Figure 1.
Count data and composition of the gut contents of Ottoia prolifica, from the middle Cambrian Burgess Shale Formation (Series 3, Stage 5; see [45]).
The pie diagrams illustrate differences in the diet of Ottoia from the Raymond Quarry (RQ+RT) and the Walcott (WQ+WT) Quarry. Hyolithids dominate in the gut contents from the Raymond Quarry followed in decreasing order by brachiopods, agnostids, trilobites, bradoriids, ASE (presumed wiwaxiids), SLE (presumed polychaetes) and trilobites. In the Walcott Quarry, three almost equally represented groups (SLE, hyolithids and ASE) are prevalent, followed by bradoriids, trilobites, agnostids and brachiopods. (1) guts containing skeletal fragments and/or undetermined material and a variable proportion of sediment; (2) guts containing skeletal elements or fragments that belong to animal species present in the Burgess Shale biota; (3) guts containing elements that belong to a single species (e.g. only hyolithid skeletal elements). Empty guts generally appear as a colored or reflective strip running axially from the pharynx to the anus. ASE, almond-shape elements (presumed wiwaxiid sclerites); RQ, RT, collection specimens from the Raymond Quarry and talus (Royal Ontario Museum); SLE, setae-like elements (presumed polychaete chaetae); USNM, collection specimens from the National Museum of Natural History, Smithsonian Institution, Washington D.C.; WQ, WT, collection specimens from the Walcott Quarry and talus (Royal Ontario Museum). Raw data in Table S1.
Figure 2.
General morphology of Ottoia prolifica
from the middle Cambrian Burgess Shale. A, ROM 61780a, high concentration of complete specimens. B–D, ROM 61759, ROM 61752 and ROM 61757, complete specimens. E, F, ROM 61751 and ROM 61765, details of anterior part. G, ROM 61760, details of introvert bearing curved scalids. H, I, ROM 61769 and ROM 61764, details of posterior part showing bursa and posterior hooks. Abbreviations: a, anus; an, trunk annulation; bu, bursa; gu, gut; in, introvert; m, mouth; ph, posterior hook; pt, pharyngeal teeth; px, pharynx; px(e), everted pharynx; px(i), inverted pharynx; sc, scalid; tr, trunk. Scale bar: 1 cm for A–D and 5 mm for E–I.
Figure 3.
General morphology of Recent priapulid worms exemplified by Priapulus caudatus collected from near the Kristineberg Marine Station, Gullmarfjord, Sweden, depth ca. 30 m.
A, B, general view of a live specimen in sea water and simplified section through body showing major anatomical features. C, section through pharynx (sclerotized pharyngeal teeth in orange; introvert removed. D, F, frontal view of a slightly everted pharynx showing pentagonal pattern of pharyngeal teeth around mouth opening and details of pharyngeal teeth. E, G, scalid rows along bulbous introvert and details of scalids (tip perforated). H–J, feces of Priapulus caudatus filled with compacted undigested material and enclosed by a transparent membrane, bundles of undigested polychaete chaetae and undetermined gut contents (mainly sediment and detritus of various origin). D–G, I, J, are scanning electron micrographs of dessicated specimens. Abbreviations: a, anus; an, trunk annulation; bu, bursa; ca, caudal appendage; cc, coelomic cavity; fc, feces contents; fm, feces membrane; go, gonads; gu, gut; in, introvert; m, mouth; pm, pharyngeal muscles; pt, pharyngeal tooth; px, pharynx; rm, retractor muscle; sc, scalid; sr, scalid row; tr, trunk. Scale bar: 1 cm for A, B; 5 mm for C; 500 µm for D, E, H; 200 µm for F; 100 µm for G; 10 µm for I; 5 µm for J.
Figure 4.
