Devonian

Last updated
Devonian Period
419.2–358.9 million years ago
Scotese 400 ma.png

A map of the world as it appeared during the Emsian epoch of the Early Devonian. (400 ma)

Contents

Mean atmospheric O
2
content over period duration
c. 15 vol %
(75 % of modern level)
Mean atmospheric CO
2
content over period duration
c. 2200 ppm
(8 times pre-industrial level)
Mean surface temperature over period durationc. 20 °C
(6 °C above modern level)
Sea level (above present day)Relatively steady around 189m, gradually falling to 120m through period [1]
Events of the Devonian Period
-420 
-410 
-400 
-390 
-380 
-370 
-360 
Widespread [4]
shrubs & trees
S. America
glaciation begins
Key events of the Devonian Period.
Axis scale: millions of years ago.

The Devonian ( /dɪˈv.ni.ən,də-,dɛ-/ dih-VOH-nee-ən, də-, deh-) [5] [6] is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian, 419.2 million years ago (Mya), to the beginning of the Carboniferous, 358.9 Mya. [7] It is named after Devon, England, where rocks from this period were first studied.

The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established.

Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating almost every known aquatic environment. The ancestors of all four-limbed vertebrates (tetrapods) began adapting to walking on land, as their strong pectoral and pelvic fins gradually evolved into legs. [8] In the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician.

The first ammonites, species of molluscs, appeared. Trilobites, the mollusc-like brachiopods, and the great coral reefs were still common. The Late Devonian extinction which started about 375 million years ago [9] severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida.

The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, and the early formation of the small continent of Euramerica in between.

History

The rocks of Lummaton Quarry in Torquay in Devon played an early role in defining the Devonian period. Lummaton Quarry 1.JPG
The rocks of Lummaton Quarry in Torquay in Devon played an early role in defining the Devonian period.

The period is named after Devon, a county in southwestern England, where a controversial argument in the 1830s, over the age and structure of the rocks found distributed throughout the county was eventually resolved by the definition of the Devonian period in the geological timescale. The Great Devonian Controversy was a long period of vigorous argument and counter-argument between the main protagonists of Roderick Murchison with Adam Sedgwick against Henry De la Beche supported by George Bellas Greenough. Murchison and Sedgwick won the debate and named the period they proposed as the Devonian System. [10] [11] [lower-alpha 1]

While the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, [12] the Devonian extends from the end of the Silurian 419.2 Mya, to the beginning of the Carboniferous 358.9 Mya – in North America, at the beginning of the Mississippian subperiod of the Carboniferous.

In nineteenth-century texts the Devonian has been called the "Old Red Age", after the red and brown terrestrial deposits known in the United Kingdom as the Old Red Sandstone in which early fossil discoveries were found. Another common term is "Age of the Fishes", [13] referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian, and Farlovian stages, the latter three of which are placed in the Devonian. [14]

The Devonian has also erroneously been characterised as a "greenhouse age", due to sampling bias: most of the early Devonian-age discoveries came from the strata of western Europe and eastern North America, which at the time straddled the Equator as part of the supercontinent of Euramerica where fossil signatures of widespread reefs indicate tropical climates that were warm and moderately humid but in fact the climate in the Devonian differed greatly during its epochs and between geographic regions. For example, during the Early Devonian, arid conditions were prevalent through much of the world including Siberia, Australia, North America, and China, but Africa and South America had a warm temperate climate. In the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common.[ citation needed ]

Subdivisions

The Devonian Period is formally broken into Early, Middle and Late subdivisions. The rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System.

Early Devonian

The Early Devonian lasted from 419.2 ± 2.8 to 393.3 ± 2.5 and began with the Lochkovian stage 419.2 ± 2.8 to 410.8 ± 2.5, which was followed by the Pragian from 410.8 ± 2.8 to 407.6 ± 2.5 and then by the Emsian, which lasted until the Middle Devonian began, 393.3 ± 2.7 million years ago. [15] 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 molluscs would dominate the marine fauna until the beginning of the Mesozoic era.

