ティラノサウルスの“本当の顔”が残念すぎる！ やはり鳥ではなくトカゲ顔だったことが判明（最新研究）
2017.04.11
恐竜界のスーパースター・ティラノサウルスの顔は、超敏感な高性能アンテナのような感覚器官だったかもしれない。アメリカで発見された新種のティラノサウルスの化石の研究結果が学術誌「Scientific Reports」で公開され、話題となっている。論文によれば、ティラノサウルスの顔はまるでクロコダイルのような鱗で覆われており、非常に優れた感覚器官として機能していた可能性があるという。英「Sunday Express」など多数のメディアが報じている。
■新種ティラノサウルスを徹底分析
ティラノサウルスは白亜紀後期（約7200万～6600万年前）に生息していた肉食恐竜だ。地球史上最大かつもっとも恐ろしい肉食獣として広く知られているが、その姿形や生態については未だに謎が多い。
今回調査されたのは、新種のティラノサウルス「Daspletosaurus horneri」の化石である。米国モンタナ州で発見されたもので、体長は約9m、尾の長さは2.2mほどだったと推定されている。米国・カーセッシ大学のトーマス・カー氏らのチームは、この化石の頭蓋骨の形状を細かく調査し、現在のワニや鳥類5種と比較することで皮膚や神経の構造を推定した。
■ティラノサウルスの“最新顔”が完全にワニ
結果、示されたのがティラノサウルスの顔の新たな復元予想図だ。ティラノサウルスの顔は、現在のワニに見られるような触覚感度の高い、大きく平たい鱗で覆われていたという。また、興味深いことに、研究者らはティラノサウルスの顔に三叉神経の痕跡を発見した。
※次頁は、ついにティラノサウルスの“本当の顔”が判明！
三叉神経は動物たちの驚くべき感覚能力、例えば鳥が磁場を感知したり、水辺に沈んだワニが少しの振動から獲物を見つけたりするのに大きく関わっている。カー氏らはティラノサウルスの顔は現代のクロコダイルとよく似て、非常に敏感だったと推測している。ワニの顔面に存在する感覚器の精度は、なんと人間の指先以上ともいわれており、獲物の探知や同定から仲間同士の挨拶、巣の温度調節にまで幅広く活用している。ティラノサウルスも似たような使い方をしていたと考えられる。
今回の推定は、ティラノサウルス上科すべてに応用できるという。恐竜の王者だけあって映像化の機会も多いティラノサウルスは、その時その時の最新の研究結果を盛り込んで、時代ごとに描かれ方が変遷している。以前はワニやトカゲを彷彿とさせるデザインが多かったが、最近では鳥のような顔で描かれがちなティラノサウルス。今回の結果を受け、再びワニ顔に戻るかもしれない。鳥のイメージが強烈だっただけに、「やっぱり巨大トカゲか……」と残念に思った読者もいるかもしれないが、今後の研究によって再び更新される可能性もあるだろう。期待して待とう。
（吉井いつき）
参考：「Scientific Reports」、「EXPRESS」、ほか
参照元 ： TOCANA
New dinosaur REVEALED: Predator almost as big as the LARGEST carnivore ever to walk Earth
A NEW dinosaur dug out of the badlands of Montana has changed the face of T Rex.
PUBLISHED: 00:01, Fri, Mar 31, 2017
A NEW dinosaur dug out of the badlands of Montana has changed the face of T Rex
The predatory beast was almost as big as the largest carnivore ever to stalk the Earth.
–– ADVERTISEMENT ––
And it had features just like a crocodile's - meaning its famous cousin would have looked the same.
Its head was covered by a mask of large, flat scales with regions of armour like skin on the snout and jaws.
Ornamental horns behind the eye were covered by keratin, the hard and shiny material that makes human fingernails.
And the creature, about 30 feet long and more than seven feet tall had no lips - making T Rex even uglier than we even imagined.
