A revision of the Australian fossil species of Zoila (Gastropoda: Cypraeidae)
Author
Darragh, Thomas A.
text
Memoirs of Museum Victoria
2011
2011-12-31
68
1
28
https://museumsvictoria.com.au/collections-research/journals/memoirs-of-museum-victoria/volume-68-2011/pages-1-28/
journal article
10.24199/j.mmv.2011.68.01
1447-2554
10665999
Zoila viathomsoni
sp. nov.
Figures 1D
,
2C
,
5B–C, H, L
Description
. Shell of small size for genus (
19–28 mm
in length), pyriform. Spire not visible on most specimens, projecting on
one specimen
. Posterior canal very short, slightly bent to left. Anterior canal very short, slightly deflected to right. Aperture slightly sinuous; outer lip with about 23–25 teeth present along entire lip; columella with about 23–26 teeth present along entire lip. Fossula well-developed, deep, elongate, projecting, bounded anteriorly by thickened ridge; very weak notch present in inner edge just posterior to anterior ridge; weak terminal ridge joining edge of fossula. First columellar tooth adjacent to terminal ridge, almost blocking shallow sulcus that extends into fossula parallel to terminal ridge.
Dimensions.
est. = estimated
Type
locality
.
PL3171
gravel scrape beside
Thomson Highway
,
23.5 km
north of
Highway
l, north of
Walpole
,
Western Australia
.
Grid
ref.
Deep River
(l:100 000 series) 743487.
Pallinup Siltstone
,
Aldingan
,
Late Eocene
.
Type material
.
Western Australian Museum
:
Holotype
WAM 72.296
, collected
T
.
A. Darragh
and
G.W. Kendrick
,
12–14 March 1969
;
paratype
WAM 72.253
, collected
G.W. and W.E. Kendrick
,
25 January 1969
.
Museum
Victoria
:
Paratype
P310193, collected
T
.
A. Darragh
&
G.W. Kendrick
,
12-14 March 1969
.
Time range.
Aldingan, Late Eocene.
Occurrence and material
.
Type
locality only (one undistorted specimen, four complete distorted specimens, nine fragments).
Remarks
. This is one of the two oldest true cowries recorded from
Australia
and occurs only in southwest
Australia
, associated with
Willungia ovulatella
(Tate)
and
Semitrivia pompholugota
(Tate)
. Specimens from the
type
locality are preserved as silica replacements weathered out of the Pallinup Siltstone. The associated fauna comprises large numbers of siliceous sponges. The protoconch observed in cross-section (fig. 2C), is paucispiral and slightly deviated from the axis of the teleoconch, unlike the multispiral protoconchs of
Cypraeorbis
species.
The general size and shape of the shell resembles that of
Cypraeorbis medius
,
C. bartonensis
and
C. ventripotens
; however, the fossula (fig. 5L) is not the same as that present in these species. The fossula is very wide and prominent, projecting into the aperture. It is more elongate than that of these three species, does not have a prominent notch and the anterior border is not thickened. In general shape and concavity, it resembles those in
Zoila friendii
and
Z. decipiens
.
Zoila viathomsoni
bears a close resemblance to
Z. chathamensis
(Cernohorsky)
, late Paleocene to early Eocene,
Chatham Islands
,
New Zealand
, but it is not as tumid, has much finer and more numerous apertural teeth, the posterior labral border of the posterior canal is more produced posteriorly and it is only about two-thirds the size. Given the similarities,
Z. chathamensis
is a possible ancestor of
Z
.
viathomsoni
sp. nov.
;
Z.
chathamensis
is the earliest known representative of the genus.
Figure 1. A,
Cypraeorbis medius
(
Deshayes,1835
)
, × 5;B,
Cypraeorbis sphaeroides
(
Conrad,1848
)
,× 5; C,
Cypraeorbis ventripotens
(
Cossmann, 1903
)
, × 5; D,
Cypraeorbis viathomsoni
sp. nov.
WAM 72.296, × 5; E,
Zoila didymorhyncha
sp. nov.
P302687, × 2.6; F,
Zoila campestris
sp. nov.
WAM 89.437, × 2.6; G,
Zoila fodinata
sp. nov.
WAM 89.637, × 3; H,
Zoila chathamensis
(
Cernohorsky, 1971
) GNSTM
87922, × 2.3. Arrows indicate the location of the notch.
Figure 2. Protoconchs. A,
Zoila platypyga
(
McCoy, 1876
)
, P308781, × 7; B,
Zoila gigas
(McCoy, 1867)
, P308792, × 3.6; C,
Zoila viathomsoni
sp. nov.
, WAM × 10.
| L |
W |
H |
LT |
CT |
| Holotype P302687 |
62 |
31 |
25 |
24 |
26 |
| Paratype P302685 |
80 |
32 |
27 |
10 |
3 |
| P302686 |
64+ |
32 |
26 |
22+ |
25 anterior canal broken |
Zoila viathomsoni
bears some resemblance in size and shape to
Lyncina (Austrocypraea) onkastoma
Yates, 2009
, recorded from the early Oligocene of
South Australia
, but lacks the well-defined anterior rostrum of
L. (A.) onkastoma
, as well as the prominent notch on the fossula.
Etymology
. Latin via road.