Systematic Ichnology And Paleoecology Study Of Trace Fossil Rhizocorallium

Systematic and detailed paleontology research is focused on Rhizocorallium in several Phaneozoic sections,including Xichuan(Devonian,Nanyang,Henan Province),Ganxi(Devonian,Beichuan,Sichuan Province),Longmendong(Triassic,Emei Mountain,Sichuan Province),Tieqiao(Permian,Laibin,Guangxi Province).Based on the studies of the stratigraphy and sedimentary study of Rhizocorallium host strata,the systematic revised the ichnogenus Rhizocorallium,the systematic large macro-and micro-analysis the morphology characteristics of Rhizocrallium,and the Phanerozoic Rhizocorallium database,four aspects results are proposed:1.The ichnogenus Rhizocorallium is systematically revised basing on the detailed literatures over the world and specimens related to this thesis.Rhizocorallium is subdivided into two ichnospecies,which include Rhizocorallium commune and Rhizocorallium jenense,and two subichnospecies,which include R.commune uliarense and R.commune problematica.Diplocraterion(also spreite trace fossil)and Rhizocorallium are grouped into the ichnofamily Rhizocorallidae.2.According to the key morphology diagnosis,the specimens in the studied sections are named as Rhizocorallium commune.3.Based on the micro-characteristics of burrow,our interpretations suggest that Rhizocorallium is not a biogenic sedimentary structure formed only by the simple motion of the trace maker,but a set of complex and elaborate biogenic structures formed by a succession of several life motions(behaviors)of the trace maker along with symbiotic microorganisms.4.According to the Phanerozoic Rhizocorallium database from 1967–2015,the sedimentary environment and morphological trend of Rhizocorallium in space and time are sketched.Several characteristics are found as below:Rhizocorallium occur widely from shallow sea to deep-sea environment in Phanerozoic.Rhizocorallium commune mainly distributed in shallow marine settings during Paleozic and Mesozoic,and in shallow and deep marine settings in Cenozoic.Rhizocorallium jenense firstly occur in the aftermath of the end-Permian mass extinction and mainly distributed in shallow and deep marine setting in post-Paleozoic.5.In Phanerozoic,the size of Rhizocoralllium burrows shows a gradual increased trend.Meanwhile,the morphological evolution of Rhizocorallium are from simple,parallel to slightly oblique forms to complex,branched and spiral forms.Above all changes indicate that the trace-maker has utilized available conditions(such as substrate type,food supply)for survive in difficult environments.This study will offer systematic materilas and detailed new idea of Rhizocorallium.