Megaevolutionary dynamics in reptiles: Simoes et al. 2020

Simoes et al 2020 discuss
“rates of phenotypic evolution and disparity across broad scales of time to understand the evolutionary dynamics behind the origin of major clades, or how they relate to rates of molecular evolution.”

“Here, we provide a total evidence approach to this problem using the largest available data set on diapsid reptiles.”

Unfortunately not large enough to understand that traditional ‘diapsid’ reptiles are diphyletic, splitting in the Viséan and convergently developing two

“We find a strong decoupling between phenotypic and molecular rates of evolution,”

Yet another case of gene-trait mismatch in analysis.

“and that the origin of snakes is marked by exceptionally high evolutionary rates.”

Taxon exclusion is the reason for this exclusion.

Figure 1. Cladogram from Simoes et al. 2020. Gray tones added to show Lepidosauromorpha in the LRT.

Figure 1. Cladogram from Simoes et al. 2020. Gray tones added to show Lepidosauromorpha in the LRT.

“Here, we explore megaevolutionary dynamics on phenotypic and molecular evolution during two fundamental periods of reptile evolution: i) the origin and early diversification of the major lineages of diapsid reptiles (lizards, snakes, tuataras, turtles, archosaurs, marine reptiles, among others) during the Permian and Triassic periods,”

In the LRT the new archosauromorphs split from new lepidosauromorphs in the Viséan (Early Carboniferous).

“as the origin and evolution of lepidosaurs (lizards, snakes and tuataras) from the Jurassic to the present.”

In the LRT lepidosaurs had their origin in the Permian and the Simoes team ignores the Triassic radiation of lepidosaurs leading to tanystropheids and pterosaurs.

So without a proper and valid phylogenetic context,
why continue? How can they possibly discuss ‘rates of change’ if they do not include basal taxa from earlier period?

“Our results indicating exceptionally high phenotypic evolutionary rates at the origin of snakes further suggest that snakes not only possess a distinctive morphology within reptiles,  but also that the first steps towards the acquisition of the snake body plan was extremely fast.”

In the LRT many taxa are included in the origin of snakes from basal geckos. These are missing from Simoes list of snake ancestor.

Figure 1.  Subset of the LRT focusing on lepidosaurs and snakes are among the squamates.

Figure 1.  Subset of the LRT focusing on lepidosaurs and snakes are among the squamates.

In the LRT all sister taxa resemble one another
and document a gradual accumulation of derived traits.

If you have any particular evolutionary questions,
they were probably answered earlier in previous posts. Use the keyword box at upper right to seek your answer.

 

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