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Kimberella is a genus of disputable multicellular organism known from fossils that date back to the Ediacaran period, and only one species, K. quadrata, has been recognized. Specimens were first found in Australia's Ediacara Hills, but recent research has concentrated on the numerous finds near the White Sea in Russia, which cover an interval of time from 555-558 Ma. As with many fossils from this time, its evolutionary relationships to other organisms is hotly debated. Paleontologists initially classified Kimberella as a type of jellyfish, but since 1997 features of its anatomy and its association with scratch marks resembling those made by a radula have been interpreted as signs that it may have been a mollusc. Although some paleontologists dispute its classification as a mollusc, it is generally accepted as being at least a bilaterian. The classification of Kimberella is important for scientific understanding of the Cambrian explosion: if it was a mollusc or at least a protostome, the protostome and deuterostome lineages must have diverged significantly before 555 Ma. Even if it was a bilaterian but not a mollusc, its age would indicate that animals were diversifying well before the start of the Cambrian. (Read more...)



Massospondylus is a genus of prosauropod dinosaur from the early Jurassic Period, ca. 200–183 million years ago. It was described by Sir Richard Owen in 1854 from remains found in South Africa, and is thus one of the first dinosaurs to have been named. Fossils have since been found in other parts of South Africa, as well as Lesotho and Zimbabwe. Further material from the United States Kayenta Formation, India, and Argentina has been assigned to this genus, but may not belong to Massospondylus. The type, and only universally recognized species, is M. carinatus, although six other species have been named during the past 150 years. Prosauropod systematics have undergone numerous revisions during the last several years, and many scientists disagree where exactly Massospondylus lies on the dinosaur evolutionary tree. Although Massospondylus was long depicted as quadrupedal, a 2007 study found it to be bipedal. It was probably a plant eater (herbivore), although it is speculated that the prosauropods may have been omnivorous. This animal, 4–6 meters (13–20 ft) long, had a long neck and tail, with a small head and slender body. (Read more...)



Rhynchosaurs (meaning "beaked lizards") were a group of unusual herbivorous quadrupedal archosauromorphs that lived during the Triassic period. Rhynchosaurs ranged in size from the 50 cm long Rhynchosaurus to the 2 meter (6 feet) long Hyperodapedon, with the average size being 1 meter (3.3 feet). Rhynchosaurs were a widespread and worldwide taxon, being found all across the supercontinent of Pangaea. Rhynchosaur fossils have been found in Britain, South Africa, Zimbabwe, Tanzania, Madagascar, India, Brazil, Argentina, Canada and the United States, although they are poorly represented in the Northern Hemisphere fossil record. 15 species are currently regarded as valid, and another five are valid taxa still in need of a name. In some fossil assemblages, several taxa lived alongside one another, as evidenced by the four contemporaneous species were contemporaneous in the Upper Triassic Santa Maria Formation of Brazil. Rhynchosaurs went extinct during the Permian-Triassic extinction event that marked the end of the Carnian stage of the Late Triassic. Rhynchosaur fossils are very abundant in some assemblages (in some fossil localities accounting for 40 to 60% of specimens found) and the anatomy and ontogeny of a few species is comparatively well known. Early primitive forms like Mesosuchus and Howesia were more typically lizard-like in build, and had skulls rather similar to the early diapsid Younginia, except for the beak and a few other features. (Read more...)



There have been a number of potential species assigned to Allosaurus, a carnosaurian dinosaur, since its description in 1877 by Othniel Charles Marsh, but only a handful are still regarded as valid. Allosaurus was originally described from material from the Upper Jurassic Morrison Formation of the western United States of America; the type species A. fragilis became one of the best-known species of dinosaur. The genus Allosaurus was part of the Marsh/Edward Drinker Cope "Bone Wars" of the late 1800s, and its taxonomy became increasingly confused due to the competition, with several genera and species named by Cope and Marsh now regarded as synonyms of Allosaurus or A. fragilis. Since the description of Allosaurus, scientists have proposed additional species from such far-flung locales as Portugal, Siberia, Switzerland, and Tanzania, Australia and unnamed remains from China have also been assigned to the genus at one time or another. It is unclear how many species of Allosaurus there were. Seven species have been considered potentially valid since 1988. There are also at least ten dubious or undescribed species that have been assigned to Allosaurus over the years, along with the species belonging to genera now sunk into Allosaurus. (Read more...)



