Paleocommunity composition, relative abundance, and new camerate crinoids from the Brechin Lagerstätte (Upper Ordovician)

Abstract The Brechin Lagerstätte of southern Ontario contains an exceptionally diverse and well-preserved Late Ordovician (Katian) crinoid fauna. We describe four genera and eight species of camerate crinoids from the Brechin Lagerstätte, including six new species. Consequently, the total diversity of the fauna now stands at 27 genera and 39 nominal species, thereby making it the most taxonomically diverse Ordovician crinoid fauna known. Taxa described include the diplobathrid Pararchaeocrinus kiddi new species and the monobathrids Glyptocrinus ramulosus Billings, 1856, Periglyptocrinus priscus (Billings, 1857a), Periglyptocrinus astricus new species, Periglyptocrinus kevinbretti new species, Periglyptocrinus mcdonaldi new species, Periglyptocrinus silvosus new species, and Abludoglyptocrinus steinheimerae new species. We summarize the taxonomic composition, diversity, and abundance distribution of all known crinoids from the Brechin Lagerstätte to better characterize the paleoecological structure and complexity of the community. We establish that the fauna is dominated by the subclass Pentacrinoidea, both in terms of abundance and species richness. In addition, we analyze species-level abundance data using Relative Abundance Distribution (RAD) models to evaluate the ecological complexity of the paleocommunity. We found that community structure of the Brechin Lagerstätte is best explained by an ecologically ‘complex’ RAD model, which suggests that species partitioned niches along multiple resource axes and/or the presence of multiple ecological ways of life. These results indicate that the Brechin Lagerstätte is significant not only for being the most taxonomically diverse Katian crinoid assemblage, but also for being an early ecologically complex fauna that developed in the wake of the Great Ordovician Biodiversification Event. UUID: http://zoobank.org/f86582ed-5db6-469E-befe-34b801f9a113


Introduction
The Upper Ordovician is one of the most significant periods in the evolutionary history of crinoids. Following their first appearance in the fossil record during the Early Ordovician, crinoids underwent a major taxonomic radiation during the Middle to Late Ordovician, with most major clades reaching peak diversity during the Sandbian-Katian (Wright and Toom, 2017;Cole, 2018). This increase in taxonomic diversity corresponded with the Great Ordovician Biodiversification Event (GOBE; Webby et al., 2004) and resulted in the formation of some of the first crinoid communities that were taxonomically, morphologically, and ecologically diverse (Foote, 1994;Peters and Ausich, 2008;Deline et al., 2012;Cole et al., 2019). As a result, better characterizing diversity, community structure, and ecology of Upper Ordovician faunas is an important step in understanding the early evolutionary history of crinoids and the development of ecologically complex communities during the GOBE.
The Upper Ordovician (Sandbian-Katian) rocks of southern Ontario, particularly the Bobcaygeon and Verulam formations in the Lake Simcoe region, contain a diverse assemblage of fossil crinoids. Although this fauna has been recognized for nearly 150 years (e.g., Billings, 1858Billings, , 1859Springer, 1911), the only taxonomic evaluation of the fauna until recently was Springer's (1911) monograph on the 'Kirkfield' fauna. More recently, the extensive collection of crinoid material from the Bobcaygeon and Verulam formations near Brechin, Ontario produced a substantial new collection of exceptionally preserved crinoids. To better understand the taxonomic diversity and paleoecology of this Upper Ordovician crinoid community, we undertook a comprehensive taxonomic re-evaluation of the crinoids from the Bobcaygeon and Verulam formations, which has been documented in a series of recent papers Cole et al., 2018;Wright et al., 2019). This exceptionally preserved fauna has been identified as a Konservat-Lagerstätte and has been subsequently referred to as the Brechin Lagerstätte, in reference to the nearby town of Brechin, Ontario .
We present here the fourth and final systematic contribution in the series on crinoids from the Brechin Lagerstätte. The three preceding publications focused on taxonomy of diplobathrid camerates , disparids and hybocrinids , and eucladids and flexibles . We evaluate the remaining camerate crinoids known from the fauna, including all monobathrids and a new diplobathrid camerate. Taxa described here bring the total diversity of the fauna to 27 genera and 39 species. Of these, 3 genera and 15 species are new. In addition, to better understand the structure and complexity of the Brechin Lagerstätte, we summarize the taxonomic composition of the fauna as a whole and fit model-based rank abundance distributions (RADs) to species abundance data. Because the abundance of taxa within a community is an important ecological parameter, RADs can be used to investigate a suite of processes that control community structure, e.g., resource partitioning, dimensionality of resource axes, and the number of ecological guilds. Previous work on the Brechin Lagerstätte used ecomorphological traits to evaluate the phylogenetic structure of niche partitioning and community assembly within the fauna . The inclusion of abundance data and the application of RAD-based modeling here provides quantitative insight into an additional aspect of the Brechin Lagerstätte as a paleocommunity: its ecological complexity. These complementary approaches provide a more synthetic view of the Brechin Lagerstätte's paleoecology and refine our understanding of Late Ordovician ecosystems.

