研究称，恐龙不是冷血动物

研究称，恐龙不是冷血动物

Dinosaurs may not have been the cold-blooded killers we once thought they were, at least in part. New research suggests that the prehistoric giants may have had the ability to regulate their body temperatures, not unlike birds of today, which could change what we know about avian evolution.

恐龙可能不是我们曾经认为的冷血杀手，至少在某种程度上不是。新的研究表明，史前巨兽可能有能力调节它们的体温，就像今天的鸟类一样，这可能会改变我们对鸟类进化的了解。

Madison Dapcevich

Scientists at Yale University employed a new technique known as clumped isotope paleothermometry to analyze the chemistry of dinosaur eggshells, looking specifically at the makeup of carbon and oxygen atoms in fossil eggshells. When the order of these atoms is known, researchers say they can calculate the mother’s internal temperature at the time she laid her eggs.

耶鲁大学的科学家们采用了一种名为块状同位素古温学的新技术来分析恐龙蛋壳的化学成分，专门研究了蛋壳化石中碳原子和氧原子的构成。当这些原子的顺序已知后，研究人员说他们可以计算出母亲下蛋时的内部温度。

Fossil eggshells from between 69 and 75-million-years-old were tested, each representing three major dinosaur groups – Ornithischia, Sauropodomorpha, and Theropoda – some of which are more closely related to birds and others that are only distant cousins. Eggs from the Troodon species, a meat-eating bipedal theropod, were calculated at 38ºC, 27ºC, and 28ºC (100.4ºF, 80.6ºF, and 82.4ºF), while the duck-billed dinosaur Maiasaura clocked in at 44ºC (111ºF). Both species were from Canada. A third species from Romania, Megaloolithus, was calculated at 36ºC (nearly 97ºF).

来自六千九百万到七千五百万年前的蛋壳化石被测试，每一个都代表了三个主要的恐龙类群——鸟臀目、蜥脚类和兽脚亚目——其中一些与鸟类有更密切的关系，另一些只是远亲。以食肉的双足兽脚亚目恐龙来说，计算得到的蛋在38°C、27°C和28°C(分别为100.4°F、80.6°F和82.4°F)，而鸭嘴恐龙则在44°C(111°C) F).这两个物种都来自加拿大。第三个来自罗马尼亚的物种，Megaloolithus，计算在36°C(近97°F)。

Petrographic microscope images of dinosaur eggshell from this study. Science Advances

Modern eggshells from cold-blooded invertebrates and warm-blooded bird species were collected from the same areas in Alberta, Canada, and Romania in order to determine a baseline temperature for egg-layers in their local environments. Troodon specimens were 10ºC degrees (18ºF) warmer than their environment, the Maiasaura (not as well preserved as the other two samples) were 15ºC degrees warmer (27ºF), and the Megaloolithus samples were 3ºC and 6ºC degrees (roughly 5ºF and 11ºF) warmer.

来自冷血无脊椎动物和温血鸟类的现代蛋壳是从加拿大阿尔伯塔省、罗马尼亚的同一地区采集的，目的是确定当地蛋壳层的基线温度。伤齿龙标本10ºC度(18 Fº)比他们的环境,温暖的慈母龙(不像其他两个样品)保存完好的15ºC度(27ºF),和Megaloolithus样本3ºC和6ºC度(大约5º和11ºF)温暖。

“What we found indicates that the ability to metabolically raise their temperatures above the environment was an early, evolved trait for dinosaurs,” lead author Robin Dawson, who conducted the research as a doctoral student at Yale and is now a postdoctoral research associate at the University of Massachusetts-Amherst, said in a statement. Dawson added that the three major clades of dinosaurs were characterized by warm body temperatures, or were able to metabolically control their thermoregulation.

“我们的发现表明，新陈代谢使温度高于环境的能力是恐龙早期进化的特征。”该研究的第一作者罗宾·道森在一份声明中说，道森是耶鲁大学的博士生，现在是马萨诸塞大学阿姆赫斯特分校的博士后研究员。道森补充说，恐龙的三个主要分支的特点是温暖的体温，或能够代谢控制它们的体温调节。

Preservation of the fossil carbonates may skew the results, so researchers first examined the eggshells using scanning electron microscopy to ensure that the eggshells were in roughly the same shape. The results suggest that dinosaur body size and growth rate do not necessarily indicate body temperature, as was previously believed. Furthermore, their work adds to an ongoing discussion about the evolution of birds from dinosaurs, particularly about the biological use of feathers. Previous research in 2014 suggested dinosaurs were possibly somewhere between cold- and warm-blooded creatures.

化石碳酸盐的保存可能会影响结果，因此研究人员首先使用扫描电子显微镜检查蛋壳，以确保蛋壳大致相同的形状。结果表明，恐龙的体型和生长速度并不一定代表体温，这是之前人们所认为的。此外，他们的工作为正在进行的关于鸟类从恐龙进化而来的讨论增加了内容，特别是关于羽毛的生物学用途。2014年之前的研究表明，恐龙可能介于冷血动物和温血动物之间。

“It’s possible that dense feathers were primarily selected for insulation, as body size decreased in theropod dinosaurs on the evolutionary pathway to modern birds,” said Dawson. “Feathers could have then later been co-opted for sexual display or flying.”

道森说:“在兽脚亚目恐龙向现代鸟类进化的过程中，由于体型的缩小，浓密的羽毛可能主要是为了保暖。后来，羽毛可能被用来性展示或飞行。”

A dinosaur eggshell fossil in cross-section under a microscope using cross-polarizing light. Notice the clusters of biomineralized calcite crystals radiating out from central nodes, along the interior margin of the shell at the bottom of the image. This and the bumpy surface of the exterior margin (top of image) is usually indicative of titanosaur, sauropod dinosaurs. Image credit: Robin Dawson/Science Advances

Simplified archosaur phylogeny illustrating the taxa investigated in this and previous clumped isotope studies. Science Advances