A Critique On Recent Concepts of Growth in Balanomorpha (Cirripedia, Thoracica)

Shell structure and shell strength in Cirripedes

“…Some of the easily recognisable shell features which contribute to its strength are the thickness of wall plates (Bourget 1977), plate porosity which arrests crack growth (Barnes et al 1970), ridges or crenulations on plates (Murdock and Currey 1978), interlocking between parietes and base (Newman et al 1967;Murdock and Currey 1978) and the cuticle covering the shell plates (Parke and Moore 1935;Bonar 1936;Newman and Ross 1971). Besides these the strengthening of the plates by interspacing of organic tissue in the matrix of shell is also known to contribute to shell strength (Newman et al 1967).…”

“…Besides these the strengthening of the plates by interspacing of organic tissue in the matrix of shell is also known to contribute to shell strength (Newman et al 1967). Gubbay (1983) divided 7 temperate species into 3 groups viz.…”

A Carboniferous Pedunculate Barnacle

“…The relatively poor fossil record of the lepadids suggests that calcification may not have evolved in this group until late in the Mesozoic. The problematic Silurian Cyprilepas holmi has been associated by Newman et al (1969) with the hypothetical bivalved ancestral group from which the lepadids are believed to have evolved. However, even if this species is a cirripede, it might equally represent a cyprid larval stage as originally suggested by Wills (1962Wills ( , 1963 or might be more closely associated with the acrothoracic cirripedes.…”

“…families Scalpellidae (U. Trias-Recent), Stramentidae (Cretaceous) and Heteralepadidae (Recent) and from which the various suborders of sessile thoracic barnacles are believed to be derived (Newman et al 1969). The scalpellids characteristically have armoured peduncles and appear to have as a fundamental feature the six capitular plates believed to be present in Pabulum.…”

“…This would appear to be a further primitive feature which is not found in any other scalpellid except the two recent genera of the Heteralepadidae where there has probably been a secondary loss of the calcareous armature of both the capitulum and the peduncle. In the Upper Jurassic a number of new scalpellid genera appear and form a rather heterogeneous group consisting of the six plated Archaeolepas and the thirty-four plated £eugmatolepas together with possible fragmentary representatives of Calantica {Calantica) (14 plates), C. (Scillaelepas) (12 plates) and Pollicipes (18+ plates) (Newman et al 1969;Withers 1928). Comparison between these genera and Pabulum is to some extent limited as of the capitular valves in Pabulum only the characters of the scuta can be well defined.…”