Avian evolution, Gondwana biogeography and the Cretaceous–Tertiary mass extinction event

Abstract

The fossil record has been used to support the origin and radiation of modern birds (Neornithes) in Laurasia after the Cretaceous-Tertiary mass extinction event, whereas molecular clocks have suggested a Cretaceous origin for most avian orders. These alternative views of neornithine evolution are examined using an independent set of evidence, namely phylogenetic relationships and historical biogeography. Pylogenetic relationships of basal lineages of neornithines, including ratite birds and their allies (Palaleocognathae), galliforms and anseriforms (Galloanserae), as well as lineages of the more advanced Neoves (Gruiformes, (Capimulgiformes, Passeriformes and others) demonstrate pervasive trans-Antarctic distribution patterns. The temporal history of the neornithines can be inferred from fossil taxa and the ages of vicariance events, and along with their biogeographical patterns, leads to the conclusion that neornithines arose in Gondwana prior to the Cretaceous Tertiary extinction event.

A re-evaluation of sperm ultrastructure in the emu, Dromaius novaehollandiae

“…Whereas the broad morphological features of emu sperm outlined above would appear to add credence to the general view that the ratites, together with the tinamous, form a monophyletic group at the base of the avian phylogenetic tree [51][52][53], it is also clear that emu sperm are distinctly different from those of the ostrich, rhea and tinamou which together share morphological affinities [12][13][14]18,26,36,45]. This observation may lend some support to the alternate view [54] that the Australasian ratites represent a separate clade that developed independently from flightless ancestors.…”

Multiple nuclear genes and retroposons support vicariance and dispersal of the palaeognaths, and an Early Cretaceous origin of modern birds

“…Despite the use of widely accepted fossil calibrations, a gap persists between the age of the oldest crown group fossils and molecular estimates of the age of their most recent common ancestor (MRCA). However, Neornithes have been posited to have originated in the Southern Hemisphere [45], a region less sampled for fossils than the Northern Hemisphere, and perhaps where exposures with fossils of greater antiquity may yet be discovered to bridge the gap. Additionally, a recent assessment of the poor quality and patchy regional sampling of the fossil record in the Late Cretaceous suggested that the presence of neornithine lineages at this time cannot be refuted based on current evidence [46].…”

New Caledonia: a very old Darwinian island?

“…The most famous is the endemic Amborella trichopoda, the sole member of the Amborellaceae and the sister group of all other flowering plants (Mathews & Donoghue 1999;Parkinson et al 1999;Qiu et al 1999;Soltis et al 1999). Another remarkable example is the emblematic flightless bird, the kagu (Rhynochetos jubatus), the closest relatives of which occur in New Zealand and South America (Cracraft 2000;Fain & Houde 2004). A further example is the New Caledonian subfamily Troglosironidae (Opiliones), which is the sister group of taxa from South America and West Africa and only distantly related to Australian and the New Zealand taxa (Boyer et al 2007).…”