Horse diversity through the ages.

This study explores the diversity and evolution of horses, highlighting factors that influenced their survival, extinction, and diversity across different continents over time. It also underscores the impact of environmental conditions, such as climate and vegetation, in shaping this diversity.

Key Findings

• The research outlines the evolutionary journey of horses (Family Equidac), classifying them as important herbivores in the Tertiary and Quaternary mammalian faunas worldwide. The horses’ specialized teeth and digestive systems made them top fibre consumers, with an ability to effectively shred even tough vegetable matter. This characteristic made them an essential part of their ecosystems.
• There’s a discussion about the changing dietary habits of these horses – from being browsers or mixed feeders to becoming grazers. This transition made them key players in paving the way for more selective grazers.
• The study explores how fossil grazing horses might have had a similar role in their ecological timelines. It mentions the possibility of all-equid successions during the middle and late Tertiary when horses were diverse both taxonomically and ecologically.

The Impact of Changing Climate and Vegetation

• The research details how variations in horse diversity across different continents at different time periods were influenced by continental configurations, environmental conditions like climate and vegetation.
• An increase in equid diversity during the Miocene in North America is suggested to be a result of a climatic shift. This shift lead to more open woodland-savanna replacing forests, providing a richer variety of forage for ungulate herbivores.
• Conversely, the study suggests that a decrease in diversity during the Pliocene may be linked to the spread of arid steppe, unfavorable for the equids.

Differences Between North America and Eurasia

• The research also draws attention to how differences in diversity between equids and horned ruminants in North America and Eurasia could be linked to differences in climate and vegetation density on these continents.
• The study concludes by proposing a possible vicariance or separation of the two great ungulate families, Equidac in North America and Bovidac in Eurasia.