360-260 Mya Karoo Ice Age
The Karoo Ice Age from 360–260 Ma (million years ago) was the second major ice age of the Phanerozoic Eon. It is named after the glacial tills found in the Karoo region of South Africa where evidence for this ice age was first clearly identified.
The tectonic assembly of the continents of Euramerica (later with the Uralian orogeny, into Laurasia) and Gondwana into Pangaea, in the Hercynian-Alleghany Orogeny, made a major continental landmass within the Antarctic region, and the closure of the Rheic Ocean and Iapetus Ocean saw disruption of warm water currents in the Panthalassa Ocean and Paleotethys Sea, which led to progressive cooling of summers, and the snowfields accumulating in winters, causing mountainous alpine glaciers to grow, and then spread out of highland areas, making continental glaciers which spread to cover much of Gondwana.
A weird magnetic signal near the State of Florida in North America shows that the peninsula stuck to North America's heel like a piece of old tape about 300 million years ago, when the central and southern Appalachian mountains were built.
At least two major periods of glaciation have been discovered:-
- The first glacial period was associated with the Mississippian Period (359.2–318.1 Ma): ice sheets expanded from a core in southern Africa and South America.
- The second glacial period was associated with the Pennsylvanian Period (318.1–299 Ma); ice sheets expanded from a core in Australia and India.
The extent of glaciation in Antarctica is not exactly known, due to its present ice sheet.
This period is marked by huge forests of primitive plants. It is also the Age of Amphibians and Reptiles. The Carboniferous is the primary period for the development of tetrapods, vertebrates possessing four legs bearing toes. This group includes amphibians, reptiles, birds and mammals.
Some of the early tetrapods include Diplocaulus with its strangely curved head, and the marine Diadectus. It was during this time that the evolution of reptiles and amphibians forked, with the evolutions of both branches evolving separately and differently. There is evidence of intermediate creatures, possessing both reptile and amphibian traits such as the Seymoria.
A major development during this period was the development of egg-laying creatures, in particular, eggs with shells. This development allowed for reproduction outside the marine environment.
The Carboniferous is usually broken into Pennsylvanian (later) and Mississippian (earlier) Epochs. The Faunal stages from youngest to oldest, together with some of their subdivisions, are:
Late Pennsylvanian Gzhelian (most recent)
Late Pennsylvanian Kasimovian
Middle Pennsylvanian Moscovian
Early Pennsylvanian Bashkirian/Morrowan
Late Mississippian Serpukhovian
Middle Mississippian Visean
- Brigantian/St Genevieve/Gasperian/Chesterian
Early Mississippian Tournaisian (oldest)
A global drop in sea level at the end of the Devonian reversed early in the Carboniferous; this created the widespread epicontinental seas and carbonate depostion of the Mississippian. There was also a drop in south polar temperatures; southern Gondwanaland was glaciated throughout the period, though it is uncertain if the ice sheets were a holdover from the Devonian or not. These conditions apparently had little effect in the deep tropics, where lush coal swamps flourished within 30 degrees of the northernmost glaciers.
A mid-Carboniferous drop in sea-level precipitated a major marine extinction, one that hit crinoids and ammonites especially hard. This sea-level drop and the associated unconformity in North America separate the Mississippian period from the Pennsylvanian period.
The Carboniferous was a time of active mountain-building, as the supercontinent Pangea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America-Europe (Laurussia) along the present line of eastern North America. This continental collision resulted in the Hercynian orogeny in Europe, and the Alleghenian orogeny in North America; it also extended the newly-uplifted Appalachians southwestward as the Ouachita Mountains. In the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China (which would collide in the Latest Carboniferous), and South China continents were still separated from Laurasia. The Late Carboniferous Pangaea was shaped like an "O".
There were two major oceans in the Carboniferous - Panthalassa and Paleo-Tethys, which was inside the "O" in the Carboniferous Pangaea. Other minor oceans were shrinking and eventually closed - Rheic Ocean (closed by the assembly of South and North America), the small, shallow Ural Ocean (which was closed by the collision of Baltica and Siberia continents, creating the Ural Mountains) and Proto-Tethys Ocean (closed by North China collision with Siberia/Kazakhstania.
