, Namibia, and South Africa. (note: 2009 is the reference's own publication year; chondrocranium is the cartilage skull, pectoral-fin radials the fin cartilages) |

## Kobayashi, Tomonaga & Tanaka (1992). Identification of a second immunoglobulin in the most primitive shark, the frill shark, Chlamydoselachus anguineus. Developmental & Comparative Immunology.

https://doi.org/10.1016/0145-305x(92)90004-v

| The page says | The source says |
| :--- | :--- |
| A 1992 study, which described it as "the most primitive extant shark" | isolated from serum of the frill shark, Chlamydoselachus anguineus, the most primitive extant shark (note: 1992 is the reference's own publication year; the ranking is kept as that paper's description) |
| found two distinct classes of antibody in its blood serum, a five-unit IgM and a second class built as pairs and single units | We thus concluded that the frill shark has two distinct classes of immunoglobulins: one a pentameric IgM and the other a second class of immunoglobulin with dimeric and monomeric structure. |
| The authors called the second class of considerable interest for how the body recognises and removes foreign material. | The presence of the second Ig is of considerable interest with respect to antigen recognition and exclusion. |

## Goto & Hashimoto (1976). Studies on the teeth of Chlamydoselachus anguineus, a living archaic fish. Japanese Journal of Oral Biology.

https://doi.org/10.2330/joralbiosci1965.18.362

| The page says | The source says |
| :--- | :--- |
| A 1976 study of its teeth found their arrangement and shape closely resemble those of Cladoselache, a shark that swam during the Devonian period | In the arrangement pattern and morphology of the teeth, Chlamydoselachus is very similar toCladoselache, a Devonian shark. (note: 1976 is the reference's own publication year; quote keeps the cached text's missing space) |
| concluded the frilled shark has one of the most primitive types of shark teeth | Therefore, it is considered that Chlamydoselachus has one of themost primitive shark teeth type. (note: quote keeps the cached text's missing space) |