30.03.2024
It is not uncommon for Tapinauchenius to become Amazonius 

Some time ago, during a visit to the Belgian tarantula breeder Samuel Spreuwers, we received a few exuviae of tarantulas unknown to him with the request to identify these exuviae. We had already presented the first results on our website (-> HERE). Because we have recently been very busy with some scientific projects on the systematics of tarantula species, we have only now been able to examine and identify another exuvia from Samuel Spreuwers' collection.

This exuvia (Fig. 1) was labeled "Tapinauchenius sp., Ecuador -> Jason Xie". Obviously, this is indeed a species from the subfamily Psalmopoeinae. For this reason, the most recent publication for this subfamily by Cifuentes & Bertani 2022 was consulted to clarify the species status. The first step was to determine the genus, as the label "Tapinauchenius" could well be incorrect, as Tapinauchenius and Amazonius species look very similar externally. 

Following the identification key for the genera of Psalmopoeinae in Cifuentes & Bertani on page 32, we came to the conclusion that this animal must be an Amazonius and not a Tapinauchenius, as it has a "Maxillary lyra with slender bristles forming an oval patch" (Fig. 2, green circle). On the chelicerae basal-retrolateral is the complementary to this maxillary lyra, which consists of longer, strong setae (Fig. 3, green circle & Fig. 4).

But what species could it be?

For this we used the identification key for the females of the species of the genus Amazonius in Cifuentes & Bertani 2022 on page 99 as well as the information from the publication by Huesser 2018 on the same topic.

First, it had to be clarified whether a "... single sub segmented distal lobe" or "... multilobular distal lobes" were present in the spermathecae. As can be clearly seen in Fig. 5, both receptacula seminis have "multilobular distal lobes" (green arrows) at their tip.

Now 2 species remained that could come into question, namely Amazonius elenae, which has long thin hairs on the femora of the front legs ventrally or Amazonius burgessi, which has "short stiff setae" at this point according to the identification key of Cifuentes & Bertani 2022 (see Fig. 6 & 7 from Cifuentes & Bertani 2022). The present exuvia does not have long thin hairs on the femora of the front legs, but has "short stiff setae" there, as can be seen in Figs. 8 & 9 and as is typical for Amazonius burgessi. The spermatheca from the exuvia also shows a high structural correspondence to the spermatheca of the holotype of Amazonius burgessi (see Fig. 10 from the original description of Amazonius burgessi by Huesser 2018).

Resumé

When identifying an exuvia of Samuel Spreuwers, which was labeled as "Tapinauchenius sp., Ecuador", we were able to determine from the identification key from the most recent publication on the Psalmopoeinae by Cifuentes & Bertani 2022 that it is in fact an Amazonius burgessi (Huesser 2018). Due to the similarity of Tapinauchenius and Amazonius species, an exact identification of these tarantulas is often only possible through a correct taxonomic determination. However, this example also shows once again how often we have misidentified tarantula species in our terrariums.

Reference

Cifuentes, Y. & Bertani, R. (2022). Taxonomic revision and cladistic analysis of the tarantula genera Tapinauchenius Ausserer, 1871, Psalmopoeus Pocock, 1985, and Amazonius n. gen. (Theraphosidae, Psalmopoeinae). Zootaxa 5101(1): 1-123.

Huesser, M. (2018). A first phylogenetic analysis reveals a new arboreal tarantula genus from South America with description of a new species and two new species of Tapinauchenius Ausserer, 1871 (Araneae, Mygalomorphae,Theraphosidae). ZooKeys 784: 59-93.