Аннотация:Brachiopods of the order Strophomenida (Rhynchonelliformea) often have two
openings in the posterior part of the shell: between valves in the middle of area and apical
foramen or tube (pedicle sheath) on the umbo of ventral valve. The latter is generally
supposed to accommodate peduncular outgrowth. We studied first representatives of
the order Strophomenida from the Ordovician of Leningrad Region with pedicle sheath
located within first-formed region of ventral valve and shaped as thin hollow outgrowth
with inner diameter of 20-30 μm at the apex. The gap between the valves, which is used as
pedicle opening in articulated brachiopods, is absent at juvenile stages and develops later
in the ontogeny, that testifies to the presence of well developed pedicle in strophomenid
ancestors. According to C. Nielsen, the ancestor of brachiopods folded on ventral side and
their dorsal and ventral valves in fact are both dorsal. Therefore the anus of brachiopods
initially should be located on ventral side and the pedicle sheath may be interpreted as
tubular outgrowth of the ventral valve accommodating anal papilla. The anus of recent
brachiopods is never ventrally located. However, possible homologue of pedicle sheath of
fossil strophomenids is the pedicle of recent discinids shaped as outgrowth of soft tissues
in the aperture within the ventral valve. Natively this outgrowth was anal papilla, but
later anus moved to the right side of the body and ventral outgrowth transformed into
anchoring organ. We suppose that discinid pedicle is not homologous to the pedicle of
lingulids and Rhynchonelliformea.