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Episode 459: Strange Little Dolphins

Episode 459: Strange Little Dolphins

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 Thanks to Alexandra, Jayson, and Eilee for their suggestions this week! Further reading: Scientists have discovered an ancient whale species. It may have looked like a mash-up of ‘a seal and a Pokémon’ The nomenclatural status of the Alula whale Field Guide of Whales and Dolphins [1971] The little Benguela dolphin [photo taken from this site]: The spinner dolphin almost looks like it has racing stripes [photo by Alexander Vasenin - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=25108509]: The Alula whale, which may or may not exist: Show transcript: Welcome to Strange Animals Podcast. I’m your host, Kate Shaw. This week let’s learn about some whales and dolphins, including an ancient whale and a mystery whale, all of them really small. Thanks to Alexandra, Eilee, and Jayson for their suggestions! Let’s start with an ancient whale, suggested by Jayson. The genus Janjucetus has been known since its first species was described in 2006, after a teenage surfer in Australia discovered the fossils in the late 1990s. It grew to about 11 feet long, or 3.5 meters, and lived about 25 million years ago. So far it’s only been found around Australia. But much more recently, just a few months ago as this episode goes live, a new species was described. That’s Janjucetus dullardi, also found in Australia along the same beach where the first Janjucetus species was found, and dating to around the same time period. We don’t know a lot about the newly described whale, since it’s only known from some teeth and partial skull. Scientists think the individual was a juvenile and estimate it was only around 6 feet long when it died, or 2.8 meters. Small as it was, it would have been a formidable hunter when it was alive. Its broad snout was shaped sort of like a shark’s and it had strong, sharp teeth and large eyes. Because it was an early whale, it wouldn’t have looked much like the whales alive today. It might even have had tiny vestigial back legs. Its eyes were huge in proportion to its head, about the size of tennis balls, and it probably relied on its eyesight to hunt prey because it couldn’t echolocate. Its serrated teeth and strong jaws indicate that it might have hunted large animals, but some scientists suggest it could also filter feed the same way a crabeater seal does. Modern crabeater seals have similar teeth as Janjucetus, as do a few other seals. The projections on its teeth interlock when the seal closes its mouth, so to filter feed the seal takes a big mouthful of water, closes its teeth, and uses its tongue to force water out through its teeth. Amphipods and other tiny animals get caught against the teeth and the seal swallows them. If Janjucetus did filter feed, it probably also hunted larger animals. Otherwise its jaws wouldn’t have been so strong or its teeth so deeply rooted. But Janjucetus wasn’t related to modern toothed whales. While it wasn’t a direct ancestor of modern baleen whales, it was part of the baleen whale’s family tree. Baleen whales, also called mysticetes, have baleen plates made of keratin instead of teeth. After the whale fills its mouth with water, it closes its jaws, pushes its enormous tongue up, and forces all that water out through the baleen. Any tiny animals like krill, copepods, small squid, small fish, and so on, get trapped in the baleen. It’s just like the crabeater seal, but really specialized and way bigger. Whether or not Janjucetus could and did filter feed doesn’t really matter, because the fact that it’s an ancestral relation of modern baleen whales but it had teeth helps us understand more about modern whales. Next, Eilee wanted to learn about the Benguela [BEN-gull-uh] dolphin, also called Heaviside’s dolphin. It lives only off the southwestern coast of Africa, and it’s really small, only a little over 5 and a half feet long at the most, or 1.7 meters. It’s dark gray with white markings,
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