Which of the following is true of the evolution of animal phyla and animal body plans The majority of animal body plans and phyla evolved over a comparatively short timespan in the Cretaceous period around 200 million years ago in an event paleontologists call the Cretaceous Explosion Animal body plans show a slow but constant progression with new body plans and new phyla evolving since the Proterozoic Era 2 5 billion years ago until relative recent times Animal body plans and phyla diversified during the Jurassic period and through the Cretaceous period from around 200 million years ago until 65 million years ago when the Cretaceous Paleogene extinction event halted their progress The majority of animal body plans and phyla evolved over a comparatively short timespan in the Cambrian period around 540 million years ago in an event paleontologists call the Cambrian Explosion 1 point Many protostomes appear quite similar at first glance with several groups exhibiting worm like morphology However this superficial similarity can be misleading as worms are present in both major groups of protostome the lophotrochozoa and the ecdysozoa Which of the following features is most likely to be present in a segmented worm a lophotrochozoan and absent in a round worm an ecdysozoan spiral cleavage during development the blastopore develops into the anus during gastrulation the blastopore develops into the mouth during gastrulation radial cleavage during development 03