Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
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, 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 million years ago. Reverse genetic engineering and the fossil record both demonstrate that birds are modern feathered dinosaurs, having evolved from earlier theropods during the late Jurassic Period; as such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event 66 million years ago. Dinosaurs can therefore be divided into birds; this article deals with non-avian dinosaurs. Dinosaurs are a varied group of animals from taxonomic and ecological standpoints. Birds, at over 10,000 living species, are the most diverse group of vertebrates besides perciform fish. Using fossil evidence, paleontologists have identified over 500 distinct genera and more than 1,000 different species of non-avian dinosaurs.
Dinosaurs are represented on every continent by fossil remains. Through the first half of the 20th century, before birds were recognized to be dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded. Most research conducted since the 1970s, has indicated that all dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction; some were herbivorous, others carnivorous. Evidence suggests that egg-laying and nest-building are additional traits shared by all dinosaurs and non-avian alike. While dinosaurs were ancestrally bipedal, many extinct groups included quadrupedal species, some were able to shift between these stances. Elaborate display structures such as horns or crests are common to all dinosaur groups, some extinct groups developed skeletal modifications such as bony armor and spines. While the dinosaurs' modern-day surviving avian lineage are small due to the constraints of flight, many prehistoric dinosaurs were large-bodied—the largest sauropod dinosaurs are estimated to have reached lengths of 39.7 meters and heights of 18 meters and were the largest land animals of all time.
Still, the idea that non-avian dinosaurs were uniformly gigantic is a misconception based in part on preservation bias, as large, sturdy bones are more to last until they are fossilized. Many dinosaurs were quite small: Xixianykus, for example, was only about 50 cm long. Since the first dinosaur fossils were recognized in the early 19th century, mounted fossil dinosaur skeletons have been major attractions at museums around the world, dinosaurs have become an enduring part of world culture; the large sizes of some dinosaur groups, as well as their monstrous and fantastic nature, have ensured dinosaurs' regular appearance in best-selling books and films, such as Jurassic Park. Persistent public enthusiasm for the animals has resulted in significant funding for dinosaur science, new discoveries are covered by the media; the taxon'Dinosauria' was formally named in 1841 by paleontologist Sir Richard Owen, who used it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were being recognized in England and around the world.
The term is derived from Ancient Greek δεινός, meaning'terrible, potent or fearfully great', σαῦρος, meaning'lizard or reptile'. Though the taxonomic name has been interpreted as a reference to dinosaurs' teeth and other fearsome characteristics, Owen intended it to evoke their size and majesty. Other prehistoric animals, including pterosaurs, ichthyosaurs and Dimetrodon, while popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs. Pterosaurs are distantly related to dinosaurs; the other groups mentioned are, like dinosaurs and pterosaurs, members of Sauropsida, except Dimetrodon. Under phylogenetic nomenclature, dinosaurs are defined as the group consisting of the most recent common ancestor of Triceratops and Neornithes, all its descendants, it has been suggested that Dinosauria be defined with respect to the MRCA of Megalosaurus and Iguanodon, because these were two of the three genera cited by Richard Owen when he recognized the Dinosauria. Both definitions result in the same set of animals being defined as dinosaurs: "Dinosauria = Ornithischia + Saurischia", encompassing ankylosaurians, ceratopsians, ornithopods and sauropodomorphs.
