蚓蜥科動(dòng)物是一類大多數(shù)沒(méi)有腿的爬行動(dòng)物（右圖所示），長(zhǎng)期以來(lái),，它們一直讓動(dòng)物學(xué)家感到困惑不解,。
這些也被稱為蚓蜥的動(dòng)物到底是隨著時(shí)間的流逝而失去了它們的腿，還是一種與蛇親緣關(guān)系更近的爬行動(dòng)物呢？
幸虧在德國(guó)梅塞爾精致的化石沉積層中發(fā)現(xiàn)的一具大約4500萬(wàn)年前的蚓蜥化石,，讓這一未解之謎終于有了答案——無(wú)論如何,，蚓蜥科動(dòng)物確實(shí)是蜥蜴。
德國(guó)柏林市洪堡大學(xué)的古生物學(xué)家Johannes Müller和同事在5月18日的《自然》雜志網(wǎng)絡(luò)版上報(bào)告說(shuō),，這具近乎完整的Cryptolacerta hassiaca小蜥蜴的骨架化石（左圖所示）具有與現(xiàn)代蚓蜥一樣粗大的頭骨特征,，而這種爬行動(dòng)物依然保存著前肢與后肢。
盡管這種爬行動(dòng)物因?yàn)橥砹?000萬(wàn)年而不可能是另一種蚓蜥的直系祖先,，但是研究人員認(rèn)為,，它保留了蚓蜥祖先的特征，并因此對(duì)于追蹤這類動(dòng)物的起源是非常有用的,。
這一發(fā)現(xiàn)不但表明這些獨(dú)特的蜥蜴通過(guò)失去它們的四肢而獨(dú)立地與蛇平行演化,，同時(shí)一顆強(qiáng)健的頭骨還能夠適應(yīng)挖洞，并且在這些蜥蜴失去四肢之前適于在落葉層中搜尋食物,。
這種蜥蜴一旦開(kāi)始挖洞,，其前肢和后肢的尺寸便會(huì)逐漸縮小，并最終采取與像蛇一樣的外觀,。
蚓蜥主要分布于非洲和南美洲,。它是一種穴居的神秘的爬行動(dòng)物，外表和習(xí)性均與蚓螈類似,。蚓蜥是食肉動(dòng)物,，其有力的牙齒可把獵物撕成大塊。一些蚓蜥物種可以像蜥蜴一樣在遇到危險(xiǎn)時(shí)斷開(kāi)尾巴以逃跑,。大部分蚓蜥會(huì)產(chǎn)卵,，不過(guò)也有一些蚓蜥是胎生。（生物谷Bioon.com）
生物谷推薦原文出處：
Nature DOI:10.1038/nature09919
Eocene lizard from Germany reveals amphisbaenian origins
Johannes Müller; Christy A. Hipsley; Jason J. Head; Nikolay Kardjilov; André Hilger; Michael Wuttke; Robert R. Reisz
Amphisbaenia is a speciose clade of fossorial lizards characterized by a snake-like body and a strongly reinforced skull adapted for head-first burrowing1, 2. The evolutionary origins of amphisbaenians are controversial, with molecular data uniting them with lacertids3, 4, a clade of Old World terrestrial lizards, whereas morphology supports a grouping with snakes and other limbless squamates5, 6, 7, 8, 9. Reports of fossil stem amphisbaenians10 have been falsified11, and no fossils have previously tested these competing phylogenetic hypotheses or shed light on ancestral amphisbaenian ecology. Here we report the discovery of a new lacertid-like lizard from the Eocene Messel locality of Germany that provides the first morphological evidence for lacertid–amphisbaenian monophyly on the basis of a reinforced, akinetic skull roof and braincase, supporting the view that body elongation and limblessness in amphisbaenians and snakes evolved independently. Morphometric analysis of body shape and ecology in squamates indicates that the postcranial anatomy of the new taxon is most consistent with opportunistically burrowing habits, which in combination with cranial reinforcement indicates that head-first burrowing evolved before body elongation and may have been a crucial first step in the evolution of amphisbaenian fossoriality.
