Figure 1.
Geographical location of the Tulip Beds.
A, position of the site (yellow star next to arrow), in relation to the Walcott Quarry (green star) and the Trilobite Beds (blue star). (The GPS coordinates for the locality are 51°24′06.1″ N, 116°27′06.4″W). B, telephoto of the Tulip Beds from Mount Field, showing the location of the main fossiliferous outcrops (yellow stars). Fossils were collected from two talus slopes (yellow dashed lines) or in situ in the Above Camp outcrop (yellow star on the left), now represented by a small quarry. The yellow star on the right indicates the approximate extent of the Above Camp fossil bearing layers to the southeast (distance between the two outcrops approximately 200 meters). The white dashed line indicates the boundary between the Campsite Cliff Shale Member (CCS) above and the Yoho River Limestone Member (YRL) below. C, close-up view of the Above Camp quarry in the summer of 2010 (yellow star on the left in B), showing the location of the fossiliferous beds excavated by the Royal Ontario Museum (small quarry just above crew members).
Figure 2.
Paratype of Siphusauctum gregarium n. gen. and n. sp. (ROM 61413) and explanatory camera lucida drawing.
Scale bar = 5 mm. Abbreviations: A - Anus, Con - Conical structure, CS - Comb Segments, ES - External Sheath, H - Holdfast, IS - Inner Stem, LD - Lower Digestive tract, OS - Outer Stem, Sed - Sediment, TG - Transverse Groove, UD - Upper Digestive tract.
Figure 3.
Holotype of Siphusauctum gregarium n. gen. and n. sp. (ROM 61414) and explanatory camera lucida drawing.
Insert shows a larger view of the external sheath with the outer layer partially detached, showing fine striae and transverse individual grooves of the comb-like segment below. Scale bar = 10 mm, insert = 1 mm. Abbreviations: Con - Conical structure, CS - Comb Segments, ES - External Sheath, H - Holdfast, IS - Inner Stem, LD - Lower Digestive tract, LS - Longitudinal Suture line, OS - Outer Stem, S - Striae, TG - Transverse Groove.
Figure 4.
Paratype of Siphusauctum gregarium n. gen. and n. sp. (ROM 61415) and explanatory camera lucida drawing.
Scale bar = 10 mm. Abbreviations: A - Anus, BC - Body Cavity, Con - Conical Structure, CS - Comb Segments, ES - External Sheath, IS - Inner Stem, LD - Lower Digestive tract, MD - Middle Digestive tract, OS - Outer Stem, S - Striae, TG - Transverse Groove, UD - Upper Digestive tract.
Figure 5.
Range of sizes observed in Siphusauctum gregarium n. gen. and n. sp.
A, the largest (ROM 61416) and one of the smallest (inset, see also B and C) specimens of S. gregarium to scale. B, Two specimens, side by side (ROM 61417). C, close-up of ROM 61417 (white frame in B, see also A). D, close-up of ROM 61417 (white frame in C) showing the connection of the inner stem to the base of the calyx. Scale bars: A, B = 10 mm, C = 5 mm, D = 1 mm. Abbreviations: Con - Conical structure, ES - External Sheath, IS - Inner Stem, LD - Lower Digestive tract, MD - Middle Digestive tract, OS - Outer Stem.
Figure 6.
Taphonomic variation in Siphusauctum gregarium n. gen. and n. sp.
A, complete calyx on the right and a decayed specimen on the left (ROM 61419). B, specimen with collapse and distortion of the upper part of the calyx (ROM 61420). C, Close-up of ROM 61419 (white frame in A), showing one disassociated comb-like segment. D, specimen where the outer stem has completely decayed (ROM 61418). E, Close-up of ROM 61418 (white frame in D), showing the remaining small pieces of the external sheath (other white frame, see Fig. 13E). F, partially decayed stem, showing the degradation of the outer stem (ROM 61414). Arrows indicate where the outer sheath has decayed. All scale bars = 5 mm. Abbreviations: Con - Conical structure, CS - Comb Segments, ES - External Sheath, H - Holdfast, IS - Inner Stem, LD - Lower Digestive tract, MD - Middle Digestive tract, OS - Outer Stem, TG - Transverse Groove.
