Selected articles about prehistoric North America

1

Acrocanthosaurus (/ˌækroʊˌkænθoʊˈsɔːrəs/ ak-rə-KAN-thə-SOR-əs; meaning "high-spined lizard") is a genus of theropod dinosaur that existed in what is now North America during the Aptian and early Albian stages of the Early Cretaceous. Like most dinosaur genera, Acrocanthosaurus contains only a single species, A. atokensis. Its fossil remains are found mainly in the U.S. states of Oklahoma, Texas, and Wyoming, although teeth attributed to Acrocanthosaurus have been found as far east as Maryland.

Acrocanthosaurus was a bipedal predator. As the name suggests, it is best known for the high neural spines on many of its vertebrae, which most likely supported a ridge of muscle over the animal's neck, back and hips. Acrocanthosaurus was one of the largest theropods, approaching 12 meters (40 ft) in length, and weighing up to 6.2 tonnes (6.8 short tons). Large theropod footprints discovered in Texas may have been made by Acrocanthosaurus, although there is no direct association with skeletal remains.

Recent discoveries have elucidated many details of its anatomy, allowing for specialized studies focusing on its brain structure and forelimb function. Acrocanthosaurus was the largest theropod in its ecosystem and likely an apex predator which possibly preyed on large sauropods and ornithopods. (see more...)

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Albertosaurus (/ælˌbɜːrtoʊˈsɔːrəs/; meaning "Alberta lizard") is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, about 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which the genus is named. Scientists disagree on the content of the genus, with some recognizing Gorgosaurus libratus as a second species.

As a tyrannosaurid, Albertosaurus was a bipedal predator with tiny, two-fingered hands and a massive head with dozens of large, sharp teeth. It may have been at the top of the food chain in its local ecosystem. Although relatively large for a theropod, Albertosaurus was much smaller than its more famous relative Tyrannosaurus, probably weighing less than 2 metric tons.

Since the first discovery in 1884, fossils of more than thirty individuals have been recovered, providing scientists with a more detailed knowledge of Albertosaurus anatomy than is available for most other tyrannosaurids. The discovery of 26 individuals at one site provides evidence of pack behaviour and allows studies of ontogeny and population biology which are impossible with lesser-known dinosaurs. (see more...)

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Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period (Kimmeridgian to early Tithonian). The name "Allosaurus" means "different lizard". The first fossil remains that can definitely be ascribed to this genus were described in 1877 by paleontologist Othniel Charles Marsh. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles.

Allosaurus was a large bipedal predator. Its skull was large and equipped with dozens of large, sharp teeth. It averaged 8.5 m (28 ft) in length, though fragmentary remains suggest it could have reached over 12 m (39 ft). It is classified as an allosaurid, a type of carnosaurian theropod dinosaur. The genus has a complicated taxonomy, and includes an uncertain number of valid species, the best known of which is A. fragilis. The bulk of Allosaurus remains have come from North America's Morrison Formation, with material also known from Portugal and possibly Tanzania.

As the most abundant large predator in the Morrison Formation, Allosaurus was at the top of the food chain, probably preying on contemporaneous large herbivorous dinosaurs and perhaps even other predators. Potential prey included ornithopods, stegosaurids, and sauropods. Some paleontologists interpret Allosaurus as having had cooperative social behavior, and hunting in packs, while others believe individuals may have been aggressive toward each other. It may have attacked large prey by ambush, using its upper jaw like a hatchet. (see more...)

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The Chicxulub crater (/ˈtʃiːkʃəluːb/; Mayan pronunciation: [tʃʼikʃuluɓ]) is a prehistoric impact crater buried underneath the Yucatán Peninsula in Mexico. Its center is located near the town of Chicxulub, after which the crater is named. The age of the Chicxulub asteroid impact and the Cretaceous–Paleogene boundary (K–Pg boundary) coincide precisely. The crater is more than 180 kilometres (110 mi) in diameter and 20 km (12 mi) in depth, making the feature one of the largest confirmed impact structures on Earth; the impacting bolide that formed the crater was at least 10 km (6 mi) in diameter. Evidence for the impact origin of the crater includes shocked quartz, a gravity anomaly, and tektites in surrounding areas. The age of the rocks marked by the impact shows that this impact structure dates from roughly 66 million years ago, the end of the Cretaceous period, and the start of the Paleogene period. The impact associated with the crater is thus implicated in the Cretaceous–Paleogene extinction event, including the worldwide extinction of non-avian dinosaurs. This conclusion has been the source of controversy. In March 2010, 41 experts from many countries reviewed the available evidence: 20 years worth of data spanning a variety of fields. They concluded that the impact at Chicxulub triggered the mass extinctions at the K–Pg boundary. (see more...)

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The Columbian mammoth (Mammuthus columbi) was a species of mammoth that inhabited North America as far north as the northern United States and as far south as Costa Rica during the Pleistocene epoch. The Columbian mammoth evolved from the steppe mammoth, which entered North America from Asia about 1.5 million years ago. The closest extant relative of the Columbian and other mammoths is the Asian elephant.

Reaching 4 m (13 ft) at the shoulders and 8–10 tonnes (18,000–22,000 lb) in weight, the Columbian mammoth was one of the largest species of mammoth. It had long, curved tusks and four molars, which were replaced six times during the lifetime of an individual. It most likely used its tusks and trunk like modern elephants—for manipulating objects, fighting, and foraging. Bones, hair, dung and stomach contents have been discovered, but no preserved carcasses are known. The Columbian mammoth preferred open areas, such as parkland landscapes, and fed on sedge, grass, and other plants.

Columbian mammoths coexisted with Palaeoamericans, who hunted them for food, used their bones for making tools, and depicted them in ancient art. Columbian mammoth remains have been found in association with Clovis culture artefacts. The Columbian mammoth disappeared at the end of the Pleistocene around 11,000 years ago, most likely as a result of habitat loss caused by climate change, hunting by humans, or a combination of both. (see more...)

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Daspletosaurus (/dæsˌpliːtoʊˈsɔːrəs/ das-PLEET-o-SAWR-əs; meaning "frightful lizard") is a genus of tyrannosaurid theropod dinosaur that lived in western North America between 77 and 74 million years ago, during the Late Cretaceous Period. Fossils of the only named species (D. torosus) were found in Alberta, although other possible species from Alberta and Montana await description. Including these undescribed species makes Daspletosaurus the most species-rich genus of tyrannosaur.

Daspletosaurus is closely related to the much larger and more recent Tyrannosaurus. Like most known tyrannosaurids, it was a multi-tonne bipedal predator equipped with dozens of large, sharp teeth. Daspletosaurus had the small forelimbs typical of tyrannosaurids, although they were proportionately longer than in other genera.

As an apex predator, Daspletosaurus was at the top of the food chain, probably preying on large dinosaurs like the ceratopsid Centrosaurus and the hadrosaur Hypacrosaurus. In some areas, Daspletosaurus coexisted with another tyrannosaurid, Gorgosaurus, though there is some evidence of niche differentiation between the two. While Daspletosaurus fossils are rarer than other tyrannosaurids, the available specimens allow some analysis of the biology of these animals, including social behavior, diet, and life history. (see more...)

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Deinonychus is a genus of carnivorous dromaeosaurid coelurosaurian dinosaurs. There is one described species, Deinonychus antirrhopus. This species, which could grow up to 3.4 metres (11 ft) long, lived during the early Cretaceous Period, about 115–108 million years ago (from the mid-Aptian to early Albian stages). Fossils have been recovered from the U.S. states of Montana, Wyoming, and Oklahoma, in rocks of the Cloverly Formation and Antlers Formation, though teeth that may belong to Deinonychus have been found much farther east in Maryland.

Paleontologist John Ostrom's study of Deinonychus in the late 1960s revolutionized the way scientists thought about dinosaurs, leading to the "dinosaur renaissance" and igniting the debate on whether dinosaurs were warm-blooded or cold blooded. Before this, the popular conception of dinosaurs had been one of plodding, reptilian giants. Ostrom noted the small body, sleek, horizontal posture, ratite-like spine, and especially the enlarged raptorial claws on the feet, which suggested an active, agile predator. The etymology "terrible claw" refers to the unusually large, sickle-shaped talon on the second toe of each hind foot. The fossil YPM 5205 preserves a large, strongly curved ungual. Ostrom looked at crocodile and bird claws and reconstructed the claw for YPM 5205 as over 150 millimetres (5.9 in) long.

In both the Cloverly and Antlers formations, Deinonychus remains have been found closely associated with those of the ornithopod Tenontosaurus. Teeth discovered associated with Tenontosaurus specimens imply they were hunted, or at least scavenged upon, by Deinonychus. (see more...)

