Original paper

On the early evolution (Late Triassic to Late Jurassic) of the Architectibranchia (Gastropoda: Heterobranchia), with a provisional classification

Gründel, Joachim; Nützel, Alexander


At least since the Late Triassic, Architectibranchia or "lower Heterobranchia" form an important component of marine gastropod faunas. Traditionally, such gastropods were also attributed to shelled opisthobranchs. In this paper, more than 160 Mesozoic, mostly Jurassic architectibranch species are classified in 5 families and 21 genera. The position of the problematic genus Acteonina d'Orbigny, 1850 based on a Palaeozoic type species is discussed and its heterobranch status could not be undoubtedly confirmed. For all genera, emended diagnoses are given based on re-evaluations of their type species. Moreover, the generic assignments of numerous species are changed. However, for many species several important shell characters are unknown, e. g., protoconch morphology or apertural features. Therefore, numerous previously described species cannot be assigned to genera with certainty and as a consequence, the duration of genera and families as well as the phylogenetic conclusions provided herein remain tentative. Cylindrobullinidae and Tubiferidae originate as early as Triassic. The oldest known genus is Sinuarbullina (Tubiferidae, Early Triassic). At least 6 genera representing both families cross the Triassic/Jurassic boundary. A distinct radiation of cylindrobullinids and tubiferids occurs in the Early to Middle Jurassic time interval. Bullinidae originate in the Early Jurassic. The bullinid Sulcoactaeon is a long ranging genus with a large number of species. Acteonidae and Ringiculidae are known since the Middle Jurassic but have their radiations in post-Jurassic times. The genera Sinespirites, Domerionina and Cossmannina are described as new. The name Cylindrites Morris & Lycett, 1851 is replaced by the name Rugalindrites nom. nov.