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Sexual Dimorphism In Dinosaurs
Sexual dimorphism in dinosaurs refers to the different physical characteristics of male and female dinosaurs of the same species. This means that the male and female dinosaurs of a species may differ in size, color, shape, or they may even look like a completely different species altogether, such as in the case of the anglerfish. These differing physical characteristics can also be the deciding factor for choosing a mate or can be helpful for blending into the surrounding environment. Researching sexual dimorphism in dinosaurs can be extremely difficult because suitable tissue and skeletal samples are required for testing, and most fossils and other samples have been damaged by decomposition and fossilization. Sexual dimorphism and dinosaurs Examining fossils of dinosaurs in search of sexually dimorphic characteristics requires the supply of complete and articulated skeletal and tissue remains. As terrestrial organisms, dinosaur carcasses are subject to ecological and geographical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya; their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds. Dinosaurs are varied from taxonomic, morphological and ecological standpoints. Birds, at over 10,700 living species, ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theropoda
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago ( Ma) and included all the large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species. Biology Diet and teeth Theropods exhibit a wide range of diets, from insectivores to herbivores and carnivores. Strict carnivory has always been considered the ancestral diet for theropods as a group, and a wider variety of diets was historically considered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dewlaps
A dewlap is a longitudinal flap of skin or similar flesh that hangs beneath the lower jaw or neck of many vertebrates. More loosely, it can be various similar structures in the neck area, such as those caused by a double chin or the submandibular vocal sac of a frog. More generally, it can be any hanging mass of skin, such as a fold of loose skin on an elderly human, person's neck, or the wattle (anatomy), wattle of a bird. Dewlaps can be considered as a Caruncle (bird anatomy), ''caruncle'', defined as "a small, fleshy excrescence that is a normal part of an animal's anatomy". Etymology The word is first attested in the mid 1300s as ''dewelappe'' ("fold of skin that hangs from the throat of oxen and cows, kine"), from ''lappe'' ("loose piece", from Old English ), but the first element ''*dew(e)-'' is of nebulous origin and meaning; it probably was altered by folk etymology with "dew". Old English had ''fræt-læppa'' in the aforementioned sense (and Middle English ''fresh-lappe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct therapsids and all extant mammals). Tetrapods evolved from a clade of primitive semiaquatic animals known as the Tetrapodomorpha which, in turn, evolved from ancient lobe-finned fish (sarcopterygians) around 390 million years ago in the Middle Devonian period; their forms were transitional between lobe-finned fishes and true four-limbed tetrapods. Limbed vertebrates (tetrapods in the broad sense of the word) are first known from Middle Devonian trackways, and body fossils became common near the end of the Late Devonian but these were all aquatic. The first crown-tetrapods ( last common ancestors of extant tetrapods capable of terrestrial locomotion) appeared by the very early Carboniferous, 350 million years ago. The specific aquat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Protoceratops Andrewsi
''Protoceratops'' (; ) is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 75 to 71 million years ago. The genus ''Protoceratops'' includes two species: ''P. andrewsi'' and the larger ''P. hellenikorhinus''. The former was described in 1923 with fossils from the Mongolian Djadokhta Formation, and the latter in 2001 with fossils from the Chinese Bayan Mandahu Formation. ''Protoceratops'' was initially believed to be an ancestor of ankylosaurians and larger ceratopsians, such as ''Triceratops'' and relatives, until the discoveries of other protoceratopsids. Populations of ''P. andrewsi'' may have evolved into ''Bagaceratops'' through anagenesis. ''Protoceratops'' were small ceratopsians, about long and in body mass. While adults were largely quadrupedal, juveniles had the capacity to walk around Facultative bipedalism, bipedally if necessary. They were characterized by a proportionally large skull, short and stiff neck, and neck fri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most animals and some plants. Differences may include secondary sex characteristics, size, weight, colour, markings, or behavioural or cognitive traits. These differences may be subtle or exaggerated and may be subjected to sexual selection and natural selection. The opposite of dimorphism is ''monomorphism'', which is when both biological sexes are phenotypically indistinguishable from each other. Overview Ornamentation and coloration Common and easily identified types of dimorphism consist of ornamentation and coloration, though not always apparent. A difference in coloration of sexes within a given species is called sexual dichromatism, which is commonly seen in many species of birds and reptiles. Sexual selection leads to the exaggerated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cranial Neural Crest
