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, to the beginning of the Permian Period, 298.9 Mya. The name Carboniferous means "coal-bearing" and derives from the Latin words carbō and ferō, was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the modern'system' names to be employed, reflects the fact that many coal beds were formed globally during that time; the Carboniferous is treated in North America as two geological periods, the earlier Mississippian and the Pennsylvanian. Terrestrial animal life was well established by the Carboniferous period. Amphibians were the dominant land vertebrates, of which one branch would evolve into amniotes, the first terrestrial vertebrates. Arthropods were very common, many were much larger than those of today. Vast swaths of forest covered the land, which would be laid down and become the coal beds characteristic of the Carboniferous stratigraphy evident today.
The atmospheric content of oxygen reached its highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. The half of the period experienced glaciations, low sea level, mountain building as the continents collided to form Pangaea. A minor marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred at the end of the period, caused by climate change. In the United States the Carboniferous is broken into Mississippian and Pennsylvanian subperiods; the Mississippian is about twice as long as the Pennsylvanian, but due to the large thickness of coal-bearing deposits with Pennsylvanian ages in Europe and North America, the two subperiods were long thought to have been more or less equal in duration. In Europe the Lower Carboniferous sub-system is known as the Dinantian, comprising the Tournaisian and Visean Series, dated at 362.5-332.9 Ma, the Upper Carboniferous sub-system is known as the Silesian, comprising the Namurian and Stephanian Series, dated at 332.9-298.9 Ma.
The Silesian is contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, the Westphalian as the Coal Measures and Pennant Sandstone; the International Commission on Stratigraphy faunal stages from youngest to oldest, together with some of their regional subdivisions, are: A global drop in sea level at the end of the Devonian reversed early in the Carboniferous. There was a drop in south polar temperatures; these conditions had little effect in the deep tropics, where lush swamps to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major marine extinction, one that hit crinoids and ammonites hard; this sea level drop and the associated unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation.
The Carboniferous was a time of active mountain-building as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America; this continental collision resulted in the Hercynian orogeny in Europe, the Alleghenian orogeny in North America. 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, 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, inside the "O" in the Carboniferous Pangaea. Other minor oceans were shrinking and closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean. Average global temperatures in the Early Carboniferous Period were high: 20 °C.
However, cooling during the Middle Carboniferous reduced average global temperatures to about 12 °C. Lack of growth rings of fossilized trees suggest a lack of seasons of a tropical climate. Glaciations in Gondwana, triggered by Gondwana's southward movement, continued into the Permian and because of the lack of clear markers and breaks, the deposits of this glacial period are referred to as Permo-Carboniferous in age; the cooling and drying of the climate led to the Carboniferous Rainforest Collapse during the late Carboniferous. Tropical rainforests fragmented and were devastated by climate change. Carboniferous rocks in Europe and eastern North America consist of a repeated sequence of limestone, sandstone and coal beds. In North America, the early Carboniferous is marine
Neosodon was a genus of sauropod dinosaur from the Late Tithonian-age Upper Jurassic Sables et Gres a Trigonia gibbosa of Départment du Pas-de-Calais, France. It has never been formally given a species name, but is seen as N. praecursor, which comes from a different animal. In the past, it had been assigned to the wastebasket taxon Pelorosaurus, but restudy has suggested that it could be related to Turiasaurus, a roughly-contemporaneous giant Spanish sauropod. Moussaye named this genus for a large, worn tooth found in Wilmille, near Boulogne-sur-Mer, neglected to give it a species name, he thought. Sauvage synonymized it with his tooth species Iguanodon praecursor, which by this time had become mixed up with Edward Drinker Cope's contemporaneous American Morrison Formation genus Caulodon. However, the two are not based on the same type, as "I". Praecursor comes from older rocks: the same unnamed Kimmeridgian formation as Morinosaurus. Earlier reviews accepted it as a synonym of Pelorosaurus, considered it a possible brachiosaurid.
In the 1990s, French researchers published on new camarasaurid bones from the same formation. At first and Martin suggested that they belonged to Neosodon praecursor, but Le Loeuff et al. rejected this, as Neosodon is based only on a tooth, which did not overlap the new material. The latest review accepted both Neosodon and "Iguanodon" praecursor as dubious sauropods. However, Royo-Torres et al. in their description of Turiasaurus, noted that this tooth was similar to those of their genus and suggested that it could be a turiasaur. The tooth is spear-like or spatulate in shape; the owner would have been a quadrupedal herbivore. Dinosaurs of France Paleobiology Database entry.
