Chapelle Kimberley E J, Botha Jennifer, Choiniere Jonah N
Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, 2050 South Africa.
School of Geosciences, University of the Witwatersrand, Johannesburg, 2050 South Africa.
Biol Lett. 2021 May;17(5):20200843. doi: 10.1098/rsbl.2020.0843. Epub 2021 May 12.
There is growing evidence of developmental plasticity in early branching dinosaurs and their outgroups. This is reflected in disparate patterns of morphological and histological change during ontogeny. In fossils, only the osteohistological assessment of annual lines of arrested growth (LAGs) can reveal the pace of skeletal growth. Some later branching non-bird dinosaur species appear to have followed an asymptotic growth pattern, with declining growth rates at increasing ontogenetic ages. By contrast, the early branching sauropodomorph appears to have had plastic growth, suggesting that this was the plesiomorphic condition for dinosaurs. The South African sauropodomorph is an ideal taxon in which to test this because it is known from a comprehensive ontogenetic series, it has recently been stratigraphically and taxonomically revised, and it lived at a time of ecosystem upheaval following the end-Triassic extinction. Here, we report on the results of a femoral osteohistological study of comprising 20 individuals ranging from embryo to skeletally mature. We find major variability in the spacing of the LAGs and infer disparate body masses for individuals at given ontogenetic ages, contradicting previous studies. These findings are consistent with a high degree of growth plasticity in .
早期分支恐龙及其外类群中发育可塑性的证据越来越多。这反映在个体发育过程中形态和组织学变化的不同模式上。在化石中，只有对生长停滞线（LAGs）的骨组织学评估才能揭示骨骼生长的速度。一些较晚分支的非鸟恐龙物种似乎遵循渐近生长模式，随着个体发育年龄的增加，生长速度下降。相比之下，早期分支的蜥脚形亚目恐龙似乎具有可塑性生长，这表明这是恐龙的原始状态。南非蜥脚形亚目恐龙是检验这一点的理想分类单元，因为它有一个完整的个体发育系列，最近在地层学和分类学上得到了修订，并且它生活在三叠纪末灭绝后的生态系统动荡时期。在这里，我们报告了对20个从胚胎到骨骼成熟个体的股骨骨组织学研究结果。我们发现LAGs的间距存在很大差异，并推断出给定个体发育年龄的个体体重不同，这与之前的研究相矛盾。这些发现与该物种高度的生长可塑性一致。