Elemental mapping of the gut of Ottoia prolifica
from the middle Cambrian Burgess Shale. The mapping reveals anatomical partitioning of the gut, with elevated C, Fe and P that probably reflects its organic-rich original composition and early diagenetic mineralizations in pyrite, apatite or calcite. A–E, ROM 61758b. A, B, general view under normal and polarized light (white arrow to indicate mapped area). C, D, back scattered image of gut showing patches of carbonaceous film; this film is interpreted as remains of the gut wall, rather than gut contents. E, elemental mapping. Abbreviations: a, anus; cf, carbonaceous film; gc, gut content; gu, gut; m, mouth. Scale bar: 1 cm for A, B; 5 mm for E; 1 mm for C; 20 µm for D.
Figure 5.
Sedimentary ingesta within the gut of Ottoia prolifica
from the middle Cambrian Burgess Shale Formation. A–D, USNM 196195, three-dimensionally preserved gut contents, general view and thin section; gut material (C) is easily distinguished from the matrix (D) by its brown colour due to high organic content. Crystals (in white) are not specific to the gut and are observed elsewhere in the matrix though smaller and less concentrated; they are interpreted as sponge spicules [21]. E, F, ROM 61755a, isolated fragment of gut content seen in transverse section. G, H, ROM 61754, gut contents showing small skeletal fragments and undetermined elements embedded in sediment. I, J, ROM 61755a, transverse section through upper part of gut content; the uppermost thin layer possibly represent the gut wall. K, ROM 61755b, thin carbonaceous film overlying gut contents, possibly representing the gut wall. gc, gut contents; se, sediment; sf, skeletal fragment; ue, undetermined element. A–D, courtesy L. Wilson (see also [21]). A, G are light photographs; B and D were taken in transmitted light; E, F, H-K are scanning electron micrographs (K, back-scattered image). Scale bar: 5 mm for A; 2 mm for G; 500 µm for B, H; 100 µm for C, D; 50 µm for K; 10 µm for E, I; 5 µm for F; 2 µm for J.
Figure 6.
Hyolithids, brachiopods and arthropods within the gut of Ottoia prolifica from the middle Cambrian Burgess Shale.
A–C, ROM 61747, with 4 hyolithid shells (Haplophrentis carinatus), their apex pointing anteriorly. D, ROM 61767, hyolithid with operculum and conch in connexion. E, F, ROM 61749, hyolithid conch and a pair of disarticulated helens. G, ROM 61774, hyolithid conch and disarticulated operculum. H, USNM 202777, hyolithid conch within the posteriormost part of the gut (bursa everted). I–K, ROM 61779 with two brachiopods (Micromitra burgessensis) in posterior gut. L, M, ROM 61775 with complete agnostid arthropod (Ptychagnostus praecurrens) within the anterior gut. N, O, ROM 61777 with a trilobite pygidium (Ehmaniella burgessensis) inside the gut. P, ROM 61785 with a trilobite cephalon (E. burgessensis). Abbreviations: a, anus; ag, agnostid; an, trunk annulation, ANT, anterior; ase, almond-shape element; br, brachiopod; br1, br2, from anterior, brachiopod 1 and 2; bu, bursa; ce, cephalon; co, hyolithid conch; gc, gut content; gu, gut; gw, gut wall; h1–h4, from anterior, hyolithid 1 to 4; he, helen; in, introvert; m, mouth; op, hyolithid operculum; ph, posterior hook; POST, posterior; pt, pharyngeal teeth; py, pygidium; tr, trunk. Scale bar: 1 cm for A, I, L; 5 mm for B, C, E, H, M; 2 mm for K; 1 mm for D, F, G, J, N–P.
Figure 7.
Hyolithids in the gut of Ottoia prolifica
from the middle Cambrian Burgess Shale. A, ROM 61753a, showing 3 hyolithids preserved with their opercule. B–E, ROM 61782, with 5 hyolithid shells (Haplophrentis carinatus) within the gut, their apex pointing anteriorly; general view and details. F–H, USNM 196381, with 6 hyolithid shells within the gut. I, USNM 188604, with 3 hyolithids (h3 close to the anus). Abbreviations: ANT, anterior; an, trunk annulation; co1–co3, hyolithid conch 1 to 3; gc, gut content; gu, gut; he, helen; h1–h6, from anterior, hyolithid 1 to 6; op1–op3, hyolithid operculum 1 to 3; lo, loop; ph, posterior hook; POST, posterior; tr, trunk. Scale bar: 1 cm for B, F, H, I; 5 mm for A, C–E; 2 mm for G.
