Reptiles, as most commonly defined, are the animals in the class Reptilia, a paraphyletic grouping comprising all amniotes except synapsids and Aves (birds). Living reptiles comprise turtles, crocodilians, squamates and rhynchocephalians (tuatara). In the traditional Linnaean classification system, birds are considered a separate class to reptiles. However, crocodilians are more closely related to birds than they are to other living reptiles, and so modern cladistic classification systems include birds within Reptilia, redefining the term as a clade. Other cladistic definitions abandon the term reptile altogether in favor of the clade Sauropsida, which refers to all animals more closely related to modern reptiles than to mammals. The study of the traditional reptile orders, historically combined with that of modern amphibians, is called herpetology.
Tetrapods are four-limbed animals constituting the superclass Tetrapoda. It includes extant and extinct amphibians, reptiles, and synapsids. Tetrapods evolved from a group of animals known as the Tetrapodomorpha which, in turn, evolved from ancient sarcopterygian fish around 390 million years ago in the middle Devonian period; their forms were transitional between lobe-finned fishes and the four-limbed tetrapods. The first crown-tetrapods appeared by the very early Carboniferous, 350 million years ago. The specific aquatic ancestors of the tetrapods and the process by which they colonized Earth's land after emerging from water remains unclear. The change from a body plan for breathing and navigating in water to a body plan enabling the animal to move on land is one of the most profound evolutionary changes known. The first tetrapods (stem) or "fishapods" were primarily aquatic. Modern amphibians, which evolved from earlier groups, are generally semiaquatic; the first stage of their lives is as fish-like tadpoles, and later stages are partly terrestrial and partly aquatic. However, most tetrapod species today are amniotes, most of which are terrestrial tetrapods whose branch evolved from earlier tetrapods about 340 million years ago. The key innovation in amniotes over amphibians is the amnion, which enables the eggs to retain their aqueous contents on land, rather than needing to stay in water.
Sauropsida is a clade of amniotes, broadly equivalent to the class Reptilia. Sauropsida is the sister taxon to Synapsida, the clade of amniotes which includes mammals as its only modern representatives. Although early synapsids have historically been referred to as "mammal-like reptiles," all synapsids are more closely related to mammals than to any modern reptile. Sauropsids, on the other hand, include all amniotes more closely related to modern reptiles than to mammals. This includes Aves (birds), which are now recognized as a subgroup of archosaurian reptiles despite originally being named as a separate class in Linnaean taxonomy.
The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians.
Buccal pumping is "breathing with one's cheeks": a method of ventilation used in respiration in which the animal moves the floor of its mouth in a rhythmic manner that is externally apparent. It is the sole means of inflating the lungs in amphibians.
A forelimb or front limb is one of the paired articulated appendages (limbs) attached on the cranial (anterior) end of a terrestrial tetrapod vertebrate's torso. With reference to quadrupeds, the term foreleg or front leg is often used instead. In bipedal animals with an upright posture, the term upper limb is often used.
Robert "Bob" Lynn Carroll was an American–Canadian vertebrate paleontologist who specialised in Paleozoic and Mesozoic amphibians and reptiles.
Varanus salvadorii, also known as the crocodile monitor, Papua(n) monitor, Salvadori's monitor, and artellia, is a species of monitor lizard endemic to New Guinea. It is the largest monitor lizard known from New Guinea, and is one of the longest lizards in the world, verified at up to 244 cm (8 ft). The tail of the species is exceptionally long, so some specimens have been claimed to exceed the length of the world's largest lizard, the Komodo dragon; however, V. salvadorii is far less massive.
David Burton Wake was an American herpetologist. He was professor of integrative biology and Director and curator of herpetology of the Museum of Vertebrate Zoology at the University of California, Berkeley. Wake is known for his work on the biology and evolution of salamanders as well as general issues of vertebrate evolutionary biology. He has served as president of the Society for the Study of Evolution, the American Society of Naturalists, and American Society of Zoologists. He was a member of the American Association for the Advancement of Science, the Linnean Society of London, the American Academy of Arts and Sciences, the American Philosophical Society, and in 1998 was elected into the National Academy of Sciences. He was awarded the 2006 Leidy Award from the Academy of Natural Sciences of Philadelphia.
Myomeres are blocks of skeletal muscle tissue arranged in sequence, found commonly in chordates. Myomeres are separated from adjacent myomeres by connective tissues (myosepta) and most easily seen in larval fishes or in the olm. Myomere counts are sometimes used for identifying specimens, since their number corresponds to the number of vertebrae in the adults. Location varies, with some species containing these only near the tails, while some have them located near the scapular or pelvic girdles. Depending on the species, myomeres could be arranged in an epaxial or hypaxial manner. Hypaxial refers to ventral muscles and related structures while epaxial refers to more dorsal muscles. The horizontal septum divides these two regions in vertebrates from cyclostomes to higher order vertebrates.
