490


Journal of Paleontology 92(3):488–505


fully articulated crinoid calyces with complete arms are uncom- mon, and intact stems and holdfasts in association with calyces are exceedingly rare. Likewise, other echinoderms are also susceptible to rapid disarticulation because of their multi- elemental skeleton. Only exceptional environmental conditions will result in preservation of complete echinoderm specimens (Brett et al., 1997). As a result, the exceptional preservation of echinoderm material from the Lake Simcoe region merits desig- nation of the fauna as a Konservat-Lagerstätte. Echinoderms from the Brechin Lagerstätte most commonly


occur either on hardground surfaces fromthe uppermost 3–4mof the Bobcaygeon Formation or in high-density clusters on non- hardground bedding planes,which aremost common in the lower 2–3m of the Verulam Formation, but can also be found in the upper Bobcaygeon (Brett and Taylor, 1999). Although echino- derms are exceptionally preserved in both types of assemblages, those fromhardground surfaces are more likely to retain holdfast structures. This in situ preservation indicates that rapid, episodic events repeatedly buried the community, resulting in preservation of intact arms, stems, and attachment structures (Brett and Baird, 1986). Specimens preserved in high-density assemblages are usually found in shale-filled topographic lows and may be associated with skeletal debris (Brett and Taylor, 1999); Cupulocrinus and Pleurocystites are particularly common in these assemblages. Although crinoid stems and holdfasts are less commonly preserved in these horizons, calyces and feeding structures typically remain articulated. In order for delicate structures like these to have remained intact, only limited disturbances of the sediment could have occurred after burial. Thus, rock slabs fromtheBrechin Lagerstätte preservingmultiple specimens, whether on hardground surfaces or in high-density concentrations on non-hardground surfaces, can be taken to represent ecological snapshots with little to no time averaging.


Faunal constituents.—In addition to more than 20 crinoid genera, the Brechin Lagerstätte also preserves a diverse echinoderm fauna representing at least eight other major echinoderm groups, including asteroids, ophiuroids, edrioast- eroids, cystoids, cyclocystoids, homalozoans, edrioblastoids, and paracrinoids. The cystoid Pleurocystites squamosus Billings, 1874 is particularly abundant, often occurring in dense associations on bedding planes in the upper Bobcaygeon Formation. Although the non-crinoid echinoderms have not been critically evaluated from a taxonomic perspective, preliminary investigation indicates at least 19 non-crinoid genera occur in the Brechin Lagerstätte. Previous work on the hardgrounds and paleoecology of the Bobcaygeon and Verulam formations has paid particular attention to hardground-encrusting echinoderms such as edrioasteroids and paracrinoids (e.g., Brett and Liddell, 1978; Sumrall and Gahn, 2006).


Materials and methods


Localities and specimen preparation.—Although echinoderm fossils are known from several horizons in the Bobcaygeon and Verulam formations, the majority of the crinoid material described here was collected near the Bobcaygeon–Verulam contact in the Carden Quarry (44°34'335''N, 79°06'095''W), located 6 km east of Brechin, and the LaFarge Quarry


(44°31'559''N, 79°09'478''W), located 2 km southeast of the town of Brechin. In both of these quarries, specimens were collected from blast piles sourced from stratigraphic intervals containing approximately 15mof upper Bobcaygeon and 5mof lower Verulam, referred to hereafter as the “Bobcaygeon- Verulam contact zone.” Material is predominately from the collection of J.M. Koniecki. Additional material examined is from the James Dick Quarry (44°29'937''N, 79°09'616''W, collection of K. Brett), which is lower Verulam, and the classic Kirkfield Quarry (44°35'6.32''N, 78°58'8.16''W), which is middle–lower Bobcaygeon. The classic Kirkfield Quarry locality is now flooded and known as Kirkfield Lake. Specimens of Cleiocrinus lepidotus n. sp. from the


Cincinnati Museum Center Invertebrate Paleontology Collec- tions were prepared and/or reconstructed from disarticulated material by S.R. Cole; Archaeocrinus maraensis n. sp. UMMP 74688 was prepared by K. Brett; all other specimens were prepared by J. Koniecki. Unless otherwise noted, specimens were photographed after coating with ammonium chloride.


Phylogenetic analysis.—Phylogenetic analysis can play a useful role in alpha taxonomy as a quantitative method for identifying closely related taxa, thereby allowing new taxa to be classified and diagnosed in evolutionarily meaningful ways. This approach complements traditional taxonomy by allowing quantitatively generated hypotheses of evolutionary history to be combined with assessment of homologous morphologic features. Here, a phylogenetic analysis was conducted to examine relationships among dicyclic camerates from the Brechin Lagerstätte. Three of the four genera identified from the Brechin Lagerstätte (Cleiocrinus, Archaeocrinus, and Reteocrinus) were included in a recent phylogenetic analysis that inferred relationships among all Ordovician camerate crinoids (Cole, 2017). As a result, the primary focus of the analysis conducted here was to examine the evolutionary relationships of Priscillacrinus elegans n. gen. n. sp., described herein. Priscillacrinus n. gen. was coded for the same 112 discrete morphological characters described by Cole (2017). Using the phylogeny of Ordovician camerate genera recovered by Cole (2017) as a constraint, the placement of Priscillacrinus n. gen. within the tree was analyzed in PAUP* using a heuristic parsimony search with tree bisection reconnection and 1000 random addition sequences (Swofford, 2003). The phylogenetic analysis recovered a single most-


parsimonious tree (Fig. 2). The placement of Priscillacrinus n. gen. relative to Cleiocrinus, Archaeocrinus, and Reteocrinus reveals that the assemblage of dicyclic taxa in the Brechin Lagerstätte has high phylogenetic diversity, meaning that diversity is distributed across the tree rather than being restricted to a particular clade of closely related taxa. The recovered tree identifies Cotylacrinna, which is from the Sandbian of Iowa, as the genus most closely related to Priscillacrinus n. gen. These two genera form a clade with Goyacrinus, Anthracocrinus, and Rheocrinus, all of which are assigned to the family Anthraco- crinidae. Although Cotylacrinna is currently assigned to Rhodocrinitidae rather than Anthracocrinidae, it has been advocated that this genus be reassigned to Anthracocrinidae because it shares the features that are diagnostic of the family (Cole, 2017). As a result, the position of Priscillacrinus n. gen.


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