英国牛津大学自然历史博物馆Panciroli, Elsa研究团队取得一项新突破。他们的研究发现侏罗纪幼兽化石揭示了早期哺乳动物漫长的生活史。相关论文于2024年7月24日发表于国际顶尖学术期刊《自然》杂志上。

在这里，研究人员报道了异常完整的中侏罗世docodontan Krusatodon幼年和成年标本，为早期分化哺乳动物的生活史提供了解剖学数据和见解。研究使用同步加速器x射线显微计算机断层成像技术对化石牙齿中牙骨质生长增量进行成像，以提供中生代哺乳动物生活节奏的证据。成年兽大约7岁，幼体兽约7到24个月大，死亡时正处于用其最后的成年牙替换乳牙列的过程中。

当对现存哺乳动物生活史参数数据集进行分析时，Krusatodon的成年牙齿萌出的相对顺序已经确定，并且在现存哺乳动物中观察到的范围内，但这种发育是延长的，与现存成年体重相当（156g或更少）的哺乳动物相比，这种发育发生在更长的时间内，是其最大寿命的一部分。研究结果显示，早期分化的哺乳动物并没有经历与现存的小型哺乳动物相同的生活史，而在中侏罗世或之后，哺乳动物类群才发生了在较短生命周期内快速生长的根本性转变。

据悉，现存的哺乳动物群体幼年期生长快速，在成年期停止生长。由于缺乏代表幼年个体的化石，了解这种模式在最早的哺乳动物(哺乳动物及其最近灭绝的近亲)中出现受到了一定阻碍。

附：英文原文

Title: Jurassic fossil juvenile reveals prolonged life history in early mammals

Author: Panciroli, Elsa, Benson, Roger B. J., Fernandez, Vincent, Fraser, Nicholas C., Humpage, Matt, Luo, Zhe-Xi, Newham, Elis, Walsh, Stig

Issue&Volume: 2024-07-24

Abstract: Living mammal groups exhibit rapid juvenile growth with a cessation of growth in adulthood. Understanding the emergence of this pattern in the earliest mammaliaforms (mammals and their closest extinct relatives) is hindered by a paucity of fossils representing juvenile individuals. We report exceptionally complete juvenile and adult specimens of the Middle Jurassic docodontan Krusatodon, providing anatomical data and insights into the life history of early diverging mammaliaforms. We used synchrotron X-ray micro-computed tomography imaging of cementum growth increments in the teeth to provide evidence of pace of life in a Mesozoic mammaliaform. The adult was about 7years and the juvenile 7 to 24months of age at death and in the process of replacing its deciduous dentition with its final, adult generation. When analysed against a dataset of life history parameters for extant mammals5, the relative sequence of adult tooth eruption was already established in Krusatodon and in the range observed in extant mammals but this development was prolonged, taking place during a longer period as part of a significantly longer maximum lifespan than extant mammals of comparable adult body mass (156g or less). Our findings suggest that early diverging mammaliaforms did not experience the same life histories as extant small-bodied mammals and the fundamental shift to faster growth over a shorter lifespan may not have taken place in mammaliaforms until during or after the Middle Jurassic.

DOI: 10.1038/s41586-024-07733-1

Source: https://www.nature.com/articles/s41586-024-07733-1