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Facts About the Cenozoic Era

The Cenozoic Era is easy to define: it’s the stretch of geologic time that kicked off with the Cretaceous/Tertiary Extinction, 65 million years ago, and continues down to the present day. Informally, the Cenozoic Era is often referred to as the “age of mammals,” since it was only after the dinosaurs went extinct that mammals had the chance to evolve into various open ecological niches and dominate terrestrial life on the planet. This characterization is somewhat unfair, however, since (non-dinosaur) reptiles, birds and fish also thrived during the Cenozoic!

Somewhat confusingly, the Cenozoic Era is divided into various “periods” and “epochs,” and scientists don’t always use the same terminology when describing their discoveries. (This situation stands in stark contrast to the preceding Mesozoic Era, which is neatly divided into the Triassic, Jurassic and Cretaceous periods.) Here’s an overview of the subdivisions of the Cenozoic Era; just click on the appropriate links to see more in-depth articles about the geography, climate and prehistoric life of that period or epoch.

The Periods and Epochs of the Cenozoic Era

The Paleogene period (65-23 million years ago) was the age when the mammals began their rise to dominance. The Paleogene comprises three separate epochs:

* The Paleocene epoch (65-56 million years ago) was fairly quiet in evolutionary terms. This is when the tiny mammals that survived the K/T Extinction first tasted their newfound freedom and began to tentatively explore new ecological niches.

* The Eocene epoch (56-34 million years ago) was the longest epoch of the Cenozoic Era. The Eocene witnessed a vast profusion of mammalian forms; this was when the first even- and odd-toed ungulates appeared on the planet, as well as the first recognizable primates.

* The Oligocene epoch (34-23 million years ago) is notable for its change in climate from the preceding Eocene, which opened up even more ecological niches for mammals. This was the epoch when certain mammals (and even some birds) began to evolve to respectable sizes.

The Neogene period (23-2.6 million years ago) witnessed the continuing evolution of mammals and other forms of life, many of them to enormous sizes. The Neogene comprises two epochs:

* The Miocene epoch (23-5 million years ago) takes up the lion’s share of the Neogene. Most of the mammals, birds and other animals that lived during this time would have been vaguely recognizable to human eyes, though often considerably bigger or stranger.

* The Pliocene epoch (5-2.6 million years ago), often confused with the ensuing Pleistocene, was the time when many mammals migrated into the territories that they continue to inhabit during the present day. Horses, primates, elephants, and other animal types continued to make evolutionary progress.

The Quaternary period (2.6 million years ago to the present) is, so far, the shortest of all the earth’s geologic periods. The Quaternary comprises two even shorter epochs:

* The Pleistocene epoch (2.6 million-12,000 years ago) is famous for its large megafauna mammals, such as the Woolly Mammoth and the Saber-Toothed Tiger, that died off at the end of the last Ice Age (thanks partly to predation by the earliest humans).

* The Holocene epoch (10,000 years ago-present) comprises pretty much all of modern human history. Unfortunately, this is also the epoch when many mammals, and other forms of life, have gone extinct due to the ecological changes wrought by human civilization.

Prehistoric Life During the Eocene Epoch

The Eocene epoch began 10 million years after the extinction of the dinosaurs, 65 million years ago, and continued for another 22 million years, up to 34 million years ago. As with the preceding Paleocene epoch, the Eocene was characterized by the continuing adaptation and spread of prehistoric mammals, which filled the ecological niches left open by the dinosaurs’ demise. The Eocene constitutes the middle part of the Paleogene period (65-23 million years ago), preceded by the Paleocene and succeeded by the Oligocene epoch (34-23 million years ago); all of these periods and epochs were part of the Cenozoic Era (65 million years ago to the present).

Climate and geography. The Eocene epoch picked up where the Paleocene left off, with a continuing rise in global temperatures to near-Mesozoic levels. The later part of the Eocene saw a pronounced cooling trend, probably related to decreasing levels of carbon dioxide in the atmosphere, which culminated in the re-formation of ice caps at both the north and south poles.

The earth’s continents continued to drift toward their present positions, having broken apart from the northern supercontinent Laurasia and the southern supercontinent Gondwana, though Australia and Antarctica were still connected. The Eocene epoch also witnessed the rise of North America’s western mountain ranges.

