A phylogenetic lineage of Myophoria kefersteini subspecies (Bivalvia) from the Late Ladinian to the Early Carnian (Triassic) in the Dolomites and Julian Alps (Italy)
published: Nov 1, 2014
ArtNo. ESP155027402005, Price: 29.00 €
Myophoria kefersteini gornensis, M. kefersteini okeni, and M. kefersteini kefersteini represent subsequent members of a phylogenetic lineage ranging from the early Regoledanus Zone (Late Ladinian, Middle Triassic) to the Austriacum Zone (Early Carnian, Late Triassic) of the Dolomites and Julian Alps (Italy). This lineage is characterized by an increasing number of radial ribs on the anterior shell region of the right valve, increased strength of the ornamentation, and a shifting of the beak to the anterior shell region from one third to one quarter length. Furthermore, it is characterized by a change from a rounded-triangular to an oblique-triangular lateral valve outline and by a change from an acute to an obtuse angle between the flank and the area. The size of Myophoria kefersteini is reduced in restricted marine environments, as in the Pordoi Formation (Austriacum Zone) of the Sella and Gardenazza (Dolomites) and in the Bleiglanzbank (lower Grabfeld Formation = lower Germanic Gipskeuper) of Wurttemberg. Based on the occurrence of Myophoria kefersteini gornensis, the age of the Bleiglanzbank corresponds to the early Regoledanus Zone (Late Ladinian).