Britannica
Sources used in this answer
How did mammals change during the Tertiary Period?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Tertiary Period
Gypsum cones, which resulted from the evaporation of the Mediterranean Sea during the Messinian Salinity Crisis, in the Sorbas basin, Spain.
During the Tertiary Period, mammals underwent a dramatic evolutionary expansion, rising from small, inconspicuous groups in the late Cretaceous to become the dominant terrestrial animals. This transition was largely triggered by the mass extinction of dinosaurs, which removed major reptilian competitors.1234
Key changes included:
- Adaptive Radiation: Following the Cretaceous, mammals experienced rapid diversification. By the early Eocene, more than 20 orders were established.1
- Faunal Turnover: Archaic groups like multituberculates and condylarths were gradually replaced by modern groups, including primates, rodents, perissodactyls, and artiodactyls.14
- Adaptation to Environment: As global cooling and drying trends created more open grasslands during the Miocene, many herbivores evolved specialized teeth for grazing and longer limbs for running.13
- Migration: Geographic shifts, such as the formation and severance of land bridges, facilitated significant intercontinental migrations, particularly between Eurasia and North America.35
By the end of the period, mammalian communities closely resembled those of the modern world, and the emergence of early primates set the stage for later human evolution.125