Here we examine the bone histology of the femora and humeri of the Western Grey Kangaroo, Macropus fuliginosus. Our results reveal that bone modelling in response to ontogenetic growth and the development of tuberosities on the femur, and especially in the humerus, lead to a highly complex histology. We propose that the alternating fast and slow rates of bone deposition are seasonal, and are likely correlated with heterothermy related to ecological constraints during the summer months. In females, after the fourth growth mark in the femur, there is a distinctive change to a more lamellar textured bone deposition with sparse vascularisation, directly indicating a slowdown in growth. However, in males, the zones remain woven textured and well vascularised, which is indicative of continued fast growth. Here we also report the novel occurrence of a fibrocartilaginous entheses for the attachment of the m. quadratus femoris to the caudal femoral tuberosity. Using a combination of methodologies, we show that perimeter measurements of growth marks provide a reasonable estimation of the age of kangaroos. Additionally, we observed large individuals that have ceased diaphyseal appositional growth of the femur and the humerus, as well as fusion of the distal epiphyses of both bones, though the proximal epiphyses may remain unfused.

中文翻译：

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Macropus fuliginosus 个体发育生长和独特的纤维软骨附着点的发育

在这里，我们检查了西部灰袋鼠 Macropus fuliginosus 的股骨和肱骨的骨组织学。我们的研究结果表明，响应个体发育的骨骼建模和股骨，尤其是肱骨的结节发育，导致了高度复杂的组织学。我们提出，骨沉积的快慢交替是季节性的，并且可能与夏季月份与生态约束相关的异温有关。在女性中，在股骨的第四个生长标记之后，有一个明显的变化，即具有稀疏血管形成的更多层状纹理骨沉积，直接表明生长放缓。然而，在雄性中，这些区域保持编织纹理和良好的血管化，这表明持续快速增长。在这里，我们还报告了用于连接 m 的纤维软骨附着点的新发生。股方肌至股骨结节。使用多种方法的组合，我们表明生长标记的周长测量提供了对袋鼠年龄的合理估计。此外，我们观察到大型个体已停止股骨和肱骨的骨干同位生长，以及两骨远端骨骺的融合，但近端骨骺可能仍未融合。