© Royal Ontario Museum. Photo: Jean-Bernard Caron
Trilobites are extinct euarthropods, probably stem lineage representatives of the Mandibulata, which includes crustaceans, myriapods, and hexapods (Scholtz and Edgecombe, 2006).
Burlingia – after Lancaster Burling, then with the United States National Museum, who discovered the first specimens on Mount Stephen in 1907; Burling was later employed by the Geological Survey of Canada to work on Cambrian strata and fossils in the Rockies.
hectori – after Sir James Hector, surgeon and geologist on the Palliser Expedition (1857-1860), and the man at the heart of the apocryphal tale according to which Kicking Horse Pass and the Kicking Horse River received their names.
Burgess Shale and vicinity: none.
Other deposits: Burlingia ovata from the Middle Cambrian of China; three species of Schmalenseeia from the early Middle to early Upper Cambrian of Sweden, China, Australia, Siberia, England, and Newfoundland (Whittington, 1994).
Found originally at a single locality just north of the Trilobite Beds on Mount Stephen, the species has since been identified from the Middle Cambrian of Öland, Sweden (ex-Burlingia laevis – see Whittington, 1994).
The first three specimens of this strange little trilobite were found by Lancaster Burling when he accompanied Charles Walcott on his first visit to Mount Stephen in 1907. These were named and described the following year (Walcott, 1908a) and the best specimen was re-illustrated in Walcott’s popular account (1908b) in the Canadian Alpine Journal. Its tiny size and very odd morphology immediately set Burlingia apart from all other trilobites except for another diminutive form, Schmalenseeia amphionura, which had been described just 5 years earlier from the Upper Cambrian of Sweden. Species of both genera are now known to occur as rare elements in Cambrian faunas around the world, however, despite a thorough redescription (Whittington, 1994), burlingiids have consistently proven difficult to fit into any current trilobite phylogeny.
Hard parts: the largest of the known Mount Stephen specimens of Burlingia hectori is only 8 mm in length; other complete individuals are 5-6 mm long. Dorsal shields vary from nearly circular to elongate ovoid in outline and specimens appear almost flat due to mechanical distortion and compression of the very thin exoskeleton. The cephalon has a semicircular to rounded triangular shape with the genal corners acutely angled, but not drawn out into spines.
Burlingia has proparian facial sutures, meaning both branches of the suture lie anterior of the genal angle and are directed obliquely forward, setting off small trapezoidal free cheeks. The narrow, forward-tapering glabella has very little independent relief, and extends over the posterior two-thirds of the cephalic mid-length. Low crescentic eye lobes lie close to the glabella at about cephalic mid-length, bounded by the proparian sutures. The thorax consists of 14 segments, with only a slight change in slope setting off the low axial lobe from the flat, unfurrowed pleurae. The overlapping pleurae, with acutely angled tips, curve progressively more strongly to the rear; the last pair extend directly backwards past the notched tip of the tiny parallel-sided pygidium.
Unmineralized anatomy: not known.
Exceedingly rare, present only at the Mount Stephen Burlingia locality.
The small adult size, peculiar morphology, thin exoskeleton, and wide geographical distribution of burlingiids have all been considered suggestive of a planktonic mode of life, but this hypothesis has not met with universal agreement (Whittington, 1994), and the lifestyle of Burlingia hectori remains enigmatic.
RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116 (5): 1-277.
SCHOLTZ, G. AND G. D. EDGECOMBE. 2006. The evolution of arthropod heads: reconciling morphological, developmental and palaeontological evidence. Development Genes and Evolution, 216: 395-415.
WALCOTT, C. 1908a. Cambrian Geology and Paleontology I. Cambrian trilobites. Smithsonian Miscellaneous Collections, 53(2): 13-52.
WALCOTT, C. D. 1908b. Mount Stephen rocks and fossils. Canadian Alpine Journal, 1: 232-248.
WHITTINGTON, H. B. 1994. Burlingiids: small proparian Cambrian trilobites of enigmatic origin. Palaeontology, 37: 1-16.