The Tangled Web of Spider Classification

Spider classification is a complicated business. Since 1900, taxonomists have reshuffled the spider order (Order Aranea) nearly 20 times. Today, there are approximately 34,000 recognized spider species which are sorted into 100 families. Those 100 families are then sorted into three suborders.

The three suborders within the Order Aranea include:

• Suborder Mesothelae
• Suborder Mygalomorphae
• Suborder Araneomorphae

Suborder Mesothelae are considered the most primitive of all living spiders. This suborder includes only one family (Liphistiidae) and 40 species.

Suborder Mygalomorphae is the suborder that includes all of the tarantula families (Atypidae, Ctenizidae, Dipluridae, and Theraphosidae), about 1450 species.

Finally, the Suborder Araneomorphae is the largest of the three suborders and comprises more than 90% of all spider species (more than 30,000 species). Members of this suborder include funnel-web spiders, orb-web spiders, wolf spiders, crab spiders, jumping spiders, and many others.

The classification of spiders relies heavily on the finer points of spider anatomy. For example, differences in mouthparts, silk-producing organs (called spinnerets), leg structure, and body segmentation all play a role in determining relatedness between species and in turn enables taxonomists to place them into one of the three suborders described above.

Source: Foelix, R. F. 1996. Biology of Spiders, 2nd Ed. USA: Oxford University Press.

Photo © Pixelman / Shutterstock.