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Taxonomy from Sumrall & Zamora 2011. Diagnosis (Sumrall & Zamora 2011, p. 441): "Large Isorophus with moderately curved ambulacra and proportionately wide peripheral rim." Identified by oilshale using Sumrall & Zamora 2011. References: Sumrall, Colin D. & Zamora, Samuel (2011) Ordovician edrioasteroids from Morocco: faunal exchanges across the Rheic Ocean. Journal of Systematic Palaeontology, Vol. 9, Issue 3, September 2011, 425–454.

Synonym: Pleurocystites robustus Billings, 1854. Alternative spelling: Pleurocystis. Taxonomy from fossilworks.org. Diagnosis (Sprinkle et al., 1985): “Theca rounded-triangular, nearly symmetrical; 3 rhombs elliptical, dichopores occupying less than 40% of sutures; periproct occupying 70% of lower side, about 680-700 periproctals, no rectal lobe, anal pyramid away from margin; ornament composed of medium growth lines and few ridges radiating to the plate sides and corners; brachioles having large groove extending up aboral side, cover plates fairly large; proximal stem slowly tapering and moderately ridged.” ID determined by oilshale. Reference: Billings, E. (1874). Paleozoic Fossils, v. II, pt. I. Canada Geological Survey 1-144 Parsley, R. L. (1970). Revision of the North American Pleurocystitidae (Rhombifera-Cystoidea). Bulletins of American Paleontology 58:135-213. Sprinkle, J., Henry, L., Zimmer, F., Kelley, L., & Whiteley, J. (1985). New Pleurocystites from the Bromide Formation of Oklahoma. Journal of Paleontology, 59(6), 1476-1480. Brower, J. (1996). Growth and Functional Morphology of Pleurocystites Squamosus Billings, An Ordovician Rhombiferan Echinoderm. The Paleontological Society Special Publications, 8, 48-48. doi:10.1017/S2475262200000502 Paton, T. (2017). Paleo Pompeii; Genesis and Preservation of an Upper Ordovician Mounded Hardground with a Diverse Encrusting Community. Master-thesis, University of Cincinnaty. Paton, T. and Brett, C. E. (2019). Revised stratigraphy of the middle Simcoe Group (Ordovician, upper Sandbian-Katian) in its type area: An integrated approach. Canadian Journal of Earth Sciences 57(1).

Nice specimen of this interesting trilobite. The species name titan refers to this species being significantly bigger than the Czech typespecies Declivolithus alfredi. The distinctive head-shape of this suspension feeder shows this trilobite was probably adapted to fast swimming. Here's a paper describing the new species and the type locality: http://www.geology.cz/bulletin/fulltext/1649_Fortey_170930.pdf