Avian-like attributes of a virtual brain model of the oviraptorid theropod Conchoraptor gracilis
Avian-like attributes of a virtual brain model of the oviraptorid theropod Conchoraptor gracilis
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DOI：
10.1007/s00114-007-0219-1
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发表时间：
2007-06-01
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通讯作者：
Kundrat, Martin
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作者：
Kundrat, Martin
本文分析了在蒙古上白垩统Hermiin Tsav地区发现的一个几乎完整的细长锥盗龙（Conchoraptor gracilis Barsbold，1986）的成年内颅化石。内神经颅腔的虚拟模型来自CT扫描，代表了迄今为止最完整的手盗龙内模。它显示嗅球缩小，大脑半球大，与扩大的小脑接触，骨骺突起，视叶向腹侧移位，推测小脑叶，小脑耳廓扩大，延髓深，腹曲突出。与始祖鸟相反，Conchoraptor的缩短的嗅觉道和小脑超过大脑半球类似于现代鸟类的情况。计算脑质量相对于身体质量的比例表明，Conchoraptor福尔斯属于现存鸟类的范围，而始祖鸟则处于边缘位置。然而，与始祖鸟和现代鸟类的相应结构相比，Conchoraptor的大多数内神经颅属性都不太像鸟类，其中1）后外侧扩展的半球域广泛覆盖视叶，2）骨骺突出到大脑后部，3）视叶的侧向延伸大大降低了大脑的长宽比，（4）侧位视叶与后脑前部重叠;（5）小脑与中脑明显重叠。Conchoraptor的内神经颅特征，综合起来，表明动物有敏锐的视觉，平衡和协调感。在这项研究中提出的数据不允许一个明确的评估是否鸟类一样的endoneurocranial特征的不会飞Conchoraptor进化收敛到那些鸟类兽脚亚目，或表明一个派生的oviraptorosaurs从会飞的祖先。
An almost complete adult endoneurocranium of Conchoraptor gracilis Barsbold 1986 (Oviraptoridae; ZPAL MgD-I/95), discovered at the Hermiin Tsav locality (the Upper Cretaceous) in Mongolia, is analyzed. A virtual model of the endoneurocranial cavity was derived from CT scans and represents the most complete maniraptoran endocast to date. It displays reduced olfactory bulbs, large cerebral hemispheres in contact with the expanded cerebellum, an epiphysial projection, optic lobes displaced latero-ventrally, presumptive cerebellar folia, enlarged cerebellar auricles, and a deep medulla oblongata with a prominent ventral flexure. Contrary to Archaeopteryx, the shortened olfactory tract and cerebellum overtopping cerebral hemispheres of Conchoraptor resemble conditions in modern birds. Calculating brain mass relative to body mass indicates that Conchoraptor falls within the range of extant birds, whereas Archaeopteryx occupies a marginal position. Most of the endoneurocranial attributes, however, have a less birdlike appearance in Conchoraptor than do corresponding structures in Archaeopteryx and modern birds in which 1) postero-laterally expanded hemispheral domains broadly overlap the optic lobes, 2) the epiphysis projects to the posterior cerebrum, 3) lateral extension of the optic lobes substantially decreases a brain length-to-width ratio, 4) optic lobe and anterior hindbrain are superposed in lateral view, and 5) cerebellar and midbrain compartments are in distinct superposition. The endoneurocranial characteristics of Conchoraptor, taken together, suggest that the animal had a keen sense of vision, balance, and coordination. The data presented in this study do not allow an unambiguous assessment whether the avian-like endoneurocranial characteristics of the flightless Conchoraptor evolved convergently to those of avian theropods, or indicate a derivation of oviraptorosaurs from volant ancestors.