Early development of the facial region in a non-avian theropod dinosaur
Early development of the facial region in a non-avian theropod dinosaur
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DOI：
10.1098/rspb.2005.3071
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发表时间：
2005-06-07
影响因子：
4.7
通讯作者：
Fechner, R
中科院分区：
文献类型：
--
作者：
Rauhut, OWM;Fechner, R
葡萄牙晚侏罗世（1.53亿年前的基梅里基纪）的兽脚亚目恐龙异特龙的分离的上颌骨是迄今为止报道的第一个非骨龙类兽脚亚目恐龙孵化的头骨遗骸，它为非鸟类兽脚亚目恐龙的早期颅骨发育提供了新的线索。异特龙的幼崽似乎只有成年鳄鱼身长的七分之一或更短，因此在体型上与现存大型鳄鱼的幼崽相当，但与相对较大的虚龙幼崽不同。在早期发育过程中，鼻子经历了相当多的正异速生长和牙齿数量的增加。该元素特别值得注意的是与副鼻翼气动系统相关的丰富和发达的特征。气动结构包括所有在成年异特龙中发现的结构，其中大多数甚至比成年颅骨更发达。结合异特龙鼓室气动系统个体发育的证据，这些发现表明，在兽脚亚目个体发育中，颅骨气动发育较早。在非鸟类兽脚亚目恐龙个体发生的早期阶段，气动特征的强烈发展支持了颅骨气动是机会性的假设，并表明异时性在该群体颅面气动的进化中发挥了重要作用。
An isolated maxilla of the theropod dinosaur Allosaurus from the Late Jurassic (the Kimmeridgian, 153 million years ago) of Portugal is the first cranial remain of a non-coelurosaurian theropod hatchling reported so far, and sheds new light on the early cranial development of non-avian theropods. Allosaurus hatchlings seem to have been one-seventh or less of the adult length and are thus comparable in relative size to hatchlings of large extant crocodile species, but are unlike the relatively larger hatchlings in coelurosaurs. The snout experienced considerable positive allometry and an increase in tooth count during early development. The element is especially noteworthy for the abundant and well-developed features associated with the paranasal pneumatic system. Pneumatic structures present include all those found in adult allosaurids and most are even more developed than in adult skulls. Together with evidence on the ontogeny of the tympanic pneumatic system in allosaurids, these findings demonstrate that cranial pneumaticity developed early in theropod ontogeny. The strong development of pneumatic features in early ontogenetic stages of non-avian theropods supports the hypothesis that pneumatization of cranial bones was opportunistic and indicates that heterochrony played an important role in the evolution of craniofacial pneumaticity in this group.