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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.
Opiliones' own divergence is dated to 414 million years ago, which arachnid are estimated to have originated during the late Cambrian to early Ordivician. [ 10 ] Genetic analysis performed on a modern Phalangium opilio specimen found that a suppressed gene that, if active, would generate a second pair of eyes at the lateral location, providing ...
However, in sea spider and arachnids, the pedipalps are more or less specialized for sensory [12] or prey-catching function [10] – for example scorpions have pincers [20] and male spiders have bulbous tips that act as syringes to inject sperm into the females' reproductive openings when mating.
Opiliones (commonly known as harvestmen) are an order of arachnids and share many common characteristics with other arachnids. However, several differences separate harvestmen from other arachnid orders such as spiders. The bodies of opiliones are divided into two tagmata (arthropod body regions): the abdomen (opisthosoma) and the cephalothorax
"The structure of a eukaryotic protein-coding gene. Regulatory sequence controls when and where expression occurs for the protein coding region (red). Promoter and enhancer regions (yellow) regulate the transcription of the gene into a pre-mRNA which is modified to add a 5' cap and poly-A tail (grey) and remove introns.
Among the oldest known land arthropods are Trigonotarbids, members of an extinct order of spider-like arachnids. [5]Trigonotarbids share many superficial characteristics with spiders, including a terrestrial lifestyle, respiration through book lungs, and walking on eight legs, [6] with a pair of leg-like pedipalps near the mouth and mouth parts.
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.
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