Marsupial First Appearance: Lower Cretaceous

The earliest evidence for the existence of marsupials dates back to the Lower Cretaceous period.

Geologic Time Period Overview

• Lower Cretaceous: This period (approximately 145 to 100.5 million years ago) is recognized as the time of the first marsupial origins. Fossil evidence, such as the shrew-like Sinodelphys, supports this.
• Upper Cretaceous: Marsupials were more diverse during this later part of the Cretaceous period, but their origin predates this time.
• Jurassic Periods (Early & Middle): While mammals existed during the Jurassic, the distinct lineage of marsupials is not known to have originated this early. They emerged later in the Cretaceous.

Therefore, the Lower Cretaceous is the geologic time period associated with the first appearance of marsupials.