[D] Parahesperornis alexi [~/~]
Describer
Martin, 1983
Time
Cretaceous Late Coniacian Santonian Campanian
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Avialae Ornithothoraces Ornithurae [Hesperonithiformes]
Fossilsite
Niobrara Chalk Formation, Kansas, US
Info
Partial skull, comple postcranium. A loon-like diving bird with long, fine feathers (feather impressions have been found).
Parahesperornis alexi, is represented by the holotype specimen KUVP 2287, which was collected by H. T. Martin from Graham Co., Kansas, in 1894. KUVP 2287 is mostly complete, partially articulated, but crushed in some areas. Williston (1898) referred the specimen to Hesperornis gracilis, but Martin (1984) recognized it as a genus distinct from Hesperornis.
A predentary bone, or an intersymphysial ossification, lying between the anterior tips of the dentaries (Martin, 1987), was reported for Hesperornis regalis (KUVP 71012) and Parahesperornis alexi (KUVP 2287), and inferred, from the shape of the mesial termination of the dentary, to be present in Ichthyornis (Martin, 1987).
Hesperornis and Parahesperornis both have streptostylic quadrates that exhibit a diarthrotic articulation between the condyle of its otic process and the corresponding cotyle on the braincase. In Hesperornis and Parahesperornis the cranio- facial bending zone is within the posterodorsal processes of the premaxilla and nasals anterior to their juncture with the frontals and dorsal to the anterior end of the mesethmoid .
Although Gingerich (1976) considered these posterodorsal processes to be too thick for bending, the processes are complete on KUVP 71012 (Hesperornis) and KUVP 2287 (Parahesperornis) and are very thin and flattened dorsoventrally as in modern prokinetic birds.
Martin, 1983
Time
Cretaceous Late Coniacian Santonian Campanian
Classification
Saurischia Theropoda Tetanurae Coelurosauria Maniraptora Avialae Ornithothoraces Ornithurae [Hesperonithiformes]
Fossilsite
Niobrara Chalk Formation, Kansas, US
Info
Partial skull, comple postcranium. A loon-like diving bird with long, fine feathers (feather impressions have been found).
Parahesperornis alexi, is represented by the holotype specimen KUVP 2287, which was collected by H. T. Martin from Graham Co., Kansas, in 1894. KUVP 2287 is mostly complete, partially articulated, but crushed in some areas. Williston (1898) referred the specimen to Hesperornis gracilis, but Martin (1984) recognized it as a genus distinct from Hesperornis.
A predentary bone, or an intersymphysial ossification, lying between the anterior tips of the dentaries (Martin, 1987), was reported for Hesperornis regalis (KUVP 71012) and Parahesperornis alexi (KUVP 2287), and inferred, from the shape of the mesial termination of the dentary, to be present in Ichthyornis (Martin, 1987).
Hesperornis and Parahesperornis both have streptostylic quadrates that exhibit a diarthrotic articulation between the condyle of its otic process and the corresponding cotyle on the braincase. In Hesperornis and Parahesperornis the cranio- facial bending zone is within the posterodorsal processes of the premaxilla and nasals anterior to their juncture with the frontals and dorsal to the anterior end of the mesethmoid .
Although Gingerich (1976) considered these posterodorsal processes to be too thick for bending, the processes are complete on KUVP 71012 (Hesperornis) and KUVP 2287 (Parahesperornis) and are very thin and flattened dorsoventrally as in modern prokinetic birds.