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Ankylorhiza tiedemani: "new" large bodied killer whale like dolphin from South Carolina Oligocene


Boesse

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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)

 

bobby ankylorhiza smaller.jpg

Ankylorhiza 1-1 flattened copy.jpg

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Genus Y had been mentioned in the literature since Whitmore and Sanders (1977). However, new research into early odontocete evolution prompted a new look at Genus Y, and Dooley (2003) noted that "Squalodon" tiedemani is very similar to Genus Y, and that one specimen (USNM 183023) from the Calvert Formation that he had referred to tiedemani in a 1991 thesis represented a new Squalodon species that he later (2005) named S. whitmorei. Also note that Dooley (2003) considers the problematic odontocete Saurocetus to be a probable relative of Ankylorhiza based on examination of undescribed specimens in the Charleston Museum.

 

 

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@Boesse This is great news Bobby. You had said that one of the earbones I donated to the Museum (at the 2019 Aurora Fossil Festival) appeared to be from genus Y. If that was correct, how cool. That would put A. tiedemani as present in either the Belgrade or the River Bend Formation. It also makes me wonder if the tooth I donated at the 2016 festival could be from this species.

Bulldozers and dirt Bulldozers and dirt
behind the trailer, my desert
Them red clay piles are heaven on earth
I get my rocks off, bulldozers and dirt

Patterson Hood; Drive-By Truckers

 

image.png.0c956e87cee523facebb6947cb34e842.png May 2016  MOTM.png.61350469b02f439fd4d5d77c2c69da85.png.a47e14d65deb3f8b242019b3a81d8160.png.b42a25e3438348310ba19ce6852f50c1.png May 2012 IPFOTM5.png.fb4f2a268e315c58c5980ed865b39e1f.png.1721b8912c45105152ac70b0ae8303c3.png.2b6263683ee32421d97e7fa481bd418a.pngAug 2013, May 2016, Apr 2020 VFOTM.png.f1b09c78bf88298b009b0da14ef44cf0.png.af5065d0585e85f4accd8b291bf0cc2e.png.72a83362710033c9bdc8510be7454b66.png.9171036128e7f95de57b6a0f03c491da.png Oct 2022

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Excellent work Bobby :yay-smiley-1:

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Every once in a great while it's not just a big rock down there!

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31 minutes ago, sixgill pete said:

@Boesse This is great news Bobby. You had said that one of the earbones I donated to the Museum (at the 2019 Aurora Fossil Festival) appeared to be from genus Y. If that was correct, how cool. That would put A. tiedemani as present in either the Belgrade or the River Bend Formation. It also makes me wonder if the tooth I donated at the 2016 festival could be from this species.

Hey Don! Good question. I believe one of your bullae belongs to Ankylorhiza or something similar; the big periotic found by @Al Dente is something else, quite probably Squalodon proper. Another clear Ankylorhiza specimen from Belgrade is a nice tooth with longitudinal fluting found and donated by Julie Niederkorn about a year ago.

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2 minutes ago, Boesse said:

Hey Don! Good question. I believe one of your bullae belongs to Ankylorhiza or something similar; the big periotic found by Eric (can't remember TFF username) is something else, quite probably Squalodon proper. Another clear Ankylorhiza specimen from Belgrade is a nice tooth with longitudinal fluting found and donated by Julie Niederkorn about a year ago.

That's great. Good to see the NCFC well represented.

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Bulldozers and dirt Bulldozers and dirt
behind the trailer, my desert
Them red clay piles are heaven on earth
I get my rocks off, bulldozers and dirt

Patterson Hood; Drive-By Truckers

 

image.png.0c956e87cee523facebb6947cb34e842.png May 2016  MOTM.png.61350469b02f439fd4d5d77c2c69da85.png.a47e14d65deb3f8b242019b3a81d8160.png.b42a25e3438348310ba19ce6852f50c1.png May 2012 IPFOTM5.png.fb4f2a268e315c58c5980ed865b39e1f.png.1721b8912c45105152ac70b0ae8303c3.png.2b6263683ee32421d97e7fa481bd418a.pngAug 2013, May 2016, Apr 2020 VFOTM.png.f1b09c78bf88298b009b0da14ef44cf0.png.af5065d0585e85f4accd8b291bf0cc2e.png.72a83362710033c9bdc8510be7454b66.png.9171036128e7f95de57b6a0f03c491da.png Oct 2022

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5 hours ago, DD1991 said:

Genus Y had been mentioned in the literature since Whitmore and Sanders (1977). However, new research into early odontocete evolution prompted a new look at Genus Y, and Dooley (2003) noted that "Squalodon" tiedemani is very similar to Genus Y, and that one specimen (USNM 183023) from the Calvert Formation that he had referred to tiedemani in a 1991 thesis represented a new Squalodon species that he later (2005) named S. whitmorei. Also note that Dooley (2003) considers the problematic odontocete Saurocetus to be a probable relative of Ankylorhiza based on examination of undescribed specimens in the Charleston Museum.

 

 

 

Good question, and very observant! I think that was based on the Boreske et al. (1972) skull, which was from the Pungo River Limestone at Lee Creek and was published because the skull had extensive clam borings, indicating it had been reworked. Anywho, they (after Remington Kellogg's identification, I believe) identified it as S. tiedemani. So this was a case of mistaken identity: many squalodon specimens, clearly larger than S. calvertensis, historically being assigned to S. tiedemani, the holotype of which was for a very long time so incomplete that it was not possible to clearly distinguish it from Squalodon sensu stricto.

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