Zhao et al.—Paleoecology of eldonioids in the Kaili Biota 92(6):972–981
975
Table 1. Quantitative data for associations between Pararotadiscus guiz- houensis and other taxa in the Kaili Biota at Balang village, Guizhou Province, China.
Associated taxa Complete brachiopods
Complete Pagetia trilobites
Complete adult eocrinoids
Complete juvenile eocrinoids
Disarticulated trilobites
Other fragmentary material
Gordia marina traces Total
Number of P. guizhouensis specimens that show association
128 82
5 11
190 74
138 628
Table 2. Four types of relationships between Pararotadiscus guizhouensis and associated organisms.
Figure 3. Pararotadiscus guizhouensis with alimentary canal and tentacles from the Kaili Biota at the Jinyinshan section, Guizhou Province, China (GTBJ-12-3-22b). Scale bar=10mm.
Symbiosis
Other living animal taxa with P. guizhouensis (commensal)
Benthic fixation
Other living benthic animal taxa on the carcass of P. guizhouensis
Co-burial
Co-burial with P. guizhouensis and other taxa
Scavenging
Marine trace Gordia made by scavenging the carcass of P. guizhouensis, with remains of P. guizhouensis
associated with other fossils, including trilobites, brachiopods, echinoderms, Wiwaxia, algae, and the trace fossil Gordia marina (Emmons, 1844). Detailed quantitative data for the 628 specimens with associated taxa examined in the present study are provided in Table 1. Four types of relationships between P. guizhouensis and associated fossils are recognized herein: symbiosis, co-burial, attachment of benthic taxa on P. guizhouensis carcasses, and scavenging of P. guizhouensis carcasses (Table 2). Each relationship is described in detail below.
Figure 4. Line drawing of a Pararotadiscus guizhouensis specimen showing key features and associated brachiopods (GTB-23-3-103a). Abbreviations as follows: (1) central ring; (2) inner ring; (3) middle ring; (4) outer ring; (5) concentric ring and ridge; (6) radial canal; (7) associated brachiopods.
compaction, folding of discs is rare, indicating that the disc of P. guizhouensis was probably softer than that of Rotadiscus grandis (Zhu et al., 2002). Specimens of P. guizhouensis range from 15–155 mm in diameter, with most having a diameter of 40–70mm; the mean diameter is 55mm (Zhu et al., 2002).
Repository and institutional abbreviation.—All study speci- mens are deposited at Guizhou University. Specimen numbers with the GTB prefix are from the Wuliu-Zengjiayan section, and those with the GTBM prefix are from the Miaobanpo section.
Relationships between Pararotadiscus guizhouensis and associated taxa
More than 2,500 specimens of P. guizhouensis have been collected from the Kaili Biota, of which ~40% are closely
Symbiosis.—Animals including brachiopods, Pagetia (trilo- bite), individual juvenile gogiids, and edrioasteroids (echino- derms) engaged in commensalism and mutualism with Pararotadiscus guizhouensis. As noted in a previous study (Zhu et al., 1999), a brachiopod of uncertain affinity, initially interpreted as the bradoriid ostracode Chuandianella? subovata (Yuan and Huang, 1994), appears to have had a commensal relationship with P. guizhouensis. The valves of this small brachiopod are elongate and oval in shape; one end is rounded and appears to be the anterior, the other end is subtriangular (Zhu et al., 1999, pl. 3, fig. D). Commonly, large numbers of these brachiopods are densely distributed on the outer ring of P. guizhouensis, each with the long axis oriented perpendicular to the adjacent portion of the rim and the apparent anterior end placed closest to the perimeter (Figs. 4, 5.5, 5.6). This distinctive arrangement suggests that the brachiopods were attached to live specimens of P. guizhouensis and benefitted from this relationship by gaining access to currents at a level well above
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