Southern African frilled shark
Encyclopedia
The southern African frilled shark (Chlamydoselachus africana) is a species
of shark
in the family
Chlamydoselachidae, described in 2009. It is found in deep water from off southern Angola
to southern Namibia
. This species is difficult to distinguish from the better-known frilled shark (C. anguineus), but is smaller at maturity and differs in several proportional measurements including head length and mouth width. It seems to be a specialized predator of smaller sharks, using its flexible jaws and numerous needle-like, recurved teeth to capture and swallow them whole. Reproduction is presumably ovoviviparous as with the other member of its family.
, Namibia
in February 1988, by the South African research ship FRS Africana (after which this species would eventually be named). The specimen was an adult male smaller than other known mature C. anguineus, and subsequent investigations revealed other consistent differences between frilled sharks in this region and C. anguineus. The new species was termed Chlamydoselachus "sp. A", before being formally described in 2009 by David Ebert and Leonard Compagno
, in a paper for the scientific journal
Zootaxa. The holotype
was a 117 cm (46.1 in) long immature female caught at a depth of 409 m (1,341.9 ft) off the Cunene River
, Namibia, by the research vessel Benguela.
to southern Namibia. Frilled sharks have also been captured off South Africa
, at 1230–1400 m (4,035.4–4,593.2 ft) deep off Eastern Cape Province, and at 300 m (984.3 ft) deep off KwaZulu-Natal Province; it is uncertain whether these specimens are C. africana. Little is known of its habitat preferences; one known specimen was caught 425 m (1,394.4 ft) down in a zone of low dissolved oxygen and high nutrient
s, over a soft substrate.
-like body and a broad, flattened head. The eyes are large and rounded. The sizable mouth is placed terminally on the blunt snout, containing around 30 tooth rows in the upper jaw and 27 tooth rows in the lower jaw. Each tooth has three slender, smooth, recurved cusps, with tiny cusplets between them, and a base that interlocks with the tooth behind it. There are six pairs of long gill slit
s, with the first pair meeting over the throat. The pectoral fins are broad and rounded, originating just behind the sixth gill slit. The pelvic and anal fins are large with long bases and curved margins. The single dorsal fin
is set far back on the body over the anal fin, and has a short base. The caudal fin is low and somewhat triangular, without a lower lobe.
Compared to the frilled shark, the southern African frilled shark has several proportional differences, including a longer head and gill slits, more widely spaced eyes and nares, broader mouth, and a greater distance between the head and the pectoral fins. The largest known female is the immature 117 cm (46.1 in) long holotype, and the largest known males measure 99 cm (39 in) long. In life the shark is dark gray, but covered with a thin membrane that gives it a uniform dark brown color.
contents, the southern African frilled shark seems to feed mainly on smaller sharks such as the African sawtail catshark
(Galeus polli). Its jaws, buccal cavity, and abdomen are all highly distensible, suggesting that this shark is specialized for capturing and swallowing whole large prey, with its rows of needle-like, recurved teeth preventing escape. One 92 cm (36.2 in) long specimen was found to have swallowed a ghost catshark
(Apristurus sp.) that measured 40% of its body length. Although adult females are unknown, the southern African frilled shark is presumed to be aplacental viviparous like the frilled shark. Males mature sexually at a length of 91.5 cm (36 in).
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Chlamydoselachidae, described in 2009. It is found in deep water from off southern Angola
Angola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
to southern Namibia
Namibia
Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
. This species is difficult to distinguish from the better-known frilled shark (C. anguineus), but is smaller at maturity and differs in several proportional measurements including head length and mouth width. It seems to be a specialized predator of smaller sharks, using its flexible jaws and numerous needle-like, recurved teeth to capture and swallow them whole. Reproduction is presumably ovoviviparous as with the other member of its family.
Taxonomy
The frilled shark (C. anguineus) was long thought to be the only extant member of its genus and family. The existence of a second Chlamydoselachus species off southern Africa was first suspected from a specimen caught off LüderitzLüderitz
Lüderitz is a harbour town in south-west Namibia, lying on one of the least hospitable coasts in Africa. It is a port developed around Robert Harbour and Shark Island.- Overview :...