Birds are now recognized as being the sole surviving lineage of theropod dinosaurs. In traditional taxonomy, birds were considered a separate class that had evolved from dinosaurs, a distinct superorder. However, a majority of contemporary paleontologists concerned with dinosaurs reject the traditional style of classification in favor of phylogenetic taxonomy. Birds are thus considered to be dinosaurs and dinosaurs are, not extinct. Birds are classified as belonging to the subgroup M
Anatomical terms of location
Standard anatomical terms of location deal unambiguously with the anatomy of animals, including humans. All vertebrates have the same basic body plan – they are bilaterally symmetrical in early embryonic stages and bilaterally symmetrical in adulthood; that is, they have mirror-image left and right halves if divided down the middle. For these reasons, the basic directional terms can be considered to be those used in vertebrates. By extension, the same terms are used for many other organisms as well. While these terms are standardized within specific fields of biology, there are unavoidable, sometimes dramatic, differences between some disciplines. For example, differences in terminology remain a problem that, to some extent, still separates the terminology of human anatomy from that used in the study of various other zoological categories. Standardized anatomical and zoological terms of location have been developed based on Latin and Greek words, to enable all biological and medical scientists to delineate and communicate information about animal bodies and their component organs though the meaning of some of the terms is context-sensitive.
The vertebrates and Craniata share a substantial heritage and common structure, so many of the same terms are used for location. To avoid ambiguities this terminology is based on the anatomy of each animal in a standard way. For humans, one type of vertebrate, anatomical terms may differ from other forms of vertebrates. For one reason, this is because humans have a different neuraxis and, unlike animals that rest on four limbs, humans are considered when describing anatomy as being in the standard anatomical position, thus what is on "top" of a human is the head, whereas the "top" of a dog may be its back, the "top" of a flounder could refer to either its left or its right side. For invertebrates, standard application of locational terminology becomes difficult or debatable at best when the differences in morphology are so radical that common concepts are not homologous and do not refer to common concepts. For example, many species are not bilaterally symmetrical. In these species, terminology depends on their type of symmetry.
Because animals can change orientation with respect to their environment, because appendages like limbs and tentacles can change position with respect to the main body, positional descriptive terms need to refer to the animal as in its standard anatomical position. All descriptions are with respect to the organism in its standard anatomical position when the organism in question has appendages in another position; this helps avoid confusion in terminology. In humans, this refers to the body in a standing position with arms at the side and palms facing forward. While the universal vertebrate terminology used in veterinary medicine would work in human medicine, the human terms are thought to be too well established to be worth changing. Many anatomical terms can be combined, either to indicate a position in two axes or to indicate the direction of a movement relative to the body. For example, "anterolateral" indicates a position, both anterior and lateral to the body axis. In radiology, an X-ray image may be said to be "anteroposterior", indicating that the beam of X-rays pass from their source to patient's anterior body wall through the body to exit through posterior body wall.
There is no definite limit to the contexts in which terms may be modified to qualify each other in such combinations. The modifier term is truncated and an "o" or an "i" is added in prefixing it to the qualified term. For example, a view of an animal from an aspect at once dorsal and lateral might be called a "dorsolateral" view. Again, in describing the morphology of an organ or habitus of an animal such as many of the Platyhelminthes, one might speak of it as "dorsiventrally" flattened as opposed to bilaterally flattened animals such as ocean sunfish. Where desirable three or more terms may be agglutinated or concatenated, as in "anteriodorsolateral"; such terms sometimes used to be hyphenated. There is however little basis for any strict rule to interfere with choice of convenience in such usage. Three basic reference planes are used to describe location; the sagittal plane is a plane parallel to the sagittal suture. All other sagittal planes are parallel to it, it is known as a "longitudinal plane".