Terrestrial Life During the Eocene Epoch

Mammals. Perissodactyls (odd-toed ungulates, such as horses and tapirs) and artiodactyls (even-toed ungulates, such as deer and pigs) can all trace their ancestry back to the primitive mammalian genera of the Eocene epoch. Phenacodus, a small, generic-looking ancestor of hoofed mammals, lived during the early Eocene, while the late Eocene witnessed much bigger “thunder beasts” like Brontotherium and Embolotherium. Carnivorous predators evolved in synch with these plant-munching mammals: the early Eocene Mesonyx only weighed as much as a large dog, while the late Eocene Andrewsarchus was the largest terrestrial meat-eating mammal that ever lived. The first recognizable bats (such as Palaeochiropteryx), elephants (such as Phiomia), and primates (such as Eosimias) also evolved during the course of the Eocene epoch.

Birds. As is the case with mammals, many modern orders of birds can trace their roots to the Eocene epoch (even though birds as a whole evolved, perhaps more than once, during the Mesozoic Era). The most notable birds of the Eocene were giant penguins, as typified by the 100-pound Inkayacu of South America and the 200-pound Anthropornis of Australia. Another important Eocene bird was Presbyornis, a toddler-sized prehistoric duck.

Reptiles. Crocodiles (such as the weirdly hooved Pristichampsus), turtles (such as the big-eyed Puppigerus) and snakes (such as the 33-foot long Gigantophis) all continued to flourish during the Eocene epoch, many of them attaining substantial sizes as they filled the niches left open by their dinosaur relatives. Much tinier lizards, like the three-inch-long Cryptolacerta, were also a common sight (and food source for larger animals).

Marine Life During the Eocene Epoch

The Eocene epoch was when the first prehistoric whales left dry land and opted for a life in the sea, a trend that culminated in the middle Eocene Basilosaurus, which attained lengths of up to 60 feet and weighed in the neighborhood of 50 to 75 tons. Sharks continued to evolve as well, but few fossils are known from this epoch. In fact, the most common marine fossils of the Eocene epoch are of tiny fish, like Knightia and Enchodus, that plied the lakes and rivers of North America in vast schools.

Plant Life During the Eocene Epoch

The heat and humidity of the early Eocene epoch made it a heavenly time for dense jungles and rainforests, which stretched almost all the way to the North and South Poles (the coast of Antarctica was lined with tropical rainforests about 50 million years ago!) Later in the Eocene, global cooling produced a dramatic change: the jungles of the northern hemisphere gradually disappeared, to be replaced by deciduous forests that could better cope with seasonal temperature swings. One important development had only just begun: the earliest grasses evolved during the late Eocene epoch, but didn’t spread worldwide (providing sustenance for plains-roaming horses and ruminants) until millions of years later.

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”. It is derived from the Greek ἄλλος/allos(“different, other”) and σαῦρος/sauros (“lizard / generic reptile”). The first fossil remains that could definitively be ascribed to this genus were described in 1877 by paleontologist Othniel Charles Marsh. These remains became known as Antrodemus. As one of the first well-known theropod dinosaurs, it has long attracted attention outside of paleontological circles. Indeed, it has been a top feature in several films and documentaries about prehistoric life.

Allosaurus was a large bipedal predator. Its skull was large and equipped with dozens of sharp, serrated teeth. It averaged 8.5 m (28 ft) in length, though fragmentary remains suggest it could have reached over 12 m (39 ft). Relative to the large and powerful hindlimbs, its three-fingered forelimbs were small, and the body was balanced by a long and heavily muscled 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.

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, 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 jaw like a hatchet.

Description

Allosaurus was a typical large theropod, having a massive skull on a short neck, a long tail and reduced forelimbs. Allosaurus fragilis, the best-known species, had an average length of 8.5 m (28 ft), with the largest definitive Allosaurus specimen (AMNH 680) estimated at 9.7 meters (32 feet) long, and an estimated weight of 2.3 metric tons (2.5 short tons). In his 1976 monograph on Allosaurus, James Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of 12 to 13 m (39 to 43 ft). As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between 1,500 kilograms (3,300 pounds), 1,000 to 4,000 kg (2,200 to 8,800 lb), and 1,010 kilograms (2,230 pounds) for modal adult weight (not maximum). John Foster, a specialist on the Morrison Formation, suggests that 1,000 kg (2,200 lb) is reasonable for large adults of A. fragilis, but that 700 kg (1,500 lb) is a closer estimate for individuals represented by the average-sized thigh bones he has measured. Using the subadult specimen nicknamed “Big Al”, researchers using computer modelling arrived at a best estimate of 1,500 kilograms (3,300 lb) for the individual, but by varying parameters they found a range from approximately 1,400 kilograms (3,100 lb) to approximately 2,000 kilograms (4,400 lb).

