Brocklehurst and Field 2024 attempt to date the radiation of extant birds
Thursday, April 4, 2024 15:22
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Brocklehurst and Field 2024 report,
“Only the fossil record can provide direct evidence of the earliest stages of crown bird evolutionary history. However, considering the ongoing scarcity of this direct evidence, improved inferences based on models of molecular and morphological evolution are necessary to shed light on the Mesozoic origins of crown birds.”
“Only the fossil record can provide direct evidence of the earliest stages of crown bird evolutionary history. However, considering the ongoing scarcity of this direct evidence, improved inferences based on models of molecular and morphological evolution are necessary to shed light on the Mesozoic origins of crown birds.”
The authors’ set-up is correct. Their conclusion is not. The last common ancestor of crown birds in the fossil record would be the direct evidence the authors are seeking, but they put no effort into that search. Instead they took a detour and relied on less-preferred, indirect methods: tip dating and Bayes factors.
A last common ancestor is nothing more than a single taxon at the base of a clade. Any cladogram will provide that. More taxa provide greater resolution and confidence.
Brocklehurst and Field report,
“Our analysis of morphological data including both extant and extinct taxa (including a broad sample of neornithine and non-crown avialan lineages) rejects an origin of crown birds occurring deep in the Early Cretaceous. It also rejects the scenario at the opposite extreme: an origin of crown birds occurring less than 10 Myr before the end of the Cretaceous Period. Instead, the pattern of diversification best supported by the morphological data is one where neornithines originate between the Early and Late Cretaceous.”
“Our analysis of morphological data including both extant and extinct taxa (including a broad sample of neornithine and non-crown avialan lineages) rejects an origin of crown birds occurring deep in the Early Cretaceous. It also rejects the scenario at the opposite extreme: an origin of crown birds occurring less than 10 Myr before the end of the Cretaceous Period. Instead, the pattern of diversification best supported by the morphological data is one where neornithines originate between the Early and Late Cretaceous.”
Figure 1. Toothless Early Cretaceous Archaeorhynchus is the last common ancestor of all extant birds in the LRT.
Taxon exclusion
(= omitting the last common ancestor) mar this study in several ways.
(= omitting the last common ancestor) mar this study in several ways.
Galloanserae is a genomic clade accepted by these authors, and many others, but not recovered by trait analysis (the LRT). Ducks and geese share few to no unique traits with chickens and pheasants.
Trait analysis places Late Cretaceous Asteriornis with geese, a highly derived avian clade, and Latest Cretaceous Vegavis with kiwis, snipes and other basal avians. Patagopteryx is a tiny Mesozoic ostrich not mentioned in the text. Paleocene penguins, another highly derived avian clade not mentioned in the text, by themselves indicate a wide gamut of bird survival spanning the asteroid event.
The last common ancestor of all extant birds in trait analysis (the LRT) is Early Cretaceous (Yixian Formation) Archaeorhynchus [Fig 1]. This is the “direct evidence of the earliest stages of crown bird evolutionary history” the authors considered ideal, but unattainable. Turns out they did not even try. Archaeorhynchus is not mentioned in their text. Taxon exclusion remains the number one problem in paleontology in 2024. Trusting deep time genomes remains the number two problem.
Cladogram and data links here: reptileevolution.com/reptile-tree
References
Brocklehurst N and Field DJ 2024. Tip dating and Bayes factors provide insight into the divergences of crown bird clades across the end-Cretaceous mass extinction. Proc. R. Soc. B 291: 20232618. https://doi.org/10.1098/rspb.2023.2618
Brocklehurst N and Field DJ 2024. Tip dating and Bayes factors provide insight into the divergences of crown bird clades across the end-Cretaceous mass extinction. Proc. R. Soc. B 291: 20232618. https://doi.org/10.1098/rspb.2023.2618
Source: https://pterosaurheresies.wordpress.com/2024/04/05/brocklehurst-and-field-2024-attempt-to-date-the-radiation-of-extant-birds/
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