Rhombocorniculum

Rhombocorniculum Temporal range:
Scientific classification
Kingdom:	Animalia
Clade:	Panarthropoda
Phylum:	†Lobopodia
Family:	†Hallucigeniidae
Genus:	†Rhombocorniculum Walliser, 1958

Rhombocorniculum is a species of small shelly fossil comprising twisted ornamented cones. It has been described from the Comley Limestone and elsewhere. R. cancellatum straddles the Atdabanian/Botomian boundary. The structure of its inner layer suggests that its phosphatic fibres formed within a flexible organic matrix.

Description

Three species are recognized — in stratigraphic succession: R. insolutum, R. cancellatum (=R. walliseri), and R. spinosus (=Rushtonites spinosus). Landing (1995) refers R. insolutum to the strictocorniculids, along with Rushtonites. Hinz (1987) considers insolutum to fall within the variability seen in cancellatum.

Classification

Based on details of the ornament and construction, Rhombocorniculum is interpreted as the spines of a Hallucigenia-like lobopodian worm.

The slightly simplified cladogram below is from a paper by Knecht et al. redescribing the lobopodian Palaeocampa anthrax.

†Diania †Lenisambulatrix †Paucipodia †Thanahita †Eoconchariidae †Microdictyon †Fusuchoncharium †Quadratapora †Xenusion †Onychodictyon †Strictocorniculum †Rhombocorniculum †Orstenotubulus †Carbotubulus †Hallucigenia fortis †Hallucigenia sparsa †"Hallucigenia" hongmeia †Cardiodictyon Tardigrada (tardigrades) †Luolishaniida †Ovatiovermis †Facivermis †Luolishania †Collinsovermidae †EBS Collinsovermid (SAM P14848) †Acinocricus †Collinsovermis †Collinsium †Entothyreos †Aysheaiidae †Aysheaia Soom Shale lobopodian (C1947) †Hadranax †Palaeocampa Antennopoda †Antennacanthopodia Onychophora †Antennipatus †Cretoperipatus †Helenodora Living onychophorans (velvet worms) †Siberiidae †Siberion †Megadictyon †Jianshanopodia †Pambdelurion †Kerygmachelidae †Opabiniidae †Radiodonta (e.g. Anomalocaris) Deuteropoda (modern arthropods)

See also

• Mongolitubulus