Omalacantha

Omalacantha
Speck-claw Decorator Crab, top view
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Decapoda
Suborder:	Pleocyemata
Infraorder:	Brachyura
Family:	Mithracidae
Genus:	Omalacantha Streets, 1871
Type species
Omalacantha hirsuta Streets, 1871
Synonyms [1]
MilniaStimpson, 1860

Omalacantha is a genus in the family of crustaceans known as the Mithracidae

Description

Species in the genus Omalacantha display these features:

• Their carapaces are longer than wide, and pear shaped.
• Their tops are rough with graininess, tubercles and patches of hooked bristles, or setae.
• Rostrums have two strong, slightly downward-curving horns, and two rows of hooked setae along their entire lengths.
• The antennae's basal segments are very broad, forming floors for the depressions (the orbits) from which the eye-bearing stalks protrude
• Above each orbit there's a strong spine.
• Walking legs decrease in size from font to rear, and their segments are varyingly covered with setae. ^[2]

Distribution

The GBIF map showing locations of georeferenced records of species of Omalacantha indicate that members of the genus naturally occur in western Atlantic and Gulf of Mexico waters from about the US state of North Carolina south to southern Brazil. ^[3]

Phylogeny

Genetic analysis of species of the superfamily Majoidea of the family Mithracidae found that the genus Omalacantha grouped in the same clade as the genus Microphrys, with which it is very similar morphologically, and that that clade was sister to the genus Teleophrys. It also confimed that Omalacantha can stand as a valid genus. ^[4]

Species

Omalacantha comprised the following species as of 2025: ^[5]

• Omalacantha antillensis Rathbun
• Omalacantha bicornuta ( Latreille, 1825)
• Omalacantha interrupta Rathbun

References

1. "Omalacantha Streets, 1871)". Catalogue of Life. Retrieved November 19, 2025.
2. Windsor, Amanda M.; Felder, Darryl L. (2014). "Molecular phylogenetics and taxonomic reanalysis of the family Mithracidae MacLeay (Decapoda : Brachyura : Majoidea) Molecular phylogenetics and taxonomic reanalysis of the family Mithracidae MacLeay (Decapoda : Brachyura : Majoidea)" (PDF). Invertebrate Systematics. 28. Victoria, Australia: CSIRO Publishing: 145–173. doi:10.1071/IS13011 . Retrieved November 21, 2025.
3. "Omalacantha Streets, 1871". gbif.org. Global Biodiversity Information Facility. Retrieved November 20, 2025.
4. Sancho-Blanco, Carolina; Salas-Arce, Luis E.; Alfaro-Montoya, Jorge; Vargas-Castillo, Rita; Baeza, Juan Antonio; Umaña-Castro, Rodolfo (January–December 2022). "Distribución, riqueza e identificación molecular de cangrejos araña (Brachyura: Majoidea: Mithracidae) de Costa Rica" (PDF). Uniciencia (in Spanish, English, and Portuguese). 36 (1). Costa Rica: Editorial Universdad Nacional/ Universidad Nacional Costa Rica: 1–15. doi:10.15359/ru.36-1.18.
5. "Search Results for Omalacantha". catalogueoflife.org. Catalogue of Life. Retrieved November 20, 2025.