Guinot, D., Jamieson, B.G.M. and Richer de Forges, B. 1994c. Relationship of Homolidae and Dromiidae: evidence from spermatozoal ultrastructure (Crustacea, Decapoda). Acta Zoologica (Stockholm) 75, 255-267.

The homolid spermatozoon, as exemplified by Homola sp., Paromola sp. and
  Paromola petterdi, differs markedly from spermatozoa of crabs of the
  Heterotremata-Thoracotremata assemblage but agrees with the sperm of
  dromiids, in the strongly anteroposteriorly depressed acrosome
  (apomorphy?) and the capitate form of the perforatorium (a major
  synapomorphy seen nowhere else in the Crustacea). These similarities
  support inclusion of the Dromiidae and Homolidae in a single grouping, the
  Podotremata. The homolid perforatorium differs from that of dromiids in
  the autapomorphic spiked-wheel form of the anterior expansion. Homolid
  spermatozoa show nuclear arms symplesiomorphic of all investigated crabs
  (small or questionably sometimes absent in Dromiidae), and corresponding
  loss of purely microtubular arms seen in other reptants. Homolid sperm
  agree with those of dromiids (synapomorphy?), raninids, higher
  heterotremes and thoracotremes (homoplasies?) but differ from lower
  heterotremes, in lacking microtubules in the nuclear arms. A posterior
  median process of the nucleus in homolids, not seen in dromiids, is shared
  with anomurans and lower heterotremes. No features in the ultrastructure
  of homolid or dromiid sperm have been detected which associate them
  exclusively with either the Raninidae or the heterotreme and thoracotreme