古蟲動物門

古蟲動物門（Vetulicolia）

據國家自然科學基金委員會２００２年２月１日報道，西北大學早期生命研究所所長舒德干教授等與英國科學家合作，在早期動物演化研究領域取得突破性成果――發現中國澄江化石庫中新的后口動物門，並將這一滅絕類群命名為“古蟲動物門”。

古蟲動物是一類絕滅的動物類群，僅發現於中國雲南澄江的早寒武紀地層。其外形分節，曾被認為是一類獨特的節肢動物。2001年，舒德乾等在鰓孔的位置發現鰓裂，並把鰓孔重新解釋為鰓囊。這樣就把古蟲從節肢動物中分裂出來，建立古蟲動物門，代表具有一個特殊身體構型的后口動物類群。巨型古蟲動物俞元蟲，還發育有細長而精細的鰓絲，代表古蟲動物發展的最高峰。古蟲動物門的一些特徵，尤其是鰓裂，對於研究后口動物分異的早期階段提供了新的線索和希望。低等古蟲類動物在澄江動物群中的后口動物序列中出現時間最早，這表明脊椎動物的分節特徵很可能不是後來獨立獲得的，而是從后口動物和原口動物共同的分節型祖先那裡繼承而來的。古蟲動物印證了分子生物學和分子發育生物學研究結果推測：最原始的后口動物是一類開始發育出具鰓裂構造的原始分節動物(Holland et al.,1997;Winchell et al.,2001;Gee,2001a,b)。有的進一步認為古蟲與海鞘相近（Richard et al.,2007）。絕滅類群古蟲動物包括8屬9種：楔形古蟲Vetulicola cuneatus Hou,1987；長方形古蟲Vetulicola rectangulata Luoet Hu,1999，困惑斑府蟲Banffia confusaChen et Zhou,1997，王冠西大蟲Xidazoon stephanus Shu,Conway Morris et Zhang,1999，宏大俞元蟲Yuyuanozoon magnificissimi Chen,Feng et Zhu，2003，郝氏地大蟲Didazoon haoae Shu et Han,2001，具腹圓口蟲Pomatrum ventralis Luo et Hu,1999，長尾異形蟲Heteromorphus longicaudatus Luo et Hu,1999，美麗北大動物Beidazoon venustum shu,2005＝丘疹丘疹古蟲Bullivetula variola Richard et al.,2007,串珠古蟲Vetulicola monile Richard et al.,2007。現代生物學和分子生物學最新研究表明，現存的后口動物中只有半索動物門、棘皮動物門和脊索動物門3個門類，古蟲動物化石的研究表明后口動物還包括現今已不復存在的第四個門———“古蟲動物門”。

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