Studies of large herbivorous mammal (ungulate) communities have revealed an association between increased tooth crown height (hypsodonty) and a shift to more arid environments over the Cenozoic. Ecometric analyses have also been used to examine the relationship between current climate conditions and crown height of these communities, and very successfully used to estimate past precipitation. Small herbivorous mammals (rodents and lagomorphs) have been shown to similarly adapt to changing habitats over the Cenozoic, but did so millions of years earlier than larger mammals. Here, we have utilized ecometric methods to examine the relationships between rodent and lagomorph crown height and diversity with current climate conditions, finding strong correlations of community structure parameters with climate, particularly mean annual temperature, maximum temperature of the warmest month, and minimum temperature of the coldest month. We applied the resultant regression equations to well-sampled fossil localities from North America, spanning over 37 million years, allowing estimation of climate conditions in deep time. As expected, estimates show a general pattern of decrease in both precipitation and temperature across North America from 37 Ma to the present. Overall, these findings provide a new broadly-applicable proxy for estimation of Cenozoic climate conditions at a local scale.

对大型草食性哺乳动物（有蹄类动物）群落的研究表明，齿冠高度增加（假齿）与新生代向更干旱环境的转移之间存在关联。经济学分析还被用来检验当前气候条件与这些社区树冠高度之间的关系，并且非常成功地用于估算过去的降水量。小型草食性哺乳动物（啮齿动物和lagomorphs）已显示出类似地适应新生代不断变化的生境，但比大型哺乳动物早了数百万年。在这里，我们利用生态计量方法研究了啮齿动物和lagomorph冠高与多样性与当前气候条件之间的关系，发现了群落结构参数与气候（尤其是年平均气温）的密切相关性，最暖月的最高温度和最冷月的最低温度。我们将所得的回归方程式应用于经过3700万多年的来自北美的采样良好的化石地区，从而可以估算更深的气候条件。不出所料，估计值显示了从37 Ma到现在整个北美降水和温度下降的总体模式。总体而言，这些发现为当地范围内新生代气候条件的估计提供了新的广泛应用的代理。估计值表明，从37 Ma到现在，整个北美的降水和温度均呈下降趋势。总体而言，这些发现为当地范围内新生代气候条件的估计提供了新的广泛应用的代理。估计值表明，从37 Ma到现在，整个北美的降水和温度均呈下降趋势。总体而言，这些发现为当地范围内新生代气候条件的估计提供了新的广泛应用的代理。