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Records of the Australian Museum (2014) Vol. 66 
Discussion 
Reappraisal of the proposed genera 
and their validity 
Sixteen genera have now been named, but not all of these have 
been accepted, either because the defining characters were not 
autapomorphic (Walker-Smith, 2001; Wells, 2007), or due 
to the fact that the type genus to the Porcellidiidae had not 
been clearly defined, resulting in a diverse assembly of very 
different species (Huys et al. , 1996). The latter problem has 
been resolved with a definitive diagnosis for Porcellidium by 
Harris (2014a), but the first difficulty has not been addressed. 
Wells (2007) objected that “... Although the ICZN neither 
precludes nor declares invalid taxa that are not in accord with 
Hennigian principles, they are now widely accepted as the 
ruling paradigms in systematics” Walker-Smith has pointed 
out that many of the genera were only defined on a unique 
combination of characters and not autapomorphies. However, 
Bodin (1997) points out that the diagnoses given “... of these 
genera are in accordance with the rules of the ICZN... ”. It is 
necessary, therefore, to reconsider the grounds on which the 
disputed genera were based. 
A careful re-examination of type material for all Australian 
and Japanese genera in the Porcellidiidae has been made to 
assess whether the unique features found were specific to 
only one species or to a closely defined group of species 
as autapomorphic characters defining a genus. The current 
data base contains detailed information on over 70 species. 
It shows certain features, such as shape of the cephalosome, 
caudal ramus, genital double-somite and structure of the male 
antennule, are extremely variable and may be useful species- 
specific characters. On the other hand, variation in a feature 
like the number of setae on the maxillule endopod, which is 
almost constant throughout the family, is more likely to be 
regarded as an autapomorphic character defining a genus. 
A number of other unique features, such as the brush pad of 
Kensakia , ventral hyaline membrane of Tectacingulum or the 
loss of terminal setae from the male P5 of Synurus are regarded 
as characters defining genera. 
The result of this re-assessment is given in Table 1 where 
apomorphic and autapomorphic characters are listed for 
each genus except Porcellidium and Acutiramus. A total of 
33 characters have been selected to define Porcellidium , all 
are present on the type species P. viride and appear to be 
plesiomorphic: none of them are considered autapomorphic. 
However, each of them are known to have a corresponding 
apomorphic state which is indicated in Table 1. 
Remarks 
Table 1 gives the main defining characters for each of 
the genera. Porcellidium is based on characters that are 
exhibited by Porcellidium viride and all species placed 
in that genus. Genera 3 to 16 are clearly defined by easily 
seen autapomorphic characters that separate them from 
Porcellidium and Acutiramus. Acutiramus is maintained 
because it is clearly excluded by the new definition of 
Porcellidium in shape of the female genital double-somite, 
caudal rami, P5 and details of the male antennule. It is 
excluded from Ravania by the presence of T3 on the caudal 
ramus and structure of the male antennule. 
The case for placing Clunia cocosensis and Geddesia 
quadrata in separate genera is not so clear for they both have 
a pentagonal caudal ramus similar in shape to Mucrorostrum 
yoroium, but not found elsewhere in the family. However, 
the three species cannot be placed together in the same genus 
because of fundamental differences in the setation of their 
maxillule. This appendage shows remarkable uniformity in 
the number of setae on endites and the endopod throughout 
the Porcellidiidae and any deviation must be considered 
an autapomorphic feature. Geddesia has six setae on the 
endopod, the typical porellidiid condition, but Mucrorostrum 
has only two setae on the endopod and an endite formula 
1-2-1. Clunia on the other hand, has only one endopod seta 
and an endite formula 2-3-1. These two unique differences in 
maxillule setation are considered autapomorphic characters 
defining Mucrorostrum and Clunia. 
An unexpected consequence of re-describing the type 
species for Porcellidium is that about half of the species 
described in the literature do not belong to that genus. 
Either they do not share all the characters of the genus or 
they possess apomorphic character states that eliminate 
them from Porcellidium and place them in other genera. Of 
the 59 species listed in the literature, eight are inadequately 
described and cannot be placed in any known genus: P. 
fulvum and P. interruptum Thomson (1882), P. tuberculatum 
Wolfenden (1905), P. affine and P. charcoti Quidor (1906), 
P. wolfendeni Brady (1910), P. scotti Pesta (1935) and P. 
malleatum Vervoort (1964). However, they may prove 
valid species when accurately redescribed. Another seven 
are synonyms for other species: P. dentatum Claus (1860), 
P. ovatum Haller (1879), P. lecanoides Claus (1889), P. 
sarsi Bocquet (1948), P. penicilliferum, Tiemann (1978), 
P. acutum and P. aoifuchidorum Harris & Iwasaki (1996, 
1997) and another three are juvenile stages: P. subrotundum 
Norman (1868), P. rotundum, and P. australe Brady (1910). 
This leaves 41 recognized species, but only 20 of these fit 
the diagnosis for Porcellidium. The remainder must be 
transferred to other genera. 
Table 2 gives a check list of the 71 species belonging to 
the Porcellidiidae recognized in the present study. It reveals 
the genus to which species rejected from Porcellidium have 
been moved, together with the original author, geographical 
distribution and the size of holotype and allotype specimens. 
Distribution of Australian Porcellidiidae 
A list of 32 described species and their recorded presence on 
the east coast of Australia is given in Fig. 14, but sampling 
has not been uniform along the whole coast. Knowledge of 
the NSW porcellidiid fauna is based on extensive collection 
at 17 stations over a period of two decades, whereas data on 
the Great Barrier Reef rests on a single sample washed from 
a mixture of seagrass (Zostera capricornia ?) and Halimedia 
sp. at Green Island, Cairns. 
Despite this, there appears to be a clear distinction 
between the species that occur in northern Queensland 
and those that are found south of the Tropic of Capricorn. 
Of the 27 species known from NSW, only four have been 
recorded from Hervey Bay, southern Queensland and only 
two of these have been collected as far south as Eden 
{Acutiramus rufolineatus and A. quinquelineatus). Two 
species, Clavigoferapacifica and Synurus ctenocheirus, are 
known from Japan, but none of the other species has been 
recorded beyond Australian shores. No New Zealand species 
has been found in Australian waters. Eight species are only 
known from single localities. 