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. Each of 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. (Read more...)



Lystrosaurus is an extinct genus of dicynodont therapsid that lived during the Late Permian and Early Triassic periods, around 250 million years ago in what is now Antarctica, India and South Africa. At present 4 to 6 species are recognized, although from the 1930s to 1970s the number of species was thought to be much higher. Lystrosaurus had only two teeth, as with all other dicynodonts, as well as a pair of tusk-like canines. Lystrosaurus is thought to have had a horny beak that was used for biting off pieces of vegetation. Lystrosaurus was a heavily-built, herbivorous animal, approximately the size of a pig. The structure of its shoulders and hip joints suggest that Lystrosaurus moved with a semi-sprawling gait. Lystrosaurus was by far the most common terrestrial vertebrate of the Early Triassic, accounting for as many as 95% of the total individuals in some fossil beds. It has often been suggested that it had anatomical features that enabled it to adapt better than most animals to the atmospheric conditions that were created by the Permian–Triassic extinction event and which persisted through the Early Triassic — low concentrations of oxygen and high concentrations of carbon dioxide. However recent research suggests that these features were no more pronounced in Lystrosaurus than in genera that perished in the extinction or genera that survived but were much less abundant than Lystrosaurus. (Read more...)



Acrocanthosaurus (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 and Texas, 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 about 2.40 metric tons (2.65 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. However, there is still debate over its evolutionary relationships, with some scientists classifying it as an allosaurid, and others as a carcharodontosaurid. Acrocanthosaurus was the largest theropod in its ecosystem and likely an apex predator which possibly preyed on large sauropods and ornithopods. (Read more...)



Deinosuchus is an extinct relative of the alligator that lived 80 to 73 Ma (million years ago), during the Late Cretaceous period. The first remains were discovered in North Carolina in the 1850s, but it was not until 1909 that the genus was named and described. Additional fragments were discovered in the 1940s and were later incorporated into an influential, though inaccurate, skull reconstruction at the American Museum of Natural History. Knowledge of Deinosuchus remains incomplete, but better cranial material found in recent years has expanded scientific understanding of this massive predator. Although Deinosuchus was far larger than any modern crocodile or alligator&mdash;measuring up to 12 m (40 ft) and weighing up to 8.5 metric tons (9.4 short tons)&mdash;its overall appearance was fairly similar to its smaller relatives. It had large, robust teeth that were built for crushing, and its back was covered with thick semispherical osteoderms. One study indicates that Deinosuchus may have lived for up to 50 years, growing at a similar rate to that of modern crocodilians, but maintaining this growth over a much longer period of time. (Read more...)



Kritosaurus (meaning "separated lizard"; sometimes misinterpreted as "noble lizard", in reference to the presumed "Roman nose"; the nasal region was fragmented, disarticulated, and originally restored flat) is an incompletely known but historically important genus of extinct hadrosaurid (duckbilled) dinosaur. It lived about 73 million years ago, during the Late Cretaceous of North and possibly South America. Its taxonomic history is convoluted, also incorporating Gryposaurus, Anasazisaurus, and Naashoibitosaurus; this tangle will remain unresolved until better remains of Kritosaurus are described. Despite the dearth of material, this herbivore appeared in dinosaur books until the 1990s, although what was usually represented was the much more completely known Gryposaurus, then thought to be a synonym. In 1904, Barnum Brown discovered the type specimen (AMNH 5799) of Kritosaurus near Ojo Alamo, San Juan County, New Mexico, United States, while following up on a previous expedition. He initially could not definitely correlate the stratigraphy, but by 1916 was able to establish it as from what is now known as the late Campanian-age De-na-zin Member of the Kirtland Formation. (Read more...)



