A North American stem turaco, and the complex biogeographic history of modern birds

Daniel J Field,Allison Y Hsiang

doi:10.1186/s12862-018-1212-3

Daniel J Field, Allison Y Hsiang

Open Access

https://doi.org/10.1186/s12862-018-1212-3

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Abstract

BackgroundEarth’s lower latitudes boast the majority of extant avian species-level and higher-order diversity, with many deeply diverging clades restricted to vestiges of Gondwana. However, palaeontological analyses reveal that many avian crown clades with restricted extant distributions had stem group relatives in very different parts of the world.ResultsOur phylogenetic analyses support the enigmatic fossil bird Foro panarium Olson 1992 from the early Eocene (Wasatchian) of Wyoming as a stem turaco (Neornithes: Pan-Musophagidae), a clade that is presently endemic to sub-Saharan Africa. Our analyses offer the first well-supported evidence for a stem musophagid (and therefore a useful fossil calibration for avian molecular divergence analyses), and reveal surprising new information on the early morphology and biogeography of this clade. Total-clade Musophagidae is identified as a potential participant in dispersal via the recently proposed ‘North American Gateway’ during the Palaeogene, and new biogeographic analyses illustrate the importance of the fossil record in revealing the complex historical biogeography of crown birds across geological timescales.ConclusionsIn the Palaeogene, total-clade Musophagidae was distributed well outside the range of crown Musophagidae in the present day. This observation is consistent with similar biogeographic observations for numerous other modern bird clades, illustrating shortcomings of historical biogeographic analyses that do not incorporate information from the avian fossil record.

Highlights

Earth’s lower latitudes boast the majority of extant avian species-level and higher-order diversity, with many deeply diverging clades restricted to vestiges of Gondwana
Such arguments, which have historically favored a vicariant Gondwanan origin for crown birds (Neornithes), have often ignored data gained from the Palaeogene fossil bird record, which has improved substantially in recent years thanks to new discoveries and diagnoses based on rigorous phylogenetic analyses [8]
Given the historical difficulty of identifying the Hoatzin’s extant sister taxon, and its strikingly unusual skeleton, an effort was made to shorten the phylogenetic branch leading to O. hoazin by including two stem opisthocomids in the phylogenetic analysis: Hoazinavis lacustris Mayr et al 2011, from the late Oligocene/early Miocene of Brazil; and Namibiavis senutae Mayr 2014, from the late early Miocene of Namibia [56, 59]

Summary

Introduction

Earth’s lower latitudes boast the majority of extant avian species-level and higher-order diversity, with many deeply diverging clades restricted to vestiges of Gondwana. South America [2,3,4] This common distributional pattern has prompted the proposal of a Gondwanan origin for living birds, a hypothesis that has been used to corroborate arguments for an ancient Mesozoic diversification of the avian crown group [5,6,7]. Phylogenetic hypotheses for many Northern Hemisphere Palaeogene bird fossils may cast doubt on the hypothesis of a Mesozoic Gondwanan origin of Neornithes, as many crown-clades with restricted extant distributions appear to have stem-group relatives in very different parts of the world

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