The jaw apparatus of the regular echinoids is moved by a complex of muscles. Of these the largest and most accessible are the lantern retractor muscles which originate on the auricles and insert upon the pyramids which enclose the teeth. Preliminary experiments using Parechinus angulosus Mortensen showed that, while in this species these muscles could not be stimulated indirectly by way of elec...

Evolutionary radiations are fascinating phenomena corresponding to a dramatic diversification of taxa and a burst of cladogenesis over short periods of time. Most evolutionary radiations have long been regarded as adaptive but this has seldom been demonstrated with large-scale comparative datasets including fossil data. Originating in the Early Jurassic, irregular echinoids are emblematic of th...

The regular echinoids were recorded from Chennai Coast,Tamilnadu, South India and the animals were belong to 4 families, 5 genera and 5 species. An identification key to generic level and synoptic description are provided. Temnopleurid sea urchin Salmaciella oligopora (Clark, 1916) was recorded for the first time in 20-30m depth between Chennai and Pondicherry Coasts, South East Coast of India....

Echinoids (sea urchins) are divided into twomajor groups – cidaroids (a ‘primitive’group)andeuechinoids (a ‘derived’group).Thecidaroidsarea promisingmodelspecies for understanding theancestral developmental mechanisms in echinoids, but little is known about the molecular mechanisms of cidaroid development. In euechinoids, skeletogenic mesenchyme cell specification is regulated by the double-neg...

Echinoids (sea urchins) are divided into twomajor groups – cidaroids (a ‘primitive’group)andeuechinoids (a ‘derived’group).Thecidaroidsarea promisingmodelspecies for understanding theancestral developmental mechanisms in echinoids, but little is known about the molecular mechanisms of cidaroid development. In euechinoids, skeletogenic mesenchyme cell specification is regulated by the double-neg...