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Deinosuchus is an extinct genus related to the alligator that lived 80 to 73 million years ago (Ma), during the late Cretaceous period. The name translates as "terrible crocodile" and is derived from the Greek. Although Deinosuchus was far larger than any modern crocodile or alligator, with the largest adults measuring 10.6 m (35 ft) in total length, its overall appearance was fairly similar to its smaller relatives. It had large, robust teeth built for crushing, and its back was covered with thick hemispherical osteoderms. One study indicated Deinosuchus may have lived for up to 50 years, growing at a rate similar to that of modern crocodilians, but maintaining this growth over a much longer time. Deinosuchus fossils have been found in 10 US states, including Texas, Montana, and many along the East Coast. Fossils have also been found in northern Mexico. It lived on both sides of the Western Interior Seaway, and was an opportunistic apex predator in the coastal regions of eastern North America. Deinosuchus reached its largest size in its western habitat, but the eastern populations were far more abundant. Deinosuchus was probably capable of killing and eating large dinosaurs. It may have also fed upon sea turtles, fish, and other aquatic and terrestrial prey. (see more...)

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The Cretaceous–Paleogene extinction event was the mass extinction of three-quarters of Earth's plant and animal species during a geologically brief interval about 66 million years (Ma) ago. A wide range of species perished in the K–Pg extinction, most notably the non-avian dinosaurs. However, other groups that sustained losses or vanished include mammals, pterosaurs, birds, lizards, insects, and plants. In the oceans, the K–Pg extinction devastated the giant marine lizards, plesiosaurs, fishes, ammonites and plankton. It marked the end of the Cretaceous period and with it, the entire Mesozoic Era, opening the Cenozoic Era which continues today. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows high levels of the metal iridium, which is rare in the Earth's crust but abundant in asteroids. It is now generally believed that the K–Pg extinction was triggered by a massive comet/asteroid impact and its catastrophic effects on the global environment, including a lingering impact winter that halted photosynthesis in plants and plankton. However, some scientists maintain the extinction was caused or exacerbated by other factors, such as volcanic eruptions, climate change, and/or sea level change. Whatever the cause, many of the surviving animal groups diversified during the ensuing Paleogene period. Mammals in particular radiated into new forms such as horses, whales, bats, and primates. (see more...)

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Dinosaurs are a diverse group of animals that first appeared during the Triassic period, 231.4 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the beginning of the Jurassic until the end of the Cretaceous (66 million years ago), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups. The fossil record indicates that birds evolved from theropod dinosaurs and, consequently, they are considered a subgroup of dinosaurs by many paleontologists. Some birds survived the extinction event and their descendants continue the dinosaur lineage to the present day. Using fossil evidence, paleontologists have identified over 500 distinct genera of non-avian dinosaurs. Dinosaurs are represented on every continent. Some are herbivorous, others carnivorous. While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species. Elaborate display structures such as horns or crests are common to all dinosaur groups, and some extinct groups developed skeletal modifications such as bony armor and spines. Evidence suggests that egg laying and nest building are additional traits shared by all dinosaurs. While modern birds are generally small due to the constraints of flight, many prehistoric dinosaurs were large-bodied—the largest sauropod dinosaurs may have achieved lengths of 58 meters (190 feet). Many dinosaurs were quite small: Xixianykus, for example, was only about 50 cm (20 in) long. (see more...)

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Diplodocus is an extinct genus of diplodocid sauropod dinosaur whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a Neo-Latin term derived from Greek διπλός (diplos) "double" and δοκός (dokos) "beam", in reference to its double-beamed chevron bones located in the underside of the tail. These bones were initially believed to be unique to Diplodocus; however, they have since then been discovered in other members of the diplodocid family and in non-diplodocid sauropods such as Mamenchisaurus.

This genus of dinosaurs lived in what is now western North America at the end of the Jurassic Period. Diplodocus is one of the more common dinosaur fossils found in the Upper Morrison Formation, a sequence of shallow marine and alluvial sediments deposited about 155 to 148 million years ago, in what is now termed the Kimmeridgian and Tithonian stages (Diplodocus itself ranged from about 154 to 150 million years ago). The Morrison Formation records an environment and time dominated by gigantic sauropod dinosaurs such as Camarasaurus, Barosaurus, Apatosaurus and Brachiosaurus.

Diplodocus is among the most easily identifiable dinosaurs, with its classic dinosaur shape, long neck and tail and four sturdy legs. For many years, it was the longest dinosaur known. Its great size may have been a deterrent to the predators Allosaurus and Ceratosaurus: their remains have been found in the same strata, which suggests they coexisted with Diplodocus. (see more...)

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The Ediacara biota consisted of enigmatic tubular and frond-shaped, mostly sessile organisms that lived during the Ediacaran Period (ca. 635–542 Ma). Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The Ediacara biota radiated in an event called the Avalon explosion, 575 million years ago, after the Earth had thawed from the Cryogenian period's extensive glaciation. The biota largely disappeared contemporaneously with the rapid increase in biodiversity known as the Cambrian explosion. Most of the currently existing body plans of animals first appeared in the fossil record of the Cambrian rather than the Ediacaran. For macroorganisms, the Cambrian biota appears to have completely replaced the organisms that populated the Ediacaran fossil record, although relationships are still a matter of debate. Multiple hypotheses exist to explain the disappearance of this biota, including preservation bias, a changing environment, the advent of predators and competition from other life-forms. Breandán MacGabhann argues that the concept of "Ediacara Biota" is artificial and arbitrary as it can not be defined geographically, stratigraphically, taphonomically nor biologically. He points out that 8 particular fossils or groups of fossils considered "Ediacaran" have 5 taphonomic modes (preservation styles), occur in 3 geological periods, and have no phylogenetic meaning as a whole. (see more...)

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Edmontosaurus is a genus of crestless duck-billed dinosaur. The fossils of this animal have been found in rocks of western North America that date from the late Campanian stage to the end of the Maastrichtian stage of the Cretaceous Period, between 73 and 65.5 million years ago. It was one of the last non-avian dinosaurs, and lived shortly before the Cretaceous–Paleogene extinction event. Edmontosaurus was one of the largest hadrosaurids, measuring up to 13 meters (43 ft) long and weighing around 4.0 metric tons (4.4 short tons). It is known from several well-preserved specimens that include not only bones, but in some cases extensive skin impressions and possible gut contents.

Edmontosaurus has a lengthy and complicated taxonomic history dating to the late 19th century. The type species, E. regalis, was named by Lawrence Lambe in 1917, although several other species that are now classified in Edmontosaurus were named earlier. The best known of these is E. annectens, originally named by Othniel Charles Marsh in 1892.

Edmontosaurus was widely distributed across western North America. The distribution of Edmontosaurus fossils suggests that it preferred coasts and coastal plains. It was an herbivore that could move on both two legs and four. Because it is known from several bone beds, Edmontosaurus is thought to have lived in groups, and may have been migratory as well.

(see more...)

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Gorgosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, between about 76.6 and 75.1 million years ago. Fossil remains have been found in the Canadian province of Alberta and possibly the U.S. state of Montana. Paleontologists recognize only the type species, G. libratus, although other species have been erroneously referred to the genus.

Like most known tyrannosaurids, Gorgosaurus was a bipedal predator weighing more than two metric tons as an adult; dozens of large, sharp teeth lined its jaws, while its two-fingered forelimbs were comparatively small. Gorgosaurus was most closely related to Albertosaurus, and more distantly related to the larger Tyrannosaurus. Some experts consider G. libratus to be a species of Albertosaurus; this would make Gorgosaurus a junior synonym of that genus.

Gorgosaurus lived in a lush floodplain environment along the edge of an inland sea. It was an apex predator (meaning that it was at the top of its food chain), preying upon abundant ceratopsids and hadrosaurs. In some areas, Gorgosaurus coexisted with another tyrannosaurid, Daspletosaurus. Although these animals were roughly the same size, there is some evidence of niche differentiation between the two. Gorgosaurus is the best-represented tyrannosaurid in the fossil record, known from dozens of specimens. These plentiful remains have allowed scientists to investigate its ontogeny, life history and other aspects of its biology. (see more...)

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Lambeosaurus (/ˌlæmbi.oʊˈsɔːrəs/ LAM-bee-ə-SOR-əs; meaning "Lambe's lizard") is a genus of hadrosaurid dinosaur that lived about 76 to 75 million years ago, in the Late Cretaceous period (Campanian) of North America. This bipedal/quadrupedal, herbivorous dinosaur is known for its distinctive hollow cranial crest, which in the best-known species resembled a hatchet. Several possible species have been named, from Canada, the United States, and Mexico, but only the two Canadian species are currently recognized as valid. Lambeosaurus was belatedly described in 1923 by William Parks, over twenty years after the first material was studied by Lawrence Lambe. The genus has had a complicated taxonomic history, in part because small-bodied crested hadrosaurids now recognized as juveniles were once thought to belong to their own genera and species. Currently, the various skulls assigned to the type species L. lambei are interpreted as showing age differences and sexual dimorphism. Lambeosaurus was closely related to the better known Corythosaurus, which is found in slightly older rocks, as well as the less well-known genera Hypacrosaurus and Olorotitan. All had unusual crests, which are now generally assumed to have served social functions like noisemaking and recognition. (see more...)

