Four view of the slit shell Mikadotrochus hirasei. The first view shows the selenizone well. The other views show its relationship to the slit in the shell.Three artificially polished shells of a New Zealand abalone, a Haliotis species, probably H. iris. The central shell clearly shows the selenizone as a series of holes
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 exhalant water circulation, which is important for respiration and other functions. It has also been suggested that the selenizone may serve to reinforce the shell against catastrophic breakage during predation attempts.[2]
A new shell-morphological term 'sutsel' has been introduced by Dr. Geiger for the area between the SUTure and the SELenizone.[3]
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 Haliotidae, the abalones, the selenizone takes the form of a series of holes in the shell (reaching back from the leading growth edge of the aperture) which form as the shell grows. The older holes are gradually sealed up as the shell grows and new holes form. Each abalone species has a typical number of holes in the selenizone which remain open, and this feature is diagnostic for the individual species.
In fossil groupsedit
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 Bellerophontoidea, which may be gastropods or monoplacophorans; in the Euomphaloidea, which are probably gastropods, but may be monoplacophorans; and in the Macluritoidea, which are either archaeogastropods or Paragastropoda Linsley & Kier, 1984, (paragastropods are a group of mollusks that superficially resemble gastropods, but were untorted).[4]
Taxaedit
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 † :
^"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.
^. www.palaeos.org. Archived from the original on 2012-09-08. Retrieved 2012-02-17.
^Bouchet P. & Rocroi J.-P. (Ed.); Frýda J., Hausdorf B., Ponder W., Valdes A. & Warén A. 2005. Classification and nomenclator of gastropod families. Malacologia: International Journal of Malacology, 47(1-2). ConchBooks: Hackenheim, Germany. ISBN3-925919-72-4. ISSN 0076-2997. 397 pp. [1]
External linksedit
Selenizone mentioned here
Paper on the selenizone and breakage in fossil shells
Information on paragastropods here
January 01, 1970
selenizone, selenizone, from, greek, selene, meaning, moon, zone, meaning, girdle, anatomical, structure, that, exists, shells, some, families, living, snails, slit, shells, little, slit, shells, abalones, which, marine, gastropod, mollusks, from, ancient, lin. A selenizone from the Greek selene meaning moon and zone meaning girdle is an anatomical structure that exists in the shells of some families of living sea snails the slit shells the little slit shells and the abalones which are marine gastropod mollusks from ancient lineages Four view of the slit shell Mikadotrochus hirasei The first view shows the selenizone well The other views show its relationship to the slit in the shell Three artificially polished shells of a New Zealand abalone a Haliotis species probably H iris The central shell clearly shows the selenizone as a series of holes 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 exhalant water circulation which is important for respiration and other functions It has also been suggested that the selenizone may serve to reinforce the shell against catastrophic breakage during predation attempts 2 A new shell morphological term sutsel has been introduced by Dr Geiger for the area between the SUTure and the SELenizone 3 Contents 1 In living gastropods 2 In fossil groups 3 Taxa 4 References 5 External linksIn living gastropods editIn 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 Haliotidae the abalones the selenizone takes the form of a series of holes in the shell reaching back from the leading growth edge of the aperture which form as the shell grows The older holes are gradually sealed up as the shell grows and new holes form Each abalone species has a typical number of holes in the selenizone which remain open and this feature is diagnostic for the individual species In fossil groups editA 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 Bellerophontoidea which may be gastropods or monoplacophorans in the Euomphaloidea which are probably gastropods but may be monoplacophorans and in the Macluritoidea which are either archaeogastropods or Paragastropoda Linsley amp Kier 1984 paragastropods are a group of mollusks that superficially resemble gastropods but were untorted 4 Taxa editA 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 Extant taxa Haliotoidea Haliotidae Pleurotomarioidea Pleurotomariidae Scissurelloidea Anatomidae Scissurellidae Fossil taxa Gastropods Haliotoidea Temnotropidae Pleurotomariacea Family Catantostomatidae Family Kittlidiscidae Family Phymatopleuridae Family Polytremariidae Family Portlockiellidae Family Rhaphischismatidae Family Trochotomidae Family Zygitidae Gastropods or monoplacophorans or paragastropods Bellerophontoidea Bellerophontidae Bucanellidae Bucaniidae Euphemitidae Pterothecidae Sinuitidae Tremanotidae Tropidodiscidae Euomphaloidea Euomphalidae Helicotomidae Lesueurillidae Omphalocirridae Omphalotrochidae Macluritoidea MacluritidaeReferences edit 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 Bouchet P amp Rocroi J P Ed Fryda J Hausdorf B Ponder W Valdes A amp Waren A 2005 Classification and nomenclator of gastropod families Malacologia International Journal of Malacology 47 1 2 ConchBooks Hackenheim Germany ISBN 3 925919 72 4 ISSN 0076 2997 397 pp 1 External links editSelenizone mentioned here Paper on the selenizone and breakage in fossil shells Information on paragastropods here Retrieved from https en wikipedia org w index php title Selenizone amp oldid 1177715767, wikipedia, wiki, book, books, library,