The plane is perpendicular to the ground. The median plane or midsagittal plane is in the midline of the body, divides the body into left and right portions; this passes through the head, spinal cord, and, in many animals, the tail. The term "median plane" can refer to the midsagittal plane of other structures, such as a digit; the frontal plane or coronal plane divides the body into ventral portions. For post-embryonic humans a coronal plane is vertical and a transverse plane is horizontal, but for embryos and quadrupeds a coronal plane is horizontal and a transverse plane is vertical. A longitudinal plane is any plane perpendicular to the transverse plane; the coronal plane and the sagittal plane are examples of longitudinal planes. A transverse plane known as a cross-section, divides the body into cranial and caudal portions. In human anatomy: A transverse plane is an X-Z plane, parallel to the ground, which s
Ammonoids are an extinct group of marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs referred to as ammonites, are more related to living coleoids than they are to shelled nautiloids such as the living Nautilus species; the earliest ammonites appear during the Devonian, the last species died out in the Cretaceous–Paleogene extinction event. Ammonites are excellent index fossils, it is possible to link the rock layer in which a particular species or genus is found to specific geologic time periods, their fossil shells take the form of planispirals, although there were some helically spiraled and nonspiraled forms. The name "ammonite", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble coiled rams' horns. Pliny the Elder called fossils of these animals ammonis cornua because the Egyptian god Ammon was depicted wearing ram's horns; the name of an ammonite genus ends in -ceras, Greek for "horn".
Ammonites can be distinguished by their septa, the dividing walls that separate the chambers in the phragmocone, by the nature of their sutures where the septa joint the outer shell wall, in general by their siphuncles. Ammonoid septa characteristically have bulges and indentations and are to varying degrees convex from the front, distinguishing them from nautiloid septa which are simple concave dish-shaped structures; the topology of the septa around the rim, results in the various suture patterns found. Three major types of suture patterns are found in the Ammonoidea: Goniatitic - numerous undivided lobes and saddles; this pattern is characteristic of the Paleozoic ammonoids. Ceratitic - lobes have subdivided tips, giving them a saw-toothed appearance, rounded undivided saddles; this suture pattern is characteristic of Triassic ammonoids and appears again in the Cretaceous "pseudoceratites". Ammonitic - lobes and saddles are much subdivided. Ammonoids of this type are the most important species from a biostratigraphical point of view.
This suture type is characteristic of Jurassic and Cretaceous ammonoids, but extends back all the way to the Permian. The siphuncle in most ammonoids is a narrow tubular structure that runs along the shell's outer rim, known as the venter, connecting the chambers of the phragmocone to the body or living chamber; this distinguishes them from living nautiloides and typical Nautilida, in which the siphuncle runs through the center of each chamber. However the earliest nautiloids from the Late Cambrian and Ordovician had ventral siphuncles like ammonites, although proportionally larger and more internally structured; the word "siphuncle" comes from the New Latin siphunculus, meaning "little siphon". Originating from within the bactritoid nautiloids, the ammonoid cephalopods first appeared in the Devonian and became extinct at the close of the Cretaceous along with the dinosaurs; the classification of ammonoids is based in part on the ornamentation and structure of the septa comprising their shells' gas chambers.
While nearly all nautiloids show curving sutures, the ammonoid suture line is variably folded, forming saddles and lobes. The Ammonoidea can be divided into six orders, listed here starting with the most primitive and going to the more derived: Agoniatitida, Lower Devonian - Middle Devonian Clymeniida, Upper Devonian Goniatitida, Middle Devonian - Upper Permian Prolecanitida, Upper Devonian - Upper Triassic Ceratitida, Upper Permian - Upper Triassic Ammonitida, Lower Jurassic - Upper CretaceousIn some classifications, these are left as suborders, included in only three orders: Goniatitida and Ammonitida; the Treatise on Invertebrate Paleontology divides the Ammonoidea, regarded as an order, into eight suborders, the Anarcestina, Clymeniina and Prolecanitina from the Paleozoic. In subsequent taxonomies, these are sometimes regarded as orders within the subclass Ammonoidea; because ammonites and their close relatives are extinct, little is known about their way of life. Their soft body parts are rarely preserved in any detail.
