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23-457: Coeluridae is a historically unnatural group of generally small, carnivorous dinosaurs from the late Jurassic Period . For many years, any small Jurassic or Cretaceous theropod that did not belong to one of the more specialized families recognized at the time was classified with the coelurids, creating a confusing array of 'coelurid' theropods that were not closely related. Although they have been traditionally included in this family, there

46-475: A cladistic analysis, found Coeluridae to include Coelurus ( Late Jurassic , North America), Compsognathus (Late Jurassic, Europe), Sinosauropteryx ( Early Cretaceous , Asia) and an unnamed Compsognathus -like form (Early Cretaceous, South America; this dinosaur has since been placed in the new genus Mirischia ). Rauhut considered coelurids to be a monophyletic group of basal coelurosaurs , characterized by evolutionary reversals in some aspects of

69-453: A node-based clade definition , for example, could be "All descendants of the last common ancestor of species X and Y". On the other hand, polyphyletic groups can be delimited as a conjunction of several clades, for example "the flying vertebrates consist of the bat, bird, and pterosaur clades". From a practical perspective, grouping species monophyletically facilitates prediction far more than does polyphyletic grouping. For example, classifying

92-415: A basal therizinosaur ), and Migmanychion . The results of his phylogenetic analysis are displayed in the cladogram below: Vayuraptor Shishugounykus Phuwiangvenator Coelurus Migmanychion Fukuivenator Ornitholestes Maniraptoriformes [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Polyphyletic For example,

115-491: A common phenomenon in nature, particularly in plants where polyploidy allows for rapid speciation. Some cladist authors do not consider species to possess the property of "-phyly", which they assert applies only to groups of species. Warm-blooded Warm-blooded is an informal term referring to animal species whose bodies maintain a temperature higher than that of their environment. In particular, homeothermic species (including birds and mammals ) maintain

138-529: A higher basal metabolic rate and can further increase their metabolic rate during strenuous activity. They usually have well-developed insulation in order to retain body heat: fur and blubber in the case of mammals and feathers in birds. When this insulation is insufficient to maintain body temperature, they may resort to shivering —rapid muscle contractions that quickly use up ATP, thus stimulating cellular metabolism to replace it and consequently produce more heat. Additionally, almost all eutherian mammals (with

161-421: A newly discovered grass in the monophyletic family Poaceae , the true grasses, immediately results in numerous predictions about its structure and its developmental and reproductive characteristics, that are synapomorphies of this family. In contrast, Linnaeus' assignment of plants with two stamens to the polyphyletic class Diandria, while practical for identification, turns out to be useless for prediction, since

184-609: A stable body temperature by regulating metabolic processes. Other species have various degrees of thermoregulation . As there are more than two categories of temperature control utilized by animals, the terms warm-blooded and cold-blooded have been deprecated in the scientific field. In general, warm-bloodedness refers to three separate categories of thermoregulation . A significant proportion of creatures commonly referred to as "warm-blooded," like birds and mammals, exhibit all three of these categories (i.e., they are endothermic, homeothermic, and tachymetabolic). However, over

207-496: Is generated by metabolism . This relates to the chemical reaction in cells that break down glucose into water and carbon dioxide , thereby producing adenosine triphosphate (ATP), a high-energy compound used to power other cellular processes. Muscle contraction is one such metabolic process generating heat energy, and additional heat results from friction as blood circulates through the vascular system. All organisms metabolize food and other inputs, but some make better use of

230-408: Is no evidence that any of these primitive coelurosaurs form a natural group with Coelurus , the namesake of Coeluridae, to the exclusion of other traditional coelurosaur groups. Before the use of phylogenetic analyses, Coeluridae and Coelurosauria were taxonomic wastebaskets used for small theropods that did not belong to other groups; thus, they accumulated many dubious genera. As late as

253-465: Is often included, support for this relationship has been weak in most of the studies that recovered it. In 2024, Cau recovered Coeluridae as the basalmost family of maniraptoromorphs , including few of its traditional members; in addition to Coelurus , it contains Shishugounykus (traditionally a basal alvarezsaur ), Phuwiangvenator and Vayuraptor (sometimes considered to be early megaraptorans ), Fukuivenator (sometimes considered to be

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276-583: Is often the stimulus for major revisions of the classification schemes. Researchers concerned more with ecology than with systematics may take polyphyletic groups as legitimate subject matter; the similarities in activity within the fungus group Alternaria , for example, can lead researchers to regard the group as a valid genus while acknowledging its polyphyly. In recent research, the concepts of monophyly, paraphyly, and polyphyly have been used in deducing key genes for barcoding of diverse groups of species. The term polyphyly , or polyphyletic , derives from

