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66-685: Anchisaurus is a genus of basal sauropodomorph dinosaur . It lived during the Early Jurassic Period , and its fossils have been found in the red sandstone of the Upper Portland Formation , Northeastern United States , which was deposited from the Hettangian age into the Sinemurian age, between about 200 and 192 million years ago. Until recently it was classed as a member of Prosauropoda . The genus name Anchisaurus comes from

132-596: A facultative biped , Anchisaurus had to have multi-purpose front legs. As 'hands', they could be turned inwards and be used for grasping. It had a simple reversible first 'finger', similar to a 'thumb'. As feet, the five toes could be placed flat against the floor and were strong at the ankle. This unspecialized design is typical of the early dinosaurs. [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Basal (phylogenetics) While there must always be two or more equally "basal" clades sprouting from

198-399: A block had been removed containing the hind part of a skeleton. He warned Marsh who, using T. A. Bostwick as an intermediary, acquired the piece from the quarry owner, Charles O. Wolcott. Marsh tried to secure the front half of the skeleton but it had already been used in a bridge abutment. The specimen, YPM 208, was named Anchisaurus major , "the larger one", by Marsh in 1889. Eventually, when

264-409: A correlation does not make a given case predicable, so ancestral characters should not be imputed to the members of a less species-rich basal clade without additional evidence. In general, clade A is more basal than clade B if B is a subgroup of the sister group of A or of A itself. In the context of large groups, the term "basal" is often used loosely to refer to positions closer to

330-698: A mix of archaic and apomorphic (derived) features that have only been sorted out via comparison with other angiosperms and their positions within the phylogenetic tree (the fossil record could potentially also be helpful in this respect, but is absent in this case). The cladogram below is based on Ramírez-Barahona et al. (2020), with species counts taken from the source indicated. Amborellales (1 species) Nymphaeales (about 90 species) Austrobaileyales (about 95 species) Magnoliids (about 9,000 species) Chloranthales (about 80 species) Monocots (about 70,000 species) Ceratophyllales (about 6 species) Eudicots (about 175,000 species) Within

396-400: A physician like his father. However, an elective course in geology and George Gaylord Simpson 's book The Meaning of Evolution inspired him to change his career plans. He earned his bachelor's degree in biology and geology from Union College in 1951. Ostrom enrolled at Columbia University as a graduate student with Ned Colbert as his advisor. In 1951 Simpson invited Ostrom to spend

462-405: A separate genus, Ammosaurus , the "sand saurian". In the same publication he named YPM 1883/YPM 40313 as a new species of Anchisaurus , Anchisaurus colurus , "the mangled one". They served as the templates from which O. C. Marsh in 1893 restored the skeleton. The Manchester specimens are now considered conspecific with Anchisaurus polyzelus . The East Windsor and Manchester specimens are housed at

528-645: A shopping mall was built on the site of the Charles O. Wolcott Quarry in 2000. Ostrom officially retired from Yale in 1992, but continued to write and research as a professor emeritus until his health failed. Ostrom died from complications of Alzheimer's disease in July 2005 at the age of 77 in Litchfield, Connecticut . In the field of paleontology, Ostrom is responsible for the following key discoveries: Ostrom's work first achieved international attention with his studies of

594-468: A sister group to Homininae and are the basal genus in the great ape family Hominidae as a whole. Orangutans ( Pongo spp.) Humans ( Homo sapiens ) Chimpanzees ( Pan spp.) Gorillas ( Gorilla spp.) Subfamilies Homininae and Ponginae are both basal within Hominidae, but given that there are no nonbasal subfamilies in the cladogram it is unlikely the term would be applied to either. In general,

660-405: A statement to the effect that one group (e.g., orangutans) is basal, or branches off first, within another group (e.g., Hominidae) may not make sense unless the appropriate taxonomic level(s) (genus, in this case) is specified. If that level cannot be specified (i.e., if the clade in question is unranked) a more detailed description of the relevant sister groups may be needed. As can be seen, the term

726-402: A subsequent paper that hadrosaurs had need for such an acute sense of smell as a defense against larger carnivorous dinosaurs, of which the hadrosaur body plan had little in the way of armor and speed. This hypothesis led Ostrom to further conclude that ecology of hadrosaurs was more likely to be that of dry ground such as conifer forests, rather than swampy, aquatic environments, thought to be