Nonetheless, much has been worked out by examining ammonoid shells and by using models of these shells in water tanks. Many ammonoids lived in the open water of ancient seas, rather than at the sea bottom, because their fossils are found in rocks laid down under conditions where no bottom-dwelling life is found. Many of them are thought to have been good swimmers, with flattened, discus-shaped, streamlined shells, although some ammonoids were less effective swimmers and were to have been slow-swimming bottom-dwellers. Synchrotron analysis of an aptychophoran ammonite revealed remains of isopod and mollusc larvae in its buccal cavity, indicating at least this kind of ammonite fed on plankton, they may have avoided predation by squirting ink, much like modern cephalopods. The soft body of the creature occupied the largest segments of the shell at the end of the coil; the smaller earlier segments were walled off and the animal could maintain its buoyancy by filling them with gas. Thus, the smaller sections of the coil would have floated ab
Theropoda or theropods are a dinosaur suborder, characterized by hollow bones and three-toed limbs. They are classed as a group of saurischian dinosaurs, although a 2017 paper has instead placed them in the proposed clade Ornithoscelida as the closest relatives of the Ornithischia. Theropods were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago and included the sole 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, are today represented by about 10,500 living species. Theropods exhibit a wide range of diets, from insectivores to carnivores. Strict carnivory has always been considered the ancestral diet for theropods as a group, a wider variety of diets was considered a characteristic exclusive to the avian theropods.
However, discoveries in the late 20th and early 21st centuries showed that a variety of diets existed in more basal lineages. All early finds of theropod fossils showed them to be carnivorous. Fossilized specimens of early theropods known to scientists in the 19th and early 20th centuries all possessed sharp teeth with serrated edges for cutting flesh, some specimens showed direct evidence of predatory behavior. For example, a Compsognathus longipes fossil was found with a lizard in its stomach, a Velociraptor mongoliensis specimen was found locked in combat with a Protoceratops andrewsi; the first confirmed non-carnivorous fossil theropods found were the therizinosaurs known as segnosaurs. First thought to be prosauropods, these enigmatic dinosaurs were proven to be specialized, herbivorous theropods. Therizinosaurs possessed large abdomens for processing plant food, small heads with beaks and leaf-shaped teeth. Further study of maniraptoran theropods and their relationships showed that therizinosaurs were not the only early members of this group to abandon carnivory.
Several other lineages of early maniraptors show adaptations for an omnivorous diet, including seed-eating and insect-eating. Oviraptorosaurs and advanced troodontids were omnivorous as well, some early theropods appear to have specialized in catching fish. Diet is deduced by the tooth morphology, tooth marks on bones of the prey, gut contents; some theropods, such as Baryonyx, Lourinhanosaurus and birds, are known to use gastroliths, or gizzard-stones. The majority of theropod teeth are blade-like, with serration on the edges, called ziphodont. Others are phyllodont depending on the shape of the tooth or denticles; the morphology of the teeth is distinct enough to tell the major families apart, which indicate different diet strategies. An investigation in July 2015 discovered that what appeared to be "cracks" in their teeth were folds that helped to prevent tooth breakage by strengthening individual serrations as they attacked their prey; the folds helped the teeth stay in place longer as theropods evolved into larger sizes and had more force in their bite.
Mesozoic theropods were very diverse in terms of skin texture and covering. Feathers or feather-like structures are attested in most lineages of theropods.. However, outside the coelurosaurs, feathers may have been confined to the young, smaller species, or limited parts of the animal. Many larger theropods had skin covered in bumpy scales. In some species, these osteoderms; this type of skin is best known in the ceratosaur Carnotaurus, preserved with extensive skin impressions. The coelurosaur lineages most distant from birds had feathers that were short and composed of simple branching filaments. Simple filaments are seen in therizinosaurs, which possessed large, stiffened "quill"-like feathers. More feathered theropods, such as dromaeosaurs retain scales only on the feet; some species may have mixed feathers elsewhere on the body as well. Scansoriopteryx preserved scales near the underside of the tail, Juravenator may have been predominantly scaly with some simple filaments interspersed. On the other hand, some theropods were covered with feathers, such as the troodontid Anchiornis, which had feathers on the feet and toes.