Geologic setting
Crinoids and other invertebrate fossils from the Brechin Lagerstätte are preserved in multiple horizons of Upper Ordovician rocks in the vicinity of Brechin, Ontario. Stratigraphic division and nomenclature for this region have been in flux for many years, and as a result, crinoids from the same or equivalent strata have been associated with multiple formation names, including the Hull, Kirkfield, Cobourg, Bobcaygeon, and Verulam formations (Liberty, 1969;Uyeno, 1974;Armstrong, 2000; see Swisher et al., 2015). Although the Bobcaygeon and Verulam formations have been the favored stratigraphic divisions in recent years (Armstrong, 2000), work by  suggested subdividing the Bobcaygeon into the Kirkfield and Coboconk formations and elevating the Bobcaygeon to a subcategory within the Simcoe Group. To maintain consistency with our previous work on the Brechin Lagerstätte, we continue to follow the stratigraphic nomenclature of Armstrong (2000) that uses the Bobcaygeon and Verulam formations. However, we note that stratigraphic horizons referred here as belonging to the Bobcaygeon Formation are equivalent to the Kirkfield Formation of . For more detailed discussions of stratigraphic divisions and nomenclature of Upper Ordovician strata of southern Ontario, see Armstrong (2000), Cole et al. (2018), and .
The Bobcaygeon Formation and the overlying Verulam Formation are each made up of bioclastic wackestones, grainstones, and packstones with interbedded calcareous shales and siltstones. The rocks are interpreted to have been deposited in a proximal carbonate shelf environment that ranged in depth and proximity from shoal to shallow shelf in the Bobcaygeon and deep shelf to shoal/shallow shelf in the Verulam (Armstrong, 2000). The Verulam contains more shale than the underlying Bobcaygeon (Liberty, 1969). The Bobcaygeon and Verulam formations are part of the middle Simcoe Group, which is equivalent to the Trenton and Ottawa groups (Armstrong, 2000). Each formation is considered Late Ordovician (late Sandbian-Katian) in age (Sproat et al., 2015). Because the fossiliferous horizons of the Bobcaygeon are largely restricted to the uppermost portions of the formation (Liberty, 1969), specimens described here are all Katian in age.
The Brechin Lagerstätte has yielded a spectacular diversity of exceptionally preserved crinoid echinoderms with arms, stems, and holdfasts intact . Specimens often occur in dense accumulations on hardground surfaces and on nonhardground bedding planes. In particular, hardground surfaces from the Bobcaygeon and Verulam formations have been investigated in detail with regard to both formation and sedimentology  and the paleoautecology of taxa occurring on hardgrounds (Brett and Liddell, 1978;Brett and Brookfield, 1984;Brett and Taylor, 1999). Many of these hardground assemblages include completely intact crinoid specimens that can be directly cemented to the hardgrounds themselves. As a result, these horizons represent in situ species assemblages that can be considered 'ecological snapshots' (sensu Ausich, 2016;Meyer and Ausich, 2019) of once-living communities . Crinoid assemblages from nonhardground horizons in the Brechin Lagerstätte are authochthonous to parauthochthonous, and their taphonomic grade indicates minimal transport and time averaging (Brett et al., 1997;Cole et al., 2018). Thus, assemblages within these horizons should reflect the original composition and abundance of the community with high fidelity (Ausich, 2016).

Paleocommunity analysis: diversity and relative abundance of crinoids from the Brechin Lagerstätte
The ecological literature is rich with theories concerning how ecosystem complexity affects the diversity, abundance, and distribution of species within communities. In particular, the distribution of species abundance by rank order within a community is shaped by ecological processes and therefore has implications regarding patterns of resource partitioning, dimensionality of resource axes, and overall number of ecological types (i.e., guilds) within a community (Gray, 1987;Magurran, 2004;McGill et al., 2007;Baldridge et al., 2016). Because taphonomic studies indicate that fossil assemblages retain their biological rank order with strong fidelity (Kidwell, 2001;Meyer and Ausich, 2019), models of taxon relative abundance distributions (RADs) can be used to investigate patterns of community structure and ecological dynamics in 'deep time' (Wagner et al., 2006;Alroy, 2015;Darroch et al., 2018). Consistent with its use in paleoecological literature (e.g., Ausich 1980;Bennington and Bambach, 1996;Holterhoff, 1997a;Patzkowsky and Holland, 2003;Wagner et al., 2006;Darroch et al., 2018;Perera and Stigall, 2018), we use 'paleocommunity' to refer to the recurrence of fossil species within local assemblages that span a relatively brief interval of geological time.
We used likelihood-based implementations of RAD models to test whether crinoids in the Late Ordovician Brechin Lagerstätte represent an ecologically 'simple' or 'complex' paleocommunity (Wagner et al., 2006;Darroch et al., 2018). 'Simple' RADs assume that species utilize and compete for similar resources. These models effectively treat niche space Journal of Paleontology 94(6):1103-1123 as a single resource axis partitioned according to models of niche preemption (geometric series) or random fractionation (i.e., broken stick). In contrast, 'complex' RAD models, e.g., lognormal or Zipf distributions, invoke additional resource axes. Consequently, complex RAD models imply disparity in niche-space utilization and the presence of multiple ecological types (i.e., guilds) within the paleocommunity (Gray, 1987;Magurran, 2004;Darroch et al., 2018).
