Atrax Robustus (Funnel Web Spider)

[Titania]

I don't know if this has been asked before, and if it has, I apologize and ask for directions on getting to the correct thread .

I guess I just wanted to know why the funnel web spider is not considered a tarantula? What are the main differences? I mean, true spiders' fangs point horizontally, like pinchers, no? And Ts' fangs point down. The funnel web's also point down, and they do look a whole lot like a tarantula... yet they are not considered one. Why? ::

 

[poisoned]

Funnel webs, trapdoors and some other spiders are not "true spiders", they are part of Mygalomorphae infraorder, together with Theraposidae (tarantulas).

 

[Ciphor]

I don't know if this has been asked before, and if it has, I apologize and ask for directions on getting to the correct thread .

I guess I just wanted to know why the funnel web spider is not considered a tarantula? What are the main differences? I mean, true spiders' fangs point horizontally, like pinchers, no? And Ts' fangs point down. The funnel web's also point down, and they do look a whole lot like a tarantula... yet they are not considered one. Why? ::

They are related but not the same. I'll give you the break down.

Kingdom: Animala
Phylum: Arthropoda (segmented animals)
Class: Arachnida (2 body segments or less)
Order: Araneae (spiders)
--Sub-orders below--
Opisthothelae (no plates on abdomen)
Mesothelae (plates on abdomen)
--Infra-orders below--
Araneomorphae (true spiders, or the most evolved spiders. Examples: Wolf spiders, Orbweavers, Fishing Spiders, Jumping spiders, Cobweb spiders, platform spiders, dwarf spiders, etc. They have short lifespans, and fangs are on a horizontal axis. Spiders size range from small to medium)
Mygalomorphae (Primitive spiders. Examples: Tarantulas, Trapdoor spiders, Funnel-web spiders, Purse-web spiders, etc. Fangs are on a vertical axis and they have long lifespans. Spiders size range from small to large)

Then you have super-families and other clads that make it a little more messy. For example in Araneomorphae you have Homalonychidae and Hypochilidae, and also non taxon clads likes Entelegynes (advanced true spiders) and Haplogynes (primitive true spiders).

The main factor that determines where a particular organism is placed in clads and taxons are its anatomical features. Funnel-web spiders & tarantulas are both Mygalomorphae because fangs are positioned on vertical axis, but they are different in many ways such as tarantulas have flat padded tarsus, and funnel-web spiders have a more narrow tarus. Trapdoor spiders have a pointed tarsus.

Hope that clarifies some of it for you. Best I can do to explain taxon & clad grouping in a single forum post without getting into to much detail.