River shark

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The river sharks are six rare species of shark in the genus Glyphis. The river sharks are members of the family Carcharhinidae, and thus share the basic characteristics of the group.

Contents

1 Characteristics
2 Morphology
3 Species
4 References
5 See also

Characteristics

In general, all river sharks feature the following field characteristics:

a short, broadly rounded snout (its length less than the mouth width);
small, widely spaced nostrils;
small, dark eyes;
broad, serrated upper teeth;
very short labial furrows (lip grooves), restricted to the jaw corners;
a broad dorsal fin with the mid-base closer to the base of the pectoral fins than those of the pelvic fins; and
an anal fin with a deeply excised posterior margin.

Morphology

River sharks are very similar in overall morphology to whaler sharks of the genus Carcharhinus, but can be distinguished from them by the following characteristics:

cusps of lower teeth protrude prominently when mouth is closed;
second dorsal fin is 1/2 to 3/5 the height of the first dorsal fin;
origin of second dorsal fin slightly anterior to origin of anal fin;
precaudal pit is longitudinal rather than crescent-shaped.

Species

Six species of river sharks are known, although due to their secretive habits, other species could easily be lying undiscovered.

Asia

Ganges Shark, Glyphis gangeticus (Müller & Henle, 1839)
: Definitely known from the Hooghly-Ganges river system, West Bengal, India, and likely from the vicinity of Karachi, Pakistan.

Oceania

Speartooth Shark, Glyphis glyphis (Müller & Henle, 1839)
: Uncertain. Speartooth-like sharks occur in Borneo, New Guinea, and Queensland, Australia, but it is uncertain at present if any of these are the true G. glyphis. The holotype has no capture locality listed for it.
Irrawaddy River Shark, Glyphis siamensis (Steindachner, 1896)
: The only known specimen is from the Ayeyarwady River, near Yangon (Rangoon). Until very recently, this species was regarded as an aberrant specimen and possible synonym of (the same species as) the Bull Shark, but shark systematist Leonard J.V. Compagno now considers it a member of the genus Glyphis, distinct from the other known species.
Glyphis species A, not yet described
: Known from two specimens from estuarine waters of the lower reaches of the Bizant River in Queensland, Australia, where it occurs along with the Bull Shark. It is also known from the Alligator River system of the Northern Territory, where it occurs with Glyphis species C. Intriguingly, Glyphis specimens from the Adelaide River, Northern Territory, that have provisionally been identified as this species display very different vertebral counts (148 total vertebrae, versus 217 in specimens from the Bizant River).
Glyphis species B, not yet described
: Known from a single specimen from Borneo. Recently, several small Glyphis have been collected from the Kinabatangan River of Sabah, in northern Borneo. These may be the same species as Glyphis species B. The species is presently in the process of being described by Sarah Fowler and Leonard J.V. Compagno.
Glyphis species C, Not yet described
: Only nine specimens have ever been collected — an immature female taken about 100 km up the Adelaide River in 1989, an adult male taken some 60 km up the South Alligator River in 1996, and in 1999, five females and two males from the East, West and South Alligator Rivers, in brackish water, with salinity ranging from 6 to 26 ppt. This species also occurs alongside Glyphis species A.

References

[Glyphis (TSN 160460)]. Integrated Taxonomic Information System. Accessed on 4 May 2006.

River shark

Characteristics

Morphology

Species

References

See also