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792-461: A trait generally viewed as ancestral among the apes. Given that the deepest phylogenetic split in a group is likely to have occurred early in its history, identification of the most basal subclade(s) in a widely dispersed taxon or clade can provide valuable insight into its region of origin; however, the lack of additional species in a clade is not evidence that it carries the ancestral state for most traits. Most deceptively, people often believe that

858-470: A well with gunpowder 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 falsified that idea. They are now recognized as those of an indeterminate sauropodomorph, possibly more closely related to the plateosaurian prosauropods. In 1855, the original type specimen of Anchisaurus polyzelus , AM 41/109, which

924-553: Is a basal clade of extant angiosperms , consisting of the most species, genus, family and order within the group that are sister to all other angiosperms (out of a total of about 250,000 angiosperm species). The traits of Amborella trichopoda are regarded as providing significant insight into the evolution of flowering plants; for example, it has "the most primitive wood (consisting only of tracheids ), of any living angiosperm" as well as "simple, separate flower parts of indefinite numbers, and unsealed carpels". However, those traits are

990-422: Is a much more intensive biochemical process than digesting meat. This herbivore swallowed gastroliths (gizzard stones) to help break down the food in its stomach. Herbivorous dinosaurs needed a huge gut . Since this had to be positioned in front of the pelvis, balancing on two legs became increasingly difficult, as dinosaurs became larger and they gradually evolved into the quadrupedal position that characterizes

1056-506: Is credited with triggering the " dinosaur renaissance ", a term coined in a 1975 issue of Scientific American by Bakker to describe increased interest in paleontology. The "dinosaur renaissance" continues, with scientists describing new species of dinosaurs every year and expanding the understanding of dinosaur biology. Due in large part to his earlier research on hadrosaurs—and his conclusion that they were likely upright, terrestrial animals rather than sluggish, swamp-bound lizards—Ostrom

1122-639: Is housed at the Amherst College Museum of Natural History , was found by William Smith in Springfield, Massachusetts during blasting a well for the waterhouse at the Springfield Armory . Unfortunately, both the East Windsor and Springfield specimens were severely damaged due to the blasting at the construction sites where they were found, and many of the bones were either accidentally thrown away by

1188-415: Is likely a source of the mis-use of the term. Other famous examples of this phenomenon are the oviparous reproduction and nipple-less lactation of monotremes , a clade of mammals with just five species, and the archaic anatomy of the tuatara , a basal clade of lepidosaurian with a single species. The flowering plant family Amborellaceae , restricted to New Caledonia in the southwestern Pacific,

1254-515: Is not reflective of ancestral states or proximity to the common ancestor of extant species. In this example, orangutans differ from the other genera in their Asian range. This fact plus their basal status provides a hint that the most recent common ancestor of extant great apes may have been Eurasian (see below), a suggestion that is consistent with other evidence. (Of course, lesser apes are entirely Asiatic.) However, orangutans also differ from African apes in their more highly arboreal lifestyle,

1320-484: Is probably a juvenile of Massospondylus carinatus . G. sinensis was also referred here, but appears to be a distinct animal. The Navajo Sandstone of Arizona is the same age as the Portland Formation, and has produced prosauropod remains that have been referred to as Ammosaurus . However, it is possible that these actually belong to the genus Massospondylus , otherwise known only from South Africa. In

1386-418: Is unnecessary and misleading. The term is more often applied when one branch (the one deemed "basal") is less diverse than another branch (this being the situation in which one would expect to find a basal taxon of lower minimum rank). The term may be equivocal in that it also refers to the direction of the root of the tree, which represents a hypothetical ancestor; this consequently may inaccurately imply that

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1452-796: The Cloverly Formation Site in Montana and Wyoming from 1962 to 1966. By 1964 he had made 10 expeditions to the Big Horn Basin , in Wyoming, east of Yellowstone National Park . Late in 1964, he discovered Deinonychus fossils near the town of Bridger, Montana . He also discovered and named Tenontosaurus fossils from the Cloverly Formation. In 1966 John H. Ostrom helped to establish Dinosaur State Park in Rocky Hill, Connecticut ("because

