Selenizone
A selenizone (from the
It is a spiral band of crescentric growth lines or threads (lunulae) on the shell surface due to the semicircular end of a notch or slit on the outer lip.[1]
A structure of the same type exists in several fossil groups of mollusks, including all the fossil families of slit shells, as well as three superfamilies of what may have been gastropods, but may possibly have been monoplacophorans or paragastropods instead.
The function of the holes and slits in living sea snails is to allow for
A new shell-morphological term 'sutsel' has been introduced by Dr. Geiger for the area between the SUTure and the SELenizone.[3]
In living gastropods
In the Pleurotomariidae (the slit shells), and the Scissurellidae (the little slit shells), the selenizone is a groove on the periphery of the shell which forms as the shell grows by the gradual sealing up of a slit that extends back from the edge of the aperture of the shell.
In the
In fossil groups
A selenizone is also present in several superfamilies of fossil mollusks. Not surprisingly it is seen in the numerous fossil gastropod families within the Pleurotomarioidae. The selenizone also exists in the
Taxa
A list of superfamilies and families (both living and fossil) which show this structure, based on the taxonomy of Bouchet et al 2005.[5] The taxa that are entirely extinct are marked with a dagger † :
Fossil taxa:
Gastropods
- Haliotoidea
- Pleurotomariacea
- † Family Catantostomatidae
- † Family Kittlidiscidae
- † Family Phymatopleuridae
- † Family Polytremariidae
- † Family Portlockiellidae
- † Family Rhaphischismatidae
- † Family Trochotomidae
- † Family Zygitidae
Gastropods or monoplacophorans or paragastropods
References
- ^ "selenizone". Academic Dictionaries and Encyclopedias.
- ^ "Repaired injuries and shell form in some Palaeozoicpleurotomarioid gastropods" (PDF). www.app.pan.pl. 2005. Retrieved 2021-04-06.
- ^ Geiger D.L. (2012) Monograph of the little slit shells. Volume 1. Introduction, Scissurellidae. pp. 1-728. Volume 2. Anatomidae, Larocheidae, Depressizonidae, Sutilizonidae, Temnocinclidae. pp. 729-1291. Santa Barbara Museum of Natural History Monographs Number 7.
- ^ "Welcome palaeos.org - BlueHost.com". www.palaeos.org. Archived from the original on 2012-09-08. Retrieved 2012-02-17.
- ISBN 3-925919-72-4. ISSN 0076-2997. 397 pp. [1]