A new book by Gerald Mayr, covering both pre-modern and crown-group fossil birds, is coming out this November:
Systematic revision of Bathornis grallator by the same author:
Mayr G 2016 Osteology and phylogenetic afnities of the middle Eocene North American Bathornis grallator—one of the
best represented, albeit least known Paleogene cariamiform birds (seriemas and allies). J Paleont doi:10.1017/jpa.2016.45
Bathornis (“Neocathartes”) grallator (Wetmore, 1944) from the middle Eocene of Wyoming is based on
a partial skeleton, which is the most substantial record of the North American Bathornithidae and one of the most
complete fossils of a Paleogene stem group representative of the Cariamiformes. So far, however, an assessment of
the evolutionary significance of this important fossil has been hampered by the limited published osteological data.
Moreover, cariamiform affinities of B. grallator and its true “genus”-level identity were recognized after the last
comprehensive revision of the Bathornithidae, and some of its features were incorrectly portrayed in the original
description. Here, the B. grallator holotype is restudied and the taxonomic composition and phylogenetic affinities
of bathornithids are revised. It is suggested to restrict Bathornithidae to the taxon Bathornis, from which the putative
bathornithid Paracrax differs in numerous features, with even cariamiform affinities of this latter taxon not having been
established beyond doubt. B. grallator was a flightless bird and has recently been hypothesized to be the sister taxon of
the likewise flightless South American Phorusrhacidae. The present analysis, however, supports a position outside a
clade including Phorusrhacidae and Cariamidae (the cariamiform crown clade). Owing to their terrestrial way of living,
Cariamiformes appear to have been prone to a loss of flight capabilities. B. grallator shows close similarities to
a flightless cariamiform bird from the Paleogene of Europe, but the phylogenetic significance of this resemblance is
difficult to assess owing to the limited material known of the latter species.
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David Černý