1518-503: The Peabody Museum of Natural History at Yale University. The type species is Hitchcock's A. polyzelus . Marsh's A. major (also known as Ammosaurus ), A. solus , and A. colurus (also known as Yaleosaurus ), have since been recognized as synonyms of A. polyzelus , their supposed differences being due to misinterpretation and different stages of growth. In 2015, the ICZN formally made

1584-515: The anthracosaurian Amphisaurus Barkas 1870, and again replaced it by Anchisaurus , with the same meaning. Meanwhile, nearly complete specimens had been found in Manchester, Connecticut . In 1884, a series of bridges was built over the Hop Creek . Sandstone blocks were sawed out of Wolcott's Quarry north of Buckland Station . On 20 October, an amateur paleontologist, Charles H. Owen, observed that

1650-586: The great apes , gorillas (eastern and western) are a sister group to chimpanzees , bonobos and humans . These five species form a clade, the subfamily Homininae (African apes), of which Gorilla has been termed the basal genus. However, if the analysis is not restricted to genera, the Homo plus Pan clade is also basal. Humans ( Homo sapiens ) Bonobos ( Pan paniscus ) Chimpanzees ( Pan troglodytes ) Eastern gorillas ( Gorilla beringei ) Western gorillas ( Gorilla gorilla ) Moreover, orangutans are

1716-623: The osteology and phylogeny of the primitive bird Archaeopteryx appeared in 1976. Ostrom lived to see the eventual discovery of feathered dinosaurs in northeastern China , confirming his theories about dinosaurs being progenitors of birds, and the existence of dinosaurs with feathered plumage. Ostrom was born in New York on February 18, 1928 and grew up in Schenectady . As a pre-medical undergraduate student at Union College , he originally aimed to prepare for medical school in order to become

1782-562: The Canadian paleontologist Dale Russell . Ostrom's reappraisal of dinosaurs as endothermic was considered radical at the time, but its ability to resolve outstanding contradictions in dinosaur physiology immediately drew many followers, and would be supported by many future discoveries. Ostrom's interest in the dinosaur-bird connection started with his study of what became known as the Haarlem Archaeopteryx . Discovered in 1855, it

1848-584: The Charles O. Wolcott Quarry near Manchester, Connecticut have since been destroyed. As early as October 20, 1884, stones from the Wolcott Quarry, reportedly containing fossils, were used to build a local bridge. In 1969, Ostrom surveyed over 60 bridges to find the missing blocks. They were part of a bridge over Hop Creek at Bridge Street which was scheduled for replacement. The highway department allowed Ostrom and his team to examine 400 sandstone blocks to find dinosaur fossils. Despite lobbying to preserve it,

1914-590: 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. Sauropodomorph remains were first documented in North America in 1818, when some bones nearly 1.8 m (6 ft) in length were uncovered by Mr. Solomon Ellsworth Jr. while excavating

1980-486: The bridge was demolished in August 1969, John Ostrom would save the front block. Subsequently, two other dinosaur fossils were located in the quarry. Six metres south of the original find a second skeleton was visible in the quarry face. It was removed as a single block and given the inventory number YPM 1883. In Yale, the part containing the skull was split off and became specimen YPM 40313. In 1891, Marsh made Anchisaurus major

2046-570: The case at the time. This idea was further justified by a 1922 paper that Ostrom rediscovered in 1964, which described the stomach contents of a mummified specimen of the hadrosaur Anatosaurus , which included conifer needles, twigs, fruit and seeds, plant matter that would be consumed in a terrestrial environment. In the 1970s, Ostrom examined trackways at the Dinosaur Footprints Reservation in Holyoke, Massachusetts . He mapped

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2112-400: The century. The implications of Deinonychus changed depictions of dinosaurs both by professional illustrators and as perceived by the public eye. Museums worldwide changed their dinosaur bone displays. The altered view of dinosaurs inspired a new generation of dinosaur movies such as Jurassic Park , which based its murderous "Velociraptors" on Deinonychus . Ostrom's work on Deinonychus

2178-503: The correlation of erect posture and locomotion with high metabolism and body temperature in modern mammals and birds, stating that this relationship cannot be accidental. The observation that dinosaurs, thought to be uniformly cold-blooded at the time, could not be used as indicators of paleoclimate was further validated in 1973 with the discovery of hadrosaur fossils above the Cretaceous Canadian Arctic Circle by

