The Florida Museum of Natural History, University of Florida, Gainesville, FL 32611-7800, USA.
Trends Ecol Evol. 1997 May;12(5):182-7. doi: 10.1016/s0169-5347(97)01049-5.
Although vertebrate herbivory has existed on land for about 300 million years, the grazingadaptation, principally developed in mammals, did not appear until the middle Cenozoic about 30 million years ago. Paleontological evidence indicates that grazing mammals diversified at the time of the spread of grasslands. Recently revised fossil calibrations reveal that the grazing mammal guild originated during the early Miocene in South America about 10-15 million years earlier than it did during the late Miocene in the northern hemisphere. Carbon isotopic analyses of extinct grazers' teeth reveal that this guild originated predominantly in C(3) terrestrial ecosystems. The present-day distribution of C(3) and C(4) grasslands evolved on the global ecological landscape since the late Miocene, after about 7 million years ago.
尽管脊椎动物的草食性在陆地上已经存在了大约 3 亿年，但主要在哺乳动物中发展起来的食草适应性直到大约 3000 万年前的中生代中期才出现。古生物学证据表明，食草哺乳动物在草原扩散的同时也在多样化。最近修订的化石校准显示，食草哺乳动物群体起源于南美洲的早中新世，比晚中新世在北半球的起源早了大约 1000 万到 1500 万年。对已灭绝食草动物牙齿的碳同位素分析表明，这个群体主要起源于 C(3)陆地生态系统。自大约 700 万年前的晚中新世以来，C(3)和 C(4)草原在全球生态景观中演化。
