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Ueekenkcoracias tambussiae gen. et sp. nov. (1 Viewer)

Fred Ruhe

Well-known member
Federico J. Degrange, Diego Pol, Pablo Puerta & Peter Wilf, 2021

Unexpected larger distribution of Paleogene stem-rollers (Aves, Coracii): new evidence from the Eocene of Patagonia, Argentina

Scientific Reports. 11: Article number 1363. doi:10.1038/s41598-020-80479-8


Here we present the first record of a stem-Coracii outside the Holarctic region, found in the early Eocene of Patagonia at the Laguna del Hunco locality. Ueekenkcoracias tambussiae gen. et sp. nov. consists of an incomplete right hind limb that presents the following combination of characters, characteristic of Coracii: relatively short and stout tibiotarsus, poorly developed crista cnemialis cranialis, short and wide tarsometatarsus, with the tuberositas m. tibialis cranialis located medially on the shaft, and curved and stout ungual phalanges. Although the presence of a rounded and conspicuous foramen vasculare distale and the trochlea metatarsi II strongly deflected medially resemble Primobucconidae, a fossil group only found in the Eocene of Europe and North America, our phylogenetic analysis indicates the new taxon is the basalmost known Coracii. The unexpected presence of a stem-Coracii in the Eocene of South America indicates that this clade had a more widespread distribution than previously hypothesized, already extending into the Southern Hemisphere by the early Eocene. Ueekenkcoracias tambussiae represents new evidence of the increasing diversity of stem lineages of birds in the Eocene. The new material provides novel morphological data for understanding the evolutionary origin and radiation of rollers and important data for estimates of the divergence time of the group.

Free pdf: https://www.nature.com/articles/s41598-020-80479-8.pdf



Fred Ruhe

Well-known member
Systematic paleontology

Class Neornithes Linnaeus, 1758.
Subclass Neognathae Pycraft, 1900.
Clade Coracii Wetmore and Miller, 1926.
Ueekenkcoracias tambussiae gen. et sp. nov.

Etymology. The generic name is from the native Tehuelche word ueekenk, meaning “outsider” in relation to its unexpected presence in South America, and the genus name ‘Coracias’. The species name honors Claudia Patricia Tambussi, whose contributions to paleornithology in the last three decades have fostered our understanding of the diversity and evolution of fossil birds in South America.

Holotype. MPEF-PV 10991, incomplete right hind limb, preserved in two slabs as part and counterpart

Locality and horizon. Laguna del Hunco locality, quarry LH27, Huitrera Formation, early Eocene (Ypresian), ca. 52.2 Ma based on 40Ar–39Ar dates and paleomagnetic stratigraphy, Chubut Province, Argentina

Diagnosis. A large representative of stem-Coracii, with a robust femur and a stout tibiotarsus, the facies articularis medialis is strongly projected caudally, the crista cnemialis cranialis is triangular shaped, the pons supratendineus is directed latero-medially, located in the median axis of the shaft, and proximally to the condyli, on the shaft, the trochleae metatarsorum II and IV have the same distal extension, the trochlea metatarsi II is medially deflected.


Figure 1. Ueekenkcoracias tambussiae gen. et sp. nov., holotype MPEF-PV 10991. Photograph (left) and interpretative drawing (right) of slabs (a,b). ccc crista cnemialis cranialis, ccl crista cnemialis lateralis, cf crista fibularis, cl condylus lateralis, cm(f) condylus medialis (femur), cm(t) condylus medialis (tibiotarsus), fam facies articularis medialis, fid fossa infracotylaris dorsalis, fp fossa poplitea, fvd foramen vasculare distale, fvp foramina vascularia proximalia, I? metatarsi I?, II–IV trochlea metatarsi II–IV, ps pons supratendineus, se sulcus extensorius, tf trochlea fibularis, ttc tuberositas m. tibialis cranialis. Scale = 1 cm.

Figure 2. Phylogenetic relationships of Ueekenkcoracias tambussiae gen. et sp. nov. Bird silhouettes were taken from PhyloPic (PhyloPic—Free Silhouette Images of Life Forms).


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