Research Article |
Corresponding author: Paul C. Southgate ( psouthgate@usc.edu.au ) Academic editor: Thomas A. Neubauer
© 2022 Paul C. Southgate, Mike Roberts.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Southgate PC, Roberts M (2022) A new species of Austrocypraea (Mollusca, Gastropoda, Cypraeidae) from the Pliocene of Flinders Island, Tasmania. ZooKeys 1123: 173-185. https://doi.org/10.3897/zookeys.1123.90917
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A new morphologically distinct species of cowry (family Cypraeidae Rafinesque, 1815) is described from the Pliocene of Flinders Island, Tasmania. Austrocypraea jimgracei sp. nov. differs morphologically from other members of the genus and is particularly characterised by the development of a heavily callused labral margin, with a distinct marginal edge that bends up towards the dorsum centrally. This feature is unique within the genus. The new taxon is only the second known Austrocypraea from the Pliocene. A revised key to the known Austrocypraea fossil species is presented.
Cameron Inlet Formation, cowrie, cowry, fossil, taxonomy
The marine gastropod genus Austrocypraea Cossmann, 1903 (Gastropoda, Cypraeidae) is endemic to southern Australia where it has an extensive fossil record from the Oligocene (
The geology and fossil molluscan fauna of Flinders Island, in the Bass Strait off the north-eastern coast of Tasmania, were described by
All examined specimens were recovered from material excavated for farm dams in the Lackrana area of Flinders Island, Tasmania. Assignment of specimens to the late Pliocene Cameron Inlet Formation was confirmed by reference to molluscan assemblages previously described for the Cameron Inlet Formation and the Pleistocene Memana Formation that disconformably overlies the Cameron Inlet Formation (
Shell length (L), width (W), and height (H) were measured as described by
MR Mike Roberts collection, Flinders Island, Tasmania, Australia;
PS Paul Southgate collection, Brisbane, Australia.
Class Gastropoda Cuvier, 1795
Order Littorinimorpha Golikov & Starobogatov, 1975
Superfamily Cypraeoidea Rafinesque, 1815
Cypraea contusa McCoy, 1877, by original designation. Balcombian, Middle Miocene, Fossil Beach, Victoria, Australia.
Holotype. Australia, Lackrana, Flinders Island, Tasmania; 40°06'37"S, 148°10'18"E; May, 2012; P.C. Southgate and M. Roberts leg.; dry specimen (fossil); among spoil material excavated for farm dam; TMAGZ10628.
Paratypes. Australia; same location as holotype; May, 2012-Feb, 2021; P.C. Southgate and M. Roberts leg.; dry specimens (fossils); among spoil material excavated for farm dam; TMAGZ10629 (1 specimen);
Australia; same location as holotype; May, 2012-Feb, 2021; P.C. Southgate and M. Roberts leg.; dry specimens (fossils); among spoil material excavated for farm dam; PS CF.305/306 (2 specimens); MR 657/658 (2 specimens); TMAGZ10630 (five partial specimens).
Austrocypraea jimgracei sp. nov. can be separated from all other members of the genus, fossil and extant, by a combination of the following characteristics: shell ovate to sub-pyriform, humped, highest point towards posterior, shell height around 71% length, shell width around 59% length; anterior extremity subtruncate, not extended in lateral profile, supported by well-defined anterior lateral flanges; protoconch paucispiral, spire projecting, overlain by callus. Aperture gently curved to the left posteriorly, widening slightly towards anterior; evenly spaced, relatively strong dentition; 13–17 columellar teeth, restricted to aperture, larger towards anterior; 17–21 labral teeth are longer, incised, and restricted to aperture margin. Fossula is broad, concave and smooth centrally, with shallow, barely discernible longitudinal depression or slightly raised ridge sometimes present; fossular margin with 4–6 denticles, visible in ventral view; anterior denticles not linked to adjacent columellar teeth by transverse ridges, but fine ridges may link posterior fossular denticles to adjacent columellar teeth. Columella smooth posterior to the fossula, lacking a defined columella ridge. Labral margin heavily callused, forming a distinct marginal edge, bent up towards the dorsum centrally; shallow anterior and posterior labral grooves may accommodate small, irregular, often elongate, pustules dorsal to the labral marginal edge; marginal edge may be weakly crenulate where marginal pustules intersect.
Average size for the genus (Table
Descriptions and repositories of the type series of Austrocypraea jimgracei sp. nov.
