River shark
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The river sharks are six (three to be formally described) rare species of shark in the genus Glyphis, although, due to their secretive habits, other species could easily remain undiscovered. The river sharks are members of the family Carcharhinidae, and thus share the basic characteristics of the group. Note: the bull shark is sometimes called both the river shark and the Ganges shark; it should not be confused with the true river sharks of Glyphis.
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[edit] 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.
[edit] Morphology
River sharks are very similar in overall morphology to requiem 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;
- the second dorsal fin is 1/2 to 3/5 the height of the first dorsal fin;
- the origin of the second dorsal fin is slightly anterior to the origin of the anal fin;
- precaudal pit is longitudinal rather than crescent-shaped.
[edit] Species
- Ganges shark, Glyphis gangeticus (Müller & Henle, 1839)
- Speartooth shark, Glyphis glyphis (Müller & Henle, 1839)
- Irrawaddy River shark, Glyphis siamensis (Steindachner, 1896)
- Bizant river shark, Glyphis sp. A, not yet described.
- Borneo river shark, Glyphis sp. B, not yet described.
- New Guinea river shark, Glyphis sp. C, not yet described.
[edit] References
- Glyphis (TSN 160460). Integrated Taxonomic Information System. Accessed on 4 May 2006.
- Northern Speartooth Shark - Glyphis sp. C
- Compagno, Dando, & Fowler, Sharks of the World, Princeton University Press, New Jersey 2005 ISBN 0-691-12072-2
