13950.遼西早白堊世離龍類的地理地史分布及其演化過程

1、版權(quán)聲明任何收存和保管本論文各種版本的單位和個人，未經(jīng)本論文作者同意，不得將本論文轉(zhuǎn)借他人，亦不得隨意復制、抄錄、拍照或以任何方式傳播。否則，弓起有礙作者著作權(quán)之問題，將可能承擔法律責任。EarlyCretaceousEVolutionofChoriotoderesinWesternLiaoningbasedonGeographicandStratigraphicEVidencezHANGWei(PaleontologyandStrat

2、igraphy)Supervisor：GAOKeqinAbstractTheChoristodera，adistinctcladeofaquaticsemiaquaticdiapsidarept訂eswhichhadliVedintheLaurasiaattheMeozoicandCenozoictime，hadarapideVolutionduringtheEarlyCretaceoustimeinwestemLiaoningProV

3、ince，aseVidencedbytheirextensiVefossilrecordfromtheYixianandJiufotangfoHllationsChoristoderanfossilshaVebeenfoundfromlocalitieswithintheLingyuan，Yixian，ChaoyangandJianchangareas，withasigniflcantconcemrationof廈助厶口腸s口甜，“Jl

4、ocalitiesattheYixianareaIntemsofgeoIogicalrange，foss訂sof砌向a腸J口蹦，“5and胸巧“陽s甜如螂aresimplyrestrictedtotheYixianFo訂nation，whilethoseof脅幽儺口渺螂and腳j饑辦優(yōu)口渺螂areconnnedtotheJiufotangFomationTheextendeddistrbutionoftheCretaceouschori

5、stoderesinwestemLiaoningindicatedadispersalpattemofthegroupfromwesttoeastandfromsouthtonorthThelastappearanceof碭p|f2口，Ds口甜，甜schoristoderesinwestemLiaoningisrecordedwiththousandsoffossilspecimenspreservedintuffaceousdepos

6、itsoftheDakangpubedsoftheYixianFomationSuchanunusualconcentrationoffossilsindicatesapossiblemassextinctioneventofthiscIadeduringtheEarIyCretaceousAptiantimeAIlchoristodereswerewipedoutfromthewestemLiaoningregionduringthe