Quantitative Paleoecology of Marine Faunas In

OLD G

The Geological Society of America Special Paper 545 OPEN ACCESS

Quantitative paleoecology of marine faunas in the lower Hamilton Group (Middle Devonian, central New York): Significance for probing models of long-term community stability

Cathryn R. Newton* Willis B. Newman† James C. Brower† Department of Earth Sciences, Syracuse University, Syracuse, New York 13244-1070, USA

ABSTRACT

Beautifully fossiliferous strata in the Hamilton Group (Middle Devonian, central New York) constitute a rich “ecological archive” sufficient to probe and test founda- tional concepts in paleontology. The evident community stability of Hamilton faunas over 4–6 m.y.—including two proposed mechanisms for coordinated stasis—has ignited controversy. Resolving community structure and both taxonomic and ecological temporal persistence within the Hamilton Group thus becomes critical to testing whether these Hamilton communities are stable and whether they are ecologically “locked.” Toward this end, we conducted multivariate analyses (cluster and correspondence analysis) of marine faunas in 81 large samples (~300 specimens each) in shallowing-upward sequences of the Cardiff and Pecksport Members (Marcellus Subgroup, Oatka Creek Formation) of the Hamilton Group. Eight statistically and ecologically distinctive benthic communities characterize the vertical gradient, from depauperate, deeper-water dark shales below to species-rich shelf siltstones above. These communities correlate strongly with grain size, bioturbation intensity, bedding thickness, density of fossils, and faunal and ecological diversity. Species richness varies inversely with weight percent organic matter. We characterized taxonomic distributions using multivariate statistics; these statistical analyses were based on percentages of 50 taxa. In order of decreasing depth, the communities are: Cephalopod-Pterochaenia, Pterochaenia- Eumetabolotoechia, Eumetabolotoechia, Emanuella, Eumetabolotoechia-Ambocoelia, Arcuaminetes-Eumetabolotoechia, Arcuaminetes-Ambocoelia , and Mucrospirifer- Ambocoelia. The Cephalopod-Pterochaenia community represents a mixed benthic- pelagic fauna associated with the deepest and finest-grained facies. The Pterochaenia- Eumetabolotoechia, Eumetabolotoechia, and Emanuella communities have low to

*corresponding author: [email protected] †deceased

Newton, C.R., Newman, W.B., and Brower, J.C., 2020, Quantitative paleoecology of marine faunas in the lower Hamilton Group (Middle Devonian, central New York): Significance for probing models of long-term community stability, in Avary, K.L., Hasson, K.O., and Diecchio, R.J., eds., The Appalachian Geology of John M. Denni- son: Rocks, People, and a Few Good Restaurants along the Way: Geological Society of America Special Paper 545, p. 161–195, https://doi.org/10.1130/2020.2545(09). © 2020 The Authors. Gold Open Access: This chapter is published under the terms of the CC-BY license and is available open access on www.gsapubs.org.

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moderate species richness and are dominated by epifaunal, active suspension feeders, especially the small epibyssate bivalve Pterochaenia fragilis, and the pedunculate brachiopods Eumetabolotoechia multicostata and Emanuella subumbona. The Pterochaenia-Eumetabolotoechia community is an opportunistic fauna that developed when the substrate first became favorable for colonization by benthic organisms. To a lesser extent, this probably also holds true for the Eumetabolotoechia assemblage. Communities near the top of the shallowing-upward cycle—Eumetabolotoechia- Ambocoelia, Arcuaminetes-Eumetabolotoechia , Arcuaminetes-Ambocoelia, and Mucrospirifer-Ambocoelia—have higher taxonomic and ecological heterogeneity, with a more diverse array of trophic and locomotory groups than their counterparts in the finer-grained, and inferred deeper, facies. Cluster significance tests applied to all pairs of communities known from adequate numbers of samples demonstrated that the communities are statistically valid and distinctive. Multivariate means of all communities were significantly different; furthermore, most pairs of communities were drawn from populations that showed no overlap in terms of rectangular distributions. The community sequence and an ordination derived from the first two axes of the correspondence analysis provided relative depth curves. Our communities, with two exceptions, do not have clear counterparts among upper Hamilton Group faunas. The ecological locking model proposed to explain the stability of Hamilton faunas is not supported by our quantitative tests to date.

INTRODUCTION 1985; Brett et al., 1996; Schopf, 1996; Ivany et al., 2009; Brett, 2012). The marine communities in the Hamilton Group have Abundant and often exquisitely preserved marine faunas been claimed to be one of the fossil record’s best-documented in the well-exposed Middle Devonian Hamilton Group of New and most temporally persistent examples of coordinated stasis York have long attracted international attention as a valuable (Brett and Baird, 1995; Ivany et al., 2009; Nagel-Myers et al., “ecological archive” for testing new hypotheses in paleontol- 2009). Various scholars have analyzed taxonomic stasis during ogy. Studied intensively by paleontologists and stratigraphers for this 4–6 m.y. interval and explored the possibilities of ecological more than 150 yr, these rich and temporally persistent Hamilton stasis, which include both stable community structure and even, faunas have figured prominently in some of the largest evolution- in the view of some authors, stable rates of predation. ary and paleoenvironmental debates, both past and present. The Explanatory proposals for coordinated ecological stasis hypothesis of punctuated equilibria, the oft-debated speciation in the Hamilton Group interval have engendered controversy. model of Eldredge and Gould (1972), derived in part from Niles Scholarly discussion, intense and sometimes heated, has cen- Eldredge’s interpretations of morphological stasis in the Hamil- tered on possible mechanisms, principally “ecological locking” ton trilobite Phacops rana1 and related species in his Columbia or “environmental tracking” (Morris et al., 1995; Ivany, 1996). University doctoral dissertation. Superbly preserved Hamilton The ecological locking (Morris et al., 1995) model views these Group fossils also afforded resolution of mid-Paleozoic skel- marine communities as tightly structured and therefore, once etal microstructures, which in turn allowed inquiry into bold established, resistant to large-scale taxonomic change. The envi- questions regarding shell structure and evolution, especially of ronmental tracking model, in contrast, interprets stability as aris- bivalves (e.g., Carter and Tevesz, 1978). In addition, outstand- ing when faunas follow environments through time; during an ing Hamilton fossil preservation afforded early analyses of the interval of minimal environmental change, faunas will vary only isotopic signatures of Paleozoic seas (e.g., Popp et al., 1986a, minimally (Ivany, 1996; see also comments by Miller, 1997). 1986b; Veizer et al., 1999, and references therein; Selleck and Ivany (1996) and several others observed that brief intervals of Koff, 2008). accelerated environmental change serve to magnify this coor- In more recent years, Hamilton Group faunas have yet again dinated pattern. Synchronous regional environmental changes, assumed centrality in the lively and prolonged debate over “coor- expressed through sedimentology and geochemistry as well as dinated stasis,” defined as simultaneous taxonomic and, some paleontology, can produce concurrent faunal eliminations that would claim, ecologic stasis within independent clades that include both regional disappearances and true extinction (lineage remain apparently stable for millions of years (Brett and Baird, termination). In sum, the ecological locking hypothesis proposes that the observed patterns originate in ecological homeostatic mechanisms, whereas the environmental tracking model hypoth- 1Now Eldredgeops rana. esizes fidelity of organisms to their environments and posits

coordinated extinctions (or regional disappearances) to create the corresponding reduction of the transgressive phase to a few thin boundaries of intervals of relative stasis. beds that are commonly associated with a diastem and lag con- Coordinated stasis is inherently a quantitative claim. Only centrate of phosphatic and other residual materials. through rigorous quantitative studies that sample rare taxa (not just abundant to common taxa) and that analyze the taxonomic SCOPE AND OBJECTIVES and ecological structure of communities over time can coordinated stasis be properly tested (Bennington and Bambach, 1996; We present here the findings of our quantitative marine McKinney et al., 1996; Ivany et al., 2009). Moreover, dem- paleoecological research on faunas of portions of the lower Ham- onstrating ecological stasis throughout the Hamilton interval ilton Group—specifically, the Cardiff and Pecksport Members requires such quantitative documentation from both lower and of the Middle Devonian Marcellus Subgroup in central New upper intervals. We present here the results of one such quanti- York (Figs. 1 and 2). The lithologies of the Cardiff and Peck- tative study of lower Hamilton communities, as one of several sport Members are well summarized and their faunas illustrated necessary steps in evaluating coordinated stasis models as they in Linsley (1994). These two members occur in the Oatka Creek apply to this Middle Devonian interval. Formation, which is best expressed in the Finger Lakes region The stratigraphic framework for the Hamilton Group was further west; as this formation was established, it became neces- established by Carlton Brett and Gordon Baird, building in turn sary to examine the detailed correlations of these classic Hamil- upon a series of earlier fundamental works by others; see discus- ton Group localities in central New York with the more recently sions of this in the comprehensive stratigraphic volumes edited established lithostratigraphic units in western New York and in by Brett (1986) and Landing and Brett (1991). This classic Ham- eastern New York, closer to the clastic source. How the member- ilton Group lithostratigraphy must be correlated with coarser level lithographic of the two new formations—one in the west, sediments occurring eastward, closer to the deltaic source; these another in the east—correlates through central New York’s clas- eastern strata were studied by Chuck Ver Straeten (Ver Straeten sic Hamilton Group remains to be resolved by the Brett and Ver et al., 2011). These marine sediments of deltaic and other marine Straeten lithostratigraphic teams. We are in a critical transition environments exhibit marked transgressive-regressive cycles zone. Following Selleck (2010), we emphasize the member- (e.g., Brett and Baird, 1985; Brett et al., 1986). These cycles level stratigraphy and its scientific replicability within the central thicken eastward toward the delta and correspondingly thin west- region, with an understanding that the correlations to the east and ward. In western New York, these thinner cycles consist of shale, west will continue to be studied by these other groups. calcareous shale, and limestone, and they are approximately The stratigraphic interval we studied (upper Cardiff and symmetrical (Miller, 1986; Savarese et al., 1986). Further east, in Pecksport Members of the Oatka Creek Formation, Marcellus central and eastern New York, as the source area in the Acadian Subgroup) records the transition between basinal black shales delta is approached, cycles increase in thickness, grain size, and and limestones with pelagic and mixed pelagic-benthic assem- clastic input (e.g., Baird et al., 2000; Ver Straeten et al., 2011); in blages into highly oxygenated benthic communities of siltstones addition, they become dominated by the regressive phase, with a that formed in shallower areas of the depositional basin. Brower

Figure 2. Revised lithostratigraphy of the Marcellus Subgroup of the Figure 1. Location of the Gulf and Swamp Road sections Hamilton Group, Devonian section of New York, as applicable to this and Devonian outcrop belt in New York State. Base map study, excerpted and modified from Ver Straeten et al. (2011). Fm.— is modified from Ivany et al. (2009). Formation; Mbr.—Member; Rd.—Road.

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and Nye (1991), one of our Syracuse group’s earlier contribu- Member exposures extending approximately from 42°54′15″N, tions, also discussed the pelagic and pelagic-benthic communi- 75°55′51″W to 42°54′3″N, 75°55′44″W, along a narrow road ties from the lower Hamilton Group. and creek. Swamp Road, shown in Figure 4, is a small road- We selected two typical outcrops that contain coarsening- side quarry at 42°56′6″N, 75°39′48″W; it has two adjacent por- upward sedimentary sequences and preserve all of the com- tions that can be studied faunally and stratigraphically. The full munities present in this part of the Marcellus Subgroup in data set included 50 taxa and 81 samples. We collected large central New York (Figs. 3 and 4). Gulf Road (Fig. 3), north samples of 300 specimens each to ensure that the presences and of the village of Delphi Falls, is lined by a series of Cardiff proportions of taxa could be adequately characterized. The taxa

COMMUNITY

ARC-EUM

ARC-AMB Medium gray, non-calcareous silty shalewith bedding 0.5 to 2cm thick. ARC-EUM 18m Concretions around smallvertical burrows and cephalopod casts common. B

AM 16m Alloporidcoral bed EUM-

ARC-EUM 14m

EUM

PE ARC-EUM TY 12m

TY ARC-AMB Medium gray, non-calcareous silty ARC-EUM shalewith bedding 0.5 to 2cm thick.

MMUNI Concretions around smallvertical EMA burrows and cephalopod casts Figure 3. Stratigraphic section for upper CO 10m common. D part of Cardiff Member (Oatka Creek

AN Formation, Hamilton Group). The out-

R crop is located on the north side of Gulf

BE Road, 2.2 km south of U.S. Route 20, 8m

UM just east of the hamlet of Pompey Cen- ter, Onondaga County, New York, USA. EN EUM Smallconcretions at 8to 12 cm See Tables 1 and 2 for community codes. PL intervals throughout interval AM 6m LS FAUNA Dark gray, non-calcareous shale. PTER- 4m EUM Finely bedded with beds about 1 cm thick. Microbioturbate

EUM structures throughout. Fossilsvery PTER-EUM rare. Severalzones of ~1 cm 2m limonite stainedconcretions. R

0m CEPH-PTE

-2m 1% 2% 3% WEIGHT%TOTALORGANICS

are listed in Table 1. We reconstructed living habits using these (4) Gastropods: Rollins et al. (1971), Linsley (1977), Hou- and other references: brick (1979), Hickman (1985), and Morris et al. (1991). (1) Brachiopods: Cooper (1937, 1957), Rudwick (1965, (5) Hyolithids: Fisher (1962), Malinky et al. (1987), and 1970), Grant (1972, 1981), Thayer (1981), Bizzarro Baumiller et al. (2010). (1995), and Williams et al. (1997–2007). (6) Trace fossils: Seilacher (1964), Frey (1975), Ekdale et al. (2) Bivalves: Morton (1967), Kauffman (1969), Stanley (1984), Bromley (1991), and Brett et al. (2007). (1970, 1972, 2015), Runnegar (1974), Levinton and The research we present here on marine communities in Bambach (1975), Bailey (1983), Seilacher (1984, 1985), the lower Hamilton Group belongs to a much larger program of and Nagel-Myers et al. (2013, 2018). research at Syracuse University spanning more than 50 yr. With (3) Cephalopods: Flower (1957), Furnish and Glenister coauthor Jim Brower’s death while our manuscript was in review, (1964), Ward and Westermann (1985), Kroger et al. it seems important to sum up this work. In this sustained and col- (2005), and Klug et al. (2010). laborative research effort, we (Cathryn R. Newton and James C.

