Capa & Murray: Australian Megalomma sabellid polychaetes 
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Remarks. Megalomma sp. 2 resembles most closely M. cf. 
miyukiae specimens described herein, in the development 
of the collar (with dorsal collar margins separated from 
the faecal groove), in the presence of radiolar eyes in the 
dorsalmost radioles, and in the absence of a caruncle, but 
these two species are distinguished by the shape of the collar 
margins, which end abruptly in Megalomma sp. 2, and form 
concave ends with low pockets in M. cf. miyukiae. Moreover 
ventral shields are separated from tori in this specimen, 
whereas these abut in M. cf. miyukiae. 
Results of cladistic analysis 
Two trees of 39 steps were found after performing maximum 
parsimony analyses, with consistency and retention indices 
of 0.48 and 0.67 respectively. The first most parsimonious 
tree (Fig. 13) differs from the second in the position of M. 
nechamae, being in the second hypothesis the sistergroup 
of the clade M. lanigera-M. suspiciens. 
In these two topologies the basal species include M. 
kaikourense, M. gesae Knight-Jones, 1997, M. trioculatum, 
M. bioculatum Ehlers, 1887, M. interrupta n.sp. and M. 
cf. miyukiae, considered by Knight Jones (1997) and 
subsequent authors as Group 2, although they do not form a 
monophyletic clade. These species all have dorsal margins 
not fused to faecal groove, which has been shown to be a 
homoplastic character. 
An apomorphic clade of Megalomma species, equi¬ 
valent to Knight-Jones’ Group 1, is supported by two 
synapomorphies, collar margins fused to the faecal grove 
(character 6) and the presence of pockets (character 7). 
Two clades are also nested within this; one is supported 
by the presence of dorsal collar lappets (character 8) and 
the other by the presence of narrowly hooded abdominal 
chaetae (character 14), the latter being homoplastic and of 
dubious worth as it should be checked in several species. 
The jackknife support values are lower than 37 in all the 
clades except for the clade Megalomma supported by a 100 
jk value, suggesting that more evidence for confirming these 
results is needed. 
The new species are not closely related and belong 
to different clades, denoting that there is not a common 
ancestor for the Australian species. Megalomma interrupta 
n.sp. is one of the basal species due to the plesiomorphic 
condition of collar margins not fused to the faecal groove, 
while M. phyllisae n.sp. and M. inflata n.sp. belong to the 
apomorphic Megalomma clade with dorsal collar margins 
fused to the faecal groove and presence of collar pockets. 
The two latter species belong to different groups, M. 
phyllisae n.sp. being nested with those species with dorsal 
collar lappets, and M. inflata n.sp. with those species with 
narrowly hooded abdominal chaetae. 
CM 
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