Avifauna of early Eocene British London Clay + Taeniolabis skull from Paleocene of Denver Basin
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Ben Creisler
May 29, 2026, 1:31:29 PM (8 days ago) May 29
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Ben Creisler
Recent Cenozoic papers:
Free pdf:
Gerald Mayr (2026)
An overview of the oldest and most comprehensive avifauna of the early Eocene British London Clay
Papers in Palaeontology 12(3): e70093
doi: https://onlinelibrary.wiley.com/doi/10.1002/spp2.70093
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70093
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/spp2.70093
Early Eocene birds from the British London Clay have been known for two centuries, but a comprehensive understanding of the avifauna of the London Clay Formation is still in its infancy. In the present study, the bird assemblage of the Walton Member is reviewed, which represents one of the oldest subdivisions of the formation. With more than 80 currently recognized species, it is one of the most comprehensive early Cenozoic avifaunas known to date. Some taxa are unknown from middle Eocene sites, while others have undergone few morphological changes over several million years, which may constitute evidence for niche conservatism in balanced ecosystems. The fossils show a high taxonomic concordance with coeval bird assemblages in North America, but the extent to which early Eocene avifaunas were similar on a global scale is unknown owing to the limited fossil record from the southern continents. The avian diversity of Walton-on-the-Naze is not evenly distributed across neornithine phylogeny, and taxa of the Telluraves predominate. Other clades that produced arboreal birds are conspicuously absent. The occurrence of stem group representatives of multiple telluravian taxa suggests an initial diversification of the clade on the northern continents, which conflicts with biogeographic scenarios derived from the extant taxa. A notable feature of the avifauna of Walton-on-the-Naze is the very small size of many species of the Telluraves and Strisores, which is attributed to the fact that these birds were at the beginning of an adaptive radiation.
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Gerald Mayr (2026)
An overview of the oldest and most comprehensive avifauna of the early Eocene British London Clay
Papers in Palaeontology 12(3): e70093
doi: https://onlinelibrary.wiley.com/doi/10.1002/spp2.70093
https://onlinelibrary.wiley.com/doi/10.1002/spp2.70093
Free pdf:
https://onlinelibrary.wiley.com/doi/epdf/10.1002/spp2.70093
Early Eocene birds from the British London Clay have been known for two centuries, but a comprehensive understanding of the avifauna of the London Clay Formation is still in its infancy. In the present study, the bird assemblage of the Walton Member is reviewed, which represents one of the oldest subdivisions of the formation. With more than 80 currently recognized species, it is one of the most comprehensive early Cenozoic avifaunas known to date. Some taxa are unknown from middle Eocene sites, while others have undergone few morphological changes over several million years, which may constitute evidence for niche conservatism in balanced ecosystems. The fossils show a high taxonomic concordance with coeval bird assemblages in North America, but the extent to which early Eocene avifaunas were similar on a global scale is unknown owing to the limited fossil record from the southern continents. The avian diversity of Walton-on-the-Naze is not evenly distributed across neornithine phylogeny, and taxa of the Telluraves predominate. Other clades that produced arboreal birds are conspicuously absent. The occurrence of stem group representatives of multiple telluravian taxa suggests an initial diversification of the clade on the northern continents, which conflicts with biogeographic scenarios derived from the extant taxa. A notable feature of the avifauna of Walton-on-the-Naze is the very small size of many species of the Telluraves and Strisores, which is attributed to the fact that these birds were at the beginning of an adaptive radiation.
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Taeniolabis simmonsae comb. nov.
David W. Krause, Lucas N. Weaver, Stephen G. B. Chester, Craig S. Scott, Ken Weissenburger, Jordan W. Crowell, Rudolph R. Hummel & Tyler R. Lyson
Taeniolabis simmonsae (Multituberculata, Taeniolabididae) from the early Paleocene of the Denver Basin, Colorado: implications for taeniolabidid taxonomy and biochronology of the Puercan North American Land Mammal Age
Journal of Mammalian Evolution 33: 28 (2026)
https://doi.org/10.1007/s10914-026-09817-3
https://link.springer.com/article/10.1007/s10914-026-09817-3
A recently discovered multituberculate skull with a nearly complete dentition from the lower Paleocene part of the Denver Formation (Corral Bluffs study area, Denver Basin, Colorado) represents a species of taeniolabidid that is smaller than Taeniolabis taoensis. We conclude that this skull, as well as an isolated upper first molar from the same study area, pertains to Kimbetopsalis simmonsae, previously known only from the Nacimiento Formation of the San Juan Basin, New Mexico. The Corral Bluffs skull includes the first lower jaw and lower dentition for the species. Based on our assessment of intraspecific variation in a large sample of T. taoensis from the Nacimiento Formation, we reevaluated all occurrences of Taeniolabis in the Western Interior of North America. We consider Kimbetopsalis a subjective junior synonym of Taeniolabis and therefore refer the species to Taeniolabis in a new combination, Taeniolabis simmonsae. Questions remain as to whether T. simmonsae is morphologically distinct from T. lamberti (Fort Union Formation, Montana). In-situ occurrences of T. simmonsae are lower than those of T. taoensis in the Corral Bluffs stratigraphic section and are in association with those of mammals characteristic of the Ectoconus/Taeniolabis taoensis Interval Zone (Pu2) of the Puercan North American Land Mammal Age, and earlier than those of mammals that characterize the Taeniolabis taoensis/Periptychus carinidens Interval Zone (Pu3). Thus, Taeniolabis, considered by some authors to be restricted to the Pu3 Interval Zone, occurs in both Pu2 and Pu3 zones, which has profound implications for early Paleocene bio- and geochronology.
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Taeniolabis simmonsae (Multituberculata, Taeniolabididae) from the early Paleocene of the Denver Basin, Colorado: implications for taeniolabidid taxonomy and biochronology of the Puercan North American Land Mammal Age
Journal of Mammalian Evolution 33: 28 (2026)
https://doi.org/10.1007/s10914-026-09817-3
https://link.springer.com/article/10.1007/s10914-026-09817-3
A recently discovered multituberculate skull with a nearly complete dentition from the lower Paleocene part of the Denver Formation (Corral Bluffs study area, Denver Basin, Colorado) represents a species of taeniolabidid that is smaller than Taeniolabis taoensis. We conclude that this skull, as well as an isolated upper first molar from the same study area, pertains to Kimbetopsalis simmonsae, previously known only from the Nacimiento Formation of the San Juan Basin, New Mexico. The Corral Bluffs skull includes the first lower jaw and lower dentition for the species. Based on our assessment of intraspecific variation in a large sample of T. taoensis from the Nacimiento Formation, we reevaluated all occurrences of Taeniolabis in the Western Interior of North America. We consider Kimbetopsalis a subjective junior synonym of Taeniolabis and therefore refer the species to Taeniolabis in a new combination, Taeniolabis simmonsae. Questions remain as to whether T. simmonsae is morphologically distinct from T. lamberti (Fort Union Formation, Montana). In-situ occurrences of T. simmonsae are lower than those of T. taoensis in the Corral Bluffs stratigraphic section and are in association with those of mammals characteristic of the Ectoconus/Taeniolabis taoensis Interval Zone (Pu2) of the Puercan North American Land Mammal Age, and earlier than those of mammals that characterize the Taeniolabis taoensis/Periptychus carinidens Interval Zone (Pu3). Thus, Taeniolabis, considered by some authors to be restricted to the Pu3 Interval Zone, occurs in both Pu2 and Pu3 zones, which has profound implications for early Paleocene bio- and geochronology.
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