46 



Medial Basivenalia moderately reduced on all margins. Anterior and posterior margins 

 isolated from surrounding sclerites. BMA broadly scaphoid; completely fused to BMP. 

 Proximal surface flat. Distal surface convex. Anterior margin concave. Proximal arch 

 short; broad; straight; planate; enlarged antero-proximally. Distal arch distinct; slender; 

 strongly convex. BMP junction with BMA discontinuous and very broad; extremely small; 

 rectangular; strongly convex to flat; distinct from brace; separated from IBP and BCu. 

 Proximal section extremely small; flat to weakly convex; very weakly distinguishable from 

 BMA. Antero-distal and postero-distal margins sharply aquiline. Median section deeply 

 concave. Distal section formed as a very large, rectangular convexity; strongly convex; 

 prominent. Distal margin deeply concave; very strongly elevated above the surrounding 

 membrane. Antero-distal and postero-distal sections continuous and equally elevated. 

 Cubital Basivenalia partially fused. Postero-proximal margin of BCuA fused with antero- 

 proximal margin of BCuP. Suture line present. BCuA larger than BCuP; ovoid to weakly 

 deltoid; strongly convex; oriented postero-distad; strongly sclerotized; lies proximal of 

 CuA. Median section concave. BCuP C-shaped; smaller than BCuA; moderately convex 

 proximally; weakly so distally; oriented postero-distad; weakly sclerotized especially 

 distally. Distal embayment very deep. - Cubitus Anterior continuous with BCuA. 



Basalare (Fig. 65) 



Head - HP lobe broad; continuous with neck; smaller than BScP lobe; very thin in cross- 

 section. Apex broadly rounded. Dorsal surface weakly curved posteriad; elevated from 

 neck; not polished. BScP lobe claviform; projects posteriad from neck. Dorsal surface 

 ovoid; convex; polished; equally elevated as the HP lobe. Ventral surface polished. - 

 Posterior Subcostal Basivenale deltoid; polished. 



Discussion 



Monophyly of the Pleocomidae is supported by the fact that all of the taxa in this family 

 share the following three apomorphic character states of the wing articulation and wing 

 base: 



1. 2Ax: the dorso-proximal lobe is strikingly small and basally extremely narrow, 



2. the subalare tendon attachment point is extremely long and narrow; 



3. 2BP: BMP is very strongly convex and extremely small. 



Pleocomidae share six apomorphic character states of the wing articulation and wing base 

 with Passalidae, Diphyllostomatidae, Lucanidae, Glaphyridae, Trogidae and 

 Bolboceratidae (Browne & Scholtz 1995; Scholtz et al.. submitted). 

 Pleocomidae have long been considered the sister group of Geotrupidae (Bolboceratini- 

 Athyreini-Lethrini, Howden 1982) based on doubtful synapomorphies (Scholtz 1990). 

 However, it has been suggested that this family may be related to Melolonthinae due to 

 the highly modified club with 4-7 annuli (Howden has subsequently favoured the latter 

 relationship over the former, pers. comm. 1991). Browne's analyses (1991a, 1993), based 

 on synapomorphic wing structure and a subsequent analysis examining all character suites 

 (Scholtz et al., submitted), supported Howden (1982). Pleocomidae and Geotrupidae have 

 similar spiracle (Ritcher 1969a,b) and eye structure (Caveney 1986). Some genitalic and 