Several gigantic specimens have been attributed to Allosaurus, but may in fact belong to other genera. The closely related genus Saurophaganax (OMNH 1708) reached perhaps 10.9 m (36 ft) in length, and its single species has sometimes been included in the genus Allosaurus as Allosaurus maximus, though recent studies support it as a separate genus. Another potential specimen of Allosaurus, once assigned to the genus Epanterias (AMNH 5767), may have measured 12.1 meters (40 feet) in length. A more recent discovery is a partial skeleton from the Peterson Quarry in Morrison rocks of New Mexico; this large allosaurid may be another individual of Saurophaganax.

Skull

Allosauridae is one of four families in Carnosauria; the other three are Neovenatoridae, Carcharodontosauridae and Sinraptoridae. Allosauridae has at times been proposed as ancestral to the Tyrannosauridae (which would make it paraphyletic), one recent example being Gregory S. Paul’s Predatory Dinosaurs of the World, but this has been rejected, with tyrannosaurids identified as members of a separate branch of theropods, the Coelurosauria. Allosauridae is the smallest of the carnosaur families, with only Saurophaganax and a currently unnamed French allosauroid accepted as possible valid genera besides Allosaurus in the most recent review. Another genus, Epanterias, is a potential valid member, but it and Saurophaganax may turn out to be large examples of Allosaurus. Recent reviews have kept the genus Saurophaganax and included Epanterias with Allosaurus.

Species and taxonomy

There are currently four valid and one undescribed species of Allosaurus (A. amplus, A. europaeus, the type species A. fragilis, the as-yet not formally described “A. jimmadseni”, and A. lucasi).

A. fragilis, “A. jimmadseni”, A. amplus, and A. lucasi are all known from remains discovered in the Kimmeridgian–Tithonian Upper Jurassic-age Morrison Formation of the United States, spread across the states of Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, and Wyoming. A. fragilis is regarded as the most common, known from the remains of at least sixty individuals. For a while in the late 1980s and early 1990s it was common to recognize A. fragilis as the short-snouted species, with the long-snouted taxon being A. atrox; however, subsequent analysis of specimens from the Cleveland-Lloyd Quarry, Como Bluff, and Dry Mesa Quarry showed that the differences seen in the Morrison Formation material could be attributed to individual variation. A study of skull elements from the Cleveland-Lloyd site found wide variation between individuals, calling into question previous species-level distinctions based on such features as the shape of the lacrimal horns, and the proposed differentiation of “A. jimmadseni” based on the shape of the jugal. A. europaeus was found in the Kimmeridgian-age Porto Novo Member of the Lourinhã Formation, but may be the same as A. fragilis.

Allosaurus tendagurensis was found in Kimmeridgian-age rocks of Tendaguru, in Mtwara, Tanzania. Subsequent studies classified it as a non-coelurosaurian tetanuran, either a megalosaurid or carcharodontosaur. Although obscure, it was a large theropod, possibly around 10 meters (33 feet) long and 2.5 metric tons (2.8 short tons) in weight.

Anchisaurus is a genus of basal sauropodomorph. An early herbivorous dinosaur, it lived during the Early Jurassic period; more specifically, the Pliensbachian to Toarcian ages, 190 to 174 million years ago. Until recently it was classed as a member of Prosauropoda. The name comes from the Greek αγχι/agkhi anchi-; “near, close” + Greek σαυρος/sauros; “lizard”. Anchisaurus was coined as a replacement name for Amphisaurus, which was itself a replacement name for Hitchcock’s Megadactylus, both of which had already been used for other animals.

Anchisaurus was a rather small dinosaur, with a length of just over 2 metres (6.6 ft), which helps explain why it was once mistaken for human bones. It probably weighed around 27 kilograms (60 lb). However, Marsh’s species A. major (also known as Ammosaurus) was larger, from 2.5 to 4 metres (8 ft 2 in to 13 ft 1 in) and some estimates give it a weight of up to 70 pounds (32 kg). Gregory S. Paul estimated its length at 2.2 meters and its weight at 20 kg in 2010.

Sauropodomorph remains were first discovered in North America in 1818, when some large bones were uncovered by Mr. Solomon Ellsworth Jr while with gunpowder excavating a well in East Windsor, Connecticut. At the time of their discovery it was thought that the bones might be those of a human, but the presence of tail vertebrae in 1821 falsified that idea. They are now recognized as those of an indeterminate sauropodomorph, possibly more closely related to the plateosaurian prosauropods.

Due to its primitive appearance, Anchisaurus was previously classified as a prosauropod, a member of a group of animals related to or ancestral to the sauropods. Recent investigations show that a group of traditional prosauropods form a monophyletic sister-group to Sauropoda, and that Anchisaurus is instead closer to sauropods.