We fit two simple (broken stick and geometric series) and two complex (lognormal and Zipf distributions) RAD models to a dataset comprised of 756 specimens spanning all 39 nominal species (27 genera) of crinoids in the Brechin fauna. Taxonomic abundance data were collected from multiple years of field-based observations by J. Koniecki and include specimens now reposited in UMMP (see Suppl. Data 2). Only specimens that could be confidently identified to the species level were included. To test whether results were sensitive to differences in taxonomic scales, we conducted analyses at the species and genus levels. Model fitting was performed using the R package Vegan (Oksanen et al., 2010). The Bayesian Information Criterion (BIC) was used to assess relative fit among RAD models. We chose to use BIC over Akaike's Information Criteria because BIC carries a larger penalty term for adding parameters (i.e., equal to the natural logarithm of the number of parameters; see Burnham and Anderson, 2002) and thus minimizes potential biases toward supporting complex RAD models.
The rank-order abundance distribution for crinoids from the Brechin Lagerstätte is presented in Figure 1.1. The most numerically abundant subclade is the species-poor Cupulocrinus-Flexibilia lineage ( Fig. 1.2, 1.3), primarily due to the abundance of Cupulocrinus humilis Springer, 1911 (Suppl. Fig. 1). However, in terms of both species richness and abundance, the overall taxonomic composition is dominated by members of the subclass Pentacrinoidea (25 species, 626 specimens; Suppl. Data 2) regardless of whether members of the Cupulocrinus-Flexibilia subclade are considered or not considered. In contrast, subclass Camerata has lower species richness and abundance (15 species, 130 specimens; Suppl. Data 2). Bayesian Information Criterion (BIC) scores for RAD models indicate that crinoid abundances best fit Zipf distributions (Table 1), with ΔBIC scores providing strong evidence against all other RAD models according to Kass and Raftery's (1995) statistical guidelines. Moreover, the preference for Zipf RAD models are independent of the taxonomic scale analyzed ( Table 1).
Assuming that divergence of crinoids from other echinoderms occurred by at least the Early Ordovician, the ecological diversity of crinoids from the Brechin Lagerstätte represents the cumulative outcome of < ∼ 10% of the clade's total evolutionary history. In contrast with extant crinoids and their extinct precursors, Ordovician crinoids had not yet evolved several complex morphological and/or behavioral adaptations that contribute to niche disparity today, e.g., muscular articulations or increased motility/swimming. For example, consider the dramatic disparity in ecological life modes exhibited by species of modern isocrinids, shallow-water 'feather stars,' and cyrtocrinids (e.g., Holopus). From these considerations, one might predict that early Paleozoic crinoid communities would be dominated by one (or few) ecological types and characterized by relatively simple patterns of niche preemption. Such communities would be expected to fit ecologically "simple" RAD models. Instead, our results indicate that the Brechin fauna is best characterized by an ecologically 'complex' RAD model, which suggests that crinoids partitioned niches along multiple resource axes. Standard interpretations of ecologically complex RAD models imply a multidimensional niche space partitioned into two or more groups, each with a different ecological strategy or guild. Other possible interpretations suggest that increased niche space arises from biotic interactions among species (Darroch et al., 2018). We note that these interpretations are not mutually exclusive. In the case of the Brechin crinoid fauna, there is possible evidence for each explanation. Cole et al. (2019) documented trait-based patterns of ecological disparity among Brechin crinoids. Niche differences were determined to have been influenced by several ecomorphological traits, including filtration fan density, fan shape, body size, and stem length . Of these traits, differences in filtration fan characters were found to be the most important dimensions for defining niche space; these results are broadly consistent with those from previous studies of crinoid communities (Ausich, 1980;Meyer and Ausich, 1983;Brower, 2007). Further, traits such as filtration fan density and body size exhibited strong phylogenetic signal, indicating that subclades could also be characterized (on average) by differences in feeding ecology and life mode (Kammer, 1985;Holterhoff, 1997b). Experiments on living species indicate that crinoids with different fan densities and/or stalk lengths have different dietary preferences and often consume different resources (Kitazawa et al., 2007;Kitazawa and Oji, 2010). In the Brechin fauna, Cole et al. (2019) concluded that ecological differences were most pronounced at high taxonomic scales, separating the pinnulate Eucamerata from the nonpinnulate Inadunata. It is possible that these major ecomorphological differences have been similarly related to differences in resource use and/or consumption between these two lineages. Considering the degree of ecomorphologic variation among these clades reported by Cole et al. (2019), our finding that the Brechin fauna fits a 'complex' RAD supports and complements this previous study.
Finally, the Brechin Lagerstätte records a paleocommunity immediately following the culmination of the GOBE, which introduced a significant increase in ecological organization across Earth's global biota (Muscente et al., 2018). Given that biotic interactions have played an important role in crinoid evolution (e.g., Meyer and Ausich, 1983;Baumiller and Gahn, 2002;Gorzelak et al., 2012), the ecological complexity of the Brechin fauna could be related to changes in Ordovician ecosystems more broadly. Similarly, the diversity and abundance of crinoids within communities has been linked with 'ecosystem engineering' mechanisms (sensu Erwin, 2008), such as positive taphonomic feedback (Kidwell and Jablonski, 1983;Ausich, 1997), which notably increased following the GOBE (Pruss et al., 2010).
