Abstract
AbstractThe stem‐group priapulid Ottoia Walcott, 1911, is the most abundant worm in the mid‐Cambrian Burgess Shale, but has not been unambiguously demonstrated elsewhere. High‐resolution electron and optical microscopy of macroscopic Burgess Shale specimens reveals the detailed anatomy of its robust hooks, spines and pharyngeal teeth, establishing the presence of two species: Ottoia prolifica Walcott, 1911, and Ottoia tricuspida sp. nov. Direct comparison of these sclerotized elements with a suite of shale‐hosted mid‐to‐late Cambrian microfossils extends the range of ottoiid priapulids throughout the middle to upper Cambrian strata of the Western Canada Sedimentary Basin. Ottoiid priapulids represented an important component of Cambrian ecosystems: they occur in a range of lithologies and thrived in shallow water as well as in the deep‐water setting of the Burgess Shale. A wider survey of Burgess Shale macrofossils reveals specific characters that diagnose priapulid sclerites more generally, establishing the affinity of a wide range of Small Carbonaceous Fossils and demonstrating the prominent role of priapulids in Cambrian seas.
Highlights
S T E M-group priapulid worms were a conspicuous component of level-bottom Cambrian faunas (Conway Morris 1977; Conway Morris and Robison 1986; Budd and Jensen 2000; Han et al 2004; Caron and Jackson 2008; Zhao et al 2014), even though their modern macroscopic counterparts are in general restricted to marginal, typically anaerobic settings
We examined Ottoia macrofossils from the Burgess Shale (Cambrian Series 3, Stage 5; Fossil Ridge, British Columbia), a series of moderately metamorphosed mudstones deposited below storm wave base at the outboard edge of the Western Canada Sedimentary Basin (Piper 1972) (Fig. 1)
Our new observations emphasize the systematic importance of priapulid sclerite morphology
Summary
S T E M-group priapulid worms were a conspicuous component of level-bottom Cambrian faunas (Conway Morris 1977; Conway Morris and Robison 1986; Budd and Jensen 2000; Han et al 2004; Caron and Jackson 2008; Zhao et al 2014), even though their modern macroscopic counterparts are in general restricted to marginal, typically anaerobic settings (van der Land 1970; Oeschger and Vetter 1992). Despite intense sampling effort (Dornbos and Chen 2008; Zhao et al 2014), there are no confirmed records of Ottoia macrofossils outside the Burgess Shale
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