Rocks and coal
Carboniferous rocks in Europe and eastern North America largely consist of a repeated sequence of limestone, sandstone, shale and coal beds, known as "cyclothems" in the U.S. and "coal measures" in Britain. In North America, the early Carboniferous is largely marine limestone, which accounts for the division of the Carboniferous into two periods in North American schemes. The Carboniferous coal beds provided much of the fuel for power generation during the Industrial Revolution and are still of great economic importance.
The large coal deposits of the Carboniferous primarily owe their existence to two factors. The first of these is the appearance of bark-bearing trees (and in particular the evolution of the bark fiber lignin). The second is the lower sea levels that occurred during the Carboniferous as compared to the Devonian period. This allowed for the development of extensive lowland swamps and forests in North America and Europe. Some hypothesize that large quantities of wood were buried during this period because animals and decomposing bacteria had not yet evolved that could effectively digest the new lignin. The extensive burial of biologically-produced carbon led to a buildup of surplus oxygen in the atmosphere; estimates place the peak oxygen content as high as 35%, compared to 21% today. This oxygen level probably increased wildfire activity, as well as resulted in insect and amphibian gigantism--creatures whose size is constrained by respiratory systems that are limited in their ability to diffuse oxygen.
In eastern North America, marine beds are more common in the older part of the period than the later part and are almost entirely absent by the late Carboniferous. More diverse geology existed elsewhere, of course. Marine life is especially rich in crinoids and other echinoderms. Brachiopods were abundant. Trilobites became quite uncommon. On land, large and diverse plant populations existed. Land vertebrates included large amphibians.
300 million year old Eocasea martini was a tiny meat-eating mammal, which lived some 80 million years before the age of dinosaurs. Research on this species helps scientists learn how tiny carnivores transitioned into large herbivores.
In the oceans the most important groups are the foraminifera, corals, bryozoa, brachiopods, ammonoids, echinoderms (especially crinoids), and Chondrichthyes (sharks and their relatives) which are actually vertebrates.
For the first time foraminifera take a prominent part in the marine faunas. The large spindle-shaped genus Fusulina and its relatives were abundant in what is now Russia, China, Japan, North America; other important genera include Valvulina, Endothyra, Archaediscus, and Saccammina (the latter common in Britain and Belgium). Some Carboniferous genera are still extant.
The microscopic shells of Radiolaria are found in cherts of this age in the Culm of Devonshire and Cornwall, and in Russia, Germany and elsewhere.
Sponges are known from spicules and anchor ropes, and include various forms such as the Calcispongea Cotyliscus and Girtycoelia, and the unusual colonial glass sponge Titusvillia.
Both reef-building and solitary corals diversify and flourish; these include both rugose (e.g. Canina, Corwenia, Neozaphrentis), heterocorals, and tabulate (e.g. Chaetetes, Chladochonus, Michelinia) forms.
Conularids were well represented by Conularia
Bryozoa are abundant in some regions; the Fenestellids including Fenestella, Polypora, and the remarkable Archimedes, so named because it is in the shape of an Archimedean screw.
Brachiopods are also abundant; they include Productids, some of which (e.g. Gigantoproductus) reached very large (for brachiopods) size and had very thick shells, while others like Chonetes were more conservative in form. Athyridids, Spiriferids, Rhynchonellids, are Terebratulids are also very common. Inarticulate forms include Discina and Crania. Some species and genera had a very wide distribution with only minor variations.
Annelids such as Spirorbis and Serpulites are common fossils in some horizons.
Among the mollusca, the bivalves continue to increase in numbers and importance. Typical genera include Aviculopecten, Posidonomya, Nucula, Carbonicola, Edmondia, and Modiola
Conocardium is a common rostroconch.
Gastropods are also numerous, including the genera Murchisonia, Euomphalus, Naticopsis.
