Gynodiastylidae is one of the eight most commonly recognised families of crustaceans of the order Cumacea. They are especially prevalent in the southern hemisphere, with some types described from

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, Thailand and the Persian Gulf. Most are found at less than depth.

Anatomy

Gynodiastylidae have a small free telson, usually lacking terminal setae, though in some cases there may be two. The interior branch ( endopod) of the uropods is present on segments one through three. The number of free

thoracic somite The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of th ...

s is never reduced. The first

pereopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

s have a group of long rigid fibres ( setae) on the propodus. Males have no

pleopod The decapod ( crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various ...

s. The flagellum of the second

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

does not reach further than the hindmost edge of the

carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...

. Females have a very small second antenna (much smaller than the first). They also have no

exopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plur ...

s (outer branches) on their third

maxilliped An appendage (or outgrowth) is an external body part, or natural prolongation, that protrudes from an organism's body. In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including anten ...

s. Because they lack exceptions to the two most important diagnostic characteristics (the lack of pleopods in males and of exopods on maxilliped 3 in females), Gynodiastylidae have a pre-eminent place among monographic descriptions.

References

External links

* {{Taxonbar, from=Q2174097 Cumacea Taxa named by Thomas Roscoe Rede Stebbing Malacostraca families