Osteohistological analyses reveal diverse strategies of theropod dinosaur body-size evolution
Osteohistological analyses reveal diverse strategies of theropod dinosaur body-size evolution
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DOI：
10.1098/rspb.2020.2258
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发表时间：
2020-11-25
影响因子：
4.7
通讯作者：
Makovicky, Peter J.
中科院分区：
文献类型：
--
作者：
Cullen, Thomas M.;Canale, Juan, I;Makovicky, Peter J.
恐龙的独立进化一直是一个长期的兴趣话题，但目前还不清楚巨大的兽脚类恐龙，化石记录中最大的两足动物，是否都以相同的方式或通过不同的策略获得巨大的尺寸。我们进行多元素的组织学分析，从8个兽脚亚目恐龙的家庭，重点是巨大的龙类和carcharodontosaurids的广泛的数据集采样，重建这些谱系的生长策略和测试，如果特定的骨骼始终保持最完整的生长记录。我们发现，在脊椎成熟的巨型兽脚亚目恐龙中，负重骨骼始终保持着广泛的生长记录，而非负重骨骼被重塑，对生长重建的作用较小，这与在较小的兽脚亚目恐龙和其他一些恐龙分支中观察到的模式相反。我们发现一个异时的增长模式拟合的加速度模型，在龙类carcharodontosaurids更好地拟合模型的hypermorphosis。这些不同的生长模式似乎受到遗传学的限制，分别代表了较小的腔上龙类和异特龙类的极端生长模式。这提供了第一个证据，证明化石记录中最大的两足动物的大小进化缺乏强大的机械或生理限制，并证明了有史以来最长寿的恐龙个体之一。
The independent evolution of gigantism among dinosaurs has been a topic of long-standing interest, but it remains unclear if gigantic theropods, the largest bipeds in the fossil record, all achieved massive sizes in the same manner, or through different strategies. We perform multi-element histological analyses on a phylogenetically broad dataset sampled from eight theropod families, with a focus on gigantic tyrannosaurids and carcharodontosaurids, to reconstruct the growth strategies of these lineages and test if particular bones consistently preserve the most complete growth record. We find that in skeletally mature gigantic theropods, weight-bearing bones consistently preserve extensive growth records, whereas non-weight-bearing bones are remodelled and less useful for growth reconstruction, contrary to the pattern observed in smaller theropods and some other dinosaur clades. We find a heterochronic pattern of growth fitting an acceleration model in tyrannosaurids, with allosauroid carcharodontosaurids better fitting a model of hypermorphosis. These divergent growth patterns appear phylogenetically constrained, representing extreme versions of the growth patterns present in smaller coelurosaurs and allosauroids, respectively. This provides the first evidence of a lack of strong mechanistic or physiological constraints on size evolution in the largest bipeds in the fossil record and evidence of one of the longest-living individual dinosaurs ever documented.