299-440: The 1980s, popular books recognized over a dozen "coelurids", including such disparate forms as the noasaurid Laevisuchus and the oviraptorosaurian Microvenator , and considered them descendants of the coelophysids . A wastebasket Coeluridae lingered into the early 1990s in some sources (and appears in at least one 2006 source) but since then it has only been recognized in a much reduced form. In 2003, O.W.M. Rauhut, using

322-444: The biological characteristic of warm-bloodedness evolved separately in the ancestors of mammals and the ancestors of birds; "warm-blooded animals" is therefore a polyphyletic grouping. Other examples of polyphyletic groups are algae , C4 photosynthetic plants , and edentates . Many taxonomists aim to avoid homoplasies in grouping taxa together, with a goal to identify and eliminate groups that are found to be polyphyletic. This

345-432: The fact that a monophyletic group includes organisms consisting of all the descendants of a unique common ancestor. By comparison, the term paraphyly , or paraphyletic , uses the ancient Greek preposition παρά ( pará ) 'beside, near', and refers to the situation in which one or several monophyletic subgroups are left apart from all other descendants of a unique common ancestor. In many schools of taxonomy ,

368-649: The only known exception of swine ) have brown adipose tissue whose mitochondria are capable of non-shivering thermogenesis . This process involves the direct dissipation of the mitochondrial gradient as heat via an uncoupling protein , thereby "uncoupling" the gradient from its usual function of driving ATP production via ATP synthase . In warm environments, these animals employ evaporative cooling to shed excess heat, either through sweating (some mammals) or by panting (many mammals and all birds)—mechanisms generally absent in poikilotherms. It has been hypothesized that warm-bloodedness evolved in mammals and birds as

391-443: The output than others. Like all energy conversions, metabolism is rather inefficient, and around 60% of the available energy is converted to heat rather than to ATP. In most organisms, this heat dissipates into the surroundings. However, endothermic homeotherms (generally referred to as "warm-blooded" animals) not only produce more heat but also possess superior means of retaining and regulating it compared to other animals. They exhibit

414-514: The past three decades, investigations in the field of animal thermophysiology have unveiled numerous species within these two groups that do not meet all these criteria. For instance, many bats and small birds become poikilothermic and bradymetabolic during sleep (or, in nocturnal species, during the day). For such creatures, the term heterothermy was introduced. Further examinations of animals traditionally classified as cold-blooded have revealed that most creatures manifest varying combinations of

437-400: The presence of exactly two stamens has developed convergently in many groups. Species have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification. It is usually implicitly assumed that species are monophyletic (or at least paraphyletic ). However, hybrid speciation arguably leads to polyphyletic species. Hybrid species are

460-494: The recognition of polyphyletic groups in a classification is discouraged. Monophyletic groups (that is, clades ) are considered by these schools of thought to be the only valid groupings of organisms because they are diagnosed ("defined", in common parlance) on the basis of synapomorphies , while paraphyletic or polyphyletic groups are not. From the perspective of ancestry, clades are simple to define in purely phylogenetic terms without reference to clades previously introduced:

483-555: The three aforementioned terms, along with their counterparts (ectothermy, poikilothermy, and bradymetabolism), thus creating a broad spectrum of body temperature types. Some fish have warm-blooded characteristics, such as the opah . Swordfish and some sharks have circulatory mechanisms that keep their brains and eyes above ambient temperatures and thus increase their ability to detect and react to prey . Tunas and some sharks have similar mechanisms in their muscles, improving their stamina when swimming at high speed. Body heat

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506-405: The two Ancient Greek words πολύς ( polús ) 'many, a lot of', and φῦλον ( phûlon ) 'genus, species', and refers to the fact that a polyphyletic group includes organisms (e.g., genera, species) arising from multiple ancestral sources. Conversely, the term monophyly , or monophyletic , employs the ancient Greek adjective μόνος ( mónos ) 'alone, only, unique', and refers to

529-710: The vertebrae to the more primitive theropod condition. However, he and other authors have not since found this result. Phil Senter proposed in 2007 that Coelurus and Tanycolagreus were the only coelurids, and were actually tyrannosauroids . Coeluridae received a formal phylogenetic definition in 2015, when it was defined as all species more closely related to Coelurus fragilis than to Proceratosaurus bradleyi , Tyrannosaurus rex , Allosaurus fragilis , Compsognathus longipes , Ornithomimus edmontonicus , or Deinonychus antirrhopus by Hendrickx, Hartman and Mateus. It remains unclear whether or not this group contains any species other than Coelurus itself, and while Tanycolagreus

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