In the geological timescale , the Middle Devonian epoch (from 393.3 ± 1.2 million years ago to 382.7 ± 1.6 million years ago) occurred during the Devonian period, after the end of the Emsian age.
7-398: The Middle Devonian epoch is subdivided into two stages: Eifelian and Givetian . In the middle Devonian the armored jawless fish known as ostracoderms were declining in diversity and instead the jawed fish were thriving and increasing in diversity in both the oceans and freshwater. The shallow, warm, oxygen-depleted waters of Devonian inland lakes, surrounded by primitive plants, provided
14-508: Is now England . The end of the Eifelian was marked by a biological crisis known as the Kačák Event, a two-part interval of extinction which led to ecological turnover among ammonoids , conodonts , and other free-swimming animals. In deep marine waters, the event is indicated by anoxic black shales. There is evidence for a major pulse of transgression ( sea level rise ) and warming during
21-742: The Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage. North American subdivisions of the Eifelian Stage include Southwood , and part of Cazenovia (or Cazenovian ). The Eifelian is named after the Eifel Mountains of Western Germany , which exposed the GSSP section at
28-661: The Wetteldorf Richtschnitt outcrop. The base of the Eifelian is defined by the start of the Polygnathus partitus conodont zone. This layer lies within the Upper Heisdorf Formation , 1.9 metres (6.2 ft) below the base of the Lauch Formation . The earliest forest is known from the Eifelian stage. Cladoxylopsid trees including Calamophyton and other plants have formed the forest landscape in what
35-540: The environment necessary for certain early fish to develop essential characteristics such as well developed lungs, ability to crawl out of the water and onto the land for short periods of time, possibly in search of food which would be developed by the tetrapods later in the Late Devonian which are descendents of these early fish. The earliest forest grew in the Middle Devonian ( Eifelian ) time. This new environment
42-480: The event. Warming and sea level rise through the Eifelian and beyond would have had major effects on diversity, likely leading to the downfall of several marine biogeographic realms . The cool-water Malvinoxhosan Realm (MXR), on the northwest edge of Gondwana , was decimated as rising temperatures eliminated suitably temperate habitat. Fauna of the Eastern Americas Realm (EAR), which was restricted to
49-457: Was formed by cladoxylopsid trees including Calamophyton . The Taghanic event took place near the end of the Middle Devonian. This article related to the Devonian period is a stub . You can help Misplaced Pages by expanding it . This geochronology article is a stub . You can help Misplaced Pages by expanding it . Eifelian The Eifelian is the first of two faunal stages in
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