Deckeroceras Foerste, 1935a

Kröger, Björn, 2025, The Lyckholm acme of cephalopods - Review of the late Katian (Vormsi-Pirgu regional stages) Ordovician cephalopods of Estonia, European Journal of Taxonomy 978, pp. 1-169 : 93-94

Genus Deckeroceras Foerste, 1935a

Type species

Deckeroceras adaense Foerste, 1935a , from Ada, Pontotoc County, Oklahoma, USA, lower Fernvale Formation, late Katian; by original designation.

Diagnosis

Strongly exogastrically curved conch with nearly circular cross section, becoming depressed at the aperture of the mature body chamber; broad and shallow hyponomic sinus; siphuncle positioned near venter but not marginal; siphuncular segments nearly tubular, slightly contracted near septal foramens. (Adopted from Foerste 1935a: 93.)

Remarks

The sutures of this genus have been described as having a ventral sutural lobe in a previous genus diagnosis ( Flower 1943a: 262; Sweet 1964a: K382). This is erroneous. In the original diagnosis, a ventral sutural lobe is not mentioned ( Foerste 1935a: 92) and in the description of the type of the genus, the sutures are described as follows: “The sutures of the septa curve only slightly downward laterally, both the dorsal and ventral margins reaching about the same level transversely” ( Foerste 1935a: 93). “Downward” here probably refers as directed toward the apex, and thus, Foerste (1935a) described a shallow lateral lobe instead of a ventral lobe in Deckeroceras . The phrase “curve downward” in ( Foerste 1935a: 93) could also refer to the distal ends of the lateral suture. This issue can only be definitely resolved by revisiting the type material, which is beyond the scope of this work. Deckeroceras has been placed within the Apsidoceratidae by Flower (1943a) and Sweet (1964a: K382) without explicit justification. A classification of this genus is equally possible within the Uranoceratidae (based on the family diagnosis given in Sweet 1964a: K374). Here, Deckeroceras is provisionally placed within the Uranoceratidae , to emphasize the similarity of this genus with Warburgoceras Kröger, 2013 and its relation to the early evolution of the Ascocerida (see discussion in Kröger 2013: 83, 100).