Figure 7.
Cluster of 42 specimens of Siphusauctum gregarium n. gen. and n. sp. (ROM 61421).
The line drawing shows the locations and orientations of the specimens (dark grey) on the slab. See Fig. 15, Table 1 and discussion on the orientations of the clusters. The grey box; see close-up in Fig. 8. Scale bar = 50 mm.
Figure 8.
Specimen showing a ventral view of the calyx of Siphusauctum gregarium n. gen. and n. sp. (ROM 61421).
A, Cluster of laterally preserved specimens with the single ventral view highlighted. B, close-up of a ventrally compressed specimen (white frame in A) showing the six axial grooves of the comb-like segments and six openings with sediment infill (numbered 1–6). Scale bars: A = 10 mm, B = 5 mm. Abbreviations: AG - Axial Groove, ES - External Sheath, IS - Inner Stem, LD - Lower Digestive tract, OS - Outer Stem, Sed - Sediment.
Figure 9.
Shape and size variation within the stem and holdfast of Siphusauctum gregarium n. gen. and n. sp.
A–B, stem and holdfast under polarized light (A) and covered in ammonium chloride (B), arrows indicate variation in thickness of the inner stem (ROM 61413). C–D, stem and holdfast under polarized light (C) and covered with ammonium chloride (D), arrows indicate change of thickness and relief in the inner stem (ROM 61421). E–F, specimen with bent stem, under normal lighting conditions (E) and under polarized light (F) (ROM 61422). G, specimen showing consistent thickness of the inner stem and terminating in a rounded holdfast (ROM 61419). H, K, two holdfasts with different morphologies, taken under polarized light (H) and under normal lighting conditions (K) (ROM 61423 – see complete specimens Fig. 10). Arrows in H indicate where the outer stem tapers in around the inner stem above the holdfast. I, a close-up of the left holdfast in K coated with ammonium chloride, the arrows indicate grainy texture. J, the terminal ends of two stems, arrows indicate areas of unusual swellings, possibly representing decay fluids (ROM 61421). Scale bars: A–H, J, K = 5 mm, I = 1 mm. Abbreviations: H - Holdfast, IS - Inner Stem, OS - Outer Stem.
Figure 10.
Overall shape and size variations within Siphusauctum gregarium n. gen. and n. sp. (ROM 61423).
This small cluster shows variations in overall calyx shape and size, as well as, varying stem lengths and holdfast morphologies. Close-ups of the areas outlined by white frames refer to Figs. 9H, 11A and 12C. Scale bar = 10 mm. Abbreviations: H - Holdfast, IS - Inner Stem, LD - Lower Digestive tract, MD - Middle Digestive tract, OS - Outer Stem, SP - Sheath Protrusion.
Figure 11.
Shape variations in the lower calyx of Siphusauctum gregarium n. gen. and n. sp.
A, flattened appearance, arrows indicate the internal conical structure (ROM 61423 – see complete specimen Fig. 10). B, rounded base (ROM 61413 – see complete specimen Fig. 3). C, flattened appearance (ROM 61422). D, conical appearance (ROM 61416 – close-up of the counterpart of Fig. 5A). E, base of a calyx with a distinctive widening inner conical structure (see arrows) (ROM 61425). F, two specimens showing variation within the inner conical structure (see arrows) (ROM 61424). Scales bars: A–D, F = 5 mm, E = 1 mm. Abbreviations: AG - Axial Groove, Con - Conical structure, CS - Comb Segments, ES - External Sheath, IC - Inner Conical structure, IS - Inner Stem, LD - Lower Digestive tract, MD - Middle Digestive tract, OS - Outer Stem, SP - Sheath protrusion, TG - Transverse Groove.
Figure 12.
Shape variations in the upper calyx of Siphusauctum gregarium n. gen. and n. sp.
