Pillai: Serpulid polychaetes from the Australian Kimberleys 
147 
the tetraceros category. In both 
Pomatoceros and Zibrowius 
(1968) further states that if 
there are species having collar 
chaetae that are intermediate 
between the bayonet-shaped 
chaetae with a squarish boss in 
Spirobranchus and the simple 
chaetae of Pomatoceros, then the two 
genera should be united. He lists out 
similarities among the nominal genera 
Spirobranchus Blainville (including 
Pomatoceropsis Gravier, 1905 and Cono- 
pomatus Pillai, 1960), Pomatoceros Philippi, 
1844 and Pomatoleios Pixell, 1913, among 
others, with regard to many important char¬ 
acters. They include the uncini, chaetae (bearing 
in mind the discussion on the collar chaetae), 
winged opercular peduncles, the calcareous 
opercular plates, possession of an apron, and the characteristic 
blue or violet body pigmentation, which is present in 
Pomatoceros, Pomatoleios and Spirobranchus. He concludes 
that they form a natural group and that, eventually, need to 
be reclassified more closely. 
Ten Hove & Nishi (1996) state that “the differences 
between the nominal genera Pomatoceros, Pomatoleios and 
Spirobranchus are very small (if indeed existing), mainly 
lying in the collar chaetae. Absent in Pomatoleios, hooded 
(limbate) in Pomatoceros and bayonet-like with numerous 
hair-like teeth in the basal boss in Spirobranchus .” 
The three genera cannot also be satisfactorily separated 
on the basis that special collar chaetae in Spirobranchus 
are bayonet-shaped and possess a squarish boss, while 
those in Pomatoceros are capillary-like or capillaries, and 
that they are absent in Pomatoleios. It will be seen from 
descriptions of species of Spirobranchus that follow, that 
there is, in the various taxa, a complete range of special 
collar chaetae, from those in which the boss is prominently 
squarish to those in which it is reduced to various extents, 
even to capillaries. Among them is the new species Spiro¬ 
branchus zibrowii, in which the special collar chaetae, like 
those of Pomatoceros, do not possess a recognizable boss, 
but are capillaries. In Pomatoceros, the reduction of the basal 
boss of collar chaetae is complete, making them capillaries, 
except for a very narrow blade that is discernible under high 
power magnification. In the light of observations of this 
character in the various species studied below (Fig. 36), it 
is impossible to separate the nominal genus Pomatoceros 
from Spirobranchus. 
Figure 36. A-I, special collar chaetae of some species of Spiro¬ 
branchus showing a complete range in form from the “ Spirobran- 
chus- type” with a squarish boss to those lacking a boss and being 
capillary-like as in Pomatoceros triqueter. (A) S. corniculatus 
Grube, 1862. (B) S. maldivensis Pixell, 1913. (C) S. zelandicus 
n.sp. ( D ) S. murrayi n.sp. (E) S. tenhovi n.sp. (F) S. sp. 3 (G) S. 
zibrowii n.sp. (H) S. (= Pomatoleios) kraussii (Baird, 1864). (7) S. 
(- Pomatoceros) triqueter (Linnaeus, 1767). 
Pixell (1913) erected the genus Pomatoleios, consisting 
of the single known species, Pomatoleios kraussii (Baird, 
1864), and distinguishing it from Spirobranchus on the 
basis that the former lacks collar chaetae while the latter 
possesses them. However, it had been shown by Zibrowius 
(1968), ten Hove & Nishi (1996), and confirmed in the 
present study, that although collar chaetae are absent in 
adults, they are present in some juveniles. Hence, the use 
of absence of collar chaetae in Pomatoleios as a character 
to distinguish it from Spirobranchus would lead to an odd 
taxonomic situation in which juvenile Pomatoleios having 
collar chaetae are assignable to Spirobranchus and adults 
without them to Pomatoleios. 
The three nominal genera cannot also be separated on the 
basis of their radiolar arrangement i.e., that it is spiral in the 
Spirobranchus giganteus and Spirobranchus corniculatus 
complexes, but circular in the Spirobranchus tetraceros- 
complex, Pomatoceros and Pomatoleios. This is because, as 
described by ten Hove & Nishi (1996: 89) in Spirobranchus 
corrugatus Straughan 1967, for example, the radioles occur 
“in two perfect circles in small specimens,” but in “IV 2 