Middle Devonian

The Middle Devonian comprised two subdivisions: first the Eifelian, which then gave way to the Givetian 387.7 ± 2.7 million years ago. During this time the jawless agnathan fishes began to decline in diversity in freshwater and marine environments partly due to drastic environmental changes and partly due to the increasing competition, predation, and diversity of jawed fishes. The shallow, warm, oxygen-depleted waters of Devonian inland lakes, surrounded by primitive plants, provided the environment necessary for certain early fish to develop such essential characteristics as well developed lungs, and the ability to crawl out of the water and onto the land for short periods of time. [16]

Late Devonian

Finally, the Late Devonian started with the Frasnian, 382.7 ± 2.8 to 372.2 ± 2.5, during which the first forests took shape on land. The first tetrapods appeared in the fossil record in the ensuing Famennian subdivision, the beginning and end of which are marked with extinction events. This lasted until the end of the Devonian, 358.9 ± 2.5 million years ago. [15]

Climate

The Devonian was a relatively warm period, and probably lacked any glaciers. The temperature gradient from the equator to the poles was not as large as it is today. The weather was also very arid, mostly along the equator where it was the driest. [17] Reconstruction of tropical sea surface temperature from conodont apatite implies an average value of 30 °C (86 °F) in the Early Devonian. [17] CO
2
levels dropped steeply throughout the Devonian period. The newly evolved forests drew carbon out of the atmosphere, which were then buried into sediments. This may be reflected by a Mid-Devonian cooling of around 5 °C (9 °F). [17] The Late Devonian warmed to levels equivalent to the Early Devonian; while there is no corresponding increase in CO
2
concentrations, continental weathering increases (as predicted by warmer temperatures); further, a range of evidence, such as plant distribution, points to a Late Devonian warming. [17] The climate would have affected the dominant organisms in reefs; microbes would have been the main reef-forming organisms in warm periods, with corals and stromatoporoid sponges taking the dominant role in cooler times. The warming at the end of the Devonian may even have contributed to the extinction of the stromatoporoids.

Paleogeography

Map of Laurentia and Baltica during the Devonian period Bulletin of the Natural Histort Museum. Geology series (2001) (19871804004).jpg
Map of Laurentia and Baltica during the Devonian period
The Paleo-Tethys Ocean opened during the Devonian 380 Ma plate tectonic reconstruction.png
The Paleo-Tethys Ocean opened during the Devonian

The Devonian period was a time of great tectonic activity, as Euramerica and Gondwana drew closer together.

The continent Euramerica (or Laurussia) was created in the early Devonian by the collision of Laurentia and Baltica, which rotated into the natural dry zone along the Tropic of Capricorn, which is formed as much in Paleozoic times as nowadays by the convergence of two great air-masses, the Hadley cell and the Ferrel cell. In these near-deserts, the Old Red Sandstone sedimentary beds formed, made red by the oxidised iron (hematite) characteristic of drought conditions. [19]

Near the equator, the plate of Euramerica and Gondwana were starting to meet, beginning the early stages of the assembling of Pangaea. This activity further raised the northern Appalachian Mountains and formed the Caledonian Mountains in Great Britain and Scandinavia.

The west coast of Devonian North America, by contrast, was a passive margin with deep silty embayments, river deltas and estuaries, found today in Idaho and Nevada; an approaching volcanic island arc reached the steep slope of the continental shelf in Late Devonian times and began to uplift deep water deposits, a collision that was the prelude to the mountain-building episode at the beginning of the Carboniferous called the Antler orogeny. [20]

Sea levels were high worldwide, and much of the land lay under shallow seas, where tropical reef organisms lived. The deep, enormous Panthalassa (the "universal ocean") covered the rest of the planet. Other minor oceans were the Paleo-Tethys Ocean, Proto-Tethys Ocean, Rheic Ocean, and Ural Ocean (which was closed during the collision with Siberia and Baltica).

During the Devonian, Chaitenia, an island arc, accreted to Patagonia. [21]

Life

Marine biota

Spindle diagram for the evolution of vertebrates. The diagram is based on Benton (2005, p. 14). Fish evolution.png
Spindle diagram for the evolution of vertebrates. The diagram is based on Benton (2005 , p. 14).

Sea levels in the Devonian were generally high. Marine faunas continued to be dominated by bryozoa, diverse and abundant brachiopods, the enigmatic hederellids, microconchids and corals. Lily-like crinoids (animals, their resemblance to flowers notwithstanding) were abundant, and trilobites were still fairly common. Among vertebrates, jawless armored fish (ostracoderms) declined in diversity, while the jawed fish (gnathostomes) simultaneously increased in both the sea and fresh water. Armored placoderms were numerous during the lower stages of the Devonian Period and became extinct in the Late Devonian, perhaps because of competition for food against the other fish species. Early cartilaginous (Chondrichthyes) and bony fishes (Osteichthyes) also become diverse and played a large role within the Devonian seas. The first abundant genus of shark, Cladoselache , appeared in the oceans during the Devonian Period. The great diversity of fish around at the time has led to the Devonian being given the name "The Age of Fish" in popular culture.[ citation needed ]

