Early loop ontogeny of some Recent laqueid brachiopods
Abstract. The early loop ontogenies of nine Recent laqueid species from Japanese waters were examined using scanning electron microscopy. Although juvenile specimens representing certain early loop stages were not available for some species, all the examined species appear to share roughly the same early stages of loop development as described by Richardson (1975). However, some differences and characteristic features exist in the early stages of loop ontogeny, such as the disposition of the septal flanges and presence or absence of septal bifurcation, characters which appear to be invariable at the genus level. A prime example is the case of the affinity between Laqueus and Frenulina, which have occasionally been included in the same subfamily. Inspections of loop morphology of early growth stages, especially of the above characters, indicate that these two genera may not be as closely related as previously thought. Comparison of relative timing of loop development as standardized by shell length reveals some variation within a species, but no major variation among species. Heterochrony is evident in one laqueid species, 'Frenulina' sp., in which adult individuals have a loop of juvenile morphology in other species.
- Transactions and proceedings of the Palaeontological Society of Japan. New series = 日本古生物学会報告・紀事. 新篇
Transactions and proceedings of the Palaeontological Society of Japan. New series = 日本古生物学会報告・紀事. 新篇 (183), 485-499, 1996-09-30