Fusion Patterns in the Skulls of Modern Archosaurs Reveal That Sutures Are Ambiguous Maturity Indicators for the Dinosauria.
Fusion Patterns in the Skulls of Modern Archosaurs Reveal That Sutures Are Ambiguous Maturity Indicators for the Dinosauria.
复制标题
DOI：
10.1371/journal.pone.0147687
复制
发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Evans DC
中科院分区：
文献类型：
--
作者：
Bailleul AM;Scannella JB;Horner JR;Evans DC
脊椎动物头骨的缝合线通常在生命早期开放，成熟后慢慢闭合。所有脊椎动物都遵循这种逐渐缝合的模式的假设已经被用来评估非鸟类恐龙化石遗骸的成熟度。在这里，我们在恐龙现存的系统发育支架中的两个成员，emu，Dromaius novaehollandiae和美洲扬子鳄，密西西比扬子鳄，通过研究它们头骨缝合融合的序列和时间来验证这一假设。正如预期的那样，在个体发育过程中，鸵鸟头骨上的几乎所有缝合线都逐渐闭合(即它们变得更窄)，然后消失。然而，在美洲扬子鳄中，36条缝合线中只有两条完全消失，而且是在胚胎发育期间。令人惊讶的是，随着成熟度的提高，与年轻、较小的个体相比，大型个体的许多鳄鱼缝合线变得更宽。对美国扬子鳄个体发育系列中的两条缝线和一条并软骨的组织学和组织形态计量学分析证实了我们的形态观察。这种缝合增宽的模式可能反映了个体发育过程中的摄食生物力学和饮食变化。我们的发现表明，在现存的原始龙中并不总是观察到渐进性缝合闭合，因此表明颅缝融合是评估非鸟类恐龙成熟度的一个模棱两可的指标。
The sutures of the skulls of vertebrates are generally open early in life and slowly close as maturity is attained. The assumption that all vertebrates follow this pattern of progressive sutural closure has been used to assess maturity in the fossil remains of non-avian dinosaurs. Here, we test this assumption in two members of the Extant Phylogenetic Bracket of the Dinosauria, the emu, Dromaius novaehollandiae and the American alligator, Alligator mississippiensis, by investigating the sequence and timing of sutural fusion in their skulls. As expected, almost all the sutures in the emu skull progressively close (i.e., they get narrower) and then obliterate during ontogeny. However, in the American alligator, only two sutures out of 36 obliterate completely and they do so during embryonic development. Surprisingly, as maturity progresses, many sutures of alligators become wider in large individuals compared to younger, smaller individuals. Histological and histomorphometric analyses on two sutures and one synchondrosis in an ontogenetic series of American alligator confirmed our morphological observations. This pattern of sutural widening might reflect feeding biomechanics and dietary changes through ontogeny. Our findings show that progressive sutural closure is not always observed in extant archosaurs, and therefore suggest that cranial sutural fusion is an ambiguous proxy for assessing maturity in non-avian dinosaurs.