COMMUNITY Buff to gray blocky coarse 81 MUC-AMB siltstone, poorly bedded. Fossilsuncommon. 80 ARC-AMB 18m

79 MUC-AMB 78 Medium gray shalysiltstone, 77 poorly bedded. Fossils 16m 76 common.

75 B 74 73

72 ARC-AM 14m 71 PE 70 TY 69 MUC-AMB TY Medium gray,non-calcareous 68 12m

B siltyshale.Poorlybeddedwith 67 beds 0.5 to 2cm thick. Fossils MMUNI 66 common. Figure 4. Stratigraphic section for up- CO 65 ARC-AM per part of Pecksport Member (Oatka ND 64 10m Creek, Hamilton Group). The outcrop is

RA 63 on the east side of Swamp Road, 4.3 km

BE 62 Medium gray, non-calcareous north of U.S. Route 20 in the village

M chippy shale. Severalhorizons of Morrisville, Madison County, New UM 61 8m of 3 -10cm diameter York, USA. See Tables 1 and 2 for com-

EN 60 concretions, with sparse small munity codes. PL 59 concretions on 5 to 12 cm ARC-EU

AM 58 intervals throughout section.

LS 57 Fossilscommon. 56 6m 55 EUM-AMB FAUNA 54 ARC-EUM 53 Dark gray, non-calcareous 4m 52 chippy shale. Finely bedded

51 B with beds about1 cm thick. 50 Fossils uncommon AM 49

48 EUM- 2m Burrowed horizon 47 46 45 EUM 0m 1% 2% 3% WEIGHT%TOTAL ORGANICS

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TABLE 1. LIST OF SPECIES AND THEIR CODES Brachiopods 1 Ambocoelia umbonata (Conrad) (AMB) 2 Arcuaminetes scitulus (Hall) (ARC) 3 Camarotoechia congregata (Conrad) (CAM) 4 Cyrtina hamiltonensis (Hall) (CYR) 5 Emanuella subumbona (Hall) (EMA) 6 Eumetabolotoechia multicostata (Hall) (EUM) 7 Lingula sp. (LIN) 8 Mediospirifer audaculus (Conrad) (MED) 9 Mucrospirifer mucronatus (Conrad) (MUC) 10 Orbiculoidea doria (Hall) (ORB) 11 Protoleptostrophia perplana (Conrad) (PRT) 12 Rhipidomella vanuxemi (Hall) (RHI) 13 Schuchertella arctostriata (Hall) (SHU) 14 Spinocyrtia granulosa (Conrad) (SPI) 15 Spinulicosta spinulicosta (Hall) (PRD) 16 Tropidoleptus carinatus (Conrad) (TRO) Bivalves 17 Actinopteria boydi (Conrad) (ACT) 18 Buchiola retrostriata (von Buch) (BUC) 19 Cornellites fasciculata (Goldfuss) (COR) 20 Cypricardella bellistriata (Conrad) (CYP) 21 Goniophora, mostly G. hamiltonensis (Hall) (GON) 22 Gosseletia triquetra (Conrad) (GOS) 23 Grammysia sp., mostly G. bisulcata (Goldfuss) (GRA) 24 Leiopteria sp. (LPT) 25 Modiomorpha spp.; most represent M. concentrica (Conrad), M. mytiloides (Conrad), and M. alta (Conrad) (MOD) 26 Nuculites oblongatus Conrad (NCO) 27 Nuculites triqueter Conrad (NCT) 28 Nuculoidea sp. (NUC) 29 Orthonota undulata Conrad (ORN) 30 Palaeoneilo constricta (Conrad) and Palaeoneilo emarginata (Conrad) (PAL) 31 Paracyclas lirata (Conrad) (PAR) 32 Pholadella radiata (Conrad) (PHO) 33 “Praecardium” robusta (Hall), termed Panenka by many workers (PAN) 34 Pseudoaviculopecten princeps (Conrad) (PSV) 35 Pterochaenia fragilis (Hall) (TER) 36 “Schizodus” appressus (Conrad) (SHZ) Gastropods 37 Bembexia sulcomarginata (Conrad) (BEM) 38 Gyronema lirata (Hall) (GYR) 39 Palaeozygopleura hamiltoniae (Hall) (PZP) 40 Praematuropis ovatus Rollins (PAE) 41 Ptomatis patulus (Hall) (PTO) 42 Sinuotopsis acutilira (Hall) (BEL) Cephalopods 43 Goniatites, mostly Agoniatites vanuxemi (Hall) (AGO) 44 Nephriticeras maximum (Conrad) (NPH) 45 Orthocones with large shells (ORT) 46 Orthocones with small shells (SOT) Tr ilobites 47 Greenops boothi (Green) (GRE) 48 Eldredgeops rana (Green) (RAN) Phyllocarid 49 Echinocaris punctata (Hall) (PHL) Hyolithid 50 Hallotheca sp. (HYO)

Brower) and our students obtained and analyzed large and closely QUANTITATIVE PALEOECOLOGICAL METHODS spaced samples from the shallowing-upward sequences in central New York. Syracuse University faculty actively involved in Biological and sedimentological data were analyzed with this long-term program of Devonian paleontological research, multivariate statistics. Lucid ecological references for the meth- and in working on this with graduate students, include James C. ods applied herein include works by Clifford and Stephenson Brower, Cathryn R. Newton, Linda C. Ivany, Osborne B. Nye (1975), Orloci (1978), Whittaker (1978a, 1978b), Gauch (1982), Jr., and now Christopher Junium. In conducting our quantitative Greig-Smith (1983), Legendre and Legendre (1983, 2012), paleoecological analyses over this span, we and our students have Pielou (1984), Birks and Gordon (1985), Ludwig and Reynolds generally collected large samples, even from sparsely fossilifer- (1988), and Dray et al. (2012). Here, we deployed a variety of ous horizons such as those of the dark shales. In addition, several methods comparable to those used both in community ecology of our students in this larger program have conducted morpho- and in our earlier works on Hamilton Group paleoecology; this logical and paleo-autecological studies of individual Hamilton parallel approach best facilitates comparisons. The basic analyti- Group taxa during these years. Some Syracuse graduate alumni cal strategy follows that of Brower (1987). Initially, clustering supported in this group continue to publish on Hamilton Group and ordination are used to identify and characterize the commu- faunas (e.g., Christopher McRoberts on trilobites and bivalves: nities and gradients present in the data. These are tested subse- McRoberts et al., 2013; Nagel-Myers et al., 2018). quently to ascertain their statistical significance. In the final step, This multidecadal research program at Syracuse University plotting the communities and gradients against geographic and has consistently probed Devonian marine community structure stratigraphic position leads to the construction of a paleoecologi- and composition using systematically collected samples and ana- cal scenario. lyzed with multivariate quantitative methods. During the 35 yr in Previous paleoecological analyses of Middle Devonian mac- which Brower and Newton worked together (1983–2018), we had rofossils have been published by Miller (1986), Savarese et al. the further goal of using these large data sets to test some funda- (1986), Brower (1987), Brower and Kile (1988), Brower et al. mental principles of paleoecology, such as exploring the extent (1978, 1988), Brower and Nye (1991), McCollum (1991), New- to which these paleocommunities were tightly structured. Our man et al. (1992), Bonuso et al. (2002a, 2002b), Nagel-Myers current study fits with both of these long-term aims and forms a et al. (2009, 2013), and others. Earlier, pertinent papers on the key addition to the Hamilton Group record in allowing for tests of somewhat comparable paleoecology of the Upper Devonian sec- both community structure and its temporal persistence. tion of the Appalachians include works by Bowen et al. (1974), The long lineage of Syracuse University studies on the paleo- McGhee (1976), McGhee and Sutton (1981, 1983), Sutton et al. ecology of Devonian siltstones and shales in upstate New York (1970), Sutton and McGhee (1985), and Thayer (1974). Exam- includes Brower and Chute (1964a, 1964b), Nye et al. (1975), ples of earlier quantitative studies that compared clustering and Brower et al. (1978), Brower (1987), Thompson and Newton ordination and/or discussed the significance of communities and (1987), Brower and Kile (1988), Thompson and Newton (1988), gradients in Ordovician rocks were published by Cisne and Rabe Brower et al. (1988), Thompson (1989), Brower and Nye (1991), (1978), Cisne et al. (1982), Lockley (1983), and Springer and Bonuso (2001), Bonuso et al. (2002a, 2002b), Brett et al. (2009), Bambach (1985). Ivany et al. (2009), Ver Straeten et al. (2019), and diverse other We define communities herein as consistent, statistically studies cited therein. Nicole Bonuso and Joel Thompson were recurrent groups of fossils. Both ordination and clustering meth- graduate students who worked with Newton. Another graduate ods are necessary for the recognition of faunal communities and student was Willis Newman, a fine field geologist who collected gradients, because these methods are subject to different types data for this paper, but who did not complete the doctorate and of distortion. Ordination methods preserve the main patterns in who died far too young. the data, but the relationships between similar species and sam- This study critically extends, and in some ways completes, ples are often shown incorrectly. Clustering retains the distances our earlier work by further analyzing community structures in between similar items, but at the cost of large-scale deformation. the Marcellus Subgroup—that basal part of the Hamilton Group In both approaches, we used percentages of species in samples. now famed for its hydrocarbon potential and production (Nya- Computational details of the exact algorithms are available in the hay et al., 2007; Kargbo et al., 2010; Soeder, 2010). Our focus textbooks listed above and Sneath and Sokal (1973). Clusters is not on the lowermost Marcellus Subgroup, which is the site were calculated by the unweighted-pair-group method (UPGM) of most hydrocarbon exploration, but on the intriguing interplay on a matrix of correlation coefficients. The ordination algorithm of communities higher, in the Cardiff and Pecksport Members— consists of correspondence analysis axis ordination or recipro- communities that find some, but not all, ecological counterparts cal averaging. The correspondence analysis was not detrended further upward in the Hamilton Group. This strengthening of because its axes retain the dual space properties of the vari- lower Hamilton Group quantitative paleoecology facilitates able- and specimen-space eigenvectors specified by the Eckart- greater rigor in testing inferences about possible ecological sta- Young theorem (see any textbook on multivariate analysis). As bility and, in particular, ecological locking of marine communi- outlined later, the first two axes of the correspondence analysis ties over 4–6 m.y. of Hamilton Group deposition. are highly arched. Consequently, these were reduced to a single

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axis by calculating orthogonal projections of the data points onto siltstones. Dark-gray shales at the base of these cycles preserve a polynomial as suggested by Ludwig and Reynolds (1988) and bioturbated fabrics at one site (Fig. 3) and are only sparsely bio- Phillips (1978). This is termed the “correspondence analysis axis turbated at the other (Fig. 4). ordination” in later parts of the paper. Clustering and ordination In addition to faunal data, we analyzed grain size (scaled lead to similar and complementary conclusions. meristically from 1.0 for shale to 5.0 for siltstone) and weight The groups of samples recognized in the clusters and ordi- percent of total organics (measured by loss on ignition). These nations should be tested for statistical significance. We elected lithologic variables were then analyzed relative to the percent- to employ significance tests for clusters rather than discriminant ages of common species in the assemblages. Statistics con- analysis because they are largely independent of the number of sidered included correlation coefficients, multiple correlation variables (taxa in this case), and they are less sensitive to statisti- coefficients, and regression weights for polynomials, where the cal assumptions. correspondence analysis axis ordination of species composition Inasmuch as cluster significance tests are probably not was written as a function of the lithologic code and/or organic familiar, the statistical methods will be outlined briefly (for content. Inasmuch as the organics were measured continuously, details, see Sneath, 1977, 1979). Visualize an axis connecting whereas the grain size was coded meristically, it is difficult to the centroids of two clusters of samples in the space defined by compare regression coefficients based on both parameters. Visual the species. The samples are projected onto this axis to form inspection and significance tests suggested that third-order poly- q (or Q) scores or distributions that illustrate the differences nomials provide reasonable fits to the data. These polynomials between the two clusters. These q scores are analogous to the were calculated for the lithology, organic matter, and lithology scores of discriminant functions, except that they are more con- and organic matter considered together. The conclusions were servative, because the differences between the two clusters may largely based on comparing the squared multiple correlation not be maximized. Various tests can be applied to the q distribu- coefficients. Interactions between lithology and organic matter tions. The conventional hypothesis for univariate or multivariate were not treated, because significance tests indicated that the means ascertains whether or not the differences between them interactions did not explain significant components of the vari- are statistically significant subject to a predetermined risk level. ance for the dependent variable. This is obviously trivial for groups that have been previously The squared multiple correlations for the correspondence identified by cluster analysis; one almost invariably rejects axis ordination versus the lithology and organics were 0.758 and the null hypotheses, even if the two groups overlap greatly. It 0.802, respectively, whereas the same value for both lithology is much more informative to query whether the samples were and organics was 0.855. (Detailed results of the correspondence drawn from two populations that overlap more or less than some axis ordination, including relation of lithologic data to com- specified amount. The degree of overlap of the q distributions is munities, appear in the “Sequence of Communities” section.) measured by the W statistic of disjunction. Thus, the correspondence axis ordination seems to represent an We regard communities as consistent faunal associations approximately equal compound of organic matter and grain size that may intergrade. The communities studied here changed in if all eight communities are considered. This is evidenced by the response to a paleoecological shallowing gradient caused by a fact that the variances associated with the two polynomial regres- marine regression. Consequently, a rectangular distribution of the sions for the organics and lithology do not differ significantly. q scores provides a reasonable null hypothesis (Sneath, 1977). In The regression for both lithology and organic matter explains a a rectangular distribution, the observed number of samples along significantly larger amount of the variance in the ordination than equal intervals of the q scores follows a Poisson distribution, so those of lithology or organic matter alone. The F ratio for the the q distributions lack extended tails and behave like censored added component of variance is 6.91 with 3 and 65 degrees of data. The null hypothesis specifies that the q scores of the two freedom, which is significant at the 0.05 and 0.01 probability lev- clusters are drawn from overlapping rectangular distributions. els. The seven exclusively benthic communities yielded similar The alternative hypothesis is that the q distributions of the two results, except that grain size was slightly more important than clusters are disjunct. The critical test values were obtained from organic matter. Sneath (1979, fig. 2). CLUSTER ANALYSIS FACIES ANALYSIS Figure 5 illustrates the dendrogram for 81 samples based on In these Hamilton Group regressive intervals in central 50 species and the unweighted-pair-group method clustering of New York, lithofacies vary consistently in ways that are trace- a matrix of correlation coefficients. Eight main clusters or com- able laterally but exhibit a narrow range of lithologic variation. munities can be recognized at correlations of 0.7 and higher. The cycles at our two study sites are typical: They begin in basal The dendrogram is tightly structured, and virtually all of the strata of dark-gray, noncalcareous shales (Figs. 3 and 4). These links within the clusters take place at levels of 0.85 and higher. are overlain by progressively siltier, concretion-rich shales, and Communities will be discussed in order of increasing grain size each regressive cycle culminates in noncalcareous silty shales or and decreasing organic content. As seen in Figures 3 and 4, the

Figure 5. Dendrogram for 81 samples. The data matrix consists of percentages of 50 species in each sample. The clusters are based on the unweighted-pair-group method of a matrix of correlation coefficients. The stratigraphic distributions of samples are shown on Figures 3 and 4.

