WebNov 1, 2014 · Based on the sister-group relationships and ontogeny of modern species and new fossil discoveries, we now know that the first echinoderms were bilaterally symmetrical, represented in the fossil... WebEchinoderms evolved from bilaterally symmetric animals exhibiting fivefold radial symmetry in portions of their body at some stage of life. This pentameral symmetry is readily apparent in familiar adult starfish and …
Evolution of the chordate body plan: New insights from ... - PNAS
WebMar 9, 2024 · The degree of phylogenetic resolution in early fossil ambulacrarians is still in its infancy, but the information presented 1 does give a glimpse of what may be evolving in a concerted manner in... WebJan 22, 2013 · of echinoderm represen t the primitive echinoderm bod ... implying that the so‐called Cambrian substrate revolution was not a strong control on the early evolution of attachment in echinoderms. ... is hyannis nice
Echinoderm - Wikipedia
WebApr 10, 2024 · Another puzzle related to echinoderm evolution is how and why these organisms acquired their distinctive radial body plan. Among animals,all but the most primitive have bilateral symmetry-the left sides of their bodies are roughly mirror images of the right sides. Two main groups of animals have radial symmetry instead. WebJul 21, 2024 · Echinoderms underwent a major two-part radiation that produced all of the major groups found in the fossil record between the Early Cambrian and the Middle Ordovician. A small initial radiation in the Early and Middle Cambrian produced about nine classes containing low-diversity members of the Cambrian Evolutionary Fauna. WebMany scientists maintain that chordates originated sometime earlier than 590 million years ago; that is, they predate the fossil record. Such early representatives were soft-bodied and therefore left a poor fossil record. The oldest known fossil chordate is Pikaia gracilens, a primitive cephalochordate dated to approximately 505 million years ago. is hyaluronic acid good for your face