Cladistics is an approach to biological classification in which organisms are categorized in groups based on the most recent common ancestor. Hypothesized relationships are based on shared derived characteristics that can be traced to the most recent common ancestor and are not present in more distant groups and ancestors. A key feature of a clade is that all its descendants are part of the clade. All descendants stay in their overarching ancestral clade. For example, if within a strict cladistic framework the terms animals, bilateria/worms, fishes/vertebrata, or monkeys/anthropoidea were used, these terms would include humans. Many of these terms are used paraphyletically, outside of cladistics, e.g. as a'grade'. Radiation results in the generation of new subclades by bifurcation; the techniques and nomenclature of cladistics have been applied to other disciplines. Cladistics is now the most used method to classify organisms; the original methods used in cladistic analysis and the school of taxonomy derived from the work of the German entomologist Willi Hennig, who referred to it as phylogenetic systematics.
Cladistics in the original sense refers to a particular set of methods used in phylogenetic analysis, although it is now sometimes used to refer to the whole field. What is now called the cladistic method appeared as early as 1901 with a work by Peter Chalmers Mitchell for birds and subsequently by Robert John Tillyard in 1921, W. Zimmermann in 1943; the term "clade" was introduced in 1958 by Julian Huxley after having been coined by Lucien Cuénot in 1940, "cladogenesis" in 1958, "cladistic" by Cain and Harrison in 1960, "cladist" by Mayr in 1965, "cladistics" in 1966. Hennig referred to his own approach as "phylogenetic systematics". From the time of his original formulation until the end of the 1970s, cladistics competed as an analytical and philosophical approach to systematics with phenetics and so-called evolutionary taxonomy. Phenetics was championed at this time by the numerical taxonomists Peter Sneath and Robert Sokal, evolutionary taxonomy by Ernst Mayr. Conceived, if only in essence, by Willi Hennig in a book published in 1950, cladistics did not flourish until its translation into English in 1966.
Today, cladistics is the most popular method for constructing phylogenies from morphological data. In the 1990s, the development of effective polymerase chain reaction techniques allowed the application of cladistic methods to biochemical and molecular genetic traits of organisms, vastly expanding the amount of data available for phylogenetics. At the same time, cladistics became popular in evolutionary biology, because computers made it possible to process large quantities of data about organisms and their characteristics; the cladistic method interprets each character state transformation implied by the distribution of shared character states among taxa as a potential piece of evidence for grouping. The outcome of a cladistic analysis is a cladogram – a tree-shaped diagram, interpreted to represent the best hypothesis of phylogenetic relationships. Although traditionally such cladograms were generated on the basis of morphological characters and calculated by hand, genetic sequencing data and computational phylogenetics are now used in phylogenetic analyses, the parsimony criterion has been abandoned by many phylogeneticists in favor of more "sophisticated" but less parsimonious evolutionary models of character state transformation.
Cladists contend. Every cladogram is based on a particular dataset analyzed with a particular method. Datasets are tables consisting of molecular, ethological and/or other characters and a list of operational taxonomic units, which may be genes, populations, species, or larger taxa that are presumed to be monophyletic and therefore to form, all together, one large clade. Different datasets and different methods, not to mention violations of the mentioned assumptions result in different cladograms. Only scientific investigation can show, more to be correct; until for example, cladograms like the following have been accepted as accurate representations of the ancestral relations among turtles, lizards and birds: If this phylogenetic hypothesis is correct the last common ancestor of turtles and birds, at the branch near the ▼ lived earlier than the last common ancestor of lizards and birds, near the ♦. Most molecular evidence, produces cladograms more like this: If this is accurate the last common ancestor of turtles and birds lived than the last common ancestor of lizards and birds.
Since the cladograms provide competing accounts of real events, at most one of them is correct. The cladogram to the right represents the current universally accepted hypothesis that all primates, including strepsirrhines like the lemurs and lorises, had a common ancestor all of whose descendants were primates, so form a clade. Within the primates, all anthropoids are hypothesized to have had a common ancestor all of whose descendants were anthropoids, so they form the clade called Anthropoidea; the "prosimians", on the other hand, form a paraphyletic taxon. The name Prosimii is not used in phylogenetic nomenclature, whic
Diplodocids, or members of the family Diplodocidae, are a group of sauropod dinosaurs. The family includes some of the longest creatures to walk the Earth, including Diplodocus and Supersaurus, some of which may have reached lengths of up to 34 metres. While the diplodocids were massive sauropods, they were slender when compared to the titanosaurs and brachiosaurids, although they were extremely long, they had short legs, making them the "dachshund" of giant dinosaurs, their rear legs were longer than front legs, giving their back a distinctive downward slope towards the neck. Their necks were extremely long. According to recent computer simulations, they may not have been able to lift their necks like other sauropods. However, these simulations do not take vertebral cartilage into account, which would allow a greater range of motion. Instead of reaching up into trees, they may have used their necks to graze over a broad area, they may have used their necks to reach into dense stands of conifers, or over marshy ground.
