The Jurassic rise of squamates as supported by lepidosaur disparity
and evolutionary rates

Abstract

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.

Open access:
https://elifesciences.org/articles/66511

A glimpse into the past of sci.bio.paleontology, before turning to the matter at hand:
Back in the 1990's, when s.b.p. was much more active than now, one of the
regulars went by the moniker "Cal King". Did you and he overlap, Pandora?

He was as interested in squamates as I already was in mammals back then, and he explained
his interest in them by the huge variety of their morphology, which he considered
to be greater than that of mammals.

On Wednesday, May 4, 2022 at 9:23:54 AM UTC-4, Pandora wrote:
> The Jurassic rise of squamates as supported by lepidosaur disparity
> and evolutionary rates

The word "disparity" caught my attention, because that was what Cal King was
referring to in different words back then. It was only long after he left s..b.p.
that I came to realize how much a deep understanding of disparity is essential to
developing a theory of macroevolution, and thereby to a theory of evolution worthy of the name.

As it is, the theory of evolution is still mostly a theory of microevolution,
with a few forays in the direction of macroevolution and mega-evolution
as described by George Gaylord Simpson.

Our understanding of disparity is still in the formative stages,
but the article represents a major effort in developing a true picture of disparity.

The most remarkable thing about this article is the rare glimpse it
gives the public of the editorial process, beginning with the decision
letter and extensive reviewer remarks, followed by a very detailed
author response. All these together take up almost as much space
as the research article itself.
I was pleased to see the following comment by reviewer #2:

"The evolution of disparity, as distinct from species diversity, is a central question in macroevolution."

I was also pleased to see the following:

"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."

This evaluation forms an essential supplement to the actual abstract:

> Abstract
> 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.

This is about diversity, which is often confused with disparity,
partly under the influence of the word "biodiversity." Diversity is
simply measured by the number of species in a group.

>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.
>

The expression used above, "initial radiation of squamate morphology,"
hints at the idea of disparity: the radiation of characters in various directions,
giving shape to a "morphospace" which is the subject of disparity analysis.
> Open access:
> https://elifesciences.org/articles/66511

I am very glad you shared this with us, Pandora.
I've spent all the time I can spare for it this week,
but I will be studying it very carefully in the coming months, on and off.

I was going to respond this week also to an earlier article you posted about
on monotreme evolution, but I'll have to postpone that until next week.

Peter Nyikos
Professor, Department of Mathematics
University of South Carolina -- standard disclaimer --
https://people.math.sc.edu/nyikos/