The Pleistocene epoch occurred between 1.6 million to 11,000 years ago. It is known as the ice age, because large sheets of ice covered much of the earth.
pleistocene
The Ice Age started in the Pleistocene era.
Pleistocene
The Cenozoic or "recent life" era
This is the Cenozoic era, near the boundary of Quaternary and Neogene periods, and therefore near the boundary of the Pleistocene and Pliocene epochs. Please see the link.
Megalodon lived in the Cenozoic era, becoming extinct in the Pleistocene, about 1.5 million years ago.
The horned gopher became extinct in the early Pleistocene era.
Pleistocene
If by "Common Era" you are referring to the era name system, then Christianity coincided with the beginning of the Common Era. In fact, the Common Era is also known as the "Christian Era" or "Current Era". The year 1 CE is the year in which a 6th century monk estimated that Jesus had been born when he created the Common Era calendar.
The Pleistocene epoch
They have been around since at least 300,000 years ago during the Pleistocene.
The Cenozoic is a major geologic era starting at 65 million years ago and encompassing the present. The Pleistocene Epoch is a much smaller division of time that is part of the Quaternary Period of the Cenozoic Era, from 1.8 million years ago to 10,000 years ago.