Comitas aldingensis

Comitas aldingensis Temporal range: late Eocene–late Oligocene PreꞒ Ꞓ O S D C P T J K Pg N
Holotype from Auckland War Memorial Museum
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Caenogastropoda
Order:	Neogastropoda
Family:	Pseudomelatomidae
Genus:	Comitas
Species:	†C. aldingensis
Binomial name
†Comitas aldingensis Powell, 1944
Synonyms [1]
† Comitas (Carinacomitas) aldingensisA. W. B. Powell, 1944

Comitas aldingensis is an extinct species of sea snail, a marine gastropod mollusc in the family Pseudomelatomidae. ^[1] Fossils of the species date to the late Eocene and late Oligocene, and occurs in the strata of the southern coast of Australia, including the Eucla Basin, St Vincent Basin and the Otway Basin.

Description

Reverse view of holotype

In the original description, Powell described the species as follows:

Shell much smaller and more heavily sculptured than clarae. The protoconch is broadly rounded, rather erect, of two smooth whorls, which are strongly carinated throughout. The species approaches the New Zealand Recent Anticomitas vivens Powell 1942, but in that genus the whole protoconch is very depressed and flattened on top. The anterior canal, also is much shorter in the Recent species. Whorls bluntly angled just below the middle, sculptured with prominent broadly rounded axials, rapidly fading out on shoulder and not extending over base, 10 per whorl, First post-nuclear whorl develops a spiral thread above the carina, soon followed by another below the carina. These spirals form the three primary keels of subsequent whorls. On the body-whorl two further strong spirals develop near the top of the aperture. There are about 26 narrow spirals on the body-whorl, these becoming gradually smaller and closer spaced towards the anterior end. The shoulder is smooth except for a fine line submargining the suture. The three main spirals develop vertically compressed tubercles where they cross the axials. ^[2]

The protoconch has between 1.75-2.5 smooth whorls, and has a median carina which develops on either of the first two whorls, which merges into the teleoconch. The teleoconch is fusiform and fairly thin, the species' spire is turretted and approximately half the height of the shell. ^[3] The species measures an average height of 8.5 mm (0.33 in) and a diameter of 3.7 mm (0.15 in) in diameter. Specimens found from Thomson Road have very weak carinar on the second whorl of the protoconch, and carinae development can vary depending on the location where fossils were found. ^[4]

Taxonomy

The species was first described by A.W.B. Powell in 1944, under the name Comitas (Carinacomitas) aldingensis, ^[2] and has been referred to by its current name from 1969. ^{[5] : 292} The holotype was collected from Aldinga Beach, South Australia, at an unknown date prior to 1944, and is held by the Auckland War Memorial Museum. ^{[6] [7]}

Distribution

This extinct marine species dates between the late Eocene and late Oligocene, and occurs in the strata of the Eucla Basin and St Vincent Basin of South Australia, including the Pallinup Formation and the Blanche Point Formation, and the Otway Basin of South Australia/Victoria in the Browns Creek Formation. ^{[6] [8]}

References

1. Comitas aldingensis A. W. B. Powell, 1944 † . 17 November 2025. Retrieved through: World Register of Marine Species .
2. Powell, A. W. B. (1944). "The Australian Tertiary Mollusca of the Family Turridae". Records of the Auckland Institute and Museum . 3: 3–68. ISSN   0067-0464. JSTOR   42905993. Wikidata   Q58676624.
3. Long, D. C. (1981). "Late Eocene and Early Oligocene Turridae (Gastropoda: Prosobranchiata) of the Brown's Creek and Glen Aire Clays, Victoria, Australia" (PDF). Memoirs of the National Museum of Victoria. 42 (1): 15–55. doi:10.24199/J.MMV.1981.42.03. ISSN   0083-5986. Wikidata   Q56195002.
4. Darragh, Thomas A. (2017). "Further Mollusca from the late Eocene Pallinup Formation, Eucla Basin, Western Australia". Records of the Western Australian Museum. 32 (1): 29. doi:10.18195/ISSN.0312-3162.32(1).2017.029-100. ISSN   0312-3162. Wikidata   Q55920053.
5. Powell, A. W. B. (9 September 1969). "The family Turridae in the Indo-Pacific. Part 2. The subfamily Turriculinae". Indo-Pacific mollusca. 2 (10): 215–416. ISSN   0073-7240. Wikidata   Q136806872.
6. Blom, Wilma M. (2025). "Annotated Catalogue of Fossil and Extant Molluscan Types in the Auckland War Memorial Museum". Bulletin of the Auckland Museum . 22. doi:10.32912/BULLETIN/22. ISSN   1176-3213. Wikidata   Q135397912.
7. "Comitas aldingensis". Collections Online. Auckland War Memorial Museum . Retrieved 17 November 2025.
8. Darragh, Thomas A. (August 2024). "A checklist of Australian marine Cenozoic Mollusca". Memoirs of Museum Victoria . 83: 37–206. doi:10.24199/J.MMV.2024.83.02. ISSN   1447-2546. Wikidata   Q136396722.