The family Anchisauridae was first proposed by Othniel Charles Marsh in 1885 and later defined as a clade consisting of Anchisaurus and its nearest relatives. However, it is not clear which other genera are included in the family; many of the dinosaurs once included have since been moved elsewhere, and the group is not used in most current taxonomies.

Atlascopcosaurus (meaning “Atlas Copco lizard”) is a genus of herbivorous basal euornithopod dinosaur from the Early Cretaceous of the present Australia.

The type specimen, NMV P166409, was found in 1984 at the Dinosaur Cove East site at the coast of Victoria, in layers of the Eumeralla Formation dating from the early Cretaceous, Aptian-Albian. This holotype consists of a piece of the upper jaw, a partial maxilla with teeth. Nothing else is known about it; as the rest of the skeleton remains undiscovered it can only be inferred from closely related species that the genus represents a small bipedal herbivore. By extrapolation it has been estimated that it was about two to three metres (6.5–10 ft) long and weighed appoximately 125 kg. Because the teeth are not species-specific and the maxilla fragment is little informative, the taxon is today commonly seen as a nomen dubium.

The type species, Atlascopcosaurus loadsi, was named and described by Tom Rich and Patricia Vickers-Rich in 1988/1989. The generic name refers to the Atlas Copco Company who had provided equipment for the dig that discovered this dinosaur in 1984. The project revealed 85 fossil bone fragments of various species. This opened the door for more excavation and, along with other companies, Atlas Copco helped over ten years excavate about sixty metres of tunnel in a cliff wall at the sea shore. The specific name, loadsi, honours William Loads, the state manager for Atlas Copco at the time, who assisted during the dig.

Atlascopcosaurus was in 1988 assigned to the Hypsilophodontidae. These are today seen as an unnatural (paraphyletic) group and Atlascopcosaurus is now simply considered a basal member of the Ornithopoda.

Ankylosaurus is a genus of armored dinosaur. Fossils of Ankylosaurus have been found in geological formations dating to the very end of the Cretaceous Period, between about 68–66 million years ago, in western North America, making it among the last of the non-avian dinosaurs. It was named by Barnum Brown in 1908, and the only species classified in the genus is A. magniventris. The genus name means “fused lizard” and the specific name means “great belly”. A handful of specimens have been excavated to date, but a complete skeleton has not been discovered. Though other members of Ankylosauria are represented by more extensive fossil material, Ankylosaurus is often considered the archetypal member of its group.

The largest known ankylosaurid, Ankylosaurus measured up to 6.25 m (20.5 feet) in length, 1.7 m (5.6 feet) in height, and weighed 6 tonnes (13,000 lb). It was a quadrupedal animal, with a broad, robust body. It had a wide, low skull, with two horns pointing backwards from the back of the head, and two horns below these that pointed backwards and down. The front part of the jaws were covered in a beak, with rows of small, leaf-shaped teeth further behind it. It was covered in armor plates, or osteoderms, with bony half-rings covering the neck, and had a large club on the end of its tail. Bones in the skull and other parts of the body were fused, increasing their strength, and this feature is the source of the genus name.

Ankylosaurus is a member of the family Ankylosauridae, and its closest relatives appear to be Anodontosaurus and Euoplocephalus. Ankylosaurus is thought to have been a slow moving animal, able to make quick movements when necessary. Its broad muzzle indicates it was a non-selective browser. Sinuses and nasal chambers in the snout may have been for heat and water balance or played a role in vocalization. The tail club is thought to have been used in defense against predators or in intraspecific combat. Ankylosaurus has been found in the Hell Creek, Lance, and Scollard formations, but appears to have been rare in its environment. Although it lived alongside a nodosaurid ankylosaur, their ranges and ecological niches do not appear to have overlapped, and Ankylosaurus may have inhabited upland areas. Ankylosaurus also lived alongside dinosaurs such as Tyrannosaurus, Triceratops, and Edmontosaurus.

Description

Ankylosaurus is the largest known ankylosaurid dinosaur, estimated to have been up to 6.25 m (20.5 feet) long, 1.5 m (4.9 feet) wide, and 1.7 m (5.6 feet) tall at the hip. This length has been proposed by American palaeontologist Kenneth Carpenter, and is based on the largest known skull (specimen NMC 8880), which is 64.5 cm (25.4 inches) long and 74.5 cm (29.3 inches) wide. The smallest known skull (specimen AMNH 5214) is 55.5 cm (21.9 inches) long and 64.5 cm (25.4 inches) wide, and this specimen is estimated to have been 5.4 m (17.7 feet) long and around 1.4 m (4.6 feet) tall. Other authors have proposed a body length of 7 m (23 feet), 8–9 m (26.2–29.5 ft), or more than 9 m (29.5 feet). The weight of the animal has been estimated at 6 tonnes (13,000 lb).

