Anabaritida

Belongs within: Trilobozoa. From three to two Published 23 August 2011 The mysterious anabaritids of the Lower Cambrian have been referred to on this site before. In the earlier, somewhat brief post, I referred to their triradial structure and uncertain, though probably coelenterate-grade, relationships. In the time since that post appeared, the anabaritids have been… Continue reading Anabaritida

Alpheoidea

Belongs within: Caridea.Contains: Synalpheus, Alpheus, Hippolyte. The Alpheoidea are a group of shrimps in which the first pair of pereiopods are distinctly chelate, containing the snapping shrimps (Alpheidae) and cleaner shrimps (Hippolytidae). The first pair of pereiopods in members of this group is well developed; in the snapping shrimps one chela is enlarged and used… Continue reading Alpheoidea

Published
Categorised as Decapoda

Crangonoidea

Belongs within: Caridea. The Crangonoidea are a group of shrimps uniting Glyphocrangon and the Crangonidae. They are distinguished by having the first pair of pereopods prehensile (Glyphocrangon) or subchelate (Crangonidae). A strong toothed rostrum is present in Glyphocrangon but the rostrum is usually small in Crangonidae. Within Crangonidae, the second pereopods are commonly chelate though… Continue reading Crangonoidea

Caridea

Belongs within: Decapoda.Contains: Bresilioidea, Pasiphaeidae, Atyidae, Nematocarcinoidea, Processidae, Alpheoidea, Crangonoidea, Pandalidae, Palaemonidae. The Caridea are one of the main groups of true shrimps (Decapoda). Members of the group have phyllobranchiate gills and chelate first and (usually) second pereiopods, but lack chelae on the third pereiopods. Another potential synapomorphy of the carideans is the ‘caridean lobe’… Continue reading Caridea

Published
Categorised as Decapoda

Reptantia

Belongs within: Decapoda.Contains: Astacidea, Thalassinida, Achelata, Anomala, Brachyura. The Reptantia are the clade of crustaceans containing decapods other than the shrimps, e.g. crabs, lobsters and crayfish. As the name of the group indicates (‘walkers’), reptants are characterised by more robust legs allowing them to walk rather than swim across the surface of the substrate. The… Continue reading Reptantia

Published
Categorised as Decapoda

Astacida

Belongs within: Astacidea.Contains: Cambarus, Procambarus, Orconectes. The Astacida are the freshwater crayfish. They are divisible between the Northern Hemisphere Astacoidea and the Southern Hemisphere Parastacidae (Martin & Davis 2001). In the Astacoidea, the first pleopod is well developed and used for sperm transfer in males but reduced or absent in females, whereas in Parastacidae it… Continue reading Astacida

Published
Categorised as Decapoda

Brachyura

Belongs within: Reptantia.Contains: Heterotremata, Pinnotheridae, Grapsoidea, Ocypodoidea, Raninoida, Homoloidea, Dromioidea, Homolodromioidea. The Brachyura are the true crabs, a group of decapods in which the reduced abdomen is held to the underside of the sternum. Basal relationships within the Brachyura have been contentious. Some authors have supported a division between the Podotremata, in which both males… Continue reading Brachyura

Published
Categorised as Decapoda

Parthenopidae

Belongs within: Heterotremata. The Parthenopidae, elbow crabs or pebble crabs, are a family of tropical and subtropical marine crabs, notable for having particularly long chelipeds relative to the other legs. Most species have a subtriangular body shape, though the Indo-Pacific Lambrachaeus ramifer has the front of the carapace extended forward into a long neck. Crabs… Continue reading Parthenopidae

Xanthidae

Belongs within: Heterotremata. The Xanthidae are a family of marine crabs found from the intertidal zone to moderately deep water. They are often brightly coloured and highly toxic, sometimes even to the touch. Characters (from Davie 2002): Carapace hexagonal, transversely hexagonal to transversely oval, sometimes subcircular; dorsal regions (areolation) generally, but not always, well defined;… Continue reading Xanthidae

Published
Categorised as Decapoda

Trichodactylidae

Belongs within: Heterotremata. The Trichodactylidae are a family of crabs found in rivers and lakes of South America, with some species in Mexico and Nicaragua. Characters (from Rodríguez 1992): Penis lodged in penial groove located across middle of 8th sternite. First male gonopod conical or flask-shaped, with distal portion armed with strong conical spines; gonopore… Continue reading Trichodactylidae

Published
Categorised as Decapoda