A tiny, long-legged raptor from the early Oligocene of Poland may be the earliest bird-eating diurnal bird of prey
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ORIGINAL PAPER
A tiny, long-legged raptor from the early Oligocene of Poland may be the earliest bird-eating diurnal bird of prey Gerald Mayr 1
&
Jørn H. Hurum 2
Received: 21 July 2020 / Revised: 25 September 2020 / Accepted: 28 September 2020 # The Author(s) 2020
Abstract We report a small hawk-like diurnal bird from the early Oligocene (30–31 million years ago) of Poland. Aviraptor longicrus, n. gen. et sp. is of a size comparable with the smallest extant Accipitridae. The new species is characterized by very long legs, which, together with the small size, suggest an avivorous (bird-eating) feeding behavior. Overall, the new species resembles extant sparrowhawks (Accipiter spp.) in the length proportions of the major limb bones, even though some features indicate that it convergently acquired an Accipiter-like morphology. Most specialized avivores amongst extant accipitrids belong to the taxon Accipiter and predominantly predate small forest passerines; the smallest Accipiter species also hunts hummingbirds. Occurrence of a possibly avivorous raptor in the early Oligocene of Europe is particularly notable because A. longicrus coexisted with the earliest Northern Hemispheric passerines and modern-type hummingbirds. We therefore hypothesize that the diversification of these birds towards the early Oligocene may have triggered the evolution of small-sized avivorous raptors, and the new fossil may exemplify one of the earliest examples of avian predator/prey coevolution. Keywords Accipitridae . Aves . Evolution . Fossil birds . Rupelian
Introduction Accipitrid diurnal birds of prey include 237 extant species with diverse ecological preferences and feeding habits (Thiollay 1994). Well-resolved molecular phylogenies (Lerner and Mindell 2005; Griffiths et al. 2007; Mindell et al. 2018) show that various small clades with geographically restricted distributions diverged early in the phylogeny of the Accipitridae, whereas the species-rich taxa Aquilinae (eagles and allies), Buteoninae (buzzards and Communicated by: Pamela Rasmussen Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00114-020-01703-z) contains supplementary material, which is available to authorized users. * Gerald Mayr [email protected] 1
Ornithological Section, Senckenberg Research Institute and Natural History Museum Frankfurt, Senckenberganlage 25, D-60325 Frankfurt am Main, Germany
2
Natural History Museum, University of Oslo, P.O. 1172 Blindern, 0318 Oslo, Norway
allies), and Accipitrinae (sparrowhawks, harriers, and allies) form a deeply nested clade. Diurnal birds of prey have a scant early Cenozoic (Paleogene) fossil record and most aspects of their evolutionary history therefore remain poorly known (Mayr 2009, 2017). The oldest fossil is from the early Eocene (50.5–52 million years ago [Ma]) of Belgium (Mayr and Smith 2019), but this specimen—a tarsometatarsus fragment— cannot be assigned to a particular accipitrid clade and does not provide insights into the ecology and feeding habit
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