A recent edition of National Geographic
featured an article on bird evolution by Victoria Jaggard with photographs by Robert Clark and many illustrations. Unfortunately, they relied on DNA for their cladogram, featuring an apologetic illustration of a dissimilar grebe and flamingo arising from a common stem (Fig. 2). Dissimilar taxa are never closely related in trait analysis, but DNA analysis keeps finding such pairs in birds, always with the vague hope/faith/belief that someday this will resolve itself with new transitional discoveries. According to the large reptile tree (LRT, 1206 taxa) that will never happen as both flamingos and grebes each have a long list of more similar sisters, cousins and second-cousins that intervene between these two.
When it comes to fossils
Nat Geo is still stuck in the stone age as they conflate all Solnhofen birds into a single genus, Archaeopteryx, no doubt following the advice of certain professional avian paleontologists resting on tradition and an unwillingness to test specimen-based taxa. In the LRT the many Solnhofen birds are a diverse assemblage, not a single genus.
Relying on the work of Dr. Julia Clarke,
Nat Geo nests the outgroup all living birds in the LRT, Vegavis (Figs, 3, 4), as a basal chicken/duck and beautifully illustrates it as a merganser-like taxon with short swimming legs (Fig. 3). In reality we don’t have the skull of Vegavis and the legs are quite long and slender (Fig. 4), like those of the most primitive of all living birds, tinamou-like taxa.
Regarding the K-T extinction-survival event, Jaggard wrote:
“Depending on whom you ask, smaller bodies, polar adaptations, seed-based diets, and even nest designs may have played roles in determining who lived and who died. Solving the mystery will almost certainly require exhaustive hunts for animals that lived even closer in time to the impact. Ongoing fieldwork in places like South America, New Zealand, and the frosty deserts of Antarctica already hint at fresh discoveries in the near future.”
Although Vegavis fossils seem to form a bottleneck for birds in the latest Cretaceous, the present diversity of later birds arises from early Cretaceous taxa, including a clade of toothed birds like Hangshanornis, basal chickens, like Eogranivora, and the appearance of highly derived birds, like basal penguins, shortly after the K-T extinction event. We also find Vegavis-like taxa in the Early Cretaceous.
“And richer genetic clues should flood the field in the coming years. At the China National GeneBank in Shenzhen, scientists are using faster, more precise techniques to churn out drafts of entire genomes for all living bird species by 2020. Their work should help researchers not only to understand living birds but also to match useful traits in fossil animals to those in the animals’ living descendants.”
That’s unfortunate because after testing we already know
DNA does not always work with birds. Bird workers believe in DNA, hoping that someday it will produce a tree topology in which all sister taxa will look like one another, gradually blending on adjacent branches. Unfortunately, trait analysis demonstrates that day will never come. There are just too many intervening taxa.
Please, let’s all get back to trait analysis.
I’ve shown that it can be done. DNA, at least with regard to birds, is just not working.
Jaggard V. 2018. These are the Dinosaurs that didn’t die. Nat Geo online