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Parasaurolophus (/ˌpærəsɔːˈrɒləfəs, -ˌsɔːrəˈloʊfəs/; meaning "near crested lizard" in reference to Saurolophus) is a genus of ornithopod dinosaur that lived in what is now North America during the Late Cretaceous Period, about 76.5–73 million years ago. It was a herbivore that walked both as a biped and a quadruped. Three species are recognized: P. walkeri (the type species), P. tubicen, and the short-crested P. cyrtocristatus. Remains are known from Alberta (Canada), and New Mexico and Utah (United States). The genus was first described in 1922 by William Parks from a skull and partial skeleton found in Alberta. Parasaurolophus was a hadrosaurid, part of a diverse family of Cretaceous dinosaurs known for their range of bizarre head adornments. This genus is known for its large, elaborate cranial crest, which at its largest forms a long curved tube projecting upwards and back from the skull. Charonosaurus from China, which may have been its closest relative, had a similar skull and potentially a similar crest. The crest has been much discussed by scientists; the consensus is that major functions included visual recognition of both species and sex, acoustic resonance, and thermoregulation. It is one of the rarer hadrosaurids, known from only a handful of good specimens. (see more...)

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Stegosaurus (/ˌstɛɡoʊˈsɔːrəs/, meaning "roof lizard" or "covered lizard" in reference to its bony plates) is a genus of armored stegosaurid dinosaur. They lived during the Late Jurassic period (Kimmeridgian to early Tithonian), some 155 to 150 million years ago in what is now western North America. In 2006, a specimen of Stegosaurus was announced from Portugal, showing that they were present in Europe as well. Due to its distinctive tail spikes and plates, Stegosaurus is one of the most recognizable dinosaurs. At least three species have been identified in the upper Morrison Formation and are known from the remains of about 80 individuals. A large, heavily built, herbivorous quadruped, Stegosaurus had a distinctive and unusual posture, with a heavily rounded back, short forelimbs, head held low to the ground and a stiffened tail held high in the air. Its array of plates and spikes has been the subject of much speculation. The spikes were most likely used for defense, while the plates have also been proposed as a defensive mechanism, as well as having display and thermoregulatory functions. Stegosaurus had a relatively low brain-to-body mass ratio. It had a short neck and small head, meaning it most likely ate low-lying bushes and shrubs. It was the largest of all the stegosaurians (bigger than genera such as Kentrosaurus and Huayangosaurus) and, although roughly bus-sized, it nonetheless shared many anatomical features (including the tail spines and plates) with the other stegosaurian genera. (see more...)

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Styracosaurus (/stɪˌrækəˈsɔːrəs/ stə-RAK-ə-SOR-əs; meaning "spiked lizard" from the Ancient Greek styrax/στύραξ "spike at the butt-end of a spear-shaft" and sauros/σαῦρος "lizard") was a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period (Campanian stage), about 75.5 to 75 million years ago. It had four to six long horns extending from its neck frill, a smaller horn on each of its cheeks, and a single horn protruding from its nose, which may have been up to 60 centimetres (2 ft) long and 15 centimetres (6 in) wide. The function or functions of the horns and frills have been debated for many years.

Styracosaurus was a relatively large dinosaur, reaching lengths of 5.5 metres (18 ft) and weighing nearly 3 tons. It stood about 1.8 meters (6 ft) tall. Styracosaurus possessed four short legs and a bulky body. Its tail was rather short. The skull had a beak and shearing cheek teeth arranged in continuous dental batteries, suggesting that the animal sliced up plants. Like other ceratopsians, this dinosaur may have been a herd animal, traveling in large groups, as suggested by bonebeds.

Named by Lawrence Lambe in 1913, Styracosaurus is a member of the Centrosaurinae. One species, S. albertensis, is currently assigned to Styracosaurus. Other species assigned to the genus have since been reassigned elsewhere. (see more...)

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Thescelosaurus (/ˌθɛsɪləˈsɔːrəs/ THESS-il-ə-SOR-əs; ancient Greek θέσκελος-/theskelos- meaning "godlike", "marvelous", or "wondrous" and σαυρος/sauros "lizard") was a genus of small ornithopod dinosaur that appeared at the very end of the Late Cretaceous period in North America. It was a member of the last dinosaurian fauna before the Cretaceous–Paleogene extinction event around 66 million years ago. The preservation and completeness of many of its specimens indicate that it may have preferred to live near streams.

This bipedal ornithopod is known from several partial skeletons and skulls that indicate it grew to between 2.5 and 4.0 meters (8.2 to 13.1 ft) in length on average. It had sturdy hind limbs, small wide hands, and a head with an elongate pointed snout. The form of the teeth and jaws suggest a primarily herbivorous animal. This genus of dinosaur is regarded as a specialized basal ornithopod, traditionally described as a hypsilophodont, but more recently recognized as distinct from Hypsilophodon. Several species have been suggested for this genus. Three currently are recognized as valid: the type species T. neglectus, as well as T. garbanii and T. assiniboiensis.

The genus attracted media attention in 2000, when a specimen unearthed in 1993 in South Dakota, United States, was interpreted as including a fossilized heart. There was much discussion over whether the remains were of a heart. Many scientists now doubt the identification of the object and the implications of such an identification. (see more...)

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Triceratops is a genus of herbivorous ceratopsid dinosaur that first appeared during the late Cretaceous period, about 68 million years ago in what is now North America. It is one of the last known non-avian dinosaur genera, and became extinct in the Cretaceous–Paleogene extinction event 66 million years ago. Its head bore a large bony frill and three horns while its body was massive and four-legged. It shared the landscape with and was probably preyed upon by the fearsome Tyrannosaurus.

The exact placement of the Triceratops genus within the ceratopsid group has been debated by paleontologists. Two species, T. horridus and T. prorsus, are considered valid. Research published in 2010 suggests that the contemporaneous Torosaurus, a ceratopsid long regarded as a separate genus, represents Triceratops in its mature form, a view not accepted by all researchers. Triceratops has been documented by numerous remains collected since the genus was first described in 1889, including at least one complete individual skeleton. Specimens representing life stages from hatchling to adult have been found.

The function of the frills and three distinctive facial horns has long inspired debate. Traditionally these have been viewed as defensive weapons against predators. More recent theories, noting the presence of blood vessels in the skull bones of ceratopsids, find it more probable that these features were primarily used in identification, courtship and dominance displays, much like the antlers and horns of modern reindeer, mountain goats, or rhinoceros beetles. (see more...)

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Tyrannosaurus is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex is commonly abbreviated to T. rex. It lived throughout what is now western North America. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 67 to 66 million years ago. It was among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event.

Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hindlimbs, Tyrannosaurus forelimbs were short and bore two clawed digits. Although other theropods rivaled or exceeded Tyrannosaurus rex in size it is one of the largest known land predators in history. The most complete specimen measures up to 12.3 m (40 ft) in length, up to 4 metres (13 ft) tall at the hips, and up to 6.8 metric tons (7.5 short tons) in weight. Tyrannosaurus rex would have been an apex predator, preying upon hadrosaurs, ceratopsians, and possibly sauropods.

More than 50 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology. Its taxonomy is also controversial: some scientists consider Tarbosaurus bataar from Asia to be a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. (see more...)

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The woolly mammoth (Mammuthus primigenius) was a species of mammoth, the common name for the extinct elephant genus Mammuthus. Its closest extant relative is the Asian elephant. The appearance and behaviour of this species are among the best studied of any prehistoric animal because of the discovery of frozen carcasses in Siberia and Alaska, as well as skeletons, teeth, stomach contents, dung, and depiction from life in prehistoric cave paintings. The mammoth was identified as an extinct species of elephant by Georges Cuvier in 1796. The woolly mammoth was roughly the same size as modern African elephants. Males reached shoulder heights between 2.7 and 3.4 m (9 and 11 ft) and weighed up to 6 tonnes (6.6 short tons). Females averaged 2.6–2.9 metres (8.5–9.5 ft) in height and weighed up to 4 tonnes (4.4 short tons). The woolly mammoth was well adapted to the cold environment during the last ice age. It was covered in fur, with an outer covering of long guard hairs and a shorter undercoat. The colour of the coat varied from dark to light. The ears and tail were short to minimise frostbite and heat loss. It had long, curved tusks and four molars, which were replaced six times during the lifetime of an individual. The diet of the woolly mammoth was mainly grass and sedges. Its habitat was the mammoth steppe, which stretched across northern Eurasia and North America. (see more...)

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Funerary art is any work of art forming, or placed in, a repository for the remains of the dead. The term also encompasses cenotaphs ("empty tombs"), tomb-like monuments which do not contain human remains; and communal memorials to the dead (such as war memorials), which may or may not contain human remains.

