新たな進化学的分析により、爬虫類の皮膚に見られる骨（皮骨）は共通の祖先から受け継がれたものではなく、複数のトカゲの系統でそれぞれ独自に進化したものであることが明らかになった。研究チームは、化石と計算手法を用いて3億2000万年にわたるこの形質の変遷を追跡した。オーストラリアのオオトカゲは、一度失った鎧を数百万年後に再び獲得したという点で特筆される。
Biological Journal of the Linnean Societyに掲載されたこの研究では、現生および絶滅した643種のデータを統合した。その結果、ほとんどのトカゲは1億年以上前のジュラ紀後期から白亜紀初期にかけて初めて皮骨を獲得したことが判明した。これらの骨質の構造は、ブラキオサウルスやステゴサウルスなどの恐竜が生きていた当時、気候変動や捕食者から身を守る上で生存を助ける役割を果たしていたと考えられる。
The tiny arms of Tyrannosaurus rex likely evolved as giant predatory dinosaurs shifted to using their massive skulls and jaws for hunting, according to new research. Scientists examined dozens of theropod species and found a strong connection between shrinking forelimbs and robust skulls. The study suggests this change occurred as predators targeted enormous prey.
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Small fossils of Liaoningosaurus paradoxus, once thought to represent a miniature species of armored dinosaur, have been confirmed as juveniles, including some less than a year old and a possible hatchling. Researchers analyzed bone growth patterns to reach this conclusion, challenging earlier ideas about the animal's size and lifestyle. The discovery provides insights into early development of ankylosaurs.
A crushed dinosaur fossil, long forgotten in a drawer, has been reconstructed by a Virginia Tech undergraduate, unveiling a new species of early carnivorous dinosaur. The specimen, named Ptychotherates bucculentus, belonged to the Herrerasauria group and lived near the end of the Triassic period. Its discovery suggests this ancient dinosaur lineage persisted until the end-Triassic extinction.
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New research suggests that young dinosaurs became independent quickly, forming their own groups and occupying different ecological niches from their parents, unlike mammals with extended parental care. This distinction could reshape understandings of Mesozoic ecosystems. The study, led by Thomas R. Holtz Jr. from the University of Maryland, was published in the Italian Journal of Geosciences.