Overview
Vermetidae, common name the worm snails or worm shells, is a taxonomic family of small to medium-sized sea snails, marine gastropod molluscs in the clade Littorinimorpha.1]
The shells of the Vermetidae are extremely irregular, and do not resemble the average snail shell, hence the common name "worm shells" or "worm snails".
They usually grow cemented onto a hard surface, or cemented together in colonies.
Shell description
These snails do not have typical regularly coiled gastropod shells; instead they have very irregular elongated tubular shells which are moulded to, and cemented to, a surface of attachment such as a rock or another shell and so on. In the adult the apertural part of the shell is usually free, with the opening directed upward. Some species have an operculum and some do not. Damage d sections of the shell can be sealed off by calcareous septa when necessary.
Some vermetids are solitary, whereas others live in colonies, partially cemented together. The shells of species within this family vary greatly and can sometimes be extremely challenging to identify.
Comparison with annelid worm tubes
The empty calcareous tubes of certain marine annelid tube worms, for example the Serpulidae, can sometimes be casually misidentified as empty vermetid shells, and vice versa. The difference is that vermetid shells are shiny inside and have 3 shell layers, whereas the annelid worm tubes are dull inside and have only 2 shell layers.
Taxonomy
2005 taxonomy
Vermetidae have been recognized in as the only family in the superfamily Vermetoidea in the taxonomy of Bouchet & Rocroi (2005) within clade Littorinimorpha.
The following two subfamilies have been recogni zed in the taxonomy of Bouchet & Rocroi (2005):[1]
Family Vermetidae Rafinesque, 1815
- Subfamily Vermetinae Rafinesque, 1815
- Subfamily Dendropomatinae Bandel & Kowalke, 1997
This classification of the Vermetoidea has been somewhat controversial. Studies, based on sperm ultrastructure[2], and on molecular data[3] clearly place it within the clade Littorinimorpha. However, there are still a number of authors[4][5][6] that place it within the superfamily Cerithioidea. The genera Campanile and Serpulorbis from a clade that is sister to the Cerithioidea, as shown in a study by Lydeard et al. (2002).[7]
2006 taxonomy
Bandel (2006)[8] have established a new subfamily Laxispirinae and he have been recognized three subfamilies of Vermetidae:
- Subfamily Vermetinae Rafinesque, 1815
- Subfamily ? Laxispirinae Bandel, 2006[8]
- Subfamily Dendropomatinae Bandel & Kowalke, 1997
Genera
Genera within the family Vermetidae include:
Vermetinae
? Laxispirinae
- ? Laxispira Gabb, 1877 - Late Cretaceous, type genus of the subfamily[8]
Dendropomatinae
- Dendropoma M?rch, 1861 - type genus of the subfamily[11]
subfamily ?
- Bivonia Gray, 1842[12]
- Eualetes Keen, 1971[13]
- Novastoa Finlay, 1926[14]
- Petaloconchus I. Lea, 1843[15]
- Serpulorbis Sassi, 1827[16]
- Spiroglyptus Daudin, 1800[17]
- Stephopoma M?rch, 1860[18]
- Thylaeodus M?rch, 1860[19]
External links
- Powell A. W. B., New Zealand Mollusca, William Collins Publishers Ltd, Auckland, New Zealand 1979 ISBN 0-00-216906-1
- R. Tucker Abbott, 1986. Seashells of North America, St. Martin's Press, New York