The first ammonites also appeared during or slightly before the early Devonian Period around 400 Mya. [22]

Reefs

A now dry barrier reef, located in present-day Kimberley Basin of northwest Australia, once extended a thousand kilometres, fringing a Devonian continent. Reefs in general are built by various carbonate-secreting organisms that have the ability to erect wave-resistant structures close to sea level. Although modern reefs are constructed mainly by corals and calcareous algae, the main contributors of the Devonian reefs were different: They were composed of calcareous algae, coral-like stromatoporoids, and tabulate and rugose corals, in that order of importance.[ clarification needed ]


Terrestrial biota

By the Devonian Period, life was well underway in its colonisation of the land. The moss forests and bacterial and algal mats of the Silurian were joined early in the period by primitive rooted plants that created the first stable soils and harbored arthropods like mites, scorpions, trigonotarbids [23] and myriapods (although arthropods appeared on land much earlier than in the Early Devonian [24] and the existence of fossils such as Protichnites suggest that amphibious arthropods may have appeared as early as the Cambrian). By far the largest land organism at the beginning of this period was the enigmatic Prototaxites , which was possibly the fruiting body of an enormous fungus, [25] rolled liverwort mat, [26] or another organism of uncertain affinities [27] that stood more than 8 metres (26 ft) tall, and towered over the low, carpet-like vegetation during the early part of the Devonian. Also the first possible fossils of insects appeared around 416 Mya, in the Early Devonian. Evidence for the earliest tetrapods takes the form of trace fossils in shallow lagoon environments within a marine carbonate platform / shelf during the Middle Devonian, [28] although these traces have been questioned and an interpretation as fish feeding traces (Piscichnus) has been advanced. [29]


The greening of land

The Devonian period marks the beginning of extensive land colonisation by plants. With large land-dwelling herbivores not yet present, large forests grew and shaped the landscape. Devonianscene-green.jpg
The Devonian period marks the beginning of extensive land colonisation by plants. With large land-dwelling herbivores not yet present, large forests grew and shaped the landscape.

Many Early Devonian plants did not have true roots or leaves like extant plants although vascular tissue is observed in many of those plants. Some of the early land plants such as Drepanophycus likely spread by vegetative growth and spores. [30] The earliest land plants such as Cooksonia consisted of leafless, dichotomous axes and terminal sporangia and were generally very short-statured, and grew hardly more than a few centimetres tall. [31] By the Middle Devonian, shrub-like forests of primitive plants existed: lycophytes, horsetails, ferns, and progymnosperms had evolved. Most of these plants had true roots and leaves, and many were quite tall. The earliest-known trees appeared in the Middle Devonian [32] These included a lineage of lycopods and another arborescent, woody vascular plant, the cladoxylopsids. [33] (See also: lignin.) These are the oldest-known trees of the world's first forests. By the end of the Devonian, the first seed-forming plants had appeared. This rapid appearance of so many plant groups and growth forms has been called the "Devonian Explosion".

The 'greening' of the continents acted as a carbon sink, and atmospheric concentrations of carbon dioxide may have dropped. This may have cooled the climate and led to a massive extinction event. See Late Devonian extinction.

Animals and the first soils

Primitive arthropods co-evolved with this diversified terrestrial vegetation structure. The evolving co-dependence of insects and seed-plants that characterised a recognisably modern world had its genesis in the Late Devonian period. The development of soils and plant root systems probably led to changes in the speed and pattern of erosion and sediment deposition. The rapid evolution of a terrestrial ecosystem that contained copious animals opened the way for the first vertebrates to seek out a terrestrial living. By the end of the Devonian, arthropods were solidly established on the land. [34]

Late Devonian extinction

The Late Devonian is characterised by three episodes of extinction ("Late D") Extinction Intensity.svg
The Late Devonian is characterised by three episodes of extinction ("Late D")

A major extinction occurred at the beginning of the last phase of the Devonian period, the Famennian faunal stage (the Frasnian-Famennian boundary), about 372.2 Mya, when all the fossil agnathan fishes, save for the psammosteid heterostraci, suddenly disappeared. A second strong pulse closed the Devonian period. The Late Devonian extinction was one of five major extinction events in the history of the Earth's biota, and was more drastic than the familiar extinction event that closed the Cretaceous.

The Devonian extinction crisis primarily affected the marine community, and selectively affected shallow warm-water organisms rather than cool-water organisms. The most important group to be affected by this extinction event were the reef-builders of the great Devonian reef systems.

