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No.
The Origins of Cetuceans.
Date
I It should be obvious that Cetaceans) - whales, porpoises and dolphins are mammals.
それは明らかなはずだ。
クジラ目
くじら
ネズミイルカ
They breathe through lungs,
not through gds, and give birth to live
(えら)
イルカ
Young
若して生きるために出産する
Their streamatized bodies, the absence of hind legs, and the presence of a fluke and
合理化 流線
不在
blombele cannot disguise their affinities with land -dwelling mammals.
噴気孔
後ろ足
存在
尾
変装くかくす)
親和性
土地の住居
ホ乳類
(親近感)
However, unlike the cases of sea otters and pinnipeds <seals, seations and walruses,
不以と違って
鰭脚類(せり)アザラシ, アンカ
ラッコ
セイウチ
whose limbs are functional both on land and at sea), it is not easy to envison what the
機能的
想像する
first whales looked like, Extinct but already fully marine cetaceans are known from the
最初のクジラ
絶滅した
完全に海洋性のクジラ
fossil record, How was the gap.
化石記録
Missing until recently
②
were fossils clearly intermediate, or transitional, between land ages.
行方不明 まで 最近だった 明らかに 中級(仲介)
between a walking mammal and a swimming
whale bridged By
This is a question that has puzzled for
過渡期
12 Very exciting discoveries have finally alowed scientists
to
reoonstruct the most
科学者
mammals and cetaceans.
推測する
likely origins of cetaceans. In 1979, a team looking for fossils in northen Pakistan found what
可能性の高起源
北部の※
proveal to be the oolest fossil whale. The fossil was offcially named Pakicetuslin honor of
公式に
名誉を
the country (where the discovery was made). Pakicetus was found embedded in rooks
発
埋め込み化石
formed from river deposits that were 52 million years old. The river that formed
堆積
these deposits was actually not far from an ancient ocean known as the
黒く
Tethys Sea.
※Pakicetus:パキケトゥス:約5,300万年前の水陸両域に生息していた、四つ足の哺乳動物。
現在知られる限りで最古の原始的クジラ類。

ページ2:

No.
details
Date
ファソー
枯学
古細胞る
③ The fossil consists of a complete skull of an archaeocyte, an extinct
完全な 骨
5X37
of modern cetaceans. Although limited to a skull, the Pakicetus fossil
だけ(限定)
on
t
group of ancestors
provides precious!
5
KELSE
Av
あご
貴重な、高価な
詳しい。
the origins of cetaceans. The skull is cetacean -like but its bones lack the
起源原
クジラ類のような
H
顎骨
不足
enlarged space that is filled with fat or oil and used for
receiving
underwater
lu
拡大した
fee
見つける
耳の開口部
lan
ダイビング
a group of
loce
Su
open ocean.
外洋
th
On
sound, in modern whales. Paticetus probably detected sound through the ear opening
as in land mammals. The skull also lacks a blowhole, another cetacean adoptation for
H
Other features, however, show experts that Paticetus is a transitional form between a
特徴
専門家
過渡期
diving
extinct flesh-eating mammals, the mesonychids, and cetaceons. It has been suggested that
fold食食べ物を与える食べた
メソニギ
Paficetus, fed on for in stellen water and was not yet adapted for life in the
供給
浅
I gave birth on land.
It probably bred and gave
④Another major discovery was made in Egypt in 1989. Several skeletons of another
I
いくつかの
(Basilosaurus) were found in sediments left by the Tethys Sea and now exposed.
沈殿物
初期のクジラ
Sahara desert. This whale lived around 40 million years ago, 12 million
Years
early whale,
初期の
in the
after Pakicetus
Many incomodate skeletons were found but they included, for the first time in an
不完全な
archaeocyte, a complete hind leg that features a foot with three tiny toes. Such
3つ
ごくちざ足の指
legs would have been for the small to have supported the 50-feet- long Basilosaurus
1112377
フィート
on land. Basilosaurus was wudaubtedly a fully marine whale with possibly nonfunctional,
一同格
and
or vestigial bindulge.
尾の名残り
疑いなく
完全に海の
何とかして
不機能的
mu