© The Norwegian Academy of Science and Letters • Zoologica Scripta, 31, 1, February 2002, pp105–121 105 Yeates, D. K. (2002). Relationships of extant lower Brachycera (Diptera): a quantitative syn- thesis of morphological characters. — Zoologica Scripta, 31, 105 –121. With over 80 000 described species, Brachycera represent one of the most diverse clades of organisms with a Mesozoic origin. Larvae of the majority of early lineages are detritivores or carnivores. However, Brachycera are ecologically innovative and they now employ a diverse range of feeding strategies. Brachyceran relationships have been the subject of numerous qual- itative analyses using morphological characters. These analyses are often based on characters from one or a few character systems and general agreement on relationships has been elusive. In order to understand the evolution of basal brachyceran lineages, 101 discrete morpholog- ical characters were scored and compiled into a single data set. Terminals were scored at the family level, and the data set includes characters from larvae, pupae and adults, internal and external morphology, and male and female terminalia. The results show that all infraorders of Brachycera are monophyletic, but there is little evidence for relationships between the infraorders. Stratiomyomorpha, Tabanomorpha, and Xylophagomorpha together form the sister group to Muscomorpha. Xylophagomorpha and Tabanomorpha are sister groups. Within Muscomorpha, the paraphyletic Nemestrinoidea form the two most basal lineages. There is weak evidence for the monophyly of Asiloidea, and Hilarimorphidae appear to be more closely related to Eremoneura than other muscomorphs. Apsilocephalidae, Scenopini- dae and Therevidae form a clade of Asiloidea. This phylogenetic evidence is consistent with the contemporaneous differentiation of the main brachyceran lineages in the early Jurassic. The first major radiation of Muscomorpha were asiloids and they may have diversified in response to the radiation of angiosperms in the early Cretaceous. David K. Yeates, Department of Zoology and Entomology, University of Queensland, Australia. Present address: CSIRO Division of Entomology, PO Box 1700, Canberra, ACT 2601, Australia. E-mail: david.yeates@ento.csiro.au Blackwell Science Ltd Relationships of extant lower Brachycera (Diptera): a quantitative synthesis of morphological characters DAVID K. YEATES Accepted: 29 July 2001 Introduction The dipteran suborder Brachycera is a monophyletic group, with a large number of undisputed synapomorphies from the larva and adult (Hennig 1973; Woodley 1989; Sinclair 1992; Sinclair et al. 1994; Griffiths 1996; Stuckenberg 1999). The first brachyceran fossils are known from the Lower Jurassic, and the group probably arose in the Triassic (208–245 mya) (Kovalev 1979; Woodley 1989). With over 80 000 described species, Brachycera represent one of the most diverse clades of organisms with a Mesozoic origin. Well-preserved taba- nids, nemestrinids, bombyliids and mydids have just been recovered from the Upper Jurassic of China ( Ren 1998). A number of species-rich families of the lower Brachycera diversified in the mid-Cretaceous, coincident with the radia- tion of angiosperms (Grimaldi 1999). Most brachyceran larvae inhabit moist terrestrial habitats, and their adults are more stout bodied and compact than those of the lower Diptera. While the monophyly of the four infraorders of Brachycera (Xylophagomorpha, Stratiomyomorpha, Tabanomorpha, Muscomorpha) are well established, relationships between them are not (Yeates & Wiegmann 1999). Synapomorphies for the Xylophagomorpha include some extremely distinctive features of the larvae: the elon- gate, conical, strongly sclerotized head capsule, the develop- ment of a pair of metacephalic rods from the posterior portion of the cranium, and the apex of the abdomen with a sclerotized dorsal plate surrounding the spiracles and ending in a pair of hook-like processes (Hennig 1973; Woodley 1989). Xylophagid larvae are predators of other soft-bodied invertebrates in wood or soil and adults feed on nectar and pollen. Synapomorphies of the Tabanomorpha include the apo- morphic presence of a brush on the larval mandible, larval head retractile, and adult with convex, bulbous clypeus