Based on our series of comprehensive taxonomic re-evaluations Cole et al., 2018;Wright et al., 2019), including those presented here, the Brechin Lagerstätte is the most taxonomically diverse Katian crinoid fauna in the world. To the best of our knowledge, the Brechin Lagerstätte contains more nominal crinoid species and genera than the wellknown Middle Ordovician Bromide Formation of Oklahoma (Sprinkle, 1982;see Webster and Webster, 2014). Although the presence of fragmentary and undescribed material indicates that the Bromide Formation might have higher species diversity (Sprinkle, 1982), the Brechin fauna is significant as one of the oldest, ecologically complex, and taxonomically diverse crinoid paleocommunities in the fossil record.

Materials and methods
Specimen collection and preparation.-The crinoid material described here was collected in the Lake Simcoe region of Ontario from the Carden Quarry (44°34'03.35''N, 79°0 6'09.5'W), the LaFarge Quarry (44°31'55.9'N, 79°0 9'04.78'W), and the James Dick Quarry (44°29'56.2'N, 79°0 9'37.0'W) (see Cole et al. [2018] for additional locality details). All localities are within ∼ 6 km of the town of Brechin, Ontario. Material from the Carden and LaFarge quarries was primarily collected from blast piles. As a result, stratigraphic resolution was coarse for many specimens but can be constrained to an interval spanning ∼ 15 m of the upper (2) histogram depicting the relative abundance of specimens belonging to species within the crinoid subclasses Pentacrinoidea and Camerata; (3) phylogeny of major crinoid subclasses plotted alongside a histogram showing the relative abundance of specimens belonging to species within each subclade.

Journal of Paleontology 94(6):1103-1123
Bobcaygeon Formation and 5 m of the lower Verulam Formation, hereafter referred to as the Bobcaygeon-Verulam boundary interval ). More precise stratigraphic data are given when possible. Localities and collection horizons are summarized for all specimens in the Supplemental Materials (Suppl. Data 1).
The majority of the specimens described here are from the collection of J. M. Koniecki and are now reposited at the University of Michigan Museum of Paleontology (UMMP). Exceptions are UMMP 74688.2, prepared and donated by K. Brett; UMMP 74900, prepared by K. Kidd and M. Thornley and donated by K. Kidd; and UMMP 74863-74863.3, collected by S. Hyne and prepared by J. M. Koniecki. Except where otherwise noted, specimens were coated with ammonium chloride sublimate before photographing.
The superordinal and ordinal classification of Camerata follows Cole (2017) and . Family-level classification follows Moore and Teichert (1978). General morphologic terminology follows Ubaghs (1978a) and the shorthand notation used to describe heteromorphic columns follows Webster (1974).
The plating in the interrays is given as the number of plates in each range from the proximalmost plate to the last range before the tegmen. In the posterior interray, the primanal is indicated by "P" and the first interradial in regular interrays is indicated by the numeral "1". A question mark in the interray series indicates that more distal plating is unknown.
Repositories and institutional abbreviations.-All new specimens described here are reposited in the University of Michigan Museum of Paleontology (UMMP). Other material considered is from the collections of the Geological Survey of Canada (GSC). Diagnosis.-A rhodocrinitid crinoid with a low, globular aboral cup; regular interrays wide, proximal plating 1-3; posterior plating 1-3 proximally, with an anitaxis originating from either the center of the interray or the C radial; arms 10, entirely uniserial or transitioning distally to biserial, unbranched or branching up to four times (emended from Kolata, 1982 Diagnosis.-Pararchaeocrinus with granulose ornamentation; median ray ridges and ridges on basals and radials composed of multiple, parallel ridges; wide anitaxis originating from the center of the posterior interray; arms unbranched, predominantly uniserial.

Systematic paleontology
Occurrence.-The holotype specimen of Pararchaeocrinus kiddi n. sp. is from the upper Bobcaygeon Formation, James Dick Quarry. All other known specimens of Pararchaeocrinus kiddi n. sp. are from the Bobcaygeon-Verulam boundary interval, Carden Quarry (Ontario, Canada).
Description.-Calyx low to medium globose, with concave base; plate sutures flush with plate surface. Basals and radials ornamented with ridges composed of multiple, parallel, raised striations; ridges on basals forming a pentagonal structure around base of calyx, extending onto radials in a star pattern. Median ray ridges wide and prominent, connected proximally to radial plate ridges, similarly composed of multiple, parallel ridges. Granulose ornamentation on most or all calyx plates.
Infrabasals not observed, presumably five, entirely confined to basal concavity. Basal circlet forming the distal margin of the basal concavity. Basal plates five, wider than high, hexagonal, approximately equal in size to radials.
Radial circlet interrupted in all rays by contact of basals with primanal and first interradial plates. Radial plates five, pentagonal or hexagonal, slightly higher than wide.
Regular interrays wide, in contact with tegmen, not depressed, interrupting the radial circlet in all interrays. First interradial plate octagonal (where observed), wider than high, largest plate in calyx; second range with three plates, proximal plating 1-3, followed by two or more higher rows of four or more plates each (Fig. 2.1).