Funerary art may serve many cultural functions. It can play a role in burial rites, serve as an article for use by the dead in the afterlife, and celebrate the life and accomplishments of the dead, whether as part of kinship-centred practices of ancestor veneration or as a publicly directed dynastic display. It can also function as a reminder of the mortality of humankind, as an expression of cultural values and roles, and help to propitiate the spirits of the dead, maintaining their benevolence and preventing their unwelcome intrusion into the affairs of the living.

The deposit of objects with an apparent aesthetic intention may go back to the Neanderthals over 50,000 years ago,[1] and is found in almost all subsequent cultures—Hindu culture, which has little, is a notable exception. Many of the best-known artistic creations of past cultures—from the Egyptian pyramids and the Tutankhamun treasure to the Terracotta Army surrounding the tomb of the Qin Emperor, the Mausoleum of Halicarnassus, the Sutton Hoo ship burial and the Taj Mahal—are tombs or objects found in and around them. In most instances, specialized funeral art was produced for the powerful and wealthy, although the burials of ordinary people might include simple monuments and grave goods, usually from their possessions.

An important factor in the development of traditions of funerary art is the division between what was intended to be visible to visitors or the public after completion of the funeral ceremonies.[2] The Tutankhamun treasure, for example, though exceptionally lavish, was never intended to be seen again after it was deposited, while the exterior of the pyramids was a permanent and highly effective demonstration of the power of their creators. A similar division can be seen in grand East Asian tombs. In other cultures, nearly all the art connected with the burial, except for limited grave goods, was intended for later viewing by the public or at least those admitted by the custodians. In these cultures, traditions such as the sculpted sarcophagus and tomb monument of the Greek and Roman empires, and later the Christian world, have flourished. The mausoleum intended for visiting was the grandest type of tomb in the classical world, and later common in Islamic culture. (see more...)

24

Maya stelae (singular stela) are monuments that were fashioned by the Maya civilization of ancient Mesoamerica. They consist of tall sculpted stone shafts and are often associated with low circular stones referred to as altars, although their actual function is uncertain.[3] Many stelae were sculpted in low relief,[4] although plain monuments are found throughout the Maya region.[5] The sculpting of these monuments spread throughout the Maya area during the Classic Period (250–900 AD),[3] and these pairings of sculpted stelae and circular altars are considered a hallmark of Classic Maya civilization.[6] The earliest dated stela to have been found in situ in the Maya lowlands was recovered from the great city of Tikal in Guatemala.[7] During the Classic Period almost every Maya kingdom in the southern lowlands raised stelae in its ceremonial centre.[5]

Stelae became closely associated with the concept of divine kingship and declined at the same time as this institution. The production of stelae by the Maya had its origin around 400 BC and continued through to the end of the Classic Period, around 900, although some monuments were reused in the Postclassic (c. 900–1521). The major city of Calakmul in Mexico raised the greatest number of stelae known from any Maya city, at least 166, although they are very poorly preserved.[8]

Hundreds of stelae have been recorded in the Maya region,[9] displaying a wide stylistic variation.[5] Many are upright slabs of limestone sculpted on one or more faces,[5] with available surfaces sculpted with figures carved in relief and with hieroglyphic text.[4] Stelae in a few sites display a much more three-dimensional appearance where locally available stone permits, such as at Copán and Toniná.[5] Plain stelae do not appear to have been painted nor overlaid with stucco decoration,[10] but most Maya stelae were probably brightly painted in red, yellow, black, blue and other colours.[11]

Stelae were essentially stone banners raised to glorify the king and record his deeds,[12] although the earliest examples depict mythological scenes.[13] Imagery developed throughout the Classic Period, with Early Classic stelae (c. 250–600) displaying non-Maya characteristics from the 4th century onwards, with the introduction of imagery linked to the central Mexican metropolis of Teotihuacan.[14] This influence receded in the 5th century although some minor Teotihuacan references continued to be used.[15] In the late 5th century, Maya kings began to use stelae to mark the end of calendrical cycles.[16] In the Late Classic (c. 600–900), imagery linked to the Mesoamerican ballgame was introduced, once again displaying influence from central Mexico.[17] By the Terminal Classic, the institution of divine kingship declined, and Maya kings began to be depicted with their subordinate lords.[18] As the Classic Period came to an end, stelae ceased to be erected, with the last known examples being raised in 909–910. (see more...)

25

The Norte Chico civilization (also Caral or Caral-Supe civilization)[19] was a complex pre-Columbian society that included as many as 30 major population centers in what is now the Norte Chico region of north-central coastal Peru. Since the early 21st century, it has been established as the oldest known civilization in the Americas and one of the six sites where civilization originated independently in the ancient world. It flourished between 3rd and 1st millennia BC. The alternative name, Caral-Supe, is derived from the Sacred City of Caral[20] in the Supe Valley, a large and well-studied Norte Chico site. Complex society in Norte Chico arose a millennium after Sumer in Mesopotamia, was contemporaneous with the Egyptian pyramids, and predated the Mesoamerican Olmec by nearly two millennia.

In archaeological nomenclature, Norte Chico is a pre-ceramic culture of the pre-Columbian Late Archaic; it completely lacked ceramics and apparently had almost no visual art. The most impressive achievement of the civilization was its monumental architecture, including large earthwork platform mounds and sunken circular plazas. Archaeological evidence suggests use of textile technology and, possibly, the worship of common god symbols, both of which recur in pre-Columbian Andean cultures. Sophisticated government is assumed to have been required to manage the ancient Norte Chico. Questions remain over its organization, particularly the influence of food resources on politics. Some scholars have suggested that Norte Chico was founded on seafood and maritime resources, rather than development of an agricultural cereal and crop surpluses, as has been considered essential to the rise of other ancient civilizations.

Archaeologists have been aware of ancient sites in the area since at least the 1940s; early work occurred at Aspero on the coast, a site identified as early as 1905,[21] and later at Caral further inland.

In the late 1990s Peruvian archaeologists, led by Dr. Ruth Shady Solís, provided the first extensive documentation of the civilization with work at Caral.[22] A 2001 paper in Science, providing a survey of the Caral research,[23] and a 2004 article in Nature, describing fieldwork and radiocarbon dating across a wider area,[24] revealed Norte Chico's full significance and led to widespread interest. (see more...)

26 The Olmec colossal heads are at least seventeen monumental stone representations of human heads sculpted from large basalt boulders. The heads date from at least before 900 BC and are a distinctive feature of the Olmec civilization of ancient Mesoamerica.[25] All portray mature men with fleshy cheeks, flat noses, and slightly crossed eyes; their physical characteristics correspond to a type that is still common among the inhabitants of Tabasco and Veracruz. The backs of the monuments often are flat. The boulders were brought from the Sierra de los Tuxtlas mountains of Veracruz. Given that the extremely large slabs of stone used in their production were transported over large distances, requiring a great deal of human effort and resources, it is thought that the monuments represent portraits of powerful individual Olmec rulers. Each of the known examples has a distinctive headdress. The heads were variously arranged in lines or groups at major Olmec centres, but the method and logistics used to transport the stone to these sites remain unclear.

The discovery of a colossal head at Tres Zapotes in the nineteenth century spurred the first archaeological investigations of Olmec culture by Matthew Stirling in 1938. Seventeen confirmed examples are known from four sites within the Olmec heartland on the Gulf Coast of Mexico. Most colossal heads were sculpted from spherical boulders but two from San Lorenzo Tenochtitlán were re-carved from massive stone thrones. An additional monument, at Takalik Abaj in Guatemala, is a throne that may have been carved from a colossal head. This is the only known example from outside the Olmec heartland.

Dating the monuments remains difficult because of the movement of many from their original contexts prior to archaeological investigation. Most have been dated to the Early Preclassic period (1500–1000 BC) with some to the Middle Preclassic (1000–400 BC) period. The smallest weigh 6 tons, while the largest is variously estimated to weigh 40 to 50 tons, although it was abandoned and left unfinished close to the source of its stone. (see more...)

27

Quiriguá (Spanish pronunciation: [kiɾiˈɣwa]) is an ancient Maya archaeological site in the department of Izabal in south-eastern Guatemala. It is a medium-sized site covering approximately 3 square kilometres (1.2 sq mi) along the lower Motagua River, with the ceremonial center about 1 km (0.6 mi) from the north bank. During the Maya Classic Period (AD 200–900), Quiriguá was situated at the juncture of several important trade routes. The site was occupied by 200, construction on the acropolis had begun by about 550, and an explosion of grander construction started in the 8th century. All construction had halted by about 850, except for a brief period of reoccupation in the Early Postclassic (c. 900 – c. 1200). Quiriguá shares its architectural and sculptural styles with the nearby Classic Period city of Copán, with whose history it is closely entwined.

