Gastropod radulae and the assessment of form in evolutionary paleontology

Abstract

Evolutionary paleontologists seek explanations of form and pattern in a diversity of contexts. A review of this diversity is presented to underscore the difficulty of producing a general model of the factors controlling the morphology of real organisms. A model specific to the marine prosobranch gastropod radula identifies seven factors contributing to form and pattern: (1) phylogenetic, (2) mechanical, (3) ecological, (4) programmatic, (5) maturational, (6) degenerative, and (7) constructional. Aspects of radular morphology attributable to each factor are illustrated in scanning electron micrographs of radulae of marine prosobranch gastropods. Applications of and extrapolations from the radular model are made to promote recognition of a broader range of interacting factors in other systems. Some aspects of form and pattern convey important information about non-evolutionary processes and phenomena and are best examined outside of the evolutionary framework.

Relationships of the Triassic Eucycloidea Koken, 1897 (Mollusca, Gastropoda) to modern genera such as Pagodatrochus, Calliotropis and Euchelus, based on morphology of the early shell

“…8;2009, pl. 9, figs 127-129) and Hickman (1980). The number of the marginal teeth varies among species.…”

Groping through the black box of variability: An integrative taxonomic and nomenclatural re-evaluation of Zospeum isselianum Pollonera, 1887 and allied species using new imaging technology (Nano-CT, SEM), conchological, histological and molecular data (Ellobioidea, Carychiidae)

“…Diverse considerations along a second line of this study involve ecological aspects such as the relationship between tooth cusps and substrates, producing adaptive moderations of morphological detail. Mechanical factors such as forces acting on teeth during feeding produce adaptive solutions to pressure, such as development of compressional ridges (Hickman 1980). Moreover, the cusp of the tooth interacts with the substrate during feeding and is vulnerable to substrate characteristics and dietary preferences (Hickman 1980;Luchtel et al 1997).…”

“…Mechanical factors such as forces acting on teeth during feeding produce adaptive solutions to pressure, such as development of compressional ridges (Hickman 1980). Moreover, the cusp of the tooth interacts with the substrate during feeding and is vulnerable to substrate characteristics and dietary preferences (Hickman 1980;Luchtel et al 1997). Consequently, if tooth cusps are to most effectively function with the fine nuances of substrate composition and configuration (i.e.…”

Mouthparts of the Burgess Shale fossils Odontogriphus and Wiwaxia : implications for the ancestral molluscan radula

“…(d) Radula and ecology The diet of many molluscs is constrained by radular morphology [25], but radulae can also adapt to available food sources-either by plasticity [26] or natural selection [27]. Accordingly, the radula provides a rich ecological signal.…”