Posterior interray wider than regular interrays and with additional plates, in contact with tegmen; proximal plating 1-3 followed by at least four rows of higher plates with four or more First primibrachial fixed, hexagonal, wider than high; second primibrachial axillary, pentagonal, wider than high. Secundibrachials fixed into calyx through approximately the third secundibrachial; second secundibrachial giving rise to a fixed pinnule. Fixed intrabrachials between secundibrachials of each half-ray, comprised of at least two rows of two plates each.
Stem circular, heteromorphic; columnals thin; nodals and internodals with slightly undulatory margins. Proximal column with two orders of internodals, N2221222 where fully differentiated; priminternodals approximately half the thickness of nodals, secundinternodals approximately one-third the thickness of priminternodals. Lumen round, large, ∼ 60% of total stem diameter.
Etymology.-The specific name is in honor of Kevin Kidd, who collected, prepared, and donated the holotype specimen for study.
Remarks.-Pararchaeocrinus kiddi n. sp. is most closely aligned with Pararchaeocrinus on the basis of its distinctive 1-3 plating in the proximal portion of the regular interrays, globose cup, 10 arm openings, and predominantly uniserial (4) UMMP 74820, holotype, CD-interray view; (5) Abludoglyptocrinus steinheimerae n. sp., UMMP 74817, holotype. P = primanal; fill: black = radials; gray = matrix/plating unknown; ruled = plate edges/undersides; stippled = interray plates; lines: dashed black = inferred plate boundaries; dashed gray = ray ridges/plate ornamentation; jagged = broken plate margins; solid black = plate boundaries. free arms (Figs. 2.1, 3.1). Of the three species of Pararchaeocrinus previously known, only Pararchaeocrinus decoratus preserves the posterior interray. The posterior interradius in Pararchaeocrinus decoratus consists of an anitaxis arising from the C radial that is ornamented by an anitaxial ridge. Although the posterior interray of Pararchaeocrinus kiddi n. sp. also has an anitaxial ridge, it appears to originate from the CD basal at the center of the ray rather than from the C-ray radial (Figs. 2.3, 3.2). Despite this difference, the new species is here assigned to Pararchaeocrinus based on the characters listed above, particularly the 1-3 plating in the regular interrays, which is uncommon in Ordovician diplobathrids (Kolata, 1982).
Pararchaeocrinus kiddi n. sp. is most like Pararchaeocrinus decoratus. However, the two species differ in several notable features. Pararchaeocrinus kiddi n. sp. has unbranched arms, an anitaxis that originates from the center of the posterior interray, granulose plate ornamentation, and median ray ridges consisting of multiple, parallel ridges, whereas Pararchaeocrinus decoratus has arms that branch at least three times, an anitaxis that originates from the C radial, stellate ornamentation, and median ray ridges made up of single ridges.
Pararchaeocrinus kiddi n. sp. is here described from one adult and four subadult specimens. Although the smaller, subadult specimens (UMMP 74863-74863.3; Fig. 2.2, 2.3) can be confidently assigned to Pararchaeocrinus kiddi n. sp. based on similarities in the structure of arms, column, and overall calyx plating, they do not display any of the ornamentation observed in the adult specimen (UMMP 74900) except for median ray ridges (Fig. 2.1-2.3). This suggests that the granulose ornamentation and striations on the median rays are features that developed later in ontogeny. Cole et al. (2019) included Pararchaeocrinus kiddi n. sp. in an analysis of Brechin crinoid community paleoecology using the placeholder name of Pararchaeocrinus sp. A. Pararchaeocrinus kiddi n. sp. had the highest filtration fan density (90.23 terminal feeding appendages per cm 2 ) within the fauna .
Diagnosis.-A glyptocrinid with 10 uniserial arms free above secundibrachials 3-5; median anal and ray ridges present; variable ornamentation consisting of small pustules or fine ridges; some species possessing smooth plates (after Kolata, 1982).
First primibrachial hexagonal, equant; second primibrachial axillary, heptagonal. Arms free above secundibrachials 3-5; fourth secundibrachial irregularly giving rise to a fixed pinnule adaxially. Fixed intrabrachials between secundibrachials of each half-ray in four or more rows of one or two plates each; intrabrachial areas narrowly in contact with tegmen.
Etymology.-The specific name is in honor of Margaret Steinheimer, a lifelong friend of J. Koniecki who encouraged him throughout his fossil collecting years. She was also a teacher, mother, and friend to many.
Remarks.-Abludoglyptocrinus steinheimerae n. sp. superficially resembles Periglyptocrinus kevinbretti new species, which also occurs in the Brechin Lagerstätte (e.g., Figs. 2.4, 5.1). However, the two taxa are readily differentiated in construction of the arms; A. steinheimerae n. sp. has uniserial arms and Periglyptocrinus kevinbretti has biserial arms. This is also one of the major features that identifies A. steinheimerae n. sp. as belonging to the genus Abludoglyptocrinus rather than Periglyptocrinus (Kolata, 1982;Ausich, 1985).
