A Nearly Modern Amphibious Bird from the Early Cretaceous of Northwestern China

Abstract

Three-dimensional specimens of the volant fossil bird Gansus yumenensis from the Early Cretaceous Xiagou Formation of northwestern China demonstrate that this taxon possesses advanced anatomical features previously known only in Late Cretaceous and Cenozoic ornithuran birds. Phylogenetic analysis recovers Gansus within the Ornithurae, making it the oldest known member of the clade. The Xiagou Formation preserves the oldest known ornithuromorph-dominated avian assemblage. The anatomy of Gansus, like that of other non-neornithean (nonmodern) ornithuran birds, indicates specialization for an amphibious life-style, supporting the hypothesis that modern birds originated in aquatic or littoral niches.

Pre‐modern Birds: Avian Divergences in the Mesozoic

“…The phylogenetic analysis presented as part of this chapter places Ichthyornis as a more remote outgroup of Neornithes than Hesperornis, an unusual tree topology that differs from most previous phylogenies in which Ichthyornis and Neornithes shared a most immediate common ancestor (Chiappe, 1996;Clarke et al, 2006;You et al, 2006;Zhou et al, 2008). Known since the 19th century (Marsh, 1880), Ichthyornis is abundant in the Late Cretaceous marine sediments of the Western Interior of North America (Clarke, 2004).…”

“…In the past few years, our knowledge of basal Ornithuromorpha has been greatly improved by important discoveries from the Early Cretaceous of China (Figures 3.14-3.17) (Zhou & Zhang, 2001Clarke et al, 2006;You et al, 2006;O'Connor et al, 2010). These fossils have significantly augmented the previously limited global diversity of known basal ornithuromorphs, which included primarily incompletely known taxa such as Ambiortus dementjevi from the Early Cretaceous of Mongolia (Kurochkin, 1982(Kurochkin, , 1985, and Vorona berivotrensis from the Late Cretaceous of Madagascar (Forster et al, 1996), and the flightless, hen-sized Patagopteryx deferrariisi (Chiappe, 1995(Chiappe, , 2002b from the Late Cretaceous of Argentina.…”

“…Discoveries of more advanced ornithuromorphs include the Chinese Early Cretaceous Gansus yumenensis, known from dozens of well-preserved specimens from the Xiagou Formation, Gansu Province in China (Figure 3.17; You et al, 2006) and the long-legged Hollanda luceria (Bell et al, 2010) from the Late Cretaceous of Mongolia. Hollanda is very incomplete, known only from a hindlimb, the proportions of which are very close to those of a modern roadrunner, suggesting a cursorial lifestyle (Bell et al, 2010).…”

Low ecological disparity in Early Cretaceous birds

“…Gut contents are preserved in eight Early Cretaceous pygostylians ( plus the nearest relative of pygostylians, Jeholornis) [16 -23] and aquatic habits are inferred for the non-Jehol ornithurine Gansus based on the preservation of webbed feet [24]. Li et al…”

Introduction: Changing the Questions in Avian Paleontology

“…However, both fossils and tracks show that Mesozoic ornithurine were able to exploit aquatic and transitional shoreline habitats in which enantiornithine fossils were rare or absent. The very early ornithurine Gansus was fully aquatic (You et al, 2006), while abundant remains of the later graculavids present evidence for a wide variety of shorebird-like species in the Mid-Cretaceous.…”