The growth stages of the lophophore of the brachiopods Platidia davidsoni (Eudes Deslongchamps) and P. anomioides (Philippi), with notes on the feeding mechanism

Abstract

(Text-figs. 1-23)The lophophore of Platidia, as illustrated in most memoirs and text-books, bears little resemblance to its appearance in life, no doubt because such illustrations and the accompanying descriptions were based on dried specimens. The lophophore of Platidia has been considered to be of a peculiar sigmoid type, differing from that of any other known lophophore. The dredging by RV. 'Sarsia' of three species of the genus in recent years has afforded the opportunity of figuring the lophophore in its natural state, and the working out of its growth stages in P. davidsoni and P. anomioides: these were previously unknown for any species of Platidia. The third species, a new one, is described separately (Atkins, 1959).Although P. anomioides (Philippi) is the type species of the genus, P. davidsoni (Eudes Deslongchamps) is considered first as it was the first to be dredged by RV. 'Sarsia' and work on it was ready for publication when P. anomioides was obtained in May 1958.All figures have been drawn with the aid of a camera lucida. PLATIDIA DAVIDSONI (EUDES DESLONGCHAMPS)A species of Platidia dredged by R V. 'Sarsia' from off Penmarch and the north coast of Spain is evidently P. davidsoni (E. Deslongchamps) as it agrees with the description of that species by Eudes Deslongchamps (1855) in having 'small spinous asperities' on the outer surface of the ventral valve, although these are often confined to a submarginal zone, and in some individuals apparently worn and indistinguishable. Fischer (1872, 1873) noted of this species that 'elle porte quelquefois des asperites assez nombreuses'. The brachial support agrees with the figures accompanying E. Deslongchamps's paper, but not with his description. There appears to be some confusion over its actual state. In his description of his new species, Morrisia ( = Platidia) davidsoni, E. Deslongchamps (1855) described the' apophysary system consisting of two lamellae originating at the base of the sockets, and

The Evolution of Brachiopoda

“…The relationship between evolution and development has long been a focus of attention among brachiopod workers, from Beecher (1891) to Atkins (1959) to Jaecks & Carlson (2001). The evolutionary consequences of changes in developmental rate and timing, referred to as heterochrony (Haeckel 1875, Alberch et al 1979, can result in paedomorphic or peramorphic patterns of evolutionary change.…”

A new species and genus of Brachiopoda from the western approaches, and the growth stages of the lophophore

“…The ciliary feeding mechanism is as described for M. cranium by Atkins, (1956). In large living specimens the valves may gape anteriorly as much as 6mm.…”

The early growth stages and adult structure of the lophophore of Macandrevia cranium (Müller) (Brachiopoda, Dallinidae)

“…The ciliary feeding mechanism of M. cranium has been briefly described (Atkins, 1956) and it is intended to publish a full account separately.…”