Classification of Arthropods

Classification of Arthropods - reaching a length of over 10...

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Classification of Arthropods Due to their great diversity of appendages, lifestyles, and other features, arthropods are usually separated into several subphylums. The Subphylum Chelicerata The subphylum Chelicerata includes spiders, scorpions, ticks, mites, horseshoe crabs, etc. The first pair of appendages are chelicerae, second pair are pedipalps, and the next four pairs are walking legs. Chelicerae are appendages that function as feeding organs. Pedipalps are feeding or sensory in function; although in scorpions, they are large pincers. All appendages attach to a cephalothorax, a fusion of the head and thoracic regions. The head lacks antennae, mandibles, or maxillae appendages. The Class Merostomata The class Merostomata contains the extinct "sea scorpions" (or eurypterids) and the extant (living) horseshoe crabs. Eurypterids are extinct, but were important elements of faunas 200-500 million years ago during the Paleozoic Era. Some were huge,
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Unformatted text preview: reaching a length of over 10 feet. Some eurypterids may have been amphibious, emerging onto land for at least part of their life. Horseshoe crabs are an ancient group consisting today of only 5 species. Members of this class have a large shield that covers the cephalothorax. The compound eyes are reduced. The second pair of appendages, the pedipalps, resemble walking legs. They have a long, spike-like appendage called a telson that projects from the rear of their bodies. Respiration is via book gills (precursors to book lungs?). The horseshoe crab genus Limulus is a familiar sight along the east coast of North America. The anterior shield is a horseshoe-shaped carapace with two compound eyes. The long, unsegmented telson projects to the rear. They possess book gills that resemble the pages in a book. Limulus is considered a living fossil due to its great similarity to fossil forms from the Paleozoic Era....
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