The structure of much of the skeleton of Ankylosaurus, including most of the pelvis, tail and feet, is still unknown. It was quadrupedal, and its hind limbs were longer than the forelimbs. The scapula (shoulder blade) and coracoid (a rectangular bone connected to the lower end of the scapula) of specimen AMNH 5895 were fused, and had entheses (connective tissue) for various muscle attachments. The scapula was 61.5 cm (24.2 inches) long. The humerus (upper arm bone) was short and very broad, and about 54 cm (21 inches) long in specimen AMNH 5214. The femur (thigh bone) was very robust, and 67 cm (26 inches) long in AMNH 5214. While the feet of Ankylosaurus are incompletely known, the hindfeet probably had three toes, as is the case in related animals.

Skull

The three known Ankylosaurus skulls differ in various details, but this is thought to be the result of taphonomy (changes happening during fossilisation of the remains) and individual variation. The skull was low and triangular in shape, wider than it was long. It had a broad beak on the premaxillae. The orbits (eye sockets) were almost round to slightly oval and did not face directly sideways, because the skull tapered towards the front. Crests above the orbits merged into the upper squamosal horns (their shape has been described as “pyramidal”), which pointed backwards to the sides from the back of the skull. The crest and horn were probably separate elements originally, as seen in the related Pinacosaurus and Euoplocephalus. Below the upper horns, jugal horns were present, which pointed backwards and down. The horns may have originally been osteoderms (armor plates) that fused to the skull. However, the scale pattern on the skull surface was instead the result of remodelling of the skull. This obliterated the sutures between skull elements, which is common for adult ankylosaurs. The scale pattern of the skull was variable between specimens, though some details are shared; it had a diamond-shaped scale (internarial scale) at the font of the snout, two squamosal osteoderms above the orbit, and a ridge of scales at the back of the skull.

Armor

 A prominent feature of Ankylosaurus was its armor, consisting of knobs and plates of bone known as osteoderms or scutes embedded in the skin. These have not been found in articulation, so their exact placement on the body is unknown, though inferences can be made based on related animals. The osteoderms ranged from 1 cm (0.4 inches) in diameter to 35.5 cm (14.0 inches) in length, and also varied in shape. The osteoderms of Ankylosaurus were generally thin walled and hollowed on the underside. Compared to Euoplocephalus, the osteoderms of Ankylosaurus were smoother in texture. The osteoderms covering the body were very flat, though with a low keel at one margin. In contrast, the nodosaurid Edmontonia had high keels, stretching from one margin to the other on the midline of its osteoderms. Ankylosaurus had some smaller osteoderms with a keel across the midline. Some osteoderms without keels may have been placed above the hip region, as in Euoplocephalus. Flattened, pointed plates resemble those on the sides of the tail of Saichania. Osteoderms with oval keels could have been placed on the upper side of the tail or the side of the limbs. Small osteoderms and ossicles likely occupied the space between the larger ones.

Since Ankylosaurus and other Late Cretaceous North American ankylosaurids grouped with Asian genera (in a tribe the authors named Ankylosaurini), Arbour and Currie suggested that earlier North American ankylosaurids had gone extinct by the late Albian or Cenomanian ages of the Middle Cretaceous. Ankylosaurids thereafter recolonised North America from Asia during the Campanian or Turonian ages of the Late Cretaceous, and diversified there again, leading to genera such as Ankylosaurus, Anodontosaurus, and Euoplocephalus. This explains a 30 million year gap in the fossil record of North American ankylosaurids between these ages.

Palaeoecology

Ankylosaurus existed between 68 and 66 million years ago, in the final, or Maastrichtian, stage of the Late Cretaceous Period. It was among the last dinosaur genera that appeared before the Cretaceous–Paleogene extinction event. The type specimen is from the Hell Creek Formation of Montana, while other specimens have been found in the Lance Formation of Wyoming and the Scollard Formation in Alberta, Canada, all of which date to the end of the Cretaceous. Fossils of Ankylosaurus are rare in these sediments, and the distribution of its remains suggest that it was restricted to the uplands of the formations, rather than the coastal lowlands. Another ankylosaur, an indeterminate nodosaur (formerly referred to as Edmontonia sp.), is also found in the same formations, but the range of the two genera does not seem to have overlapped. Their remains have so far not been found in the same localities, and the nodosaur appears to have inhabited the lowlands. The narrow muzzle of the nodosaur suggests it had a more selective diet than Ankylosaurus, further indicating ecological separation.

