Search results for "Ligament structure"

Early oysters and their supposed Permian ancestors

2005

The origin of oysters is a much debated palaeontological issue. Recent morphological studies indicate that oysters are characterized by a particular ribbing pattern, the so-called antimarginal ribs which are characterized by a proper morphogenetic pattern. Therefore antimarginal ribs can be used as a diagnostic character in phylogeny. The earliest recognized bivalve displaying diagnostic features of oysters (sinistral attachment to the substrate, typical hinge and ligament structure, and antimarginal ribs) is Ostracites cristadifformis Schlotheim, 1820 first appearing in the Anisian of Europe. This common species was later attributed to Enantiostreon and is here transferred to Umbrostrea. S…