Aetosaurs, (meaning "Eagle Lizards") are an extinct clade of heavily armored, medium to large-sized Late Triassic quadrupedal archosaurs that were mostly herbivorous. Aetosaurs are widely characterized by their dorsal and ventral surfaces being encased in parallel rows of subrectangular osteoderms, some of which sported spikes in some species. Aetosaurs ranged in size from 1–5 meters (3–16 ft), with the average size being between 2.5–3 meters (8–10 ft). Some of the smallest aetosaurs were Aetosaurus and Coahomasuchus, reaching no more than a meter in length. Aetosaur fossils were first documented by paleontologist Louis Agassiz (1807-1873) in 1844, although they were originally attributed armored fish, instead of archosaurs. Two distinct subdivisions of aeotosaurs are currently recognized, the Desmatosuchinae and the Aetosaurinae, based primarily on differences in the morphology of the bony scutes of the two groups. Aetosaurs first appeared during the Late Carnian epoch of the Late Triassic, roughly the same time that phytosaurs and ornithosuchids appeared. From that point on, they quickly diversified, into various genera, with the most notable being Aetosaurus, Stagonolepis, and Desmatosuchus, and existed for nearly the entirety of the Late Triassic. Aetosaurs quickly became widespread across the the supercontinent Pangaea, with their fossils being found in Europe (Scotland, Germany), India, Northern Africa, North (United States) and South America (Argentina), Greenland and Madagascar. (Read more...)



Allosaurus is a genus of large theropod dinosaur that lived 155 to 145 million years ago, in the Late Jurassic period (Kimmeridgian to Tithonian). The first remains that can definitely be ascribed to this genus were described in 1877 by Othniel Charles Marsh. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles, and has been a lead dinosaur in several films and documentaries. Allosaurus was a large bipedal predator with a large skull, equipped with dozens of large, sharp teeth. It averaged 8.5 meters (28 ft) in length, though fragmentary remains suggest it could have reached over 12 meters (39 ft). Relative to the large and powerful hindlimbs, its three-fingered forelimbs were small, and the body was balanced by a long, heavy tail. 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. It was known for over half of the 20th century as Antrodemus, but study of the copious remains from the Cleveland Lloyd Dinosaur Quarry brought the name Allosaurus back to prominence, and established it as one of the best-known dinosaurs. 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, and that congregations of this genus are the result of lone individuals feeding on the same carcasses. It may have attacked large prey by ambush, using its upper jaws like a hatchet. (Read more...)



"Archaeoraptor" is the generic name informally assigned in 1999 to a fossil from China in an article published in National Geographic magazine. The magazine claimed that the fossil was a "missing link" between birds and terrestrial theropod dinosaurs. Even prior to this publication there had been severe doubts about the fossil's authenticity. It led to a scandal when it was definitely proven to be a forgery through further scientific study. The forgery was constructed from rearranged pieces of real fossils from different species. Zhou et al. found that the head and upper body actually belong to a specimen of the primitive fossil bird Yanornis. A 2002 study found that the tail belongs to a small winged dromaeosaur, Microraptor, named in 2000. The legs and feet belong to an as yet unknown animal. The "Archaeoraptor" scandal has ongoing ramifications. The scandal brought attention to illegal fossil deals conducted in China. It also highlighted the need for close scientific scrutiny of purported "missing links" published in journals which are not peer-reviewed. The fossil scandal has been used by creationists to cast doubt on evolutionary theory. Although "Archaeoraptor" was a forgery, many true examples of feathered dinosaurs have been found and demonstrate the evolutionary connection between birds and other theropods. (Read more...)



Crassigyrinus (meaning "thick tadpole") is an extinct genus of carnivorous stem group tetrapod from the Early Carboniferous of Scotland and a possible specimen from Greer, West Virginia. The type specimen was originally described as Macromerium scoticum and lacked a complete skull. With subsequent discoveries, Crassigyrinus is now known from three skulls, one of which is in articulation with a fairly complete skeleton, and a couple of incomplete lower jaws. Crassigyrinus grew up to 1.5 meters in length, coupled with punitive limbs and unusually large jaws. Crassigyrinus is taxonomically enigmatic, having confused paleontologists for decades with its apparent fish-like and tetrapod features. Some paleontologists have even considered it as the most basal tetrapod, while others hesitate to even place it within the Tetrapoda superclass. Crassigyrinus had unusually large jaws, enabling it to eat other animals it could catch and swallow. It had two rows of sharp teeth in its jaws, the second row having a pair of fangs. Crassigyrinus had large eyes, suggesting that it was either nocturnal, or lived in very murky water. (Read more...)



