Taxonomy

Phylum: Lobopodia

Class: Xenusia

Order: Paronychophora

Family: Onychodictyidae

Genus: Onychodictyon

Specie: O.ferox

Description: This is a relatively common Chengjiang lobopodian. The specimens of Onychodictyon ferox are typically preserved in a strong rusty or brown color, with strong relief and mineralization around the sclerites. A complete specimen can reach 7 cm long and 5mm wide. The body is divided into a head region and an elongated trunk. The features of the head region have been controversial with regard to its shape, mouth structure, and the existence of antennae and a sclerotized head shield. The latest study shows that amongst the most conspicuous structures are the feathery, antenniform appendages, the proboscis with a terminal mouth and the ocellus-like eye at the basis of each antenniform appendage.The new material reveals that the anterior-most portion of the head comprizes a bulbous proboscis, delineated from the rest of the body by a circumferential constriction. A terminal mouth extends into a straight buccal tube.The proboscis is succeeded by the first body segment, which bears a pair of eyes and antenniform appendages. The eyes are represented by carbonaceous remains of simple, ocellus-like structures situated dorsolaterally on the head. Adjacent to these is a pair of annulated antenniform appendages with numerous branches. Another prominent feature of the head is a structure posterior to the proboscis, belonging to the first body segment and referred to as the “arcuate sclerite”. In contrast to the first and the remaining body segments, sclerotized structures of any sort are not evident in the second segment, which bears the first pair of walking lobopods.  There are 10 pairs of oval‐shaped sclerites arranged along the trunk, each of which is finely reticulate and has a sharp central spine. Beneath each pair of sclerites there is a pair of walking legs, with two additional pairs of legs located in front of the first pair of sclerites and at the posterior end of the body. There are 12 pairs of limbs. Each limb carries along its length at least two rows of tubercles, similar to those of the trunk. The number of tubercles in each row is at least 10, probably up to 20. Each of these legs is annulated, bearing longitudinal rows of papillae and a pair of large, curved, strongly sclerotized claws.The two most anterior pairs of legs appear to be somewhat shorter than the others. The trunk is strongly annulated except for the sclerite‐bearing region. The key distinguishing feature of this animal is the longitudinal rows of long, finger‐like papillae covering the whole body. The alimentary canal is straight, flat, and dark, extending from a terminal mouth at the proboscis tothe posterior end, with a bulbous pharynx located behind the head region. Onychodictyon has the strongest claws of any lobopodian, which are clearly well adapted for a grasping or attaching function. Together with the fact that the dark, flat gut lacks sediment infilling, this lobopodian could be interpreted to have led a predatory life style.O. ferox is unknown outside of the Chengjiang biota of Yunnan Province.

Age & Localities

Age: Cambrian Series 2, Stage 3, Eoredlichia-Wutingaspis Zone

Principal localities: Chengjiang biota (Yu’anshan Member of Chiungchussu Formation), eastern Yunnan Province, China