Valsequillo biostratigraphy. III: Equid ecospecies in Paleoindian sites.

This research paper delves into the classification of Pleistocene horse species in North America and their geographical distribution, using their remains found in Paleoindian sites as ecological pointers.

Objective of the Research

• The research aims to utilize advancements in the taxonomy of Pleistocene equids (ancient horses) in North America to scrutinize horse remains found at Paleoindian archaeological sites. These remains serve as ecological index-fossils, aiding in understanding the ecology and climate of different regions during the Pleistocene epoch.

Methodology and Findings

• Researchers successfully sorted horse species in Central Mexico and the Southern Plains based on tooth size alone, excluding two rare larger horses of the Southern Plains.
• The species endemic to these grasslands and south to Central Mexico included Equus pacificus (large), E. conversidens (small), and E. francisci (the smallest).
• The Southern Plains were also inhabited by a specialized grazer, E. excelsus, found at the Burnet and Sandia caves.
• E. occidentalis was detected at the Dry and Sandia caves, denoting another species that existed during this time.
• In the regions west of the Rocky Mountains, E. occidentalis was the dominant horse species.
• Two woodland species, E. fraternus and E. littoralis, were found to the east of the Mississippi River.

Implications of the Study

• This study contributes to the field of biostratigraphy by providing valuable insights into the Pleistocene equid species’ ecological standing and geographical distributions. This can lead to a better understanding of the ancient horse species’ evolution, habitat preferences, and migration patterns.
• The distinct tooth sizes and species assignment offer a fresh approach to classify and study ancient horse species.
• Moreover, the research might also assist in approximating climate conditions of the past by studying the dominant horse species and their feeding habits, which are generally correlated with the type of existing vegetation.