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Ganges River Platanista - Platanista gangetica

Also known as the blind river dolphin, Gangetic platanista, susu, bhulan, or South Asian river dolphin, this big-flippered, long-beaked, and sightless freshwater cetacean has about as much charm as a gharial with poked-out eyeballs - a far cry from its “charismatic” ocean-dwelling cousins.

But hey, at least the massive, curved, two-inch-long teeth don’t last forever! No, if the dolphin lives more than a few years (never a sure thing in the over-trafficked and heavily polluted Ganges and Indus rivers), those skewers are broken and ground into little pegs, only adding to their charm. Though the big teeth help to catch and hold fish and shrimp when the dolphin is young, if they make it beyond their first decade, they’re adept enough at catching prey that the little pegs are enough.

Note how big the melon on their foreheads is. Like all toothed whales, the susu uses echolocation to find its food, but unlike many of the others (such as oceanic dolphins), the susu lives its entire life in a very murky, dark environment. It finds mates (as they live most of their life alone, they don’t have a pod to find females in or with), avoids predators, and conducts its entire life via echolocation, as its eyes are only capable of distinguishing light from dark.

Despite their less-than-charming looks, the susu is an integral part of the ecosystem in both the Ganges and Indus riverways, and is endangered in all parts of its habitat. There are less than 4000 individuals left in the wild, and none in captivity. Hunting for “traditional medicine" (yeah, these guys are "aphrodisiacs". Go ahead, try to wrap your head around that) and poisoning from pollution due to factory runoff are still their primary threats.

Nevertheless, the reduction of runoff in the Indus in the past decade, and subsequent rise in its dolphin population proves that we can save these creatures - none of the three subpopulations are at a level where they’re safe, but all three can be salvaged if we just make a few changes. Not to mention, people use both of those rivers for water, bathing, and fishing. It really benefits everyone if we stop pouring chemical waste into them.

Older susu:The Strange and  Beautiful River Dolphins." Kate H, September 2011.

Young adult susu skull cast: Children’s Museum of Indianapolis via Wikimedia Commons

Susu illustration: Illustrations of Indian Zoology, Part 2. Major-General Hardwicke for John Edward Gray, 1833-1834.

"External similarities among the three extant river dolphins and Pontoporia. The painting shows shared characteristics including long and narrow rostrum, small eyes, and broad forelimb flippers. A poorly-developed dorsal fin characterizes Inia (top), Platanista (second from top), and Lipotes (second from bottom) but is absent in the coastal Pontoporia (bottom). Note that the painting is for comparative purposes only; the geographic ranges of these species are disjunct”

A supermatrix analysis of genomic, morphological, and paleontological data from crown Cetacea. Jonathan H Geisler, Michael R McGowen, Guang Yang and John Gatesy. BMC Evolutionary Biology 2011, 11:112 doi:10.1186/1471-2148-11-112

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INDUS RIVER DOLPHIN CALVES SUCCESSFULLY RESCUED IN EASTERN PAKISTAN

WWF Pakistan

The calves were a male, 81.2 cm in length and weighing approximately 6 kg and a female, 91.4 cm in length and weighing about 9 kg.

Numbers for this species have dramatically declined since the construction of the irrigation system in the Indus. Most now remain in a 1200 km stretch of the Indus River. The Indus River dolphin is one of the world’s rarest mammal and most endangered cetaceans. A 2011 dolphin population survey estimated the population to be 1,297 individuals

  • Info and pics WWF-Pakistan

Squalodon could be termed a marine river dolphin. This may seem like a contradiction of terms, in a way, but its closest living relatives are the Indus and Ganges river dolphins of South Asia (both in twin subspecies within Platanista gangetica). With marine species like Squalodon to show us the evolutionary history of our modern cetacean groups, and the fact that ‘river dolphin’ is really a paraphyletic grouping (that is to say, all modern river dolphins aren’t necessarily one another’s closest living relatives—and to complicate it further, none of them are the closest relatives of ‘true’ dolphins!), it can be assumed that the different groupings of river dolphins each took the trek from the sea to freshwater convergently, and at different points in their respective histories.

Now then.

Squalodon was among one of the first extinct whales identified in the early decades of the 19th Century, but at first its teeth (named thus for their resemblance to those of the spurdog sharks, Squalus) were mistaken for those of an iguanodontian dinosaur! It wasn’t until further remains were found that it was (correctly) identified as an extinct odontocete whale. Squalodon was part of a mostly-Paleogene family of platanistoids, the eponymous Squalodontidae. It achieved multi-continental distribution, and is known from the Americas, Europe, and Asia. It grew to a size comparable to the modern orca, and was in all likelihood similarly predatory.

Portrayed here by Craig Dylke, pursuing a pack of seabirds in the shallow seas of the submerged continent of Zealandia. (It must be noted that Squalodon proper is not attested from New Zealand, but a close relative, Tangaroasaurus—bearing that unfortunate malady it shares in common with Basilosaurus of initially being mistaken as reptilian—is.)

PLASTINOIDS DOLPHINS

John D Orcutt UO

Modern dolphins are by many measures the most successful group of cetaceans: they are diverse, intelligent, and in many cases have proven more resistant to anthropogenic change than their larger relatives. Some dolphins have even colonized freshwater environments. These ‘river dolphins’ are often referred to as platanistoids, a name based on the modern genus Platanista that inhabits the Ganges and Indus Rivers (other generus inhabit the AmazonLa Plata, and - until recently - Yangtze Rivers), but there has been much debate about whether or not all river dolphins are actually related, as was originally thought. If the world’s living and extinct river dolphins really are the product of separate colonizations of freshwater habitats, then they represent a striking example of convergent evolution: platanistoids share many morphological characteristics, perhaps the most striking being a long, pointed rostrum (or snout; this feature makes them similar in form to many other fish-eating vertebrates, such as ichthyosaurs and swordfish).

The specimen at left, an as-yet unnamed platanistoid from the mid-Miocene of Oregon, exhibits this characteristic rostrum. However, it was uncovered from the Astoria Formation, a marine unit from the Oregon Coast, making it a saltwater freshwater dolphin. This implies that at least one lineage of river dolphins evolved its unusual morphology before migrating inland. 

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