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lithologies vary, including relatively dark and fine-grained shales attached spiriferid brachiopod. We thus designate this the Eman- and siltstones with 3% total organic matter; gray silty shales with uella community. Eumetabolotoechia multicostata and Arcuami- lower organic content; and siltstones in with approximately 2 netes scitulus each typically account for 10%–15% of the fauna. wt% of total organic matter. A few shells of Mucrospirifer mucronatus and Nuculoidea sp. Samples 1–9 on the dendrogram constitute the Cephalopod- are associated (Table 2). Although the geographic distribution of Pterochaenia community (Fig. 5). Diversity is low, with only this assemblage is uncertain, it seems locally to be restricted to three to eight species per sample. Cephalopods dominate the a small stratigraphic interval within the Cardiff Member along community; these include both large orthocones and Agoniatites Gulf Road. vanuxemi, which represent from 43% to 81% of the individu- The Arcuaminetes-Eumetabolotoechia community, repre- als, respectively (Table 2). Pterochaenia fragilis, also common sented by samples 27–44 on the clusters in Figure 5, is domi- (11%–30% of the community), is enigmatic in terms of living nated by Arcuaminetes scitulus and Eumetabolotoechia multico- habits; it is clearly a byssate suspension feeder (e.g., Brower stata, which together generally comprise slightly over 50% of and Nye, 1991; see illustrations in Clarke, 1904), but the site of each sample. In most samples, these are followed by Ambocoelia byssal attachment (i.e., benthic vs. epipelagic) is uncertain. We umbonata, Nuculoidea sp., Mucrospirifer mucronatus, Lingula interpret it here as a nonendemic benthic opportunist, but we sp., and Nuculites oblongatus (in decreasing order of abundance). recognize that others might also reasonably infer it was an epi- A few specimens of large orthocones and Bembexia sulcomar- planktonically attached taxon; this can likely be resolved with ginata occur in most samples (Table 2). further studies. Eumetabolotoechia multicostata also occurs in The Arcuaminetes-Ambocoelia community characterizes the many samples. This community characterizes the finest-grained sequence of samples 28–73 on the dendrogram. Approximately rocks observed in this study—namely, thinly bedded dark-gray half of the individuals consist of Arcuaminetes scitulus, in con- shales with small burrows and relatively high organic contents junction with highly variable numbers of Ambocoelia umbonata. (averaging 3.0 wt%). Other common constituents in most samples include Mucro- Samples 10, 12, and 13 belong to the Pterochaenia- spirifer mucronatus, Nuculoidea sp., and Emanuella subumbona. Eumetabolotoechia community. Pterochaenia fragilis and the Eumetabolotoechia multicostata is conspicuously absent from pedicle-attached brachiopod Eumetabolotoechia multicostata most samples (Table 2). are about equally abundant, together accounting for 85% of the Four samples, numbers 69, 78, 79, and 81, are assigned to assemblage. Emanuella subumbona, Nuculoidea sp., and large the Mucrospirifer-Ambocoelia community (Fig. 5). The pedicle- orthocones occur consistently in minor proportions (Table 2). attached brachiopod Ambocoelia umbonata and the recliner The Eumetabolotoechia community contains samples Mucrospirifer mucronatus lead the roster of species, but signifi- 11–24 on the cluster diagram (Fig. 5). The pedunculate rhyn- cant numbers of Arcuaminetes scitulus also occur. Spinocyrtia chonellid Eumetabolotoechia multicostata invariably dominates; granulosa, Tropidoleptus carinatus, Nuculites oblongatus, Bem- in one sample, it represents 81% of the individuals present. Other bexia sulcomarginata, and Modiomorpha spp. are frequently taxa encountered in all or most samples are (in decreasing order accessory taxa (Table 2). of abundance): Emanuella subumbona, Pterochaenia fragilis, The Mucrospirifer-Ambocoelia and Arcuaminetes-Ambocoelia Nuculoidea sp., and Arcuaminetes scitulus (Table 2). Samples communities occupy the coarsest sediments at both the Gulf 11–45 join the cluster at high correlation coefficients of 0.955– Road and Swamp Road localities. These sediments are gray silty 0.997. However, samples 31 and 24 group at somewhat lower shales and siltstones that are relatively thick and poorly bedded. values of 0.903 and 0.885; these two samples also contrast in Average organic matter content is 2.17%–2.3%. having a slightly higher species richness and a somewhat lower The previous discussion indicates that the communities are proportion of Eumetabolotoechia. mainly defined by the most common or dominant species. This Fourteen samples, listed from 35 to 55 on the dendrogram, was expected for clustering of a matrix of correlation coefficients represent the Eumetabolotoechia-Ambocoelia community. Eume- between the original percentages of taxa within samples. tabolotoechia multicostata and, to a lesser extent, the pedicle- Consequently, we further explored community composition by attached brachiopod Ambocoelia umbonata and the recliner Arcu- calculating constancy (proportion or percent of samples within a aminetes scitulus form the core of this cluster. Eumetabolotoechia community in which a species, say species i, is present) and fidelity and Ambocoelia individuals occur in all samples, whereas Arcua- (proportion or percent of samples within a community, with species minetes is present in only 13 samples. Although generally pres- i divided by total number of samples over all communities contain- ent, Nuculoidea sp., Nuculites oblongatus, and large orthocones ing that species). The basic pattern is clear (Table 2). are less abundant; they typically constitute 1% to 5% of any one Species with high constancies generally have low fidelities sample. Accessory species that occur in approximately half of for any one community, and vice versa. This reflects the eco- the samples are Mucrospirifer mucronatus, Pterochaenia fragilis, logical strategies of Hamilton Group taxa. Common forms are Lingula sp., and Palaeozygopleura hamiltoniae (Table 2). broadly adapted and inhabit a wide variety of communities and Samples 25 and 26 differ greatly from all others; more than environments. Such organisms are ecological generalists. Con- 50% of the fauna is Emanuella subumbona, a small, pedicle- versely, forms with a high fidelity for a certain community are

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/5177698/spe545-09e.pdf by guest on 02 October 2021 Quantitative paleoecology of marine faunas in the lower Hamilton Group (Middle Devonian, New York) 171) er if — — — — — Continued 0.799 0.671 4.000 2.170 0.678 7.500 0.328* 2.190** 0.517 2.770* 1.870** 0.326 0.593 ( 15.800 38.700 47.000 35.200** 18.6** 23.700** (MUC-AMB) - Ambocoelia Mucrospir —— 0.710 0.600 3.410 2.300 3.170* 0.019 0.057 7.120 0.928 0.098 1.260* 0.453 1.940* 0.804 0.039 0.538 6.980** 0.750 1.350* 15.500 23.700 60.900 18.200** 49.100** Ambocoelia (ARC-AMB) Arcuaminetes - — 0.831 0.756 2.270 0.712 2.670 4.890* 0.075 6.330 0.530 0.551 9.280** 1.140 0.698 0.844 6.150** 0.847 13.000 37.900 22.400** 40.800 31.8** (ARC-EUM) Arcuaminetes - Eumetabolotoechia —— — — — —— — —— — 0.533 0.559 2.530 9.000 1.510** 0.505** 3.000 4.500 0.274 0.427 6.430** (EMA) 61.400* 78.200 14.700** 18.600 12.200** Emanuella UCTURE OF COMMUNITIES — —— 0.724 0.680 2.380 0.498 0.094 0.095 2.140 6.210 0.095 0.490 0.621 0.400 0.434 3.440* 0.319 11.900 59.300 44.700** 13.400** 21.300 17.200** Ambocoelia (EUM-AMB) - Eumetabolotoechia Community —— — — (EUM) 0.507 0.538 2.730 8.790 0.474 0.024 2.000 5.210 9.220** 1.390 0.024 7.410 0.337 2.330 *— 4.780** 0.467 0.024 0.310 77.100 65.900** AXONOMIC AND ECOLOGICAL STR T Eumetabolotoechi a GE

VERA A —— —— 0.535 0.583 2.840 8.330 0.753** 1.000 5.000 4.210** 2.910 0.438 0.543 1.520* 0.626 0.852 45.600 40.600** (PTER-EUM) Pterochaeni a ABLE 2. T - Eumetabolotoechi a — —— —— —— — —— —— —— — —— 0.542 0.814 3.000 5.220 1.000 8.670 3.560 7.890* 0.778 1.110 0.361 1.110 0.713 ephalopod - Pterochaeni a (CEPH-PTER ) ucture

(Hall) (Hall )—

lana ersity ersity

(Hall) eeders

(Hall) es

iat a

inatus a (Hall) nuxemi umbona (Hall) va C or species or ecological (Hall) er mucronatus er audaculus f if ella arctostr tia granulosa es es mation function div mation function div tina hamiltonensis (Hall )— ight percent of organic or or edicle-attached suspension axonomic and ecological str ropidoleptus car or species eeders or ecological catego ri f Inf Equitability f (Conrad) Orbiculoidea do ri Rhipodomella Number of ecological catego ri We matter Number of species Eumetabolotoechi a multicostata Mediospir General characteristics Lithologic code T P f Spinocyr (Conrad) Ambocoelia umbonata (Conrad) f Inf Emanuella sub Reclining suspension f Arcuaminetes scitulus Equitability f catego ri (Conrad) T Camarotoechia congregata (Conrad) Cyr Spinulicosta spinulicost a (Conrad) Mucrospi ri Protoleptostrophia pe rp (Conrad) Schuche rt

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/5177698/spe545-09e.pdf by guest on 02 October 2021 172 Newton et al. ) er if — — — — — Continued 0.847 1.700 0.251* 0.336* 0.268 0.407 0.520* 0.339 0.663* 0.945** 0.169 1.750 1.410** 2.710 ( (MUC-AMB) - Ambocoelia Mucrospir — —— 0.333 0.623 0.057 0.020 0.177 0.059 0.374 0.117 1.210 0.824 0.098 0.057 0.527 0.020 3.390 0.020 1.340* 1.210 Ambocoelia (ARC-AMB) Arcuaminetes - ) — — 1.170 0.369 0.037 0.075 0.038 0.073 3.100* 0.334 0.239 0.093 4.430 0.092 0.92 1.520 (ARC-EUM) Arcuaminetes - Eumetabolotoechia — — —— — —— —— — — — — —— — 0.167 0.148 0.167* 0.167* 0.167 (EMA) Emanuella UCTURE OF COMMUNITIES ( Continued — —— —— —— 2.890* 0.330 0.097 0.263 0.048 1.830* 0.238 0.88 0.024 3.250 3.14 0.379 Ambocoelia (EUM-AMB) - Eumetabolotoechia Community —— —— — —— — —— (EUM) 7.360** 0.095 0.068 0.024 0.213 0.095 0.095 0.024 7.590 0.424 0.305 Eumetabolotoechi a AXONOMIC AND ECOLOGICAL STR

T GE —— —— —— 0.868* VERA 44.800** 45.700 A (PTER-EUM) Pterochaeni a - Eumetabolotoechi a ABLE 2. T —— —— —— —— —— —— —— —— —— —— —— —— —— —— 3.000** 0.222 ephalopod 23.200 - Pterochaeni a (CEPH-PTER ) .

on M. M.

