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Hey all, I wrote up some more on our recent paper on the giant dolphin Ankylorhiza (formerly Genus Y) from the Oligocene of South Carolina - this is a bit more interesting as it covers the anatomy, adaptations, feeding ecology, and evolutionary implications of the discovery. Hope you can give it a read! https://coastalpaleo.blogspot.com/2020/08/ankylorhiza-tiedemani-giant-dolphin_9.html
Hey y'all - we finally re-named "Squalodon" tiedemani, now known as Ankylorhiza tiedemani - a large macropredatory killer whale like dolphin with some implications for the early feeding ecology of odontocetes (toothed/echolocating whales) and convergent evolution of swimming in baleen whales (mysticetes) and odontocetes after their split some ~35-36 million years ago. I've copied our FB post text below so I don't need to re-type it all. Introducing the species formerly known as Genus Y: Ankylorhiza tiedemani! This large dolphin was originally named from a partial but uninformative skull dredged from the Wando River in South Carolina in the 1880s, erroneously placed in the genus Squalodon, and without any age data. Our new skeleton, CCNHM 103, is nearly complete, and demonstrates 1) that it definitely isn’t Squalodon, needing the new genus name Ankylorhiza, and 2) the species is from the Oligocene epoch. The new skeleton was discovered by Mark Havenstein in the ~24 million year old Chandler Bridge Formation near Summerville SC in the mid 1990s. There are two major aspects to this new study, published today in the prestigious journal Current Biology by one of our paleontologists, Dr. Boessenecker, and colleagues (Dr. Morgan Churchill, Dr. Emily Buchholtz, Dr. Brian Beatty, and Dr. Jonathan Geisler). The first and more simple finding is that Ankylorhiza is large and has several adaptations for feeding on large prey: large, thick-rooted teeth, a robust snout, sharp (and occasionally serrated) cutting edges on its teeth, enormous jaw muscles, and a killer whale-like range of neck motion. This evidence all points toward Ankylorhiza being an apex predator, reinvading the niche formerly occupied by predatory basilosaurid whales which died out only 5 million years before the oldest fossils of Ankylorhiza. The second and more surprising aspect is what the skeleton tells us about the evolution of swimming adaptations. Modern baleen whale and echolocating whale skeletons are remarkably similar, and assumed to have remained static since the split between the two groups some 35 million years ago. Indeed, most “whaleontologists” working on early baleen whales and early dolphins are ‘headhunters’ and focus exclusively on skulls. The flipper and vertebrae of Ankylorhiza indicate that many features in modern baleen (mysticetes) and echolocating whales (odontocetes) actually evolved twice, in parallel – we call this convergent evolution. We know this since modern mysticetes and odontocetes share many features– including a remarkably shortened humerus (upper arm bone; still a bit long in Ankylorhiza), lost muscle attachments of the humerus (still present in Ankylorhiza), short blocky finger bones (long/skinny in Ankylorhiza), a narrow tail stock (wide in Ankylorhiza), and more than 23 or so tail vertebrae (fewer than that in Ankylorhiza). These features therefore must have evolved convergently – likely driven by the locking of the elbow joint, forcing the flipper to be used only for steering and all propulsive force to come from the tail. You can read the paper here: https://www.cell.com/current-biology/fulltext/S0960-9822(20)30828-9 (please email us if you would like a pdf of the paper)