DELAWARELLA Collignon, 1948

Ifrim, Christina & Stinnesbeck, Wolfgang, 2021, Ammonoids and their biozonation across the Santonian-Campanian boundary in north-eastern Coahuila, Mexico, Palaeontologia Electronica (a 34) 24 (3), pp. 1-62 : 8

Subgenus DELAWARELLA Collignon, 1948

Many species described below were earlier included into Submortoniceras based on quinquetuberculation seen in lower Campanian Texanitinae from Texas, at least during part of their ontogeny, while other species were based on juveniles. However, Submortoniceras is based on the South African Mortoniceras woodsi Spath, 1921 . This taxon defined by Spath (1926) was interpreted to have evolved from Texanites soutoni soutoni in South Africa at about the Santonian-Campanian boundary, there producing a large number of endemic species ( Klinger and Kennedy, 1980). Menabites (Delawarella) tequesquitense ( Morton, 1830) , on the other hand, was interpreted to have evolved during the late Santonian from Plesioexanites shiloensis ( Young, 1963) , or alternatively, from the South African soutoni lineage ( Klinger and Kennedy, 1980); it cannot be assigned to the younger South African genus Submortoniceras . In the North American Menabites (Delawarelly) group two lineages are distinguished: M. (D.) tequesquitense gave rise to the tequesquitense – delawarensis – danei lineage. The proximity between early Campanian Texanitinae from Texas and South Africa suggests a close relationship. The other lineage departs from M. (D.) vanuxemi giving rise to M. (D.) mariscalense and M. (D.) uddeni ( Young, 1963) and some more compressed species of this genus endemic to Texas. They are here all included into Menabites (Delawarella) .