Capa & Murray: Australian Megalomma sabellid polychaetes 
223 
Table 3. Matrix of fourteen morphological characters and a variety of species of 
Megalomma from all the categories proposed by Knight-Jones (1997) together with 
the species described in Australia. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 13 14 
Demonax leucaspis 
0 
— 
2 
0 
0 
1 
0 
0 
1 
0 
0 
1 ( 
3 0 
Megalomma lanigera 
1 
3 
2 
0 
1 
0 
1 
1 
0 
0 
1 
1 
1 1 
M. multioculatum 
1 
3 
0 
0 
1 
0 
1 
0 
0 
0 
0 
2 : 
1 0 
M. carunculata 
1 
1 
2 
1 
0 
1 
1 
0 
0 
1 
1 
2 : 
1 0 
M. cinctum 
1 
0 
0 
0 
0 
0 
1 
0 
0 
0 
0 
2 : 
1 0 
M. heterops 
1 
3 
1 
0 
0 
0 
1 
0 
1 
0 
0 
1 
1 0 
M. perkinsi 
1 
3 
? 
0 
0 
0 
1 
0 
0 
0 
1 
0 
1 ? 
M. gesae 
1 
0 
? 
0 
1 
1 
0 
0 
1 
0 
0 
? 
1 ? 
M. kaikourense 
1 
0 
? 
0 
0 
1 
0 
0 
2 
0 
0 
1 
1 1 
M. nechamae 
1 
3 
? 
0 
0 
0 
1 
1 
1 
0 
1 
1 
l 1 
M. cf. miyukiae 
1 
0 
1 
0 
0 
1 
0 
0 
0 
0 
1 
l : 
l 1 
M. phyllisae 
1 
3 
2 
0 
0 
0 
1 
1 
0 
0 
1 
2 : 
l 1 
M. interrupta 
1 
2 
2 
0 
1 
1 
0 
0 
0 
0 
0 
l : 
l 1 
M. lobiferum 
1 
1 
? 
1 
0 
0 
1 
0 
0 
0 
1 
1 ] 
l ? 
M. suspiciens 
1 
3 
1 
0 
1 
0 
1 
1 
1 
0 
1 
1 ] 
1 1 
M. cf. acrophthalmos 
1 
3 
2 
0 
0 
0 
1 
1 
0 
0 
1 
2 ] 
l 1 
M. trioculatum 
1 
1 
0 
0 
1 
1 
0 
0 
0 
0 
0 
1 ] 
l 1 
M. bioculatum 
1 
0 
? 
0 
1 
1 
0 
0 
0 
0 
1 
1 ] 
1 ? 
M. inflata 
1 
0 
1 
0 
1 
0 
1 
0 
0 
0 
1 
1 ] 
1 0 
M. quadrioculatum 
1 
0 
2 
1 
0 
0 
1 
1 
0 
0 
1 
0 ] 
1 1 
Discussion 
Although Megalomma has been considered a cosmopolitan 
genus (see Knight-Jones, 1997) it is not very abundant 
in benthic habitats and this is reflected in the number 
of specimens collected and recorded in ecological and 
taxonomic studies. For instance, several authors have 
described new species based on scarce material: Fitzhugh’s 
(2002) description of M. multioculatum is based on a single 
specimen, M. carunculata is described from three specimens 
(Tovar-Hernandez & Salazar-Vallejo, 2008), M. miyukiae, 
also described from three specimens (Nishi, 1998), M. 
perkinsi from two (Tovar-Hernandez & Salazar-Vallejo, 
2006), M. nechamae from seven, M. kaikourense from six, M. 
messapicum from 12, and M. gesae from ten (Knight-Jones, 
1997). Similar results have been observed after the study of 
a vast collection of sabellids from several surveys around 
Australia from which only 62 specimens of Megalomma 
have been found. This justifies the description of three 
new species even though there was insufficient material to 
document intraspecific variation in some cases. 
Results from the present study show that the genus is well- 
represented along Australian coasts, living in several habitats 
and depths, and that diversity is greater than previously 
thought, as there are at least seven species, three of them new. 
Results of cladistic analysis reveal that some of the 
features selected by Knight-Jones (1997) to establish 
groups of species are valid and gather natural groups, and 
these are the fusion of dorsal collar margins and presence 
of collar pockets. Results also illustrate that the presence of 
dorsal lappets and shape of abdominal chaetae are useful 
characters for grouping species. The fusion of dorsal collar 
margins to the faecal groove and the presence of pockets 
characterizes an apomorphic clade of Megalomma species, 
in which a clade with dorsal lappets is nested. Nevertheless, 
the number and distribution of radiolar eyes are homoplastic 
characters varying substantially in the Megalomma radiation 
and therefore are not suitable for classification. 
Conclusions 
After examination of specimens collected during many 
surveys around the Australian coast and housed in the 
three main Australian museum collections (AM, MV and 
MAGNT), we have documented the presence of the genus 
Megalomma in this continent, and have found it to exhibit 
high diversity, albeit in low numbers. These findings are 
similar to previous studies in other geographic areas. 
The total number of Megalomma species before the 
present study was 31 and is now increased to 34. 
We found in this study that intraspecific morphological 
variation may be high and affects several features previously 
considered as diagnostic. 
A worldwide revision of the genus is needed in order to 
clarify some issues partially commented on in this study. 
