Dinosaurs are a diverse group of animals of the clade Dinosauria. They first appeared during the Triassic period, 231.4 million years ago, and were the dominant terrestrial vertebrates for 135 million years, from the beginning of the Jurassic (about 201 million years ago) until the end of the Cretaceous (66 million years ago), when the Cretaceous–Paleogene extinction event led to the extinction of most dinosaur groups at the close of the Mesozoic Era. The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic Period and, consequently, they are considered a subgroup of dinosaurs by many paleontologists. Some birds survived the extinction event that occurred 66 million years ago, and their descendants continue the dinosaur lineage to the present day. Etymology Definition The common House Sparrow (Passer domesticus) is often used to represent modern birds in definitions of the group Dinosauria General description Distinguishing anatomical features
Related: Tree of Life - Phylogenetic systematics
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Track and FieldInternational Code of Zoological NomenclatureHow names are correctly established in the frame of binominal nomenclatureWhich name must be used in case of name conflictsHow scientific literature must cite names Zoological nomenclature is independent of other systems of nomenclature, for example botanical nomenclature. This implies that animals can have the same generic names as plants. In other words, whether a species itself is or is not a recognized entity is a subjective decision, but what name should be applied to it is not. The Code is also retroactive or retrospective, which means that previous editions of the Code, or previous other rules and conventions have no force any more today, and the nomenclatural acts published 'back in the old times' must be evaluated only under the present edition of the Code. Principles In regulating the names of animals it holds by six central principles, which were first set out (as Principles) in the third edition of the Code (1985): Principle of binominal nomenclature Example:
Dinosaures (TV Series 1991–1994TaxonThe idea of a "natural system" of classification goes back to the dawn of scientific nomenclature in the mid-18th century, as indicated by the title of Carolus Linnaeus' 1758 Systema Naturae. Systematists since that time have striven to determine the true classification of the diversity of life, which was at that time thought to reflect the Plan of Creation. Today it is common to define a "good taxon" as one that reflects evolutionary (phylogenetic) relationships. This is not mandatory, as is evident from commonly used words for non-monophyletic entities such as invertebrates, conifers and fish. A taxon may be given a formal scientific name, the application of which is governed by one of the Nomenclature Codes, which set out rules to determine which scientific name is correct for that particular grouping. Many modern systematists using cladistic methods, including advocates of phylogenetic nomenclature, require taxa to be monophyletic, consisting of all descendants of some ancestor.
when i was 5 i loved dinosReading trees: A quick reviewReading trees: A quick review A phylogeny, or evolutionary tree, represents the evolutionary relationships among a set of organisms or groups of organisms, called taxa (singular: taxon). The tips of the tree represent groups of descendent taxa (often species) and the nodes on the tree represent the common ancestors of those descendants. Two descendents that split from the same node are called sister groups. Many phylogenies also include an outgroup — a taxon outside the group of interest. Evolutionary trees depict clades.
i always loved carsCladeCladogram (family tree) of a biological group. The red and blue boxes at right and left represent clades (i.e., complete branches). The green box in the middle is not a clade, but rather represents an evolutionary grade, an incomplete group, because the blue clade at left is descended from it, but is excluded. Increasingly, taxonomists try to avoid naming taxa that are not clades. Etymology The term "clade" was coined in 1957 by the biologist Julian Huxley to refer to the result of cladogenesis, a concept Huxley borrowed from Bernhard Rensch. Definitions Gavialidae, Crocodylidae and Alligatoridae are clade names that are here applied to a phylogenetic tree of crocodylians. Clade and ancestor A clade is by definition monophyletic, meaning it contains one ancestor (which can be an organism, a population, or a species) and all its descendants. Clades and phylogenetic trees Terminology The relationship between clades can be described in several ways: See also