Branta dickeyi Miller 1924
Branta dickeyi Miller, 1924 Material. USNM PAL 641972, r carpometacarpus: proximal end with damage to trochlea carpalis, collected July 2002 (Fig. 1F). Description. A large anserine carpometacarpus with a long extensor process of the alular metacarpal that is perpendicular to the long axis of the bo...
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| Format: | Other/Unknown Material |
| Language: | unknown |
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2020
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| Online Access: | https://zenodo.org/record/3815452 https://doi.org/10.5281/zenodo.3815452 |
| Summary: | Branta dickeyi Miller, 1924 Material. USNM PAL 641972, r carpometacarpus: proximal end with damage to trochlea carpalis, collected July 2002 (Fig. 1F). Description. A large anserine carpometacarpus with a long extensor process of the alular metacarpal that is perpendicular to the long axis of the bone and narrows distinctly towards the tip. In contrast, the extensor process is shorter in Chen and Anser; and shorter and wider at the tip in Coscoroba and Cygnus. The fossil agrees well in morphology with the largest comparative skeletons of Branta canadensis but exceeds them in size (at least if skeletons of captive-reared individuals are excluded from comparisons). It is distinctly larger than other North American species of Anserinae. The extensor process resembles large individuals of B. canadensis in being long and robust. Rough-surfaced exostoses are present at the tip of the extensor process; these tend to be present in large males of B. canadensis but can also occur in other Anseriformes. Measurements. In the fossil, the maximum depth from the carpal trochlea through the extensor process is 28.6 mm. This exceeds the range for 12 modern carpometacarpi of B. canadensis measured by Emslie (1995; range 21.8-25.8) and nine measured by me (range 19.8–25.3, including two from South Dakota, within the original range of the largest subspecies of Canada Goose, B. canadensis maxima Delacour). It closely matches the measurements recorded by Emslie (1995) for two Irvingtonian fossil carpometacarpi of the fossil species Branta dickeyi, one from Florida and one from Oregon, both of which measured 28.7 mm. Remarks. The large fossil goose B. dickeyi has the osteological characteristics of Branta but is roughly the size of a Tundra Swan (C. columbianus). It has previously been reported from three disparate localities in North America: the Rancholabrean McKittrick tar seeps of California (Miller 1924), a Blancan locality in Malheur County, Oregon (Miller 1944), and an early Irvingtonian locality in Florida (Leisey Shell Pit, ... |
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