The Hell Creek, Lance and Scollard Formations represent different sections of the western shore of the Western Interior Seaway that divided western and eastern North America during the Cretaceous. They represent a broad coastal plain, extending westward from the seaway to the newly formed Rocky Mountains. These formations are composed largely of sandstone and mudstone, which have been attributed to floodplain environments. The regions where Ankylosaurus and other Late Cretaceous ankylosaurs have been found had a warm subtropical/temperate climate, which was monsoonal, had occasional rainfall, tropical storms, and forest fires. In the Hell Creek Formation, many types of plants were supported, primarily angiosperms, with less common conifers, ferns and cycads. An abundance of fossil leaves found at dozens of different sites indicates that the area was largely forested by small trees. Ankylosaurus shared its environment with dinosaurs including the ceratopsids Triceratops and Torosaurus, the hypsilophodont Thescelosaurus, the hadrosaurid Edmontosaurus, an indeterminate nodosaur, the pachycephalosaurian Pachycephalosaurus, and the theropods Struthiomimus, Ornithomimus, Troodon, and Tyrannosaurus.

Apatosaurus is a genus of sauropod dinosaurs that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, A. ajax in 1877, and a second species, A. louisae, was discovered and named by William H. Holland in 1916. They lived about 152 to 151 million years ago (mya), during the early Tithonian age, and are now known from fossils in the Morrison Formation of modern-day Colorado, Oklahoma, and Utah, in the United States. Apatosaurus had an average length of 21–22.8 m (69–75 ft), and an average mass of 16.4–22.4 t (16.1–22.0 long tons; 18.1–24.7 short tons). A few specimens indicate a maximum length of 11–30% greater than average and a mass of 32.7–72.6 t (32.2–71.5 long tons; 36.0–80.0 short tons).

The cervical vertebrae of Apatosaurus are less elongated and more heavily constructed than those of Diplodocus, a diplodocid like Apatosaurus, and the bones of the leg are much stockier despite being longer, implying that Apatosaurus was a more robust animal. The tail was held above the ground during normal locomotion. Apatosaurus had a single claw on each forelimb and three on each hindlimb. The skull of Apatosaurus, long thought to be similar to Camarasaurus, is much more similar to that of Diplodocus. Apatosaurus was a generalized browser that likely held its head elevated. To lighten its vertebrae, Apatosaurus had air sacs that made the bones internally full of holes. Like that of other diplodocids, its tail may have been used as a whip to create loud noises.

The skull of Apatosaurus was confused with that of Camarasaurus and Brachiosaurus until 1909, when the holotype of A. louisae was found, and a complete skull just a few meters away from the front of the neck. Henry Fairfield Osborn disagreed with this association, and went on to mount a skeleton of Apatosaurus with a Camarasaurus skull cast. Until 1970, Apatosaurusskeletons were mounted with speculative skull casts, when McIntosh showed that more robust skulls assigned to Diplodocuswere more likely from Apatosaurus.

Apatosaurus is a genus in the family Diplodocidae. It is one of the more basal genera, with only Amphicoelias, and possibly a new, unnamed genus more primitive. While the subfamily Apatosaurinae was named in 1929, the group was not used validly until an extensive 2015 study. Only Brontosaurus is also in the subfamily, with the other genera being considered as synonyms or reclassified as diplodocines. Brontosaurus has long been considered a junior synonym of Apatosaurus; its only species was reclassified as A. excelsus in 1903. However, the 2015 study concluded that Brontosaurus was a valid genus of sauropod distinct from Apatosaurus. Nevertheless, not all paleontologists agree with this division. As it existed in North America during the late Jurassic, Apatosaurus would have lived aside dinosaurs such as Allosaurus, Camarasaurus, Diplodocus, and Stegosaurus.

Archaeopteryx, sometimes referred to by its German name Urvogel (“original bird” or “first bird”), is a genus of bird-like dinosaurs that is transitional between non-avian feathered dinosaurs and modern birds. The name derives from the ancient Greek ἀρχαῖος (archaīos) meaning “ancient”, and πτέρυξ (ptéryx), meaning “feather” or “wing”. Between the late nineteenth century and the early twenty-first century, Archaeopteryx had been generally accepted by palaeontologists and popular reference books as the oldest known bird (member of the group Avialae). Older potential avialans have since been identified, including Anchiornis, Xiaotingia, and Aurornis.

