Chloephaga Eyton, 1838

Agnolín, Federico L., Álvarez Herrera, Gerardo P. & Tomassini, Rodrigo, 2024, Pleistocene record of Chloephaga Eyton, 1838 (Anseriformes: Anatidae) in the Argentine Pampas, with the description of a new species, Comptes Rendus Palevol 23 (18), pp. 241-255 : 243

Genus Chloephaga Eyton, 1838

REMARKS

The specimens here reported can be referred to the genus Chloephaga by having: 1) coracoid with a notch on the furcular facet and foramina behind the furcular facet (shared with Neochen and Alopochen Stejneger, 1885 [ Woolfenden 1961; Álvarez-Herrera et al. 2022]), cranially divergent impressio ligamentum acrocoracohumeralis ( Álvarez-Herrera et al. 2022), shallow triosseal canal (notably deep in other geese, such as Oressochen [ Woolfenden 1961; Álvarez-Herrera et al. 2022]), prominent lateral tubercle of the acrocoracoid (modified from Woolfenden 1961; Álvarez-Herrera et al. 2022), humeral articular surface not laterally deflected (in contrast to Oressochen ); 2) humerus with enlarged and globose humeral head ( Miller 1937), elevated internal tuberosity (this tuberosity is even larger in Oressochen [ Woolfenden 1961]), very weak capital ridge and the shaft compressed adjacent to the angle of the deltoid crest but well-rounded from there ( Worthy 2009; modified from Miller 1937), depression for the m. triceps notably broad extends far laterally and proximally, so that it is overhung by the crest of the head ( Miller 1937), distally curved humeral shaft ( Miller 1937), high elevation and flat surface for the anterior articular ligament ( Woolfenden 1961); 3) ulna with distal end having external cotyla projects farther distally than the others ( Miller 1937); 4) femur with narrowing of the popliteal excavation due to inflation of the lateral margin, resulting in a deep and narrow trough, patellar groove transversely expanded ( Miller 1937); and 5) tarsometatarsus with posterior surface proximal to the trochleae wide and flattened, trochlea II strongly medially deflected ( Miller 1937), trochlea II lies farther distal and it extends beyond the base of the external intertrochlear notch, and relatively robust shaft (the shaft measures between 7.2- 7.9% of the total length of the bone; c. 6.7% in Neochen [ Woolfenden 1961]). This combination of characters clearly distinguishes Chloephaga species from closely related taxa such as Oressochen and Neochen .