, Namibia
Namibia
Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
in February 1988, by the South African research ship FRS Africana (after which this species would eventually be named). The specimen was an adult male smaller than other known mature C. anguineus, and subsequent investigations revealed other consistent differences between frilled sharks in this region and C. anguineus. The new species was termed Chlamydoselachus "sp. A", before being formally described in 2009 by David Ebert and Leonard Compagno
Leonard Compagno
Leonard Joseph Victor Compagno is an international authority on shark taxonomy and the author of many scientific papers and books on the subject, best known of which is his 1984 catalogue of shark species produced for the Food and Agriculture Organization of the United Nations.-Career:*Ph.D,...
, in a paper for the scientific journal
Scientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
Zootaxa. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
was a 117 cm (46.1 in) long immature female caught at a depth of 409 m (1,341.9 ft) off the Cunene River
Cunene River
The Cunene River or Kunene River is a river in Southern Africa. It flows from the Angola highlands south to the border with Namibia. It then flows west along the border until it reaches the Atlantic Ocean. It is one of the few perennial rivers in the region. It is about long, with a drainage...
, Namibia, by the research vessel Benguela.
Distribution and habitat
The southern African frilled shark has only been confirmed to occur from off southern AngolaAngola
Angola, officially the Republic of Angola , is a country in south-central Africa bordered by Namibia on the south, the Democratic Republic of the Congo on the north, and Zambia on the east; its west coast is on the Atlantic Ocean with Luanda as its capital city...
to southern Namibia. Frilled sharks have also been captured off South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, at 1230–1400 m (4,035.4–4,593.2 ft) deep off Eastern Cape Province, and at 300 m (984.3 ft) deep off KwaZulu-Natal Province; it is uncertain whether these specimens are C. africana. Little is known of its habitat preferences; one known specimen was caught 425 m (1,394.4 ft) down in a zone of low dissolved oxygen and high nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s, over a soft substrate.
Description
The southern African frilled shark looks very similar to the frilled shark, with a long snakeSnake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
-like body and a broad, flattened head. The eyes are large and rounded. The sizable mouth is placed terminally on the blunt snout, containing around 30 tooth rows in the upper jaw and 27 tooth rows in the lower jaw. Each tooth has three slender, smooth, recurved cusps, with tiny cusplets between them, and a base that interlocks with the tooth behind it. There are six pairs of long gill slit
Gill slit
Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of Cartilaginous fish such as sharks, rays, sawfish, and guitarfish. Most of these have five pairs, but a few species have 6 or 7 pairs...
s, with the first pair meeting over the throat. The pectoral fins are broad and rounded, originating just behind the sixth gill slit. The pelvic and anal fins are large with long bases and curved margins. The single dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
is set far back on the body over the anal fin, and has a short base. The caudal fin is low and somewhat triangular, without a lower lobe.
Compared to the frilled shark, the southern African frilled shark has several proportional differences, including a longer head and gill slits, more widely spaced eyes and nares, broader mouth, and a greater distance between the head and the pectoral fins. The largest known female is the immature 117 cm (46.1 in) long holotype, and the largest known males measure 99 cm (39 in) long. In life the shark is dark gray, but covered with a thin membrane that gives it a uniform dark brown color.
Biology and ecology
From stomachStomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
contents, the southern African frilled shark seems to feed mainly on smaller sharks such as the African sawtail catshark
African sawtail catshark
The African sawtail catshark is a species of catshark, family Scyliorhinidae. Demersal in nature, it is found at depths of off the western African coast from Morocco to South Africa...
(Galeus polli). Its jaws, buccal cavity, and abdomen are all highly distensible, suggesting that this shark is specialized for capturing and swallowing whole large prey, with its rows of needle-like, recurved teeth preventing escape. One 92 cm (36.2 in) long specimen was found to have swallowed a ghost catshark
Apristurus
Apristurus is a genus of catshark, the family Scyliorhinidae, commonly known as the ghost or demon catsharks.-Species:* Apristurus albisoma Nakaya & Séret, 1999* Apristurus ampliceps Sasahara, Sato & Nakaya, 2008...
(Apristurus sp.) that measured 40% of its body length. Although adult females are unknown, the southern African frilled shark is presumed to be aplacental viviparous like the frilled shark. Males mature sexually at a length of 91.5 cm (36 in).