Nomina dubia

term used in taxonomy to indicate a scientific name is of unknown or questionable authority

Protoavis (meaning "first bird") is a problematic taxon known from fragmentary remains from Late Triassic Norian stage deposits near Post, Texas. The animal's true classification has been the subject of much controversy, and there are many different interpretations of what the taxon actually is. When it was first described, the fossils were described as being from a primitive bird which, if the identification is valid, would push back avian origins some 60–75 million years.

species of mammal

Mauisaurus ("Māui lizard") is a dubious genus of plesiosaur that lived during the Late Cretaceous period in what is now New Zealand. Numerous specimens have been attributed to this genus in the past, but a 2017 paper restricts Mauisaurus to the lectotype and declares it a nomen dubium.

Pristichampsus (from , 'saw' and , 'crocodile') is a non-diagnostic and potentially dubious extinct genus of crocodylian from France and possibly also Kazakhstan that is part of the monotypic Pristichampsidae family. As the type species, Pristichampsus rollinatii, was based on insufficient material when described in 1831 and 1853, the taxonomic status of the genus is in doubt, and other species have been referred to other genera, primarily Boverisuchus.

Actiosaurus (meaning "coast lizard") is an extinct genus of reptile first described by Henri Sauvage in 1883 from Antully bonebed, Autun (Triassic of France). The type species is A. gaudryi (commonly misspelled A. gaudrii after Boulenger). Little is known of it, and it is considered a nomen dubium. Actiosaurus was originally described as a dinosaur in 1883 and was reinterpreted as an ichthyosaur in 1908. Actiosaurus may instead represent the remains of a choristodere. Fischer et al. (2014) considered A. gaudryi to be a species inquirenda, and noted the similarity of its bones to the limb bones

Trachodon (meaning "rough tooth") is a dubious genus of hadrosaurid dinosaur based on teeth from the Campanian-aged (Upper Cretaceous) Judith River Formation of Montana, U.S. It is a historically important genus with a convoluted taxonomy that has been all but abandoned by modern dinosaur paleontologists. Despite being used for decades as the iconic hadrosaurid dinosaur, the material it is based on is composed of teeth from both hadrosaurids and ceratopsids (their teeth have a distinctive double root), and its describer, Joseph Leidy, came to recognize the difference and suggested limiting the

Polyptychodon (meaning 'many-folded tooth') is a genus of pliosaurid found in Middle-Late Cretaceous marine deposits in southern England, France and Argentina. It has been considered a nomen dubium in a 2016 review.

Mesotardigrada is one of three classes of tardigrades, consisting of a single species, Thermozodium esakii. The animal reportedly has six claws of equal length at each foot. This species was described in 1937 by German zoologist Gilbert Rahm from a hot spring near Nagasaki, Japan. The inability of taxonomists to replicate Rahm's finding has cast doubt on the accuracy of the description, making T. esakii, and by extension the entire class Mesotardigrada, a taxon inquirendum.

Regnosaurus (meaning "Sussex lizard") is an extinct genus of herbivorous presumably armored dinosaur known from the early Cretaceous Wealden Formation of England. The genus contains a single species, Regnosaurus northamptoni, known from a single partial jaw bone. Regnosaurus has traditionally been regarded as a stegosaur, possibly related to the Jurassic Huayangosaurus of China. Later research considers it to be a dubious, indeterminate thyreophoran.

Nopcsaspondylus (meaning "Nopcsa's vertebra", in reference to the original describer) is a dubious genus of rebbachisaurid sauropod dinosaur from the Cenomanian-aged (Upper Cretaceous) Candeleros Formation of Neuquén, Argentina. It is based on a now-lost back vertebra described by Nopcsa in 1902 but not named at the time. The specimen had a small vertebral body and large hollows, now known to be typical of rebbachisaurids.

Avipes (meaning "bird foot") is a genus of extinct archosaurs represented by the single species Avipes dillstedtianus, which lived during the middle Triassic period. The only known fossil specimen, a partial foot (metatarsals), was found in Bedheim, Thuringia, Germany, in deposits of Lettenkohlensandstein (a form of sandstone). Avipes was named in 1932 by Huene. Although originally classified as a coelurosaur or a ceratosaur, a new study of the fossil specimen found that it was too incomplete to assign to a group more specific than Archosauria, and so it was regarded as indeterminate by Rauhut