Nautiloid cephalopods are represented by tightly coiled nautilids, with straight-shelled and curved-shelled forms becoming increasingly rare. Goniatite Ammonoids are common.
Trilobites are rare, represented only by the proetid group. Ostracods such as Cythere, Kirkbya, and Beyrichia are abundant.
Amongst the echinoderms, the crinoids were the most numerous. Dense submarine thickets of long-stemmed crinoids appear to have flourished in shallow seas, and their remains were consolidated into thick beds of rock. Prominent genera include Cyathocrinus, Woodocrinus, and Actinocrinus. Echinoids such as Archaeocidaris and Palaeechinus were also present. The Blastoids, which included the Pentreinitidae and Codasteridae and superficially resembled crinoids in the possession of long stalks attached to the sea-bed, attain their maximum development at this time.
Many fish inhabited the Carboniferous seas; predominantly Elasmobranchs (sharks and their relatives). These included some, like Psammodus, with crushing pavement-like teeth adapted for grinding the shells of brachiopods, crustaceans, and other marine organisms. Other sharks had piercing teeth, such as the Symmoriida; some, the petalodonts, had peculiar cycloid cutting teeth. Most of the sharks were marine, but the Xenacanthida invaded fresh waters of the coal swamps. Among the bony fish, the Palaeonisciformes found in coastal waters also appear to have migrated to rivers. Sarcopterygian fish were also prominent, and one group, the Rhizodonts, reached very large size.
Most species of Carboniferous marine fish have been described largely from teeth, fin spines and dermal ossicles, with smaller freshwater fish preserved whole.
Freshwater fishes were abundant, and include the genera Ctenodus, Uronemus, Acanthodes, Cheirodus, and Gyracanthus.
Ozarcus mapesae, may lead scientists to rethink shark evolution. The fossilized remains of a shark that lived 325 million years ago in what is now Arkansas, complete with a series of cartilage arches that supported its gills and jaws was found. The cartilage arches are quite different from those in modern sharks. This suggests that while their general outward appearance has stayed roughly the same changes have occurred over time that have helped make sharks the perfect eating machines they are today. It is the oldest shark fossil to reveal all of the anatomy of the skeleton supporting the gill arches, a vitally important element of a fish.
A 310 Million Year Old Bandringa Shark Nursery was discovered In Illinois
Early Carboniferous land plants were very similar to those of the preceding Latest Devonian, but new groups also appeared at this time.
The main Early Carboniferous plants were the Equisetales (Horse-tails), Sphenophyllales (vine-like plants), Lycopodiales (Club mosses), Lepidodendrales (scale trees), Filicales (Ferns), Medullosales (previously included in the "seed ferns", an artificial assemblage of a number of early gymnosperm groups) and the Cordaitales. These continued to dominate throughout the period, but during late Carboniferous, several other groups, Cycadophyta (cycads), the Callistophytales (another group of "seed ferns"), and the Voltziales (related to and sometimes included under the conifers), appeared.
The Carboniferous lycophytes of the order Lepidodendrales, which are cousins (but not ancestors) of the tiny club-moss of today, were huge trees with trunks 30 meters high and up to 1.5 meters in diameter. These included Lepidodendron (with its fruit cone called Lepidostrobus), Halonia, Lepidophloios and Sigillaria. The roots of several of these forms are known as Stigmaria.
The fronds of some Carboniferous ferns are almost identical with those of living species. Probably many species were epiphytic. Fossil ferns and "seed ferns" include Pecopteris, Cyclopteris, Neuropteris, Alethopteris, and Sphenopteris; Megaphyton and Caulopteris were tree ferns.
The Equisetales included the common giant form Calamites, with a trunk diameter of 30 to 60 cm and a height of up to 20 meters. Sphenophyllum was a slender climbing plant with whorls of leaves, which was probably related both to the calamites and the lycopods.
Cordaites, a tall plant (6 to over 30 meters) with strap-like leaves, was related to the cycads and conifers; the catkin-like inflorescence, which bore yew-like berries, is called Cardiocarpus. These plants were thought to live in swamps and mangroves. True coniferous trees (Waichia, of the order Voltziales) appear later in the Carboniferous, and preferred higher drier ground..
