Topic
Polarornis
About: Polarornis is a research topic. Over the lifetime, 3 publications have been published within this topic receiving 27 citations.
Papers
TL;DR: Gaviiformes in the Southern Hemisphere during the Upper Cretaceous-lower Eocene times is consistent with recent phylogenetic proposals relating this group to Sphenisciformes and Procellariiformes, birds already recorded in Antarctica as discussed by the authors.
Abstract: The new remains of Gaviiformes collected from the Maastrichtian Sandwich Bluff Member (Lopez de Bertodano Formation in Vega Island), the Maastrichtian Klb 9 (Lopez de Bertodano Formation in Seymour Island), the Maastrichtian Snow Hill Formation (Vega Island), and the Ypresian Submeseta Formation (Seymour Island), Antarctica, are described. A specialized foot-propelled diving morphology is already present in the Antarctic Polarornis gregorii, the Chilean Neogaeornis wetzelli and the new specimens here reported, suggesting that such diving skills were developed at least since the Upper Cretaceous. The occurrence of Gaviiformes in the Southern Hemisphere during the Upper Cretaceous–lower Eocene times is consistent with recent phylogenetic proposals relating this group to Sphenisciformes and Procellariiformes, birds already recorded in Antarctica. The fossil record also supports the idea that the hemisphere displacement observed in Gaviiformes could be a response to increasing competition for resources with Sphenisciformes. The phylogenetic proximity of penguins and loons plus their similar trophic behavior, suggest that competitive exclusion could have triggered the gaviiform migration to the Northern Hemisphere and explain their extinction from Southern continents.
TL;DR: The results of the phylogenetic analysis suggest that A. capelambensis would be placed inside the Ornithuromorpha, and probably nested within the Ornithsurae, which would make it the geologically oldest bird described from Antarctica.
TL;DR: Comparison of characters that may be assessed in this femur with those of avian taxa scored in published character matrices refutes the inclusion of SDSM 78247 within Cariamiformes and supports its assignment to a new, as-yet unnamed large-bodied species within the genus Vegavis, and therefore its referral to a clade of semiaquatic anseriforms.
Abstract: In 2006, a partial avian femur (South Dakota School of Mines and Technology (SDSM) 78247) from the Upper Cretaceous (Maastrichtian) Sandwich Bluff Member of the Lopez de Bertodano Formation of Sandwich Bluff on Vega Island of the northern Antarctic Peninsula was briefly reported as that of a cariamiform-a clade that includes extant and volant South American species and many extinct flightless and cursorial species. Although other authors have since rejected this taxonomic assignment, SDSM 78247 had never been the subject of a detailed description, hindering a definitive assessment of its affinities. Here we provide the first comprehensive description, illustration, and comparative study of this specimen. Comparison of characters that may be assessed in this femur with those of avian taxa scored in published character matrices refutes the inclusion of SDSM 78247 within Cariamiformes, instead supporting its assignment to a new, as-yet unnamed large-bodied species within the genus Vegavis, and therefore its referral to a clade of semiaquatic anseriforms. Important character states diagnostic of Vegavis + Polarornis include strong craniocaudal bowing of the femoral shaft, the presence of a distinct fossa just proximal to the fibular trochlea, and the broad and flat shape of the patellar sulcus. Referral to Vegavis is based on the presence of a distinctive proximocaudal fossa and distolateral scar. This genus was previously known only from Vegavis iaai, a smaller-bodied taxon from the same locality and stratigraphic unit. Our reassignment of SDSM 78247 to Vegavis sp. removes the record of cariamiform landbirds from the Antarctic Cretaceous.
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2020 | 1 |
| 2019 | 1 |
| 2015 | 1 |