Byronia annulata (ROM 56648). Plate 1, figures 9 and 9a of Walcott (1908) and counterpart of original specimen collected in 1975 from the Trilobite Beds on Mount Stephen. (The part is at the Smithsonian Institution). Approximate specimen length = 95 mm. Specimen dry – direct light. Trilobite Beds on Mount Stephen.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Byronia represents the purported sessile polyp stage of a scyphozoan jellyfish that builds tapered, chitinous tubes fixed to the substrate by an attachment disc (Zhu et al., 2000).
Byronia – for Byron Edmund Walker (1848-1924), Canadian banker, amateur palaeontologist, and co-founder of the Royal Ontario Museum.
annulata – from the Latin annulatus, “ring-like,” in reference to distinct annular (transverse) ridges.
Burgess Shale and vicinity: Many shared similarities suggest that other thecate Burgess Shale fossils such as Tubulella flagellum, Sphenothallus sp., Cambrorhytium major, and C. fragilis may be related to Byronia.
Other deposits: B. natus from the Kaili Formation (Zhu et al., 2000). Other species occur in the Cambrian worldwide, including in Australia, in particular B. displosa, B. mirrabookaensis and B. petila (Bischoff, 1989).
The Trilobite Beds and additional localities on Mount Stephen. The Walcott and Raymond Quarries on Fossil Ridge.
On August 1887, the Toronto meeting of the British Association for the Advancement of Science was followed by a special geological rail tour to western Canada organized by Byron Edmund Walker (a prominent Canadian banker). One of the excursion highlights was a visit to the Mount Stephen Trilobite Beds, after which Walker loaned his personal collection of Mount Stephen fossils to Canada’s leading Cambrian palaeontologist, George F. Matthew, of Saint John, New Brunswick. In 1899, Matthew published a series of new descriptions based on this material, including Byronia annulata, named in gratitude for Walker’s generosity. Matthew considered this rare form to be a flattened, conical worm tube, and illustrated the only complete specimen (which would have been considered the holotype) in an engraving. Walker donated his entire fossil collection to the University of Toronto in 1904, and in 1913 it was transferred to the new Royal Ontario Museum of Palaeontology. Unfortunately, the single complete specimen of Byronia annulata described by Matthew remained unrecognized until it was “rediscovered” in the ROM collections in 2009. In the meantime, Byronia had been reinterpreted as the theca of a cnidarian polyp based on specimens from other sites.
The chitinous or chitinophosphatic tube (theca) of Byronia annulata is long and conical, originally circular or oval, with a cross section approaching 10 mm in diameter. Thecae may be almost straight or may show varying degrees of curvature, and are almost always flattened by compression. Preservation of the multilamellar thecal wall is occasionally quite good, with patches of dark, glossy material contrasting strongly against the shale matrix. The external surface shows distinctive closely-spaced annular (transverse) ridges with very fine longitudinal (lengthwise) ridges between them. Complete thecae may show a small attachment disc at the narrow end. Individuals or clusters of smaller, narrower thecae resembling a form called Tubulella flagellum are occasionally found closely associated with Byronia, but it is not known if these grew attached to, or clonally “budded” from, the larger tubes. As yet, no soft tissues of Byronia annulata have been described.
Rare, known mostly from the Trilobite Beds on Mount Stephen.
The theca of Byronia was likely attached to the substrate using an apical disc which is usually broken off. The absence of soft tissue preservation makes the assignment to a particular feeding strategy tentative. By comparison with forms such as Cambrorhytium, a carnivorous or suspension feeding habit seems possible.
BISCHOFF, C. O. 1989. Byroniida new order from early Palaeozoic strata of eastern Australia (Cnidaria, thecate scyphopolyps). Senkenbergiana Lethaea, 69(5/6): 467-521.
CONWAY MORRIS, S. AND R. A. ROBISON. 1988. More soft-bodied animals and algae from the Middle Cambrian of Utah and British Columbia. University of Kansas Paleontological Contributions, Paper, 122: 23-48.
MATTHEW, G. F. 1899. Studies on Cambrian faunas, No. 3. Upper Cambrian fauna of Mount Stephen, British Columbia. The trilobites and worms. Transactions of the Royal Society of Canada, Series 2, 4: 39-66.
RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116(5): 277 p.
WALCOTT, C. D. 1908. Mount Stephen rocks and fossils. Canadian Alpine Journal, 1: 232-248.
ZHU, M.-Y., H. VAN ITEN, R. S. COX, Y. L. ZHAO, B.-D. ERDTMANN. 2000. Occurrence of Byronia Matthew and Sphenothallus Hall in the Lower Cambrian of China. Paläontologische Zeitschrift, 74: 227-238.
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