Stegomosuchus Temporal range: Early Jurassic | |
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Stegomosuchus longipes skeleton replica | |
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Genus: | Stegomosuchus von Huene, 1922 |
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Stegomosuchus is an extinct genus of small protosuchian crocodyliform. It is known from a single incomplete specimen discovered in the late 19th century in Lower Jurassic rocks of south-central Massachusetts, United States. It was originally thought to be a species of Stegomus , an aetosaur (a type of armored herbivorous reptile), but was eventually shown to be related to Protosuchus and thus closer to the ancestry of crocodilians. Stegomosuchus is also regarded as a candidate for the maker of at least some of the tracks named Batrachopus in the Connecticut River Valley.
The holotype and only known specimen of Stegomosuchus (AM 900 [1] ) was discovered at what was then known as the Hines Quarry, east of East Longmeadow, Massachusetts, just before the turn of the 20th century. It was found 10 feet (3.0 m) below the surface, in red sandstone used for building material. [2] This site is now called the Hoover Quarry; it has also yielded invertebrate trace fossils and dinosaur tracks ( Eubrontes ). [3] [4] The rocks are now known to belong to the Portland Formation. [5] [6] While thought to be Triassic when Stegomosuchus was originally described, [2] the Portland Formation is now known to date to the Early Jurassic, including the Hettangian and Sinemurian stages [7] (approximately 200 to 190 million years ago).
Its discoverer, G. B. Robinson, took home the blocks containing the specimen and placed them in his door yard, where they were exposed to the elements for "about seven years." The fossil was then found and obtained by Mr. and Mrs. E. D. White, and the specimen was then described by B. K. Emerson and F. B. Loomis in 1904. At that point, the specimen was in three blocks. The bones had been largely preserved as impressions, and the two main blocks had upper and lower impressions of the skull, twenty-eight pairs of armor plates situated along the spine up to the pelvis, right arm (minus the hand) and shoulder blade, and left foot. [2] Emerson and Loomis interpreted the impressions as showing another row of armor along the sides, but this was later shown to be a mistake. [8] AM 900 was a small animal, with a skull estimated at 35 millimetres (1.4 in) long and 27 millimetres (1.1 in) across, and a body length from snout to pelvis of 149 millimetres (5.9 in). Emerson and Loomis described the specimen as a new species of Stegomus (S. longipes), an aetosaur known from slightly older rocks. [2]
The assessment of the material as belonging to a species of the aetosaur Stegomus held for about twenty years, [9] [10] until Friedrich von Huene reclassified it, giving the species the new genus Stegomosuchus and new family Stegomosuchidae, in the Pseudosuchia. [11]
Its classification was further reassessed by Alick Walker over forty-five years later, who reinterpreted Stegomosuchus as a close relative of Protosuchus, a crocodile-like reptile of similar age. In making this change, he noted that Stegomosuchidae should have priority over Protosuchidae. He also regarded AM 900 as a juvenile. [8] The reassignment of Stegomosuchus was followed, [5] [6] [12] [13] although Alfred Romer recommended passing over Stegomosuchidae for the more familiar Protosuchidae. [13] Whetstone and Whybrow (1983) agreed that a protosuchian identity was probable, but found AM 900 too poorly preserved and lacking too many important parts of the body to classify further. [14]
By comparison to other protosuchids, Stegomosuchus was probably a terrestrial carnivore. [15]
In the same issue of The American Journal of Science that contained the description of Stegomus longipes, Richard Swann Lull published a short article in which he proposed that S. longipes had produced previously known tracks named Batrachopus gracilis, also from the Connecticut River Valley. [16] This assessment has been followed, although the ichnospecies assigned to Batrachopus have since been consolidated; B. deweyi is now the name for the tracks in question. [17]
The Hoover Quarry may represent a playa, or dry lake, a shallow lake, or a river setting. [3] [4] The Portland Formation as a whole is composed of reddish shallow–water and gray or black deeper water rocks in the lower part of the formation, and coarser red rocks from river or alluvial settings in the upper part of the formation. [6] It has yielded fossils of algal structures, pollen, trees and smaller plants, bivalves, clam shrimp, ostracodes, beetles, invertebrate traces, several genera of fish ( Acentrophorus , Redfieldius , Semionotus , and the coelacanth Diplurus ), the theropod dinosaur Podokesaurus , the sauropodomorph dinosaur Anchisaurus , vertebrate coprolites (fossilized droppings), and several vertebrate track genera ( Batrachopus , the theropod tracks Anchisauripus , Eubrontes , and Grallator , the prosauropod tracks Otozoum , and the ornithischian dinosaur tracks Anomoepus ). [5] [6]
Coelophysis is a genus of coelophysid theropod dinosaur that lived approximately 215 to 208.5 million years ago during the Late Triassic period from the middle to late Norian age in what is now the southwestern United States. Megapnosaurus was once considered to be a species within this genus, but this interpretation has been challenged since 2017 and the genus Megapnosaurus is now considered valid.