Journal of Paleontology 94(6):1103-1123 Abludoglyptocrinus steinheimerae n. sp. is most like other species of Abludoglyptocrinus, particularly A. pustulosus from the Upper Ordovician Forreston Member of the Grand Detour Formation, Illinois and A. laticostatus from the Upper Ordovician (Sandbian) Pooleville Member of the Bromide Formation, Oklahoma. All three species have conspicuous ray ridges, stellate ornamentation on the basals and radials, and granular ornamentation on the calyx plates. They differ most noticeably in that A. steinheimerae n. sp. has free arms that branch twice and proximal interray plating in a 1-2-2-2 pattern, whereas A. pustulosus has unbranched free arms and proximal interray plating in a 1-2-3-4 pattern, and A. laticostatus has unbranched free arms and proximal interray plating in a 1-2-2-3 pattern. Diagnosis.-Glyptocrinus with medium conical calyx; plates flat and unornamented; median ray ridges broad; base of calyx surrounded by a prominent dropped flange; interrays broad and flat, proximal plating 1-2 with 5-7 higher rows of two or three plates each; intrabrachials between half-rays numerous; 20 free arm openings; free arms branching once; stem round.
Occurrence. Description.-Calyx medium bowl, wider than high; plates unornamented except for basals; median ray ridges low and broad on radials and primibrachials, becoming more distinct and rounded on fixed secundibrachials; plate sutures flush with plate surface; base of calyx upright, surrounded by a circular ridge. Basal circlet upright, slightly recessed beneath radial circlet. Basal plates five, small, wider than high, pentagonal, ornamented with a flared ridge at the base encircling the stem with narrow ridges angled toward the adjoining radial plates.
Radial circlet uninterrupted; radial plates heptagonal, approximately as wide as high, largest plates in calyx.
Regular interrays in contact with tegmen, not depressed, narrowing distally. First interradial plate hexagonal, wider than high, larger than basals, slightly smaller than radials. Second range with two plates; proximal plating 1-2-2 followed by 4-6 higher rows typically with two or three plates each (Fig. 4.1).
Posterior interray much wider, in contact with tegmen, narrowing slightly distally. Primanal hexagonal, wider than high, approximately equal in size to first interray plates. Proximal plating P-3-5-5-5-5, at least three higher rows of plates with five or more plates each; medial column of plates forming a distinct anitaxis ornamented with a low anitaxial ridge ( Fig. 2.6).
First primibrachial fixed, hexagonal, approximately as high as wide; second primibrachial axillary, heptagonal. Secundibrachials typically becoming free above fifth plate; second and fourth secundibrachials giving rise to fixed pinnules abaxially and adaxially, respectively; fixed pinnules marked by thin, sharp ray ridges. Fixed intrabrachials between secundibrachials of half-rays; intrabrachial plates large, proximal plating 1-1-2-2, commonly with additional higher rows of one or two plates each. Arm openings 20, grouped by half-rays. Free arms cuneate uniserial; brachials very thin, ∼ 6.5 times wider than high; arms branching once isotomously near the calyx, densely pinnulate; pinnules long and thin (Fig. 4.2).
Stem circular, holomeric, heteromorphic. Proximal stem with nudinodals and three orders of closely spaced, welldifferentiated internodals, N3231323 where fully differentiated; distance between nudinodals and internodals increasing in medial and distal stem. Tegmen, anal opening, and other details of column unknown.   Remarks.-A formalized diagnosis for Glyptocrinus ramulosus has not been previously published to our knowledge. The diagnosis presented here combines our own observations of new material with descriptions given by previous workers, especially Billings (1857a and Wachsmuth and Springer (1897). Notably, we figure and describe in detail the posterior interray of G. ramulosus (Fig. 2.6).
Glyptocrinus ramulosus is one of the largest species recovered from the Brechin Lagerstätte. The maximum size of the crown reaches ∼ 11 cm (UMMP 74815; Fig. 4.1, 4.2). Smaller specimens (UMMP 74814-74814.2; Fig. 2.7, 2.8) are likely juveniles. The height to width ratios of the proximal brachials in these specimens are much higher than those for the adult specimens, which commonly indicates earlier stages of ontogenetic development (Brower, 1974;Cole et al., 2017 Diagnosis.-Glyptocrinidae with large, upright basals almost entirely visible in side view; 10 or 20 free arm openings; arms biserial, branched or unbranched; fixed pinnules; stellate ornamentation on at least proximal calyx plates (emended from Ubaghs, 1978b).
Remarks. -Springer (1911) referred all specimens of Periglyptocrinus from Kirkfield to Periglyptocrinus priscus but noted that many of the specimens had much stronger stellate ornamentation on the calyx plates than had been previously recognized. We assign specimens of Periglyptocrinus from the Brechin Lagerstätte to five species, including Periglyptocrinus priscus and four new species. Because three species of Periglyptocrinus were previously recognized, the description of these new species more than doubles the known species richness of the genus. Although the four new species are similar in many aspects of calyx plating, they differ with regard to calyx shape, plate ornamentation, contact of the interrays with the tegmen, stem morphology, and arm branching. Major differences between species of Periglyptocrinus are summarized in Table 2 Description.-Calyx high cone, higher than wide; base of calyx upright, surrounded by a low, narrow ridge; plate sutures flush with plate surface. Ornamentation consisting of prominent, broad stellate ridges on basals, radials, and first interray plates that connect to form a distinctive wagon-wheel pattern ( Fig. 4.4, 4.6); upper interray plates with smooth, rounded concavities. Median ray ridges prominent, narrow, rounded; slightly constricted at plate sutures. Basal circlet upright; basal plates five, pentagonal, slightly wider than high.
