Browsing by Author "Dyke, Gareth J."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item A new presbyornithid bird (Aves, Anseriformes) from the late Cretaceous of southern Mongolia. American Museum novitates ; no. 3386(New York, NY : American Museum of Natural History, 2002) Kurochkin, E. N. (Evgenii Nikolaevich); Dyke, Gareth J.; Karhu, Alexandr A.We describe a new large representative of the important fossil anseriform taxon Presbyornithidae from the latest Cretaceous (Maastrichtian) Nemegt Formation of southern Mongolia. This new taxon, Teviornis gobiensis, n. gen. et n. sp., is known from the associated manual portion of a right wing and the distal end of a right humerus, but is clearly diagnosable with respect to all other known representatives of the fossil Presbyornithidae. It is placed within the clades Anseriformes and Presbyornithidae, respectively, on the basis of a number of derived characters of the carpometacarpus and digits. Importantly, description of Teviornis confirms the presence of members of the neornithine clade Anseriformes ("waterfowl") in the late Cretaceous, as has been suggested previously on the basis of much less diagnostic fossil material as well as from clade divergence estimates founded on molecular sequence data. The extinct Presbyornithidae thus has a worldwide distribution and ranged in age from at least the Maastrichtian through to the uppermost Eocene.Item A new specimen of the fossil palaeognath Lithornis from the Lower Eocene of Denmark. American Museum novitates ; no. 3491(New York, NY : American Museum of Natural History, 2005) Leonard, Leona M.; Dyke, Gareth J.; Tuinen, Marcel vanPalaeognathous birds (Aves, Palaeognathae) are uncontroversially the most basal clade among modern birds (Neornithes), having been defined for more than 100 years on the basis of their palatal morphology. However, because many fossil specimens that have been described to date lack detailed skull material (especially in association with postcrania), aspects of the early evolutionary history of these birds remain unclear, and their relationships on the basis of anatomical characters are as yet unresolved. In this paper we present a new and exceptionally well-preserved specimen of the Lower Eocene fossil palaeognath Lithornis that has a remarkable three-dimensionally preserved and complete skull. New anatomical information provided by this Danish fossil leads us to suggest that a number of cranial characters previously considered diagnostic for ratites may in fact be primitive among palaeognaths. The presence of members of Lithornithidae in the Lower Eocene (earliest Tertiary) is consistent with the hypothesis that basal divergences within Palaeognathae occurred at an earlier geological time, perhaps prior to the Cretaceous-Tertiary (K-T) boundary, as has been proposed based on evidence from much less well-preserved fossil material.