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Apomorphic and synapomorphic characteristics convey much information about evolutionary clades and can be used to define taxa. However, plesiomorphic and symplesiomorphic characteristics cannot. The term symplesiomorphy was introduced in 1950 by German entomologist Willi Hennig.
The terms "plesiomorphy" and "apomorphy" are typically used in the technical literature: for example, when a plesiomorphic trait is shared by more than one member of a clade, the trait is called a symplesiomorphy, that is, a shared primitive trait; a shared derived trait is a synapomorphy.
Willi Hennig 1972 Peter Chalmers Mitchell in 1920 Robert John Tillyard. The original methods used in cladistic analysis and the school of taxonomy derived from the work of the German entomologist Willi Hennig, who referred to it as phylogenetic systematics (also the title of his 1966 book); but the terms "cladistics" and "clade" were popularized by other researchers.
Phylogenies showing the terminology used to describe different patterns of ancestral and derived character or trait states. [1]In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy).
This body type is plesiomorphic (ancestral) to the other two shapes, with some narrow-bodied aetosaurs more closely related to typothoracines and others closer to desmatosuchines. [4] Some plesiomorphic genera, like the widespread Norian genus Aetosaurus and the Carnian Coahomasuchus, tended to be small, about a metre (3.2 ft) in length. [14]
They are considered to have characteristics that are more "primitive" (ancestral or plesiomorphic) than those of simians (monkeys, apes, and humans). [5] Simians emerged within the Prosimians as sister group of the haplorhine tarsiers, and therefore cladistically belong to this group. Simians are thus distinctly closer related to tarsiers than ...
The world's smallest known vertebrate, Paedophryne amauensis, sitting on a U.S. dime.The dime is 17.9 mm in diameter, for scale. The word amphibian is derived from the Ancient Greek term ἀμφίβιος (amphíbios), which means 'both kinds of life', ἀμφί meaning 'of both kinds' and βίος meaning 'life'.
For example, it retains an intertemporal bone, which is the plesiomorphic ("primitive") condition present in animals like Ventastega and embolomeres. [19] The skull bones were heavily textured, as was typical for ancient amphibians and captorhinid reptiles. In addition, the rear part of the skull had a large incision stretching along its side.