In a recent publication (Ksepka et al. in press), the results of a phylogenetic analysis of extant and fossil Podicipediformes (grebes) were reported. Because the Least Grebe 'Tachybaptus' dominicus was recovered outside of the monophyletic group formed by other Tachybaptus species, Poliocephalus, and the fossil taxon Thiornis, it was proposed that the genus Limnodytes be resurrected for this species. However, it has come to our attention that this name is invalid due to being a junior homonym. Ksepka et al. (2013) incorrectly ascribed authorship of the genus name Limnodytes to Linnaeus. Linnaeus (1766) named the species dominicus, but assigned this species to Colymbus Linnaeus, 1758, a 'wastebasket' genus that has since been suppressed under the plenary powers of the ICZN (ICZN 1956, Opinion 401). The name Limnodytes was first applied to grebes by Oberholser (1974), and thus is a junior homonym of Limnodytes Duméril and Bibron, 1841, a ranid frog (currently synonymized with Hylarana Tschudi, 1838; see Frost 2013). Given the history in the ornithological literature of creating tautonymous genera when separating species first named by Linnaeus, we propose Dominicus nom. nov. as a replacement name for Limnodytes Oberholser, 1974. Colymbus dominicus Linnaeus, 1766, is the type and only known species. Dominicus can be distinguished from Tachybaptus by the absence of an accessory hypotarsal canal for the tendon of m. flexor perforatus digiti II, absence of chestnut-coloured patches on the neck and absence of a yellow 'grin patch' at the rima oris. Dominicus can further be distinguished from Tachybaptus and the extinct Thiornis by the presence of a distal notch in the rim of the condylus medialis of the tibiotarsus and from Poliocephalus by its strong, bladelike apophysis furculae and the absence of white, elongate feathers on the side of the head (Ksepka et al. 2013).
Albatrosses are among the most intensely studied groups of living birds, yet their fossil record remains sparse. Despite modern albatrosses being more abundant and widespread in the Southern Hemisphere, the vast majority of fossil albatrosses identified to date come from Northern Hemisphere localities. Here, we describe Plotornis archaeonautes sp. nov., a new albatross species from the earliest Miocene that represents the earliest record of Procellariiformes in New Zealand and the earliest uncontroversial record of the clade Pan-Diomedeidae from the Southern Hemisphere. Phylogenetic analyses support the placement of Plotornis outside of the clade uniting all extant albatrosses. The new fossil reveals that stem lineage albatrosses were widespread by the onset of the Neogene. Although the humerus of Plotornis archaeonautes exhibits a short processus supracondylaris dorsalis, this early species may have possessed at least one of the unique ossifications associated with the patagial bracing system present in modern albatrosses.
Abstract Although the long‐necked choristodere Hyphalosaurus is the most abundant tetrapod fossil in the renowned Yixian Formation fossil beds of Liaoning Province, China, the genus has only been briefly described from largely unprepared specimens. This paper provides a thorough osteological description of the type species Hyphalosaurus lingyuanensis and the con‐generic species Hyphalosaurus baitaigouensis based on the study of fossils from several research institutions in China. The diagnoses for these two species are revised based on comparison of a large sample of specimens from the type area and horizon of each of the two species. The skull, better known in H. baitaigouensis , exhibits key choristodere synapomorphies including an elongate contact between the prefrontals and posteriorly expanded supratemporal fenestrae that strongly support the placement of the highly derived hyphalosaurids within Choristodera. Both species of Hyphalosaurus share a proportionally small head, an elongate neck, a relatively unspecialized appendicular skeleton and a long, dorsoventrally heightened tail. Soft tissue preservation in several specimens provides rare insight into the integument of an extinct group. The integument of Hyphalosaurus is made up of small polygonal scales with several parasagittal rows of large, keeled, ovoid scutes. These possibly ornamental scutes bear a strong resemblance to the rows of large scutes in the monjurosuchid choristodere Monjurosuchus splendens . Observations from a variety of growth stages reveal that significant ontogenetic change in the proportions of the body and limb bones occurred in both species of Hyphalosaurus .
The total-evidence approach to divergence-time dating uses molecular and morphological data from extant and fossil species to infer phylogenetic relationships, species divergence times, and macroevolutionary parameters in a single coherent framework. Current model-based implementations of this approach lack an appropriate model for the tree describing the diversification and fossilization process and can produce estimates that lead to erroneous conclusions. We address this shortcoming by providing a total-evidence method implemented in a Bayesian framework. This approach uses a mechanistic tree prior to describe the underlying diversification process that generated the tree of extant and fossil taxa. Previous attempts to apply the total-evidence approach have used tree priors that do not account for the possibility that fossil samples may be direct ancestors of other samples. The fossilized birth-death (FBD) process explicitly models the diversification, fossilization, and sampling processes and naturally allows for sampled ancestors. This model was recently applied to estimate divergence times based on molecular data and fossil occurrence dates. We incorporate the FBD model and a model of morphological trait evolution into a Bayesian total-evidence approach to dating species phylogenies. We apply this method to extant and fossil penguins and show that the modern penguins radiated much more recently than has been previously estimated, with the basal divergence in the crown clade occurring at ~12.7 Ma and most splits leading to extant species occurring in the last 2 million years. Our results demonstrate that including stem-fossil diversity can greatly improve the estimates of the divergence times of crown taxa. The method is available in BEAST2 (v. 2.4) www.beast2.org with packages SA (v. at least 1.1.4) and morph-models (v. at least 1.0.4).
Penguins (Sphenisciformes) inhabit some of the most extreme environments on Earth. The 60+ Myr fossil record of penguins spans an interval that witnessed dramatic shifts in Cenozoic ocean temperatures and currents, indicating a long interplay between penguin evolution and environmental change. Perhaps the most celebrated example is the successful Late Cenozoic invasion of glacial environments by crown clade penguins. A major adaptation that allows penguins to forage in cold water is the humeral arterial plexus, a vascular counter-current heat exchanger (CCHE) that limits heat loss through the flipper. Fossil evidence reveals that the humeral plexus arose at least 49 Ma during a ‘Greenhouse Earth’ interval. The evolution of the CCHE is therefore unrelated to global cooling or development of polar ice sheets, but probably represents an adaptation to foraging in subsurface waters at temperate latitudes. As global climate cooled, the CCHE was key to invasion of thermally more demanding environments associated with Antarctic ice sheets.
Africa hosts a single breeding species of penguin today, yet the fossil record indicates that a diverse array of now-extinct taxa once inhabited southern African coastlines. Here, we show that the African penguin fauna had a complex history involving multiple dispersals and extinctions. Phylogenetic analyses and biogeographic reconstructions incorporating new fossil material indicate that, contrary to previous hypotheses, the four Early Pliocene African penguin species do not represent an endemic radiation or direct ancestors of the living Spheniscus demersus (blackfooted penguin). A minimum of three dispersals to Africa, probably assisted by the eastward-flowing Antarctic Circumpolar and South Atlantic currents, occurred during the Late Cenozoic. As regional sea-level fall eliminated islands and reduced offshore breeding areas during the Pliocene, all but one penguin lineage ended in extinction, resulting in today's depleted fauna.
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