Their heads, like those of other sauropods, were tiny with the nasal openings on the top of the head. The heads of diplodocids have been depicted with the nostrils on top due to the position of the nasal openings at the apex of the skull. There has been speculation over whether such a configuration meant that diplodocids may have had a trunk. A 2006 study surmised, it noted that the facial nerve in an animal with a trunk, such as an elephant, is large as it innervates the trunk. The evidence suggests that the facial nerve is small in diplodocids. Studies by Lawrence Witmer indicated that, while the nasal openings were high on the head, the actual, fleshy nostrils were situated much lower down on the snout. Diplodocids had long, whip-like tails, which were thick at the base and tapered off to be thin at the end. Computer simulations have shown that the diplodocids could have snapped their tails, like a bullwhip; this could generate a sonic boom in excess of 200 decibels, may have been used in mating displays, or to drive off predators.
There is some circumstantial evidence supporting this as well: a number of diplodocids have been found with fused or damaged tail vertebrae, which may be a symptom of cracking their tails. Their teeth were only present in the front of the mouth, looked like pencils or pegs, they used their teeth to crop off food, without chewing, relied on gastroliths to break down tough plant fibers. Diplodocines have unusual teeth compared to other sauropods; the crowns are long and slender, elliptical in cross-section, while the apex forms a blunt, triangular point. The most prominent wear facet is on the apex, though unlike all other wear patterns observed within sauropods, diplodocine wear patterns are on the labial side of both the upper and lower teeth; this implies that the feeding mechanism of Diplodocus and other diplodocids was radically different from that of other sauropods. Unilateral branch stripping is the most feeding behavior of Diplodocus, as it explains the unusual wear patterns of the teeth.
In unilateral branch stripping, one tooth row would have been used to strip foliage from the stem, while the other would act as a guide and stabilizer. With the elongated preorbital region of the skull, longer portions of stems could be stripped in a single action; the palinal motion of the lower jaws could have contributed two significant roles to feeding behaviour: 1) an increased gape, 2) allowed fine adjustments of the relative positions of the tooth rows, creating a smooth stripping action. Young et al. used biomechanical modelling to examine the performance of the diplodocine skull. It was concluded that the proposal that its dentition was used for bark-stripping was not supported by the data, which showed that under that scenario, the skull and teeth would undergo extreme stresses; the hypotheses of branch-stripping and/or precision biting were both shown to be biomechanically plausible feeding behaviors. Diplodocine teeth were continually replaced throughout their lives in less than 35 days, as was discovered by Michael D'Emic et al.
Within each tooth socket, as many as five replacement teeth were developing to replace the next one. Studies of the teeth reveal that it preferred different vegetation from the other sauropods of the Morrison, such as Camarasaurus; this may have better allowed the various species of sauropods to exist without competition. Few skin impressions of diplodocids have been found. However, at least one significant find was reported by Stephen Czerkas in 1992. Fossils from the Howe Quarry in Shell, Wyoming preserved portions of the skin from around the tip of the tail, or "whiplash". Czerkas noted that the skin preserved a sequence of conical spines, that other, larger spines were found scattered around larger tail vertebrae; the spines appeared to be oriented in a single row along the mid-line of the tail, Czerkas speculated that this midline row may have continued over the animal's entire back and neck. Long-bone histology enables researchers to estimate the age. A study by Griebeler et al. examined long bone histological data and concluded that the diplodocid MfN.
R.2625 weighed 4,753 kilograms, reached sexual maturity at 23 years and died at age 24. The same growth model indicated that the diplodocid MfN. R. NW4 weighed 18,463 kilograms, died at age 23, before reaching sexual maturity. Diplodocidae was
The Precambrian is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic eon, named after Cambria, the Latinised name for Wales, where rocks from this age were first studied; the Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons of the geologic time scale, it spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 541 million years ago, when hard-shelled creatures first appeared in abundance. Little is known about the Precambrian, despite it making up seven-eighths of the Earth's history, what is known has been discovered from the 1960s onwards; the Precambrian fossil record is poorer than that of the succeeding Phanerozoic, fossils from the Precambrian are of limited biostratigraphic use. This is because many Precambrian rocks have been metamorphosed, obscuring their origins, while others have been destroyed by erosion, or remain buried beneath Phanerozoic strata.
It is thought that the Earth coalesced from material in orbit around the Sun at 4,543 Ma, may have been struck by a large planetesimal shortly after it formed, splitting off material that formed the Moon. A stable crust was in place by 4,433 Ma, since zircon crystals from Western Australia have been dated at 4,404 ± 8 Ma; the term "Precambrian" is recognized by the International Commission on Stratigraphy as the only "supereon" in geologic time. "Precambrian" is still used by geologists and paleontologists for general discussions not requiring the more specific eon names. As of 2010, the United States Geological Survey considers the term informal, lacking a stratigraphic rank. A specific date for the origin of life has not been determined. Carbon found in 3.8 billion-year-old rocks from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have been found in Western Australia. Probable fossils 100 million years older have been found in the same area.