The snout would also have been as sensitive to touch as a hand - not that any animal would have been mad enough to stroke it.
The discovery is groundbreaking because it fills a gap in the fossil record of tyrannosaurs.
The species, named Daspletosaurus horneri, meaning 'Frightful Lizard', evolved directly from its older relative, D. torosus, a rare form of evolution called anagenesis where one species gradually morphs into a new one.
Remains from both adults and juveniles were so well preserved scientists were even able to reconstruct the nerves and arteries of the extinct animal. They were roaming the planet around 75 million years ago when they died.
The trigeminal nerve, which is responsible for feeling sensation in the face, as well as biting and chewing, resembled a human's, according to the findings published in Scientific Reports.
Biologist Dr Thomas Carr, of Carthage College, Wisconsin, said: "It turns out tyrannosaurs are identical to crocodylians in that the bones of their snouts and jaws are rough, except for a narrow band of smooth bone along the tooth row.
"In crocodylians, the rough texture occurs deep to large flat scales; given the identical texture, tyrannosaurs had the same covering.
"We did not find any evidence for lips in tyrannosaurs, the rough texture covered by scales extends nearly to the tooth row, providing no space for lips."
He added: "The armour-like skin would have protected tyrannosaurs from abrasions, perhaps sustained when hunting and feeding."
A mule drawn sled was required to haul from the mud the skull and skeleton of the older adult specimen of Daspletosaurus horneri, meaning 'Frightful Lizard'.
The dinosaur graveyard near the Rocky Mountains also included a skull and skeleton, part of the lower jaw and isolated bones from younger adults, as well as bones from juveniles.
The scientists compared tyrannosaur skulls with those of crocodylians, birds and mammals as well as earlier research that matched bone texture with different types of skin covering.
Anaatomist Dr Jayc Sedlmayr, of Louisiana State University, said: "Much of our research went beyond field paleontology - it was generated from lab-based comparative anatomy, the dissection of birds as living dinosaurs and crocodilians as their closest living relatives, and based on the similarities of the facial nerves and arteries we found in those same groups which left a trace on the bone, we were able to then reconstruct in the new tyrannosaur species."
His own research was based on dissecting birds, alligators, crocodiles, lizards and turtles, including injecting their blood vessels and doing blood vessel scans from some of the specimens.
The scientists compared tyrannosaur skulls with those of crocodylians
If a specific nerve or artery went through a particular opening or groove in a bone in both birds and crocodiles, and this is also found in dinosaurs, he could then reconstruct that nerve or artery in the extinct animal.
Explained Dr Sedlmayr: "Our findings of a complex sensory web is especially interesting because it is derived from the trigeminal nerve which has an extraordinary evolutionary history of developing into wildly different 'sixth senses' in different vertebrates - sensing magnetic fields for bird migration, electroreception for predation in the platypus bill or the former whisker pits of dolphins, sensing infrared in pit vipers to identify prey, guiding mammals movements through the use of whiskers, sensing vibrations through the water by alligators, and turning the elephant trunk into a sensitive hand similar to what has been done to the entire face of tyrannosaurs."
The predatory beast was almost as big as the largest carnivore ever to stalk the Earth
Its prey were horned dinosaurs, crested duckbill dinosaurs, dome-headed dinosaurs and smaller theropod dinosaurs. It was the last species of Daspletosaurus to have evolved in the American west.
Dr Sedlmayr said: "In some ways, the facial components of the trigeminal nerve of these dinosaurs mirrors that of humans.
"The human trigeminal nerve provides significant touch sensitivity to the face. It brings back sensation from our facial muscles allowing us to fine tune and coordinate the emotional and social displays so important to human communication.
"This nerve is so sensitive that in pathological conditions, trigeminal neuraligia, it can be responsible for some of the most severe pain our species can endure; in extreme cases, the pain is so great that many people suffering from it end up committing suicide. "
T Rex was bigger than D horneri, around 40 feet long and up to 20 feet tall.
