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The authors favoured relationships shown by more slowly evolving genes, which demonstrated the monophyly of Chelicerata, Euchelicerata and Arachnida, as well as of some clades within the arachnids. The diagram below summarizes their conclusions, based largely on the 200 most slowly evolving genes; dashed lines represent uncertain placements.
Paintings of Araneus angulatus from Svenska Spindlar of 1757, the first major work on spider taxonomy. Spider taxonomy is the part of taxonomy that is concerned with the science of naming, defining and classifying all spiders, members of the Araneae order of the arthropod class Arachnida, which has more than 48,500 described species. [1]
The group's origins lie within an arachnid sub-group defined by the presence of book lungs (the tetrapulmonates); [1] [2] the arachnids as a whole evolved from aquatic chelicerate ancestors. More than 45,000 extant species have been described, organised taxonomically in 3,958 genera and 114 families. [3] There may be more than 120,000 species. [3]
Diagram of a prawn, with the carapace highlighted in red. A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.
Pages in category "Arachnid genera" The following 30 pages are in this category, out of 30 total. This list may not reflect recent changes. A. Allokoenenia; C. Catageus;
Basic characteristics of arachnids include four pairs of legs (1) and a body divided into two segments: the cephalothorax (2) and the abdomen (3). The ventral side of a brown widow spider. The epigastric plates and furrow are visible, as well as the hourglass marking on the underside of the abdomen, which is a characteristic feature of widow ...
The idea of a tree of life arose from ancient notions of a ladder-like progression from lower into higher forms of life (such as in the Great Chain of Being).Early representations of "branching" phylogenetic trees include a "paleontological chart" showing the geological relationships among plants and animals in the book Elementary Geology, by Edward Hitchcock (first edition: 1840).
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