However, there is evidence. There is a solid record of bacterial life throughout the remainder of the Precambrian. Excluding a few contested reports of much older forms from North America and India, the first complex multicellular life forms seem to have appeared at 1500 Ma, in the Mesoproterozoic era of the Proterozoic eon. Fossil evidence from the Ediacaran period of such complex life comes from the Lantian formation, at least 580 million years ago. A diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma; these are referred to as Vendian biota. Hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic eon. By the middle of the following Cambrian period, a diverse fauna is recorded in the Burgess Shale, including some which may represent stem groups of modern taxa; the increase in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life. While land seems to have been devoid of plants and animals and other microbes formed prokaryotic mats that covered terrestrial areas.
Tracks from an animal with leg like appendages have been found in what was mud 551 million years ago. Evidence of the details of plate motions and other tectonic activity in the Precambrian has been poorly preserved, it is believed that small proto-continents existed prior to 4280 Ma, that most of the Earth's landmasses collected into a single supercontinent around 1130 Ma. The supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch 2400–2100 Ma. One of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a "Snowball Earth"; the atmosphere of the early Earth is not well understood. Most geologists believe it was composed of nitrogen, carbon dioxide, other inert gases, was lacking in free oxygen. There is, evidence that an oxygen-rich atmosphere existed since the early Archean. At present, it is still believed that molecular oxygen was not a significant fraction of Earth's atmosphere until after photosynthetic life forms evolved and began to produce it in large quantities as a byproduct of their metabolism.
This radical shift from a chemically inert to an oxidizing atmosphere caused an ecological crisis, sometimes called the oxygen catastrophe. At first, oxygen would have combined with other elements in Earth's crust iron, removing it from the atmosphere. After the supply of oxidizable surfaces ran out, oxygen would have begun to accumulate in the atmosphere, the modern high-oxygen atmosphere would have developed. Evidence for this lies in older rocks that contain massive banded iron formations that were laid down as iron oxides. A terminology has evolved covering the early years of the Earth's existence, as radiometric dating has allowed real dates to be assigned to specific formations and features; the Precambrian is divided into
Zby is an extinct genus of turiasaurian sauropod dinosaur known from the Late Jurassic of the Lourinhã Formation, central west Portugal. It contains a single species, Zby atlanticus, it is named after Georges Zbyszewski, who studied the paleontology of Portugal. Zby was first described and named by Octávio Mateus, Philip D. Mannion and Paul Upchurch in 2014 and the type species is Zby atlanticus, although it was thought to be Turiasaurus riodevensis, it is known from its holotype, a associated partial skeleton including a complete tooth with root, a fragment of cervical neural arch, an anterior chevron, an complete right pectoral girdle and forelimb. Zby is differentiated from other sauropods based on four autapomorphies, including a prominent posteriorly projecting ridge on the humerus at the level of the deltopectoral crest. Zby is suggested to be related to Turiasaurus riodevensis from Spain and Portugal, based on its tooth morphology, extreme anteroposterior compression of the proximal end of the radius, strong beveling of the lateral half of the distal end of the radius, while some other forelimb traits distinguish these two genera.
Nearly all other anatomical features suggest that Zby is a non-neosauropod eusauropod, confirming its position as a Turiasaurian. Zby is estimated to be between 16 and 18 metres long
Atlasaurus is a genus of sauropod dinosaurs from Middle Jurassic beds in North Africa. Atlasaurus differs from Brachiosaurus relative to the estimated length of the dorsal vertebral column, in having a proportionately larger skull, a shorter neck, a longer tail and more elongated limbs; the teeth have denticles. The lower jaw of Atlasaurus is about 69 centimetres long, the neck was about 3.86 metres long, the humerus 1.95 metres long, the femur about 2 metres long. It has been estimated at 15 metres in length, 22.5 tonnes in weight. Atlasaurus was discovered by Monbaron, Russell & Taquet in 1999, it was named after the location of discovery in the High Atlas range of the Atlas Mountains of Morocco, for the animal's size. It is known from a nearly complete skeleton with a skull found at Wawmda, in the Middle Jurassic Tiougguit Formation in Morocco's Azilal Province; the type species is Atlasaurus imelakei, the specific name coming from Arabic Imelake, the name of a giant. A primitive sauropod identified as a "cetiosaur" when first discovered in 1981, Atlasaurus appears to be closer to Brachiosaurus than to any other known sauropod based on detailed similarities between the vertebral column and limbs.
However, more recent analyses have considered it to be a putative member of the Turiasauria