Quiriguá's rapid expansion in the 8th century was tied to king K'ak' Tiliw Chan Yopaat's military victory over Copán in 738. When the greatest king of Copán, Uaxaclajuun Ub'aah K'awiil or "18-Rabbit", was defeated, he was captured and then sacrificed in the Great Plaza at Quiriguá. Before this, Quiriguá had been a vassal state of Copán, but it maintained its independence afterwards. The ceremonial architecture at Quiriguá is quite modest, but the site's importance lies in its wealth of sculpture, including the tallest stone monumental sculpture ever erected in the New World.

(see more...)

28

Tak'alik Ab'aj (/tɑːkəˈliːk əˈbɑː/; Mayan pronunciation: [takʼaˈlik aˈɓaχ] (listen); Spanish: [takaˈlik aˈβax]) is a pre-Columbian archaeological site in Guatemala. It was formerly known as Abaj Takalik; its ancient name may have been Kooja. It is one of several Mesoamerican sites with both Olmec and Maya features. The site flourished in the Preclassic and Classic periods, from the 9th century BC through to at least the 10th century AD, and was an important centre of commerce,[26] trading with Kaminaljuyu and Chocolá. Investigations have revealed that it is one of the largest sites with sculptured monuments on the Pacific coastal plain.[27] Olmec-style sculptures include a possible colossal head, petroglyphs and others.[28] The site has one of the greatest concentrations of Olmec-style sculpture outside of the Gulf of Mexico.[28]

Takalik Abaj is representative of the first blossoming of Maya culture that had occurred by about 400 BC.[29] The site includes a Maya royal tomb and examples of Maya hieroglyphic inscriptions that are among the earliest from the Maya region. Excavation is continuing at the site; the monumental architecture and persistent tradition of sculpture in a variety of styles suggest the site was of some importance.[30]

Finds from the site indicate contact with the distant metropolis of Teotihuacan in the Valley of Mexico and imply that Takalik Abaj was conquered by it or its allies.[31] Takalik Abaj was linked to long-distance Maya trade routes that shifted over time but allowed the city to participate in a trade network that included the Guatemalan highlands and the Pacific coastal plain from Mexico to El Salvador.

Takalik Abaj was a sizeable city with the principal architecture clustered into four main groups spread across nine terraces. While some of these were natural features, others were artificial constructions requiring an enormous investment in labour and materials.[32] The site featured a sophisticated water drainage system and a wealth of sculptured monuments. (see more...)

29

Tyrannosaurus is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex is commonly abbreviated to T. rex. It lived throughout what is now western North America. Fossils are found in a variety of rock formations dating to the Maastrichtian age of the upper Cretaceous Period, 67 to 66 million years ago. It was among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event.

Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hindlimbs, Tyrannosaurus forelimbs were short and bore two clawed digits. Although other theropods rivaled or exceeded Tyrannosaurus rex in size it is one of the largest known land predators in history. The most complete specimen measures up to 12.3 m (40 ft) in length, up to 4 metres (13 ft) tall at the hips, and up to 6.8 metric tons (7.5 short tons) in weight. Tyrannosaurus rex would have been an apex predator, preying upon hadrosaurs, ceratopsians, and possibly sauropods.

More than 50 specimens of Tyrannosaurus rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology. Its taxonomy is also controversial: some scientists consider Tarbosaurus bataar from Asia to be a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. (see more...)

30 ?Oryzomys pliocaenicus is a fossil rodent from the Hemphillian (late Miocene) of Kansas, central United States. It is known from a single mandible (lower jaw) with the back part missing. All three molars are present, but very worn. Together, the molars are 3.6 mm long. The fossil was discovered in 1935 and described in 1939 as a possible species of Oryzomys (in open nomenclature). Later authors doubted this allocation and suggested that it may instead belong in Bensonomys or Jacobsomys, but the material may not allow a definite identification.(see more...)

31

Aetosaurs (order name Aetosauria) are an extinct order of heavily armoured, medium- to large-sized Late Triassic herbivorous archosaurs. They have small heads, upturned snouts, erect limbs, and a body covered by plate-like scutes. All aetosaurs belong to the family Stagonolepididae. Two distinct subdivisions of aeotosaurs are currently recognized, Desmatosuchinae and Aetosaurinae, based primarily on differences in the morphology of the bony scutes of the two groups. Over 20 genera of aetosaurs have been described.

Aetosaur fossil remains are known from Europe, North and South America, parts of Africa and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site that they are found in.

Aetosaur remains have been found since the early 19th century, although the very first remains that were described were mistaken for fish scales. Aetosaurs were later recognized as crocodile relatives, with early paleontologists considering them to be semiaquatic scavengers. They are now considered to have been entirely terrestrial animals. Some forms have characteristics that may have been adaptations to digging for food. There is also evidence that some if not all aetosaurs made nests. (see more...)

32

Chitinozoa (singular: chitinozoan, plural: chitinozoans) are a taxon of flask-shaped, organic walled marine microfossils produced by an as yet unknown animal. Common from the Ordovician to Devonian periods (i.e. the mid-Paleozoic), the millimetre-scale organisms are abundant in almost all types of marine sediment across the globe. This wide distribution, and their rapid pace of evolution, makes them valuable biostratigraphic markers.

Their bizarre form has made classification and ecological reconstruction difficult. Since their discovery in 1931, suggestions of protist, plant, and fungalaffinities have all been entertained. The organisms have been better understood as improvements in microscopy facilitated the study of their fine structure, and there is mounting evidence to suggest that they represent either the eggs or juvenile stage of a marine animal.

The ecology of chitinozoa is also open to speculation; some may have floated in the water column, where others may have attached themselves to other organisms. Most species were particular about their living conditions, and tend to be most common in specific paleoenvironments. Their abundance also varied with the seasons.(see more...)

33

The Cloudinids, an early metazoan family containing the genus Cloudina, lived in the late Ediacaran period and became extinct at the base of the Cambrian. They formed millimetre-scale conical fossils consisting of calcareous cones nested within one another; the appearance of the organism itself remains unknown. Current scientific opinion is divided between classifying them as polychaetes and regarding it as unsafe to classify them as members of any broader grouping.

Cloudinids had a wide geographic range, reflected in the present distribution of localities in which their fossils are found, and are an abundant component of some deposits. They never appear in the same layers as soft-bodied Ediacaran biota, but the fact that some sequences contain Cloudinids and Ediacaran biota in alternating layers suggests that these groups had different environmental preferences.

Cloudinids are important in the history of animal evolution for two reasons. They are among the earliest and most abundant of the small shelly fossils with mineralized skeletons, and therefore feature in the debate about why such skeletons first appeared in the Late Ediacaran. The most widely-supported answer is that their shells are a defense against predators, as some Cloudina specimens from China bear the marks of multiple attacks, which suggests they survived at least a few of them. The evolutionary arms race which this indicates is commonly cited as a cause of the Cambrian explosion of animal diversity and complexity. (see more...)

34

Coal balls, despite their name, are calcium-rich masses of permineralised life forms, generally having a round shape. Coal balls were formed roughly 300 million years ago, during the Carboniferous Period. They are exceptional at preserving organic matter, which makes them useful to scientists, who cut and peel the coal balls to research the geological past of the Earth.

In 1855, two English scientists, Joseph Dalton Hooker and Edward William Binney, discovered coal balls in England, and the initial research on coal balls was carried out in Europe. It was not until 1922 that coal balls were discovered and identified in North America. Since then, coal balls have been discovered in other countries and they have led to the discovery of over 300 species and 130 genera.

Coal balls can be found in coal seams across North America and Eurasia. North American coal balls are relatively widespread, both stratigraphically and geologically, as compared to coal balls from Europe. The oldest known coal balls were found in Germany and the former Czechoslovakia.

35

Dimetrodon is an extinct genus of synapsid that lived during the Early Permian, around 299–270 million years ago (Ma). It is a member of the family Sphenacodontidae. The most prominent feature of Dimetrodon is the large sail on its back formed by elongated spines extending from the vertebrae. It walked on four legs and had a tall, curved skull with large teeth of different sizes set along the jaws. Generally reptile-like in appearance and physiology, Dimetrodon is nevertheless more closely related to mammals than it is to any living reptilian group, though it is not a direct ancestor of any mammals. Most fossils have been found in the southwestern United States, the majority coming from a geological deposit called the Red Beds in Texas and Oklahoma. More recently, fossils have been found in Germany. Over a dozen species have been named since the genus was firstdescribed in 1878. Dimetrodon was probably one of the top predators in Early Permian ecosystems, feeding on fish and tetrapods, including reptiles as well as amphibians. Smaller Dimetrodon species may have had different ecological roles. The sail of Dimetrodon may have been used to stabilize its spine or to heat and cool its body as a form of thermoregulation. Some recent studies argue that the sail would have been ineffective at removing heat from the body, and was more likely used in sexual display. (see more...)