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 the Greek αγχιanchi-; "near, close" + Greek σαυρος ; "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.
Coelurus is a genus of coelurosaurian dinosaur from the Late Jurassic period. The name means "hollow tail", referring to its hollow tail vertebrae. Although its name is linked to one of the main divisions of theropods (Coelurosauria), it has historically been poorly understood, and sometimes confused with its better-known contemporary Ornitholestes. Like many dinosaurs studied in the early years of paleontology, it has had a confusing taxonomic history, with several species being named and later transferred to other genera or abandoned. Only one species is currently recognized as valid: the type species, C. fragilis, described by Othniel Charles Marsh in 1879. It is known from one partial skeleton found in the Morrison Formation of Wyoming, United States. It was a small bipedal carnivore with elongate legs.
Podokesaurus is a genus of coelophysoid dinosaur that lived in what is now the eastern United States during the Early Jurassic Period. The first fossil was discovered by the geologist Mignon Talbot near Mount Holyoke, Massachusetts, in 1910. The specimen was fragmentary, preserving much of the body, limbs, and tail. In 1911, Talbot described and named the new genus and species Podokesaurus holyokensis based on it. The full name can be translated as "swift-footed lizard of Holyoke". This discovery made Talbot the first woman to find and describe a non-bird dinosaur. The holotype fossil was recognized as significant and was studied by other researchers, but was lost when the building it was kept in burned down in 1917; no unequivocal Podokesaurus specimens have since been discovered. It was made state dinosaur of Massachusetts in 2022.
Aetosaurs are heavily armored reptiles belonging to the extinct order Aetosauria. They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs more closely related to crocodilians than to birds and other dinosaurs. All known aetosaurs are restricted to the Late Triassic, and in some strata from this time they are among the most abundant fossil vertebrates. They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like osteoderms. Aetosaur fossil remains are known from Europe, North and South America, parts of Africa, and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site in which they are found.
Atlantosaurus is a dubious genus of sauropod dinosaur. It contains a single species, Atlantosaurus montanus, from the upper Morrison Formation of Colorado, United States. Atlantosaurus was the first sauropod to be described during the infamous 19th century Bone Wars, during which scientific methodology suffered in favor of pursuit of academic acclaim.
Laosaurus is a genus of neornithischian dinosaur. The type species, Laosaurus celer, was first described by O.C. Marsh in 1878 from remains from the Oxfordian-Tithonian-age Upper Jurassic Morrison Formation of Wyoming. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species from the Morrison Formation, L. gracilis, and a species from the late Cretaceous Allison Formation of Alberta, Canada, Laosaurus minimus, are also considered dubious.
Nanosaurus is an extinct genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic in North America. Its fossils are known from the Morrison Formation of the south-western United States. The type and only species, Nanosaurus agilis, was described and named by Othniel Charles Marsh in 1877. The taxon has a complicated taxonomic history, largely the work of Marsh and Peter M. Galton, involving the genera Laosaurus, Hallopus, Drinker, Othnielia, and Othnielosaurus, the latter three now being considered to be synonyms of Nanosaurus. It had historically been classified as a hypsilophodont or fabrosaur, types of generalized small bipedal herbivore, but more recent research has abandoned these groupings as paraphyletic and Nanosaurus is today considered a basal member of Neornithischia.
