The evolutionary radiation of modern birds: systematics and patterns of diversification

Abstract

The timing of the evolutionary radiation of the modern, or neornithine, birds is controversial. The fossil record has indicated that the radiation occurred mainly in the aftermath of the Cretaceous–Tertiary (KT) extinction event. However, recent estimates of lineage divergence times calculated from molecular data have instead indicated that most of the major clades of modern birds originated in the Cretaceous. Because the known Mesozoic fossil record of modern birds is poor, fossils from the early Tertiary provide the first opportunity to document the pattern of the radiation. The limited phylogenetic hypotheses produced to date and including this post‐KT fossil material suggest that only some of the ‘more basal’ clades of modern birds were, most likely, present during the Mesozoic Era, and that the radiation of the ‘more derived’ landbird group of clades occurred in the early Tertiary. Copyright © 2001 John Wiley & Sons, Ltd.

The Utility of Fossil Taxa and the Evolution of Modern Birds: Commentary and Analysis

“…The extension of the strigiform confidence interval into the late Cretaceous supports Mayr & Clarke's (2003) evaluation of the Strigiformes. Regardless of this phylogenetic uncertainty, the results of the gap analysis support the hypothesis that the basal orders of neornithine birds and a number of basal neoavian orders diverged in the Cretaceous (Dyke, 2001).…”

“…The results of our gap analysis do, however, support the hypothesis that the basal lineages of neornithine birds and a number of basal neoavian lineages diverged in the Cretaceous with the remaining lineages diversifying in the Tertiary (Dyke, 2001). The known fossil records of the Anseriformes (Hope, 2002;Clarke et al, 2005) and Procellariiformes (Hope, 2002) already extend into the Late Cretaceous and, with the confidence intervals included, extend as far as 76 Ma (still in the Late Cretaceous).…”

Mitochondrial and Nuclear DNA Sequences Support a Cretaceous Origin of Columbiformes and a Dispersal-Driven Radiation in the Paleogene

“…Avian fossil evidence supports these molecular time estimates by clearly indicating that Palaeognathae and Galloanserae (Anseriformes and Galliformes) were already independent lineages in the Cretaceous (e.g., Clarke et al, 2005;Livezey, 1997). Some lineages within Neoaves, which is the sister group to Galloanserae, may also have been present in the Cretaceous, although the fossil record is too scanty and fragmentary to be unambiguously attributed to specific modern Neoaves (Cracraft, 2001;Dyke, 2001;Padian and Chiappe, 1998). Furthermore, the trans-Antarctic distributional pattern of Columbiformes and several other groups of birds (e.g., Neotropical and Australasian parrots, cracids and megapodes, and Apodiformes and Caprimulgiformes) suggest a Cretaceous age for these clades that became isolated in South America and Australia with the breakup of Gondwanaland and glaciation of Antarctica (Cracraft, 2001).…”

Forelimb proportions and the evolutionary radiation of Neornithes

“…Enantiornithidae and Confuciusornithidae) were certainly present that had similar wing proportions (BI Ͻ 1) to 'higher' modern clades (Rayner & Dyke 2002). Perhaps the absence of 'higher' modern bird clade fossils from the Mesozoic (Dyke 2001) is as a result of the occupation of niches for fast and manoeuvrable fliers (BI Ͻ 1; Rayner & Dyke 2002) by other, already abundant and morphologically diverse taxa, such as the enantiornithine birds. Extinction of confuciusornithine and enantiornithine lineages prior to the Cretaceous-Tertiary boundary may have vacated niches, which were subsequently filled by the radiation of Neornithes during the Palaeocene and Eocene.…”