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Re: [dinosaur] Rates of morphological evolution in Early Cretaceous birds
During the Cretaceous, Ornithuromorpha favored terrestrial/aquatic
habitats, whereas Enantiornithes were more more arboreal. That's one
conclusion of this study. I'm not certain that this dichotomy is so
clear-cut. It would also be interesting to see how this hypothesis
gels with other data, such as pedal phalangeal proportions.
But if ornithuromorphs were more terrestrial/aquatic, and
enantiornithines were more more arboreal, it may explain why
ornithuromorphs were more prone to becoming flightless during the
Cretaceous (_Patagopteryx_, _Gargantuavis_, hesperornithiforms). So
far, AFAIK there's only enantiornithine that's thought to have been
flightless (_Elsornis_), and even that's highly uncertain.
BTW, this study features the name _Bellulornis_ - the proposed
replacement name for the preoccupied _Bellulia_, named earlier by Wang
et al. (2016). Consequently, this paper by Wang & Lloyd (2016) may be
the first official publication to mention _Bellulornis_; the name has
appeared in an IVPP press release (as well as multiple internet
sources), but AFAIK there's been no formal correction (with the new
name) published yet.
On Thu, Apr 7, 2016 at 1:14 AM, Ben Creisler <firstname.lastname@example.org> wrote:
> Ben Creisler
> A new paper:
> Min Wang & Graeme T. Lloyd (2016)
> Rates of morphological evolution are heterogeneous in Early Cretaceous
> Proceedings of the Royal Society B 283(1828): 20160214
> DOI: 10.1098/rspb.2016.0214
> http: // rspb.royalsocietypublishing.org/content/283/1828/20160214
> The Early Cretaceous is a critical interval in the early history of birds.
> Exceptional fossils indicate that important evolutionary novelties such as a
> pygostyle and a keeled sternum had already arisen in Early Cretaceous taxa,
> bridging much of the morphological gap between Archaeopteryx and crown
> birds. However, detailed features of basal bird evolution remain obscure
> because of both the small sample of fossil taxa previously considered and a
> lack of quantitative studies assessing rates of morphological evolution.
> Here we apply a recently available phylogenetic method and associated
> sensitivity tests to a large data matrix of morphological characters to
> quantify rates of morphological evolution in Early Cretaceous birds. Our
> results reveal that although rates were highly heterogeneous between
> different Early Cretaceous avian lineages, consistent patterns of
> significantly high or low rates were harder to pinpoint. Nevertheless,
> evidence for accelerated evolutionary rates is strongest at the point when
> Ornithuromorpha (the clade comprises all extant birds and descendants from
> their most recent common ancestors) split from Enantiornithes (a diverse
> clade that went extinct at the end-Cretaceous), consistent with the
> hypothesis that this key split opened up new niches and ultimately led to
> greater diversity for these two dominant clades of Mesozoic birds.