Amongst the severely affected marine groups were the brachiopods, trilobites, ammonites, conodonts, and acritarchs, as well as jawless fish, and all placoderms. Land plants as well as freshwater species, such as our tetrapod ancestors, were relatively unaffected by the Late Devonian extinction event (there is a counterargument that the Devonian extinctions nearly wiped out the tetrapods [35] ).

The reasons for the Late Devonian extinctions are still unknown, and all explanations remain speculative.[ citation needed ] Canadian paleontologist Digby McLaren suggested in 1969, that the Devonian extinction events were caused by an asteroid impact. However, while there were Late Devonian collision events (see the Alamo bolide impact), little evidence supports the existence of a large enough Devonian crater.

See also

Categories:

Notes

  1. Sedgwick and Murchison coined the term "Devonian system" in Sedgwick & Murchison (1840, p. 701): "We propose therefore, for the future, to designate these groups collectively by the name Devonian system". Sedgwick and Murchison acknowledged William Lonsdale's role in proposing, on the basis of fossil evidence, the existence of a Devonian stratum between those of the Silurian and Carboniferous periods. From Sedgwick & Murchison (1840, p. 690): "Again, Mr. Lonsdale, after an extensive examination of the fossils of South Devon, had pronounced them, more than a year since, to form a group intermediate between those of the Carboniferous and Silurian systems". William Lonsdale stated that in December 1837 he had suggested the existence of a stratum between the Silurian and Carboniferous ones. From Lonsdale (1840, p. 724): "Mr. Austen's communication [was] read December 1837 ... . It was immediately after the reading of that paper ... that I formed the opinion relative to the limestones of Devonshire being of the age of the old red sandstone; and which I afterwards suggested first to Mr. Murchison and then to Prof. Sedgwick".

Related Research Articles

Carboniferous Fifth Period of the Paleozoic Era 359-299 million years ago

The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago (Mya), to the beginning of the Permian Period, 298.9 Mya. The name Carboniferous means "coal-bearing" and derives from the Latin words carbō ("coal") and ferō, and was coined by geologists William Conybeare and William Phillips in 1822.

Ordovician Second period of the Paleozoic Era 485-444 million years ago

The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period 485.4 million years ago (Mya) to the start of the Silurian Period 443.8 Mya.

Permian Sixth and last period of the Paleozoic Era 299-252 million years ago

The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous period 298.9 million years ago (Mya), to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic era; the following Triassic period belongs to the Mesozoic era. The concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the region of Perm in Russia.

The PaleozoicEra is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting from 541 to 251.902 million years ago, and is subdivided into six geologic periods : the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era.

Silurian Third period of the Paleozoic Era 444-419 million years ago

The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago (Mya), to the beginning of the Devonian Period, 419.2 Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out.

Laurasia Northern supercontinent that formed part of the Pangaea supercontinent

Laurasia, a portmanteau for Laurentia and Asia, was the more northern of two minor supercontinents that formed part of the Pangaea supercontinent from c.425 million years ago (Mya) to 200 Mya. It separated from Gondwana 215 to 175 Mya during the breakup of Pangaea, drifting farther north after the split and finally broke apart with the opening of the North Atlantic Ocean c. 56 Mya.

Late Devonian extinction One of the five most severe extinction events in the history of the Earths biota

The Late Devonian extinction was one of five major extinction events in the history of life on Earth. A major extinction, the Kellwasser event, occurred at the boundary that marks the beginning of the last phase of the Devonian period, the Famennian faunal stage, about 360–376 million years ago. Overall, 19% of all families and 50% of all genera became extinct. A second, distinct mass extinction, the Hangenberg event, closed the Devonian period.

In the geological timescale, the Llandovery epoch occurred at the beginning of the Silurian period. The Llandoverian epoch follows the massive Ordovician-Silurian extinction events, which led to a large decrease in biodiversity and an opening up of ecosystems.

Pangaea Supercontinent from the late Paleozoic to early Mesozoic eras

Pangaea or Pangea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from earlier continental units approximately 335 million years ago, and it began to break apart about 175 million years ago. In contrast to the present Earth and its distribution of continental mass, Pangaea was centred on the Equator and surrounded by the superocean Panthalassa. Pangaea is the most recent supercontinent to have existed and the first to be reconstructed by geologists.

Fossils of many types of water-dwelling animals from the Devonian period are found in deposits in the U.S. state of Michigan. Among the more commonly occurring specimens are bryozoans, corals, crinoids, and brachiopods. Also found, but not so commonly, are armored fish called placoderms, snails, sharks, stromatolites, trilobites and blastoids.

