We explore numerically the formation of Turing patterns in a confined circular domain with small aspect ratio. Our results show that stable fivefold patterns are formed over a well defined range of disk sizes, offering a possible mechanism for inducing the fivefold symmetry observed in early development of regular echinoids. Using this pattern as a seed, more complex biological structures can b...

two new species of an arbacioid echinoid, genus goniopygus, are reported for the first time from aptiansediments of baghin area, kerman, iran. the main features of the species lie in apical disc and peristomediameter. in goniopygus triangularis sp. nov., the periperoct is triangular in shape with three small, sunkentubercles, located alternatively adjacent to the periperoct, while goniopygus an...

Heterochrony has become a central organizing concept relating development and evolution. Unfortunately, the standard definition of heterochrony--evolutionary change in the rate or timing of developmental processes--is so broad as to apply to any case of phenotypic evolution. Conversely, the standard classes of heterochrony only accurately describe a small subset of the possible ways that ontoge...