Steneosaurus (from , 'narrow' and , 'lizard') is a dubious genus of teleosaurid crocodyliform from the Middle or Late Jurassic (Callovian or early Oxfordian) of France and possibly also India. The genus has been used as a wastebasket taxon for thalattosuchian fossils for over two centuries, and almost all known historical species of teleosauroid have been included within it at one point. The genus has remained a wastebasket, with numerous species still included under the label '''Steneosaurus''', many of which are unrelated to each other (either paraphyletic or polyphyletic with respect to eac

Mandschurosaurus (meaning "lizard from Manchuria") is an extinct genus of hadrosaurids based on material from the Late Cretaceous of China and possibly also the Early Cretaceous of Laos. It was the first dinosaur genus named from China.

species of arachnid

Halitherium is a dubious genus of extinct dugongid sea cow that arose in the late Eocene, then became extinct during the early Oligocene. Its fossils are common in European shales. Inside its flippers were finger bones that did not stick out. Halitherium also had the remnants of back legs, which did not show externally. However, it did have a basic femur, joined to a reduced pelvis. Halitherium also had elongated ribs, presumably to increase lung capacity to provide fine control of buoyancy.

Scaldicetus is an extinct genus of highly predatory macroraptorial sperm whale. Although widely used for a number of extinct physeterids with primitive dental morphology consisting of enameled teeth, Scaldicetus as generally recognized appears to be a wastebasket taxon filled with more-or-less unrelated primitive sperm whales.

species of fish

Calamospondylus (meaning "reed vertebrae") is a dubious genus of theropod dinosaur. It lived during the Early Cretaceous and its fossils were found on the Isle of Wight in southern England. The type species is C. oweni, named in 1866 in an anonymous publication written largely by its discoverer, the Reverend William Fox. The description given by Fox was brief and listed no unique diagnostic characteristics; between this and the fact that the specimen has been lost, C. oweni is now considered a nomen dubium. The presence of expansive hollows in the bone led Fox to speculate that it was arboreal

species of arachnid

dubious species of animal

Salinella salve is a dubious species of a very simple animal which some have named as the sole member of the phylum Monoblastozoa. It was discovered in 1892 by Johannes Frenzel in the salt pans of Córdoba Province, Argentina and cultivated in a laboratory by him. This animal has not been found since and its real existence is considered as doubtful. A project involving Michael Schrödl from the Zoological State Collection in Munich searched for Salinella in salt lakes across Argentina and Chile, but failed to find any specimens.

Taveirosaurus (meaning "Taveiro lizard") is a genus of possibly eutriconodontan mammal from the Late Cretaceous Argilas de Aveiro Formation of Portugal, and also Laño, Spain. The genus is based solely on teeth, and the type species is T. costai.

Discosaurus is an extinct genus of plesiosaur from the Santonian of Alabama and Mississippi. One species is known, which is D. vestutus.

species of sponge

Macrodontophion (meaning "long-toothed snake") is the name given to a dubious genus of lophotrochozoan from the Early Devonian Dniester Series of Podolia, Ukraine. It was described by Adalbert Zborzewsky in 1834, but was never given a species epithet, and is considered a nomen dubium, because it is based only on fragments, such as the holotype, a shell of .

Ponerosteus is a dubious genus of extinct archosauromorph from the Late Cretaceous (Cenomanian-aged) Korycanar Formation of the Czech Republic that was initially identified as a species of the dinosaur Iguanodon.

species of amphibian

species of arachnid

species of arachnid

species of insect

Liaoxiornis is a dubious genus of enantiornithean bird. The only named species is Liaoxiornis delicatus, described by Hou and Chen in 1999. Because the species was named for a hatchling specimen, it cannot be matched with adult specimens, and so it is impossible to determine which, if any, birds from the same rocks represent adults of this species. Luis Chiappe and colleagues therefore regarded it as a nomen vanum ("empty name") or at least a nomen dubium, and recommended that use of the name be abandoned. thumb|left|Fossil of Liaoxiornis delicatus, at Museo di Storia Naturale di Venezia, Veni

species of ant endemic to Australia

species of insect

species of insect

Termatosaurus ("End Lizard", due to its appearance in the End Triassic) is a potentially dubious genus of archosaur known from several tooth specimens. Its remains come from the Upper Triassic of France, England, Germany and Switzerland.

species of insect

Uronautes is an extinct genus of rhomaleosaurid plesiosaur from the Late Cretaceous Fox Hills Formation of the United States. The type species is U. cetiformis.