Radial circlet uninterrupted; radial plates heptagonal, as wide as high, largest plates in calyx.
Posterior interray slightly wider than regular interrays, tapering distally; in contact with the tegmen very narrowly or not at all. Primanal heptagonal, approximately as wide as high, slightly larger than first interray plates. Posterior plating consisting of primanal followed by anitaxis of six or more plates with a single column of small plates on each side of the anitaxis; roughly P-3-3-3-3-3-3 but with some additional plates lateral to anitaxis. Primanal ornamented with heavy stellate ridges; anitaxis originating from distal ridge, other ridges extending proximally to adjacent radials and laterally to first primibrachials.
First primibrachial fixed, hexagonal, approximately as wide as high; second primibrachial axillary, heptagonal. Proximal secundibrachials fixed, second giving rise to fixed pinnule abaxially, fourth giving rise to fixed pinnule adaxially, fifth to seventh giving off pinnules on alternate sides; arms becoming free above seventh or eighth secundibrachial (Figs. 3.3, 4.6). Fixed intrabrachials between secundibrachials of half-rays, typically in 4-6 rows of one or two plates each; intrabrachials with smooth central concavities; a few small plates irregularly positioned between secundibrachials and first fixed pinnules.
Arm openings 10, ungrouped. Arms strongly cuneate biserial immediately where they become free, transitioning to wedge biserial just above the calyx. Arms unbranched, pinnulate; pinnules long and thin, densely arranged.
Etymology.-The specific name is from the Latin, astricus, meaning starry, in reference to the prominent stellate ornamentation on the calyx plates.
Journal of Paleontology 94(6):1103-1123 basals, radials, first interray plates, and first primibrachials to form a distinctive wagon-wheel pattern; smooth, rounded concavities on distal interray plates; and a stem with construction N212. In contrast, Periglyptocrinus mcdonaldi n. sp. has a medium bowl-shaped calyx; broad stellate ridges on the distal basals, radials, proximal interray plates, and primibrachials with granulose ornamentation between ridges; a combination of irregular stellate ridges, granulose ornament, and irregular concavities on more distal interray and fixed brachial plates; and a stem with construction N2221222. Although differences in ornamentation are subtle, they are consistently expressed across many specimens and do not appear to be a function of ontogeny, with subadult specimens showing fully developed ornamentation consistent with one species or the other without any gradation between the two (Fig. 4.3; UMMP 74686.5-74686.7, 74686.10). See Table 2 for a summary of other characters that differ between species of Periglyptocrinus. Cole et al. (2019) included Periglyptocrinus astricus n. sp. in an analysis of Brechin crinoid community paleoecology using the placeholder name of Periglyptocrinus sp. C.
Occurrence.-The occurrences documented here are from the Upper Ordovician (early Katian) lower Verulam Formation, James Dick Quarry and from the Bobcaygeon-Verulam boundary interval, Carden Quarry (Ontario, Canada).
Description.-Calyx medium cone-to bowl-shaped, height and width approximately equal; base of calyx upright; plate sutures flush with plate surface. Median ray ridges prominent, narrow, maintaining width across plates. Ornamentation on basals, radials, first interray plates, and primanal consisting of stellate ridges with granulose ornamentation between ridges; other calyx plates with granulose ornamentation only ( Fig. 5.2, 5.3). Basal circlet upright; basal plates five, pentagonal, wider than high; ridge on proximal margins forming a circular ridge around the base of the calyx, with two additional ridges on each plate extending upward and connecting to ridges on adjacent radial plates.
Radial circlet uninterrupted. Radial plates heptagonal, slightly wider than high; largest plates in calyx. Each radial plate with seven ridges that converge in the center of the plate to form a stellate pattern.
Regular interrays in contact with tegmen, slightly depressed, tapering distally. First interradial plate hexagonal, wider than high, slightly larger than basals, much smaller than radials. Second range with two plates; proximal plating 1-2-3?-2-3-4 followed by at least two higher rows of four or more plates each (Fig. 6.5).
Posterior interray wider than regular interrays, apparently in contact with tegmen, tapering distally. Primanal heptagonal, approximately as wide as high, larger than first interray plates, ornamented with five ridges that converge in the center of the plate to form a stellate pattern. Proximal plating in the posterior interray P-3-3? followed by at least two higher rows of three or more plates; medial column of plates forming an anitaxis ornamented with an anitaxial ridge (Figs. 5.2,6.4).
Arm openings 10, ungrouped. Free arms predominantly cuneate biserial but becoming uniserial in places; branching poorly isotomously twice in most arms, but some arms unbranched or branching three times; pinnules long, relatively robust at the bases (Fig. 5.1).
