64 p. : 26 cm

"A phylogeny is developed for those genera of tyrant flycatchers that historically have been treated in two unrelated groups: Hellmayr's (1927) Fluvicolinae, dominated numerically by Muscisaxicola and Knipolegus, and a major portion of Hellmayr's Myiarchinae, dominated numerically by Empidonax and Contopus. Monophyly of the assemblage is established by a configuration of the nasal septum that is shared only by the constituent genera and considered thus to be derived. Putative relatives that do not share this derived condition are excluded from this assemblage: Zimmerius, Polystictus, Mecocerculus, Onychorhynchus, Myiotriccus, Terenotriccus, Myiobius, some species of 'Myiophobus,' Nesotriccus, Colonia, Muscigralla, and Machetornis. Generic limits and relationships of the 33 genera admitted to the Empidonax assemblage are determined primarily by the morphology of the syrinx, and secondarily by nesting behavior and external morphology. Three primary lineages in the assemblage are defined by basic differences in the degree to which the A elements of the syrinx provide support for each bronchus. One of these lineages, in which there is little support for the bronchi, is dominated by Ochthoeca (including Tumbezia), and in addition includes Arundinicola, Fluvicola, Alectrurus, Silvicultrix (a new genus for the three forest species of 'Ochthoeca'), and Colorhamphus. A second lineage, in which the A elements form complete and calcified rings around the bronchi, consists of Myiophobus and the two monotypic genera Pyrrhomyias and Hirundinea. The remaining 24 genera belong to a third lineage, characterized by the presence of a plug of cartilaginous tissue just caudal to the tracheobronchial junction, and consisting of several groups whose interrelationships are unresolved. The largest of these groups consists of Muscisaxicola, Agriornis, Xolmis, Heteroxolmis (a new genus for dominicana), Myiotheretes, Cnemarchus, Polioxolmis (a new genus for rufipennis), Neoxolmis, Gubernetes, and Muscipipra. Another monophyletic group in this large lineage is dominated by Empidonax, and in addition includes Sayornis, Contopus, Mitrephanes, Xenotriccus, Cnemotriccus, Aphanotriccus, and Lathrotriccus. Knipolegus, Hymenops, Lessonia, and Pyrocephalus cluster by virtue of pronounced sexual dimorphism in their plumage. In addition, this large lineage also includes the monotypic Ochthornis and Satrapa, which have no obvious close relatives"--P. 2

Title from caption

"June 11, 1986."

Includes bibliographical references (p. 61-64)

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