Scientists have excavated the largest dinosaur 化石 which would have been the largest terrestrial animal on our 行星.
来自的科学家团队 南非以威特沃特斯兰德大学为首的英国和巴西发现了一种 化石 一个新物种的 恐龙 在南非被认为与雷龙有关。 这只侏罗纪早期恐龙重达 26,000 磅，是非洲象的两倍，臀高四米。 它被命名为“Ledumahadi mafube”，在发现它的地区的土著语言塞索托语中意为“黎明时的巨大雷声”。
进化的转变
雷杜马哈迪与蜥脚类恐龙关系密切，包括著名的雷龙和梁龙。 它是一种以植物为食的食草动物，四肢粗壮，是四足动物，即四足行走，姿势类似于现代大象。 与蜥脚类恐龙长而细长的柱状肢相比，Ledumahadi 的前肢更加蜷缩，即它的四肢更加弯曲，就像原始恐龙一样。 他们的祖先只用两条腿走路，他们一定已经适应了用四只腿走路，这就是为什么他们变得更大以支持消化，因为他们是食草动物。
研究人员比较 化石 data from dinosaurs, reptiles etc who walked on two or four legs and they measured limb size and thickness. This is how they concluded Ledumahadi’s posture and its way of walking on all four limbs. It is understood that many other dinosaurs must have experimented walking on all four limbs which could optimally balance a bigger body. Based upon these collective observations, researchers say that Ledumahadi was definitely a ‘transitional’ dinosaur, as it had ‘crouched’ yet very thick limbs to support its large body. Their limb bones– both arms and legs – are very robust and similar in shape to giant sauropod dinosaurs but obviously thicker while sauropods had more slender limbs. The evolution of four-legged postures came before their giant bodies. Just sheer size and elephant-like limb posture helped them, example sauropods, to become one of the most dominant dinosaur groups during the Jurassic era. Ledumahadi definitely represents a transitional stage between two major groups of dinosaurs. The group of early dinosaurs were experimenting with various ways of becoming bigger in size during the first tens of millions of years of their evolution. What it means for research is that the evolutionary transition from a small, bipedal creature to a large, quadrupled sauropod is a complex path and this evolution certainly led to survival and achieving dominance.
The discovery published tells us that even more than 200 million years ago, these dinosaurs were the largest vertebrates to be present on the 行星, and this time period was almost 40-50 million years earlier than giant sauropods were first seen. The new dinosaur is closely related to giant dinosaurs who lived in Argentina around that time supporting the idea that all continents that we see today were assembled as Pangea – a supercontinent comprised of world’s land mass during Early Jurassic. And at that time this region of South Africa was not mountainous as we see it today but was flat and semi-arid with shallow streams. Certainly, it was a thriving ecosystem. Like Ledumahadi, many other dinosaurs – both giant and tiny – roamed the place at the time. It is fascinating that South Africa has helped to understand the rise of giant dinosaurs during Jurassic era.
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来源（S）
McPhee BW 等人 2018. 南非最早侏罗纪的巨型恐龙和早期蜥脚类恐龙向四足动物的过渡。 科学. 28（19）。 https://doi.org/10.1016/j.cub.2018.07.063
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