The cranial neural crest is one of the four regions of the neural crest. The cranial neural crest arises in the anterior and populates the face and the pharyngeal arches giving rise to bones, cartilage, nerves and connective tissue. The endocranium and facial bones of the skull are ultimately derived from crest cells. :''Other Migration Locations:'' :*Into the pharyngeal arches and play an inductive role in thymus development. :*Into the pharyngeal arches and form the parafollicular cell or ultimobranchial bodies of the thyroid gland. :*Into the pharyngeal arches and play an inductive role in parathyroid gland development. :*Facial ectomesenchyme of the pharyngeal arches forming skeletal muscle, bone, and cartilage in the face. :*Odontoblasts (dentin-producing cells) of the teeth. :*Around the optic vesicle and the developing eye and contributes to many eye elements such the choroid, sclera, iris, and ciliary body. It also contributes to the attaching skeletal muscles of the eye. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hadrosaurid
Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which includes genera such as '' Edmontosaurus'' and '' Parasaurolophus'', was a common group of herbivores during the Late Cretaceous Period. Hadrosaurids are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had a similar body layout. Hadrosaurs were among the most dominant herbivores during the Late Cretaceous in Asia and North America, and during the close of the Cretaceous several lineages dispersed into Europe, Africa, South America and Antarctica. Like other ornithischians, hadrosaurids had a predentary bone and a pubic bone which was positioned backwards in the pelvis. Unlike more primitive iguanodonts, the teeth of hadrosaurids are stacked into complex structures known as dental batteries, which acted as ef ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haemal Arch
A haemal arch also known as a chevron, is a bony arch on the ventral side of a tail vertebra of a vertebrate. The canal formed by the space between the arch and the vertebral body is the haemal canal. A spinous ventral process emerging from the haemal arch is referred to as the haemal spine. Blood vessels to and from the tail run through the arch. In reptiles, the caudofemoralis longus muscle, one of the main muscles involved in locomotion, attaches to the lateral sides of the haemal arches. In 1956, Alfred Sherwood Romer hypothesized that the position of the first haemal arch was sexually dimorphic in crocodilians and dinosaurs. However, subsequent research established that the size and position of the first haemal arch was not sexually dimorphic in crocodilians and found no evidence of significant variation in tyrannosaurid dinosaurs, indicating that haemal arches could not be used to distinguish between sexes after all. Haemal arches play an important role in the taxonomy of s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crocodilia
Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria. Members of the order's total group, the clade Pseudosuchia, appeared about 250 million years ago in the Early Triassic period, and diversified during the Mesozoic era. The order Crocodilia includes the true crocodiles (family Crocodylidae), the alligators and caimans (family Alligatoridae), and the gharial and false gharial (family Gavialidae). Although the term 'crocodiles' is sometimes used to refer to all of these, crocodilians is a less ambiguous vernacular term for members of this group. Large, solidly built, lizard-like reptiles, crocodilians have long flattened snouts, laterally compressed tails, and eyes, ears, and nostrils ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Camarasaurus
''Camarasaurus'' ( ) was a genus of quadrupedal, herbivorous dinosaurs and is the most common North American sauropod fossil. Its fossil remains have been found in the Morrison Formation, dating to the Late Jurassic epoch ( Kimmeridgian to Tithonian stages), between 155 and 145 million years ago. ''Camarasaurus'' presented a distinctive cranial profile of a blunt snout and an arched skull that was remarkably square, typical of basal Macronarians. The name means "chambered lizard", referring to the hollow chambers, known as pleurocoels, in its cervical vertebrae ( Greek (') meaning "vaulted chamber", or anything with an arched cover, and (') meaning "lizard". ''Camarasaurus'' contains four species that are commonly recognized as valid: '' Camarasaurus grandis'', ''Camarasaurus lentus'', ''Camarasaurus lewisi'', and '' Camarasaurus supremus''. ''C. supremus'', the type species, is the largest and geologically youngest of the four. ''Camarasaurus'' is the type genus o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anglerfish
The anglerfish are fish of the teleost order Lophiiformes (). They are bony fish named for their characteristic mode of predation, in which a modified luminescent fin ray (the esca or illicium) acts as a lure for other fish. The luminescence comes from symbiotic bacteria, which are thought to be acquired from seawater, that dwell in and around the sea. Some anglerfish are notable for extreme sexual dimorphism and sexual symbiosis of the small male with the much larger female, seen in the suborder Ceratioidei, the deep sea anglerfish. In these species, males may be several orders of magnitude smaller than females. Anglerfish occur worldwide. Some are pelagic (dwelling away from the sea floor), while others are benthic (dwelling close to the sea floor). Some live in the deep sea (such as the Ceratiidae), while others on the continental shelf, such as the frogfishes and the Lophiidae (monkfish or goosefish). Pelagic forms are most often laterally compressed, whereas the b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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