Wow, it’s been a couple months since my last post. There are a couple reasons for this. For one thing, there hadn’t been anything I really wanted to blog about, and I don’t want to force myself to write just because I feel I have to. In addition, I just completed my move to Kansas, and during that time I had neither the time nor energy to write anything. But now I’m back with a subject that’s near and dear to me; hesperornithiforms!
Last time I posted about these birds, I was outlining my intent to read as much of the scientific literature on them as I could. Now that I’ve read several of these papers, I feel I can give some more informed opinions on this amazing group. Of all the papers published on hesperornithiforms, one of the most important ones only came out last year. Written by Alyssa Bell and Luis Chiappe of the Natural History Museum of Los Angeles County and published in the Journal of Systematic Paleontology, this paper presents what is probably (at least to my knowledge) the first comprehensive phylogenetic analysis of this group. The results of this study may have some interesting ramifications for hesperornithiform taxonomy.
The biggest issues seem to come from the genus Hesperornis itself. In addition to the type species Hesperornis regalis, numerous additional species have been assigned to this genus. Many of these are based on very scrappy remains, often consisting of a single bone, usually a tarsometatarsus. When coding specimens for their analysis, Bell and Chiappe found that many of these purported species, as well as the genus Asiahesperornis, coded identically to H. regalis, and were all lumped into the same unit for the analysis. In addition, there were a few specimens assigned to H. regalis that coded slightly differently than the main H. regalis unit, and were thus used as separate units. The remaining Hesperornis units consisted of specimens assigned to their own species that also differed from H. regalis. The end result was a clear lack of resolution in the Hesperornis portion of their trees, with little indication of which specimens are most closely related to each other. While they didn’t state any hard taxonomic conclusions, the authors made it clear that more work needs to be done on the taxonomy of the various proposed species of Hesperornis.
Imagine my surprise then when, just this year, a paper came out naming yet another new species, Hesperornis lumgairi. Given the current issues with hesperornithiform taxonomy, I was immediately skeptical. While I’ve so far only skimmed through the paper, what I have seen does not inspire confidence. This is yet another species named on the basis of a tarsometatarsus, and what’s more, it’s not even complete. The authors assert that this specimen cannot be assigned to any previously named species of Hesperornis, but given the issues outlined by Bell and Chiappe (which they cite but don’t really do anything with), naming any new species, especially based on such fragmentary material, only confounds the problems associated with the taxonomy of hesperornithiforms.
Hesperornis isn’t the only taxon with issues. Bell and Chiappe also analyzed three specimens that have traditionally been assigned to Baptornis advenus. While two of these grouped with their assigned taxon, one specimen was found to be closer to Hesperornis, and in a followup paper was given the new name Fumicollis hoffmani. While the reclassification of this specimen may not seem like that big of a deal, it too may have a profound effect on our understanding of these birds. The specimen that would become the type of Fumicollis played a major role in an influential paper by Martin and Tate describing the osteology of Baptornis. With this specimen now split from Baptornis, it calls for a reexamination of other specimens attributed to this genus, as well as a reconsideration of its current diagnosis.
As you can see here, hesperornithiform taxonomy is somewhat confused at the moment. Fortunately, largely thanks to the work of Bell and Chiappe, we are getting a somewhat clearer view of the problems that need work. Hopefully they will continue on this track. There is some other work I wanted to mention, but it hasn’t been formally published yet so I decided to refrain from discussing it without the author’s consent. As for my own views, it seems likely to me that Hesperornis is severely oversplit, and it wouldn’t surprise me if most or even all species other than H. regalis are either lumped with the latter, or declared nomina dubia (that is, too fragmentary to have any taxonomic utility). I’m also interested in seeing how the identification of many Baptornis specimens is affected by the removal of a major specimen from this genus. But for now, I’ll leave it to the experts, though if I’m lucky, I may someday have a hand in sorting out these issues.