参照元 ： express
2017.04.11
恐竜界のスーパースター・ティラノサウルスの顔は、超敏感な高性能アンテナのような感覚器官だったかもしれない。アメリカで発見された新種のティラノサウルスの化石の研究結果が学術誌「Scientific Reports」で公開され、話題となっている。論文によれば、ティラノサウルスの顔はまるでクロコダイルのような鱗で覆われており、非常に優れた感覚器官として機能していた可能性があるという。英「Sunday Express」など多数のメディアが報じている。
■新種ティラノサウルスを徹底分析
ティラノサウルスは白亜紀後期（約7200万～6600万年前）に生息していた肉食恐竜だ。地球史上最大かつもっとも恐ろしい肉食獣として広く知られているが、その姿形や生態については未だに謎が多い。
今回調査されたのは、新種のティラノサウルス「Daspletosaurus horneri」の化石である。米国モンタナ州で発見されたもので、体長は約9m、尾の長さは2.2mほどだったと推定されている。米国・カーセッシ大学のトーマス・カー氏らのチームは、この化石の頭蓋骨の形状を細かく調査し、現在のワニや鳥類5種と比較することで皮膚や神経の構造を推定した。
■ティラノサウルスの“最新顔”が完全にワニ
結果、示されたのがティラノサウルスの顔の新たな復元予想図だ。ティラノサウルスの顔は、現在のワニに見られるような触覚感度の高い、大きく平たい鱗で覆われていたという。また、興味深いことに、研究者らはティラノサウルスの顔に三叉神経の痕跡を発見した。
※次頁は、ついにティラノサウルスの“本当の顔”が判明！
三叉神経は動物たちの驚くべき感覚能力、例えば鳥が磁場を感知したり、水辺に沈んだワニが少しの振動から獲物を見つけたりするのに大きく関わっている。カー氏らはティラノサウルスの顔は現代のクロコダイルとよく似て、非常に敏感だったと推測している。ワニの顔面に存在する感覚器の精度は、なんと人間の指先以上ともいわれており、獲物の探知や同定から仲間同士の挨拶、巣の温度調節にまで幅広く活用している。ティラノサウルスも似たような使い方をしていたと考えられる。
今回の推定は、ティラノサウルス上科すべてに応用できるという。恐竜の王者だけあって映像化の機会も多いティラノサウルスは、その時その時の最新の研究結果を盛り込んで、時代ごとに描かれ方が変遷している。以前はワニやトカゲを彷彿とさせるデザインが多かったが、最近では鳥のような顔で描かれがちなティラノサウルス。今回の結果を受け、再びワニ顔に戻るかもしれない。鳥のイメージが強烈だっただけに、「やっぱり巨大トカゲか……」と残念に思った読者もいるかもしれないが、今後の研究によって再び更新される可能性もあるだろう。期待して待とう。
（吉井いつき）
参考：「Scientific Reports」、「EXPRESS」、ほか
参照元 ： TOCANA
New dinosaur REVEALED: Predator almost as big as the LARGEST carnivore ever to walk Earth
A NEW dinosaur dug out of the badlands of Montana has changed the face of T Rex.
PUBLISHED: 00:01, Fri, Mar 31, 2017
A NEW dinosaur dug out of the badlands of Montana has changed the face of T Rex
The predatory beast was almost as big as the largest carnivore ever to stalk the Earth.
–– ADVERTISEMENT ––
And it had features just like a crocodile's - meaning its famous cousin would have looked the same.
Its head was covered by a mask of large, flat scales with regions of armour like skin on the snout and jaws.
Ornamental horns behind the eye were covered by keratin, the hard and shiny material that makes human fingernails.
And the creature, about 30 feet long and more than seven feet tall had no lips - making T Rex even uglier than we even imagined.
The snout would also have been as sensitive to touch as a hand - not that any animal would have been mad enough to stroke it.
