Rotadiscus

For the genus of snails, see Rotadiscus (gastropod).

Rotadiscus is a genus of discoidal animal known from the Cambrian Chengjiang biota^[3] and classified with the eldonioids.^[2]

Rotadiscus Temporal range: Early Cambrian – Middle Cambrian[1] PreꞒ Ꞓ O S D C P T J K Pg N
Fossil of Rotadiscus
Scientific classification
Kingdom:	Animalia
Stem group:	Ambulacraria
Clade:	†Cambroernida
Class:	†Eldonioidea
Family:	†Rotadiscidae
Genus:	†Rotadiscus Sun & Hou, 1987
Type species
R. grandis Sun & Hou, 1987
Synonyms[2]
Brzechowia Dzik, 1991

As with other eldonioids, it was originally thought to have been pelagic, but is now thought to be benthic.^[4]

In addition to the type species R. grandis, two other Rotadiscus species have been proposed. The first is known only from one complete juvenile specimen and a few fragments, and was originally described as "Brzechowia sp." It remains without a formal species name, but has been transferred to Rotadiscus.^[5] The species initially described as R. guizhouensis has since been reassigned to the genus Pararotadiscus.^[2]

A 2023 cladistic analysis based on new fossils places Rotadiscus, along with other eldonioids, as stem-group ambulacrarians in the clade Cambroernida.^[6]