The Burgess Shale

Titanokorys gainesi

A sediment sifter with a giant carapace

Titanokorys gainesi, holotype ROMIP 65168

Taxonomy:

Kingdom: Animalia
Phylum: Arthropoda
Higher Taxonomic assignment: Order Radiodonta, Family Hurdiidae
Species name: Titanokorys gainesi
Remarks:

With its single pair of jointed frontal appendages, lateral swimming flaps, and circular mouth structure, Titanokorys possesses all the hallmarks of Radiodonta, part of the stem group to the true arthropods which also includes the iconic Anomalocaris (Collins 1996). The frontal appendages with comb or rake-like inner spines are characteristic of the radiodont family Hurdiidae. Phylogenetic analysis has found it to be closely related to Cambroraster from the Burgess Shale and Zhenghecaris from the Chengjiang deposit, which share similarities in carapace shape and a large number of finely-spaced spines on the appendages (Caron and Moysiuk 2021).

Described by: Caron and Moysiuk
Description date: 2021
Etymology:

Titanokorys – from Titans, a group of powerful Greek deities of great sizes, in reference to the large size of the central carapace and from the Greek word Korys meaning helmet.

gainesi – after Robert R. Gaines, Professor of Geology at Pomona College, who was instrumental in the co-discovery of the Marble Canyon fossil deposit in 2012.

Type Specimens: Holotype ROMIP 65415; Paratypes ROMIP 65168, 65741, 65748, and 65749, at the Royal Ontario Museum.
Other species:

Burgess Shale and vicinity: None
Other deposits: None

Age & Localities:

Age:
Middle Cambrian, Wuliuan Stage, upper part of the ‘thick’ Stephen Formation (Burgess Shale) (around 507 million years old).
Principal localities:

Marble Canyon and Mount Whymper / Tokumm Creek, Kootenay National Park, British Columbia.

History of Research:

Brief history of research:

Several specimens of Titanokorys were discovered at the Marble Canyon and North Tokumm sites in Kootenay National Park in 2014 and 2018. Because of their distinctive shape, large size, and resemblance to the smaller Cambroraster (nicknamed “spaceship”), the head carapaces were nicknamed the “mothership.” The genus and species were formally described in 2021 (Caron and Moysiuk 2021).

Description:

Morphology:

The defining feature of Titanokorys gainesi is its large dorsal carapace. This is roughly elliptical in overall shape. Frontally this carapace has a small spine flanked by a pair of blunt lobes. The rear sides of the carapace are developed into short, wing-like projections. Each “wing” has a small spine along its inner margin. The rear central part of the carapace extends into a bilobate projection. Between the lateral “wings” and bilobate projection are notches that presumably accommodated the eyes. On the underside, the head is protected by two additional plates, shaped like elongate paddles and joined together at the front by their narrow ends, each of which bears a stout, downward-directed spine. All three plates are covered in longitudinal rows of small bumps. A circular, tooth-lined jaw and a pair of jointed frontal appendages with five long, curving, rake-like inner spines are located on the underside, near the front of the head. The body bears rows of stacked gill blades.

Abundance:

Titanokorys is rare in Kootenay National Park, being known from just twelve specimens. Only disarticulated frontal appendages, mouthparts, carapace elements, and gills are known.

Maximum Size:
About 500 mm.

Ecology:

Life habits: Mobile, Nektobenthic
Feeding strategies: Carnivorous
Ecological Interpretations:

Like other hurdiids, Titanokorys shows adaptations to sweep feeding. Specifically, the rake-like inner spines on its stout frontal appendages form a rigid basket-like apparatus of spines surrounding the mouth, which could have functioned to disturb the sediment, sift out burrowing organisms, and move them into the mouth for further processing. Compared to related hurdiids like Hurdia and Stanleycaris, the particularly finely-spaced, strong, hooked secondary spines on the inner spines could have enabled capture of minute benthic organisms, although larger prey may also have been consumed. As the largest animal known from the Marble Canyon and Tokumm communities, Titanokorys would have been at the top of the food chain. Titanokorys shared the environment with the slightly smaller Cambroraster, which probably employed a similar mode of feeding, although body size differences may have entailed distinct prey size niches (Moysiuk and Caron 2019; Caron and Moysiuk 2021). Respiration would have been accomplished primarily through the rows of gill blades on the body (Daley et al. 2013).

References:

  • CARON, J.-B. and MOYSIUK, J. 2021. A giant nektobenthic radiodont from the Burgess Shale and the significance of hurdiid carapace diversity. Royal Society Open Science, 8: 210664.
  • COLLINS, D. 1996. The “evolution” of Anomalocaris and its classification in the arthropod class Dinocarida (nov.) and order Radiodonta (nov.). Journal of Paleontology, 70: 280–293.
  • DALEY, A. C., BUDD, G. E. and CARON, J.-B. 2013. Morphology and systematics of the anomalocaridid arthropod Hurdia from the Middle Cambrian of British Columbia and Utah. Journal of Systematic Palaeontology, 11: 743–787.
  • MOYSIUK, J. and CARON, J.-B. 2019. A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources. Proceedings of the Royal Society B, 286: 20191079.
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