The linguliform brachiopod Discinisca in the Lower Jurassic Charmouth Mudstone Formation of Dorset and Alum Shale Member of Yorkshire

摘要

SUMMARY: New, well-preserved examples of the linguliform brachiopod Discinisca holdeni are reported from the Belemnite Marl and Green Ammonite members of the Lower Jurassic Charmouth Mudstone Formation, near Golden Cap, Dorset: Five specimens are attached to ammonites; two are attached to Tragophylloceras numismale and one plus another two possible specimens to Polymor-phites evolutus. Three specimens are attached to a rhynchonellid. brachiopod Scalpellirhynchia scalpellurr In addition, Discinisca infra-oolithica is described attached to the ammonite Dactylioceras cf. athleticum from the Alum Shale Member of the Whitby Mudstone Formation of Yorkshire. An example of D. infraoolithica attached to the bivalve Dacryomya reveals previously unreported fine curved ridges on the pedicle valve. Discinisca spp. probably attached to the ammonite shells post mortem, but might have been attached to the rhynchonellid and bivalve when the latter were alive.