Darwinius is a genus of extinct Adapiformes, a group of basal or stem group primates from the Eocene epoch, 47 million years ago (Lutetian stage) based on dating of the fossil site. The genus name, Darwinius, was named to celebrate Charles Darwin on his bicentenary and the species name, masillae, honors the Messel pit, where the specimen was found.) The only known fossil, dubbed Ida, was discovered in 1983 at the Messel pit, a disused shale quarry noted for its astonishing fossil preservation, near the village of Messel, about 35 kilometers (22 mi) southeast of Frankfurt am Main. The fossil, divided into a positive and negative slab after the amateur excavation and sold separately, was not reassembled until the early months of 2007, and formally published in 2009. The fossil is of a juvenile female, approximately 58 cm (23 in) overall length, and it is estimated that Ida died at about 80–85% of her projected adult body and limb length. The scientists who published the initial paper on Darwinius described it as a significant transitional form between early primitive primates and the later prosimian and simian lineages. The creature appeared superficially similar to a modern lemur. The fossil is classified as lying near the separation of two major primate clades: one leading to the prosimians, the other to the anthropoid monkeys and, eventually, to the great apes, including Homo sapiens. However, concerns have been raised about the claims made about its relative importance, and the publicizing of the fossil before adequate information was available for scrutiny by other scientists. (Read more...)



Dromaeosaurids are a family of extinct bird-like theropod dinosaurs. They were small to medium-sized, feathered carnivores that flourished during the Cretaceous Period. In informal usage they are often called "raptors" (after Velociraptor), a term popularized by the film Jurassic Park and have become iconic for their enlarged "sickle claw" on the second toe. The name Dromaeosauridae means 'running lizards', from Greek dromeus (δρομευς) meaning 'runner' and sauros (σαυρος) meaning 'lizard'. Dromaeosaurid fossils have been found in North America, Europe, North Africa, Japan, China, Mongolia, Madagascar, Argentina, and Antarctica. They first appeared in the mid-Jurassic Period (Bathonian stage, 167 million years ago) and survived until the end of the Cretaceous (Maastrichtian stage, 65.5 ma), existing for over 100 million years, up until the Cretaceous-Paleogene extinction event. The presence of dromaeosaurs as early as the Middle Jurassic has been confirmed by the discovery of isolated fossil teeth, though no dromaeosaurid body fossils have been found from this epoch. There is also a large body of evidence showing that dromaeosaurids were covered in feathers. Some dromaeosaurid fossils preserve long, pennaceous feathers on the hands and arms (remiges) and tail (rectrices), as well as shorter, down-like feathers covering the body. (Read more...)



Feathered dinosaurs is a term used to describe dinosaurs, particularly maniraptoran dromaeosaurs, that were covered in plumage; either filament-like intergumentary structures with few branches, to fully developed pennaceous feathers complete with shafts and vanes. Feathered dinosaurs first came to realization after it was discovered that dinosaurs are closely related to birds. Since then, the term "feathered dinosaurs" has widened to encompass the entire concept of the dinosaur–bird relationship, including the various avian characteristics some dinosaurs possess, including a pygostyle, a posteriorly oriented pelvis, elongated arms and forelimbs and clawed hand, and clavicles fused to form a furcula. A substantial amount of evidence demonstrates that birds are the descendants of theropod dinosaurs, and that birds evolved during the Jurassic from small, feathered maniraptoran theropods closely related to dromaeosaurids and troodontids (known collectively as deinonychosaurs). Less than two dozen species of dinosaurs have been discovered with direct fossil evidence of plumage since the 1990s, with most coming from Cretaceous deposits in China, most notably Liaoning Province. Together, these fossils represent an important transition between dinosaurs and birds, which allows paleontologists to piece together the origin and evolution of birds. (Read more...)



Nanotyrannus (meaning "small tyrant") is a problematic genus of tyrannosaurid dinosaur, and is possibly a juvenile specimen of Tyrannosaurus. Nanotyrannus is the smallest known tyrannosaurid and was one of the last tyrannosaurids to before the end-Cretaceous mass extinction, the K-T event. The genus is represented only by a small skull that was discovered by Charles W. Gilmore in 1942 and described in 1946 as a specimen of Gorgosaurus lancensis (now known as Albertosaurus). In 1988, the specimen was re-described by Robert T. Bakker, Phil Currie, and Michael Williams, the late curator of paleontology at the Cleveland Museum of Natural History, where the original specimen was housed and is currently on display. Opinions continue to remain divided on the validity of N. lancensis. Nanotyrannus can be a possible juvenile of a tyrannosaur that is closely related to Tyrannosaurus and the adult of this animal is yet to be identified, or it really is a juvenile Tyrannosaurus. In either case, an adult Nanotyrannus has to be discovered or a juvenile Tyrannosaurus of the same size as Nanotyrannus but morphologically distinct from it in order to fully resolve this debate. Many paleontologists consider the skull to belong to a juvenile Tyrannosaurus rex. (Read more...)