(Hall )2 . iata w G. cf G. a (Conrad )— . anenka) cf (Conrad) . . iata (v (Conrad) ydi (Conrad )— ., cf ., cf C (?P spp .— iquetr asciculata sp (Conrad), sp a . ia bo ph a sp (Hall ) (Goldfuss) viculopecten ic a a (Conrad ) ysi a yssate suspension yssate suspension wing suspension odus appressus usta ellites f icardella bellistr yssate or shallo racyclas lirata thonota undulata Conrad inceps ytiloides (Conrad), and M. eders rob eeders eeders Endob f Pterochaenia fragilis Goniophor Gramm Modiomor bisulcata hamiltonensi s (Hall) P. “Praecardium” Pseudoa pr Or (Goldfuss) concentr m Leiopte ri Co rn Gosseletia tr Lingul a sp alta (Conrad ) (Conrad) Buchiola retrostr Buch ) Pholadella radiata Burro f Cypr (Conrad) Schiz endob fe Epib Actinopter Pa

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/5177698/spe545-09e.pdf by guest on 02 October 2021 Quantitative paleoecology of marine faunas in the lower Hamilton Group (Middle Devonian, New York) 173 er if — — — — — 0.089 0.083 0.590* 5.600 0.083 2.060** 2.19 1.510** 2.110* 0.997* 0.424 0.332 0.081 0.081 0.169 (MUC-AMB) - Ambocoelia Mucrospir * and **, by — —— —— — 0.02 0.059 0.137 1.290* 0.039 6.550 0.039 0.02 1.160* 2.45 0.959** 0.861 3.680** 0.845 1.040 0.788* 0.216 0.039 Ambocoelia (ARC-AMB) Arcuaminetes - ) 0.056 0.037 0.037 0.018 0.016 0.709 1.72 0.922* 2.660** 1.150 7.370** 0.390 1.750 0.358 1.370* 0.018 11.600 (ARC-EUM) Arcuaminetes - Eumetabolotoechia — —— — — — —— —— —— — — — — — —— ters of the samples in a community are denoted 0.171* 2.550 2.370** 0.342 0.342* (EMA) Emanuella UCTURE OF COMMUNITIES ( Continued —— —— —— 0.069 0.738* 3.32** 1.21 0.405 4.990** 1.320 0.831 0.975 0.071 1.250** 10.100 Ambocoelia (EUM-AMB) - Eumetabolotoechia Community —— —— —— — —— —— —— — — —— (EUM) 0.234 5.940 5.230** 1.460 0.214 0.262 0.222 1.240* . Species present in at least half and three quar Eumetabolotoechi a . AXONOMIC AND ECOLOGICAL STR T GE —— —— —— —— 3.670 3.670** 2.160 0.325 1.8300** VERA or siltstones A (PTER-EUM) Pterochaeni a - Eumetabolotoechi a ABLE 2. ies are listed as percentages T or shales to 5 f —— —— —— —— —— —— —— —— —— —— —— —— —— 0.333 0.333 1.110 1.110 ephalopod 65.600 19.100** 46.500** - Pterochaeni a (CEPH-PTER )

s—

ms (Hall) rm r (Hall) eeders fo a fo hamiltoniae Agoniatites icta (Green) atus Rollin s— (Hall) emarginata (Hall)

ov C . P. or taxa and ecological categor . longatus Conrad , large , small . Lithology is coded from 1 f sp sp ly , mostly is punctata (Hall) Data f xia sulcomarginata iticeras maximum wing deposit f engers iqueter Conrad ace grazers v laeozygopleura laeoneilo constr thocones thocones nuxemi tr Note: “Collectors” Sinuotopsis acutilir Echinocar Ptomatis patulus Praematuropis Pa (Hall) Hallotheca Nuculites ob Swimming predators and sca Greenops boothi (Green) Eldredgeops rana N. Bembe (Conrad) Gyronema lirata Burro Nuculoidea Pa Surf (Conrad) and (Conrad) respecti ve Goniatites Or va Or Nephr (Conrad)

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environmentally restricted, specialized, and usually rare. Also, Cluster 7: Lingula to Echinocaris. Broadly adapted, com- such taxa are usually restricted to one or a small number of sam- mon to rare organisms ranging from the Eumetabolotoechia to the ples within that community. Figure 6 illustrates the distribution Mucrospirifer-Ambocoelia communities, with all or most being of species in samples, showing that only a few taxa are found in recorded in the four communities from the coarsest sediments. a large number of samples, and vice versa. Cluster 8: Praecardium and Orthonotus. Rare taxa in Clusters were also generated for the 50 species (Fig. 7). As the Eumetabolotoechia-Ambocoelia and Arcuaminetes- is usual for paleoecological data, this dendrogram is much more Eumetabolotoechia communities. loosely structured than that for the samples. For example, only Cluster 9: Pholadella to Gyronema. Rare forms, mostly in 6% and 14% of the links are above correlation coefficients of the Arcuaminetes-Ambocoelia community. 0.70 and 0.60, respectively. Despite low levels of similarities, the Cluster 10: Schuchertella to Grammysia. Wide-ranging, clusters do identify coherent groups of taxa with common distri- rare species found in communities varying from Pterochaenia- bution patterns, as shown below in telegraphic form. The species Eumetabolotoechia to Mucrospirifer-Ambocoelia communities; all are listed as given on the dendrogram. of these taxa are known from the Arcuaminetes-Eumetabolotoechia Cluster 1: Eumetabolotoechia to Orbiculoidea on the den- and Arcuaminetes-Ambocoelia communities. drogram of Figure 7. Common and rare taxa found in fine sediments; these taxa are most abundant in the Eumetabolotoechia, CORRESPONDENCE ANALYSIS Eumetabolotoechia-Ambocoelia, Emanuella, and Arcuaminetes- Ambocoelia communities. The first three axes of the correspondence analysis for 81 sam- Cluster 2: Pterochaenia to Hallotheca. Common and rare spe- ples and 50 species account for 30.4%, 17.9%, and 10.2% of the cies found in the finest sediments, mostly from the Cephalopod- information in the data set, respectively. The third axis mainly polar- Pterochaenia and Pterochaenia-Eumetabolotoechia communities. izes the unique Emanuella subumbona community from the rest, Cluster 3: Arcuaminetes to Eldredgeops. Widely tolerant, and this axis will not be discussed further. Correspondence axes I common to rare forms, generally from the Eumetabolotoechia and II display the overall relations between the eight communities to Mucrospirifer-Ambocoelia communities; all or most spe- (Fig. 8A). The communities are arranged in a horseshoe-shaped cies occur in the Arcuaminetes-Ambocoelia and Mucrospirifer- figure in a systematic sequence: (1) the Cephalopod-Pterochaenia Ambocoelia communities. community; (2) the Pterochaenia-Eumetabolotoechia commu- Cluster 4: Cornellites and Ptomatis. Rare species in the nity; (3) the Eumetabolotoechia community; (4) the Emanuella Mucrospirifer-Ambocoelia community. community and (5) the Eumetabolotoechia-Ambocoelia com- Cluster 5: Rhipidomella and Modiomorpha. Rare species in munity; (6) the Arcuaminetes-Eumetabolotoechia community; a variety of assemblages, ranging from the Eumetabolotoechia to (7) the Arcuaminetes-Ambocoelia community; and (8) the Mucro- the Mucrospirifer-Ambocoelia communities. spirifer-Ambocoelia community. The Emanuella community is Cluster 6: Leiopteria to Greenops. Rare species, mostly cen- most closely linked to that of Eumetabolotoechia. Interestingly, tered in the Arcuaminetes-Ambocoelia and adjacent communities. these relations resemble those that could be inferred from the dendrogram of Figure 7, except that the position of the Emanu- ella community is greatly distorted by the clusters. From left to right on the graph of the correspondence analysis (Fig. 8A), the 60 communities reflect a trend of increasing sedimentary grain size, generally decreasing amounts of organic matter, and increasing 50 sedimentary bed thickness. This sequence presumably reflects an overall tendency of decreasing depth, increasing agitation, and

40 higher amounts of oxygenation. Furthermore, the sequence also replicates the most frequent vertical changes between and within communities, as annotated below. FEWER SAMPLES 30 Other information can also be gleaned from the correspondence analysis plot. The wide gap between the Cephalopod- N OR 20 Pterochaenia and the Pterochaenia-Eumetabolotoechia com- SI munities is notable. This gap indicates considerable cleavage 10 between the two groups and suggests much variance between SPECIE the two clusters. However, the Cephalopod-Pterochaenia and

0 Pterochaenia-Eumetabolotoechia communities sometimes occur 020 40 60 80 in adjacent samples. Perhaps a critical or threshold change in one or more environmental parameters dictated the assemblage NUMBER OF SAMPLESWITH SPECIES i that is found. Likewise, the Pterochaenia-Eumetabolotoechia Figure 6. Graph showing exponential distribution of species in samples. community is discontinuously separated from the more diverse

and shallower-water communities that are closely packed on the first two axes for the samples groups the communities from right side of the graph. Although they tend to occupy different Pterochaenia-Eumetabolotoechia to Mucrospirifer-Ambocoelia, regions in the correspondence axis plot, overlap can be seen but the intergradations between the Eumetabolotoechia, Eume- between the Eumetabolotoechia and the Eumetabolotoechia- tabolotoechia-Ambocoelia, Arcuaminetes-Eumetabolotoechia, Ambocoelia communities, the Eumetabolotoechia-Ambocoelia Arcuaminetes-Ambocoelia, and Mucrospirifer-Ambocoelia com- and the Arcuaminetes-Eumetabolotoechia communities, the munities are illustrated more clearly (Fig. 8B). Although the Arcuaminetes-Eumetabolotoechia and the Arcuaminetes- second axis isolates the Emanuella community from the others, Ambocoelia communities, and the Arcuaminetes-Ambocoelia this assemblage remains closest to that of the Eumetabolotoechia and the Mucrospirifer-Ambocoelia communities. community. The third correspondence axis, which is associated To study the patterns for the more shallow-water commu- with 9.07% of the variance, separates the Pterochaenia-Eume- nities, we performed another correspondence analysis, in which tabolotoechia community from the rest of the data; it thus does the nine samples of the Cephalopod-Pterochaenia community not provide any new information. were deleted in order to decrease the total dispersion of the data Figure 9 contains the first correspondence axes for the 50 set. Axes I and II extracted 27.7% and 14.8% of the variance of species in all 81 samples. The horseshoe-shaped pattern for the the 72 samples and 50 species, respectively. The graph of the taxa duplicates that of the samples and communities. The organ-

CORRELAT ION COEFFICIENT 0.00.1 0.20.3 0.40.5 0.60.7 0.80.9 1.0

GRAMMYSIA BISULCATA CAMAROTOECHI A CONGREGATA GONIOPHORA HAMILTONENSIS SPINULOCOSTA SPINULOCOSTA 10 MEDIOSPIRIFER AUDACULUS PROTOLEPTOSTROPHIA PERPLANA SCHU CHERTELLA ARCTOSTRIATA GYRONEMA LIRATA SINUOTOPSISACUTI LIRA PALAEOZYGOPLEURA HAMILTONIAE SMALLORTHOCONES 9 CYPRICARDELLA BELLISTRIATA PHOLADELLA RADI ATA ORTHONOT AUNDULATA PRAECARDIUM ROBUSTA 8 ECHI NOCARISPUNCTATA SCHI ZODU S APPRESSUS PALEONEILO SP. NUCULITES OBLONGATUS 7 NUCULITES TRIQUETER LINGULA SP. GREENOPS BOOTHI PSEUDAVICULOPECTEN PRINCEPS 6 LEIOPTERIA SP. MODIOMORPHA SP. RHIPIDOMELLA VANUXEMI 5 PTOMATIS PATULIS CORNELLITES FLABELLUM 4 ELDREDGEOPS RANA PRAEMATUROTROPIS OVATUS GOSSELETIA TRIQUETRA CYRTINA HAMILTONENSIS PARACYCLAS LIRATA MUCROSPIRIFER MUCRONATUS NEPHRITI CERAS MAXIMUM 3 BEMBEXIA SULCOMARGINATA SPINOCYRTIA GRANULOSA ACTINOPTERIA FASCICULATA TROPIDOLEPTU S CARINATUS AMBOCOELIA UMBONATA ARCU AMINETES SCITULUS HALLOTHECA SP. AGONIATITES VANUXEMI LARGE ORTHOCONES 2 PTEROCHAENIA FRAGILIS ORBICULOIDEA DORIA EMANUELLASUBUMBONA BUCHIOLA RETROSTRIATA NUCULOIDEA SP. 1 EUMETABOLOTOECHIAMULTI COSTATA

Figure 7. Dendrogram for 50 species. Algorithm is same as for Figure 5.

Downloaded from http://pubs.geoscienceworld.org/books/book/chapter-pdf/5177698/spe545-09e.pdf by guest on 02 October 2021 176 Newton et al.

