研究稱，恐龍不是冷血動物

研究稱，恐龍不是冷血動物

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.

恐龍可能不是我們曾經(jīng)認(rèn)為的冷血殺手，至少在某種程度上不是。新的研究表明，史前巨獸可能有能力調(diào)節(jié)它們的體溫，就像今天的鳥類一樣，這可能會改變我們對鳥類進化的了解。

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.

耶魯大學(xué)的科學(xué)家們采用了一種名為塊狀同位素古溫學(xué)的新技術(shù)來分析恐龍蛋殼的化學(xué)成分，專門研究了蛋殼化石中碳原子和氧原子的構(gòu)成。當(dāng)這些原子的順序已知后，研究人員說他們可以計算出母親下蛋時的內(nèi)部溫度。

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).

來自六千九百萬到七千五百萬年前的蛋殼化石被測試，每一個都代表了三個主要的恐龍類群——鳥臀目、蜥腳類和獸腳亞目——其中一些與鳥類有更密切的關(guān)系，另一些只是遠(yuǎn)親。以食肉的雙足獸腳亞目恐龍來說，計算得到的蛋在38°C、27°C和28°C(分別為100.4°F、80.6°F和82.4°F)，而鴨嘴恐龍則在44°C(111°C) F).這兩個物種都來自加拿大。第三個來自羅馬尼亞的物種，Megaloolithus，計算在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.

來自冷血無脊椎動物和溫血鳥類的現(xiàn)代蛋殼是從加拿大阿爾伯塔省、羅馬尼亞的同一地區(qū)采集的，目的是確定當(dāng)?shù)氐皻拥幕€溫度。傷齒龍標(biāo)本10ºC度(18 Fº)比他們的環(huán)境,溫暖的慈母龍(不像其他兩個樣品)保存完好的15ºC度(27ºF),和Megaloolithus樣本3ºC和6ºC度(大約5º和11ºF)溫暖。

“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.

“我們的發(fā)現(xiàn)表明，新陳代謝使溫度高于環(huán)境的能力是恐龍早期進化的特征。”該研究的第一作者羅賓·道森在一份聲明中說，道森是耶魯大學(xué)的博士生，現(xiàn)在是馬薩諸塞大學(xué)阿姆赫斯特分校的博士后研究員。道森補充說，恐龍的三個主要分支的特點是溫暖的體溫，或能夠代謝控制它們的體溫調(diào)節(jié)。

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.

化石碳酸鹽的保存可能會影響結(jié)果，因此研究人員首先使用掃描電子顯微鏡檢查蛋殼，以確保蛋殼大致相同的形狀。結(jié)果表明，恐龍的體型和生長速度并不一定代表體溫，這是之前人們所認(rèn)為的。此外，他們的工作為正在進行的關(guān)于鳥類從恐龍進化而來的討論增加了內(nèi)容，特別是關(guān)于羽毛的生物學(xué)用途。2014年之前的研究表明，恐龍可能介于冷血動物和溫血動物之間。

“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.”

道森說:“在獸腳亞目恐龍向現(xiàn)代鳥類進化的過程中，由于體型的縮小，濃密的羽毛可能主要是為了保暖。后來，羽毛可能被用來性展示或飛行。”

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