The Azooxanthellate Scleractinia (Coelenterata: Anthozoa) of Australia
Author
Cairns, S. D.
text
Records of the Australian Museum
2004
56
259
329
journal article
2201-4349
Sphenotrochus excavatus
Tenison-Woods, 1878
Figs. 9G,H
Sphenotrochus excavatus
Tenison-Woods, 1878b: 308
, pl. 4, figs. 1A–C (
NSW
).–
Squires, 1961: 19
(
listed
).–
Wells, 1964: 109
(
listed
).–
Veron, 1986: 606
(
listed
).–Cairns, 1997: 25 (
listed
).
New records
. None.
Types
.
The
holotype
is deposited at the
Macleay Museum
; it is uncatalogued. Type Locality:
Port Jackson
,
New South Wales
, depth unknown
.
Redescription of
holotype
. Corallum 5.80×
4.07 mm
in CD (
GCD
:LCD= 1.43) and
9.44 mm
in height.
Costae
continuous (not fragmented), all costae but the 4 C3 flanking the medial C2 reach the base, those 4 C3 reaching only about 90% of that distance.
Costae
on thecal faces wide near calice (
0.38 mm
), narrowing to about
0.16 mm
near the base, but then widening to about
0.60 mm
width at the base, producing a slightly bulbous basal region.
Edge
costae of uniform width, about
0.40 mm
.
Intercostal
grooves deep, about
0.22 mm
wide.
Vertical
faces of costae in region adjacent to calice and base, and entire length of principal costae an the costae that flank principal costae, are finely ridged or fluted, such that about 10 carinae occur every mm.
Septa
hexamerally arranged in 3 cycles (24 septa) according to the formula: S1–2>S3, but the 4 S2 adjacent to the principal S1 are somewhat smaller than those occurring in the lateral systems. S1–2 about
1 mm
exsert and have vertical axial edges that bear small teeth that project horizontally into the fossa. S3 about
0.5 mm
exsert, but are essentially vestigial inside the calice.
Fossa
quite deep, containing a small, deep-set, lamellar columella
.
Remarks
. This species is redescribed based on a reexamination of the
holotype
. It is unique, in that it is known from only
one specimen
and is quite unlike any of the other nine Recent species belonging to the nominate subgenus of
Sphenotrochus
. It differs from other species by having a full corallum shape with a relatively high GCD:LCD, a bulbous base, fluted costal edges, and a deeply-set columella. Given the large amount of collecting in the Sydney region since 1878, even though this species is relatively small, it is surprising that it has not been re-collected.