Tuesday 3 May 2022

Evolution News - When Lizards and Snakes Evolved

The fossil of Jurassic lizard Eichstaettisaurus.

Image credit: Jorge Herrera Flores
May: Researchers discover overlooked lizards | News and features | University of Bristol

With so many science papers casually and unintentionally refuting creationism just by revealing the facts, most weeks are bad weeks for creationists and their cults, but this week has been worse than most and it's only half done!

On top of the news of how environmental changes have been shown to influence evolution, just as the Theory of Evolution explains, we now have a paper which sheds more light on the evolution of the squamates (i.e. cold-blooded vertebrates with scales - snakes and lizards) and which shows the scientists involved have no doubts about the TOE being the grand unifying theory in biology that makes best sense of the data.

A collared lizard posing on a rock in Colorado.

Pahcal123 under CC BY-SA 4.0 license
This paper by scientists from the Institut Català de Paleontologia Miquel Crusafont (ICP) and the University of Bristol, in the best traditions of science, challenges the previous consensus over just when this order radiated into its current diversity and pushes that back from the Cretaceous Era between 145.5 and 65.5 million years ago, into the Jurassic, between 201 and 145 million years ago. It had previously been assumed that the main period of evolutionary radiation had been part of the so-called Cretaceous Terrestrial Revolution, when many terrestrial tetrapod groups like mammals, lizards and birds, apparently underwent a great diversification, triggered by the rise of flowering plants.

However, the research team led by Dr Arnau Bolet, palaeontologist at the Institut Català de Paleontologia Miquel Crusafont and the University of Bristol, has shown that, although Jurassic squamate fossils are rare, it is possible to detect the more advanced features found in modern species in them, showing that the major phases of evolutionary diversification had occurred by then.

As the Bristol University press release accompanying the team's open access published paper in the online journal, eLife, explains:

Even though Jurassic squamates are rare, reconstructed evolutionary trees show that all the main specializations of squamates evolved then, and it’s possible to distinguish adaptations of geckoes, iguanas, skinks, worm lizards, and snakes some 50 million years earlier than had been thought. But how could the scarce Jurassic fossils suggest an early burst in evolution? The key is in their anatomy.

Michael J. Benton, co-author
School of Earth Sciences
University of Bristol, Bristol, UK.
The few Jurassic squamates do not show primitive morphologies as would be expected, but they relate directly to the diverse modern groups. “Instead of finding a suite of generalized lizards on the stem of the squamate tree, what we found in the Jurassic were the first representatives of many modern groups, showing advanced morphological features”, says Arnau Bolet, lead author of the article.

The observed times of divergence, morphospace plots and evolutionary rates, all suggest that the Jurassic was a time of innovation in squamate evolution, during which the bases of the success of the group were established. According to these results, the apparent sudden increase in diversity observed in the Cretaceous could be related to an improved fossil record, capable of recording a larger number of species, or to a burst of origins of new species related to the new kinds of forests and insects.

Instead of finding a suite of generalized lizards on the stem of the squamate tree, what we found in the Jurassic were the first representatives of many modern groups, showing advanced morphological features.

Arnau Bolet, lead author
Institut Català de Paleontologia Miquel Crusafont
Universitat Autònoma de Barcelona
Cerdanyola del Vallès, Spain
And School of Earth Sciences
University of Bristol, Bristol, UK.
The Squamata is the largest order of reptiles, including lizards, snakes and worm lizards. Squamates are all cold-blooded, and their skins are covered by horny scales. They are key parts of modern terrestrial faunas, especially in warmer climates, with an astonishing diversity of more than 10,000 species. However, understanding the evolutionary paths that forged their success are still poorly understood.

Establishing the timing and mode of radiation of squamates is key for not only understanding the dynamics of terrestrial ecosystems in the Mesozoic, but also for deciphering how the group achieved an astonishing diversity of more than 10,000 species, only rivalled by birds among tetrapods.
Copyright: © 2022 The authors. Published by eLife
Open access
The team's paper in eLife gives more technical details:

The squamates (lizards, snakes, and relatives) today comprise more than 10,000 species, and yet their sister group, the Rhynchocephalia, is represented by a single species today, the tuatara. The explosion in squamate diversity has been tracked back to the Cretaceous Terrestrial Revolution, 100 million years ago (Ma), the time when flowering plants began their takeover of terrestrial ecosystems, associated with diversification of coevolving insects and insect-eating predators such as lizards, birds, and mammals. Squamates arose much earlier, but their long pre-Cretaceous history of some 150 million years (Myr) is documented by sparse fossils. Here, we provide evidence for an initial radiation of squamate morphology in the Middle and Late Jurassic (174–145 Ma), and show that they established their key ecological roles much earlier than had been assumed, and they have not changed them much since.

I doubt any creationists have had the courage to read this far, but if they have, they might like to note the eLife editor's evaluation:
Editor's evaluation

This article presents an evaluation of the macroevolutionary history of squamates (lizards, snakes, and relatives) and is relevant to evolutionary biologists and paleontologists interested in this group. The ‘early burst’ of disparity in squamates demonstrates that squamates established their morphospace range much earlier than had been assumed, and the long-term stable morphospace occupation ever since. [My emphasis]
Not only does this paper illustrate just how central the TOE is to interpreting the fossil record, but the editor of the journal in which it is published calls it "an evaluation of macroevolutionary history".

No doubt these examples of macroevolution will be completely ignored by creationists desperate to maintain the ludicrous belief that macro-and micro-evolution are somehow different processes and that the latter is possible but some mysterious process prevents the former from happening.

Just another in a long list of biology research papers exposing the facts that casually refute creationism without any effort or intent on the part of the authors.

Thank you for sharing!

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