Holdfast composed of many terminal rhizoids branching irregularly from lowermost portion of the stem (lower sixth in UMMP 74823); rhizoids mostly unbranched, protruding outward and downward, composed of uniformly thin segments, penetrated by axial canal (Fig. 5.6).
Tegmen and anal opening unknown.
Etymology.-The specific name is given in honor of Kevin Brett, who collected, prepared, and donated the holotype specimen.
Remarks.-Periglyptocrinus kevinbretti n. sp. is most similar to the other species of Periglyptocrinus from the Brechin Lagerstätte. However, it differs from all other species in the fauna in that the arms branch isotomously two or three times ( Fig. 5.1). See Table 2    Radial circlet uninterrupted; radial plates heptagonal, slightly wider than high; largest plates in calyx.
Regular interrays narrow, not in contact with tegmen, not depressed, tapering distally. First interradial plate hexagonal, approximately as wide as high, slightly smaller than basals, much smaller than radials. Second range with two plates; proximal plating 1-2, with two to five higher rows of plates with two plates each, less commonly with three plates in some rows (Figs. 6.3,7.2).
Posterior interray wider, not in contact with tegmen, tapering distally. Primanal heptagonal, approximately as wide as high, slightly larger than first interray plates. Proximal plating P-3-3-3-3, with two or more higher rows of plates with one to three plates each; medial column of plates forming a distinctive anitaxis ornamented with a prominent anitaxial ridge (Figs. 6.3, 7.2, 7.3).
Tegmen and anal opening unknown.
Etymology.-The specific name is given in honor of Terry McDonald, a long time collector of the Brechin Lagerstätte, who collected some of the specimens described in this series of papers. Description.-Calyx high bowl, slightly higher than wide; plates thin and flat. Radials typically ornamented with low stellate ridges, the two proximal ridges extending from radials onto basals, first interray plates occasionally ornamented with stellate ridges, higher plates unornamented; plate sutures flush with plate surface; base of calyx surrounded by a thin but prominent circular ridge; median ray ridges low, narrow, constricted in the center of the plates, widening near the plate margins. Basal circlet upright; basal plates five, pentagonal, widening distally, approximately as wide as high, smaller than radial plates.
Radial circlet uninterrupted. Radial plates heptagonal, slightly wider than high, largest plates in calyx.
Regular interrays in contact with tegmen, not depressed, slightly narrowing distally. First interradial plate hexagonal, approximately as wide as high, slightly larger than basals, much smaller than radials. Second range with two plates; proximal plating 1-2-2-2, followed by three or four higher rows with two to four plates each (Figs. 6.1, 7.4).
Posterior interray wider than regular interrays, in contact with tegmen, tapering distally. Primanal heptagonal, higher than wide, slightly larger than first interray plates. Proximal plating P-3-3-3-3-?, medial column of plates forming a distinctive anitaxis. Primanal ornamented with an inverted Y from which an anitaxial ridge originates; the two proximal ridges extending to the adjacent radial plates.
Remarks.-Although Periglyptocrinus priscus is similar to the other Periglyptocrinus species in the Brechin Lagerstätte, it is the only species that possesses unbranched arms and interrays that are all in contact with the tegmen (Figs. 6.1, 7.4). Additional features that differentiate Periglyptocrinus priscus from other species of Periglyptocrinus are given in Table 2 Holotype.-UMMP 74826.
Occurrence.-Periglyptocrinus silvosus n. sp. is known from a single specimen collected from the Bobcaygeon-Verulam boundary interval, LaFarge Quarry (Ontario, Canada).
Description.-Calyx medium cone, approximately as high as wide; base of calyx upright, surrounded by a circular ridge; plate sutures flush with plate surface. Stellate ornamentation on basals and radials, narrow and low; no ornamentation on distal calyx plates. Median ray ridges narrow and low. Basal circlet upright; basal plates five, pentagonal, equant. Radial circlet uninterrupted; radial plates heptagonal, equant, largest plates in calyx.
First primibrachial fixed, hexagonal, higher than wide; second primibrachial axillary, heptagonal. Proximal secundibrachials fixed, free above second or third secundibrachials. Third secundibrachial typically giving rise to first pinnule that might or might not be fixed; fifth and all higher secundibrachials giving rise to free pinnules. Fixed intrabrachials present between secundibrachials of half-rays, typically a single plate.
Etymology.-The specific name is from the Latin, silvosus, meaning branched or branching, in reference to the branched arms of this species.
Journal of Paleontology 94(6):1103-1123 Remarks.-Periglyptocrinus silvosus n. sp. is most similar to other species of Periglyptocrinus from the Brechin fauna, particularly Periglyptocrinus kevinbretti n. sp., which is the only other species of Periglyptocrinus in the fauna with free arms that branch, although the arms of Periglyptocrinus kevinbretti n. sp. branch up to three times whereas those of Periglyptocrinus silvosus n. sp. branch only once (Figs. 5.1,7.4). Additional differences between Periglyptocrinus silvosus n. sp., Periglyptocrinus kevinbretti n. sp., and other species of Periglyptocrinus are summarized in Table 2. Cole et al. (2019) included Periglyptocrinus silvosus n. sp. in an analysis of Brechin crinoid community paleoecology using the placeholder name of Periglyptocrinus sp. D.