Works Cited
Anissimov, Michael, and Bronwyn Harris. "What Are Chelicerates?" WiseGEEK. Conjecture Corporation, 28 May 2017. Web. 14 June 2017.
This article explains what Chelicerates are. Chelicerates are named for their chelicerae, specialized appendages used for feeding and manipulating food, in lieu of the chewing mandibles employed by other arthropod subphyla, such as Hexapoda (which includes insects). There are five major classes of chelicerates: Arachnids (spiders, scorpions, mites, etc.), Xiphosura (horseshoe crabs), Eurypterida (sea scorpions), Chasmataspidida (chasmataspids), and Pycnogonida (sea spiders). Of these, Eurypterids and Chasmataspidida are extinct, and Xiphosura, the horseshoe crab -- considered a "living fossil" -- consists of only four species.
The largest and most successful of the chelicerates, by far, are the arachnids. When you hear the word "arachnid," spiders immediately leap to mind, and indeed, spiders are the most numerous arachnid, if only described species are counted. About 40,000 spider species have been identified, out of a total of 110,000 arachnids known to science. However, it is likely that another arachnid group -- ticks and mites -- are actually the most numerous, but because of their small size, have yet to be adequately classified. Different species of mite may have few external differences, requiring comparisons between DNA sequences to verify the distinct species. This massive project has only just begun.
So cool! I never knew that organisms could use chelicerae instead of teeth for chewing! Also, it's cool that spiders are not the most numerous arachnids!
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