Bell and Chiappe 2020
provide additional insight and valuable photos of Parahesperornis alexi (Martin 1984; Fig. 1; Late Cretaceous ~90 mya) a smaller sister/ancestor to Hesperornis (Fig. 1) with more plesiomorphic traits.
According to Bell and Chiappe, “The Hesperornithiformes constitute the first known avian lineage to secondarily lose flight in exchange for the evolution of a highly derived foot-propelled diving lifestyle, thus representing the first lineage of truly aquatic birds. First unearthed in the 19th century, and today known from numerous Late Cretaceous (Cenomanian-Maastrichtian) sites distributed across the northern hemisphere, these toothed birds have become icons of early avian evolution.”
Bell and Chiappe and the Large Reptile Tree (LRT, 1694+ taxa, illustrated in figure 3) are in broad agreement regarding the phylogenetic nesting of Parahesperornis (Fig. 2). Unfortunately, Bell and Chiappe don’t include enough taxa to understand the nesting of toothed birds within the clade of toothless birds, as recovered by the LRT (Fig. 3).
And what the heck
are Gallus, the chicken, and Anas, the duck, doing in figure 2 nesting together? They are not related to one another in the LRT, but… (and here’s the key)… absent ANY pertinent transitional taxa, figure 2 is actually correct, a match with the LRT. Taxon exclusion delivers this oversimplified and misinforming cladogram (Fig. 2). More taxa, not more characters, makes a cladogram more and more accurate.
Bell A and Chiappe LM 2020. Anatomy of Parahesperornis: Evolutionary Mosaicism
in the Cretaceous Hesperornithiformes (Aves). Life 2020, 10, 62; doi:10.3390/life10050062
Marsh, OC 1880. Odontornithes, a Monograph on the Extinct Toothed Birds of North America. Government Printing Office, Washington DC.
Martin L 1984. A new Hesperornithid and the relationships of the Mesozoic birds. Transactions of the Kansas Academy of Science 87:141-150.