Limb-bone scaling indicates diverse stance and gait in quadrupedal ornithischian dinosaurs.
Limb-bone scaling indicates diverse stance and gait in quadrupedal ornithischian dinosaurs.
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DOI：
10.1371/journal.pone.0036904
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Barrett PM
中科院分区：
文献类型：
--
作者：
Maidment SC;Linton DH;Upchurch P;Barrett PM
最原始的鸟臀目恐龙是小型两足恐龙，但四足恐龙在进化支系中独立进化了三次。从两足动物祖先到四足动物的过渡在陆生脊椎动物的进化史上是罕见的，现存的类似物并不存在。四足鸟臀目动物的祖先双足鸟臀目动物对它们施加的限制仍未被探索，因此，关于它们的站立和步态的争论仍在继续。例如，有人提出一些鸟臀目动物可以奔跑，而另一些人则认为没有一种鸟臀目动物会跑动。根据现有分类群的肢体骨骼缩放和运动理论的生物力学概念，我们使用迄今为止汇编的最大的鸟臀龙颅后测量数据集来检查四足鸟臀龙的站立和步态。鸭嘴龙和角鼻龙股骨中轴偏心率的差异可能表明鸭嘴龙在运动时将脚放在中线上，而角鼻龙则将脚放在更外侧的臀部下方。相对于较小的类群，最大角鼻龙的肱骨更健壮可能是由于角鼻龙的头骨尺寸与体重的正异速，而最大的剑龙的肱骨纤细可能是由于进化分支中皮肤盔甲分布的差异。鸭嘴龙在四足鸟目动物中表现出最灵活的运动形态，这表明鸭嘴龙的运动能力比角鼻目和角鼻目动物更高。四肢骨尺度表明，尽管四肢形态明显趋同，但四足鸟臀目动物的姿态和步态的多样性以前未被认识到。将四足鸟臀目动物归为一个单一的功能类群，隐藏了这种差异。肢体比例和尺度的差异可能是由于拥有显示结构，如角、褶边和真皮盔甲，这些结构可能会影响动物的质量中心，以及运动行为的差异，如迁徙、捕食者逃脱或家庭范围的大小。
The most primitive ornithischian dinosaurs were small bipeds, but quadrupedality evolved three times independently in the clade. The transition to quadrupedality from bipedal ancestors is rare in the history of terrestrial vertebrate evolution, and extant analogues do not exist. Constraints imposed on quadrupedal ornithischians by their ancestral bipedal bauplan remain unexplored, and consequently, debate continues about their stance and gait. For example, it has been proposed that some ornithischians could run, while others consider that none were cursorial. Drawing on biomechanical concepts of limb bone scaling and locomotor theory developed for extant taxa, we use the largest dataset of ornithischian postcranial measurements so far compiled to examine stance and gait in quadrupedal ornithischians. Differences in femoral midshaft eccentricity in hadrosaurs and ceratopsids may indicate that hadrosaurs placed their feet on the midline during locomotion, while ceratopsids placed their feet more laterally, under the hips. More robust humeri in the largest ceratopsids relative to smaller taxa may be due to positive allometry in skull size with body mass in ceratopsids, while slender humeri in the largest stegosaurs may be the result of differences in dermal armor distribution within the clade. Hadrosaurs are found to display the most cursorial morphologies of the quadrupedal ornithischian cades, indicating higher locomotor performance than in ceratopsids and thyreophorans. Limb bone scaling indicates that a previously unrealised diversity of stances and gaits were employed by quadrupedal ornithischians despite apparent convergence in limb morphology. Grouping quadrupedal ornithischians together as a single functional group hides this disparity. Differences in limb proportions and scaling are likely due to the possession of display structures such as horns, frills and dermal armor that may have affected the center of mass of the animal, and differences in locomotor behaviour such as migration, predator escape or home range size.
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影响因子：
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作者：
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