Specimens (repository) | Length (mm) | Width (mm) | Height (mm) | Columellar teeth | Labral Teeth |
---|---|---|---|---|---|
Holotype (TMAGZ10628) | 24.2 | 17.5 | 14.5 | 16 | 21 |
Paratype 1 ( |
25.4 | 18.5 | 15.4 | 13 | 17 |
Paratype 2 ( |
23.1 | 16.4 | 13.8 | 16 | 20 |
Paratype 3 ( |
25.2 | 18.2 | 14.9 | 16 | 18 |
Paratype 4 (MR 635) | 23.6 | 16.4 | 13.9 | 14 | 18 |
Paratype 5 (PS CF.174) | 24.4 | 16.9 | 14.4 | 15 | 20 |
Paratype 6 (PS CF.175) | 25.5 | 17.7 | 14.9 | 17 | 20 |
Mean (± SD) | 24.5 (±0.9) | 17.4 (±0.8) | 14.5 (±0.6) | 15.3 (±1.4) | 19.0 (±1.5) |
Variation. Available specimens show variation in the angle of slope of the fossula, the number and form of fossular marginal denticles, and the presence, or otherwise, of a shallow depression or a slightly raised ridge on the central part of the fossula (Fig.
Shell shape in cowries is commonly expressed using a ‘shell formula’ which reports linear shell measurements, and their ratios, as well as normalised tooth counts (
Shell formulae [L (W/L – H/L – H/W) nLT: nCT] for known Austrocypraea fossil species for which complete morphometric data are available.
Species | Shell formula | Data source(s) |
---|---|---|
Austrocypraea constricta | 14 (59-48-81) 26:14 |
|
A. archeri | 21 (61-50-86) 22:17 | PS collection |
A. subsidua | 22 (65-52-80) 25:18 |
|
A. scalena | 30 (64-57-89) 24:16 |
|
A. subcontusa | 15 (67-55-82) 18:15 |
|
A. contusa | 26 (74-66-89) 21:17 |
|
A. ampullacea | 34 (56-53-94) 27:22 |
|
A. parallela | 18 (53-46-86) 32:20 |
|
A. amae | 28 (71-60-84) 22:16 | |
A. rumballi | 16 (73-63-85) 16:14 |
|
A. goudeyana | 22 (68-58-86) 17:16 |
|
A. jimgracei sp. nov. | 24 (71-59-84) 19:15 | This study |
Clear differences in fossula structure also separate A. jimgracei sp. nov. from A. amae and A. rumballi. The fossula of A. amae is crossed by ribs which are continuous with the anterior columellar teeth and extend to the inner margin of the fossula (Table
Comparison of shell characters of Austrocypraea amae
Character | Species | ||
---|---|---|---|
Austrocypraea amae | A. rumballi | A. jimgracei sp. nov. | |
Length (mm): | 20.7–38.9 | 11.0–22.1 | 23.1–25.5 |
Shape: | ovate, sub-pyriform to sub-cylindrical; highest point in posterior third. Short anterior extremity not extended in lateral profile. | broadly ovoid; inflated specimens globular. Anterior extremity short but extended in lateral profile. | ovate to sub-pyriform; highest point towards posterior; short anterior extremity, not extended in lateral profile, supported by well-developed lateral flanges. |
Sculpture: | moderately to weakly malleate, mainly posteriorly; base smooth. | malleation present on the left side of many specimens but absent in others; base smooth. | malleation absent; base smooth. |
Fossula: | broad, impressed, traversed by 6 or 7 ribs continuous with columella teeth. | broad with projecting inner margin; fossula denticles (~ 6) linked to columella teeth by transverse ridges becoming obsolete anteriorly. Indistinct tubercle or ridge centrally. | broad, inner margin with 4–6 denticles that do not connect to columella teeth; central fossula smooth. Shallow, longitudinal depression or raised area sometimes present centrally. |
Labral margin: | rounded but not heavily thickened; generally rounded in posterior profile. | rounded but not heavily thickened; generally rounded in posterior profile. | heavily callused, forming a distinct marginal edge, bent up centrally; pustules or small tubercules often present dorsal to marginal edge. |
Data source(s): | |
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This study |
The Miocene species A. contusa and A. goudeyana have similar size and proportions to A. jimgracei sp. nov., and the form of the anterior extremity, supported by distinct anterior lateral flanges, may also be similar for these species. However, A. contusa and A. goudeyana are readily separated from A. jimgracei sp. nov. because of their more produced anterior extremity, narrower aperture, which has consistent width throughout, and stronger dentition that may extend onto the columella. The form of the heavily callused labral margin of A. jimgracei sp. nov., that is bent up towards the dorsum centrally, is unique within the genus. Other species within the genus, such as A. contusa, A. goudeyana and A. subcontusa, may also develop a well-defined thickened labral margin, but unlike that of A. jimgracei sp. nov., when present, it generally forms a thin step-like rim to the shell margin that does not bend up towards the dorsum. The shells of a number of Austrocypraea species, including the extant A. reevei, have shallow contusions or ‘malleation’ on the dorsal surface of the shell, but this is not a ubiquitous feature of the genus. For example, malleation is prominent on the shells of A. contusa and A. goudeyana, less prominent and generally restricted to the posterior half of the body whorl in A. rumballi and A. amae, obscure or absent in A. scalena, but totally lacking in A. onkastoma, A. archeri, A. subsidua and A. parallela, and in all examined specimens of A. jimgracei sp. nov.
