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Fossil record of Opisthocomiformes
I think that the following paper has not been posted on this list yet, but
might be of interest:
Gerald Mayr, Herculano Alvarenga and Cécile Mourer-Chauviré (2011):
Out of Africa: Fossils shed light on the origin of the hoatzin, an iconic
Neotropic bird. Naturwissenschaften. DOI: 10.1007/s00114-011-0849-1
We describe the earliest fossils of the enigmatic avian taxon
Opisthocomiformes (hoatzins) from the Oligo-Miocene (22–24 mya) of Brazil. The
bones, a humerus, scapula and coracoid, closely resemble those of the extant
hoatzin, Opisthocomus hoazin. The very similar osteology of the pectoral
girdle in the new Brazilian fossil compared to the extant O. hoazin, in which
it reflects peculiar feeding adaptations, may indicate that hoatzins had
already evolved their highly specialized feeding behavior by the mid-Cenozoic.
We further show that Namibiavis senutae from the early Miocene of Namibia is
another, previously misclassified representative of Opisthocomiformes, which
documents that the extant Neotropic distribution of hoatzins is relictual.
Because of the weak flight capabilities of hoatzins, their occurrence on both
sides of the South Atlantic is of particular biogeographic interest. We detail
that this distribution pattern is best explained by dispersal from Africa to
South America, and that Opisthocomiformes provide the first example of
transatlantic rafting among birds.