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Live birth in lizards at 250 mya

artist’s impression of Dinocephalosaurus/Dinghua Yang

From ScienceDaily:

Until recently it was thought the third major group of living land vertebrates, the crocodiles and birds (part of the wider group Archosauromorpha) only laid eggs.

“Indeed, egg-laying is the primitive state, seen at the base of reptiles, and in their ancestors such as amphibians and fishes,” Professor Aitchison said.

“Further evolutionary analysis revealed the first case of live birth in such a wide group containing birds, crocodilians, dinosaurs and pterosaurs among others, and pushes back evidence of reproductive biology in the group by 50 million years,” Professor Liu said.

“Information on reproductive biology of archosauromorphs before the Jurassic Period was not available until our discovery, despite a 260 million-year history of the group.” More. Paper. (public access) – Jun Liu, Chris L. Organ, Michael J. Benton, Matthew C. Brandley, Jonathan C. Aitchison. Live birth in an archosauromorph reptile. Nature Communications, 2017; 8: 14445 DOI: 10.1038/ncomms14445

But note,

Professor Mike Benton of the University of Bristol said analysis of the evolutionary position of the new specimens showed no fundamental reason why archosauromorphs could not have evolved live birth.

But wait! What, exactly, would the “fundamental reason archosauromorphs could not have evolved live birth” be, had it turned out to exist? These days, it may be necessary to explain in more detail to a restive public.

For example, suppose an expert says that there is a “fundamental reason” life forms won’t survive at absolute zero. Most people won’t ask for a lot of confirmation.

By contrast, we just want to know more about these new developments, considering how often we have been told that live birth is an evolutionary advance over egg-laying. Is it? Or was that just something Darwin’s followers liked to say, thinking they’d never be confuted by evidence?

Also, one wonders, how many evolutionary advances have there really been in the last quarter billion years, apart from humans? Just a thought.

See also: Earliest animals with true body cavities found at 30 mya earlier than thought


Stasis: Life goes on but evolution does not happen

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