Archaeopteryx lived in the Late Jurassic around 150 million years ago, in what is now southern Germany during a time when Europe was an archipelago of islands in a shallow warm tropical sea, much closer to the equator than it is now. Similar in size to a Eurasian magpie, with the largest individuals possibly attaining the size of a raven, the largest species of Archaeopteryx could grow to about 0.5 m (1 ft 8 in) in length. Despite their small size, broad wings, and inferred ability to fly or glide, Archaeopteryx had more in common with other small Mesozoic dinosaurs than with modern birds. In particular, they shared the following features with the dromaeosaurids and troodontids: jaws with sharp teeth, three fingers with claws, a long bony tail, hyperextensible second toes (“killing claw”), feathers (which also suggest warm-bloodedness), and various features of the skeleton.

These features make Archaeopteryx a clear candidate for a transitional fossil between non-avian dinosaurs and birds. Thus, Archaeopteryx plays an important role, not only in the study of the origin of birds, but in the study of dinosaurs. It was named from a single feather in 1861. That same year, the first complete specimen of Archaeopteryx was announced. Over the years, ten more fossils of Archaeopteryx have surfaced. Despite variation among these fossils, most experts regard all the remains that have been discovered as belonging to a single species, although this is still debated.

Most of these eleven fossils include impressions of feathers. Because these feathers are of an advanced form (flight feathers), these fossils are evidence that the evolution of feathers began before the Late Jurassic. The type specimen of Archaeopteryx was discovered just two years after Charles Darwin published On the Origin of Species. Archaeopteryx seemed to confirm Darwin’s theories and has since become a key piece of evidence for the origin of birds, the transitional fossils debate, and confirmation of evolution.

Description

Avimimus, meaning “bird mimic” (Latin avis = bird + mimus = mimic), was a genus of oviraptorosaurian theropod dinosaur, named for its bird-like characteristics, that lived in the late Cretaceous in what is now Mongolia, around 70 million years ago.

As its name clearly suggests Avimimus was a very birdlike dinosaur. It was a lightly built, long-legged animal that may have made its living by chasing after small reptiles and mammals. Avimimus’s diet is still a subject of debate; some scientists believe that it probably fed mainly on insects. It was capable of swift speeds, which would have both enhanced its efficiency as a predator and helped it to avoid falling prey to larger meat-eating dinosaurs.

Avimimus was a strange-looking dinosaur. It had a long neck and a short head with a tooth-less mouth. It had a large braincase, which suggests that its brain, too, was relatively large. In place of teeth it had a powerful beak, similar to that of a present-day cockatoo. The bones of its wrist were fused together as they are in birds and the three long fingers could be held tucked under the body. In fact, Avimimus could fold its whole arm against its body in a similar fashion to the way a bird folds its wing.

Its long legs ended in three toes, with a smaller fourth toe nestled on the inside of the foot. All the toes and fingers were tipped with sharp, curved claws. Unlike a bird, however, Avimimus had a long, bony tail and its pelvis resembled those that are seen in other theropods. It is possible that Avimimus had feathers of some kind, but the deposits in which it has been discovered are too coarse for such features to have been preserved. However, a rough ridge on the forearm of Avimimus – similar to the one on Caudipteryx, which supported a half-wing – may well have served to anchor feathers. However, even if Avimimus did have feathers, it seems unlikely that it would have been capable of flight.

We have known about Avimimus for only a relatively short time. Russian expeditions into Mongolia in the late 1970s and early 1980s were the first to discover fossils of it, and it was described and named only as recently as 1981. Since then, Chinese paleontologists have unearthed other fossils, but remains of Avimimus are still very rare. Only three partial skeletons – and no complete skeletons – have so far been discovered.

What is a Paleontologist?

Paleontology is the science dealing with the fossils of long-deceased animals and plants that lived up to billions of years ago. It’s an interdisciplinary field involving geology, archaeology, chemistry, biology, archaeology and anthropology.

A paleontologist studies the history and process of evolution by examining fossils, the preserved traces of long dead animals and plants. Using data from fossilized bones, ancient pollen, and other clues, paleontologists dig up the details on past climates and past extinctions. They tell us about the history of the earth, the evolution of life, and our own place in the world.

What Does a Paleontologist Do?

Paleontologists plan, direct, and conduct fieldwork projects to search for fossils or collect samples. They document the work site and dig up fossils or take core samples from lakes, soil, or ice sheets. They then need to preserve the specimens and prepare them for transport to the institution where they’ll be cleaned and studied. Some work in laboratories, using chemical techniques to analyze fossilized samples and ancient pollen. They share their research by writing journal articles and presenting to colleagues at professional conferences. Most need to write applications for grants to support their research. Many teach and conduct research as faculty members at colleges and universities.