Table 1.
Hyolithid elements in the gut contents of Ottoia prolifica from the Middle Cambrian Burgess Shale: countings and measurements.
Table 2.
Brachiopod elements in the gut contents of Ottoia prolifica from the Middle Cambrian Burgess Shale: countings and measurements.
Table 3.
Arthropod elements in the gut contents of Ottoia prolifica from the Middle Cambrian Burgess Shale: countings and measurements.
Table 4.
Almond-shape elements (ASE; see Fig. 12) in the gut contents of Ottoia prolifica from the Middle Cambrian Burgess Shale: countings and measurements.
Figure 8.
Other skeletal elements in the gut of Ottoia prolifica
from the Middle Cambrian Burgess Shale. A–D, USNM 196204, with articulate brachiopod, possibly Diraphora bellicostata [1], [50], [51]. E, ROM 61756, with the inarticulate brachiopod Micromitra burgessensis [1], [50], [51] and undetermined gut contents. F, ROM 61750 with Micromitra burgessensis and a hyolithid. G, H, ROM 61770 with agnostid (possibly Pagetia bootes [1], [52]), general view and close-up. I, J, ROM 61783 with complete agnostid and hyolithid. Abbreviations: ag, agnostid; an, trunk annulation; ANT, anterior; br, brachiopod; ce, cephalon; gc, gut contents; gu, gut; h, hyolithid; op, operculum of hyolithid; ph, posterior hook; POST, posterior; py, pygidium. All light photographs. Scale bar: 1 cm for A, G; 2 mm for B–F, H–J.
Figure 9.
Other skeletal elements in the gut of Ottoia prolifica
from the middle Cambrian Burgess Shale. A, B, ROM 61785, showing gut contents with a trilobite cephalon (probably Ehmaniella burgessensis [1], [52]). C, D, ROM 61761, with contents containing trilobite remains (e.g. thoracic segments). E, USNM 196425, with gut contents containing possible trilobite remains. F, G, ROM 61776, with bradoriid arthropod [53] in anterior part of gut. H, I, ROM 61778, with possible shields of bivalved arthropods in posterior gut, general view and detail. J, ROM 61771, with possible shields of bivalved arthropods. Abbreviations: ANT, anterior; ba, bivalved arthropod (shield); bd, bradoriid; ce, cephalon; gc, gut contents; gu, gut; ph, posterior hook; POST, posterior; px(e), everted pharynx; tr, trilobite; ts, thoracic segment. All light photographs (J, whitened with ammonium chloride). Scale bar: 1 cm for A–C; 5 mm for F; 2 mm for D, E, G; 1 mm for I, J.
Figure 10.
Setae-like elements (SLE) within the gut of Ottoia prolifica from the middle Cambrian Burgess Shale, compared with the chaetae of Burgessochaeta.
A–D, ROM 61755b, general view, accumulations and details of SLE in gut. E, ROM 61772b, SLE in gut. F, ROM 61746a, SLE in cross section, preserved in aluminosilicate. G–I, Burgessochaeta setigera (Polychaeta; [1], [54]); G, ROM 56967 complete specimen with numerous chaetae on parapodia; H, ROM 56968a(1), ROM 56968a(1), decayed specimen; I, ROM 56968a(2), chaetae on parapodia. J, ROM 56969a, bundle of chaetae (compare with C). Abbreviations: ANT, anterior; bd, possible bundle of SLE; cf, carbonaceous film; ch, chaetae; gc, gut content; gu, gut; pa, parapodium; POST, posterior. Scale bar: 1 cm for A, G; 1 mm for E, H–J; 500 µm for B; 100 µm for D; 20 µm for F.
Figure 11.
