Redescription of Burgessia bella from the Middle Cambrian Burgess Shale, British Columbia
1975; Wiley; Linguagem: Inglês
10.18261/8200049639-1975-28
ISSN2637-6032
Autores Tópico(s)Ecology and Vegetation Dynamics Studies
ResumoPreviously studied specimens and additional material of Burgessia bella from old and new collections have been prepared, and new photographs accompanied by explanatory line drawings are given together with reconstructions in various aspects. The carapace is roughly circular, invaginated posteriorly, and extends back above the trunk leaving only the long unsegmented posterior spine uncovered. The carapace is gently convex sagitally and transversely. No cephalic doublure or ventral plates are present. The body is segmented and appears to have been subcircular in cross-section, with no pleurae. The mouth is ventral. Four appendagebearing somites lie within the cephalon and the remaining eight in the trunk. A large kidney-shaped gut-caecal system occupies the lateral portion of the carapace, being connected by a wide diverticulum to the alimentary canal at the posterior cephalic somite. The so-called eyes are reinterpreted as attachment areas for muscles connecting the anterior end of the body to the carapace. The anterior cephalic appendages consist of a pair of multijointed uniramous antenna, the second, third and fourth are biramous, consisting of a jointed walking-leg and a whip-like flagellum. All the trunk appendages, "except the last, are biramous and consist of a coxa with telopod composed of six segments and terminal cIaws, and a small lateral, leaf-like gill branch presumed to be attached to the coxa. The posterior appendage is believed uniramous consisting simply of a backwardly curved spike. The telson consists of an anal segment lacking lateral appendages, and a long, tapering unsegmented caudal spine jointed at the base to the anal segment. Dark stains are occasionally associated with specimens and are presumed to represent organic matter squeezed out of the body during compaction. The carapace ranges from four to seventeen mm in maximum width, the size-frequency histogram being unimodal except that the smallest three specimens are somewhat detached. The occurrence within the Phyllopod bed cIosely matches that of Waptia, Marrella, and Yohoia.
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