Records of the Western Australian Museum 17: 315-323 ( 1995 ). 
The spatangoid echinoid Schizaster (Schizaster) compactus (Koehler, 1914) 
in Western Australia 
Kenneth J. McNamara 
Department of Earth and Planetary Sciences, Western Australian Museum, Francis Street, Perth, 
Western Australia 6000 
Abstract - The spatangoid echinoid Schizaster (Schizaster) compactus (Koehler, 
1914) is recorded from Australian waters for the first time. A sample 
consisting of a juvenile and adults collected from off the Dampier 
Archipelago, Western Australia is shown to undergo significant ontogenetic 
variation in a number of parameters, notably number of pore pairs in all 
aboral ambulacra; relative size and shape of the peristome and periproct; 
relative width of ambulacrum III aborally; and relative length of the posterior 
petals. A number of morphological characters also show appreciable 
intraspecific variation, in particular the number of gonopores; position of the 
peristome; the width of the plastron; test width; and position of the apical 
system. An understanding of the degree of phenotypic variation in this 
species aids in the delimitation of species of Schizaster and in the 
characterisation of the taxa Schizaster and Paraster. 
INTRODUCTION 
On July 27, 1982 a number of large steel pipes 
destined for the North-West Shelf Gas Project was 
inadvertently sunk in about 45 m of water north of 
Dampier, Western Australia at 20°19'33.1"S, 
116°33’22.11"E. Nearly 10 months later, on May 18, 
1983, the pipes were recovered. They were found 
to be packed with soft, foraminiferal-rich silt, 
within which were living five species of 
spatangoids. In addition to 33 complete and broken 
specimens of a species of Schizaster, single 
specimens of Moira lethe Mortensen, 1930; Metalia 
sternalis (Lamarck, 1816); and Lovenia elongata 
(Gray, 1845) were found in the silt, along with three 
specimens of an undescribed species of Metalia. 
The species of Schizaster (Figure 1) is identical to 
a single specimen described by McNamara and 
Philip (1980a) from Rosemary Island in the 
Dampier Archipelago, and referred by them to 
Schizaster (Schizaster) lacunosus (Linnaeus, 1758). 
Examination of the larger population has revealed 
the species to be conspecific with a form described 
by Koehler (1914) from the Bay of Bengal and 
called by him Paraster compactus. However, in one 
character the Western Australian form differs from 
tire features described by Koehler, and that is in 
the number of gonopores. Koehler's description 
was based on only two specimens, This difference 
is not considered to be of sufficient importance to 
warrant placing the Australian form in a separate 
species, as other species of Schizaster have been 
shown to possess variable numbers of gonopores 
(McNamara and Philip 1980a). 
hr addition to describing this species from the 
eastern side of the Indian Ocean for the first time, 
the aim of this paper is to demonstrate not only the 
variability in the number of gonopores within a 
single, presumably genetically homogeneous, 
population. This feature has been used as a generic 
or subgeneric character within schizasterids. In this 
paper characters other than gonopore number are 
used to differentiate the three subgenera of 
Schizaster ( Schizaster, Paraster and Ova) and revised 
diagnoses of these subgenera given. This paper 
also aims to illustrate the extent of morphological 
variation present in other characters throughout 
ontogeny. Phenotypic variation encompasses not 
simply the morphological differences between 
adults within a population, but also differences 
that occur through the ontogenetic development. 
After all, tire adult phenotype is a product of the 
morphological variation that the individual 
undergoes throughout its ontogeny. 
It is particularly important to determine the 
degree of morphological variation present within 
species of Schizaster in order to delineate fossil taxa 
effectively. In the past many species have been 
described, particularly last century, on the basis of 
few specimens (Koehler's Paraster compactus being 
a case in point). Consequently, Lambert and Thiery 
(1925) and Kier and Lawson (1978) recorded that 
up until 1970, 275 species of Schizaster and Paraster 
had been described. Categorising the degree of 
intraspecific morphological variation within this 
northwestern Australian species of Schizaster will 
therefore provide a useful tool to further studies 