2244-492: The direction of migration away from the area of origin can also be inferred (as in the Amaurobioides and Noctilionoidea cases below). As with all other traits, the phylogeographic location of one clade that connects to the root does not provide information about the ancestral state. Examples where such unjustified inferences may have been made include: John Ostrom John Harold Ostrom (February 18, 1928 – July 16, 2005)

2310-552: The eastern Canadian province of Nova Scotia , scientists have unearthed prosauropods from the McCoy Brook Formation , which is about 200 to 197 million years old, from the Early Jurassic Hettangian stage. The Nova Scotia material provides clues about the diet of these animals. A large number of gastroliths , stones swallowed to grind up plant material in the gut, were found in the abdomen, as well as bone from

2376-459: The estimated average size of the adult Eubrontes track-maker in the Hartford and Deerfield basins. Based on the largest known Eubrontes footprint, exceptionally large individuals of Anchisaurus probably measured up to 6 meters (20 ft) in length. Due to its primitive appearance, Anchisaurus was previously classified as a prosauropod, a member of a group of animals related to or ancestral to

2442-719: The extant taxa of a given rank within the clade; this is one reason the term basal is highly deceptive, as the lack of additional species in one clade is taken as evidence of morphological affinity with ancestral taxa. Additionally, this qualification does not ensure that the diversity of extinct taxa (which may be poorly known) is represented. In phylogenetics, the term basal cannot be objectively applied to clades of organisms, but tends to be applied selectively and more controversially to groups or lineages thought to possess ancestral characters, or to such presumed ancestral traits themselves. In describing characters, "ancestral" or " plesiomorphic " are preferred to "basal" or " primitive ",

2508-453: The faculty at Beloit College the following year. In 1961 he accepted a professorship at Yale University , where he remained throughout his career. As a new professor at Yale, Ostrom was named the assistant curator for vertebrate paleontology at the Peabody Museum of Natural History . He became full professor and curator in 1971. Throughout his career, Ostrom led and organized fossil-hunting expeditions to Wyoming and Montana. He worked in

2574-665: The family; many of the dinosaurs once included have since been moved elsewhere, and the group is not used in most current taxonomies. Fossils of Anchisaurus were originally discovered in the Portland Formation of the Newark Supergroup in the Connecticut River Valley. This formation preserves an arid environment with strong wet and dry seasons, from the Hettangian age into the Sinemurian age, between about 200 and 195 million years ago. Digesting plant matter

2640-409: The finds as a new genus. Owen suggested the name Megadactylus , "large finger" in Greek, in reference to the enormous thumb of the animal. Hitchcock Jr himself then chose the specific name polyzelus , "much sought for" in Greek, referring to the fact that his father had for many years vainly sought to discover the identity of the track-maker. In 1877, Professor Othniel Charles Marsh had noted that

2706-403: The following case:   Basal clade #1  Non-basal clade #1  Non-basal clade #2    Non-basal clade #3 While it is easy to identify a basal clade in such a cladogram, the appropriateness of such an identification is dependent on the accuracy and completeness of the diagram. It is often assumed in this example that the terminal branches of the cladogram depict all

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2772-654: The governor was besieged by letters from schoolchildren swayed into dino-mania by Ostrom". ). Ostrom edited the American Journal of Science , published over a dozen books for both scientific and lay audiences. He was the recipient of numerous awards and honors. In the 1960s, Ostrom wrote a paleontology themed guide for the National Park Service 's National Natural Landmarks (NNLs) Program. He recommended 20 sites for designation and protection as NNLs, of which 13 became designated landmarks. Others sites such as

2838-618: The later sauropods such as Diplodocus . Prosauropods represented a middle phase between the earliest bipedal herbivores and the later giant sauropods. As a prosauropod, Anchisaurus was mostly typical of this group, which flourished briefly during the late Triassic and early Jurassic. Anchisaurus teeth, used to rip food, were shaped like spoons. It had fewer and more widely spaced teeth than true prosauropods, and as Peter Galton and Michael Cluver observed, narrower feet. Anchisaurus would have spent most of its time on four legs but could have reared up on its hind legs to reach higher plants. As

2904-437: The latter of which may carry false connotations of inferiority or a lack of complexity. The terms ''deep-branching'' or ''early-branching'' are similar in meaning, and equally may misrepresent extant taxa that lie on branches connecting directly to the root node as having more ancestral character states. Despite the ubiquity of the usage of basal , systematists try to avoid its usage because its application to extant groups

