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FIGURE 1. Basal protomonaxonids and a primitive hamptoniid from the early Cambrian Hetang Biota, South China. 1-2, NIGP154828 Hyalosinica sp.; 1, overall view with examples of hexactines arrowed; 2, magnification of hexactines in central part of (1); 3, NIGP155891 apparently undescribed genus (new genus B) with mass of minute, inflated and short-rayed hexactines (visible as tiny shadowed cavities) amongst irregularly-arranged, fine monaxons; 4-5, NIGP155892 undescribed genus (new genus A) with dense wall of minute, inflated-rayed hexactines and no monaxons; 4, overall view showing body form; 5, detail showing mass of minute, short-rayed hexactines preserved as external moulds; 6, NIGP155893 probably undescribed genus (new genus C) with irregular, dense array of sub-longitudinal monaxons but lacking hexactine-based spicules, interpreted as a primitive hamptoniid-like sponge due to the lack of hexactine-based spicules; 7-8, NIGP155894 probably undescribed genus with conical body wall containing mostly diagonally-oriented monaxons, and non-inflated hexactine-based spicules. Scale bars equal: 1, 3: 5 mm; 2, 5, 8: 1 mm; 4, 6-7: 10 mm.


FIGURE 2. Leptomitidae, from the Burgess Shale (middle Cambrian, Canada).1, 3 Leptomitus lineatus ROM 53558; 1, apex of sponge showing longitudinal monaxon bundles converging towards narrowed osculum, and short transverse monaxons; 3, basal region with linear skeletal nucleation centre; 2, 4 Wapkia elongata; 2, ROM53549, showing fundamental architecture of longitudinal spicules with prominent development of transverse monaxon bundles, distorted into plumose array in left half; 4, ROM 53544, apical region of holotype showing skeletal architecture. 5, 7, ROM6l9l5, probably undescribed leptomitid-like sponge with thick wall and complex architecture from Burgess Shale locality S7; 6, ROM6l9l0, undescribed protomonaxonid from the Burgess Shale locality S7; previously named as Leptomitus but lacks transverse spicules (photograph: J.-B. Caron, ROM). 1-3, 5, 7 photographed under crossed polarisers, with high-angle illumination; 4 photographed with low-angle illumination. Scale bars equal: 1, 7: 1 mm; 2-5: 5 mm; 6: 50 mm. ].

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FIGURE 3. Hamptoniidae and 'Choiidae'. 1, Hamptonia bowerbanki, ROM6l9l4 from Monarch Cirque, British Columbia (ROM), with bimodal array of monaxons including relatively large, prominent spicules embedded in finer thatch; 2-3, NIGP155895 Choia sp. from the Hetang Biota; 2, overall view showing projecting monaxons; 3, magnified view of central body showing acicular coronal spicule bases (compare with Figure 4); 4, Lenica sp. NIGP154161, detail showing conical, organic-walled spicules preserved as flattened, partly pyritised moulds. Scale bars equal: 1: 10 mm; 2, 4: 5 mm; 3: 2 mm.

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FIGURE 4. Halichondritid and piraniid sponges from early and middle Cambrian Lagerstätten. 1,3, apparently undescribed halichondritid-like sponge NIGP155896, Hetang Biota (early Cambrian, Anhui, South China); 1, view of partial specimen, showing architecture of fine monaxons and open-based, conical spicules; 3, detail with single conical spicule; 2, 4, Choia hindei (ROM53563) from the Burgess Shale, showing bimodal spicule sizes, the flattened open bases of large spicules shown in D; 5-6 Pirania muricata; 5, ROM6l9l3, details of central parts of spicules with preserved axial regions, dissolved middle layer, and organic preservation of outer film; 6, ROM53589, detail showing insertion of spicules into sponge wall, with poorly-defined, apparently open bases. Scale bars equal: 1-2: 5 mm; 3, 5-6: 1 mm; 4: 2 mm.

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FIGURE 5. Hazeliidae from the Burgess Shale (middle Cambrian, British Columbia, Canada). 1, Hamptoniella foliata ROM44283, with sub-longitudinal array of spicule tracts and irregular cross-branching and reticulation; 2, Hazelia palmata ROM56247, distal part of large frondose specimen showing continuation of spicule tracts beyond margin; 3, ROM6l9l2, an undetermined hazeliid with a moderately thick, but disorganised wall and no reticulation; 4-5, ROM53578, new taxon described as Crumillospongia frondosa (Rigby and Collins, 2004) but showing echinating spicule tracts incompatible with that genus, visible in both cross-polarised (4) and low-angle light (5); 6-7, Hazelia delicatula ROM56258, with detail of upper right region (7) showing reticulate skeleton. Scale bars equal: 1, 6: 5 mm; 2, 4-5, 7: 1 mm; 3: 10 mm.

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FIGURE 6. Members of the vauxiid-anthaspidellid complex, from the Burgess Shale (middle Cambrian, British Columbia, Canada). 1, detail of Hazelia conferta ROM56253, with sub-regular reticulation of primary skeleton; 2,4, Vauxia cf. bellula ROM6l 9l l, showing regular hexagonal (pseudo-rectangular) reticulation of longitudinal columns, lateral parts complicated by superposition of the dermal layer, and detail (4) showing framework composed of discrete, usually paired and sometimes misaligned spicules; 3, Vauxia bellula ROM 56243; 5, Fieldospongia bellilineata ROM53602, showing regular arrangement of single and double monaxons to form hexagonal (sub-rectangular) reticulation; 6, undescribed fragment of anthaspidellid lithistid on same slab as ROM44283, with more complex skeletal architecture. Scale bar equals 1 mm.

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FIGURE 7. Phylogenetic hypothesis for the protomonaxonids, divided into two major groups: 1, large-spiculed taxa, including links to basal, hexactine-bearing sponges; 2, small-spiculed taxa with relationships to modern demosponge lineages. New genera A, B, and C are described briefly in the text. This reconstruction includes most of the genera described from Cambrian deposits, but a few poorly-understood or potentially problematic taxa are excluded. Vertical axis represents evolution; no scale of time or morphology is implied.

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FIGURE 8. Schematic illustration showing primary skeletal development in protomonaxonids, referring to the most fundamental changes described in Figure 7.1, Group One (refers to Figure 7.1); 2, Group Two (refers to Figure 7.2).

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