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Cambrian Period 570-800 MYA
The lower boundary of the Cambrian was traditionally set at the earliest appearance of early arthropods known as trilobites and also unusual forms known as archeocyathids (literally 'ancient cup') that are thought to be the earliest sponges and also the first non-microbial reef builders. -
Ordovician
In the Early Ordovician, trilobites were joined by many new types of organisms, including tabulate corals, strophomenid, rhynchonellid, and many new orthid brachiopods, bryozoans, planktonic graptolites and conodonts, and many types of molluscs and echinoderms, including the ophiuroids ("brittle stars") and the first sea stars. -
Silurian
The Silurian was the first period to see macrofossils of extensive terrestrial biota, in the form of moss forests along lakes and streams.Coral reefs made their first appearance during this time, built by extinct tabulate and rugose corals. The first bony fish, the Osteichthyes, appeared, represented by the Acanthodians covered with bony scales; fishes reached considerable diversity and developed movable jaws, adapted from the supports of the front two or three gill arches. -
Devonian
The first tetrapods, members of the [lobe-finned fish] clade (Sarcopterygii), appeared in the fresh and brackish waters of the later Devonian, which then give rise to the first Amphibians.
Early Devonian plants did not have roots or leaves like the plants most common today, and many had no vascular tissue at all. They probably spread largely by vegetative growth, and did not grow much more than a few centimeters tall. -
Carboniferous
One of the greatest evolutionary innovations of the Carboniferous was the amniote egg, which allowed for the further exploitation of the land by certain tetrapods. These included the earliest Sauropsid reptiles (Hylonomus), and the earliest known synapsid (Archaeothyris).The main Early Carboniferous plants were the Equisetales (Horse-tails), Sphenophyllales (vine-like plants), Lycopodiales (Club mosses), Lepidodendrales (scale trees), Filicales (Ferns). -
Permian
Terrestrial life in the Permian included diverse plants, fungi, arthropods, and various types of tetrapods. The period saw a massive desert covering the interior of the Pangaea. The warm zone spread in the northern hemisphere, where extensive dry desert appeared. -
Triassic
The Triassic climate was generally hot and dry, forming typical red bed sandstones and evaporites. There is no evidence of glaciation at or near either pole; in fact, the polar regions were apparently moist and temperate, a climate suitable for reptile-like creatures. Pangaea's large size limited the moderating effect of the global ocean; its continental climate was highly seasonal, with very hot summers and cold winters. -
Jurassic
The arid, continental conditions characteristic of the Triassic steadily eased during the Jurassic period, especially at higher latitudes; the warm, humid climate allowed lush jungles to cover much of the landscape. On land, large archosaurian reptiles remained dominant. The Jurassic was the golden age of the large herbivorous dinosaurs. -
Cretaceous
The first representatives of many leafy trees, including figs, planes and magnolias, appeared in the Cretaceous. The fauna was dominated by archosaurian reptiles, especially dinosaurs, which were at their most diverse stage. In the seas, rays, modern sharks and teleosts became common. -
Tertiary
At the beginning of the period, mammals replaced reptiles as the dominant vertebrates. Each epoch of the Tertiary was marked by striking developments in mammalian life. The earliest recognizable hominoid relatives of humans such as Proconsul. Modern types of birds, reptiles, amphibians, fish, and invertebrates were either already numerous at the beginning of the period or appeared early in its history. Modern families of flowering plants evolved. -
Quaternary
The 2.6 million years of the Quaternary represents the time during which recognizable humans existed. Over this short a time period, the total amount of continental drift was less than 100 km, which is largely irrelevant to palaeontology. Nonetheless, the geological record is preserved in greater detail than that for earlier periods, and is most relatable to the maps of today, revealing in the second half of the twentieth century its own series of extraordinary landform changes.
