Each segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion. Septa separate the segments of many species, but are poorly defined or absent in others, and Echiura and Sipuncula show no obvious signs of segmentation.ach segment has the same sets of organs and, in most polychaetes, has a pair of parapodia that many species use for locomotion. Septa separate the segments of many species, but are poorly defined or absent in others, and Echiura and Sipuncula show no obvious signs of segmentation.
Chicxulub is most famous for being near the geographic center of the Chicxulub crater, an impact crater discovered by geologists on the YucatÃ¡n Peninsula and extending into the ocean. It was created by the impact some 65 million years ago of the Chicxulub impactor, an asteroid or comet which caused the CretaceousâPaleogene extinction event, which led to the demise of the dinosaurs.
Its center is located near the town of Chicxulub, after which the crater is named. The date of the Chicxulub impactor, which created it, coincides precisely with the CretaceousâPaleogene boundary (KâPg boundary).he crater was discovered by Antonio Camargo and Glen Penfield, geophysicists who had been looking for petroleum in the Yucatan yucatÃ¡n during the late. 1970s