Canoville Aurore, Chinsamy Anusuya
Department of Biological Sciences, University of Cape Town, Rhodes Gift, 7701, South Africa.
Anat Rec (Hoboken). 2015 Jul;298(7):1237-54. doi: 10.1002/ar.23160. Epub 2015 Apr 23.
The small-bodied stereospondyl Lydekkerina huxleyi, dominated the amphibian fauna of the South African Lower Triassic. Even though the anatomy of this amphibian has been well described, its growth strategies and lifestyle habits have remained controversial. Previous studies attributed the relative uniformity in skull sizes to a predominance of subadult and adult specimens recovered in the fossil record. Anatomical and taphonomic data suggested that the relatively small body-size of this genus, as compared to its Permo-Triassic relatives, could be linked to a shortened, rapid developmental period as an adaptation to maintain successful breeding populations under harsh environmental conditions. Moreover, Lydekkerina's habitat has been hypothesized to be either aquatic or mainly terrestrial. The current study, utilizes bone microstructure to reassess previous hypotheses pertaining to the biology and ecology of Lydekkerina. Various skeletal elements of different-sized specimens are analyzed to understand its growth dynamics, intraskeletal variability, and lifestyle adaptations. Bone histology revealed that our sample comprises individuals at different ontogenetic stages i.e., juveniles to mature individuals. Our results show that these amphibians, despite exhibiting plasticity in growth, experienced an overall faster growth during early ontogeny (thereby attaining sexual maturity sooner), as compared to most other temnospondyls. The microanatomy of the long bones with their thick bone walls and distinctive medullary cavity suggests that Lydekkerina may have been amphibious with a tendency to be more terrestrial. Our study concludes that Lydekkerina employed a peculiar growth strategy and lifestyle adaptations, which enabled it to endure the harsh, dry conditions of the Early Triassic.
小型的立体椎类两栖动物赫氏利德克氏螈在南非下三叠统的两栖动物群中占主导地位。尽管这种两栖动物的解剖结构已有详尽描述，但其生长策略和生活习性仍存在争议。此前的研究将头骨大小的相对一致性归因于化石记录中回收的亚成体和成年标本占多数。解剖学和埋藏学数据表明，与二叠纪-三叠纪的亲属相比，该属相对较小的体型可能与缩短的快速发育时期有关，这是一种适应，以便在恶劣环境条件下维持成功的繁殖种群。此外，利德克氏螈的栖息地被推测为水生或主要为陆生。当前的研究利用骨骼微观结构重新评估先前关于利德克氏螈生物学和生态学的假设。分析不同大小标本的各种骨骼元素，以了解其生长动态、骨骼内变异性和生活方式适应性。骨骼组织学显示，我们的样本包括处于不同个体发育阶段的个体，即幼年到成熟个体。我们的结果表明，这些两栖动物尽管在生长方面表现出可塑性，但与大多数其他离片椎类相比，在个体发育早期总体生长速度更快（从而更早达到性成熟）。长骨的微观解剖结构及其厚厚的骨壁和独特的髓腔表明，利德克氏螈可能是两栖动物，更倾向于陆地生活。我们的研究得出结论，利德克氏螈采用了独特的生长策略和生活方式适应性，使其能够在三叠纪早期恶劣、干燥的条件下生存。
