Middle Triassic juvenile terebratulids Angustothyris angustaefortmis (Boeckh) from the Żebrak borehole, eastern Poland

Abstract

Four early early stage of brachidium development are recognizable in juvenile terebratulids attributable to the species Angustothyris angustaeformis (Bgeckh) from the Middle Triassic (Lower Muschelkalk) pierced by the Żebrak borehole, podlasie region, viz.: (1) precentronelliform, (2) centronelliform, (3) close to quasipremagadiniform and (4) close to quasimagadiniform.