Perching bird osteology, especially of the limb bones, is rather diagnostic.[7] However, the early fossil record is poor because the first Passeriformes were apparently on the small side of the present size range, and their delicate bones did not preserve well. QM specimens F20688 (carpometacarpus) and F24685 (tibiotarsus) from Murgon, Queensland are fossil bone fragments clearly recognizable as passeriform; they represent two species of approximately 10 and 20 cm in overall length and prove that some 55 mya, barely into the Early Eocene, early perching birds were recognizably distinct.[8]
Male Superb Lyrebird (Menura novaehollandiae). This very primitive songbird shows strong sexual dimorphism, with a peculiarly apomorphic display plumage in males.
A quite similar group, the Zygodactylidae (named for their zygodactylous approach to perching) independently arose at much the same time – and possibly from closely related ancestors – in the landmasses bordering the North Atlantic, which at that time was only some two-thirds of its present width.
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Subject: Earliest passerines 
Tue Jan 04, 2011 6:32 pm
