Probillingsites Foerste, 1928

Kröger, Björn, 2013, The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden, European Journal of Taxonomy 41, pp. 1-110 : 86-87

Genus Probillingsites Foerste, 1928

Type species

Probillingsites welleri Foerste, 1928 , Wisconsin, USA; probably Galena Dolomite, early-mid Katian, Ordovician; by original designation.

Emended diagnosis

Cyrtocones with truncated conch; mature conch inflated, higher than long or height similar to length; conch cross section circular to depressed; mature sutures generally oblique and slightly sinuous or sigmoid, but not lacunose; septal necks in latest septa strongly recumbent, cyrtochoanitic, in earlier septa suborthocoanitic; siphuncular segments expanded.

Remarks

The morphology of Probillingsites scandinavicum sp. nov. indicates that the concept of Probillingsites requires adjustment as it is transitional between Redpathoceras and typical Probillingsites . In fact, the distinction between Redpathoceras and Probillingsites must be drawn relatively arbitrarily at the tenuous border between a mature body chamber characterized as “strongly inflated” ( Probillingsites ) or “inflated” ( Redpathoceras ), or between a mature truncated conch that is “obese” ( Probillingsites ) or breviconic ( Redpathoceras ). The ratio of the height/length of the mature conch may be used as a quantitative measure to distinguish between the two genera. In Redpathoceras clarki Flower, 1963 , the type of Redpathoceras , this ratio is 0.48 and in R. magum sp. nov. and R. bullatum it is 0.46; in typical Probillingsites the height is greater than or equal to the length. In P. scandinavicum sp. nov. this ratio is 0.52. Consequently, here Probillingsites is restricted to Probillingsitidae with conch heights that are greater than or equal to the mature conch length.