Evolution and systematics

Lyrebirds probably originated in the Antarctic beech (Nothofagus brassii) forests and subtropical rainforests that covered much of Australia at the beginning of the Tertiary period. An early Miocene fossil species, Menura tyawanoides, has been described from Riversleigh in northwestern Queensland about 1,000 mi (1,700 km) from the northern limit of lyrebird distribution.

The open-floored nature of the beech forests (as can still be seen in New Zealand) was conducive to the evolution of visual courtship displays. The dense undergrowth of the wet sclerophyll forests and subtropical rainforests which replaced the beech forests probably necessitated the development of elaborate vocal displays.

When first discovered, the superb lyrebird was called a "native pheasant" and regarded as Gallinaceous, but it is now accepted that lyrebirds belong in the Passeriformes, and that their nearest relatives are the scrub-birds (Atrichornis). As of 2001 there was no unequivocal evidence linking the lyrebirds and scrub-birds to any other passerines. Proposed relationships with the bowerbirds (Ptilonorhynchidae) or with the tapaculos (Rhinocryptidae) have not been accepted.

The Records of the Australian Museum provide a detailed historical account of the systematics of the lyrebirds and scrub-birds. A meticulously planned series of studies on a single noisy scrub-bird specimen filled the 143 pages of that monograph. W. J. Bock and M. H. Clench summarize the research and conclusions reached. They accept that "the scrub-birds and lyrebirds form a monophyletic group of unknown affinities within the Oscines." They do not agree that the two genera form a single family as proposed on somewhat tenuous DNA hybridization grounds, and place them in separate families within a superfamily, the Menuroidea.

As of 2001, the most recent treatise on the systematics of Australian birds is The Directory of Australian Birds, published in 1999. The authors, R. Schodde and I. J. Mason, retain the two families, and recognize two species of lyrebirds, one with three subspecies.

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