Broken gears in the avian molecular clock: new phylogenetic analyses support stem galliform status forGallinuloides wyomingensisand rallid affinities forAmitabha urbsinterdictensis

Abstract

Galliformes (landfowl) have been the focus of numerous divergence dating studies that seek a refined understanding of the early radiation of living birds. The Eocene fossil birds Amitabha urbsinterdictensis (Bridger Formation) and Gallinuloides wyomingensis (Green River Formation) have been used extensively in studies dealing with the timing of evolution in crown Galliformes. Divergence estimates from studies incorporating these fossils as calibration points suggest that multiple galliform lineages radiated in the Cretaceous and survived the Cretaceous-Tertiary mass extinction. However, the phylogenetic position of both fossils has been disputed, particularly with regard to crown or stem status. In order to resolve this debate, a new study of A. urbsinterdictensis and G. wyomingensis was undertaken. Further preparation and re-examination of the A. urbsinterdictensis holotype indicates this fossil falls outside both crown and stem Galliformes, and reveals evidence for a relationship with Rallidae (rails). In order to reassess the status of G. wyomingensis, a matrix of 120 morphological characters was constructed by revising and expanding on previous studies. Phylogenetic analyses using this matrix place G. wyomingensis basal to all crown Galliformes. Stem placement of G. wyomingensis is retained and resolution is improved in combined analyses incorporating sequence data from cytochrome b, NADH dehydrogenase subunit 2, mitochondrial control region, 12S rDNA, and nuclear ovomucoid intron G. All evidence indicates that A. urbsinterdictensis and G. wyomingensis are inappropriate internal calibration points for Galliformes and may have contributed to overestimation of divergence event ages. Though stem galliforms existed in the Cretaceous, the divergence of crown lineages in the Cretaceous remains inconclusively demonstrated. Because few galliform fossils have been evaluated phylogenetically, further investigations into the tempo of galliform evolution must await identification of proper fossil calibration points.

A new genus and species of a galliform bird from the Oligocene of Poland

“…A small galliform bird which is distinguished from members of all other avian orders by the combination of the following characters: (1) the sternum bears the spina interna that is fused with the spina externa to form the spina communis that protrudes cranially, (2) bears the foramen rostri at its base, and (3) two well pronounced cristae lateralis carinae that border the deep and wide sulcus carinae; (4) the furcula bears a very large and blade-like apophysis furculae; (5) the humerus shows second fossa pneumotricipitalis, (6) a transverse ridge at the beginning of the incisura capitis, and (7) a proximodistally short crista deltopectoralis whose ventral surface is almost perpendicular to the cranial surface of the humerus shaft. For distribution of characters (1), (2), and (6) among chosen Anseriformes and Galliformes see Ksepka (2009). According to Mayr (2000), at least characters (4) and (5) are derived within neognathous birds.…”

The first Palaeogene galliform from Africa

“…II is distinctly shorter than trochlea met. IV and is plantarly displaced (Ksepka 2009). It also differs from the Cracidae because in that family the trochleae are not splayed but situated close together (Ksepka 2009).…”

“…IV and is plantarly displaced (Ksepka 2009). It also differs from the Cracidae because in that family the trochleae are not splayed but situated close together (Ksepka 2009). It is more similar to the Megapodiidae because it is the only Recent galliform family in which the trochleae are splayed, and in which trochlea met.…”

Evolving Perceptions on the Antiquity of the Modern Avian Tree

“…Falconiformes, Gruiformes, Ratitae) but the majority of these ordinal ages signify extensive gaps in the fossil record. It is presently unclear to what extent taxon sampling (Linder et al, 2005;van Tuinen et al, 2006;Hug & Roger, 2007), fossil sampling (Hug & Roger, 2007), rate heterogeneity (Pereira & Baker, 2006a), genomic sampling (van Tuinen & Hadly, 2004), incorrect modeling of rates and substitution patterns (Brown et al, 2007;Brown et al, 2008;Svennblad, 2008), incorrect fossil constraints (Brown et al, 2007;Ksepka, 2009), or true lack of fossils are responsible for these tremendous gaps.…”