論文標題:A Cambrian unarmoured lobopodian, †Lenisambulatrix humboldti gen. et sp. nov., compared with new material of †Diania cactiformis
期刊:Scientific Reports
作者:Qiang Ou & Georg Mayer
發表時間:2018/09/20
數字識別碼:10.1038/s41598-018-31499-y
原文連結:https://www.nature.com/articles/s41598-018-31499-y?utm_source=Other_website&utm_medium=Website_links&utm_content=RenLi-MixedBrand-multijournal-Multidisciplinary-China&utm_campaign=ORG_USG_JRCN_RL_article_promotion_sciencenet_Sep_4th
微信連結:https://mp.weixin.qq.com/s/JIU6UhxEkJjlrr2l9_74hg
《科學報告》近日發表的一項研究A Cambrian unarmoured lobopodian, †Lenisambulatrix humboldti gen. et sp. nov., compared with new material of †Diania cactiformis描述了寒武紀(5.41-4.85億年前)葉足動物的一個新物種——一種具有柔軟附肢的蠕蟲狀動物。
中國地質大學(北京)的歐強和德國卡塞爾大學的Georg Mayer將這個命名為Lenisambulatrix humboldti的新物種與之前描述過的葉足動物仙掌滇蟲(Diania cactiformis)進行比較,發現了一些新細節。
圖1:Lenisambulatrix humboldti的三維重建模型。圖源:Ou & Mayer
作者指出,兩種葉足動物的身形和軀體分節都很相似,都有較厚較長的附肢(葉足),長度約為11.6-18mm。與其它葉足動物不同的是,兩個物種似乎都無爪。不過,仙掌滇蟲的軀幹表面布滿刺狀鎧甲,故其綽號為「行走的仙人掌」,但L. humboldti的整個軀體似乎並無盔甲。
圖2:Lenisambulatrix humboldti 的正模標本。圖源:Ou & Mayer
根據作者描述,新物種的軀體有分節、呈管狀,與蠕蟲類似,且每個體節都有一對附肢。新物種軀體只有一端得以保存,且並未發現如眼睛、嘴巴或觸鬚這些可以確定此端為頭部的顯著特徵。相比之下,假定為仙掌滇蟲頭部的部位則具有明顯的類似頭盔的結構。
圖3:葉足動物仙掌滇蟲的細節圖。圖源:Ou & Mayer
從兩個物種的形態特徵可以大致判斷出它們曾經可能的生活方式。因為兩者都是海洋棲息動物,它們的無爪附肢可能是為了適應在柔軟的海底行走或爬行。仙掌滇蟲的厚重鎧甲可能有助於防禦捕食者的攻擊,而L. humboldti的軀體較柔軟,或表明其個體曾過著隱居生活,藏於縫隙或海綿群體中以抵禦被捕食的風險。
摘要:Cambrian marine lobopodians are generally considered as predecessors of modern panarthropods (onychophorans, tardigrades, and arthropods). Hence, further study of their morphological diversity and early radiation may enhance our understanding of the ground pattern and evolutionary history of panarthropods. Here, we report a rare lobopodian species, †Lenisambulatrix humboldti gen. et sp. nov. (「Humboldt lobopodian」), from the early Cambrian Chengjiang Lagerstätte and describe new morphological features of †Diania cactiformis, a coeval armoured lobopodian nicknamed 「walking cactus」. Both lobopodian species were similar in possessing rather thick, elongate lobopods without terminal claws. However, in contrast to †Diania cactiformis, the body of which was heavily armored with spines, the trunk and limbs of the Humboldt lobopodian were entirely unarmored. Our study augments the morphological diversity of Cambrian lobopodians and presents two evolutionary extremes of cuticular ornamentation: one represented by the Humboldt lobopodian, which was most likely entirely 「naked」, the other epitomized by †D. cactiformis, which was highly 「armoured」.
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