2970-406: The meaning of the animal's genus name. Ostrom also suggested that it had hunted in packs. John Ostrom's work on the functional morphology of dinosaurs found that the claws and tendon scars in the tail would indicate a running position. Evidence of a truly active lifestyle included long strings of muscle running along the tail, providing a stiff counterbalance for jumping and running. This changed

3036-490: The more complete type specimen of A. colurus the neotype of the genus Anchisaurus and the species A. polyzelus , rendering A. polyzelus and A. colurus objective synonyms (both names being based on exactly the same fossil). Broom named Gyposaurus capensis in 1911, from bones discovered in South Africa but Peter Galton renamed these Anchisaurus capensis in 1976. This species has since been reclassified again and

3102-555: The name Megadactylus had been preoccupied by Megadactylus Fitzinger 1843, a subgenus of the lizard genus Stellio . In 1882, he replaced the name with Amphisaurus , "near saurian", probably referring to Marsh's interpretation of it as intermediate between primitive dinosaurs—at the time the British Palaeosaurus was an example of what was thought to be a primitive dinosaur—and more derived dinosaurs. In 1885, Marsh had discovered that this name also had been preoccupied, by

3168-404: The posture of bipedal dinosaurs to one of agile, fast-running, fearsome predators. He concluded that at least some dinosaurs had a high metabolism and were in some cases warm-blooded . This position was further popularized by Ostrom's student Robert T. Bakker . This helped to change the impression of dinosaurs as sluggish, slow, cold-blooded lizards, which had prevailed since the turn of

3234-527: The presence of cf. Otozoum tracks on the Connecticut Valley, Anchisaurus could reach even greater sizes. Otozoum tracks were made by a semibipedal to quadrupedal sauropodomorph close to or on the line leading toward eusauropods. Anchisaurus is one of the two sauropodomorphs recognized in the zone. Based on the four known specimens of Anchisaurus , Yates estimated that the animal measured up to 4.9 meters (16 ft) in length. This matches well with

3300-419: The root of every cladogram, those clades may differ widely in taxonomic rank , species diversity , or both. If C is a basal clade within D that has the lowest rank of all basal clades within D , C may be described as the basal taxon of that rank within D . The concept of a ' key innovation ' implies some degree of correlation between evolutionary innovation and diversification . However, such

3366-423: The root than the majority, and in such cases, expressions like "very basal" can appear. A 'core clade' refers to the grouping that encompasses all constituent clades except for the basal clade(s) of the lowest rank within a larger clade, exemplified by core eudicots . No extant taxon is closer to the root than any other. A basal group in the stricter sense forms a sister group to the rest of the larger clade, as in

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3432-417: 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

3498-524: The sister group of a more species-rich clade displays ancestral features. An extant basal group may or may not resemble the last common ancestor of a larger clade to a greater degree than other groups, and is separated from that ancestor by the same amount of time as all other extant groups. However, there are cases where the unusually small size of a sister group does indeed correlate with an unusual number of ancestral traits, as in Amborella (see below). This

3564-551: The site, identifying preserved dinosaur tracks in the sandstone beds of various sizes and species. Ostrom's reading of fossilized Hadrosaurus trackways led him to the conclusion that these duckbilled dinosaurs were gregarious and traveled in herds. Ostrom worked in the Cloverly Formation Site in Montana and Wyoming from 1962 to 1966. Late in 1964, he detected unfamiliar fossils in the Bridger Fossil Area, near

3630-479: The skeletal anatomy of Archaeopteryx . He suggested that dinosaurs, far from becoming extinct, had evolved into a wide variety of descendants in the form of birds. Ostrom's work led to a revolution in the classification of fossils and the understanding of dinosaur-bird lineages. As a result of subsequent research and comparison with more recently found specimens from the Tiaojushan Formation of China, it

3696-414: The skull of a small sphenodont , Clevosaurus . This indicates that these dinosaurs were omnivorous, with a diet mainly consisting of plants but with an occasional supplement of meat. However, these remains have never been fully described or illustrated and were only tentatively referred to Ammosaurus . A further study identified them as a new taxon of sauropodomorph, Fendusaurus eldoni . Anchisaurus