Tyrannosaurus was for many decades the largest known best-known to the general public. Since its discovery, however, a number of other giant carnivorous dinosaurs have been described, including Spinosaurus, Carcharodontosaurus, Giganotosaurus; the original Spinosaurus specimens support the idea that Spinosaurus is longer than Tyrannosaurus, showing that Spinosaurus was 3 meters longer than Tyrannosaurus though Tyrannosaurus could still be taller than Spinosaurus. There is still no clear explanation for why these animals grew so much larger than the land predators that came before and after them; the largest extant theropod is the common ostrich, up to 2.74 m tall and weighing between 63.5 and 145.15 kg. The smallest non-avialan theropod known from adult specimens is the troodontid Anchiornis huxleyi, at 110 grams in weight and 34 centimeters in length; when modern birds are included, the bee hummingbird Mellisuga helenae is sm
2018 in paleontology
Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, burrows, cast-off parts, fossilised feces and chemical residues; because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 2018. New three dimensionally phosphatized microfossils of coronate scyphozoan Qinscyphus necopinus, including a new type of fossil embryo, are described from the Cambrian Kuanchuanpu Formation by Shao et al. who interpret their findings as indicating that Qinscyphus underwent direct development. A study on the morphology of the conulariid species Carinachites spinatus based on a new specimen collected from the lower Cambrian Kuanchuanpu Formation is published by Han et al.. Revision of stony corals from the Lower Cretaceous Oehrli Formation is published by Baron-Szabo, who compares this fauna with five additional Berriasian coral faunas.
Studies on the ontogenetic development of early acrotretoid brachiopods based on well preserved specimens of the earliest Cambrian species Eohadrotreta zhenbaensis and Eohadrotreta? zhujiahensis from the Shuijingtuo Formation are published by Zhang et al.. A study on the extinction and origination of members of the order Strophomenida during the Late Ordovician mass extinction is published by Sclafani et al.. A study on the body size of several brachiopod assemblages recorded into the extinction interval prior to the Toarcian turnover, collected from representative localities around the Iberian Massif, is published by García Joral, Baeza-Carratalá & Goy. A study testing the proposed models of growth of conodont elements is published by Shirley et al.. A study on the histological sections of Ordovician and Permian conodont dental elements from the Bell Canyon Formation, Harding Sandstone, Ali Bashi Formation and Canadian Arctic, examining those fossils for the presence and distribution of soft tissue biomarkers, is published by Terrill, Henderson & Anderson.
A study evaluating the δ18O variation within a species-rich conodont assemblage from the Ordovician Factory Cove Member of the Shallow Bay Formation, Cow Head Group, as well as assessing the implications of these data for determining the paleothermometry of ancient oceans and conodont ecologic models, is published by Wheeley et al.. A study on the body size and diversity of Carnian conodonts from South China and their implications for inferring the biotic and environmental changes during the Carnian Pluvial Event is published by Zhang et al.. A study assessing the similarity of late Paleozoic to Triassic conodont faunas known from the Cache Creek Terrane is published by Golding. Reconstruction of the multi-element apparatus of the Middle Triassic conodont from British Columbia belonging to the Neogondolella regalis group within the genus Neogondolella is presented by Golding. Reconstruction of the number and arrangement of elements in the apparatus of Hindeodus parvus published by Zhang et al. is criticized by Agematsu, Golding & Orchard.
A cluster of icriodontid conodonts belonging to the species Caudicriodus woschmidti, providing new information on the apparatus structure of icriodontid conodonts, is described from the Lower Devonian sediments in southern Burgenland by Suttner, Kido & Briguglio. A study on the species belonging to the genus Neognathodus, evaluating whether defined morphotype groups are reliably distinct from one another, is published by Zimmerman, Johnson & Polly. Evidence from multi-stable isotope data indicating that some Devonian vertebrates, including early tetrapods, were euryhaline and inhabited aquatic environments subject to rapid changes in salinity is presented by Goedert et al.. A study on the evolution of forelimb musculature from the lobe-finned fish to early tetrapods is published by Molnar et al.. A partial jaw resembling that of Crassigyrinus is described from the Tournaisian of Scotland by Clack, Porro & Bennett extending the existence of the genus by 20 million years towards the base of the Carboniferous.