Paleontology in Ohio

Paleontology in Ohio refers to paleontological research occurring within or conducted by people from the U.S. state of Ohio. Ohio is well known for having a great quantity and diversity of fossils preserved in its rocks. The state's fossil record begins early in the Paleozoic era, during the Cambrian period. Ohio was generally covered by seawater from that time on through the rest of the early Paleozoic. Local invertebrates included brachiopods, cephalopods, coral, graptolites, and trilobites. Vertebrates included bony fishes and sharks. The first land plants in the state grew during the Devonian. During the Carboniferous, Ohio became a more terrestrial environment with an increased diversity of plants that formed expansive swampy deltas. Amphibians and reptiles began to inhabit the state at this time, and remained present into the ensuing Permian. A gap in the local rock record spans from this point until the start of the Pleistocene. During the Ice Age, Ohio was home to giant beavers, humans, mammoths, and mastodons. Paleo-Indians collected fossils that were later incorporated into their mounds. Ohio has been the birthplace of many world famous paleontologists, like Charles Schuchert. Many significant fossils curated by museums in Europe and the United States were found in Ohio. Major local fossil discoveries include the 1965 discovery of more than 50,000 Devonian fish fossils in Cuyahoga County. The Ordovician trilobite Isotelus maximus is the Ohio state fossil.

Paleontology in Indiana

Paleontology in Indiana refers to paleontological research occurring within or conducted by people from the U.S. state of Indiana. Indiana's fossil record stretches all the way back to the Precambrian, when the state was inhabited by microbes. More complex organisms came to inhabit the state during the early Paleozoic era. At that time the state was covered by a warm shallow sea that would come to be inhabited by creatures like brachiopods, bryozoans, cephalopods, crinoids, and trilobites. During the Silurian period the state was home to significant reef systems. Indiana became a more terrestrial environment during the Carboniferous, as an expansive river system formed richly vegetated deltas where amphibians lived. There is a gap in the local rock record from the Permian through the Mesozoic. Likewise, little is known about the early to middle Cenozoic era. During the Ice Age however, the state was subject to glacial activity, and home to creatures like short-faced bears, camels, mammoths, and mastodons. After humans came to inhabit the state, Native Americans interpreted the fossil proboscidean remains preserved near Devil's Lake as the bones of water monsters. After the advent of formal scientific investigation one paleontological survey determined that the state was home to nearly 150 different kinds of prehistoric plants.

Paleontology in Illinois

Paleontology in Illinois refers to paleontological research occurring within or conducted by people from the U.S. state of Illinois. Scientists have found that Illinois was covered by a sea during the Paleozoic Era. Over time this sea was inhabited by animals including brachiopods, clams, corals, crinoids, sea snails, sponges, and trilobites.

Paleontology in Pennsylvania

Paleontology in Pennsylvania refers to paleontological research occurring within or conducted by people from the U.S. state of Pennsylvania. The geologic column of Pennsylvania spans from the Precambrian to Quaternary. During the early part of the Paleozoic, Pennsylvania was submerged by a warm, shallow sea. This sea would come to be inhabited by creatures like brachiopods, bryozoans, crinoids, graptolites, and trilobites. The armored fish Palaeaspis appeared during the Silurian. By the Devonian the state was home to other kinds of fishes. On land, some of the world's oldest tetrapods left behind footprints that would later fossilize. Some of Pennsylvania's most important fossil finds were made in the state's Devonian rocks. Carboniferous Pennsylvania was a swampy environment covered by a wide variety of plants. The latter half of the period was called the Pennsylvanian in honor of the state's rich contemporary rock record. By the end of the Paleozoic the state was no longer so swampy. During the Mesozoic the state was home to dinosaurs and other kinds of reptiles, who left behind fossil footprints. Little is known about the early to mid Cenozoic of Pennsylvania, but during the Ice Age it seemed to have a tundra-like environment. Local Delaware people used to smoke mixtures of fossil bones and tobacco for good luck and to have wishes granted. By the late 1800s Pennsylvania was the site of formal scientific investigation of fossils. Around this time Hadrosaurus foulkii of neighboring New Jersey became the first mounted dinosaur skeleton exhibit at the Academy of Natural Sciences in Philadelphia. The Devonian trilobite Phacops rana is the Pennsylvania state fossil.

