Decoritheca Sysoyev, 1972

Sun, Haijing, Malinky, John M., Zhu, Maoyan & Huang, Diying, 2018, Palaeobiology of orthothecide hyoliths from the Cambrian Manto Formation of Hebei Province, North China, Acta Palaeontologica Polonica 63 (1), pp. 87-101 : 90

Genus Decoritheca Sysoyev, 1972

Type species: Hyolithus (Orthotheca) excavatus Holm, 1893 ; middle Cambrian , Sweden .

Diagnosis. —See Berg-Madsen and Malinky (1999). Remarks.— Decoritheca is morphologically similar to Contitheca Sysoyev, 1958 , but they are separated by the prominent ridge present on the dorsum of the latter, giving rise to a heart-shaped cross section. The former possesses a rounded dorsum and lacks the middle dorsal ridge, creating a reniform cross section. Specimens described herein match well the traits of Decoritheca and are therefore assigned to that genus. Decoritheca also resembles Nephrotheca Marek, 1966 in cross section, but differs from the latter in solely having transverse lines ( Malinky 1987), although, to some degree, ornamentation may not be the best criterion to differentiate taxon ranking above species. So far no operculum for Decoritheca has been documented. Decoritheca cyrene was described from the “middle Cambrian” (Cambrian Series 3) Changhsia Formation and the “upper Cambrian” (Cambrian Furongian) Chaomitien Formation (Walcott 1905; Malinky 1987); the long span of the species may also reflect a taxonomic problem. Until better fossil material is available to address the relationship between Nephrotheca , Decoritheca , and some other similar taxa, specimens described below are provisionally placed under Decoritheca .

Stratigraphic and geographic range.—Cambrian Series 2 Stage 3 to Furongian Stage 10. Distributed in China, Greenland, Sweden, British Columbia, Texas, Montana, possibly South Dakota, and New York State ( Malinky 1987; 1990; 2014; see also SOM 2).