Systematic and functional aspects of the locomotor system of the Scrub-birds, Atrichornis, and Lyrebirds, Menura (Passeriformes: Atrichornithidae and Menuridae)
The forelimb and hindlimb musculature was dissected in the Noisy Scrub-bird, Atrichornis clamosus (Atrichornithidae), and the Superb Lyrebird, , Menura novaehollandiae (Menuridae). The purposes of the study were to test certain phylogenetic hypotheses and to examine the locomotor specializations of the Menurae. The two families share derived myological traits and are sister groups. The structure of M. flexor perforatus digiti IV confirms that their affinities are with the oscines and not with the suboscines. The scrub-birds have the more highly derived limb morphology. The Menurae exhibit several myological conditions not shared with the Ptilonorhynchidae, other members of the 'corvid assemblage' or other passerines. They are, therefore, not similar to the bowerbirds in their limb musculature. A sister-group relationship with bowerbirds is not ruled out, however, because the peculiarities of the Menurae could have evolved after separation from a common ancestor with the bowerbirds, but the same is true for any suggested sister group. Both scrub-birds and lyrebirds are nearly flightless. , Atrichornis has reduced clavicles and greater forelimb reduction than does , Menura. In contrast, , Menura shows greater specialization in the hindlimb, which is elongated and has enlarged claws specialized for digging and grasping.