正文
of dinosaurs knows, those terrible
reptiles
are divided into two groups: the
Saurischia
and the
Ornithischia
—or, to people for whom that is all Greek, the lizard-hipped and the bird-hipped. The names go back 130 years, to 1887, when they were invented and applied by Harry Seeley, a British
palaeontologist
.
提到恐龙这种恐怖爬行动物的生物学分类，对于恐龙爱好者（哪怕是学龄前儿童）来说，都可谓手到拈来：恐龙分为蜥臀目与鸟臀目（来自希腊语的Saurischia和Ornithischia）两大类，这两个名称来自130年前，由英国古生物学家HSeeley在1887年发明并使用。
-
Aficionado：n. 迷；狂热爱好者
-
Reptile：n. 爬行动物
-
Saurischia：n. 蜥臀目
-
Ornithischia：n. 鸟臀目
-
Palaeontologist：n. 古生物学者
Seeley determined that the arrangement of the bones in a dinosaur’s
pelvis
—specifically, whether the
pubic bone
points forwards (Saurischia) or backwards (Ornithischia)—could be used to assign that species to one of these two groups. In his view, and that of subsequent palaeontologists, the evolution of other features of dinosaur skeletons supported the idea that these two hip-defined groups were what are now referred to as
clades
, each having a single common
ancestor
. Seeley thereby thought he had overthrown the dinosaurs as a true clade themselves: he believed Saurischia and Ornithischia were descended separately from a group called the
thecodonts
.
Seeley发现可以利用恐龙骨盆部位的骨骼结构来将恐龙分为两类：耻骨前凸的为蜥臀目，耻骨向后延伸的为鸟臀目。在他和其后的古生物学家看来，恐龙骨骼其他特征的演化可以证明，这两种根据骨盆定义的分类体现了如今所说的进化枝， 即物种来自单一的共同祖先。因此，Seeley认为他推翻了“恐龙是一个真正进化枝”的理论，他相信蜥臀目与鸟臀目是从槽齿目的并系群分别演来。
-
Pelvis：n. 骨盆
-
Pubic bone：n. 耻骨
-
Clade：n. 分化枝；进化枝
-
Ancestor：n. 始祖，祖先
-
Thecodont：adj. 有槽齿的；槽齿类的
Subsequent analysis suggests he was wrong about that. The dinosaurs do seem to be a proper clade, with a single thecodont ancestor. But the basic division Seeley made of them, into Saurischia and the Ornithischia, has not been challenged—until now.
