Mygalomorph spiders constitute a moderately diverse group including more than 2,600 described species, currently classified into over 300 genera and 15 families. Familiar mygalomorphs include tarantulas (also called baboon spiders) and trapdoor spiders, but many other distinctive taxonomic groups exist. Most mygals are relatively large, long-lived (15-30 years), ground dwelling spiders - the largest spiders in the world are in fact mygalomorphs. These spiders build a diverse array of silk constructs for prey capture, shelter, and protection (Coyle 1986). Considered an ancient monophyletic group (Coddington & Levi 1991; Platnick & Gertsch 1976; Raven 1985), mygalomorphs retain several characteristics that are considered primitive for spiders (e.g., two pairs of book lungs, simple spinning structures, etc). Many mygalomorph taxa are dispersal-limited and regionally-endemic, and have long been favorites of biogeographers (e.g., Griswold & Ledford 2001; Platnick 1981). Mygalomorph lineages have a deep evolutionary history, as reflected in a rich fossil fauna that extends back to the lower Triassic (Selden & Gall 1992), with fossil representatives of several families dating to the mid-Cretaceous (see Eskov & Zonshtein 1990; Penney et al. 2003; Selden 2002). Recent molecular clock analyses suggest intra-familial divergences date to the Cretaceous (Hendrixson & Bond 2007), and inter-familial divergences may be as old as 300 Ma (Ayoub et al. 2007).
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