美洲是否有过马？
中国的一本什么书上说：美洲有原始的马（好像只有小狗大小）。为什么没有演化成现代的马匹，这是一个谜。现在我们知道，这个谜底是：他们的知识太陈旧，又想当然。
美洲曾经有过马匹，并且还是three to five species。大概是具体的分类有不同的意见，所以才有3到5个species的说法。
另外，在美洲，狮子、猎豹、骆驼，虎也是有的。但在第四纪期间，陆续灭绝了。许多还是在第四纪冰川已经结束了，气温回暖时期而灭绝的。许多动物和美洲的印第安人共同生活过。
至于灭绝的具体原因，各种假说都有。其中一个假说是：印第安人狩猎，把这些动物都灭绝了。有人用计算机模拟，断定人类完全能灭绝那些动物。
印第安人基本上没有金属，靠石制的箭头和原始的弓箭，几乎不可能把那么多种的动物都灭绝了。灭绝几种，那还是有可能的。
下面是维基百科在Quaternary extinction event条目罗列的灭绝的动物一览表。仅限于北美地区。当然，这些动物的灭绝的时间不是一致的，前后相去很宽的时间域。
这些灭绝的哺乳动物都有一个特点，就是体型很庞大。和被灭绝的Short-faced
Bear相比，今天的棕熊都是小玩意。
国家地理电视频道上曾播放过介绍的片子，其中的观点，只是许多假说中的某种说法罢了。
The megafaunal extinctions include
twelve genera of edible herbivores (H), and five large, dangerous
carnivores (C). North American extinctions included:
-
American horses,
(Equus, three
to five species) (H)
-
Yukon wild ass (Equus lambei) (H)
-
California tapirs (Tapirus californicus and Tapirus merriami)
(H)
-
Vero tapir (Tapirus
veroensis) (H)
-
Western camel (Camelops hesternus) (H)
-
North American llamas (Hemiauchenia)(H)
-
Deer (Cervidae, two genera) (H)
-
Pronghorn (Antilocapridae, two genera, one survived) (H)
-
Stag-moose (Cervalces scotti) (H)
-
Shrub-ox and Harlan's muskox (the Arctic Muskox survived) (H)
-
Ancient Bison (Bison
antiquus) (H)
-
Long-horned bison / Giant bison (Bison latifrons) (H)
-
Giant Beaver (Castoroides,
two species) (H)
-
Saiga (Saiga tatarica) (H)
-
Teratorns (C)
-
Pinckney's Capybara (Neochoerus
pinckneyi) (H)
-
Eremotherium and Nothrotheriops,
megatheriid ground sloths (H)
-
Megalonyx, a megalonychid ground sloth (H)
-
Paramylodon, a mylodontid ground sloth (H)
-
Glyptodonts (H)
-
Pampatheres (H)
-
Short-faced Bear (Arctodus simus, larger than the present Grizzly Bear) (C)
-
Florida Cave Bear (Tremarctos floridanus) (C)
-
Saber-toothed cat (Smilodon fatalis) (C)
-
Scimitar cat (Homotherium
serum) (C)
-
Giant polar bear (Ursus maritimus
tyrannus, it is possible that this giant relative of the
modern polar bear lived in North America) (C)
-
American lion (Panthera leo atrox, larger than the current
African Lion but probably a fairly recent immigrant through Beringia)
(C)
-
American cheetah (Miracinonyx, not a true cheetah, possibly
ancestral) (C)
-
Dire wolf (Canis dirus) (C)
-
Mammoth (Mammuthus), several species (H)
-
American mastodon (Mammut americanum) (H)
-
Flat-headed (Platygonus) & Long-nosed (Mylohyus) peccaries (H)
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