Curviacus

Curviacus is a genus of Ediacaran organism of uncertain lineage that displays a modular body plan consisting of crescent-shaped chambers. It contains a single species, Curviacus ediacaranus.

Curviacus
Scientific classification
Kingdom:	Animalia
Phylum:	incertae sedis
Order:	†Palaeopascichnida
Genus:	†Curviacus Shen, Xiao, Zhou, Dong, Chang & Chen, 2017
Species:	†C. ediacaranus
Binomial name
†Curviacus ediacaranus Shen, Xiao, Zhou, Dong, Chang & Chen, 2017

Etymology

The genus name Curviacus references the shape of the crescent chambers; coming from Latin curvus meaning curved and acus meaning needle.^[1]

Phylogeny

The phylogeny of this fossil is not yet known. Some scientists believe the genus to be a coralline algal or fungal stem group.^[1]

Occurrence

C. ediacaranus is from the late Ediacaran. The fossil C. ediacaranus has been found in the Shibantan Member of the Dengying Formation.^[1] The Shibantan Member is the bituminous limestone section of the formation.^[2] It is unusual for Ediacaran biota to be preserved in limestone. As such, C. ediacaranus is the only Palaeopascichnus fossil to be reported from carbonate rock rather than siliclastic rock.^[1] This special type of fossilization allows for 3-dimensional analysis.^[1]

Description

These fossils occur on bituminous limestone on the bedding surface. The fossilized specimen has calcispar walls with the inner chambers filled with micrite.^[1] The walls are raised because the calcispar does not erode as easily. C. ediacaranus is a slightly oblong macrofossil that ranges from 5–14 cm in length. It is characterized by its curved or crescent-shaped chambers that occur arranged in a series with the chambers sharing walls. All of the chambers are convex in the same direction. Each chamber is narrow ranging ~1-3mm in width. Chamber length can be consistent or inconsistent. Inconsistencies can give a false impression of branching.^[1] Additionally, the walls of the chambers sometimes converge laterally.