Paleontology in Georgia (U.S. state)

Paleontology in Georgia refers to paleontological research occurring within or conducted by people from the U.S. state of Georgia. During the early part of the Paleozoic, Georgia was largely covered by seawater. Although no major Paleozoic discoveries have been uncovered in Georgia, the local fossil record documents a great diversity of ancient life in the state. Inhabitants of Georgia's early Paleozoic sea included corals, stromatolites, and trilobites. During the Carboniferous local sea levels dropped and a vast complex of richly vegetated delta formed in the state. These swampy deltas were home to early tetrapods which left behind footprints that would later fossilize. Little is known of Triassic Georgia and the Jurassic is absent altogether from the state's rock record. During the Cretaceous, however, southern Georgia was covered by a sea that was home to invertebrates and fishes. On land, the tree Araucaria grew, and dinosaurs inhabited the state. Southern Georgia remained submerged by shallow seawater into the ensuing Paleogene and Neogene periods of the Cenozoic era. These seas were home to small coral reefs and a variety of other marine invertebrates. By the Pleistocene the state was mostly dry land covered in forests and grasslands home to mammoths and giant ground sloths. Local coal mining activity has a history of serendipitous Carboniferous-aged fossil discoveries. Another major event in Georgian paleontology was a 1963 discovery of Pleistocene fossils in Bartow County. Shark teeth are the Georgia state fossil.

Paleontology in Wisconsin

Paleontology in Wisconsin refers to paleontological research occurring within or conducted by people from the U.S. state of Wisconsin. The state has fossils from the Precambrian, much of the Paleozoic, and the later part of the Cenozoic. Most of the Paleozoic rocks are marine in origin. Because of the thick blanket of Pleistocene glacial sediment that covers the rock strata in most of the state, Wisconsin’s fossil record is relatively sparse. In spite of this, certain Wisconsin paleontological occurrences provide exceptional insights concerning the history and diversity of life on Earth.

Paleontology in Missouri

Paleontology in Missouri refers to paleontological research occurring within or conducted by people from the U.S. state of Missouri. The geologic column of Missouri spans all of geologic history from the Precambrian to present with the exception of the Permian, Triassic, and Jurassic. Brachiopods are probably the most common fossils in Missouri.

Paleontology in Minnesota

Paleontology in Minnesota refers to paleontological research occurring within or conducted by people from the U.S. state of Minnesota. The geologic record of Minnesota spans from Precambrian to recent with the exceptions of major gaps including the Silurian period, the interval from the Middle to Upper Devonian to the Cretaceous, and the Cenozoic. During the Precambrian, Minnesota was covered by an ocean where local bacteria ended up forming banded iron formations and stromatolites. During the early part of the Paleozoic era southern Minnesota was covered by a shallow tropical sea that would come to be home to creatures like brachiopods, bryozoans, massive cephalopods, corals, crinoids, graptolites, and trilobites. The sea withdrew from the state during the Silurian, but returned during the Devonian. However, the rest of the Paleozoic is missing from the local rock record. The Triassic is also missing from the local rock record and Jurassic deposits, while present, lack fossils. Another sea entered the state during the Cretaceous period, this one inhabited by creatures like ammonites and sawfish. Duckbilled dinosaurs roamed the land. The Paleogene and Neogene periods of the ensuing Cenozoic era are also missing from the local rock record, but during the Ice Age evidence points to glacial activity in the state. Woolly mammoths, mastodons, and musk oxen inhabited Minnesota at the time. Local Native Americans interpreted such remains as the bones of the water monster Unktehi. They also told myths about thunder birds that may have been based on Ice Age bird fossils. By the early 19th century, the state's fossil had already attracted the attention of formally trained scientists. Early research included the Cretaceous plant discoveries made by Leo Lesquereux.

Prehistory of the United States US History from the formation of the Earth to history in written form

The prehistory of the United States comprises the occurrences within regions now part of the United States of America during the interval of time spanning from the formation of the Earth to the documentation of local history in written form. At the start of the Paleozoic era, what is now "North" America was actually in the southern hemisphere. Marine life flourished in the country's many seas, although terrestrial life had not yet evolved. During the latter part of the Paleozoic, seas were largely replaced by swamps home to amphibians and early reptiles. When the continents had assembled into Pangaea drier conditions prevailed. The evolutionary precursors to mammals dominated the country until a mass extinction event ended their reign.

Evolution of fish The origin and diversification of fish through geologic time

The evolution of fish began about 530 million years ago during the Cambrian explosion. It was during this time that the early chordates developed the skull and the vertebral column, leading to the first craniates and vertebrates. The first fish lineages belong to the Agnatha, or jawless fish. Early examples include Haikouichthys. During the late Cambrian, eel-like jawless fish called the conodonts, and small mostly armoured fish known as ostracoderms, first appeared. Most jawless fish are now extinct; but the extant lampreys may approximate ancient pre-jawed fish. Lampreys belong to the Cyclostomata, which includes the extant hagfish, and this group may have split early on from other agnathans.