Pharyngeal jaws are a "second set" of jaws contained within an animal's throat, or pharynx, distinct from the primary or oral jaws. They are believed to have originated as modified gill arches, in much the same way as oral jaws. Originally hypothesized to have evolved only once, current morphological and genetic analyses suggest at least two separate points of origin. Based on connections between musculoskeletal morphology and dentition, diet has been proposed as a main driver of the evolution of the pharyngeal jaw. A study conducted on cichlids showed that the pharyngeal jaws can undergo morphological changes in less than two years in response to their diet. Fish that ate hard-shelled prey had a robust jaw with molar-like teeth fit for crushing their durable prey. Fish that ate softer prey, on the other hand, exhibited a more slender jaw with thin, curved teeth used for tearing apart fleshy prey. These rapid changes are an example of phenotypic plasticity, wherein environmental factors affect genetic expression responsible for pharyngeal jaw development. Studies of the genetic pathways suggest that receptors in the jaw bone respond to the mechanical strain of biting hard-shelled prey, which prompts the formation of a more robust set of pharyngeal jaws.
Matthew Bonnan is an American paleobiologist and a Professor of Biological Sciences at Stockton University. His research combines traditional descriptive and anatomical study with computer-aided morphometric analysis and modeling of vertebrate skeletons. See also Dr. Bonnan's blog on his research and teaching at The Evolving Paleontologist.
Iguana is a genus of herbivorous lizards that are native to tropical areas of Mexico, Central America, South America, and the Caribbean. The genus was first described in 1768 by Austrian naturalist Josephus Nicolaus Laurenti in his book Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis circa Venena. Two species are placed in the genus, the green iguana, which is widespread throughout its range and a popular pet, and the Lesser Antillean iguana, which is native to the Lesser Antilles. Genetic analysis indicates that the green iguana may comprise a complex of multiple species, some of which have been recently described, but the Reptile Database considers all of these as subspecies of the green iguana.
Aquatic feeding mechanisms face a special difficulty as compared to feeding on land, because the density of water is about the same as that of the prey, so the prey tends to be pushed away when the mouth is closed. This problem was first identified by Robert McNeill Alexander. As a result, underwater predators, especially bony fish, have evolved a number of specialized feeding mechanisms, such as filter feeding, ram feeding, suction feeding, protrusion, and pivot feeding.
Susan E. Evans is British palaeontologist and herpetologist. She is the author or co-author of over 100 peer-reviewed papers and book chapters.
Most bony fishes have two sets of jaws made mainly of bone. The primary oral jaws open and close the mouth, and a second set of pharyngeal jaws are positioned at the back of the throat. The oral jaws are used to capture and manipulate prey by biting and crushing. The pharyngeal jaws, so-called because they are positioned within the pharynx, are used to further process the food and move it from the mouth to the stomach.
X-ray motion analysis is a technique used to track the movement of objects using X-rays. This is done by placing the subject to be imaged in the center of the X-ray beam and recording the motion using an image intensifier and a high-speed camera, allowing for high quality videos sampled many times per second. Depending on the settings of the X-rays, this technique can visualize specific structures in an object, such as bones or cartilage. X-ray motion analysis can be used to perform gait analysis, analyze joint movement, or record the motion of bones obscured by soft tissue. The ability to measure skeletal motions is a key aspect to one's understanding of vertebrate biomechanics, energetics, and motor control.
Brooke E. Flammang is an American biologist at the New Jersey Institute of Technology. She specializes in functional morphology, biomechanics, and bioinspired technology of fishes. Flammang is a discoverer of the radialis muscle in shark tails. She also studies the adhesive disc of the remora, and the walking cavefish, Cryptotora thamicola. Her work has been profiled by major news outlets including The New York Times, The Washington Post, Wired, BBC Radio 5, Discovery Channel, and National Geographic Wild. She was named one of the "best shark scientists to follow" by Scientific American in 2014.
Kenro Kusumi, a genome biologist and professor, Dean of Natural Sciences in The College of Liberal Arts and Sciences at Arizona State University.
Sharlene E. Santana is a Venezuelan–American biologist, currently serving as the Curator of Mammals at the Burke Museum of Natural History and as a professor of Evolutionary biology at the University of Washington, in Seattle, Washington. Her research primarily focuses on the order Chiroptera (bats), and her work often engages with a diverse range of biological disciplines, including evolution, systematics, biomechanics, behavioral studies, and ecology. Santana has worked to expand opportunities for underrepresented minorities in STEM fields and has relied on innovative applications of technology to increase the amount of high-quality scientific information that is available to the general public.
