when did the first mammal appear on earth
late Carboniferous period
title: History of Earth text: vast quantities of particulate matter and vapor into the air that occluded sunlight, inhibiting photosynthesis. 75% of all life, including the non-avian dinosaurs, became extinct, marking the end of the Cretaceous period and Mesozoic era. The first true mammals evolved in the shadows of dinosaurs and other large archosaurs that filled the world by the late Triassic. The first mammals were very small, and were probably nocturnal to escape predation. Mammal diversification truly began only after the Cretaceous-Paleogene extinction event. By the early Paleocene the earth recovered from the extinction, and mammalian diversity increased. Creatures like "Ambulocetus" took to the title: Mammal text: mammals (in Kemp's sense) appeared in the Late Triassic epoch (about 225 million years ago), 40 million years after the first therapsids. They expanded out of their nocturnal [[insectivore]] niche from the mid-Jurassic onwards; The Jurassic "[[Castorocauda]]", for example, was a close relative of true mammals that had adaptations for swimming, digging and catching fish. Most, if not all, are thought to have remained nocturnal (the [[Nocturnal bottleneck]]), accounting for much of the typical mammalian traits. The majority of the mammal species that existed in the [[Mesozoic|Mesozoic Era]] were multituberculates, eutriconodonts and [[spalacotheriid]]s. The earliest known [[metatherian]] is "[[Sinodelphys]]", found title: Mammal text: modern mammalian orders arose in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs, and have been among the dominant terrestrial animal groups from 66 million years ago to the present. The basic body type is quadriped, and most mammals use their four extremities for terrestrial locomotion; but in some, the extremities are adapted for life at sea, in the air, in trees, underground, or on two legs. Mammals range in size from the bumblebee bat to the blue whale - the largest animal on the planet. All modern mammals give birth to live title: Mammal text: late [[Eocene]] through the [[Miocene]]. However, no placental fossils have been found from before the end of the Cretaceous. The earliest undisputed fossils of placentals comes from the early [[Paleocene]], after the extinction of the dinosaurs. In particular, scientists have identified an early Paleocene animal named "[[Protungulatum donnae]]" as one of the first placental mammals. however it has been reclassified as a non-placental eutherian. Recalibrations of genetic and morphological diversity rates have suggested a [[Maastrichtian|Late Cretaceous]] origin for placentals, and a Paleocene origin for most modern clades. The earliest known ancestor of primates is "[[Archicebus achilles]]" from around 55 million title: Mammal text: 66 million years ago emptied ecological space once filled by non-avian dinosaurs and other groups of reptiles, as well as various other mammal groups, and underwent an exponential increase in body size ([[megafauna#In terrestrial mammals|megafauna]]). Then mammals diversified very quickly; both birds and mammals show an exponential rise in diversity. For example, the earliest known bat dates from about 50 million years ago, only 16 million years after the extinction of the dinosaurs. Molecular phylogenetic studies initially suggested that most placental orders diverged about 100 to 85 million years ago and that modern families appeared in the period from the