Spinosaurus (meaning "spine lizard") is a genus of theropod dinosaur which lived in what is now North Africa, sometime during the Albian and Cenomanian stages of the Cretaceous period, about 112 to 93.5 million years ago. This genus was first known from Egyptian remains discovered in the 1910s and described by German paleontologist Ernst Stromer. These original remains were destroyed in World War II, but additional skull material has come to light in recent years. It is unclear whether one or two species are represented in the described fossils. The best known species is S. aegyptiacus from Egypt, although a potential second species, S. marocannus, has been recovered from Morocco. The distinctive spines of Spinosaurus, which were long extensions of the vertebrae, grew up to 2 meters (7 ft) long and were likely to have had skin connecting them, forming a sail-like structure, although some authors have suggested that they were covered in muscle and formed a hump or ridge. Multiple functions have been put forward for this structure, including thermoregulation and display. According to recent estimates, Spinosaurus is the largest of all known carnivorous dinosaurs, even larger than Tyrannosaurus rex and Giganotosaurus. These estimates suggest that it was around 16 to 18 meters (52 to 59 ft) in length and 7 to 9 tonnes (7.7 to 9.9 short tons) in weight. (Read more...)



Titanoboa, meaning "titanic boa", is an extinct genus of snake that lived approximately 60 to 58 million years ago, during the Paleocene epoch, (approximately 60-58 million years ago) a 10-million-year period immediately following the Cretaceous–Tertiary extinction event that wiped out the majority of terrestrial life, including the dinosaurs. After the mass extinction event, Titanoboa was, for the majority of the Paleocene epoch, the largest non-marine vertebrate. It is the largest snake ever discovered at an estimated 43 feet long, and to date, paleontologists have identified about 180 different bones, mainly vertebrae and costae (rib bones) belonging to 28 individual specimens from a cache of fossils excavated from El Cerrejon coal mine in northern Colombia. The prepped fossils were later revealed in early 2007 at the University of Florida's Florida Museum of Natural History in Gainesville, Florida. However, this is not the first occurence of large snake fossils that have been discovered in South America before. An example would be Madtsoia bai, a huge constrictor known from fossils discovered in Argentina in the mid 1930s. This particular species was believed to be up to 12 meters long, huge by modern snake standards but still 20% smaller than Titanoboa. (Read more...)



Herrerasaurus (meaning "Herrera's lizard", after the name of the rancher who discovered the first fossil of the animal) was one of the earliest dinosaurs. All known specimens of this carnivore have been discovered in rocks of early Carnian age (late Triassic, around 228 million years ago) in northwestern Argentina. The type species, Herrerasaurus ischigualastensis, was described by Osvaldo Reig in 1963 and is the only species assigned to the genus. The names Ischisaurus and Frenguellisaurus are synonymous with Herrerasaurus. For many years, the classification of Herrerasaurus was unclear, as the animal was initially known from very fragmentary remains; it has been hypothesized to be a basal theropod, a basal sauropodomorph, a basal saurischian, or not a dinosaur at all. However, with the discovery of a mostly complete skeleton and skull in 1988, Herrerasaurus has been classified as either an early theropod or an early saurischian in at least five recent reviews of theropod evolution. Herrerasaurus is a medium-sized bipedal member of the Herrerasauridae, a group of similar animals which were among the earliest of the dinosaurian evolutionary radiation. (Read more...)



Hupehsuchia is an order of enigmatic diapsid marine reptiles belonging to the class Sauropsida. The order was short-lasting, with a temporal range restricted to the Spathian age of the late Olenekian, spanning only a few million years of the Early Triassic. The order gets its name from Hubei Province, China, from which many specimens have been found. Of the entire order, Nanchangosauridae is the only recognized family. Hupehsuchians display an unusual combination of characteristics with other derived marine reptiles, including mosasaurs and ichthyosaurs, including polydactyly, narrow skull, and vivipary. The order consists of two genera, Hupehsuchus and Nanchangosaurus, of which, the former is the type genus. Determining the exact classification and phylogeny of this group remains difficult, and may be attributed to the limited knowledge of the fossil record of diapsid reptiles in the Late Permian and Early Triassic, as well as the great amount of convergence exhibited by secondarily aquatic reptiles. (Read more...)

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