“始祖鳥(niǎo)”（Archaeopteryx）是最早的鳥(niǎo),，是處在兩大類(lèi)別動(dòng)物的過(guò)渡階段的一個(gè)非常好的演化實(shí)例。所研究的“始祖鳥(niǎo)”化石標(biāo)本實(shí)際上是一種小型食肉獸腳恐龍的骨架,，上面有現(xiàn)代飛行羽毛衍生物,。對(duì)倫敦的“始祖鳥(niǎo)”標(biāo)本所做的一項(xiàng)新的研究工作，采用非破壞性計(jì)算機(jī)斷層掃描技術(shù),、X-射線掃描技術(shù)和計(jì)算機(jī)三維重建技術(shù)來(lái)觀測(cè)“始祖鳥(niǎo)”的腦腔內(nèi)部,、模擬其大腦形狀和重建其內(nèi)耳。研究發(fā)現(xiàn),， “始祖鳥(niǎo)”原來(lái)不像恐龍,，它有一個(gè)真正的“鳥(niǎo)腦”，完全具備飛行所需的視力,、平衡和協(xié)調(diào)條件,。
The avian nature of the brain and inner ear of Archaeopteryx
Archaeopteryx, the earliest known flying bird (avialan) from the Late Jurassic period, exhibits many shared primitive characters with more basal coelurosaurian dinosaurs (the clade including all theropods more bird-like than Allosaurus), such as teeth, a long bony tail and pinnate feathers. However, Archaeopteryx possessed asymmetrical flight feathers on its wings and tail, together with a wing feather arrangement shared with modern birds. This suggests some degree of powered flight capability but, until now, little was understood about the extent to which its brain and special senses were adapted for flight. We investigated this problem by computed tomography scanning and three-dimensional reconstruction of the braincase of the London specimen of Archaeopteryx. Here we show the reconstruction of the braincase from which we derived endocasts of the brain and inner ear. These suggest that Archaeopteryx closely resembled modern birds in the dominance of the sense of vision and in the possession of expanded auditory and spatial sensory perception in the ear. We conclude that Archaeopteryx had acquired the derived neurological and structural adaptations necessary for flight. An enlarged forebrain suggests that it had also developed enhanced somatosensory integration with these special senses demanded by a lifestyle involving flying ability.
Figure 1 Braincase of the holotype of Archaeopteryx lithographica (BMNH 37001). Scale bar, 10 mm. a, Original prepared specimen in left lateral view6. b, c, 3D reconstructions of braincase based on X-ray CT data; left lateral view (b) and posterior view (c) showing right side collapse. d, e, Stereopair of restored braincase in oblique right-anterior view (d) and posterior view (e). Elements from the left side are reversed except for the right quadrate. L and R indicate left and right. Abbreviations: *BO?, ?basioccipital fragment; ca, crista arcuata; cq, mandibular condyle of quadrate; F, frontal; fm, foramen magnum; LS, laterosphenoid; met, metotic; O, opisthotic; oc, occiput; opq, orbital process of quadrate; otq, otic wing of quadrate; P, parietal; pcq, pterygoid condyle of quadrate; pop, paroccipital process of opisthotic; PR, prootic; Q, right quadrate; *SO, supraoccipital fragment; V, trigeminal nerve foramen; VII, facial nerve foramen. Original imagery available at < http://www.DigiMorph.org >.
Figure 2 Right quadrate of BMNH 37001 in medial view. Scale bar, 1 mm. Abbreviations: ptf, pterygoid facet; pnf, pneumatic foramen; mc, mandibular condyle; opp, optic process; otc, otic capitulum. See also Supplementary Information for clear views of the pneumatic foramen.
Figure 3 Restored endocast of the brain of BMNH 37001 rendered as a shell. Elements from the left side are reversed. Scale bar, 10 mm. a, Right lateral view. b, Dorsal view. c, Posterior view. Abbreviations: c, cerebrum (telencephalon); cb, cerebellum; fl, floccular lobe of the cerebellum; fm, foramen magnum; mo, medulla oblongata (rhombencephalon); o, olfactory lobe; ol, optic lobes (metencephalic tectum); ot, olfactory tract; pc, cerebellar prominence; pg, pineal gland (epiphysis); ss, semicircular sulcus. Cranial nerves: II, optic; III?, possible oculomotor; V, trigeminal; VII, facial; VIII?, auditory (or endolymphatic duct, see Fig. 5); IX?, glossopharyngeal; X, vagus; XII, hypoglossal. Original imagery available at < http://www.DigiMorph.org >.
Figure 5 Right inner ear of BMNH 37001. 3D model based on X-ray CT. Scale bar, 2 mm. a, Lateral (external) view. b, Anterior view. c, Posterior view. Abbreviations: aa, anterior ampulla; ac, anterior canal; cc, common crus; cd, cochlear duct; fr, fenestra pseudorotunda; fv, fenestra vestibuli (fenestra ovalis); la, lateral ampulla; lc, tentative course of lateral canal; LO, left opisthotic; pc, tentative course of posterior canal; pc (u), posterior canal (upper part); PR, prootic; sa, sacculus; ut, utriculus; VIII?, acoustic nerve or endolymphatic duct. Original imagery available at < http://www.DigiMorph.org