Comparative measurements between the setae-like elements (SLE) within the gut of Ottoia prolifica, the chaetae of Burgessochaeta setigera
[1], [59] and sponge spicules. The diameter of most spicules of sponges occurring in the same horizons as Ottoia ranges between 10 and 20 µm and is lower than that of most SLE. Interpolation (up right diagram) suggests that SLE are undigested chaetae of small individuals of Burgessochaeta, possibly between 5 and 10 mm long. Size distribution of chaetae (blue) and SLE (red) lengths are given for three well-preserved Burgessochaeta specimens (A–C) and one Ottoia gut content (number 4). Diagonella (bottom left) is a typical sponge in the Burgess Shale biota. Abbreviations: ANT, anterior; BL, body length; bo, body; ch, chaetae; CL, chaeta length; pa, parapodium; POST, posterior; sp, spicule. 1, ROM 61786b; 2, ROM 61787; 3, ROM 61772b; 4, ROM 61755; 5, ROM 61788; 6, ROM 61789; 7, ROM 61746. A, ROM 56968a; B, ROM 56968b; C, ROM 56967; D, ROM 56968b; E, ROM 56969a.
Table 5.
Numerical abundance of Ottoia prolifica and the animal taxa that constituted its diet (evidence from gut contents and feeding assemblages, present paper) through successive bed assemblages in the Great Phyllopod Bed (Walcott Quarry Member, Burgess Shale Formation, Middle Cambrian).
Figure 12.
Almond-shape elements (ASE) within the gut of Ottoia prolifica from the middle Cambrian Burgess Shale, compared to the sclerites of Wiwaxia
[60]. A–C, G, H, ROM 61768, general views, and details of ASE (bulbous feature in G is an artefact due to mineralization). D, ROM 61763b with aligned ASE. E, ROM 61773a, with ASE and other skeletal elements. F, ROM 61781a, three aligned ribbed ASE. I, ROM 61745b, isolated ASE within gut. J, ROM 61747, Wiwaxia corrugata [1], [60] with sclerites in situ. K, L, ROM 56965, W. corrugata, ribbed sclerite and general view of decayed specimen. Abbreviations: a, anus; ANT, anterior; ase, almond-shape element; gc, gut content; m, mouth; ma, mouth apparatus; POST, posterior; scs, scale-like sclerite; se, skeletal element; sps, spine-like sclerite. Scale bar: 5 mm for A–C, J, L; 2 mm for D, E, K; 1 mm for F–I.
Figure 13.
Three fossil associations from the Burgess Shale Formation, middle Cambrian, showing Ottoia prolifica around and below the carcass of the arthropod Sidneyia inexpectans and suggesting scavenging behaviour in Ottoia prolifica.
A, B, USNM 196241, showing at least 5 worms around the decaying carcass of Sidneyia. This specimen was interpreted [32] as a death assemblage with the worms feeding around the collapsed and decaying carcass of Sidneyia inexpectans. I follow this interpretation here, although the number of worms is more likely to be five than nine [32]. C, D, ROM 61748a, showing an assemblage very similar to USNM 196241; four worms form a wreath-like arrangement around the remains of Sidneyia. E, F, USNM 250218, showing a curved specimen of Ottoia closely associated with Sidneyia. All light photographs (A, courtesy Jean-Bernard Caron, ROM). Scale bar: 1 cm. Abbreviations: an, annulation; dg, digestive glands; gc, gut content; gu, gut; hy, hyolithid conch; ph, posterior hook; px, pharynx; w1–5, worm (Ottoia) 1–5.
Figure 14.
Major components of the diet of Ottoia prolifica
from the middle Cambrian Burgess Shale. 1, hyolithids (Haplophrentis); 2, brachiopods (Micromitra); 3, polychaete worms (Burgessochaeta); 4, bradoriids (Liangshanella); 5, trilobites (Ehmaniella); 6, agnostids (Ptychagnostus); 7, 8, carcasses of Sidneyia and Wiwaxia. (A–C), feeding behavior of Ottoia: detection of food via possible chemical cues and ingestion. gu, gut; in, introvert with spiny scalids; px(e), everted pharynx; px(i), inverted pharynx; sc, scalid; tr, trunk.
Table 6.
Diet of Recent macrobenthic priapulid worms exemplified by Priapulus caudatus and Halicryptus spinulosus (see morphology in Fig. 3).