CEPH -PTER 1 PTER-EUM EUM

S II EUM-AMB 0

AXI EMA ARC -EUM ARC -AMB -1 MUC -AMB

Figure 8. Graphs of samples from axes -2 I and II of the correspondence analy- -4 -3 -2 -1 01 sis. (A) Eighty-one samples from eight communities. Axes I and II account for AXIS I 30.4% and 17.9% of the information in the data. (B) Seventy-two samples from seven communities. The nine samples from the Cephalopod-Pterochaenia community were deleted in order to compare principally benthic communities. Axes I 6 and II explain 27.7% and 14.8% of the variance in the data. The samples are designated by the community types discussed in the text. The species codes are 4 listed in Tables 1 and 2. PTER -EUM EUM

S II EUM-AMB 2

AXI EMA ARC -EUM ARC -AMB 0 MUC -AMB

-2 -3 -2 -1 012

AXIS I

isms that are restricted to the finest-grained and darkest shales lie Emanuella, and Mucrospirifer-Ambocoelia communities were on the left side of the graph. Proceeding from left to right along deleted because of the small numbers of samples (which var- the horseshoe, taxa represent associations found in progressively ied from two to four, in the communities deleted). Allowing coarser rocks and shallower lithofacies. for the missing communities, all pairs of communities that occurred adjacent stratigraphically were tested; the results are CLUSTER SIGNIFICANCE TESTS given in Table 3. Student’s t values demonstrate that mean species composi- Cluster significance tests were applied to the communities tions of all pairs of communities differ significantly at the 0.01 known from adequate numbers of samples, namely, Cephalo- probability level. The multivariate means of the different com- pod-Pterochaenia, Eumetabolotoechia, Eumetabolotoechia- munities were clearly derived from different populations. How- Ambocoelia, Arcuaminetes-Eumetabolotoechia, and Arcua- ever, this hypothesis tells little about the amount of overlap minetes-Ambocoelia. The Pterochaenia-Eumetabolotoechia, between the parent populations. This information is provided by

EUM MED EMA NUC BUC RHI 2 TER PAN RAN HYO ORN ORT NCO 1 AGO AMB GOS ARC PRD 0 GRA PAL II PTO

IS ORB BEL AX SHU PHO -1 CYR BEM PHL GON LIN MUC 2 NCT CYP SHZ PZP TRO GRE PRT PAE -3 -3.5 -2.5 -1.5 -0.5 0.5 NPH PAR GYR PSV CAM COR ACT AXIS I MOD SOTLPT SPI Figure 9. Graph of species from axes I and II of the correspondence analysis for 81 samples. The species codes are listed in Table 1.

the W statistics of disjunction, which were tested using the data of SEQUENCE OF COMMUNITIES Sneath (1979). The W figures denote that most pairs of communities were drawn from populations with rectangular distributions Figures 3 and 4 show the stratigraphic sections with the that do not overlap, again subject to a risk of 0.01. However, the communities superimposed. The stratigraphic order of the com- Eumetabolotoechia-Ambocoelia community overlaps with the munities is summarized in Figure 10 for the two sections and Eumetabolotoechia and Arcuaminetes-Eumetabolotoechia com- their composite. Each arrow denotes a vertical change from munities in terms of rectangular distributions. The Eumetabo- older to younger rocks. In general, the composite sequence of lotoechia and Arcuaminetes-Eumetabolotoechia communities communities, listed from base to top, is Cephalopod-Ptero- are completely disjunct. The statistics suggest that one assem- chaenia, Pterochaenia-Eumetabolotoechia, Eumetabolotoechia, blage, the Eumetabolotoechia-Ambocoelia community, may not Emanuella or Eumetabolotoechia-Ambocoelia, Arcuaminetes- have occupied a completely separate region in the ecological gra- Eumetabolotoechia, Arcuaminetes-Ambocoelia, and Mucro- dient seen in the Cardiff Member. spirifer-Ambocoelia; this sequence agrees with that given by

TABLE 3. RESULTS OF CLUSTER SIGNIFICANCE TESTS Pairs of communities W statistic of disjunction Total sample Observed percent of Student’s t values comparing (** denotes values size overlap in q scores multivariate means (** denotes signiﬁ cant at 0.01 values signiﬁ cant at 0.01 probability level) probability level) Cephalopod-Pterochaenia versus 3.340** 23 0 16.000** Eumetabolotoechia Eumetabolotoechia versus 1.83 28 7.14 9.680** Eumetabolotoechia-Ambocoelia Eumetabolotoechia-Ambocoelia versus 1.62 32 0 9.1500** Arcuaminetes-Eumetabolotoechia Eumetabolotoechia versus 3.220** 32 0 18.200** Arcuaminetes-Eumetabolotoechia Arcuaminetes-Eumetabolotoechia 2.980** 35 0 17.600** versus Arcuaminetes-Ambocoelia

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COMPOSITESECTION GULF ROAD SECTION SWAMPROADSECTION

MUCROSPIRIFER -AMBOCOELIA MUCROSPIRIFER-AMBOCOELIA

ARCUAMINETES -AMBOCOELIA ARCUAMINETES-AMBOCOELIA ARCUAMINETES-AMBOCOELIA

ARCUAMINETES -EUMETABOLOTOECHIA ARCUAMINETES -EUMETABOLOTOECHIA ARCUAMINETES-EUMETABOLOTOECHIA

EMANUELLA EUMETABOLOTOE. -AMBOCOELIA EMANUELLA EUMETABOLOTOECHIA-AMBOCOELIA EUMETABOLOTOECHIA- AMBOCOELIA

EUMETABOLOTOECHIA EUMETABOLOTOECHIA EUMETABOLOTOECHIA

PTEROCHAENIA -EUMETABOLOTOECHIA PTEROCHAENIA -EUMETABOLOTOECHIA

CEPHALOPOD -PTEROCHAENIA CEPHALOPOD -PTEROCHAENIA

Figure 10. Vertical changes of communities from the two sections and their composite.

the correspondence analysis. Several lines of evidence suggest Arcuaminetes-Eumetabolotoechia communities in the middle of that this sequence reflects decreasing depth. The basic sequence, Swamp Road; and Arcuaminetes-Ambocoelia and Mucrospirifer- ranging from the Cephalopod-Pterochaenia to Mucrospirifer- Ambocoelia communities in the upper part of Swamp Road (Figs. Ambocoelia communities, correlates strongly with increasing 3, 4, and 10). Obviously, the two sections experienced times in sedimentary grain size, increasing bed thickness, and progres- which benthic communities (and possibly environmental condi- sively more intense bioturbation; it also relates to decreasing tions) fluctuated considerably. amounts of organics, increased species richness, and ecological Different ranges of communities and environments occur diversity. Thus, the main trend is one of decreasing depth, with in the two stratigraphic sequences. The oldest and youngest changes in associated parameters, such as increasing agitation, communities at the Swamp Road section consist of Eumetabo- and we acknowledge that additional ecological factors may also lotoechia and Mucrospirifer-Ambocoelia, but those at Gulf have been operative. Road vary from Cephalopod-Pterochaenia to Arcuaminetes- The two collections with the Emanuella community are only Eumetabolotoechia and Arcuaminetes-Ambocoelia. Thus, the known at the Gulf Road section; these samples follow a large Swamp Road area began and ended in shallower habitats than stratigraphic interval dominated by the Eumetabolotoechia com- did the Gulf Road section. munity and are in turn overlain by the Arcuaminetes-Eumetabo- The relations between the samples are shown by the first two lotoechia community (Figs. 3 and 10). The lithology and organic axes of the correspondence analysis, as has been discussed above content of the Emanuella samples resemble those of the Eume- (Fig. 8A). Inasmuch as the overall pattern involves both axes, the tabolotoechia community. Both Eumetabolotoechia and Emanu- data were combined into a single sequence, which will be termed ella subumbona are pedicle-attached brachiopods, although they the correspondence ordination. First, a fourth-order polynomial exhibit few other common features. For example, the former is was fitted to the first two axes of the correspondence analysis, a rhynchonellid, whereas the latter is a spirifer, and Emanuella yielding a squared correlation coefficient of 0.890 (Fig. 11). Next, subumbona is much smaller than Eumetabolotoechia multico- orthogonal projections of the 81 samples onto the polynomial stata. The paleoecological changes involved here are not entirely were determined. Finally, the polynomial was “unfolded” and certain and are discussed later. scaled so that the points on the left and right of the curve equaled Both stratigraphic sections analyzed here have thick inter- 0 and 95, respectively. This technique is commonly employed by vals characterized by frequent changes in community compo- ecologists to reduce curvilinear ordinations of various types (e.g., sition. Examples are: Pterochaenia-Eumetabolotoechia and Ludwig and Reynolds, 1988; Phillips, 1978), although typically Eumetabolotoechia communities in the lower part of Gulf with lower-order polynomials. Road; Eumetabolotoechia, Eumetabolotoechia-Ambocoelia, The correspondence ordination is interpreted as a general- Arcuaminetes-Eumetabolotoechia, and Arcuaminetes-Ambocoelia ized measure of relative depth and position along an ecological in the upper-middle part of Gulf Road; Arcuaminetes-Eumetab- gradient, as has been suggested in other studies, including Cisne olotoechia and Arcuaminetes-Ambocoelia communities in the and Rabe (1978), Brower and Kile (1988), and Brower et al. upper portion of Gulf Road; Eumetabolotoechia-Ambocoelia and (1988). Several facts indicate that this ordination does provide

CEPH -PTER 1 PTER -EUM EUM EUM-AMB Figure 11. Fourth-order polynomial S II 0 EMA fitted to axes I and II of the correspon- AXI dence analysis of 81 samples shown in ARC -EUM Figure 8A. The species codes are listed ARC -AMB in Table 1. -1 MUC -AMB

-2 -4 -3 -2 -1 01

AXIS I

such information. Scores for the samples on the ordination are dence axis ordination and depth is both generalized and blurred; highly correlated with sedimentary grain size and community the independent effects of depth, such as agitation and substrate composition, and they vary inversely with the organic matter texture, cannot be completely disentangled, although some sug- content. For example, the Spearman’s rank correlations between gestions are presented below. the correspondence ordination versus sedimentary grain size, The scores for the samples on the correspondence axis ordi- organic matter content, and community composition are 0.828, nation are plotted against stratigraphic position in Figure 12. For –0.732, and 0.964, respectively. In addition, there are associa- the purposes of interpretation, we will assume that depths and tions between the correspondence axis ordination and increas- scores exhibit a linear relationship. The first-order pattern in both ing amounts of sedimentary bed thickness, bioturbation, density stratigraphic sections is regression or relative fall of sea level. of fossils, and taxonomic and ecological diversity, although the The rapid increase in the scores at the base of the Gulf Road exact correlations have not been calculated. High ordination section, especially involving the Cephalopod-Pterochaenia, scores in this analysis were linked with comparatively shallow Pterochaenia-Eumetabolotoechia, and perhaps the Eumetabo- water, high agitation, coarse substrates, and high oxygen con- lotoechia communities, suggests rapid shoaling and augmented tents, and vice versa. The correlation between the correspon- oxygenation. Later rates of falling sea level at Gulf Road are

SWAMP ROAD

CEPH -PTER PTER -EUM ER EUM Figure 12. Plot of correspondence anal- EUM-AMB NUMB ysis ordination for the two sections. The EMA samples are designated by the community types discussed in the text. Strati- ARC -EUM graphic locations of samples are given SAMPLE ARC -AMB in Figures 3 and 4. The species codes are listed in Table 1. MUC -AMB

GULF ROAD

ORDINATION SCORES

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more gradual and exhibit several smaller-scale transgressions and Although much less common, the distribution and some morpho- regressions superimposed on the overall trend. logical features of Buchiola retrostriata parallel those of Ptero- The base of the Swamp Road outcrop began in deeper water chaenia fragilis, and their living habits are considered to be the than that seen in the youngest beds at Gulf Road. Consequently, same. “Praecardium” robusta, a rare element in many Cardiff the range of depths spanned by the two sections overlaps consid- Member communities, is a large (up to 60 mm long) bivalve that erably. The Swamp Road area is characterized by a decrease in was probably epifaunal and may have been epibyssate. Although relative sea level that appears almost linear. The superimposed “Praecardium” often occurs in deeper-water, fine-grained facies, fluctuations of scores for the correspondence axis ordination are its large size is not typical of most epipelagic taxa. The asym- minor, and they may or may not be statistically significant. The metric valves suggest that this bivalve did not have the swimming Mucrospirifer-Ambocoelia community caps the Swamp Road capacity characteristic of some modem pectinaceans in compara- section, which ended in shallower habitats than did the older sec- ble habitats (cf. Stanley, 1972). We therefore conclude that most tion at Gulf Road. individuals of Praecardium likely dwelled epifaunally, but some specimens may have been epipelagic. COMMUNITY COMPOSITION AND Shell shapes and apertural orientations of the gastropods ECOLOGICAL STRUCTURE and bellerophontids in the Cardiff Member demonstrate that these animals dwelled epifaunally on the sedimentary substrate Ecological groups within the eight Cardiff Member commu- or on plants (e.g., Linsley, 1977). Their food supplies are uncer- nities will be discussed in order of decreasing depth. The living tain. Recent shallow-water counterparts graze on benthic algae, habits of the shelled organisms are divided into ecological cat- whereas those dwelling in aphotic regions are deposit feeders egories that represent a combination of feeding habits and mode (Rex, 1973). Inasmuch as stratigraphic position and lithology of locomotion or attachment. The nine categories are: indicate that these sediments were deposited at moderate depths, (1) pedicle-attached suspension feeders; the Cardiff Member gastropods are tentatively considered to have (2) reclining suspension feeders in which the shell may lie at, been herbivores. The bellerophontids—extinct molluscs thought or slightly above, the substrate; by some to have been gastropods and by others possibly to have (3) epibyssate or very shallow endobyssate suspension feeders; been monoplacophorans (this latter grouping is, however, itself (4) endobyssate suspension feeders; considered polyphyletic)—are here classified as herbivores as (5) burrowing suspension feeders that are probably mostly well. Following Bouchet et al. (2005, 2017), we consider bel- sedentary (rather than active) burrowers; lerophontids as incertae sedis within Class Gastropoda for now. (6) burrowing deposit feeders; (7) grazers that crawl along the surface; Cephalopod-Pterochaenia Community (8) a highly variable suite of “collectors,” which includes mainly bottom plowers, crawlers, or walkers, some of This community occurs only in the organic-rich, deep-water which may have been capable of swimming or burrow- shales of the Gulf Road section (Fig. 3). Both species richness ing; the organisms denoted as “collectors” may have and ecological diversity are low, with means of 5.22 species and been deposit feeders, scavengers, or predators on small 3.56 ecological categories, respectively (Table 2). Surprisingly, animals and plants; and equitabilities are comparatively high, with a more even distribu- (9) swimming predators and scavengers. tion of species frequencies and ecological categories than in any Reconstruction of living habits for most species is straight- other Cardiff Member community. The assemblage is dominated forward, and it was based mainly on references listed previously. by pelagic cephalopods. Among the most common bivalves, Several forms do require additional explanation. The shape of Pterochaenia fragilis is tentatively interpreted as either epipe- the small and thin-shelled bivalve Pterochaenia fragilis defi- lagic or more likely epibyssate. Eumetabolotoechia multicostata, nitely denotes the presence of a byssus (Stanley, 1972), but the a pedunculate rhynchonellid that also occurs in samples from site of byssal attachment is uncertain. This bivalve spans a wide the upper stratigraphic range of this community,2 commonly variety of facies, from laminated black shales and limestones to forms dense accumulations in dark-gray shales stratigraphically siltstones. The species may be extremely abundant in dark-gray higher in the sections, and it is likely that individuals of this spe- shales, where some specimens are preserved in inferred living cies were moored to the substrate. The presence of pedicle bor- position; such occurrences are interpreted as representing organ- ings on valves further demonstrates that some individuals were isms attached to the seafloor.Pterochaenia fragilis is a common attached to other individuals of multicostata (see also discussions accessory in various level-bottom Hamilton Group communities, of the ecology of this brachiopod genus in Thompson and New- a distribution consistent with a benthic habit. A few shells were ton [1987] and Boyer and Droser [2009]). Epipelagic specimens obtained from laminated black shales, where they are associated of Eumetabolotoechia multicostata are not known. We thus infer with pelagic faunas. These could represent epipelagic organisms, as suggested by Thayer (1974) for Upper Devonian material (see also discussion in Boyer and Droser [2009] on such organisms). 2Formerly known as Leiorhynchus, this taxonomy was revised by Paul Sartenaer.

