Glossary of Morphological and Anatomical Terms
oblique muscles - Variable sets of muscles in inarticulated brachiopods responsible for rotational and longitudinal movements of valves.Fig.374.
occlusor muscle - See adductor muscle.
oligopalmate - Mantle canal system with two pairs of principal canals in each mantle.
opercular - Lidlike valve.
opposite folding - Folding in which fold or sulcus in one valve is opposed by fold or sulcus in other; commissure remaining rectimarginate.Fig.288.
ornament - Any regularly occurring outgrowth, deflection or nonpathological interruption in growth(other than growth lines) found on outer shell surface.
ornithellid stage - See carinate.
orthoconate - Brachia coiled parallel with plane of commissure.
orthomorph - Chonetoid hinge spines remaining straight, perpendicular, oblique, or parallel to hinge line.
outer hinge plates - Pair of concave or subhorizontal plates in cardinalia separating inner socket ridges and crural bases.Fig.329,Fig.330,Fig.331.
outer mantle lobe - Outer peripheral part of mantle separated by mantle groove from inner lobe; in articulated brachiopods responsible for secretion of periostracum and part or all of primary shell layer.Fig.3.
outer plates - Pair of subvertical plates in pentameroid cardinalia with ventral surface fused to base of brachial process and dorsal edge attached to floor of valve or rarely, septal plate homologue of crural plates or inner hinge plates.Fig.329_9.
outer socket ridge - Low ridge bounding dental socket on outer lateral or posterior side of dorsal valve.Fig.322,Fig.331.
outside lateral muscles - Pair of muscles in some lingulides that originates on ventral valve lateral of centrals and extends posteriorly to insertions behind middle lateral muscles on dorsal valve.Fig.377.
ovarian impression - See genital marking.
ovarian marking - See genital marking.
