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Late Cambrian and earliest Ordovician trilobites, Timbered Hills and lower Arbuckle Groups, western Arbuckle Mountains, Murray County, Oklahoma
... Data for Oklahoma are derived from new fieldwork in the Slick Hills (Donovan, 1986) to the north of the Wichita Mountains, and from archival collections at the Oklahoma Museum of Natural History made by Stitt (1971b) in the Arbuckle Mountains. In the Slick Hills, three sections (KR1, KR2, and KR3) through the Honey Creek Formation were measured on the Kimbell Ranch around the flanks of Ring Top Mountain, Comanche County, Oklahoma, and were correlated physically by walking out a distinctive, resistant, meter-thick carbonate unit (see Westrop et al., 2010, fig. 1, for locality map and correlation of sections). ...
... 5, for a locality map showing the line of section; base of section is at 34°27 ′ 08 ′′ N, 97°15 ′ 41 ′′ W), and carbon and oxygen values are uncorrelated. Trilobite, agnostid, and rhynchonelliform The gray-shaded band shows the interval of extinction and faunal replacement at the base of the Sunwaptan Stage (Westrop and Cuggy, 1999), comprising the Irvingella "major" Zone and the lower Taenicephalus Zone (Parabolinoides Subzone of Stitt, 1971b). Par = Parabolinoides; shu = Taenicephalus "shumardi;" "Id." lirae = "Idahoia" lirae; Ir. "major" = Irvingella "major." ...
... Trilobite biostratigraphy.-The traditional trilobite zones used in the Furongian succession of Laurentia are based on genera, with subzones typically founded on species (e.g., Winston and Nicholls, 1967;Longacre, 1970;Stitt, 1971b;Westrop, 1986a). However, there has been a move towards higher resolution zones based on trilobite species in both the Cambrian (e.g., Ludvigsen, 1982;Pratt, 1992;Westrop, 1995) and in younger strata (e.g., Adrain et al., 2009Adrain et al., , 2014. ...
Successions in Oklahoma and Nevada record trilobite extinction and replacement near the Steptoean–Sunwaptan boundary in inner-shelf and outer-shelf settings, respectively. Prior to the extinctions, different trilobite biofacies occupied these environments, but faunas became similar in composition across the environmental gradient in the overlying I . “ major ” and Taenicephalus zones. Faunal changes in the outer shelf at the I . “ major ” Zone begin at a drowning unconformity that brought dark, laminated calcisiltite and silty lime mudstone above a subtidal carbonate succession. In contrast, Oklahoma shows facies continuity in a succession of tidally influenced bioclastic carbonates. Loss of genera and a dramatic abundance “spike” of Irvingella are features of the I . “ major ” Zone in both regions. Turnover of biofacies occurred in the succeeding Taenicephalus Zone, with both the inner and outer shelf dominated by Orygmaspis ( Parabolinoides ). Blooms of orthid brachiopods in shallow water settings are underappreciated signals of faunal change in the extinction interval. Although absent from the outer shelf in Nevada, orthids became abundant enough in Oklahoma to form shell beds in the lower Taenicephalus Zone, but became rare in overlying strata. Carbon isotope stratigraphy includes a modest positive δ ¹³ C excursion that peaks in the extinction interval at 1.4‰ (Oklahoma) and 2.2‰ (Nevada), which is congruent with previous reports from Utah and Wyoming. Although consistent with regional upwelling of dysoxic waters, the absence of sedimentary evidence for significant environmental change over much of the shelf is problematic. This suggests that physical environmental change acted primarily as a catalyst for cascading ecological and biogeographic effects.
... Cambrian trilobites of Oklahoma have been studied intensively for 70 years (e.g., Frederickson 1948Frederickson , 1949Stitt, 1971Stitt, , 1977Westrop et al., 2010), so it is surprising to discover an entirely new fauna in the succession. This fauna is of interest because it includes early representatives of two major clades (Ptychaspididae Raymond, 1924 andEurekiidae Hupé, 1953) that radiated in Laurentia during the Sunwaptan Stage. ...
... The Fort Sill Formation (lowest unit of the Arbuckle Group) succeeds the Honey Creek Formation and is composed of lime mudstone-wackestone (Stitt, 1971;Donovan and Ragland, 1986). Intraclastic rudstone is also present, and microbial buildups occur in the upper part of the formation (Stitt, 1971). ...
... The Fort Sill Formation (lowest unit of the Arbuckle Group) succeeds the Honey Creek Formation and is composed of lime mudstone-wackestone (Stitt, 1971;Donovan and Ragland, 1986). Intraclastic rudstone is also present, and microbial buildups occur in the upper part of the formation (Stitt, 1971). Quartz sand and glauconite are minor components, suggesting that the archipelago was largely flooded during deposition of the Fort Sill. ...
Non-technical summary
A newly discovered trilobite fauna from the Cambrian Honey Creek Formation marks a distinct interval that follows an extinction event. Dominated by the genus Monocheilus in association with Ptychaspis , it resembles faunas from Alberta, Canada, and the Upper Mississippi Valley region of the United States. Ptychaspis bullasa Lochman and Hu, 1959 is a species that has been reported widely in North America. However, restudy of various museum collections shows that the various occurrences record a set of more narrowly distributed species. The pattern of distribution is similar to groups of modern “pseudocryptic species” identified by a combination of genetic and anatomical data.
