Information: - The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174 to 163 million years ago. In European lithostratigraphy, rocks of this Middle Jurassic age are called the Dogger. This name in the past was also used to indicate the Middle Jurassic epoch itself, but is discouraged by the IUGS, to distinguish between rock units and units of geological time. - The Early Cretaceous/Middle Cretaceous (geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 146Ma to 100 Ma. - The Jurassic (from Jura Mountains) is a geologic period and system that spans 56.3 million years from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period is marked by the major TriassicJurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian/Toarcian event in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the "Big Five" mass extinctions. - Iguanodon (; meaning "iguana-tooth") is a genus of ornithopod dinosaur that existed roughly halfway between the first of the swift bipedal hypsilophodontids of the mid-Jurassic and the duck-billed dinosaurs of the late Cretaceous. While many species have been classified in the genus "Iguanodon", dating from the late Jurassic Period to the late Cretaceous Period of Asia, Europe, and North America, research in the first decade of the 21st century suggests that there is only one well-substantiated species: "I. bernissartensis", which lived from the late Barremian to the earliest Aptian ages (Early Cretaceous) in Belgium and possibly elsewhere in Europe, between about 126 and 125million years ago. "Iguanodon" were large, bulky herbivores. Distinctive features include large thumb spikes, which were possibly used for defense against predators, combined with long prehensile fifth fingers able to forage for food. - The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period million years ago (Mya) to the beginning of the Paleogene Period Mya. It is the last period of the Mesozoic Era. The Cretaceous Period is usually abbreviated K, for its German translation "Kreide" (chalk). - Not to be confused with Dyrosauridae Dryosaurids were primitive iguanodonts . They are known from Middle Jurassic to Early Cretaceous rocks of Africa , Europe , and North America . - Hypsilophodonts (named after "Hypsilophodon", itself derived from the "Hypsilophus" ("high-crested") genus of iguana lizard and literally meaning ""Hypsilophus"-tooth") were small ornithopod dinosaurs, regarded as fast, herbivorous bipeds on the order of 12meters long (3.36.6feet). They are known from Asia, Australia, Europe, New Zealand, North America, and South America, from rocks of Middle Jurassic to late Cretaceous age. The group traditionally has included almost all bipedal bird-hipped dinosaurs other than iguanodonts, and some early phylogenetic analyses found it to be a natural group, but more recent studies have found that the group is mostly paraphyletic and the taxa within represent a series leading up to Iguanodontia. Some of these studies have moved some traditional hypsilophodonts out of the Ornithopoda, such as "Agilisaurus" and "Othnielosaurus" (="Othnielia"). Thus, the only certain member at this time is "Hypsilophodon". What is the relationship between 'dryosauridae' and 'iguanodontia'?
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parent taxon