Cambrian Explosion: a whole nervous system (Introduction)

by David Turell , Tuesday, March 01, 2016, 15:19 (2978 days ago) @ David Turell

In a 520 myo arthropod fossil from the Cambrian. Up until now just brains have been found. No precursors:-https://www.sciencedaily.com/releases/2016/02/160229153517.htm-"The animal, called Chengjiangocaris kunmingensis, lived during the Cambrian ‘explosion', a period of rapid evolutionary development about half a billion years ago when most major animal groups first appear in the fossil record. C. kunmingensis belongs to a group of animals called fuxianhuiids, and was an early ancestor of modern arthropods - the diverse group that includes insects, spiders and crustaceans.-***-"Like modern arthropods, C. kunmingensis had a nerve cord - which is analogous to a spinal cord in vertebrates - running throughout its body, with each one of the bead-like ganglia controlling a single pair of walking legs.-"Closer examination of the exceptionally preserved ganglia revealed dozens of spindly fibres, each measuring about five thousandths of a millimetre in length. “These delicate fibres displayed a highly regular distribution pattern, and so we wanted to figure out if they were made of the same material as the ganglia that form the nerve cord,” said Ortega-Hernández. “Using fluorescence microscopy, we confirmed that the fibres were in fact individual nerves, fossilised as carbon films, offering an unprecedented level of detail. These fossils greatly improve our understanding of how the nervous system evolved.”-"For Ortega-Hernández and his colleagues, a key question is what this discovery tells us about the evolution of early animals, since the nervous system contains so much information. Further analysis revealed that some aspects of the nervous system in C. kunmingensis appear to be structured similar to that of modern priapulids (penis worms) and onychophorans (velvet worms), with regularly-spaced nerves coming out from the ventral nerve cord.-"In contrast, these dozens of nerves have been lost independently in the tardigrades (water bears) and modern arthropods, suggesting that simplification played an important role in the evolution of the nervous system."-Comment: Following Denton, he would assume his 'Types' appeared in the Cambrian and then were later modified, but traceable to the original. Note our spinal cord is dorsal in comparison.