Gwyneddosaurus is a possibly invalid genus of extinct aquatic tanystropheid reptile. The type species, G. erici was described in 1945 by Wilhelm Bock, who identified it as a coelurosaurian dinosaur related to Podokesaurus. Its remains were found in the Upper Triassic Lockatong Formation of Montgomery County, eastern Pennsylvania, and the holotype includes skull fragments, several vertebra, ribs, gastralia, partial shoulder and hip bones, and several forelimb and hindlimb elements found in soft shale, while the paratype includes a femur and a tibia. The type specimen is ANSP 15072 and it was discovered by Bock's four-year-old son while the paratype is only listed as ?(ASNP coll.). It was not a large animal; the type skeleton was estimated by Bock as 18 centimetres (7.1 in) long, and its thigh bone was only 23 millimeters long (0.91 in).
Aetosaurus is an extinct genus of pseudosuchian reptile belonging to the order Aetosauria. It is generally considered to be the most primitive aetosaur. Three species are currently recognized: A. ferratus, the type species from Germany and Italy; A. crassicauda from Germany; and A. arcuatus from eastern North America. Additional specimens referred to Aetosaurus have been found in the Chinle Group of the southwestern United States, and the Fleming Fjord Formation of Greenland. Specimens of Aetosaurus occur in Norian-age strata.
Camarasaurus grandis is an extinct species of sauropod dinosaur in the genus that lived during the Jurassic in what is now the western United States. It is the geologically oldest of the four species of the genus Camarasaurus.
The Portland Formation is a geological formation in Connecticut and Massachusetts in the northeastern United States. It dates back to the Early Jurassic period. The formation consists mainly of sandstone laid down by a series of lakes and the floodplain of a river. The sedimentary rock layers representing the entire Portland Formation are over 4 kilometres (2.5 mi) thick and were formed over about 4 million years of time, from the Hettangian age to the late Hettangian and Sinemurian ages.
Charles Emerson Beecher was an American paleontologist most famous for the thorough excavation, preparation and study of trilobite ventral anatomy from specimens collected at Beecher's Trilobite Bed. Beecher was rapidly promoted at Yale Peabody Museum, eventually rising to head that institution.
Theretairus is a Late Jurassic genus of sphenodont reptile from the Morrison Formation of western North America, present in stratigraphic zones 5 and 6.
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The Moenave Formation is a Mesozoic geologic formation, in the Glen Canyon Group. It is found in Utah and Arizona.
Platyognathus is an extinct genus of protosuchian crocodyliform. Fossils are known from the Early Jurassic Lower Lufeng Formation in Yunnan, China and belong to the type and only species, P. hsui.
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Paleontology in Virginia refers to paleontological research occurring within or conducted by people from the U.S. state of Virginia. The geologic column in Virginia spans from the Cambrian to the Quaternary. During the early part of the Paleozoic, Virginia was covered by a warm shallow sea. This sea would come to be inhabited by creatures like brachiopods, bryozoans, corals, and nautiloids. The state was briefly out of the sea during the Ordovician, but by the Silurian it was once again submerged. During this second period of inundation the state was home to brachiopods, trilobites and entire reef systems. During the mid-to-late Carboniferous the state gradually became a swampy environment.
Paleontology in Connecticut refers to paleontological research occurring within or conducted by people from the U.S. state of Connecticut. Apart from its famous dinosaur tracks, the fossil record in Connecticut is relatively sparse. The oldest known fossils in Connecticut date back to the Triassic period. At the time, Pangaea was beginning to divide and local rift valleys became massive lakes. A wide variety of vegetation, invertebrates and reptiles are known from Triassic Connecticut. During the Early Jurassic local dinosaurs left behind an abundance of footprints that would later fossilize.