The Early Devonian is the first of three
epochs comprising the
Devonian
The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
period, corresponding to the Lower Devonian
series. It lasted from and began with the
Lochkovian
The Lochkovian is one of three faunal stages in the Early Devonian Epoch. It lasted from 419.2 ± 3.2 million years ago to 410.8 ± 2.8 million years ago. It marked the beginning of the Devonian Period, and was followed by the Pragian Stage. It is ...
Stage , which was followed by the
Pragian from and then by the
Emsian, which lasted until the
Middle Devonian began, .
During this time, the first
ammonoids appeared, descending from
bactritoid nautiloids. Ammonoids during this time period were simple and differed little from their nautiloid counterparts. These ammonoids belong to the order
Agoniatitida, which in later epochs evolved to new ammonoid orders, for example
Goniatitida and
Clymeniida. This class of
cephalopod
A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...
molluscs would dominate the marine fauna until the beginning of the
Mesozoic
The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...
Era.
References
Geological epochs
*01
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