Data from: Palaeobiology of the early sauropodomorph Mussaurus patagonicus inferred from its long bone histology

We present here a detailed histological study of long bones from an ontogenetic series of Mussaurus patagonicus, an early sauropodomorph from the Early Jurassic of Argentina. Twenty long bones, including humeri, femora and fibulae, obtained from thirteen individuals of different body sizes were sampled for histological analysis. In general terms, the cortical bone is formed by a well vascularized fibrolamellar and parallel fibred bone. Except for the smaller individuals, cyclical growth marks (CGMs) are well recorded in all the specimens, but their number and relative position is highly variable. Mussaurus exhibits marked variation regarding relative growth rates, with some individuals growing much faster than others. Such variation affects the size of the adult individuals, which results in a poor correlation between the body size and the age/ontogenetic stage for this taxon. These discrepancies may be related to sexual dimorphism and/or developmental plasticity. Intraspecific variation is also recorded with regard to the growth strategies, which can vary from cyclical, as in other early sauropodomorphs, to continuous, as reported in sauropods. Sexual maturity appears to be reached between 23 and 31 years, which is delayed in comparison to other early sauropodomorphs, but more compatible to derived sauropods. The attainment of somatic maturity appears to be reached about 14 years after the onset of sexual maturity. Mussaurus is a sauropodiform, phylogenetically closer to sauropods than most other sauropodomorphs, and therefore provides critical information for understanding paleobiological aspects relevant to the origin of sauropods and the onset of gigantism in this lineage.本研究针对阿根廷早侏罗世早期蜥脚形亚目（sauropodomorph）物种巴塔哥尼亚穆氏龙（Mussaurus patagonicus）的个体发育序列长骨，开展了详细的组织学研究。研究共采集13具不同体型个体的20块长骨，包括肱骨（humeri）、股骨（femora）与腓骨（fibulae），用于组织学分析。总体而言，该物种的皮质骨由血管丰富的纤维板层骨（fibrolamellar bone）与平行纤维骨构成。除体型较小的个体外，所有标本均清晰记录有周期性生长标记（CGMs），但其数量与相对位置存在显著差异。穆氏龙的相对生长速率存在显著个体差异，部分个体的生长速度远快于其他个体。此类差异会影响成年个体的体型，导致该分类群的体型与年龄/个体发育阶段之间相关性较弱。这些差异可能与性二态性（sexual dimorphism）和/或发育可塑性（developmental plasticity）相关。研究同时记录到种内生长策略变异：其生长模式可如其他早期蜥脚形亚目般呈周期性，也可如蜥脚类（sauropods）一般为持续生长。该物种的性成熟年龄约为23至31年，相较于其他早期蜥脚形亚目有所延迟，但更接近衍生型蜥脚类。躯体成熟则似乎在性成熟起始后约14年达成。穆氏龙属于蜥脚形类（sauropodiform），系统发育上比多数其他蜥脚形亚目更接近蜥脚类，因此可为理解蜥脚类的起源以及该演化支系的体型巨型化（gigantism）起始相关的古生物学特征提供关键信息。