Aphonopelma eutylenum, steindachneri, or Something Else?
Vanessa

Aphonopelma eutylenum, steindachneri, or Something Else?

Freshly moulted female approximately 3". I know there is often errors made in identification of these guys. I was actually hoping she would end up being A.steindachneri, because I love big, black, tarantulas. I am not disappointed, but I just want to clear up what species she is... if possible.
@Smokehound714 My understanding is that A.eutylenum is a tan tarantula and looks far closer to a chalcodes than this girl does. The photos I have found of A.eutylenum show a very light carapace with tan and brown legs and a dark abdomen.
Do you have any photos of your girl's spermathecae? I would like to have a comparison to look at when my girl moults again.
 
You may find images of spermatheca in the 2016 aphonopelma revision by Hendrixson and Hamilton.

As for eutylenum, they are extremely polymorphic. they can resemble chalcodes, or they can be silver like yours, or even greenish or blueish, some can have a black caput (eye turret). coloration is a poor indicator of species without a trained eye.

the revision covers all the species of aphonos with great high-res images of features important for ID.

one easy way to tell apart steindachneri from eutylenum is their much shorter, more velvety integument, thicker massive build, and huge carapace. Also, they live in cryptic burrows. if your tarantula came from a classic tarantula burrow, it's definitely not steindachneri
 
@VanessaS You are correct in that A. eutylenum is a tan/ blonde tarantula so that immediately disqualifies your tarantula as being that species. Only matured males of A. eutylenum are black. If you do not have collection information, then getting a definite ID is going to be near impossible. You also have to consider Aphonopelma marxi from Arizona and Colorado is also black. Spermatheca shape isn't a reliable character to use since it is highly variable across all species except for A. anax. In addition, since Aphonopelma species from the USA are frequently misidentified in the pet trade, you maybe comparing pictures of spermathecae of the wrong species.
 
@Smokehound714 If A. eutylenum can be black, then how did you accurately identify the ones you have seen as A. eutylenum? Do they change color between molts or is a black A. eutylenum always black? Since I haven't collected these species myself, I don't have a reason to doubt you other than the USA Aphonopelma revision doesn't mention polychromatism. After looking at the revision again, it appears the best way to distinguish A. eutylenum from A. steindachneri without taking color into consideration is the extent of the leg 4 metatarsal scopulation. A. eutylenum at over 50% and A. steindachneri at less than 50%. I don't ever ID tarantulas based on robustness or color, especially if one is using terms like "more black than.." or "more brown than.." A. anax is generally considered a large robust species, but I have one that is small and doesn't look like the pictures, even the pictures in the revision paper, but keys by where it was collected and by spermatheca shape. Because size, or "robustness", in this one case was useless to make an ID, it raises doubt on its usefulness in other Aphonopelma species. We are also talking about a tarantula bought from the pet trade which most likely does not have collection information. In that case, all biases have to be tossed out and an identification has to be done from scratch instead of guessing at which species it could be based on a list of options. In this case specifically, the pictured tarantula may not be A. eutylenum or A. steindachneri.
 
@AphonopelmaTX I eliminated marxi, only because that species came in on the same import and a female was considerably more expensive. The import contained over a dozen different wild caught Aphonopelma species - some I had never even heard of before. Many species were from the California area - gabeli, paloma, xwalxwal - while others were from Arizona and New Mexico. I assume that whoever sent them to Tarantula Canada definitely knows the genus very well.
I have located the Taxonomic Revision over on NCBI, thank you @Smokehound714 .
 

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