The discovery is groundbreaking because it fills a gap in the fossil record of tyrannosaurs.
The species, named Daspletosaurus horneri, meaning 'Frightful Lizard', evolved directly from its older relative, D. torosus, a rare form of evolution called anagenesis where one species gradually morphs into a new one.
Remains from both adults and juveniles were so well preserved scientists were even able to reconstruct the nerves and arteries of the extinct animal. They were roaming the planet around 75 million years ago when they died.
The trigeminal nerve, which is responsible for feeling sensation in the face, as well as biting and chewing, resembled a human's, according to the findings published in Scientific Reports.
Biologist Dr Thomas Carr, of Carthage College, Wisconsin, said: "It turns out tyrannosaurs are identical to crocodylians in that the bones of their snouts and jaws are rough, except for a narrow band of smooth bone along the tooth row.
"In crocodylians, the rough texture occurs deep to large flat scales; given the identical texture, tyrannosaurs had the same covering.
"We did not find any evidence for lips in tyrannosaurs, the rough texture covered by scales extends nearly to the tooth row, providing no space for lips."
He added: "The armour-like skin would have protected tyrannosaurs from abrasions, perhaps sustained when hunting and feeding."
A mule drawn sled was required to haul from the mud the skull and skeleton of the older adult specimen of Daspletosaurus horneri, meaning 'Frightful Lizard'.
The dinosaur graveyard near the Rocky Mountains also included a skull and skeleton, part of the lower jaw and isolated bones from younger adults, as well as bones from juveniles.
The scientists compared tyrannosaur skulls with those of crocodylians, birds and mammals as well as earlier research that matched bone texture with different types of skin covering.
Anaatomist Dr Jayc Sedlmayr, of Louisiana State University, said: "Much of our research went beyond field paleontology - it was generated from lab-based comparative anatomy, the dissection of birds as living dinosaurs and crocodilians as their closest living relatives, and based on the similarities of the facial nerves and arteries we found in those same groups which left a trace on the bone, we were able to then reconstruct in the new tyrannosaur species."
His own research was based on dissecting birds, alligators, crocodiles, lizards and turtles, including injecting their blood vessels and doing blood vessel scans from some of the specimens.
The scientists compared tyrannosaur skulls with those of crocodylians
If a specific nerve or artery went through a particular opening or groove in a bone in both birds and crocodiles, and this is also found in dinosaurs, he could then reconstruct that nerve or artery in the extinct animal.
Explained Dr Sedlmayr: "Our findings of a complex sensory web is especially interesting because it is derived from the trigeminal nerve which has an extraordinary evolutionary history of developing into wildly different 'sixth senses' in different vertebrates - sensing magnetic fields for bird migration, electroreception for predation in the platypus bill or the former whisker pits of dolphins, sensing infrared in pit vipers to identify prey, guiding mammals movements through the use of whiskers, sensing vibrations through the water by alligators, and turning the elephant trunk into a sensitive hand similar to what has been done to the entire face of tyrannosaurs."
The predatory beast was almost as big as the largest carnivore ever to stalk the Earth
Its prey were horned dinosaurs, crested duckbill dinosaurs, dome-headed dinosaurs and smaller theropod dinosaurs. It was the last species of Daspletosaurus to have evolved in the American west.
Dr Sedlmayr said: "In some ways, the facial components of the trigeminal nerve of these dinosaurs mirrors that of humans.
"The human trigeminal nerve provides significant touch sensitivity to the face. It brings back sensation from our facial muscles allowing us to fine tune and coordinate the emotional and social displays so important to human communication.
"This nerve is so sensitive that in pathological conditions, trigeminal neuraligia, it can be responsible for some of the most severe pain our species can endure; in extreme cases, the pain is so great that many people suffering from it end up committing suicide. "
T Rex was bigger than D horneri, around 40 feet long and up to 20 feet tall.
参照元 ： express
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