[D] Graculavus anceps [~/~]
Describer
Marsh, 1872
Time
Cretaceous Late
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Avialae Ornithothoraces Ornithurae Cartinatae Ichtyornithiformes
Fossilsite
North Fork of the Smoky Hill River, Kansas, US
Fall under
Ichthyornis dispar
Info
Ichthyornis dispar (Marsh, 1872) [= Colonosaurus mudgei (Marsh, 1872) including Ichthyornis agilis (Marsh, 1873); Graculavus agilis (Marsh, 1873); Ichthyornis anceps (Marsh, 1872); Graculavus anceps (Marsh, 1872); Ichthyornis victor (Marsh, 1876); Ichthyornis validus (Marsh, 1880); Ichthyornis antecessor (Wetmore, 1962); Plegadornis antecessor (Wetmore, 1962); Angelinornis antecessor (Wetmore, 1962)
Graculavus anceps (Marsh, 1872)was named several months before Ichthyornis dispar (Marsh, 1872)and was later referred to Ichthyornis (Marsh, 1880). Graculavus anceps is not the name-bearer of the taxon ‘‘Graculavus’’ and, thus, the name of the species was changed to Ichthyornis anceps (Marsh, 1880).
Holotype
YPM 1208 is a poorly preserved distal end of a left carpometacarpus. Referred specimens: The only specimen referred to Ichthyornis anceps is YPM 1749 (Marsh, 1880: 124). As YPM 1749 consists only of a partial humerus and mandible that cannot be compared to the carpometacarpus holotype of Ichthyornis anceps, this referral is considered baseless.
Locality and horizon
Marsh (1872a) indicated that the holotype was collected on the North Fork of the Smoky Hill River. Marsh (1880: 198) later specified that he collected the holotype in 1870 on the North Fork ‘‘about twelve miles east of Fort Wallace, Kansas.’’ Bardack (1965) gave its provenance as Section 11 or 13, Township 13 S, Range 36 W. Again, it is unclear how this more precise information was ascertained.
YPM 1208 is badly crushed and missing most of the distal portion of metacarpal III, making this comparison meaningless. Indeed, if the anteroposterior width of the relatively undistorted midpoint of the distal end is compared instead, the specimens are nearly identical in size (3.4 mm for YPM 1208 vs. 3.5 mm for YPM 1724). The dorsal process of the holotype is broken, leading to an apparent, but artifactual, difference in the development of the anterodorsal edge of the trochlea of metacarpal II. (Clarke , 2004)