subclass dibranchia
Definition
Noun: - A taxonomic subclass within the class Cephalopoda, comprising all living cephalopods except the nautiluses. Members of this subclass are characterized by having two gills and typically an internal or reduced shell. It includes the orders Octopoda (octopuses) and Decapoda (squids and cuttlefish).
Usage
- The term is used in scientific, particularly zoological and biological, contexts to classify a major group of cephalopod mollusks.
- It is a formal taxonomic rank.
Examples
- Noun:
- The subclass Dibranchia is distinguished from the subclass Nautiloidea by the number of gills.
- All modern, commercially important cephalopods like squid and octopus belong to the subclass Dibranchia.
Advanced Usage
- In Taxonomic Hierarchy: The term is used to specify a precise level of biological classification.
- In the classification system, Cephalopoda is the class, and Dibranchia is one of its subclasses.
Variants and Related Words
- Dibranchiate (adj): Having two gills. This adjective form describes the characteristic feature of the subclass.
- Dibranchiate cephalopods like the cuttlefish have a more complex nervous system than nautiluses.
Synonyms
- Two-gilled cephalopods: A descriptive synonym highlighting the primary anatomical feature.
- Coleoidea: In modern taxonomic revisions, the group containing squids, octopuses, and cuttlefish is often referred to as the subclass Coleoidea, which is largely synonymous with the historical group Dibranchia.
Notes on Meaning
- The definition is highly specific to zoological taxonomy. The word is not used in everyday language.
- Historically, "Dibranchia" was a standard subclass, but contemporary taxonomy may use "Coleoidea" more frequently. However, "Dibranchia" remains valid and descriptive.
Noun
-
comprising all living cephalopods except the family Nautilidae: the orders Octopoda (octopuses) and Decapoda (squids and cuttlefish)
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