Named in honour and in memory of the late Jim Grace of Lackrana, Flinders Island, on whose property all specimens of the new species were recovered.
Known only from the Cameron Inlet Formation, Lackrana area, Flinders Island, Tasmania.
The following key is based on shell morphology and is modified from
1 | Shell ovate, globular or pyriform; fossula abruptly constricted posteriorly | 2 |
– | Shell cylindrical; fossula scarcely constricted posteriorly, broad but rather shallow | A. parallela |
2 | Fossula very broad, concave, projecting; dorsum smooth, small contusions more apparent posteriorly if present; columella smooth posteriorly | 3 |
– | Fossula rather narrow, concave; dorsum with numerous, close small contusions throughout; columellar teeth often produced across the columella posteriorly | 5 |
3 | Shell not exceeding 17 mm; aperture sinuous, inner lip rather constricted in the anterior third; shell subcylindrical | A. constricta |
– | Shell exceeding 17 mm | 4 |
4 | Base flattened; aperture rather wide; anterior top of outer lip rather rounded; fossula extremely broad, irregularly ribbed | A. subsidua |
– | Base convex; aperture equally narrow but may widen slightly anteriorly | 5 |
5 | Shell generally not exceeding 20 mm | 6 |
– | Shell exceeding 20 mm | 7 |
6 | Shell ovate, slightly depressed; dentition rather course, columella teeth often produced | A. subcontusa |
– | Shell ovate to globose; columella teeth short, second tooth weakly developed; fossula greatly protruding, with central tubercule | A. rumballi |
7 | Elongate; dentition extremely fine and numerous | A. ampullacea |
– | Shell inflated, pyriform, ovate or globular | 8 |
8 | Pyriform to globular, inflated, dorsum intensely malleate | 9 |
– | Ovate to sub-pyriform, inflated, dorsal contusions reduced or absent | 10 |
9 | Anterior terminal collar elongated, elevated in lateral profile | A. goudeyana |
– | Anterior terminal collar shorter and low in lateral profile | A. contusa |
10 | Fossula ribbed, or marginal denticles present | 11 |
– | Fossula smooth, without marginal denticles; columellar teeth developed posteriorly, no dorsal contusions | A. onkastoma |
11 | Aperture equally narrow throughout | 12 |
– | Aperture widening towards anterior | 13 |
12 | Sub-pyriform; narrow, ribbed fossula; no dorsal contusions; rarely exceeding 27 mm | A. archeri |
– | Ovate, mostly exceeding 27 mm; fossula regularly ribbed | A. scalena |
13 | Ovate to sub-pyriform; fossula traversed by 6 or 7 ribs continuous with columellar teeth; contusions, if present, more apparent posteriorly | A. amae |
– | Ovate to sub-pyriform; fossula smooth centrally, margin with 4–6 denticles; no dorsal contusions; well-developed labral margin | A. jimgracei sp. nov. |
Austrocypraea jimgracei sp. nov. is only the second known member of the genus from the Pliocene and this description increases the number of known fossil species within Austrocypraea to thirteen. The new species has characteristics that are typical of the genus, including a well-produced denticulate fossula, a paucispiral protoconch indicating intracapsular development, and a projecting spire. It also has some characteristics that are not present in any other Austrocypraea species, including a heavily callused labral margin and the presence of pustules or small tubercules within the labral grooves above (dorsal to) the marginal edge. Extensive molecular analysis within the family Cypraeidae (e.g.,
We thank Betty and Jim Grace and their family for access to their property for specimen collection and Dawn and Naomi for support and technical assistance. We also thank Drs Felix Lorenz and Adam Yates, who provided constructive inputs to this paper. This study was supported by University of the Sunshine Coast Research Initiative funding to the first author.