that Eumetabolotoechia multicostata and Pterochaenia fragi- of dark-gray shale are densely covered with this assemblage, lis were epibenthic rather than epipelagic. If our interpretation whereas other bedding surfaces are almost barren, a pattern we is correct, the Cephalopod-Pterochaenia community reflects a interpret as reflecting opportunistic settlement behavior. Pedicle- mixed pelagic-benthic fauna. attached brachiopods, especially Eumetabolotoechia multicostata and small numbers of Emanuella subumbona, form 77% Pterochaenia-Eumetabolotoechia Community of the fauna. Other accessory taxa, at levels of 6% to 7% each, include epibyssate bivalves (mainly Pterochaenia fragilis), Although many taxa in this community occur in the lower reclining brachiopods such as Arcuaminetes scitulus (formerly Cephalopod-Pterochaenia assemblage discussed above, the fre- Devonochonetes scitulus) and Spinulicosta spinulicosta, and quency of cephalopods is much lower (~2.16%, or an order of deposit-feeding nuculoids. Nuculoidea sp., the most common magnitude lower than that of the underlying Cephalopod-Ptero- burrowing deposit feeder, was a shallow-burrowing, asiphonate chaenia community; Table 2). Many benthic species in this com- bivalve. Other ecological categories are either sparsely repre- munity also occur in the deeper-water Cephalopod-Pterochaenia sented or unrepresented. Species richness and ecological diver- community; the most common of these are pedunculate brachio- sity continue to be comparatively low, with means of 8.79 species pods (Eumetabolotoechia multicostata and a few specimens of and 5.21 ecological categories, respectively. The dominance of a Emanuella subumbona) and epibyssate bivalves, most notably few pedicle-attached suspension feeders results in an equitability Pterochaenia fragilis. These two ecological categories taken that is the lowest of all eight communities in the data set. together account for over 90% of the individuals in this com- The Eumetabolotoechia community is usually underlain by, munity. Minor frequencies of infaunal deposit-feeding bivalves and often succeeded by, the Pterochaenia-Eumetabolotoechia (Nuculoidea sp.) and reclining brachiopods represent the lowest community. In fact, most taxa in the Eumetabolotoechia com- stratigraphic occurrences of these groups in our study. Most of munity were already present in the Pterochaenia-Eumetab- the sediments associated with this community show some traces olotoechia fauna; the community transition mostly involves of bioturbation (usually small, well-defined, horizontal burrows) changes in the frequencies of these fossils (e.g., Figs. 5 and 8). of 1.5–2.0 mm diameter, implying that the bottom waters were The Eumetabolotoechia community occurs in distinctly coarser at least dysaerobic (and probably aerobic). Such burrows do not rocks with thicker beds, more bioturbation, and slightly lower occur in the Cephalopod-Pterochaenia community. The introduc- organic content (Figs. 3, 4, and 10). These interrelated changes tion of new species and ecological categories in the Pterochae- suggest a pattern of decreasing depth, with an associated increase nia-Eumetabolotoechia fauna augments species richness and in agitation and a shift toward firmer substrates. ecological diversity considerably, with means of 8.33 species and 5.0 ecological types per sample. This greater diversity suggests Eumetabolotoechia-Ambocoelia Community a shift in environmental conditions relative to those of the mixed pelagic-benthic Cephalopod-Pterochaenia community. Because This assemblage represents a higher species richness com- of the dominance of pedicle-attached and epibyssate suspension munity closely related to the Eumetabolotoechia community feeders, the equitability of the Pterochaenia-Eumetabolotoechia (Table 2), as is documented by the multivariate analyses discussed community is less than that of most of the other assemblages. above (Figs. 5 and 8) and by recurring stratigraphic juxtapositions The Pterochaenia-Eumetabolotoechia community likely of these two assemblages. The Eumetabolotoechia-Ambocoelia reflects a pioneer fauna developed as the substrate initially community invariably succeeds the Eumetabolotoechia commu- became favorable for benthic settlement. The grain size of sedi- nity stratigraphically (Figs. 3, 4, and 10). Pedunculate brachio- ments associated with the Cephalopod-Pterochaenia and the pods, typically Eumetabolotoechia multicostata and Ambocoelia Pterochaenia-Eumetabolotoechia communities appears con- umbonata, account for nearly 60% of the fauna. This represents a stant, but the mean organic content declines slightly, from 3.0% significant decline from the 77% in the Eumetabolotoechia com- to 2.8%. The contrast between the Cephalopod-Pterochaenia munity. Reclining suspension feeders—Arcuaminetes scitulus and Pterochaenia-Eumetabolotoechia communities is consistent and a few individuals of Mucrospirifer mucronatus—constitute with a threshold or trigger effect, in which small environmen- 21% of the fauna, which is also significantly higher than in the tal changes may have catalyzed large ecological and taxonomic Eumetabolotoechia community. Burrowers, both deposit and shifts in faunal composition. One such environmental change suspension feeding, are also present. Deposit-feeding burrowers between these two communities may have been an increase in are represented by forms that lived at various depths. Nuculoi- oxygenation. dea sp. was a shallow burrower, whereas Nuculites oblongatus, which becomes common in this community for the first time, has Eumetabolotoechia Community a shell shape signaling the presence of siphons and a deeper burrow. Epibyssate bivalves decline to about 3%, a downshift caused The pedunculate brachiopod Eumetabolotoechia multico- by decreasing Pterochaenia fragilis. stata attains peak abundance in this community, where it con- High species richness values and ecological diversities stitutes nearly two thirds of the individuals (Table 2). Some beds appear for the first time in this community, averaging 11.9 and

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6.21 species and ecological categories, respectively. Likewise, and Eumetabolotoechia-Ambocoelia assemblages. Organic con- the equitabilities increase, as the Eumetabolotoechia-Ambocoelia tents are lower than in the sediments of the Eumetabolotoechia community consists of a greater number of taxa and ecological community, but they are comparable to those of the Eumetabo- categories than do the communities occurring stratigraphically lotoechia-Ambocoelia community. The inferred environmental lower in the sections. Sediments associated with this commu- changes include decreasing depth and increasing agitation. nity resemble those of the Eumetabolotoechia suite, except that The abundance of the small reclining brachiopod Arcua- organics are sparser, with an average of 2.4 wt%, as compared minetes scitulus deserves special note. Small recliners such as with 2.7 wt%. We infer that the Eumetabolotoechia-Ambocoelia Arcuaminetes scitulus are often considered characteristic of soft assemblage reflects a more agitated, and possibly slightly more soupy substrates in quiet water. In fact, suspension-feeding bra- oxygenated, habitat than the underlying Eumetabolotoechia and chiopods require some water movement to provide fresh food other communities. and oxygen and to remove wastes. The chonetid shell must have lain close to the substrate and the boundary layer between the Emanuella Community substrate and seawater. Current velocity decreases exponentially as the seafloor is approached. Consequently, a certain minimal Multivariate analyses demonstrate that this peculiar commu- amount of agitation is required to enable these small reclining nity relates most closely to the Eumetabolotoechia fauna. These animals to survive. This is wholly consistent with the distribution communities are associated, and they share similar ecological of these small reclining taxa in the Cardiff Member communi- roles, species, diversity, and equitability (Figs. 3, 4, and 10; Table ties. Arcuaminetes scitulus is either completely absent or rare in 2). Pedicle-attached suspension feeders dominate, but Emanu- the deepest and quietest water benthic communities (Pterochae- ella subumbona is much more abundant than Eumetabolotoechia nia-Eumetabolotoechia and Eumetabolotoechia). The species multicostata. Compared to the Eumetabolotoechia commu- appears only after a critical amount of agitation is reached. nity, reclining brachiopods—mostly Arcuaminetes scitulus and Mucrospirifer mucronatus—are more frequent, but burrowing Arcuaminetes-Ambocoelia Community deposit feeders and epibyssate bivalves are rarer. The Emanu- ella community is associated with silty shales, in contrast to the This fauna is closely linked to, and is interbedded with, the Eumetabolotoechia community, which occurs in shales. Organic Arcuaminetes-Eumetabolotoechia and Mucrospirifer-Ambocoelia content is slightly less abundant than in the rocks of the Eume- communities (Figs. 3–5, 8, and 10). Reclining suspension feed- tabolotoechia community. These lithologic differences suggest ers, mostly Arcuaminetes scitulus, along with some shells of that the Emanuella community occupied a slightly shallower and Mucrospirifer mucronatus and Spinulicosta spinulicosta, lead more agitated habitat than the Eumetabolotoechia community. the roster of ecological categories and represent 58% of the individuals (Table 2). Next are pedunculate brachiopods, largely Arcuaminetes-Eumetabolotoechia Community Ambocoelia umbonata with rare Emanuella subumbona, which comprise 21% of the assemblage. Burrowing deposit feed- The statistical data and stratigraphic distribution indicate that ers are diverse, but they are slightly less abundant than in the this community most closely resembles the Eumetabolotoechia- Arcuaminetes-Eumetabolotoechia community. The small cohort Ambocoelia fauna (Figs. 3, 4, 5, 8, and 10). Samples of the Arcu- of burrowing suspension feeders includes forms that occur also aminetes-Eumetabolotoechia community are usually underlain in the deeper-water communities. Species richness values and by the Eumetabolotoechia, Eumetabolotoechia-Ambocoelia, or ecological diversities of the Arcuaminetes-Ambocoelia commu- Arcuaminetes-Ambocoelia assemblages, although in one part nity slightly exceed those of Arcuaminetes-Eumetabolotoechia, of the Gulf Road section, the Arcuaminetes-Eumetabolotoechia but the relatively high abundance of a few reclining suspension fauna follows that of Emanuella. Reclining brachiopods, espe- feeders leads to lower equitabilities in this assemblage. Litholo- cially the ubiquitous Arcuaminetes scitulus, along with some gies associated with the Arcuaminetes-Ambocoelia community Mucrospirifer mucronatus, make up 43% of the assemblage are shaly siltstones and silty shales that are coarser, thicker bed- (Table 2). Pedunculate brachiopods—Eumetabolotoechia mul- ded, and more highly bioturbated than those of the Arcuami- ticostata, Ambocoelia umbonata, and Emanuella subumbona netes-Eumetabolotoechia fauna. Organic contents of the three (in decreasing order)—constitute 37% of the individuals. About relatively shallow-water communities in the Cardiff Member are 10% of the fauna consists of the deposit-feeding bivalves Nucu- quite similar. Thus, the Arcuaminetes-Ambocoelia assemblage loidea sp. and Nuculites oblongatus. Burrowing suspension feed- almost certainly occupied shallower, higher-energy habitats than ers, notably lingulids, are consistent accessories in most samples the Arcuaminetes-Eumetabolotoechia community. in this community. Taxonomic and ecological diversity exceed those of the Eume- Mucrospirifer-Ambocoelia Community tabolotoechia-Ambocoelia assemblage. The Arcuaminetes-Eume- tabolotoechia fauna occurs in gray shale and silty shales that are This group of organisms occurs in the coarsest sediments generally coarser than those of the associated Eumetabolotoechia in the study—silty shales to siltstones—and represents the most

