世界最大の足跡化石
ロートサウルス（Rhoetosaurus）
オーストラリアの恐竜
何しろ広い個人の農場ですので勝手に車を乗り入れ、住宅と作業場で大きな声で住人を捜したのですが、たぶんどこかで作業をしているでしょう誰も返事をしてくれません。
家までの間に古い掘削現場の様になっている所がありましたのでここだろうと目星をつけて地層を観察。
やむなく引き返したところの道路上で近隣の人と話が出来ました。
聞くところに依りますと恐竜が発掘されてから既に４人も持ち主が変わっているし、昔の農場から比べると５分の１ぐらいに分割されてしまっているそうで現在のオーナーはここで恐竜が発見された事も知らないのではないかと言われました。
まぁ実際発見されたのが１９２４年ですから第一次世界大戦のすぐ後かな。
以後続けて発掘した話しもなさそうだし、もし土地が売りに出たなら買いたい。
その前に宝くじでも買わなくっちゃ。
ロートサウルス（Rhoetosaurus Brownei）は１９２４年にDurham Douns Station（ダーハムダウンズ農場）で発見されました。
Injune Creek bed (Hutton Sandstone)の地層からです。
体長は１８ｍ。ヒップ高４ｍ。棲息１９０mya、ジュラ紀の前期Toarcian Stage。巨大植物食恐竜。
0ne of Australia's largest dinosaurs was Rhoetosaurus Brownei, a giant plant-eater that lived in Queensland about 190 million years ago, during the Lower Jurassic Period（Toarcian Stage）.
Rhoetosaurus is known from a single specimen discovered in 1924.
lts fossilised bones were found in a rocky gully on Taloona Station, near Roma in the south west of the state.
The dinosaur was named after the station manager, A.J.Browne, who sent some of the bones to the Queensland Museum and later helped recover more of the skeleton, including parts of the neck, back, tail, ischium, ribs and femur.
The lower part of the animal's right hind leg and near complete foot were collected from the same area by Museum scientists in 1976.
Rhoetosaurus
Rhoetosaurus was a sauropod dinosaur and its name comes from Rhoetos, a mythological Greek giant and saurus meaning lizard.
Sauropods were long-necked, big-bodied reptiles that carried their long tails in the air.
They were quadrupeds（four-footed） and they existed in many parts of the world, probably from about 210 million years ago （at the start of the Jurassic Period） to 65 million years ago （at the end of the Cretaceous Period）.
The sauropod group included the largest land animals of all time.
There were two subgroups exemplified by Seismosaurus （longest） with long tails and big hindlegs, and Brachiosaurus （heaviest） with big necks and forelegs, shorter hind legs and tails．
The hind feet of a sauropod （and in some brachiosaurs, possibly the front feet too） were padded with connective tissue like those of an elephant. This spread the animal's weight over a large area （reduced the pressure on the feet） and cushioned the bones.
So far, sauropod remains have been found on all continents except Antarctica and fossilised eggs, believed to have come from sauropods, have been found in Europe, North America, and Asia.
Rhoetosaurus is important because it is one of the oldest known sauropods.
Although the Rhoetosaurus skeleton is incomplete, by comparing it with sauropods from other parts of the world, scientists have been able to reconstruct the form of the living dinosaur and build up a picture of how it may have lived.
Rhoetosaurus brownei
The fossilised bones of Rhoetosaurus are immense. The femur（thigh bone）, for example, is 1.5m long. Rhoetosaurus measured 3.4 m tall at the hip, a little shorter at the shoulder and 14 m to 17 m from its snout to the tip of its tail.
Rhoetosaurus may have weighed more than 20 tonnes-as much as four elephants. Large as this is, it is possible that Brachiosaurus, a sauropod from Africa, North America and Europe, may have weighed between 60 and 80 tonnes.
Two North American sauropods, Supersaurus and Ultrasaurus, may have been even bigger.
Every large animal has to adapt to the problems of weight and Rhoetosaurus was no exception. Its legs had to support the body's weight, and withstand the impact of stepping without the pressure becoming too great for the joint cartilages.
To help overcome this weight problem, sauropods developed light-weight trunk vertebrae. In Rhoetosaurus the centres of the trunk vertebrae were apparently made of cartilage, a lighter and more elastic tissue than bone, and had a very thin surface coating of bone.
This reduced the weight of the skeleton without significantly reducing its rigidity.
ln the fossils from Taloona Station, the cartilage decayed after the animal died and the cavity of each vertebra was filled with sand and twigs which slowly turned to rock.
Like other sauropods, Rhoetosaurus had a very long neck which was flexible enough to have allowed the animal to feed at ground level or to have stretched up to the tree-tops for food.
A single vertebra from the neck is about 2 1/2 times as long as a vertebra from the back. The neck vertebrae, as well as those from the animal's tail, were very strong. Although a sauropod could strike fearful blows with its neck, its most powerful defensive weapon was its long supple tail. Massive muscles attached to the tail venebrae, and more supple joints at the base and tip of the tail, allowed the tail to be swept around with great agility and force.
Some sauropods had long tapering tails with whiplash-like ends.
Even though the end of its tail has not been preserved, scientists believe Rhoetosaurus had a whiplash tail because of other modified bones that have been found higher in the tail.
以上の情報はクイーンズランド博物館より