36

The Kirtlandian is a North American land-vertebrate faunal age of the Cretaceous period, following the Judithian and succeeded by the Edmontonian. It lasted about 2 million years, ca 74.8 to 72.8 Mya and is characterized by the ceratopsian Pentaceratops sternbergii, which lived throughout the Kirtlandian. It was first named by R.M. Sullivan and S.G. Lucas in 2003 as a faunal age for the Kirtland and Fruitland formations. Previously, only five land-vertebrate ages were identified from the Late Cretaceous. as identified by Loris S. Russell in 1975, they include the Paluxian, Aquilan, Judithian, Edmontonian, and the Lancian. Before the naming of the Kirtlandian, three gaps, between the Paluxian and Aquilan, the Aquilan and the Judithian, and the Judithian and Edmontonian, were identified but not named. The Fruitland Formation measures 97 to 107 metres (318 to 351 ft) thick, and with the 594 metres (1,949 ft) of the Kirtland Formation, the Kirtlandian consists of 701 metres (2,300 ft) of sediments. The rock types within the formations are primarily coal beds, but also include sandstone, siltstone, mudstone, and shale. Within the sediments with a Kirtlandian age, two local faunas, the Hunter Wash local fauna, and the Willow Wash local fauna, have been identified. The currently accepted date of the Kirtlandian is 74.8 to 72.8 million years ago. (see more...)

37

Macabeemyrma is an extinct genus of bulldog ants in the subfamily Myrmeciinae containing the single species Macabeemyrma ovata, described in 2006 from Ypresian stage (Early Eocene) deposits of British Columbia, Canada. Only a single specimen is known; a holotype queen found preserved as a compression fossil. The specimen had no wings and small portions of its legs and eyes were faintly preserved. It was a large ant, reaching 25 millimetres (0.98 in) in length. This ants' behaviour would have been similar to that of extant Myrmeciinae ants, such as foraging singly in search for arthropod prey and nesting in soil or in trees. Macabeemyrma shows similarities to extinct ants in the genus Ypresiomyrma, and to the living Nothomyrmecia macrops, but has not been conclusively assigned to any tribe, instead generally regarded as incertae sedis within Myrmeciinae. However, the sole specimen lacks definitive traits, and its classification in Myrmeciinae, and even its identity as an ant, has been challenged. (see more...)

38

Megalodon (/ˈmɛɡələdɒn/ MEG-ə-lə-don; meaning "big tooth", from Ancient Greek: μέγας, translit. (megas), lit. 'big, mighty' and ὀδoύς (odoús), "tooth"—whose stem is odont-, as seen in the genitive case form ὀδόντος, odóntos) is an extinct species of shark that lived approximately 15.9 to 2.6 million years ago, during the Cenozoic Era (middle Miocene to end of Pliocene).

The taxonomic assignment of C. megalodon has been debated for nearly a century, and is still under dispute. The two major interpretations are Carcharodon megalodon (under family Lamnidae) or Carcharocles megalodon (under the family Otodontidae). Consequently, the scientific name of this species is commonly abbreviated C. megalodon in the literature.

C. megalodon is regarded as one of the largest and most powerful predators in vertebrate history, and likely had a profound impact on the structure of marine communities. Fossil remains suggest that this giant shark reached a maximum length of 18 metres (59 ft), and also affirm that it had a cosmopolitan distribution. Scientists suggest that C. megalodon looked like a stockier version of the great white shark, Carcharodon carcharias. (see more...)

39

Opabinia is an extinct stem-arthropod genus found in Cambrian fossil deposits. The only known species, O. regalis, is known from the Middle Cambrian Burgess Shale Lagerstätte of British Columbia, Canada. Fewer than twenty good specimens have been described. Opabinia was a soft-bodied animal of modest size, and its segmented body had lobes along the sides and a fan-shaped tail. The head shows unusual features: five eyes, a mouth under the head and facing backwards, and a proboscis that probably passed food to the mouth. Opabinia probably lived on the seafloor, using the proboscis to seek out small, soft food. When the first thorough examination of Opabinia in 1975 revealed its unusual features, it was thought to be unrelated to any known phylum, although possibly related to a hypothetical ancestor of arthropods and of annelid worms. However other finds, most notably Anomalocaris, suggested that it belonged to a group of animals that were closely related to the ancestors of arthropods and of which the living animals onychophorans and tardigrades may also be members.(see more...)

40

Ornatifilum (Latin ornatis + filum, Ornamented filament) is an artificial form genus, which is used to categorise any small, branched filaments with external ornamentation. It has been applied to microfossils of Devonian age with possible fungal affinities; two "species" have been described, and further Silurian fossils closely resemble it. These Silurian specimens hint that the organisms may have been fungal, placing them among the oldest representatives of this kingdom. (see more...)

41

Othnielosaurus is a genus of ornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age Morrison Formation of the western United States. It is named in honor of famed paleontologist Othniel Charles Marsh, and was formerly assigned to the genus Laosaurus. This genus was coined to hold fossils formerly included in Othnielia, which is based on remains that may be too sparse to hold a name; as such, it is part of decades of research to untangle the taxonomy left behind by Marsh and his rival Edward Drinker Cope from the Bone Wars. Othnielosaurus has usually been classified as a hypsilophodont, a type of generalized small bipedal herbivore or omnivore, although recent research has called this and the existence of a distinct group of hypsilophodonts into question. (see more...)

42

Protomycena is an extinct monotypic genus of gilled fungus in the Mycenaceae family, of order Agaricales. At present it contains the single species Protomycena electra, known from a single specimen collected in an amber mine in the Cordillera Septentrional area of the Dominican Republic. The fruit body of the fungus has a convex cap that is 5 mm (0.2 in) in diameter, with distantly spaced gills on the underside. The curved stipe is smooth and cylindrical, measuring 0.75 mm (0.030 in) thick by 10 mm (0.39 in) long, and lacks a ring. It resembles extant (currently living) species of the genus Mycena. Protomycena is one of only five known agaric fungus species known in the fossil record and the second to be described from Dominican amber. (see more...)

43

Pteranodon (/tɪˈrænədɒn/; from Greek πτερόν ("wing") and ἀνόδων ("toothless")) is a genus of pterosaurs which included some of the largest known flying reptiles, with wingspans over 6 metres (20 ft). It existed during the late Cretaceous geological period of North America in present day Kansas, Alabama, Nebraska, Wyoming, and South Dakota. More fossil specimens of Pteranodon have been found than any other pterosaur, with about 1,200 specimens known to science, many of them well preserved with nearly complete skulls and articulated skeletons. It was an important part of the animal community in the Western Interior Seaway. Pteranodon was not a dinosaur. By definition, all dinosaurs belong to the groups Saurischia and Ornithischia, which exclude pterosaurs. Nevertheless, Pteranodon is frequently featured in dinosaur books and is strongly associated with dinosaurs by the general public. (see more...)

44

Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period (228 to 66 million years ago). Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger. Early species had long, fully toothed jaws and long tails, while later forms had a highly reduced tail, and some lacked teeth. Many sported furry coats made up of hair-like filaments known as pycnofibres, which covered their bodies and parts of their wings. Pterosaurs spanned a wide range of adult sizes, from the very small Nemicolopterus to the largest known flying creatures of all time, including Quetzalcoatlus and Hatzegopteryx. Pterosaurs are often referred to in the popular media and by the general public as flying dinosaurs, but this is incorrect. However, like the dinosaurs, pterosaurs are more closely related to birds than to any living reptile. Pterosaurs are also incorrectly referred to as pterodactyls, particularly by journalists. "Pterodactyl" refers specifically to members of the genus Pterodactylus, and more broadly to members of the suborder Pterodactyloidea of the pterosaurs. (see more...)

45

The Saint Croix macaw (Ara autocthones) is an extinct species of parrot. The last populations lived on the Caribbean islands Saint Croix and Puerto Rico. It was originally described by Alexander Wetmore in 1937 based on a subfossil limb bone unearthed by L. J. Korn in 1934 from a kitchen midden at an Amerindian archeological site on Saint Croix. A second specimen was described by Storrs L. Olson and Edgar J. Máiz López based on various limb and shoulder bones excavated from a similar site on Puerto Rico, while a possible third specimen from Montserrat has been reported. The species is one of two medium-sized macaws of the Caribbean, the other being the smaller Cuban red macaw (Ara tricolor). Its bones are distinct from Amazon parrots as well as from the other medium-sized but geographically distant Lear's macaw (Anodorhynchus leari) and blue-throated macaw (Ara glaucogularis). The natural range is unknown because parrots were regularly traded between islands by indigenous people. Like other parrot species in the Caribbean, the extinction of the Saint Croix macaw is believed to be linked to the arrival of humans in the region. (see more...)