shallow-water fauna present (Figs. 3 and 4). However, the lithol- minetes-Eumetabolotoechia, Arcuaminetes-Ambocoelia, ogies and sedimentary structures indicate gentle to moderate and Mucrospirifer-Ambocoelia communities. Pedicle- (rather than high) amounts of wave and current agitation below attached and reclining suspension feeders form the trophic normal wave base. core for all of these assemblages. Maximum taxonomic Reclining brachiopods (45%) and pedunculate brachiopods and ecological diversities are observed in these faunas. (37%) form the trophic nucleus of this community (Table 2). The A matrix of correlation coefficients among the nine ecologi- most common taxa in this assemblage, e.g., Ambocoelia umbo- cal roles was calculated for 72 samples from the seven benthic nata, Mucrospirifer mucronatus, and Arcuaminetes scitulus (in communities (Table 4). The magnitudes for the correlations that decreasing order of abundance), are also known from the closely differ significantly from a population value of nil, i.e., no cor- associated Arcuaminetes-Eumetabolotoechia and Arcuaminetes- relation at all, equal 0.232 and 0.302 at the 0.05 and 0.01 prob- Ambocoelia communities (Figs. 5, 8, and 10). The large spiriferid ability levels. Most (53%) of the observed correlations are not Spinocyrtia granulosa is a common accessory in this fauna; this statistically significant. The correlation with the highest magni- is the lowermost stratigraphic occurrence of significant numbers tude is –0.906 for the pedicle-attached versus reclining suspen- of Spinocyrtia granulosa. Burrowing deposit feeders continue sion feeders. Thus, these two categories are inversely related, as to decline, a trend probably correlated with the higher agitation would be expected from the composition of the communities. and lower amounts of organic matter. Large epibyssate bivalves, Many Cardiff Member recliners—particularly common groups such as Actinopteria boydi, Cornellites fasciculata, Gosseletia such as chonetids—had relatively low profiles with respect to the triquetra, and Leiopteria sp., and endobyssate clams such as sediment. Therefore, these animals could not become well estab- Goniophora hamiltonensis, Grammysia bisulcata, and Modio- lished until critical amounts of gentle agitation were attained, in morpha spp., show increased abundance. Maximum diversities— order to supply them with food and oxygen and to remove waste both taxonomic and ecologic—are attained in some samples of materials from near the substrate. Most pedicle-attached brachio- the Arcuaminetes-Ambocoelia and Mucrospirifer-Ambocoelia pods filtered water higher above the substrate, where more water faunas. However, taxonomic and ecological evenness are higher movement would have been available in the quieter habitats. In in the Mucrospirifer-Ambocoelia community. addition, the fine sediments of the deeper communities could easily have fouled the shells of small recliners such as Arcuami- Cluster Analysis of Trophic Structures netes scitulus. The correlation coefficient with the next highest magnitude, a value of 0.469 between reclining filter feeders and Taxonomic and ecological structures of the communities are surface grazers, reflects mainly the rarity of both groups in the highly correlated, as is strongly indicated in the cluster analysis of finest sediments of the Cardiff Member. Here, one category only the 81 samples for the nine ecological categories (Fig. 13). This explains 22% of the variance of the other (i.e., correlation coef- dendrogram derives from the unweighted-pair-group method ficient squared). Therefore, except for the pedicle-attached and on a matrix of correlation coefficients. The communities can be reclining brachiopods, the various ecological categories seem to divided into four major types with respect to the ecological data: be basically independent of each other, as would be predicted (1) Samples 1–9 belong to the Cephalopod-Pterochaenia from diversity theory. community, characterized by a very low species richness Correlations between the taxonomic and ecological diversi- and mixed pelagic-benthic assemblage. ties and between the taxonomic and ecological equitability are (2) The Pterochaenia-Eumetabolotoechia community includes all high; these range from 0.808 to 0.858 (Fig. 14). Thus, these samples 10, 12, and 13. This is a low-species-richness pio- pairs of parameters consistently track one another, as can be neer fauna that mostly includes pedicle-attached brachio- inferred from the annotations on the communities. Equitabilities pods and small epibyssate bivalves. These organisms seem in our samples are largely independent of the diversities, and vice to appear as soon as the seafloor becomes generally suitable versa. Contrary to popular belief, communities with low species for occupation by bottom dwellers. richness may have taxa that are evenly distributed; they are not (3) The samples ranging from numbers 11 to 55 on the necessarily dominated by a single species. To some extent, the dendrogram are mostly from the Ambocoelia and the converse is also true for the Cardiff Member data. For example, Emanuella communities. All of these samples are domi- the Arcuaminetes-Ambocoelia community is rich in taxa, yet nated by pedicle-attached brachiopods. Species richness Arcuaminetes scitulus makes up almost half of the individuals. values and equitabilities range from low to moderate. Within this large group, the samples within the Eume- SUMMARY OF VERTICAL ECOLOGIC AND tabolotoechia community tend to separate from those TAXONOMIC CHANGES of the Eumetabolotoechia-Ambocoelia and Emanuella communities, which are more diverse, both ecologically Progressive changes in communities of the lower Hamilton and taxonomically. Group can be summarized by tracing various paleoecological (4) A large cluster extends from samples 27 to 29 on the parameters from the base to the top of the stratigraphic succes- dendrogram. These samples are grouped in the Arcua- sions. These parameters include species richness and equitability,

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CORRELATIONCOEFFICIENT

29 80 67 65 66 68 64 28 60 71 70 59 79 81 75 73 61 40 56 54 57 62 32 44 69 42 33 30 77 58 74 72 43 78 76 27 55 63 49 53 48 47 41 39 52 35 34 36 31 46 38 51 50 26 25 45 18 16 37 23 24 22 20 21 17 15 14 19 11 12 13 10 9 8 7 6 5 4 2 3 1 Figure 13. Dendrogram for 81 samples. The data matrix consists of percentages of the nine ecological categories in each sample. The clusters were extracted by the unweighted-pair-group method on a matrix of correlation coefficients. Stratigraphic locations of samples are given in Figures 3 and 4.

taxonomic composition, ecological roles, and correspondence analysis ordination scores (the last parameter providing an indi- engers eeders v rect measure of changes in paleodepth of the communities). eeders ies eeders eeders eeders Species Richness and Equitability eeders As expected from the previous discussion of the communities, both taxonomic richness and ecological diversity increase with progressively younger beds in both stratigraphic sections Ecological categor yssate suspension f wing suspension f wing deposit f

yssate suspension f (Fig. 15). The stratigraphically highest samples at Swamp Road ace grazers

edicle-attached suspension f (including portions of the Mucrospirifer-Ambocoelia and Arcu- Reclining suspension f Endob P Swimming predators and sca Surf Collectors Epib Burro Burro aminetes-Ambocoelia communities) exhibit slightly lower spe- 2. 4. 1. 9. 7. 8. 3. 5. 6. cies richness values, representing a slight reversal of the overall trend of increasing species richness in the sections. For both sec- 1.000 0.105 0.253 tions, species richness and ecological diversity are highly cor- –0.053 –0.126 –0.042 –0.314 –0.139 –0.285 related. The overall environmental changes of decreased depth TEGORIES Y 0.027 0.222 1.000 0.139 0.291 –0.210 –0.094 –0.083 IT RS GORIE S 0.253 0.469 1.000 0.349 –0.460 –0.240 –0.052 TE GORIES TE XONOMIC DIVERSITY TA 0.142 0.079 1.000 IES –0.266 –0.276 –0.026 OGICAL CA ION ION ECOLOGICAL DIVE S SPEC ECOL IE 0.290 0.113 1.000 FOR FOR –0.386 –0.190 TION COEFFICIENTS FOR ECOLOGICAL CA TY TY ION FUNCT ION FUNCT ABILI ABILI 0.281 1.000 –0.258 –0.171 NUMBER OF SPEC NUMBER OF ECOLOGICAL CA INFORMAT INFORMAT EQUIT 1.0 EQUIT TRIX OF CORRELA 34 56789 MA 0.117 1.000 T –0.445 0.8 ABLE 4. T

2 0.6 1.000 –0.906 ION COEFFICIEN 0.4 1.000

0.2 CORRELAT ie s1

0.0 Figure 14. Dendrogram for diversities and equitabilities for taxonomic and ecological categories. The algorithm used is the unweighted-pair-group Ecological categor method of a matrix of correlation coefficients.

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SWAMP ROAD

CEPH -PTER PTER -EUM

BER EUM EUM- AMB NUM EMA ARC -EUM

SAMPLE ARC -AMB MUC -AMB

GULF ROAD

A NUMBER OF SPECIES IN ASAMPLE

SWAMP ROAD Figure 15. Plots of taxonomic and ecological diversity for the two sections. (A) Species richness per sample; (B) number of ecological categories per sample. Both figures show increases upward at Swamp Road. The samples are designated by the community types discussed in the text. Stratigraphic locations of samples are given in Figures 3 and 4. The species CEPH -PTER codes are listed in Table 1. PTER -EUM

BER EUM EUM-AMB NUM EMA ARC -EUM

SAMPLE EUM -AMB MUC -AMB

GULF ROAD

B NUMBER OF ECOLOGIC CATEGORIES

and increased sedimentary grain size, agitation, and oxygenation (1) Swimming predators abound in the Cephalopod-Ptero- favor greater diversities. chaenia community at the base of the Gulf Road section, Equitabilities are more independent of stratigraphic posi- but frequencies of nektonic predators decline sharply in tion. The most evenly distributed communities are those of Ceph- all other communities. alopod-Pterochaenia, with low species richness and ecological (2) Following establishment of benthic faunas, the domi- diversity, and Arcuaminetes-Eumetabolotoechia, with higher nant ecological categories vary among three groups of species richness and higher ecological diversity. The Eume- epifaunal suspension feeders. In the deepest waters, tabolotoechia fauna, highly dominated by the pedicle-attached small epibyssate bivalves, notably Pterochaenia, pre- brachiopod E. multicostata, yields the lowest equitabilities. dominate. Pedicle-attached brachiopods, especially Low equitabilities also characterize the Pterochaenia-Eumetab- Eumetabolotoechia multicostata, become most abun- olotoechia and Emanuella communities. This reflects the fact dant in the Eumetabolotoechia and associated fau- that these deep-water communities are basically pioneer epifaunal suites. Communities in shallower water exhibit an nal assemblages that developed when conditions first became inverse relation between reclining and pedicle-attached favorable for the establishment of benthic organisms. As depth brachiopods, in which recliners are most frequent in the decreased in both stratigraphic sections, the increased agitation shallowest sediments in the two sections. Higher agi- and oxygenation favored more numerous taxa and ecological cat- tation is apparently required to provide adequate water egories that exploited more resources. circulation close to the seafloor for small recliners such as Arcuaminetes scitulus. Taxonomic Composition (3) Benthic assemblages of deeper waters are predomi- nantly epifaunal. Burrowing deposit feeders commonly Vertical distributions of some of the dominant taxa appear appeared at shallow depths below the substrate in the in Figure 16. Several generalizations can be made. Virtually all Eumetabolotoechia community, and greater burrowing common Hamilton Group species are protean organisms with depths were penetrated when the Eumetabolotoechia- broad environmental tolerances, and they span many types of Ambocoelia and Arcuaminetes-Eumetabolotoechia com- communities. Some organisms are concentrated in one or sev- munities occupied the area. Burrowing deposit feeders eral assemblages—for example, orthocones, Emanuella subum- began to decline in shallower waters as sediments pro- bona, and Pterochaenia fragilis—but others range more widely, gressively had decreasing amounts of organic matter and such as Eumetabolotoechia multicostata, Arcuaminetes scitulus, coarser sediment grain sizes. Mucrospirifer mucronatus, and Ambocoelia umbonata. In some (4) Endobyssate and burrowing suspension feeders are not instances, species composition and abundance can fluctuate abundant. Both groups were most frequently collected widely between adjacent samples within a stratigraphic section, in the faunas of the shallower lithofacies, ranging from especially at transitions between different communities; however, Eumetabolotoechia-Ambocoelia to Arcuaminetes-Ambo- in most cases, less dramatic variation occurs during transitions. coelia for the burrowers and to Mucrospirifer-Ambocoe- On average, changes between communities explain more of the lia for the endobyssates. Peak abundances of burrowing variation in the data than changes within assemblages. and endobyssate suspension feeders coincided with the Among abundant species, Ambocoelia umbonata, Arcuami- decline of burrowing deposit feeders. netes scitulus, Eumetabolotoechia multicostata, Mucrospirifer (5) Surface-dwelling gastropods, believed to have grazed on mucronatus, and Pterochaenia fragilis seem controlled more by plants, occurred most commonly in comparatively shal- factors related to grain size than by organic content, even though low regions with diverse associated taxa. both parameters contribute significantly. Conversely, Nuculoidea (6) Surface collectors, such as trilobites and hyolithids, were sp. and large orthocones are more closely correlated with organic erratically distributed as minor accessories of varied com- content. This was expected for Nuculoidea because of its deposit- munities. Admittedly, this ecological category is highly feeding habits. Likewise, the orthocone frequency declines dras- variable, and a range of feeding habits is included—for tically from the Cephalopod-Pterochaenia community to the example, deposit feeding, scavenging, and predation. Pterochaenia-Eumetabolotoechia community. The distribution This trophic role accounts for no more than 1.0% of the of Emanuella must be influenced by parameters other than grain individuals in any community. size and organic content, based upon the regressions for these variables, which are not significant. TESTING PROPOSALS OF COMMUNITY STABILITY AND COORDINATED STASIS Ecological Roles Hamilton Group faunas are frequently cited as paradigmatic Ecological categories exhibit the following major system- of the pattern of long-term community stability termed coordi- atic vertical changes in the two stratigraphic sections (Figs. 17 nated stasis (Brett and Baird, 1995; Brett et al., 1996; Schopf, and 18): 1996), with several workers referring to these assemblages as the

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PTEROCHAENIA

CEPH -PTER PTER -EUM

BER SWAMP ROAD EUM EUM-AMB NUM EMA ARC -EUM

SAMPLE ARC -AMB MUC -AMB

GULF ROAD

Figure 16. Plots of taxonomic composition for the two sections. The samples PERCENT are designated by the community types discussed in the text. Stratigraphic locations of samples are given in Figures 3 ARCUAMINETES and 4. The species codes are listed in Table 1. (Continued on facing page).

CEPH -PTER PTER -EUM ER SWAMP ROAD EUM EUM-AMB NUMB EMA ARC -EUM

SAMPLE ARC -AMB MUC -AMB

GULF ROAD

-10 10

PERCENT

“type” example of coordinated stasis. However, this intriguing McKinney et al., 1996; Ivany, 1999), let alone within the faunas proposal—that some marine evolutionary ecological units (EEUs of the lower Hamilton Group. of Boucot [1983] and Sheehan [1996]) exhibit long-term stabil- This study provides both documentation and analysis of ity on a scale of millions of years—has been discussed more paleoecological structure and taxonomic composition for the far widely than it has actually been tested, even now. Presence- lower Hamilton Group—an interval necessary for rigorous tests absence data and taxonomic ranges of common taxa do not suf- of whether the communities themselves, rather than just the taxa, fice to demonstrate coordinated stasis (McKinney et al., 1996; range through this entire stratigraphic unit and the time it encom- Schopf and Ivany, 1997). Instead, quantitative analysis of large passes. It provides a first detailed look at community stability samples distributed over a significant temporal interval must be in this lower interval, integrating taxa that are moderately rare undertaken (see also Bennington and Bambach, 1996). In par- (>1% of the fauna). Taken together with the few other quantita- ticular, the stability of rare taxa (and their variability) has not tive Hamilton Group studies (e.g., Savarese et al., 1986; Brower previously been explored adequately in general (Boucot, 1996; et al., 1988; Brower and Nye, 1991; McCollum, 1991; Bonuso,

NUCULOIDEA

CEPH -PTER PTER -EUM

BER SWAMP ROAD EUM EUM-AMB NUM EMA ARC -EUM

SAMPLE ARC -AMB MUC -AMB

GULF ROAD

PERCENT Figure 16. (Continued).

