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Field & Hsiang, 2018.
bird images by International Touraco Society
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Abstract
Background:
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. However, palaeontological analyses reveal that many avian crown clades with restricted extant distributions had stem group relatives in very different parts of the world.
Results:
Our 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.
Conclusions:
In 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.
Keywords: Biogeography, Palaeontology, Turaco, Musophagidae, Phylogeny, Fossils, Gondwana, Dispersal, Otidimorphae, Macroevolution
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| Fig. 1 Skeletal morphology of total clade musophagids. (a) Complete skeleton of Foro panarium holotype USNM 336261. Scale bar equals 10 cm. (b) 3-dimensional CT rendering of the pectoral region of Ross’s Turaco (Musophaga rossae) GCO 1142 (Georgia College Ornithology, Georgia College and State University, Milledgeville, GA). LF – left ramus of furcula, RC – right coracoid, RF – right ramus of furcula, S – sternum. 153:1 denotes unfused midline of furcula, which optimizes as an unambiguous synapomorphy of a Foro + Musophagidae clade. (c) Pectoral region of F. panarium. LH – left humerus, RS – right scapula. (d) Cranial region of USNM 336261. 50:1 processus costales of axis absent. 152:1 bill short and stout with broad processus maxillaris of the os nasale. (e) Distal end of right leg of USNM 336261. 109:0 – trochlea metatarsi IV without large trochlea accessoria. 106:0 tendon of musculus flexor hallucis longus not enclosed in bony canal |
Daniel J. Field and Allison Y. Hsiang. 2018. A North American Stem Turaco, and the Complex Biogeographic History of Modern Birds. BMC Evolutionary Biology. 18:102. DOI: 10.1186/s12862-018-1212-3
