River shark

The river shark is one of 6 rare species of the genus Glyphis.

The river sharks are members of the family Carcharhinidae, and thus share the basic characteristics of the group.

Table of contents

1 Features of Glyphis spp. 1.1 General characteristics 1.2 Morphology 2 Species 2.3 Asia 2.3.1 Ganges Shark 2.4 Oceania 2.4.2 Speartooth Shark 2.4.3 Irrawaddy River Shark 2.4.4 Glyphis species A 2.4.5 Glyphis species B 2.4.6 Glyphis species C

Features of Glyphis spp.

General characteristics

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

• a short, broadly rounded snout (its length less than the mouth width)

• small, wide-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 Irrawaddy River, near 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 100km up the Adelaide River in 1989, an adult male taken some 60km 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.