3762-791: The summer as a field assistant in the San Juan Basin of New Mexico. Ostrom also worked as a research assistant with Colbert, who was the Curator of Vertebrate Paleontology at the American Museum of Natural History (AMNH), Ostrom earned his doctorate in geology (vertebrate paleontology) in 1960 with a thesis on North American hadrosaurs that was based on the skull collection housed at the AMNH. In 1952 Ostrom married Nancy Grace Hartman (d. 2003). They had two daughters, Karen and Alicia. Ostrom taught for one year at Brooklyn College in 1955 before joining

3828-468: The town of Bridger, Montana. In subsequent seasons, his team unearthed four specimens of a small bipedal carnivorous theropod , and parts of a larger plant-eating dinosaur. The discovery of the Deinonychus fossils is considered one of the most important fossil finds in history. Deinonychus was an active predator that clearly killed its prey by leaping and slashing or stabbing with its "terrible claw",

3894-427: The unique hadrosaur nasal apparatus, which had not been convincingly explained by the early 1960s. By examining the olfactory apparatuses of modern reptiles and drawing comparisons via comparative morphology , Ostrom concluded that hadrosaurs likely developed an acute sense of smell by a lengthening of the nasal passages into long chambers that wound around the skull and were protected by bony crests. He speculated in

3960-551: The workmen or kept by interested onlookers. As a result, these dinosaurs were only known from incomplete remains. In 1863, the son of the ichnologist Edward Hitchcock , Edward Hitchcock Jr, described the Springfield remains in a supplement to his father's work on fossil footprints, suggesting they could explain a certain mysterious kind of reptile tracks. He then contacted the British paleontologist Richard Owen . Owen advised him to name

4026-546: Was a rather small dinosaur, with a length of just over 2 meters (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 meters (8 ft 2 in to 13 ft 1 in) and some estimates give it a weight of up to 32 kilograms (70 lb). Gregory S. Paul estimated its length at 2.2 meters (7.2 ft) and its weight at 20 kilograms (44 lb) in 2010. According to

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4092-565: Was actually the first specimen recovered but, incorrectly labeled as Pterodactylus crassipes , it languished in the Teylers Museum in the Netherlands . Ostrom's 1970 paper (and 1972 description) identified it as one of only four specimens known to exist at that time. In his 1973 paper in Nature , "The Ancestry of Birds", Ostrom argued for a coelurosaurian (Theropoda) ancestry of birds, based on

4158-650: Was an American paleontologist who revolutionized the modern understanding of dinosaurs . Ostrom's work inspired what his pupil Robert T. Bakker has termed a " dinosaur renaissance ". Beginning with the discovery of Deinonychus in 1964, Ostrom challenged the widespread belief that dinosaurs were slow-moving lizards (or "saurians"). He argued that Deinonychus , a small two-legged carnivore, would have been fast-moving and warm-blooded. Further, Ostrom's work made zoologists question whether birds should be considered an order of Reptilia instead of their own class, Aves . The idea that dinosaurs were similar to birds

4224-485: Was first proposed by Thomas Henry Huxley in the 1860s, but was dismissed by Gerhard Heilmann in his influential book The Origin of Birds (1926). Prior to Ostrom's work, the development of birds was generally believed to have split off early on from that of dinosaurs. Ostrom showed more bird-like traits common in dinosaurs and proved that birds themselves are in fact a group of coelurosaurian theropod dinosaurs. The first of Ostrom's broad-based reviews of

4290-610: Was one of the first paleontologists to grasp the implications of the amount of energy it would take such large animals (and their still larger predators, such as Tyrannosaurus rex ) to stand and move erect. At the first North American Paleontological Convention, held at the Chicago Field Museum in 1969, Ostrom spoke out against the accepted wisdom that Mesozoic climates were universally tropical and that such warm climates would be necessary to sustain large animals with lizard-like metabolisms . Ostrom supported this view by noting

4356-462: Was suggested in 2017 that the Haarlem Archaeopteryx actually represents a separate taxon. The genus has been given the generic name Ostromia , after John Ostrom. The Haarlem fossil is now considered to be of the species Ostromia crassipes . It is the first representative of the basal avialian clade Anchiornithidae to be found outside eastern Asia. In considering the possible evolution of flight, Ostrom theorized that birds might have evolved

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