References

  1. Haq, B. U.; Schutter, SR (2008). "A Chronology of Paleozoic Sea-Level Changes". Science. 322 (5898): 64–68. Bibcode:2008Sci...322...64H. doi:10.1126/science.1161648. PMID   18832639. S2CID   206514545.
  2. Parry, S. F.; Noble, S. R.; Crowley, Q. G.; Wellman, C. H. (2011). "A high-precision U–Pb age constraint on the Rhynie Chert Konservat-Lagerstätte: time scale and other implications". Journal of the Geological Society. London: Geological Society. 168 (4): 863–872. doi:10.1144/0016-76492010-043.
  3. Kaufmann, B.; Trapp, E.; Mezger, K. (2004). "The numerical age of the Upper Frasnian (Upper Devonian) Kellwasser horizons: A new U-Pb zircon date from Steinbruch Schmidt(Kellerwald, Germany)". The Journal of Geology. 112 (4): 495–501. Bibcode:2004JG....112..495K. doi:10.1086/421077.
  4. Algeo, T. J. (1998). "Terrestrial-marine teleconnections in the Devonian: links between the evolution of land plants, weathering processes, and marine anoxic events". Philosophical Transactions of the Royal Society B: Biological Sciences. 353 (1365): 113–130. doi:10.1098/rstb.1998.0195.
  5. Wells, John (3 April 2008). Longman Pronunciation Dictionary (3rd ed.). Pearson Longman. ISBN   978-1-4058-8118-0.
  6. "Devonian". Dictionary.com Unabridged. Random House.
  7. Gradstein, Felix M.; Ogg, James G.; Smith, Alan G. (2004). A Geologic Time Scale 2004. Cambridge: Cambridge University Press. ISBN   978-0521786737.CS1 maint: ref=harv (link)
  8. Amos, Jonathan. "Fossil tracks record 'oldest land-walkers'". news.bbc.co.uk. BBC News. Retrieved 24 December 2016.
  9. Newitz, Annalee (13 June 2013). "How do you have a mass extinction without an increase in extinctions?". The Atlantic.
  10. Gradstein, Ogg & Smith (2004)
  11. Rudwick, M.S.J. (1985). The great Devonian controversy: The shaping of scientific knowledge among gentlemanly specialists . Chicago: University of Chicago Press.
  12. Gradstein, Ogg & Smith 2004.
  13. Farabee, Michael J. (2006). "Paleobiology: The Late Paleozoic: Devonian". The Online Biology Book. Estrella Mountain Community College.
  14. Barclay, W.J. (1989). Geology of the South Wales Coalfield Part II, the country around Abergavenny. Memoir for 1:50,000 geological sheet (England and Wales) (3rd ed.). pp. 18–19.
  15. 1 2 Cohen, K.M.; Finney, S.C.; Gibbard, P.L.; & Fan, J.-X. (2018). "The ICS International Chronostratigraphic Chart. Episodes 36: 199-204" (PDF). Retrieved 18 June 2019.Cite journal requires |journal= (help)CS1 maint: uses authors parameter (link)
  16. Clack, Jennifer (13 August 2007). "Devonian climate change, breathing, and the origin of the tetrapod stem group". Integrative and Comparative Biology. 47 (4): 510–523. doi: 10.1093/icb/icm055 . PMID   21672860. Estimates of oxygen levels during this period suggest that they were unprecedentedly low during the Givetian and Frasnian periods. At the same time, plant diversification was at its most rapid, changing the character of the landscape and contributing, via soils, soluble nutrients, and decaying plant matter, to anoxia in all water systems. The co-occurrence of these global events may explain the evolution of air-breathing adaptations in at least two lobe-finned groups, contributing directly to the rise of the tetrapod stem group.
  17. 1 2 3 4 Joachimski, M. M.; Breisig, S.; Buggisch, W. F.; Talent, J. A.; Mawson, R.; Gereke, M.; Morrow, J. R.; Day, J.; Weddige, K. (July 2009). "Devonian climate and reef evolution: Insights from oxygen isotopes in apatite". Earth and Planetary Science Letters. 284 (3–4): 599–609. Bibcode:2009E&PSL.284..599J. doi:10.1016/j.epsl.2009.05.028.