MUCROSPIRIFER

CEPH -PTER PTER -EUM

BER SWAMP ROAD EUM EUM-AMB NUM EMA ARC -EUM

SAMPLE ARC -AMB MUC -AMB

GULF ROAD

PERCENT

2001; Bonuso et al., 2002a, 2002b), we can make some initial taxa within these other associations are known from higher in inferences about the structure and temporal persistence of Ham- the Hamilton Group, and hence range through (Brett and Baird, ilton Group marine communities. 1995), but the internal structure of later associations, as described Our data reveal a few—but not all—lower Hamilton Group in Savarese et al. (1986) and McCollum (1991), is incongruent communities with counterparts in upper Hamilton Group faunas. with that of our communities. This means that stability is indicated for some associations but In coordinated stasis, and particularly in the ecological not others. For instance, the Arcuaminetes-Ambocoelia commu- locking model, these communities should recur temporally and nity and the Eumetabolotoechia community apparently occur higher in the Hamilton Group, as described by other workers (cf. Savarese et al., 1986; McCollum, 1991)3. However, the other 3Zambito et al. (2012) lumped different “chonetids” and “leiorhynchids” together and excluded rare taxa, so some further work will be necessary to dem- six communities we recognized herein do not clearly recur with onstrate which of their EEUs parallel those we describe quantitatively and eco- the same array of taxa in other studies. Abundant and common logically here.

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SWIMMING PREDATORSAND SCAVENGERS

CEPH -PTER PTER -EUM ER SWAMP ROAD EUM EUM-AMB NUMB EMA ARC -EUM

SAMPLE ARC -AMB MUC -AMB

GULF ROAD

Figure 17. Plots of ecological catego- PERCENT ries for the two sections. The samples are designated by the community types discussed in the text. Stratigraphic locations of samples are given in Figures 3 BURROWING DEPOSIT FEEDERS and 4. The species codes are listed in Table 1. (Continued on facing page).

CEPH -PTER PTER -EUM

BER SWAMP ROAD EUM EUM-AMB NUM EMA ARC -EUM

SAMPLE ARC -AMB MUC -AMB

GULF ROAD

PERCENT

should prove statistically similar throughout the temporal inter- structure, but rather were fluid with species and genera moving in val. As Ivany has pointed out, frequencies of taxa may vary, but and out of communities in response to local changes in environ- the associations ought to recur. This pattern would be predicted mental conditions.” Further rigorous quantitative studies of upper in both the environmental tracking and ecologic locking mod- Hamilton Group faunas should reveal whether, as in the Ordovi- els—and it would especially be an integral prediction of ecologic cian study, loosely integrated communities characterize the dura- locking. Our information from the lower Hamilton Group sug- tion of Hamilton Group deposition. gests that this is not supported by currently available data. In that Our study also yielded several quantitative results for the regard, the Hamilton faunas may resemble those documented lower Hamilton Group that, in themselves, pose further ques- by Patzkowsky and Holland (1999, p. 301) from the Middle to tions for the hypothesis of ecological locking. First, these Mar- Upper Ordovician of the Nashville Dome. Their results indicate cellus Subgroup communities exhibit low levels of integration that Ordovician communities “were not tightly integrated in their and correlation among the constituent species, in contrast to the

PEDICLE-ATTACHED SUSPENSION FEEDERS

CEPH -PTER PTER -EUM

BER SWAMP ROAD EUM EUM-AMB NUM EMA ARC-EUM

SAMPLE ARC-AMB MUC -AMB

GULF ROAD

PERCENT Figure 17. (Continued).

RECLINING SUSPENSION FEEDERS

CEPH -PTER PTER -EUM ER SWAMP ROAD EUM EUM-AMB NUMB EMA ARC-EUM

SAMPLE ARC- AMB MUC -AMB

GULF ROAD

PERCENT

predictions of ecological locking. Second, rapid swings in the These conclusions resemble those reached by Tang and abundance of taxa occur in adjacent beds, with no apparent cor- Bottjer (1996), who inferred that Jurassic paleocommunities in responding shifts in lithology or other environmental indicators. western North America also fail to show evidence in support of Ecologic categories of lower Hamilton Group taxa in our study the ecological locking model. However, Tang and Bottjer’s con- show low correlations (53% of observed correlations are not sta- clusions came solely from presence-absence data or data on dom- tistically significant). In sum, the lower Hamilton Group faunas inant taxa; Schopf and Ivany (1997) therefore correctly pointed analyzed here reflect only loosely structured associations, even out that Tang and Bottjer had not conducted all the tests neces- though the individual communities are statistically discrete— sary to probe the question. Our study, with a far richer abundance results that seem not to suggest that the faunas are tightly inte- database, now reveals that with appropriate tests of Hamilton grated as has been predicted by some (but not all) coordinated Group faunas, 4–6 m.y. persistence of ecologically locked and stasis proponents. tightly structured communities is still not indicated.

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SHALLOW sink, J.R. Corbett, R. Fein, R. Hennigan, S.N. Hill, M.S. Mon- 100 MUCROSPIRIFER -AMBOCOELIA monier, and A. Stützle of Syracuse University, as well as the ARCUAMINETES-AMBOCOELIA GSA Books editorial staff, who lent expertise crucial to the completion of this research. ARCUAMINETES-EUMETABOLOTOECHIA 80 EUMETABOLOTOECHIA-AMBOCOELIA REFERENCES CITED EMANUELLA EUMETABOLOTOECHIA Bailey, J.B., 1983, Middle Devonian Bivalvia from the Solsville Member 60 (Marcellus Formation), central New York State: Bulletin of the American Museum of Natural History, v. 174, p. 193–325. PTEROCHAENIA -EUMETABOLOTOECHIA Baird, G.C., Brett, C.E., and Ver Straeten, C.A., 2000, Facies and fossils of the lower Hamilton Group in the Livingston County–Onondaga County 40 region, in McKinney, D.B., ed., New York State Geological Association 72nd Annual Meeting Field Trip Guidebook: Syracuse, New York, New

ORDINATION SCOR E York State Geological Association, p. 155–175. CEPHALOPOD -PTEROCHAENIA Baumiller, T.Z., Marinovic, J.C., Tuura, M.E., Damstra, E.S., and Miller, 20 D.J., 2010, Signs of boring predation on Middle Devonian hyolithids from the Michigan Basin: Palaios, v. 25, no. 10, p. 636–641, https://doi .org/10.2110/palo.2010.p10-044r. Bennington, J.B., and Bambach, R.K., 1996, Statistical testing for paleocom- 0 munity recurrence: Are similar fossil assemblages ever the same?: Palaeo- geography, Palaeoclimatology, Palaeoecology, v. 127, p. 107–133, https:// DEEP doi.org/10.1016/S0031-0182(96)00090-9. Birks, H.J.B., and Gordon, A.D., 1985, Numerical Methods in Quaternary Pol- Figure 18. Relative depth of Hamilton Group communities as indi- len Analysis: London, Academic Press, 317 p. cated by ordination results. Bizzarro, M., 1995, The Middle Devonian chonetoidean brachiopods from the Hamilton Group of New York, in Racheboeuf, P.R., ed., Four Contribu- tions to the Study of Chonetoidean Brachiopods: Documents des Labora- toires de Géologie de Lyon (France) 136, p. 149–189. Bonuso, N., 2001, Quantitative Paleoecology of the Hamilton Group of Central New York [M.S. thesis]: Syracuse, New York, Syracuse University, 96 p. ACKNOWLEDGMENTS Bonuso, N., Newton, C.R., Brower, J.C., and Ivany, L.C., 2002a, Does coordinated stasis yield taxonomic and ecologic stability? Middle Devonian Hamilton Group of central New York: Geology, v. 30, p. 1055–1058, Brower and Newton dedicate this paper to the honor and https://doi.org/10.1130/0091-7613(2002)030<1055:DCSYTA>2.0.CO;2. memory of John M. Dennison, M.S. advisor to Cathryn New- Bonuso, N., Newton, C.R., Brower, J.C., and Ivany, L.C., 2002b, Statistical testing of community patterns: Uppermost Hamilton Group, Middle ton and colleague of James Brower, and Willis B. Newman, Devonian (New York State, USA): Palaeogeography, Palaeoclimatology, our joint doctoral student, much respected and beloved, who Palaeoecology, v. 185, no. 1–2, p. 1–24, https://doi.org/10.1016/S0031 -0182(02)00298-5. conducted this fieldwork and analyses but did not complete Bouchet, P., Rocoi, J.-P., Fryda, J., Hausdorf, B., Ponder, W., Valdés, A., and the dissertation. Warén, A., 2005, Classification and nomenclator [sic] of Gastropod fami- Acknowledgment is made to the donors of the Petroleum lies: Malacologia, v. 47, no. 1–2, p. 1–397. Bouchet, P., Rocoi, J.-P., Hausdorf, B., Kaim, A., Kano, Y., Nützel, A., Research Fund of the American Chemical Society for sup- Parkhaev, P., Schrödl, M., and Strong, E.E., 2017, Revised classifica- port of this research program. We also gratefully acknowledge tion, nomenclator [sic], and typification of Gastropod and Monopla- a New York State Honorarium to W.B. Newman and ongoing cophoran families: Malacologia, v. 61, no. 1–2, p. 1–526, https://doi .org/10.4002/040.061.0201. research support to C.R. Newton from the Vice Chancellor and Boucot, A.J., 1983, Does evolution take place in an ecological vacuum? II: Provost of Academic Affairs at Syracuse University. Thanks are Journal of Paleontology, v. 57, no. 1, p. 1–30. due to G.C. Baird of the State University of New York at Fredo- Boucot, A.J., 1996, Epilogue: Palaeogeography, Palaeoclimatology, Palaeoecol- ogy, v. 127, p. 339–359, https://doi.org/10.1016/S0031-0182(97)81610-0. nia, C.E. Brett of the University of Cincinnati, T.X. Grasso of Bowen, Z.P., Rhoads, D.C., and McAlester, A.L., 1974, Marine benthic com- Monroe Community College, L.C. Ivany of Syracuse Univer- munities of the Upper Devonian in New York: Lethaia, v. 7, p. 93–120, sity, D. and R.M. Linsley of Colgate University, H.B. Rollins https://doi.org/10.1111/j.1502-3931.1974.tb00889.x. Boyer, D.L., and Droser, M.L., 2009, Palaeoecological patterns within the of the University of Pittsburgh, and B. Selleck of Colgate Uni- dysaerobic biofacies: Examples from Devonian black shales of New versity for assistance in the field and for helpful discussions and York state: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 276, scientific friendship over many years. Cathryn Newton offers p. 206–216, https://doi.org/10.1016/j.palaeo.2009.03.014. Brett, C.E., 1986, Dynamic Stratigraphy and Depositional Environments of the deep and lasting gratitude to Jim Brower, Bob Linsley, and Hamilton Group (Middle Devonian) in New York State, Part I: New York Bud Rollins for becoming tremendous mentors who showed State Museum Bulletin 457, 156 p. her how to invest in others. John Harper and an anonymous Brett, C.E., 2012, Coordinated stasis reconsidered: A perspective at fifteen years, in Talent, J.A., ed., Earth and Life: Global Biodiversity, Extinction reviewer suggested slight revisions that markedly improved the Intervals, and Biogeographic Perturbations through Time, Part I: Berlin, figures and paleontological and stratigraphic descriptions; K. Springer, p. 23–36, https://doi.org/10.1007/978-90-481-3428-1_2. Lee Avary further lent wisdom and knowledge to the revisions Brett, C.E., and Baird, G.C., 1985, Carbonate-shale cycles in the Middle Devo- nian of New York: An evaluation of models for the origin of limestones process—and friendship always. CRN also thanks her students, in terrigenous shelf sequences: Geology, v. 13, p. 324–327, https://doi. from whom she learned much. Special thanks go to G.K. Wis- org/10.1130/0091-7613(1985)13<324:CCITMD>2.0.CO;2.

Brett, C.E., and Baird, G.C., 1995, Coordinated stasis and evolutionary ecol- ecology: Geological Society of America Memoir 67, Part 2, p. 249–278, ogy of Silurian to Middle Devonian faunas in the Appalachian Basin, in https://doi.org/10.1130/MEM67V2-p249. Erwin, D.H., and Anstey, R.L., eds., New Approaches to Speciation in the Dray, S., Pelissier, R., Couteron, P., Fortin, M.-J., Legendre, P., Peres-Neto, Fossil Record: New York, Columbia University Press, p. 285–315. P.R., Bellier, E., Bivand, R., Blanchet, F.G., De Caceres, M., Dufour, Brett, C.E., Speyer, S.E., and Baird, G.C., 1986, Storm-generated sedimentary A.-B., Heegard, E., Jombart, T., Munoz, F., Oksanen, J., Thioulouse, J., units: Tempestite proximality and event stratification in the Middle Devo- and Wagner, H.H., 2012, Community ecology in the age of multivariate nian Hamilton Group of New York, in Brett, C.E., ed., Dynamic Stra- multiscale spatial analysis: Ecological Monographs, v. 82, no. 3, p. 257– tigraphy and Depositional Environments of the Hamilton Group (Middle 275, https://doi.org/10.1890/11-1183.1. 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