The Ganges shark (Glyphis gangeticus) is a critically endangered species of requiem shark found in the Ganges River (Padma River) and the Brahmaputra River of India and Bangaladesh. It is often confused with the more common bull shark (Carcharhinus leucas), which also inhabits the Ganges River and is sometimes incorrectly referred to as the Ganges shark. The genus is currently considered to contain three recent species; genetic evidence has shown that both the Borneo river shark (G. fowlerae) and Irrawaddy river shark (G. siamensis) should be regarded as synonyms of the Ganges shark, expanding the range of the species to Pakistan, Myanmar, Borneo, and Java. While the other members of the genus Glyphis occur in coastal marine waters as well as rivers, the Ganges shark is found only in fresh water, making it the world's only exclusively freshwater shark. The species remains poorly known and very rare. Taxonomy Formerly the Borneo river shark (Glyphis fowlerae) and the Irrawaddy river shark (Glyphis siamensis) were considered to represent two other species in the genus Glyphis. They have recently been reclassified as G. gangeticus based on genetic studies, and their scientific names are treated as synonyms. The Borneo river shark is known only from the Kinabatangan River in Borneo. It can reach a length of . Only 13 specimens are known to science, all collected in 1996. Expeditions in 2010 and 2011 failed to find any, and while fishermen recognised the shark, they have not been seen for many years. The Irrawaddy river shark is known only from a single museum specimen originally caught at the mouth of the Irrawaddy River in Myanmar, a brackish-water locality in a large, heavily silt-laden river lined with mangrove forests. It was collected in the 19th century and described as Carcharias siamensis by Austrian ichthyologist Franz Steindachner, in Annalen des Naturhistorischen Museums in Wien (volume 11, 1896). However, subsequent authors doubted the validity of this species, regarding it as an abnormal bull shark (Carcharhinus leucas), until in 2005 shark systematist Leonard Compagno recognized it as distinct member of the genus Glyphis. The specimen is a 60-cm-long immature male. It closely resembles the Ganges shark, but has more vertebrae (209 versus 169) and fewer teeth (29/29 versus 32–37/31–34). A possibly undescribed species of Glyphis is known from Mukah in Borneo, as well as Bangladesh. The status of a Borneo specimen from Sampit remains unclear. Physical appearance G. gangeticus