  18. Richardson, John B.; Rodriguez, Rosa M.; Sutherland, Stuart J. (November 29, 2001). "Bulletin of the Natural History Museum, Geology Series". Bulletin of the Natural History Museum . 57 (2): 126. Retrieved May 22, 2020.
  19. "Devonian Period". Encyclopedia Britannica. geochronology. Retrieved 15 December 2017.
  20. Blakey, Ron C. "Devonian Paleogeography, Southwestern US". jan.ucc.nau.edu. Northern Arizona University. Archived from the original on 15 April 2010.
  21. Hervé, Francisco; Calderón, Mauricio; Fanning, Mark; Pankhurst, Robert; Rapela, Carlos W.; Quezada, Paulo (2018). "The country rocks of Devonian magmatism in the North Patagonian Massif and Chaitenia". Andean Geology . 45 (3): 301–317. doi: 10.5027/andgeoV45n3-3117 .
  22. Kazlev, M. Alan (May 28, 1998). "Palaeos Paleozoic: Devonian: The Devonian Period – 1". Palaeos. Retrieved 24 January 2019.
  23. Garwood, Russell J.; Dunlop, Jason (July 2014). "The walking dead: Blender as a tool for paleontologists with a case study on extinct arachnids". Journal of Paleontology . 88 (4): 735–746. doi:10.1666/13-088. ISSN   0022-3360. S2CID   131202472 . Retrieved 2015-07-21.
  24. Garwood, Russell J.; Edgecombe, Gregory D. (September 2011). "Early Terrestrial Animals, Evolution, and Uncertainty". Evolution: Education and Outreach. 4 (3): 489–501. doi: 10.1007/s12052-011-0357-y .
  25. Hueber, Francis M. (2001). "Rotted wood-alga fungus: The history and life of Prototaxites Dawson 1859". Review of Palaeobotany and Palynology. 116 (1–2): 123–159. doi:10.1016/s0034-6667(01)00058-6.
  26. Graham, Linda E.; Cook, Martha E.; Hanson, David T.; Pigg, Kathleen B.; Graham, James M. (2010). "Rolled liverwort mats explain major Prototaxites features: Response to commentaries". American Journal of Botany. 97 (7): 1079–1086. doi:10.3732/ajb.1000172. PMID   21616860.
  27. Taylor, Thomas N.; Taylor, Edith L.; Decombeix, Anne-Laure; Schwendemann, Andrew; Serbet, Rudolph; Escapa, Ignacio; Krings, Michael (2010). "The enigmatic Devonian fossil Prototaxites is not a rolled-up liverwort mat: Comment on the paper by Graham et al.(AJB 97: 268–275)". American Journal of Botany. 97 (7): 1074–1078. doi:10.3732/ajb.1000047. PMID   21616859.
  28. Niedźwiedzki (2010). "Tetrapod trackways from the early middle Devonian period of Poland". Nature . 463 (7277): 43–48. Bibcode:2010Natur.463...43N. doi:10.1038/nature08623. PMID   20054388. S2CID   4428903.
  29. Lucas (2015). "Thinopus and a Critical Review of Devonian Tetrapod Footprints". Ichnos . 22 (3–4): 136–154. doi:10.1080/10420940.2015.1063491. S2CID   130053031.
  30. Zhang, Ying-ying; Xue, Jin-Zhuang; Liu, Le; Wang, De-ming (2016). "Periodicity of reproductive growth in lycopsids: An example from the Upper Devonian of Zhejiang Province, China". Paleoworld. 25 (1): 12–20. doi:10.1016/j.palwor.2015.07.002.
  31. Gonez, Paul; Gerrienne, Philippe (2010). "A new definition and a lectotypification of the genus Cooksonia Lang 1937". International Journal of Plant Sciences. 171 (2): 199–215. doi:10.1086/648988. S2CID   84956576.
  32. Smith, Lewis (19 April 2007). "Fossil from a forest that gave Earth its breath of fresh air". The Times. London. Retrieved 1 May 2010.
  33. Hogan, C. Michael (2010). "Fern". In Basu, Saikat; Cleveland, C. (eds.). Encyclopedia of Earth. Washington DC: National Council for Science and the Environment.
  34. Gess, R.W. (2013). "The earliest record of terrestrial animals in Gondwana: A scorpion from the Famennian (Late Devonian) Witpoort Formation of South Africa". African Invertebrates . 54 (2): 373–379. doi: 10.5733/afin.054.0206 .
  35. McGhee, George R. (2013). When the invasion of land failed: The legacy of the Devonian extinctions. New York: Columbia University Press. ISBN   9780231160568.