[1] Metapelma archetypon is known only from one fossil, the holotype, number "AMNH BaJWJ-407", which is a single female specimen preserved, along with a spider, in a nearly rectangular amber block 13 by 11 millimetres (0.51 by 0.43 in) in size.

The block is currently residing in the American Museum of Natural History paleoentomology collections in New York City, USA.

Several areas of the female are obscured or missing, with the dorsal mesosomal and part of the gastral structures covered by a white substance.

While M. archetypon has a deeply divided upper and lower mesepimeron separating the acropleuron and metapleuron, a feature found only in Metapelma, the shapes of the hind legs and head are closer to the general morphology of the subfamily Neanastatinae.

Although not confirmed shape of the ovipositor and relationship in the genus Metapelma suggests M. archetypon was parasitic on wood-boring beetles.