Parapeytoia

Parapeytoia is a genus of Cambrian arthropod. The type and only described species is Parapeytoia yunnanensis, lived over 518 million years ago (Cambrian Stage 3) in the Maotianshan shales of Yunnan, China. Unidentified fossils from the same genus also had been discovered from the nearby Wulongqing Formation (Cambrian Stage 4).

Classification
Initially, Parapeytoia was interpreted as a radiodont ("anomalocaridid" at that time) dinocaridid with legs alongside Cucumericrus, purported to be an indicator that radiodonts might have legs underneath their body flaps in general, comparable to Pambdelurion. With the combination of megacheiran and presumably radiodont features (see text), it was also suggest to be an intermediate form between the two taxa. However, later studies reveal it most likely nested within megacheirans,      and megacheirans was no longer thought to be originated from radiodonts since than. Within megacheirans, Parapeytoia possibly closest to the multisegmented (with over 20 trunk segments) taxa like Fortiforceps and Jianfengia, united under the family Jianfengiidae.

Description


Parapeytoia is known from a few incomplete fossil materials with part of its ventral structures preserved. The frontmost appendages were a pair of great appendages that form by a robust peduncle and 4 distal segments with serrated spine on each of them, a feature shared by some other megacheirans such as Yohoia and Fortiforceps. Behind the great appendages were 2 or 3 pairs of short appendages, and numerous pairs of well-developed biramous appendages, each formed by a basipod with spiny gnathobase, lobe-like exopod and leg-like endopod with 8 segments. A narrow, hourglass-like sternite associated between each of those appendages.

Some features originally interpreted as radiodont-like are more or less questionable, such as radial sclerites interpreted as its mouthparts (oral cone) have since been assigned to another genus of animal, Omnidens. While some subsequent studies suggest those features are genuine, it most likely represent ancestral traits originated from more basal arthropods instead of any indicators of radiodont affinities. The same goes with gnathobases, and the presence of arthropodized endopods underneath the purported body flaps (exopods) conflict with the component of radiodont trunk appendages as well (the radiodont ventral body flaps are most likely homologous to euarthropod endopods).

Parapeytoia was in all likelihood a benthic feeder, spending most of its time on the ocean floor hunting (or possibly scavenging) for prey.