Arthropod appendages from the Weeks Formation Konservat-Lagerstätte: new occurrences of anomalocaridids in the Cambrian of Utah, USA

Abstract

The Guzhangian Weeks Formation (House Range, Utah, USA) contains a virtually unstudied but diverse assemblage of "soft-bodied" organisms. This fauna includes several enigmatic appendages of arthropods that are described in this contribution. Six appendages (two isolated and four paired appendages) are interpreted as frontal appendages of a probably new species of Anomalocaris. They are characterized by a slender morphology, 14 podomeres, ventral spines alternating in size, up to three auxiliary spines per ventral spine, and only two dorsal spines. Another isolated appendage is also tentatively assigned to Anomalocaris, but it exhibits a more robust morphology, a stronger distal tapering, and apparently simple ventral spines, suggesting that it may represent a distinct taxon. These frontal appendages represent the youngest occurrence of anomalocaridids in Laurentia and demonstrate the persistence of older, Burgess Shale-type taxa in the Weeks Formation. An assemblage of four antenniform and six robust and heavily-armed appendages is also described. These are interpreted as the serially arranged, anterior appendages of a single individual of an undetermined arthropod species. This association of three pairs of robust, spiny appendages with two pairs of antenniform structures in a Cambrian arthropod is unique. •

Aysheaia prolata from the Utah Wheeler Formation (Drumian, Cambrian) is a frontal appendage of the radiodontan Stanleycaris

“…Peytoia nathorsti and Hurdia victoria (Briggs et al 2008;Pates et al in press) are known in both regions from frontal appendages, mouthparts, and carapace material. Anomalocaris has also been described from post cephalic remains in both the Spence Shale and Wheeler Formation (Briggs et al 2008), and isolated frontal appendages in the younger (Guzhangian) Weeks Formation (Lerosey-Aubril et al 2014). The Wheeler Formation specimen is the youngest stratigraphic occurrence of Stanleycaris, expanding its temporal range from the BathyuriscusElrathina Zone to the Ptychagnostus atavus Zone.…”

“…Despite their fundamentally soft-bodied construction, there is a comprehensive record of radiodontan diversity owing to the preferential preservation of their sclerotized frontal appendages (e.g., Caron et al 2010;Daley and Peel 2010;Wang et al 2013;Lerosey-Aubril et al 2014;Vinther et al 2014). Recent work has expanded the palaeobiogeographic and stratigraphic occurrence of radiodontan taxa previously known only from the Cambrian (Stage 5) Burgess Shale in British Columbia, including new reports from the Cambrian (Series 3) of Utah (Pates et al in press).…”

Making sense of ‘lower’ and ‘upper’ stem‐group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848

“…6) also apply Arthropoda inappropriately for a scion including Radiodonta, upper stem‐Euarthropoda and Euarthropoda. Indeed, Legg & Vannier (, p. 549; see also Lerosey‐Aubril et al , ) explicitly state that their use of Arthropoda follows an apomorphy‐based definition that once again focuses on the presence limb arthropodization; similarly to Liu et al (), however, this usage does not conform to any of the possible classifications of Arthropoda in a strict sense (see Table ). In another comparable case, the cladogram of Ma et al (, fig.…”

Hurdiid radiodontans from the middle Cambrian (Series 3) of Utah

“…sp. from the younger (Guzhangian) Weeks Formation in Utah have been described by Lerosey-Aubril et al (2014). No new Anomalocaris appendages or bodies were identified during the course of this study.…”