トリケラトプス、動き鈍かった？　頭骨ＣＴスキャンで判明―福井県立大

　３本の角を持つ草食恐竜のトリケラトプスは、機敏な動きが苦手だった可能性が高いことが分かったと、福井県立大が１８日発表した。肉食恐竜ティラノサウルスとの格闘シーンがよく描かれるが、実際は突進を繰り返すような戦い方は難しかったようだ。
　トリケラトプスは後期白亜紀の約６８００万～約６６００万年前に生息した角竜類で、大きな角やフリルと呼ばれる襟飾りのような後頭部の構造が特徴。脳の大きさや形は知られていたが、知覚機能などの詳細な解析はされていなかった。
　同大の大学院生、坂上莉奈さんと恐竜学研究所の河部壮一郎准教授は、トリケラトプス２体の頭骨化石をコンピューター断層撮影（ＣＴ）スキャン。脳が収まっていた頭骨の空洞を解析し、脳や神経、血管、内耳の形態を３次元的に復元した。
　その結果、他の角竜類や肉食恐竜と比べ、トリケラトプスは頭部の動きやバランス感覚をつかさどる三半規管が小さい傾向があり、頭や体を速く動かすことが苦手だったと推定された。脳は嗅覚をつかさどる部分が極めて小さく、鼻はあまり利かなかったとみられるという。（2020/09/18-20:30）

The triceratops, a three-horned herbivore dinosaur, highly likely had low agility, researchers from the Fukui Prefectural University said Friday.
   The triceratops is often depicted fighting off the carnivore tyrannosaurus, but the research revealed that it was probably difficult for the herbivore to repeatedly rush at the predator.
   The triceratops lived in the late Cretaceous period some 68 million to 66 million years ago. It had three large horns, and the back of its head flared out, looking like frills. Its brain size and shape were previously known, but there had been no detailed analyses of its abilities.
   Rina Sakagami, a graduate student, and Soichiro Kawabe, associate professor at the Dinosaur Research Institute of the university in Fukui Prefecture, central Japan, took computed tomography scans of fossils of skulls from two triceratops. Analyzing the space in the skulls for dinosaurs' brains, they recreated the brains, nervous systems, blood vessels and inner ears in 3D.
   They found that the triceratops is believed to have had smaller semicircular canals, which are responsible for head movements and sense of balance, than other ceratopsids or carnivores, making it difficult for it to move its head or body swiftly.