近日,，里約熱內(nèi)盧國家博物館的古生物學(xué)家們在巴西東北部發(fā)現(xiàn)一種14米長，有三排牙齒的兇猛食肉恐龍,，這種牙齒結(jié)構(gòu)是獸腳亞目恐龍里獨一無二的,。它被命名為歌倫波奧沙拉龍（Oxalaiaquilombensis），生活在9500萬年前,。相關(guān)文章發(fā)表在《巴西科學(xué)院年鑒》（Annals of the Brazilian Academy of Sciences）,。
奧沙拉龍一般只使用最前排的牙齒，后面兩排正在發(fā)育的牙齒可替換前面磨損或掉落的牙齒,，這種現(xiàn)象在鯊魚和某些爬行動物中很常見,，但在獸腳類恐龍中還是頭一次。
奧沙拉龍屬于一種棘背龍（spinosaurids）,，它的吻端狹長,，很像鱷魚。有趣的是,，它似乎與北非出土的那些棘背龍親緣關(guān)系更近,，跟巴西的其它棘背龍反而疏遠(yuǎn)些。因此我們可以推斷,，這些棘背龍的祖先早在1.3-1.1億年前,，非洲和南美大陸分開時，就已經(jīng)出現(xiàn)了,，隨著大陸漂移,，棘背龍的祖先分隔兩岸,，走上了獨立的演化道路。（生物谷Bioon.com）
生物谷推薦原文出處：
An. Acad. Bras. Ciênc. [online]. 2011, vol.83, n.1, pp. 99-108. ISSN 0001-3765.
A new dinosaur (Theropoda, Spinosauridae) from the Cretaceous (Cenomanian) Alcantara Formation, Cajual Island, Brazil.
KELLNER, Alexander WA. et al.
A new spinosaurid taxon, Oxalaia quilombensis gen. et sp. nov., is described based on the anterior part of a snout and a fragment of a maxilla. These specimens were collected at the Laje do Coringa site, Late Cretaceous (Cenomanian) of the S?o Luis Basin. Unlike Cristatusaurus and Suchomimus, Oxalaia quilombensis lacks serrations on the teeth. The new species differs from Angaturama limai by having the anterior part of the premaxillae more expanded and by lacking a sagittal premaxillary crest. It further differs from Spinosaurus cf. S. aegyptiacus and the Algerian spinosaurid by the rounder shape of the terminal expansion. Furthermore, xalaia quilobensis has one functional tooth followed by two replacement teeth, a feature not previously observed in theropods. Oxalaia quilombensis appears to be more closely related to the spinosaurids found in North Africa than to the Brazilian members of this clade and thus further increases the diversity of these enigmatic predatory dinosaurs in this country.
Keywords : Dinosauria; Spinosauridae; Oxalaia quilombensis; Cenomanian; Brazil.
