Yochelcionella
Encyclopedia
Yochelcionella is an extinct genus
of basal molluscs which lived during the Tommotian epoch
, the first epoch of the Cambrian
period. This genus is often reconstructed to resemble snail
s (gastropods).
Yochelcionella is a type genus
in the family Yochelcionellidae.
This genus of molluscs possessed shells which were shaped like curved caps, with an exhaust pipe shaped "snorkel
" emanating underneath where the apex (point of the shell) curves over. All experts agree that the "snorkel" was used in breathing, with most experts suspecting that it allowed waste water to flow away from the gill
s.
ns. Their snorkel may represent a move towards a tubular shell, such as is seen in the modern scaphopods. It's also been interpreted as a precursor to the cephalopod funnel or siphuncle.
The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005
categorizes Yochelcionella in the family Yochelcionellidae within the superfamilia Yochelcionelloidea
within the Paleozoic molluscs of uncertain position within Mollusca (Gastropoda or Monoplacophora).
For alternate 2007-2007 taxonomy by P. Yu. Parkhae see Helcionelloida
.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of basal molluscs which lived during the Tommotian epoch
Epoch (geology)
An epoch is a subdivision of the geologic timescale based on rock layering. In order, the higher subdivisions are periods, eras and eons. We are currently living in the Holocene epoch...
, the first epoch of the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
period. This genus is often reconstructed to resemble snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s (gastropods).
Yochelcionella is a type genus
Type genus
In biological classification, a type genus is a representative genus, as with regard to a biological family. The term and concept is used much more often and much more formally in zoology than it is in botany, and the definition is dependent on the nomenclatural Code that applies:* In zoological...
in the family Yochelcionellidae.
Description
Snorkeling
Snorkeling is the practice of swimming on or through a body of water while equipped with a diving mask, a shaped tube called a snorkel, and usually swimfins. In cooler waters, a wetsuit may also be worn...
" emanating underneath where the apex (point of the shell) curves over. All experts agree that the "snorkel" was used in breathing, with most experts suspecting that it allowed waste water to flow away from the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s.
Taxonomy
When they were first discovered, they were originally thought to be monoplacophoraMonoplacophora
Monoplacophora, meaning "bearing one plate", is a polyphyletic class of mollusks with a cap-like shell, living on the bottom of deep sea. Extant representatives were unknown until 1952; previously they were known only from the fossil record.- Definition :...
ns. Their snorkel may represent a move towards a tubular shell, such as is seen in the modern scaphopods. It's also been interpreted as a precursor to the cephalopod funnel or siphuncle.
The taxonomy of the Gastropoda by Bouchet & Rocroi, 2005
Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...
categorizes Yochelcionella in the family Yochelcionellidae within the superfamilia Yochelcionelloidea
Yochelcionelloidea
Yochelcionelloidea is an extinct superfamily of paleozoic molluscs of uncertain position . The earliest yochelcionellids are known from the Middle Tommotian, but they are most diverse from the Botomian through the early Middle Cambrian.- 2005 taxonomy :The taxonomy of the Gastropoda by Bouchet &...
within the Paleozoic molluscs of uncertain position within Mollusca (Gastropoda or Monoplacophora).
For alternate 2007-2007 taxonomy by P. Yu. Parkhae see Helcionelloida
Helcionelloida
Helcionelloida is the name given to an extinct group of ancient molluscs . These are the oldest known conchiferan molluscs, that is, they had a mineralised shell. Some members of this class were mistaken for Monoplacophorans. The class was erected by Peel in 1991.-Anatomy:These animals were...
.
Species
Species in the genus Yochelcionella include:- Yochelcionella americana Runnegar & Pojeta, 1980
- Yochelcionella angustiplicata
- Yochelcionella chinensis Pei, 1985
- Yochelcionella crassa Zhegallo in Esakova et Zhegallo, 1996
- Yochelcionella cyrano
- Yochelcionella daleki
- Yochelcionella erecta (Walcott, 1891)
- Yochelcionella gracilis Atkins & Peel, 2004
- Yochelcionella greenlandica Atkins & Peel, 2004
- Yochelcionella ostentata
- Yochelcionella saginata Vendrasco et al., 2010
- Yochelcionella snorkorum Vendrasco et al., 2010