Shell-Form in the Lamellibranchia

Constraints in the ligament ontogeny and evolution of pteriomorphian Bivalvia

“…But, as most other studies, it ignores the early phases of ligament ontogeny when important changes occur (exceptions include Bernard 1898;Waller 1990;2004). Also, the relation between shell growth and ligament growth patterns has only been addressed in a small number of bivalve taxa (Owen 1953;Yonge 1967;Skelton 1978). This paper sets out to document the close correlation between ligament and general growth pattern in pteriomorphian bivalves and proposes a hypothesis on the underlying mechanisms.…”

On the Nature and Definition of the Lunule, Escutcheon and Corcelet in the Bivalvia

“…The absolute magnitude of the spiral angle of non-directive spirals is determined by the fact that their projection into the directive plane must have the same spiral angle as the spiral of the directive plane. Because of this, the further away laterally a sector of shell growth is from the directive plane, the more markedly turbinate it is, and hence the more marked is the apparent 'tangential growth component' of the shell (Owen, 1953). Thus, given models of shell shape which are identical apart from the angle that the directive plane makes with the commissure (defined as 0 by Lison), the shape of the lunule will be controlled by this angle.…”

Anatomy of Phyllodina persica (Bivalvia: Tellinidae), and its first occurrence in southeastern Brazilian waters

“…Many of the internal anatomical features of P. persica are similar to others tellinids, such as a dorso-ventral elongated anterior adductor muscle, a long pair of siphons associated to a broad siphonal muscle extending, at least, to the half shell, a large palp with same size (or larger) than the gills, and a broad gastric shield. These general features have been described as representatives of Macominae and Tellininae (Yonge, 1949;Owen, 1953;Franc;1960;Bright & Ellis, 1989;Gilbert, 1977;Beukema & Meehan, 1985;Barón & Ciocco, 1997;Simone & Wilkinson, 2008) that appear to be a set of stable characters within the Tellinidae, which may be considered synapomorphies of this family (Simone & Wilkinson, 2008). P. persica presents two noteworthy characters that seem to be constant through subfamily Tellininae: an outer demibranch with a single lamellae and a pericardial region with no recovering outer demibranch.…”