Hypsilophodontidae is a traditionally used family of ornithopod dinosaurs, generally considered invalid today. It historically included many small bodied bipedal neornithischian taxa from around the world, and spanning from the Middle Jurassic until the Late Cretaceous. This inclusive status was supported by some phylogenetic analyses from the 1990s and mid 2000s, although there have also been many finding that the family is an unnatural grouping which should only include the type genus, Hypsilophodon, with the other genera being within clades like Thescelosauridae and Elasmaria. A 2014 analysis by Norman recovered a grouping of Hypsilophodon, Rhabdodontidae and Tenontosaurus, which he referred to as Hypsilophodontia. All other analyses from around the same time have instead found these latter taxa to be within Iguanodontia.
Notohypsilophodon is a genus of ornithopod dinosaur from the Late Cretaceous of Argentina. It was described as the only "hypsilophodont" known from South America, although this assessment is not universally supported, and Gasparinisaura is now believed to have been a basal euornithopod as well.
Parksosaurus is a genus of neornithischian dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur. It is one of the few described non-hadrosaurid ornithopods from the end of the Cretaceous in North America, existing around 70 million years ago.
Alocodon is a genus of ornithischian dinosaur known from multiple teeth from the Middle or Late Jurassic Cabaços Formation of Portugal, and also the Forest Marble and Chipping Norton Formations of England. A single species is known, A. kuehnei.
Anoplosaurus is an extinct genus of herbivorous nodosaurid dinosaur, from the late Albian-age Lower Cretaceous Cambridge Greensand of Cambridgeshire, England. It has in the past been classified with either the armored dinosaurs or the ornithopods, but current thought has been in agreement with the "armored dinosaur" interpretation, placing it in the Ankylosauria.
Velocipes is a saurischian dinosaur genus from the Late Triassic that may have been a theropod; its fossils were found in the Norian-age Lissauer Breccia of southern Poland.
Trimucrodon is a genus of ornithischian dinosaur from the Late Jurassic Lourinhã Formation of Portugal. The type, and currently only, species is T. cuneatus.
Anabisetia is a genus of ornithopod dinosaur from the Late Cretaceous Period of Patagonia, South America. It was a small bipedal herbivore, around 2 metres long.
Fulgurotherium is a dubious genus of ornithischian dinosaur from the Late Cretaceous (Cenomanian) Griman Creek Formation. It lived in what is now Australia.
Magnosaurus was a genus of theropod dinosaur from the Middle Jurassic of England. It is based on fragmentary remains and has often been confused with or included in Megalosaurus.
Clasmodosaurus is a genus of titanosaurian sauropod dinosaur from the Bajo Barreal Formation. It lived during the Late Cretaceous in what is now Argentina. It is known only from three fossilized teeth, and is therefore a tooth taxon. It is a nomen dubium.
Kangnasaurus is a genus of iguanodontian ornithopod dinosaur found in supposedly Early Cretaceous rocks of South Africa. It is known from a tooth and possibly some postcranial remains found in the early-Aptian Kalahari Deposits Formation. It was probably similar to Dryosaurus.
Phyllodon was a genus of small ornithischian dinosaur from the Kimmeridgian-aged Upper Jurassic Camadas de Guimarota Formation of Leiria, Portugal and possibly also the Bathonian-aged Chipping Norton Limestone of England. It may have been closely related to contemporaneous dinosaurs in North America.
Siluosaurus is a genus of ornithopod dinosaur from the Barremian-Albian-age Lower Cretaceous Xinminbao Group of Gansu, China. It is based on the specimen IVPP V.11117 (1-2), which consists of two teeth. It is an obscure genus, with no papers doing more than mentioning it since it was described in 1997. The type species is S. zhanggiani.
Gongbusaurus is a genus of ornithischian, perhaps ornithopod, dinosaur that lived between about 160 and 157 million years ago, in the Late Jurassic period. A small herbivore, it is very poorly known. Two species have been assigned to it, but as the original name is based on teeth, there is no concrete evidence to connect the two species. Its fossils have been found in China.
Priodontognathus was a genus of ankylosaurian dinosaur possibly from the Oxfordian-age Upper Jurassic Lower Calcareous Grit of Yorkshire, England. It is a dubious genus based on a maxilla, and has been erroneously mixed up with iguanodonts and stegosaurs.
Cedrorestes is a genus of iguanodontian dinosaur from the Early Cretaceous of Utah. It is based on an incomplete skeleton which was found in the Valanginian-age Yellow Cat Member of the Cedar Mountain Formation.
Dryosauridae was a family of primitive iguanodonts, first proposed by Milner & Norman in 1984. They are known from Middle Jurassic to Early Cretaceous rocks of Africa, Europe, and North America.
The Twin Mountains Formation, also known as the Twin Mak Formation, is a sedimentary rock formation, within the Trinity Group, found in Texas of the United States of America. It is a terrestrial formation of Aptian age, and is notable for its dinosaur fossils. Dinosaurs from this formation include the large theropod Acrocanthosaurus, the sauropod Sauroposeidon, as well as the ornithopods Tenontosaurus and Convolosaurus. It is the lowermost unit of the lower Cretaceous, lying unconformably on Carboniferous strata. It is overlain by the Glen Rose Formation. It is the lateral equivalent of the lower part of the Antlers Formation.
Thescelosauridae is a clade of neornithischians from the Cretaceous of Asia, North America and possibly South America. The group was originally used as a name by Charles M. Sternberg in 1937, but was not formally defined until 2013, where it was used by Brown and colleagues as the group uniting Thescelosaurus and Orodromeus, based on their phylogenetic results. During a phylogenetic revision of neornithischians by Clint Boyd in 2015, the authorship of Thescelosauridae was given to Brown and colleagues, which meant that the similar name Parksosauridae, informally defined in 2002 by Buchholz, would have had priority over Thescelosauridae. The two clades had slightly different definitions, with Parksosauridae referring to all animals closer to Parksosaurus than Hypsilophodon, but they contained the same taxa so Boyd used Parksosauridae under the assumption it had priority. However, in formalizing the clade following the regulations of the PhyloCode, Madzia, Boyd, and colleagues identified in 2021 that Sternberg was the proper authority for Thescelosauridae, giving it priority over Parksosauridae. As well, they gave Thescelosauridae the definition of the largest clade containing Thescelosaurus neglectus but not Iguanodon bernissartensis, as long as Hypsilophodon foxii was not in the group, modifying previous definitions for Thescelosauridae in order to maintain its modern use, so that the clade was not applied if Thescelosaurus fell within Hypsilophodontidae, a family that has not been recently used but may be revived if the systematic position of Hypsilophodon was solidified at some point in the future. Madzia et al. identified the analysis of Madzia et al. in 2018 as the reference analysis for the name Thescelosauridae, an analysis based on a revised version of the 2015 Boyd analysis.
