Friday mystery object #441 answer

Last week I gave you this rather impressive spider to have a go at identifying:

The huge size had a several people on Twitter and in the comments here suggesting it’s a Goliath Birdeater Theraphosa blondi. It is big, with a leg span of around 19-20cm, but not quite as big (or as chunky) as the Goliath.

Also, although it’s probably not easy to see from the main image, this specimen has tibial spurs on the first pair of legs – which are absent in Goliath Birdeaters:

Tibial spurs on first pair of legs (don’t confuse them with the hooked mating organ at the end of the pedipalp)

Another thing that’s not easy to see in the main image is some subtle purple iridescence on the first three legs, pedipalps and chelicerae:

This is something I only noticed after looking for it with a light and it offers some support for the identification on the side of the box:

This label suggests the specimen is Bolivian (or in this case Peruvian) Blue-leg Birdeater Pamphobeteus antinous Pocock, 1903, but that species (as hinted at by the name) has quite distinctly blue legs:

There are fourteen other species in the genus Pamphobeteus, some of which also display some degree of iridescence on the same parts of the body, so I suspect that what we have here is one of the other species. I’m wondering if it might be Pamphobeteus grandis Bertani, Fukushima & Silva, 2008, which is very similar in appearance to P. antinous, except it has purple iridescence rather than violet/blue.

Unfortunately, I’m no spider expert and I don’t have time at the moment to go through the diagnostic features of P. grandis and relatives under a microscope, but when I get a chance I’ll check my tentative identification!

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