MECYSMAUCHENIIDAE Simon, 1895

Saupe, Erin E. & Selden, Paul A., 2009, First fossil Mecysmaucheniidae (Arachnida, Chelicerata, Araneae), from Lower Cretaceous (Uppermost Albian) amber of Charente-Maritime, France, Geodiversitas 31 (1), pp. 49-60 : 53

Family MECYSMAUCHENIIDAE Simon, 1895

REMARKS

Mecysmaucheniidae are diagnosed as having two spinnerets and chelicerae originating from a foramen in the carapace. Although our specimen has four spinnerets and we cannot be certain the chelicerae originate from a foramen in the carapace, we place the specimen in Mecysmaucheniidae on account of the following characters. The unsclerotized, constricted area on the base of the tarsal segments in our specimen appears to be a synapomorphy uniting the archaeids and mecysmaucheniids ( Forster & Platnick 1984; H. Wood pers. comm.) and places our specimen firmly among these families. The lack of a constricted neck or greatly heightened cephalic area (characteristic of Archaeidae ), and the presence of four spinnerets (vs six in archaeids), suggest our specimen should be included within Mecysmaucheniidae . Our reasoning is that, while mecysmaucheniids have only two spinnerets, this is a reduction from the plesiomorphic six (i.e. an apomorphy). Loss of spinnerets (or their reduction to patches of spigots) has occurred several times within the Palpimanoidea ( Forster & Platnick 1984) and is a character of known polarity. It is likely that reduction is a trend within the Mecysmaucheniidae and the condition in Archaemecys n. gen. represents a stage in the reduction. Archaeids have two spiracle openings, unlike the single opening seen in the mecysmaucheniids and our specimen. Additionally, Forster & Platnick (1984) mentioned that the spiracle is often sclerotized in mecysmaucheniids, a character observed in our fossil. Archaemecys n. gen., like other mecysmaucheniids, does not have tubercles on the carapace, and the chelicerae in the fossil are shorter and stouter than those usually found in archaeids. Archaeids have spatulate hairs on the tibia and metatarsus of leg 1 ( Forster & Platnick 1984), but the Mecysmaucheniidae , including our specimen, do not. Additionally, our specimen does not have a femoral hump, as is present in archaeids (see Wunderlich 2004). A Pararchaeidae affinity can be ruled out because, as mentioned above, the pararchaeids do not possess the unsclerotized, constricted area at the bases of the tarsi. This aside, our specimen has plumose leg setae, not the serrate or smooth setae found in pararchaeids, and the legs are stout, unlike the slender legs characteristic of pararchaeids.