Bilaterians of the Precambrian-Cambrian Transition and the Annelid-Arthropod Relationship Export

@article{citeulike:2719893, abstract = {The Late Proterozoic fossil record contains the remains of animals that may represent a grade of organization not found among living metazoans. These forms were segmented and large enough to require a hemocoel, yet evidently were not capable of forming penetrating burrows, which are essentially absent from contemporaneous sediments containing locally common but chiefly horizontal trace fossils. As has been noted, there is no evidence that Late Proterozoic invertebrates possessed a coelom suited for peristaltic burrowing. Therefore, the annelidan body plan had probably not appeared. It is not implausible, however, that coelomic spaces in the form of ducts or organ sacs were present in Late Proterozoic segmented forms. Uniramians, some of which employ the hemocoel hydrostatically in lobopodal locomotion, may be allied to segmented hemocoelic forms not unlike sprigginids. Coelomic spaces may have been exploited in some protoarthropod lineages to enhance pedal-wave locomotion, but probably there are no eucoelomic forms in arthropodan ancestry. Annelids may represent an early divergent branch of seriated worms, perhaps rather nemertine-like at first, that developed eucoelomic compartments only in Cambrian time. The extinct grade is most likely to have arisen from flatworm-like ancestors. Of all the proposed phylogenies examined, only that of Manton closely anticipates these interpretations of the early metazoan fossil record. 10.1073/pnas.86.7.2272}, author = {Valentine, James W.}, citeulike-article-id = {2719893}, citeulike-linkout-0 = {http://dx.doi.org/10.1073/pnas.86.7.2272}, citeulike-linkout-1 = {http://www.pnas.org/cgi/content/abstract/86/7/2272}, citeulike-linkout-2 = {http://view.ncbi.nlm.nih.gov/pubmed/16594022}, citeulike-linkout-3 = {http://www.hubmed.org/display.cgi?uids=16594022}, day = {1}, doi = {10.1073/pnas.86.7.2272}, journal = {Proceedings of the National Academy of Sciences}, keywords = {animal-evolution, bilaterians, precambrian-cambrian-transition}, month = {April}, number = {7}, pages = {2272--2275}, posted-at = {2008-04-26 01:56:27}, priority = {2}, title = {Bilaterians of the Precambrian-Cambrian Transition and the Annelid-Arthropod Relationship}, url = {http://dx.doi.org/10.1073/pnas.86.7.2272}, volume = {86}, year = {1989} }

TY - JOUR ID - citeulike:2719893 L3 - citeulike-article-id:2719893 N2 - The Late Proterozoic fossil record contains the remains of animals that may represent a grade of organization not found among living metazoans. These forms were segmented and large enough to require a hemocoel, yet evidently were not capable of forming penetrating burrows, which are essentially absent from contemporaneous sediments containing locally common but chiefly horizontal trace fossils. As has been noted, there is no evidence that Late Proterozoic invertebrates possessed a coelom suited for peristaltic burrowing. Therefore, the annelidan body plan had probably not appeared. It is not implausible, however, that coelomic spaces in the form of ducts or organ sacs were present in Late Proterozoic segmented forms. Uniramians, some of which employ the hemocoel hydrostatically in lobopodal locomotion, may be allied to segmented hemocoelic forms not unlike sprigginids. Coelomic spaces may have been exploited in some protoarthropod lineages to enhance pedal-wave locomotion, but probably there are no eucoelomic forms in arthropodan ancestry. Annelids may represent an early divergent branch of seriated worms, perhaps rather nemertine-like at first, that developed eucoelomic compartments only in Cambrian time. The extinct grade is most likely to have arisen from flatworm-like ancestors. Of all the proposed phylogenies examined, only that of Manton closely anticipates these interpretations of the early metazoan fossil record. 10.1073/pnas.86.7.2272 IS - 7 JF - Proceedings of the National Academy of Sciences EP - 2275 TI - Bilaterians of the Precambrian-Cambrian Transition and the Annelid-Arthropod Relationship VL - 86 SP - 2272 KW - animal-evolution KW - bilaterians KW - precambrian-cambrian-transition AU - Valentine, James PY - 1989/04/01/ UR - http://dx.doi.org/10.1073/pnas.86.7.2272 ER -