46

The small shelly fauna or small shelly fossils, abbreviated to SSF, are mineralized fossils, many only a few millimetres long, with a nearly continuous record from the latest stages of the Ediacaran to the end of the Early Cambrian period. They are very diverse, and there is no formal definition of "small shelly fauna" or "small shelly fossils". Almost all are from earlier rocks than more familiar fossils such as trilobites. Since most SSFs were preserved by being covered quickly with phosphate and this method of preservation is mainly limited to the Late Ediacaran and Early Cambrian periods, the animals that made them may actually have arisen earlier and persisted after this time span. The bulk of the fossils are fragments or disarticulated remains of larger organisms, including sponges, molluscs, slug-like halkieriids, brachiopods, echinoderms, and onychophoran-like organisms that may have been close to the ancestors of arthropods. Although the small size and often fragmentary nature of SSFs makes it difficult to identify and classify them, they provide very important evidence for how the main groups of marine invertebrates evolved, and particularly for the pace and pattern of evolution in the Cambrian explosion. Besides including the earliest known representatives of some modern phyla, they have the great advantage of presenting a nearly continuous record of Early Cambrian organisms whose bodies include hard parts. (see more...)

47

Smilodon /ˈsmaɪlədɒn/, is an extinct genus of machairodont felid. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats. Smilodon lived in the Americas during the Pleistocene epoch (2.5 mya–10,000 years ago). The genus was named in 1842, based on fossils from Brazil. Three species are recognized today: S. gracilis, S. fatalis and S. populator.

Overall, Smilodon was more robustly built than any extant (living) cat, with particularly well-developed forelimbs and exceptionally long upper canines. Its jaw had a bigger gape than that of modern cats and its upper canines were slender and fragile, being adapted for precision killing. S. gracilis was the smallest species at 55 to 100 kg (120 to 220 lb) in weight. S. populator from South America is perhaps the largest known felid at 220 to 400 kg (490 to 880 lb) in weight and 120 cm (47 in) in height.

Smilodon probably lived in closed habitats such as forests and bush, which would have provided cover for ambushing prey. Smilodon died out at the same time that most North and South American megafauna disappeared, about 10,000 years ago. Its reliance on large animals has been proposed as the cause of its extinction, along with climate change and competition with other species, but the exact cause is unknown. (see more...)

48

The Temnospondyli are a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian, and Triassic periods. A few species continued into the Cretaceous. Fossils have been found on every continent. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including fresh water, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis, and maturity. Most temnospondyls were semiaquatic, although some were almost fully terrestrial, returning to the water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are considered amphibians, many had characteristics, such as scales, claws, and armor-like bony plates, that distinguish them from modern amphibians. Authorities disagree over whether temnospondyls were ancestral to modern amphibians (frogs, salamanders, and caecilians), or whether the whole group died out without leaving any descendants. Different hypotheses have placed modern amphibians as the descendants of temnospondyls, another group of early tetrapods called lepospondyls, or even as descendants of both groups (with caecilians evolving from lepospondyls and frogs and salamanders evolving from temnospondyls). Recent studies place a family of temnosondyls called the amphibamids as the closest relatives of modern amphibians. Similarities in teeth, skulls, and hearing structures link the two groups. (see more...)

Selected articles covering the Prehistory of North America and human science, culture, and economics

1

Bone Sharps, Cowboys, and Thunder Lizards: A Tale of Edward Drinker Cope, Othniel Charles Marsh, and the Gilded Age of Paleontology (2005) is a graphic novel written by Jim Ottaviani and illustrated by the company Big Time Attic. The book tells a slightly fictionalized account of the Bone Wars, a period of intense excavation, speculation, and rivalry which led to a greater understanding of dinosaurs in the western United States. This novel is the first semi-fictional work written by Ottaviani; previously, he had taken no creative license with the characters he depicted, portraying them strictly according to historical sources. Bone Sharps follows the two scientists Edward Drinker Cope and Othniel Marsh as they engage in an intense rivalry for prestige. Ottaviani has Cope and Marsh interact and meet many important figures of the Gilded Age, from P. T. Barnum to U.S. Grant, as the two scientists pursue their hotheaded and sometimes illegal acquisitions of fossils. Unlike in his previous books, "the scientists are the bad guys this time". Upon release, the novel received praise from critics for its exceptional historical content, although some reviewers wished more fiction had been woven into the story. (see more...)

2

The Bone Wars is the name given to a period of intense fossil speculation and discovery during the Gilded Age of American history, marked by a heated rivalry between Edward Drinker Cope and Othniel Charles Marsh. The two paleontologists used underhanded methods to out-compete the other in the field, resorting to bribery, theft, and destruction of bones. The scientists also attacked each other in scientific publications, attempting to ruin the other's credibility and cut off his funding.

Originally colleagues who were civil to each other, Cope and Marsh became bitter enemies after several personal slights between them. Their pursuit of bones led them west to rich bone beds in Colorado, Nebraska, and Wyoming. From 1877 to 1892, both paleontologists used their wealth and influence to finance their own expeditions and to procure services and fossils from dinosaur hunters. By the end of the Bone Wars, both men exhausted their funds in fueling their intense rivalry.

Cope and Marsh were financially and socially ruined by their efforts to disgrace each other, but their contributions to science and the field of paleontology were massive; the scientists left behind tons of unopened boxes of fossils on their deaths. The feud between the two men led to over 142 new species of dinosaurs being discovered and described. Several historical books and fictional adaptations have also been published about this period of intense paleontological activity. (see more...)

3

Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Cope distinguished himself as a child prodigy, publishing his first scientific paper at the age of nineteen. Cope later married and moved from Philadelphia to Haddonfield, New Jersey, although Cope would maintain a residence and museum in Philadelphia in his later years.

Cope had little formal scientific training, and he eschewed a teaching position for field work. He made regular trips to the American West prospecting in the 1870s and 1880s, often as a member of United States Geological Survey teams. A personal feud between Cope and paleontologist Othniel Charles Marsh led to a period of intense fossil-finding competition now known as the Bone Wars. Cope's financial fortunes soured after failed mining ventures in the 1880s. He experienced a resurgence in his career toward the end of his life before dying in 1897.

Cope's scientific pursuits nearly bankrupted him, but his contributions helped to define the field of American paleontology. He was a prodigious writer, with 1,400 papers published over his lifetime, although his rivals would debate the accuracy of his rapidly published works. He discovered, described, and named more than 1,000 vertebrate species including hundreds of fishes and dozens of dinosaurs. His proposals on the origin of mammalian molars and for the gradual enlargement of mammalian species over geologic time ("Cope's Law") are notable among his theoretical contributions. (see more...)

4

Petrified Forest National Park is a United States national park in Navajo and Apache counties in northeastern Arizona. Named for its large deposits of petrified wood, the park covers about 146 square miles (380 km2), encompassing semi-desert shrub steppe as well as highly eroded and colorful badlands. The site, the northern part of which extends into the Painted Desert, was declared a national monument in 1906 and a national park in 1962. The Petrified Forest is known for its fossils, especially fallen trees that lived in the Late Triassic, about 225 million years ago. The sediments containing the fossil logs are part of the widespread and colorful Chinle Formation, from which the Painted Desert gets its name. Beginning about 60 million years ago, the Colorado Plateau, of which the park is part, was pushed upward by tectonic forces and exposed to increased erosion. All of the park's rock layers above the Chinle, except geologically recent ones found in parts of the park, have been removed by wind and water. In addition to petrified logs, fossils found in the park have included Late Triassic ferns, cycads, ginkgoes, and many other plants as well as fauna including giant reptiles called phytosaurs, large amphibians, and early dinosaurs. Paleontologists have been unearthing and studying the park's fossils since the early 20th century. (see more...)

5

Chaco Culture National Historical Park is a United States National Historical Park hosting the densest and most exceptional concentration of pueblos in the American Southwest. The park is located in northwestern New Mexico, between Albuquerque and Farmington, in a remote canyon cut by the Chaco Wash. Containing the most sweeping collection of ancient ruins north of Mexico, the park preserves one of the United States' most important pre-Columbian cultural and historical areas.

Between AD 900 and 1150, Chaco Canyon was a major center of culture for the Ancient Pueblo Peoples. Chacoans quarried sandstone blocks and hauled timber from great distances, assembling fifteen major complexes that remained the largest buildings in North America until the 19th century. Evidence of archaeoastronomy at Chaco has been proposed, with the "Sun Dagger" petroglyph at Fajada Butte a popular example. Many Chacoan buildings may have been aligned to capture the solar and lunar cycles, requiring generations of astronomical observations and centuries of skillfully coordinated construction. Climate change is thought to have led to the emigration of Chacoans and the eventual abandonment of the canyon, beginning with a fifty-year drought commencing in 1130.

Composing a UNESCO World Heritage Site located in the arid and sparsely populated Four Corners region, the Chacoan cultural sites are fragile; concerns of erosion caused by tourists have led to the closure of Fajada Butte to the public. The sites are considered sacred ancestral homelands by the Hopi and Pueblo people, who maintain oral accounts of their historical migration from Chaco and their spiritual relationship to the land. Though park preservation efforts can conflict with native religious beliefs, tribal representatives work closely with the National Park Service to share their knowledge and respect the heritage of the Chacoan culture.

It is on the Trails of the Ancients Byway, one of the designated New Mexico Scenic Byways. (see more...)

