A new zygodactylid species indicates the persistence of stem passerines into the early Oligocene in North America

The lake deposits of the informal Ruby Paper Shale unit, part of the Renova Formation of Montana, have yielded abundant plant fossils that document Late Eocene - Early Oligocene global cooling in western North America. A nearly complete small bird with feather impressions was recovered from this uni...

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Bibliographic Details
Published in:BMC ecology and evolution 2019-01, Vol.19 (1), p.3-3, Article 3
Main Authors: Hieronymus, Tobin L, Waugh, David A, Clarke, Julia A
Format: Article
Language:English
Subjects:
Animals
Birds
Body Size
Cooling
Creeks & streams
Eocene
Extremities - anatomy & histology
Feathers - anatomy & histology
Fossils
Geography
Global cooling
Lake sediments
Miocene
Museums
New records
New species
North America
Oligocene
Oligocene Epoch
Paleobiogeography
Paleogene
Paleogene period
Paleontology
Passeriformes
Passeriformes - classification
Phylogenetics
Phylogeny
Piciformes
Plant fossils
Range extension
Shale
Skull - anatomy & histology
Species Specificity
Spine - anatomy & histology
Taxa
Time Factors
Zygodactylidae
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Summary:The lake deposits of the informal Ruby Paper Shale unit, part of the Renova Formation of Montana, have yielded abundant plant fossils that document Late Eocene - Early Oligocene global cooling in western North America. A nearly complete small bird with feather impressions was recovered from this unit in in 1959, but has only been informally mentioned. Here we describe this fossil and identify it as a new species of Zygodactylus, a stem lineage passerine with a zygodactyl foot. The new taxon shows morphological traits that are convergent on crown Passeriformes, including an elongate hallux, reduced body size, and a comparative shortening of proximal limb elements. The fossil documents the persistence of this lineage into the earliest Oligocene (~ 33 Ma) in North America. It is the latest occurring North American species of a group that persists in Europe until the Miocene. Eocene-Oligocene global cooling is known to have significantly remodeled both Palearctic and Nearctic mammal faunas but its impact on related avifaunas has remained poorly understood. The geographic and temporal range expansion provided by the new taxon together with avian other taxa with limited fossil records suggests a similar pattern of retraction in North America followed by Europe.
ISSN:1471-2148
1471-2148
2730-7182
DOI:10.1186/s12862-018-1319-6