A, D (close-up), rounded top (ROM 61413). B, E (close-up), corona-like appearance at the top (ROM 61426). C, F (close-up), calyx with extended comb-like segments (ROM 61423 – see complete specimen Fig. 10). Scale bars = 5 mm. Abbreviations: A - Anus, Con - Conical structure, CS - Comb Segments, ES - External Sheath, IS - Inner Stem, LD - Lower Digestive tract, MD - Middle Digestive tract, OS - Outer Stem, Sed - Sediment, SP - Sheath Protrusion, TG - Transverse Groove, UD - Upper Digestive tract.
Figure 13.
Internal anatomy of the calyx of Siphusauctum gregarium n. gen. and n. sp.
A–C, paratype (ROM 61415) showing complete digestive tract (A) and close-ups of the gut (B and C) showing the gut enclosed within a body cavity, internal striae and transverse grooves . D, partially decayed specimen showing the overall shape of the digestive tract (ROM 61427). E, close-up of ROM 61418 (Fig. 6D), showing displacement of part of the digestive tract probably as a result of decay. Scale bars: A, D, E = 5 mm, B, C = 1 mm. Abbreviations: A - Anus, AG - Axial Groove, BC - Body Cavity, Con - Conical structure, CS - Comb Segments, ES - External Sheath, IS - Inner stem, LD - Lower Digestive tract, LS - Longitudinal Suture line, MD - Middle Digestive tract, OS - Outer Stem, S - Striae, TG - Transverse Groove, UD - Upper Digestive tract.
Figure 14.
Schematics of the internal anatomy of Siphusauctum gregarium n. gen. and n. sp.
A, longitudinal-section of the entire animal, with the major features labeled. B, cross-section of the calyx showing hexaradial symmetry. C, longitudinal-section of the calyx, showing raised comb segments above the level of the anus. Abbreviations: A - Anus, BC - Body Cavity, Con - Conical structure, CS - Comb Segments, ES - External Sheath, H - Holdfast, IC - Inner Conical structure with central tube, IS - Inner Stem, LD - Lower Digestive tract, MD - Middle Digestive tract, OS - Outer Stem, SP - Sheath Protrusion, TG - Transverse Groove, UD - Upper Digestive tract.
Table 1.
Measurement parameters related to Fig. 15.
Table 2.
Overall dimensions of Siphusauctum gregarium n. gen and n. sp.
Figure 15.
Rose diagrams showing the relative orientation of specimens of Siphusauctum gregarium n. gen and n. sp. on three different slabs.
A, ROM 61421. B, ROM 61428. C, ROM 61429. The measurements are relative as the original in-situ orientation is unknown. (See Table 1).
Figure 16.
Population variations of Siphusauctum gregarium n. gen. and n. sp within particular slabs.
Box and whisker plots: of total length (A) and calyx width (B). Grey indicates the entire data set, red indicates separate slabs with five or more individuals, and green indicates individual specimens and clusters of less than five specimens. The thick black lines indicate the mean value and the circles indicate outliers. Numbers below box and whisker plots refer to ROM numbers. N = 177.
Figure 17.
Reconstructions of Siphusauctum gregarium n. gen. and n. sp.
Left, outer appearance. Right, transparent view through the external sheath to show the internal anatomy of the calyx. (© Marianne Collins).
Figure 18.
Other stalked animals from the Burgess Shale.
A, Herpetogaster collinsi, primitive ambulacrarian (ROM 58037). B–D, Dinomischus isolatus, problematica. B, holotype (USNM 198735), C, paratype, showing a flatter base of the calyx (MCZ 1083), D, paratype showing long narrow stem and bracts pulled together at the top of the calyx (ROM 32573). E, Priscansermarinus barnetti, an enigmatic stalked animal with a thick stem (ROM 36064). F, Lyracystis radiata, a basal echinoderm with a long stem, cup shaped calyx (here surrounded by a halo of pyrite) and branchlets (ROM 57229). Scale bars: A–E = 5 mm, F = 30 mm. Abbreviations: Br - Bract, Bt - Branchlet, Ca - Calyx, Cp - Chitinous plate, Ph - Pharynx, Seg - Segment, St - Stem, Stom - Stomach, Ta - theca, Te - Tentacle, Td - Terminal disc.