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Body plan pushed back hundreds of millions of years


The vertebrate family tree is all shook up, we hear, by a fossil hagfish (right: Cretaceous hagfish fossil, 100 mya/Tetsuto Miyashita, University of Chicago).

From ScienceDaily:

Paleontologists at the University of Chicago have discovered the first detailed fossil of a hagfish, the slimy, eel-like carrion feeders of the ocean. The 100-million-year-old fossil helps answer questions about when these ancient, jawless fish branched off the evolutionary tree from the lineage that gave rise to modern-day jawed vertebrates, including bony fish and humans.

The fossil, named Tethymyxine tapirostrum,is a 12-inch long fish embedded in a slab of Cretaceous period limestone from Lebanon. It fills a 100-million-year gap in the fossil record and shows that hagfish are more closely related to the blood-sucking lamprey than to other fishes. This means that both hagfish and lampreys evolved their eel-like body shape and strange feeding systems after they branched off from the rest of the vertebrate line of ancestry about 500 million years ago.

“This is a major reorganization of the family tree of all fish and their descendants. This allows us to put an evolutionary date on unique traits that set hagfish apart from all other animals,” said Tetsuto Miyashita, PhD, a Chicago Fellow in the Department of Organismal Biology and Anatomy at UChicago who led the research. The findings are published this week in the Proceedings of the National Academy of Sciences…

“We now have a fossil that can push back the origin of the hagfish-like body plan by hundreds of millions of years,” Miyashita said. “Now, the next question is how this changes our view of the relationships between all these early fish lineages.” Paper. (open access) – Yu-Ting Lai, Carol K. L. Yeung, Kevin E. Omland, Er-Li Pang, Yu Hao, Ben-Yang Liao, Hui-Fen Cao, Bo-Wen Zhang, Chia-Fen Yeh, Chih-Ming Hung, Hsin-Yi Hung, Ming-Yu Yang, Wei Liang, Yu-Cheng Hsu, Cheng-Te Yao, Lu Dong, Kui Lin, Shou-Hsien Li. Standing genetic variation as the predominant source for adaptation of a songbird. Proceedings of the National Academy of Sciences, 2019; 201813597 DOI: 10.1073/pnas.1813597116 More.

Well yes, if this checks out, it changes our view of “the relationships between all these early fish lineages” but it does something more. It’s an excellent example of stasis. Contrary to the Darwinian claim:

It may be said that natural selection is daily and hourly scrutinizing, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, wherever and whenever opportunity offers, at the improvement of each organic being in relation to its organic and inorganic conditions of life. (Darwin Online)

… once life forms have established something that works, they can stick with it for a very long time, maybe half a billion years or more. It’s more like conforming to an underlying pattern than like endless variation.

See also: Researchers: Coralline Red Algae Existed 300 Million Years Earlier Than Thought

SFlowers bloomed in the early Jurassic, 50 million years earlier than thought

Feathers originated 70 million years earlier than thought It certainly is “amazing,” as Professor Benton says, that a complex array of features appeared 250 million years ago, rather abruptly, just as life was recovering from the Permian extinction. Would anyone have predicted that? Talk about “fossil rabbits in the Cambrian.”


Stasis: Life goes on but evolution does not happen

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