A study on the fossil record of amphibians, aiming to identify traits that influenced the extinction risk of species, using this data to predict the extinction risk for living amphibian species, is published by Tietje & Rödel. Description of anamniote tetrapod fossils from the Late Permian Sundyr Tetrapod Assemblage is published by Golubev & Bulanov. A study on the relationship between taxonomic and ecological diversity of temnospondyls across the Permian–Triassic boundary in the Karoo Basin of South Africa is published by Tarailo. A study on the morphology and phylogenetic relationships of Neldasaurus is published by Schoch. A study on the morphological changes in the skull that have been considered related to size reduction in dissorophoids, evaluating whether these changes are consistent with the consequences of miniaturization according to the studies in extant miniature amphibians, is published by Pérez-Ben, Schoch & Báez. A study on the phylogenetic relationships of dissorophoid temnospondyls, on their relationship to modern amphibians, is publishe
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype. Under the International Code of Zoological Nomenclature, a holotype is one of several kinds of name-bearing types. In the International Code of Nomenclature for algae and plants and ICZN the definitions of types are similar in intent but not identical in terminology or underlying concept. For example, the holotype for the butterfly Lycaeides idas longinus is a preserved specimen of that species, held by the Museum of Comparative Zoology at Harvard University. An isotype is a duplicate of the holotype and is made for plants, where holotype and isotypes are pieces from the same individual plant or samples from the same gathering. A holotype is not "typical" of that taxon, although ideally it should be. Sometimes just a fragment of an organism is the holotype in the case of a fossil.
For example, the holotype of Pelorosaurus humerocristatus, a large herbivorous dinosaur from the early Jurassic period, is a fossil leg bone stored at the Natural History Museum in London. If a better specimen is subsequently found, the holotype is not superseded. Under the ICN, an additional and clarifying type could be designated an epitype under Article 9.8, where the original material is demonstrably ambiguous or insufficient. A conserved type is sometimes used to correct a problem with a name, misapplied. In the absence of a holotype, another type may be selected, out of a range of different kinds of type, depending on the case, a lectotype or a neotype. For example, in both the ICN and the ICZN a neotype is a type, appointed in the absence of the original holotype. Additionally, under the ICZN the Commission is empowered to replace a holotype with a neotype, when the holotype turns out to lack important diagnostic features needed to distinguish the species from its close relatives. For example, the crocodile-like archosaurian reptile Parasuchus hislopi Lydekker, 1885 was described based on a premaxillary rostrum, but this is no longer sufficient to distinguish Parasuchus from its close relatives.
This made. Texan paleontologist Sankar Chatterjee proposed that a new type specimen, a complete skeleton, be designated; the International Commission on Zoological Nomenclature considered the case and agreed to replace the original type specimen with the proposed neotype. The procedures for the designation of a new type specimen when the original is lost come into play for some recent, high-profile species descriptions in which the specimen designated as the holotype was a living individual, allowed to remain in the wild. In such a case, there is no actual type specimen available for study, the possibility exists that—should there be any perceived ambiguity in the identity of the species—subsequent authors can invoke various clauses in the ICZN Code that allow for the designation of a neotype. Article 75.3.7 of the ICZN requires that the designation of a neotype must be accompanied by "a statement that the neotype is, or upon publication has become, the property of a recognized scientific or educational institution, cited by name, that maintains a research collection, with proper facilities for preserving name-bearing types, that makes them accessible for study", but there is no such requirement for a holotype.
Type Allotype Paratype Type species Genetypes- genetic sequence data from type specimens. BOA Photographs of type specimens of Neotropical Rhopalocera