Centemodon (meaning "point tooth") is an extinct genus of basal phytosaur from the Late Triassic Period. It lived in what is now Pennsylvania, United States. It is classified as a nomen dubium. It was found in the Red Sandstone Formation near the Schuyklill River. Centemodon may have been related to Suchoprion. It was a small phytosaur, weighing no more than when fully grown.

Fayella is an extinct genus of dubious temnospondyl from the Early Permian (Guadalupian) of Oklahoma.

Scymnosaurus is a dubious genus of therocephalian therapsids from the Middle Permian of what is now South Africa based upon the fossils of large, but indeterminate, early therocephalians. The genus and its type species S. ferox was named by Robert Broom in 1903, followed by S. watsoni in 1915. A third species, S. major, was named by Lieuwe Dirk Boonstra in 1954, who also referred many more specimens to the genus as Scymnosaurus sp.

Charruodon is an extinct genus of cynodonts which existed in the Hyperodapedon Assemblage Zone of the Santa Maria Formation in the Paraná Basin in southeastern Brazil during the Late Triassic. The genus contains only the type species Charruodon tetracuspidatus, which is known from a single specimen of uncertain provenance. Upon its first description, Charruodon was tentatively placed within the family Therioherpetidae, but a 2017 study by Agustín G. Martinelli and colleagues instead recovered it as a more basal member of Probainognathia. In 2023, Hoffmann, Ribeiro & de Andrade reinterpreted th

Trochosaurus (from , 'badger' and , 'lizard') is a dubious genus of therocephalian therapsid from South Africa, to which various species were once assigned. The genus was based upon multiple weathered and distorted fossils of therocephalians of the family Lycosuchidae. Like other lycosuchids, specimens placed in Trochosaurus have only five large incisors in each premaxilla, seemingly two functional "double canines" in each maxilla (of which the second was supposedly slightly larger in Trochosaurus), and few postcanines. However, the fossils lack any further diagnostic traits to justify referri

Brimosaurus (meaning "strong lizard") is an extinct genus of plesiosaur from the Late Cretaceous of what is now Arkansas. The type species is Brimosaurus grandis, first named by Joseph Leidy in 1854. The name Brimosaurus is a nomen dubium: the fossils consist of only a few isolated vertebrae, and in 1952 Welles proposed that Brimosaurus was actually synonymous with Cimoliasaurus (which itself is based on dubious material).

subspecies of fish

Phytosaurus (meaning "plant lizard") is a dubious genus of extinct parasuchid phytosaur found in an outcrop of the Keuper (likely the Exter Formation) in Germany. Phytosaurus was the first phytosaur to be described, being done so by Georg Friedrich von Jaeger in 1828. The type species is P. cylindricodon and a second species, P. cubicodon, is also known.

species of insect

Parvibellus is an extinct genus of panarthropod animal known from the Cambrian of China. It is known from only a single species, P. atavus, found in the Cambrian Stage 3 aged Chengjiang Biota of Yunnan, China.

Barracudasaurus is a dubious genus of ichthyosaur from the Triassic of China, containing the single species B. maotaiensis.

Dianchungosaurus (meaning "Dianchung lizard") is an extinct genus of mesoeucrocodylian crocodyliform from the Early Jurassic of China. It was previously considered a dinosaur, but it was recently reclassified as a mesoeucrocodylian by Paul Barrett and Xing Xu (2005). It is probably the same animal as the informally named "Tianchungosaurus". The type species is D. lufengensis and it was described in 1982. A second species, D. elegans, was named in 1986, but it has since become a synonym of the type species.

Rachitrema is a poorly known genus of ichthyosaur from the Triassic of France. Its remains were found in France by two independent collectors, towards the end of the nineteenth century. They were only isolated bone fragments.

species of Amphibia

thumb|left|A skeleton of Cricotus crassidens (specimen AMNH 4550) thumb|left|Detail of the skull and limbs of AMNH 4550 thumb|left|Illustration of the skull and ventral scutes of Cricotus heteroclitus by Edward Drinker Cope.

Utahdactylus was a genus of extinct reptile from the Kimmeridgian-Tithonian-age Upper Jurassic Morrison Formation of Utah, United States. Based on DM 002/CEUM 32588 (an incomplete skeleton described as including a fragment of the skull, a cervical vertebra, three back vertebrae, and a caudal vertebra, ribs, a scapula, coracoid, and limb bones), Czerkas and Mickelson (2002) identified it as a "rhamphorhynchoid" pterosaur. Bennett (2007) later concluded that it has no diagnostic features of the Pterosauria, and cannot be positively identified beyond being an indeterminate diapsid. More recent wo