6

Sylvanus Griswold Morley (June 7, 1883 – September 2, 1948) was an American archaeologist, epigrapher, and Mayanist scholar who made significant contributions toward the study of the pre-Columbian Maya civilization in the early 20th century.

Morley made extensive excavations of the Maya site of Chichen Itza that he directed on behalf of the Carnegie Institution. He also published several large compilations and treatises on Maya hieroglyphic writing, and wrote popular accounts on the Maya for a general audience.

To his contemporaries, "Vay" Morley was one of the leading Mesoamerican archaeologists of his day. Although more recent developments in the field have resulted in a re-evaluation of his theories and works, his publications, particularly on calendric inscriptions, are still cited. In his role as director of various projects sponsored by the Carnegie Institution, he oversaw and encouraged many others who later established notable careers in their own right. His commitment and enthusiasm for Maya studies helped inspire the necessary sponsorship for projects that would ultimately reveal much about ancient Maya civilization.

Morley also conducted espionage in Mexico on behalf of the United States during World War I, but the scope of those activities only came to light well after his death. His archaeological field work in Mexico and Central America provided suitable cover for investigating German activities and anti-American activity at the behest of the United States' Office of Naval Intelligence. (see more...)

7

The history of paleontology traces the history of the effort to study the fossil record left behind by ancient life forms. Although fossils had been studied by scholars since ancient times, the nature of fossils and their relationship to life in the past became better understood during the 17th and 18th centuries. At the end of the 18th century the work of Georges Cuvier ended a long running debate about the reality of extinction and led to the emergence of paleontology as a scientific discipline.

The first half of the 19th century saw paleontological activity become increasingly well organized. This contributed to a rapid increase in knowledge about the history of life on Earth, and progress towards definition of the geologic time scale. As knowledge of life's history continued to improve, it became increasingly obvious that there had been some kind of successive order to the development of life. After Charles Darwin published Origin of Species in 1859, much of the focus of paleontology shifted to understanding evolutionary paths.

The last half of the 19th century saw a tremendous expansion in paleontological activity, especially in North America. The trend continued in the 20th century with additional regions of the Earth being opened to systematic fossil collection, as demonstrated by a series of important discoveries in China near the end of the 20th century. There was also a renewed interest in the Cambrian explosion that saw the development of the body plans of most animal phyla. (see more...)

8 Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. He was also one of the most influential and widely read writers of popular science of his generation. Gould spent most of his career teaching at Harvard University and working at the American Museum of Natural History in New York. In the later years of his life, Gould also taught biology and evolution at New York University.

Gould's most significant contribution to evolutionary biology was the theory of punctuated equilibrium, which he developed with Niles Eldredge in 1972. The theory proposes that most evolution is marked by long periods of evolutionary stability, which is punctuated by rare instances of branching evolution. The theory was contrasted against phyletic gradualism, the popular idea that evolutionary change is marked by a pattern of smooth and continuous change in the fossil record.

Most of Gould's research was based on the land snail genera Poecilozonites and Cerion. He also contributed to evolutionary developmental biology, and has received wide praise for his book Ontogeny and Phylogeny. In evolutionary theory he opposed strict selectionism, sociobiology as applied to humans, and evolutionary psychology. Gould was known by the general public mainly from his 300 popular essays in the magazine Natural History, and his books written for a non-specialist audience.

In April 2000, the US Library of Congress named him a "Living Legend". (see more...)

9

Raptor Red is a 1995 American novel by paleontologist Robert T. Bakker. The book is a third-person account of dinosaurs during the Cretaceous Period, told from the point of view of Raptor Red, a female Utahraptor. Raptor Red features many of Bakker's theories regarding dinosaurs' social habits, intelligence, and the world in which they lived.

The book follows a year in Raptor Red's life as she loses her mate, finds her family, and struggles to survive in a hostile environment. Bakker drew inspiration from Ernest Thompson Seton's works that look at life through the eyes of predators, and said that he found it "fun" to write from a top predator's perspective. Bakker based his portrayals of dinosaurs and other prehistoric wildlife on fossil evidence, as well as studies of modern animals.

When released, Raptor Red was generally praised: Bakker's anthropomorphism was seen as a unique and positive aspect of the book, and his writing was described as folksy and heartfelt. Criticisms of the novel included a perceived lack of characterization and average writing. Some scientists, such as paleontologist David B. Norman, took issue with the scientific theories portrayed in the novel, fearing that the public would accept them as fact, while Discovery Channel host Jay Ingram defended Bakker's creative decisions in an editorial.

(see more...)

DYK

Selected pictures

Cast of the skull and neck vertebrae of a Uintatherium anceps. The specimen was a gift from Professor Othniel Charles Marsh to the Museum National d'Histoire Naturelle of Paris, France in 1889.
Photo credit: Jebulon

Mounted skull and neck of the 150 million year old Late Jurassic theropod Allosaurus fragilis. The specimen was discovered in the US state of Utah and is exhibited in the Galerie de paléontologie et d'anatomie comparée of the Muséum National d'Histoire Naturelle in Paris, France.
Photo credit: Jebulon

Rock formations known as the Tepees in Petrified Forest National Park Arizona, USA. The exposed rock layers belong to the Blue Mesa Member of the Chinle Formation and are about 220 to 225 million years old. The colorful bands of mudstone and sandstone were laid down during the Triassic, when the area was part of a huge tropical floodplain.
Photo credit: User:Finetooth

The middle of a polished 15.34 cm × 18.04 cm slice of a petrified tree from Arizona, USA. After the enlargement of the image it is possible to see insect borings in the wood. The tree lived approximately 230 million years ago during the Late Triassic.
Photo credit: Michael Gäbler

Close up image of petrified wood from Canyonlands National Park in Utah, USA.
Photo credit: Jim Gordon

Various views of a Pliocene shell of the lightning whelk Busycon contrarium from La Belle, Florida, USA. The specimen is 24 cm long.
Photo credit: H. Zell

Fossil remains of various horse genera, showing the evolution of their skeletons, skulls and limb bones over time. The uppermost and most recent genus is that of the modern horse, Equus. Below that is Pliohippus, dating back to the late Miocene. Below that and older still is Merychippus of the middle Miocene. The bottom and oldest horse genus is Mesohippus from the late Eocene.
Photo credit: H. Zell

A mounted skeleton of a Late Cretaceous mosasaurid species belonging to the genus Plioplatecarpus, probably P. ictericus. In life the animal would have been about 5.5 m in length. The mounted skeleton is actually a composite of two individuals collected from the Niobrara Formation, of Kansas, USA and is exhibited in the Museum für Naturkunde in Karlsruhe, Germany.
Photo credit: H. Zell

A life restoration of the Late Cretaceous ceratopsid dinosaur Achelousaurus horneri from the Two Medicine Formation of Montana, USA.
Artist credit: Mariana Ruiz

Fossil shells of the scaphitid ammonoids Hoploscaphites (left) and Discoscaphites (right). The shell dates back to the Maastrichtian age (66–72.1 million years ago) of the Late Cretaceous epoch. The Specimen was collected in South Dakota, USA.
Photo credit: H. Zell

A fossil of the asaphid trilobite Megalaspides . This specimen dates back to the Ordovician period. It was collected in Ohio, USA and is displayed by the Staatliches Museum für Naturkunde in Karlsruhe, Germany.
Photo credit: H. Zell

A cluster of fossils fossil of the trilobite Homotelus bromidensis. This specimen dates back to the Ordovician period and was discovered in Oklahoma, USA.
Photo credit: High Contrast

Related

Prehistory of Africa	Prehistory of South America	Prehistory of Antarctica	Prehistory of Asia	Prehistory of Europe
Prehistory of Oceania	North America	Archaeology	Earth sciences	Paleontology
Extinct and Endangered Species	Paleozoic	Mesozoic	Cenozoic	Dinosaurs

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Featured prehistory of North America articles - Acrocanthosaurus - Albertosaurus - Allosaurus - Bone Sharps, Cowboys, and Thunder Lizards - Bone Wars - Chicxulub crater - Columbian mammoth - Edward Drinker Cope - Cretaceous–Paleogene extinction event - Daspletosaurus - Deinonychus - Deinosuchus - Dinosaur - Diplodocus - Ediacara biota - Edmontosaurus - Gorgosaurus - Lambeosaurus - Parasaurolophus - Petrified Forest National Park - Stegosaurus - Styracosaurus - Thescelosaurus - Triceratops - Tyrannosaurus - Woolly mammoth

Good prehistory of North America articles - ?Oryzomys pliocaenicus - Aetosaur - Archaeomarasmius - Chitinozoan - Cloudinid - Coal ball - Dimetrodon - Stephen Jay Gould - History of paleontology - Kirtlandian - Macabeemyrma - Megalodon - Ornatifilum - Othnielosaurus - Protomycena - Pteranodon - Pterosaur - Saint Croix macaw - Small shelly fauna - Smilodon - Temnospondyli - Tiktaalik - Waptia