Retroplumidae is a family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of heterotremata

Heterotremata

Heterotremata is a clade of crabs, comprising those crabs in which the genital openings are on the sternum in females, but on the legs in males. It comprises 68 families in 28...

n crab

Crab

True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...

s, placed in their own (monotypic

Monotypic

In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

) superfamily

Taxonomic rank

In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

, Retroplumoidea.

Classification

Eight genera are recognised, of which all but two are only known from fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

s:

• Archaeopus † Rathbun, 1908
• Bathypluma de Saint Laurent, 1989
• Costacopluma † Collins & Morris, 1975
• Cristipluma † Bishop, 1983a
• Loerentheya † Lőrenthey, in Lőrenthey & Beurlen, 1929
• Loerenthopluma † Beschin, Busulini, De Angeli & Tessier, 1996
• Retrocypoda † Vía, 1959
• Retropluma Gill, 1894

Ten species in two genera survive in the deep sea

Deep sea

The deep sea, or deep layer, is the lowest layer in the ocean, existing below the thermocline and above the seabed, at a depth of 1000 fathoms or more. Little or no light penetrates this part of the ocean and most of the organisms that live there rely for subsistence on falling organic matter...

 of the Indo-Pacific

Indo-Pacific

The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...

 region:

• Bathypluma chuni (Doflein, 1904)
• Bathypluma forficula De Saint Laurent, 1989
• Bathypluma spinifer De Saint Laurent, 1989
• Retropluma denticulata Rathbun, 1932
• Retropluma quadrata De Saint Laurent, 1989
• Retropluma notopus (Alcock & Anderson, 1894)
• Retropluma planiforma Kensley, 1969
• Retropluma plumosa Tesch, 1918
• Retropluma serenei De Saint Laurent, 1989
• Retropluma solomonensis McLay, 2006

Fossil specimens ascribed to the Retroplumidae are known from the Late Cretaceous

Late Cretaceous

The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 onwards, with Archaeopus antennatus in Coniacian

Coniacian

The Coniacian is an age or stage in the geologic timescale. It is a subdivision of the Late Cretaceous epoch or Upper Cretaceous series and spans the time between 89.3 ± 1 Ma and 85.8 ± 0.7 Ma...

–Maastrichtian

Maastrichtian

The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

 rocks in California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 and Archaeopus ezoensis from Turonian

Turonian

The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...

–Maastrichtian rocks from Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

.