Abstract
BackgroundDuring the last decade, new Neogene fossil assemblages from South America have revealed important clues about the evolution of seabird faunas in one of the major upwelling systems of the world: the Humboldt Current. However, most of this record comes from arid Northern Chile and Southern Peru and, in consequence, our knowledge of the evolutionary history of seabirds in the temperate transitional zone is negligible. A new Late Pliocene assemblage of fossil birds from the coastal locality of Horcon in Central Chile offers a unique opportunity to fill this gap.Principal FindingsIsolated bones of a medium-sized penguin are the most abundant bird remains. Morphological and cladistic analyses reveal that these specimens represent a new species of crested penguin, Eudyptes calauina sp. nov. Eudyptes is a penguin genus that inhabit temperate and subantarctic regions and currently absent in central Chile. Additionally, a partial skeleton of a small species of cormorant and a partial tarsometatarsus of a sooty shearwater have been identified.Conclusion/SignificanceThe Horcon fossils suggest the existence of a mixed avifauna in central Chile during the Pliocene in concordance with the latitudinal thermal gradient. This resembles the current assemblages from the transitional zone, with the presence of species shared with Northern Chile and Southern Peru and a previously unrecorded penguin currently absent from the Humboldt System but present in the Magellanic region. Comparison of Pliocene seabird diversity across the Pacific coast of South America shows that the Horcon avifauna represents a distinctive assemblage linking the living faunas with the Late Miocene ones. A comparison with the fossil record near the Benguela Current (west coast of southern Africa) suggests that the thermic gradient could play an important role in the preservation of a higher diversity of cold/temperate seabirds in the Humboldt Current.
Highlights
Two well-defined stratigraphic intervals can be identified across the entire sequence
The presence of carbonized plant remains and the absence of macrofossils are characteristic of this unit
The upper unit corresponds to the main section of the sequence. The lithology of this unit is characterized by layers of fine to coarse sandstone, light-colored and poorly consolidated, which are interspersed with few conglomeritic layers
Summary
Two well-defined stratigraphic intervals can be identified across the entire sequence. (iv) Presence of deep pit for ligament insertion adjacent to head on proximal surface (absent or very shallow in Pygoscelis antarcticus, P. adeliae, Madrynornis, Palaeospheniscus, Eretiscus and occasionally in Aptenodytes patagonicus). (ix) Preaxial angle weak or absent (well defined in Aptenodytes, Pygoscelis, Megadyptes, Spheniscus, Palaeospheniscus, Eretiscus and occasionally in Eudyptes).
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