Taxonomy

Phylum: Arthropoda

Class: Megacheira

Order：Leanchoiliida

Family: Leanchoiliidae

Genus：Leanchoilia

Specie: Leanchoilia illecebrosa

Description:

Leanchoilia illecebrosa has a strongly convex dorsal exoskeleton consisting of a simple shield with a rostrum,11 trunk tergites and a pointed tailpiece with a marginal fringe of spines. The average size ranges from 20 to 46mm in length.  The shield covers the head,which consists of an anterior portion carrying the eyes and four limb-bearing segments. The eyes are located ventrally in the anterior region of the cephalon.They are distinctly reniform, or form part of a reniform structure. The first paired appendage in the cephalon is a prominent ʻgreat appendageʼ. The cephalon also carries three pairs of biramous appendages resembling those of the trunk.The ʻgreat appendageʼ consists of 6 articles. The two proximal articles do not show any outgrowths and are therefore regarded as forming a peduncle. The comparatively long third distal article has a hook-like extension medio-distally. The fourth distal article extends into another very long distal filament. The three long filaments were somewhat curved, and each of them tapers slowly in width toward the tip, indicating that they were flexible,but annuli are not discernible. In lateral aspect, the antero-lateral margins of the shield run ventrally in an almost straight horizontal line and then sharply flex dorsally straight up to meet medio-distally. In profile, the dorsal midline inclines gently to run almost straight back in its last quarter. In all, the lateral margins extend only slightly beyond the level of the venter. The anterior tip of the cephalic shield is drawn out into a short and straight rostrum. All the 11 trunk tergites of L. illecebrosa are almost of the same length, and the widest part is at the third trunk segment. The limbs posterior to the ʻgreat appendageʼ consist of a proximal portion, the basipod, on which an endopod with nine podomeres inserts distally, and an exopod with two portions inserts on its tilting outer margin. The limbs insert on the body proper through an ample membrane. The tailpiece consists of a cylindrical part anteriorly and a dagger-shaped flap posteriorly. Each side of the tail flap has a row of postero-laterally pointed needle-like setae.

Age & Localities

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

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