Ctenophore Evolution In Light Of Morphospace And Disparity Analyses

Ctenophores,also called comb jellies,are transparent,gelatinous marine animals of diploblastic organization.They have varied body form,like spherical,pouch and leaf shaped.They are biradial and have a mesoglea that contains muscle fibers and amebocytes.Their tentacles have special colloblasts.The most prominent features are the apical sense organ and eight columns of longitudinal,radial ctene rows on the body surface.Eoandromeda octobrachiata,which is found in Chinese south Ediacaran stratum,has a high conical body with eight possible arms,is regarded as the oldest ctenophores fossil.A kind of ctenophore embryo is found in the Kuanchuanpu biota of the Cambrian,which was spherical and had eight comb rows and miss tentacles.Scleroctenophora is a group of sclerotized and armored ctenophores from the early Cambrian period,which have diagnostic ctenophore features,for example,octaradially arranged ctene rows and apical organ.It represents extinct but important stem group of ctenophores and reveals a special evolutionary history of the Ctenophora.Ctenophore fossils are also found in the Qingjiang biota(Cambrian Series 2,early Stage 4)the later Cambrian Guanshan biota(Cambrian Series 2,early Stage 4),the Burgess Shale biota(Cambrian Series 3,Stage 5),the McKay Group(Furongian,Jiangshanian)of Canada.The incomplete ctenophora fossils that were found in the McKay Group,are thought to be close to living Ctenophora.To explore the morphological evolution of Ctenophora,we conducted analyses of the ecomorphospace and disparity analyses of total-group Ctenophores,including published fossil taxa and representative species of major living groups.The result show that disparity of Cambrian Ctenophora is higher than the disparity of living Ctenophora.