Paleontologists usually specialize in a particular research area. For example, micropaleontologists study microscopic fossils. Paleobotanistsconduct research on fossil plants, including algae and fungi. Palynologists study pollen and spores. Invertebrate paleontologists study fossils of invertebrate animals like mollusks and worms. Vertebrate paleontologists focus on the fossils of vertebrate animals, including fish. Human paleontologists or paleoanthropologists focus on the fossils of prehistoric humans and pre-human hominids. Taphonomists study the process that creates fossils. Ichnologists hunt for fossil tracks, trails, and footprints, such as the dinosaur tracks found in Arkansas in 2011. Paleoecologists use fossils, spores, pollen, and other information to study the ecologies and climates of the past.

The revelations they uncover can help us understand the past, so that we don’t repeat it. They can also provide context for comparison between the current state of our environment and biodiversity, and those of ancient and turbulent epochs.

Where Does a Paleontologist Work?

Most paleontologists are faculty members in the geology departments of colleges and universities. Some work in museums. A handful are employed by government geological surveys, where they make geological maps or investigate geological issues. A few help oil companies search for petroleum.

Paleontologists spend most of their time in offices while teaching, writing, or analyzing their finds. However, some conduct research in laboratories. When conducting fieldwork, paleontologists work outdoors, where they do rigorous physical work in all kinds of weather.

What Is the Average Paleontologist Salary?

Indeed listed the average annual salary of paleontologists as $64,000 in January 2015.

Table data taken from BLS (http://www.bls.gov/oes/current/oes192042.htm)

Paleontology Jobs & Job Description

Paleontologist jobs deal primarily with the study of animal and plant fossils from various eras of earth’s prehistory. While jobs vary significantly, most paleontologists would call the below list of tasks a basic outline of their scope of work:

• Develop data collection methods and systems tailored to a particular era, site or project goal
• Collect information from observations, satellite, GIS/GPS and concussive instruments
• Record and manage records of observations
• Analyze field data, laboratory samples, and other sources of information to uncover patterns about prehistoric life and origins
• Prepare reports and present research findings
• Communicate with project leads, administrators and other staff through regular, scheduled field status reports and presentation of research findings
• Engage in field survey, testing, monitoring, and data recovery
• Advise organizations on the possible impact of policies, programs, and products

A lead paleontologist, chief researcher, or project manager may have the following or similar additional responsibilities, depending on the project and its goals:

• Foster a positive and safe work environment
• Develop and inform project scopes, schedules, and budgets
• Navigate federal and international protocols, regulations, and best practices
• Test and calibrate equipment and instruments
• Ensure quality assurance, organization, and appropriate tracking of field data
• Oversee the preservation of site integrity
• Engage in office-based tasks including technical report preparation and submittal, as well as liaising with site stakeholders
• Supervise fieldwork (survey, site recording, testing, monitoring, and data integrity) of multiple field crews
• Communicate with funding agencies through grant applications
• Communicate with stakeholders through field status reports and presentation of team findings

What Is the Job Demand for Paleontologists?

While the government projects that employment of geoscientists as a whole will grow quickly, the outlook for paleontologists specifically is more conservative. The Paleontological Research Institution notes that there are fewer jobs in this area in the U.S. than there were a few years ago, but a few good jobs still become available each year.

How Do I Get a Paleontology Degree?

A Ph.D. is usually necessary for paleontological careers, particularly in academia. Aspiring paleontologists should have extensive knowledge of biology and geology. A double-major with full training in both is the best educational option. Chemistry, physics, calculus, statistics, and computer science are also very important. Undergraduate geology classes typically include mineralogy, stratigraphy, sedimentary petrology, vertebrate and invertebrate paleontology, ecology, evolutionary biology, and genetics.

Field and lab experience are also vital. Paleontologists will need to know professional standards and procedures for surveying work sites and unearthing their finds. Look for volunteer opportunities at nearby museums, or join a mineral or fossil club at your university.

What Kind of Societies and Professional Organizations Do Paleontologists Have?

• The Palaeontological Association publishes academic journals, newsletters and field guides, sponsors an annual meeting and field excursions, provides Web resources, and funds grants and awards. It also hosts career information.

• The International Palaeontological Association aims to coordinate international cooperation among paleontologists, and to integrate the various sub-disciplines of the field. It also organizes international meetings, issues a world directory of paleontologists, and publishes Lethaia, a leading paleontological academic journal.

• Founded in 1940, The Society of Vertebrate Paleontology provides a global forum for vertebrate paleontologists through publications, annual meetings, and an email list. It accepts a wide variety of professionals, including science artists and writers.

Source: https://www.nationalgeographic.org