![]() Their fossil record is reviewed by Olson, Mlíkovský, Ericson, Dyke, Hope, Dyke and Van Tuinen, Mayr, Kurochkin and Dyke, Livezey and Zusi, Mayr and De Pietri, Stidham and Ni, De Pietri et al. The pre-Neogene record of Anseriformes is well-documented by only a handful of well-characterized genera. Regardless, they contribute to an ever-increasing known diversity of early Anseriformes that will ultimately establish the polarity of historically disputed characters. Either way, they may be of limited usefulness for establishing minimum divergence times for timetree calibration. If instead they were stem-Anseriformes, as we believe they may have been, then they were anachronisms all the more. If the new fossils do represent stem-Anhimae, then ironically they were likely relics even in their time. The fossils described herein expose what is in fact a fairly wide representation of Anhimae-like birds in celebrated late Paleocene and early Eocene deposits of North America and Europe. The divergence of Anseres from Anhimae is the most basal among crown-Anseriformes yet, paradoxically there is to date no documented paleontological record of even stem-Anhimae until the late Oligocene or Miocene. Fossils of what are believed to be stem representatives of the suborder Anseres near or just prior to the Cretaceous–Paleogene boundary imply that the stem lineage of their sister, the Anhimae, was also present at this time. It is firmly established that the divergence of Galloanseres from Neoaves occurred in the Cretaceous. It is, in fact, so close to the divergence of screamers (suborder Anhimae) and duck-like waterfowl (suborder Anseres) as to preclude truly unqualified assignment to either subordinal clade. However, the fossil lacks many or all of the synapomorphies of modern screamers, and in many respects the fossil is as much or even more duck-like as it is screamer-like. Indeed, it has already been referenced as a screamer anecdotally. ![]() ![]() The fossil is ostensibly that of a “screamer grade” of anseriform evolution because it possesses a fowl-like bill, among other screamer-like characters. While it is far from being the oldest fossil described as anseriform, it may be the most basal member of stem- or crown-Anseriformes (i.e., the most recent common ancestor of Anhima cornuta Linnaeus, 1766 and Anas platyrhynchos Linnaeus, 1758 and all their descendants) yet discovered. Additional specimens of similar basal Anseriformes of uncertain affinities from the early Eocene of North America and Europe further complicate interpretation of character state polarity due to the mosaicism of primitive and derived characters they exhibit.Īmong the new fossils presented in this paper is the three-dimensionally preserved remains, including representative elements of nearly the entire skeleton, of an anseriform from the latest Paleocene of Wyoming. ![]() However, it exhibits a more landfowl-like bill, like that of Anhimae and unlike the spatulate bill of Anseres. is similar in some aspects of both cranial and postcranial anatomy to other well-represented early Paleogene Anseriformes and members of Anseres, such as Presbyornis Wetmore, 1926. The new fossils augment a growing collection of early Pan-Anseriformes, which in their diversity do not paint an unambiguous picture of phylogeny or character state evolution on the path to or within crown-Anseriformes. et sp., to which the others cannot be confidently assigned. fam., is erected on the basis of one of these, Anachronornis anhimops nov. Collectively, these birds appear to be representative of anseriforms near the divergence of Anhimae and Anseres, but their exact positions relative to these clades remains uncertain. We describe nearly complete skeletons of basal Anseriformes from the Latest Paleocene to the early Eocene of North America and Europe. ![]()
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