The Fossil Record and Evolution of Mousebirds (Aves: Coliiformes)

Abstract

Recent mousebirds are the smallest of the living neognathous bird orders -just two genera comprising six species. Understanding the evolutionary dynamics of this avian lineage is important because these birds occupy a critical position within Neoaves and can be used as a model for patterns of morphological diversification in other taxa. We present a review of all known fossil mousebirds (Aves: Coliiformes), which formed a diverse assemblage in the Paleogene (65-23.8 ma). We also present a new phylogenetic analysis including the living and fossil representatives of the order, on the basis of a larger character ⁄ taxon matrix. This analysis suggests that the Lower Eocene Eocolius is the most basal member of clade Coliiformes, while the Lower-Middle Eocene Sandcoleidae form a basal clade with respect to all other known coliiforms. We show that the Eocene taxon Chascacocolius is the sister group of the crown Coliidae, and that the Middle Eocene taxon Selmes is basal to a clade comprising Chascacocolius and Coliidae. On the basis of this phylogenetic analysis, we propose a new classification for the order Coliiformes including two new families, Chascacocoliidae and Selmeidae. For all families (clades) of mousebirds we provide descriptive osteological diagnoses and discuss a number of functional considerations related to the evolution of their hindlimbs; these considerations can be extended across all extant and fossil perching birds because we show that the hindlimb morphology of Coliiformes is strongly related to their lifestyle, as reflected in their evolutionary history.

Late Oligocene mousebird converges on parrots in skull morphology

“…These stem group Coliiformes were morphologically very diverse and adapted to different locomotory modes and feeding niches. The rather short‐legged species of the Sandcoleidae had a generalized thrush‐like beak and may have been adapted to trunk‐climbing (Houde & Olson , Zelenkov & Dyke ), whereas Chascacocolius was a specialized frugivore with gaping adaptations and a bill‐shape similar to that of some New World blackbirds (Icteridae; Houde & Olson , Mayr ), Celericolius exhibited much longer wings than extant mousebirds, allowing for a more sustained flight in open areas (Ksepka & Clarke ) and the enigmatic Masillacolius had very long legs and presumably fully pamprodactyl feet, with the hindtoe permanently directed forwards (Mayr & Peters ).…”

A new specimen of the Early Eocene Masillacolius brevidactylus and its implications for the evolution of feeding specializations in mousebirds (Coliiformes)

“…Previous analyses congruently recovered Selmes as the sister taxon of a clade including all other nonsandcoleid Coliiformes (Ksepka and Clarke, 2010;Mayr, 2013;Mayr and Mourer-Chauviré, 2004;Zelenkov and Dyke, 2008). The analyses of Zelenkov and Dyke (2008) and Ksepka and Clarke (2010) further suggested that Chascacocolius branches next, and that Masillacolius and all other more modern-type Coliiformes form a clade. In the analysis of Mayr (2013), by contrast, the interrelationships of Chascacocolius and Masillacolius were poorly resolved, and Chascacocolius, Masillacolius, and Celericolius were recovered in a polytomy at the base of a clade, which includes all coliiform taxa to the exclusion of sandcoleids and Selmes.…”

“…However, their recognition in Oligocolius already raised the question whether these processes may be plesiomorphic for a coliiform subclade, which also includes the crown group representatives (Mayr, 2013). Previous analyses congruently recovered Selmes as the sister taxon of a clade including all other nonsandcoleid Coliiformes (Ksepka and Clarke, 2010;Mayr, 2013;Mayr and Mourer-Chauviré, 2004;Zelenkov and Dyke, 2008). The analyses of Zelenkov and Dyke (2008) and Ksepka and Clarke (2010) further suggested that Chascacocolius branches next, and that Masillacolius and all other more modern-type Coliiformes form a clade.…”

“…If Selmes, Chascacocolius, and Masillacolius are indeed successive sister taxa of a clade including more moderntype Coliiformes (Ksepka and Clarke, 2010;Zelenkov and Dyke, 2008), elongated, blade-like retroarticular processes are likely to be an apomorphy of a clade including Chascacocolius, Masillacolius, Oligocolius, and crown group Coliiformes to the exclusion of Selmes and sandcoleids. Long retroarticular processes must then have secondarily become shortened in the lineage leading to the crown group, a scenario that gains some support from the fact that extant Coliiformes exhibit incipient retroarticular processes, which may represent vestiges of longer ones (Fig.…”

Phylogenetically vetted and stratigraphically constrained fossil calibrations within Aves

“…Phylogenetic Justification. Phylogenetic analysis of morphological data Zelenkov and Dyke, 2008;Clarke, 2009, 2010c). Analyses utilizing a composite Sandcoleidae with scorings from Sandcoleus and several related taxa also support placing Sandcoleus copiosus along the mousebird stem lineage Mayr, 2005d).…”