Speartooth shark

Lore & Background

German biologists Johannes Müller and Jakob Henle originally described the speartooth shark as Carcharias (Prionodon) glyphis in their 1839–41 Systematische Beschreibung der Plagiostomen, based on a stuffed juvenile female 1 m (3.3 ft) long of unknown origin. In 1843, Swiss-American zoologist Louis Agassiz proposed the new genus Glyphis for this species and a fossil relative. The use of Glyphis for river sharks did not gain wide acceptance until Jack Garrick's 1982 revision of Carcharhinus. Müller and Henle's type specimen remained the sole known record until specimens of the 'Bizant river shark' were caught in Australia in 1982; subsequent work by Leonard Compagno, William White, and Peter Last confirmed it was the same species as G. glyphis.

The speartooth shark has a streamlined, robust body with a short, wide head, tiny eyes, and a relatively large second dorsal fin. Its teeth are large, triangular, and serrated in the upper jaw, and narrow, spear-like, and serrated only near the tips in the lower jaw. Adults grow to about 2.6 m (8.5 ft) long. The species is plain slate-gray above and white below, with a black blotch beneath each pectoral fin near the tip. It preys on demersal bony fishes and crustaceans, and is adapted for hunting in near-complete darkness, relying more on electroreception than sight. Reproduction is viviparous, with females forming a placental connection to their young; birthing seems to occur from October to December.

Reader's Guide

The speartooth shark is significant as one of the rarest and most specialized members of the river shark genus, with a global population estimated at no more than 2,500 mature individuals. Its restricted range—limited to a few large, mangrove-lined tropical rivers in northern Australia and New Guinea—and stringent habitat requirements make it highly susceptible to threats such as incidental capture in fisheries and habitat degradation. The species' ability to tolerate a wide range of salinities, from nearly fresh to nearly marine, and its behavior of moving with tidal currents to conserve energy, highlight its unique adaptations to turbid, fast-flowing environments. The discovery of adults only in 2014, and a new population in the Roper River in 2024, underscore how little is known about this species. Fossil teeth from the Early Miocene to Pliocene of Portugal and the Pliocene of Italy suggest it once had a much larger range. Its listing as vulnerable by the International Union for Conservation of Nature reflects the urgent need for conservation measures to protect this elusive shark.

Did You Know?

• The speartooth shark was originally described from a single stuffed juvenile female of unknown origin, possibly from the Indian Ocean or the South China Sea.
• Adults were entirely unknown until 2014, when three specimens were documented on Daru island, Papua New Guinea.
• A new population was found in the Roper River of the Northern Territory in 2024, the first time documented living in that area.
• The species' teeth are large, triangular, and serrated in the upper jaw, but narrow and spear-like in the lower jaw.