Freshwater and Lagoonal Invertebrates
Freshwater Carboniferous invertebrates include various bivalve molluscs that lived in brackish or fresh water, such as Anthracomya, Naiadiles, and Carbonicola; diverse Crustacea such as Bairdia, Carbonia, Estheria, Acanthocaris, Dithyrocaris, and Anthrapalaemon.
The Eurypterids were also diverse, and are represented by such genera as Eurypterus, Glyptoscorpius, Anthraconectes, Megarachne (originally misinterpreted as a giant spider) and the specialised very large Hibbertopterus. Many of these were amphibious.
Frequently a temporary return of marine conditions resulted in marine or brackish water genera such as Lingula, Orbiculoidea, and Productus being found in the thin beds known as marine bands.
Fossil remains of air-breathing insects, myriapods and arachnids are known from the late Carboniferous, but so far not from the early Carboniferous. Their diversity when they do appear however show that these arthropods were both well developed and numerous. Their large size can be attributed to the moistness of the environment (mostly swampy fern forests) and the fact that there was a 36% higher oxygen concentration in Earth's atmosphere than today, requiring less effort for respiration and allowing arthropods to grow larger. Among the insect groups are the Syntonopterodea (relatives of present-day mayflies), the abundant and often large sap-sucking Palaeodictyopteroidea, the huge predatory Protodonata (griffinflies), the diverse herbivorous "Protorthoptera", and numerous basal Dictyoptera (ancestors of cockroaches). Many insects have been obtained from the coalfields of Saarbruck and Commentry, and from the hollow trunks of fossil trees in Nova Scotia. Some British coalfields have yielded good specimens: Archaeoptitus, from the Derbyshire coalfield, had a spread of wing extending to more 35 cm; some specimens (Brodia) still exhibit traces of brilliant wing colors. In the Nova Scotian tree trunks land snails (Archaeozonites, Dendropupa) have been found.
Carboniferous amphibians were diverse and common by the middle of the period, more so than they are today; some were as long as 6 meters, and those fully terrestrial as adults had scaly skin. They included a number of basal tetrapod groups classified in early books under the Labyrinthodontia. These had long bodies, a head covered with bony plates and generally weak or undeveloped limbs. The largest were over 2 meters long. They were accompanied by an assemblage of smaller amphibians included under the Lepospondyli, often only about 15 cm long. Some Carboniferous amphibians were aquatic and lived in rivers (Loxomma, Eogyrinus, Proterogyrinus); others may have been semi-aquatic (Ophiderpeton, Amphibamus) or terrestrial (Dendrerpeton, Hyloplesion, Tuditanus, Anthracosaurus).
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 Synapsida (Archaeothyris). These small lizard-like animals quickly gave rise to many descendants. The amniote egg allowed these ancestors of all later birds, mammals, and reptiles to reproduce on land by preventing the desiccation, or drying-out, of the embryo inside. By the end of the Carboniferous period, the reptiles had already diversified into a number of groups, including protorothyridids, captorhinids, aeroscelids, and several families of pelycosaurs.
The emergence of the synapsids was the amniotic tetrapods' divergence into mammals, while the emergence of the sauropsids was the amniotic tetrapods' divergence into reptiles and in turn dinosaurs and birds.
Cryptomartus hindi and Eophrynus prestvicii, closely related to modern-day spiders used their front legs to grapple with prey.
305 Million Years Ago, an "almost spider" may show an evolutionary stage in spider development. Idmonarachne brasieri after the Greek mythological figure Idmon, father of Arachne, a weaver turned into a spider by a jealous goddess, the "almost spider" lacks only the spinnerets that spiders use to turn silk into webs.
Because plants and animals were growing in size, and abundance in this time (ie. Lepidodendron) land fungi diversified further. Marine fungi still occupied the oceans.
- The Columbia History of the World, Harper & Row, 1972