... Unfortunately, detailed biostratigraphic study of Cambrian and Ordovician faunas in this area has lagged behind sedimentological analysis of these deposits, owing to the sparsely fossiliferous character of most formations and very poor exposure of the carbonate-dominated units. Even the most productive intervals have been studied primarily in reconnaissance fashion, as compared to more thorough biostratigraphic syntheses in coeval deposits in western North America that form the basis of the refined biostratigraphic and chronostratigraphic frameworks (Fig. 3) currently used for Upper Cambrian and Lower Ordovician strata in Laurentian North America (Ross 1951;Hintze 1952;Grant 1965;Palmer 1965;Winston & Nicholls 1969;Longacre 1970; Stitt 1971Stitt , 1977Stitt , 1983Ludvigsen 1982;Westrop 1986;among others). This is particularly true for the Upper Cambrian outer shelf deposits of the Conococheague Formation and the slopeto-basin facies of the Frederick Formation. ...
... The highest beds of the underlying Elbrook Formation contain an upper Marjuman Crepicephalus Zone fauna, assigning them to the top of the underlying Sauk II Supersequence. The oldest faunas recovered from strata directly overlying the Big Springs Station Member assign those strata to the uppermost Steptoean Elvinia Zone (Wilson 1951(Wilson , 1952 (1971), Westrop (1986), and Miller et al. (2003); for Southern Laurentia from Palmer (1954), Longacre (1970), Stitt (1971Stitt ( , 1983 and Rasetti (1961). Iapetus slope faunas from Ludvigsen et al. (1989). ...
... Broad generic and species concepts in some studies in the mid-twentieth century (e.g. Grant 1965; Stitt 1971) resulted in extensive synonymy of these dokimocephalid genera and species. But more recent and focused studies have shown that at least some of the taxa consolidated in those investigations of thick stratigraphic intervals display consistent morphologic differences and have removed them from synonymy. ...
... TRILOBITES ATTRIBUTED to the eurekiid genus Corbinia Walcott, 1924, are geographically widespread over North America and are restricted to a narrow interval close to the top of the Cambrian. Corbinia apopsis Winston and Nicholls, 1967, is the eponymous species of the uppermost subzone of the Saukia Zone of the standard North American zonation (Winston and Nicholls, 1967;Longacre, 1970;Stitt, 1971). The base of this subzone is the base of the Ibexian Series (Ludvigsen and Westrop, 1985). ...
... intermedius Rasetti, and Apatokephaloides sp. (Figure 1) and that is correlative with the Eurekia apopsis Subzone of Oklahoma and Texas (Stitt, 1971(Stitt, , 1977Longacre, 1970). Two incomplete cranidia assigned to E. cf. ...
... -San Saba Member, Wilbers Formation, central Texas, Eurekia apopsis Subzone (Winston and Nicholls, 1967;Longacre, 1970). Signal Mountain Limestone, Arbuckle and Wichita mountains, Oklahoma, E. apopsis Subzone (Stitt, 1971(Stitt, , 1977. Lava Dam Member, Notch Peak Formation, western Utah, E. apopsis Subzone (Miller et al., 1982). ...
The type species of the eurekiid trilobite Corbinia Walcott, C. horatio Walcott, 1924, possesses very short palpebral lobes located opposite 2p glabellar lobe. The palpebral lobes of species of Eurekia Walcott and of Corbinia apopsis Winston and Nicholls, 1967, are considerably longer and located opposite 1p and 2p glabellar lobes. Corbinia is here restricted to the type species, and C. apopsis is assigned to Eurekia. Corbinia horatio occurs in the Basal Silty Member of the Survey Peak Formation of southern Alberta and appears to be confined to the lower part of the Eurekia apopsis Subzone of the Saukia Zone (basal Ibexian).
... By comparison, the trilobite faunas have been badly neglected; an unfortunate situation in view of the paramount importance of trilobites in biostratigraphic correlations of Upper Cambrian rocks in North America (Lochman and Wilson, 1958;Longacre, 1970;Stitt, 1971Stitt, , 1977. The thesis by Greggs (1962) remained unpublished, and the only other taxonomic works describing trilobites from southern Alberta are those of Walcott (1925) and Resser (1942). ...
... The remarkably broad distribution of the Irvingella-Comanchia assemblage has been commented upon by previous workers (Wilson and Frederickson, 1950) and more recent work confirms these earlier observations. Collections virtually identical to those from the Bison Creek Formation at Mount Murchison have been recorded by Stitt (1971;Text-fig. 16) from the Honey Creek Limestone of Oklahoma. From faunal lists and qualitative assessments of abundances published by various workers, this biofacies is also present in Texas (Wilson, 1949); Nevada-Utah (Palmer, 1965); Montana-Wyoming (Grant, 1965); Missouri (Kurtz, 1975) ( Wilson and Frederickson, 1950;Berg, 1953). ...
... Compared with the Irvingella-Comanchia Biofacies, the Parabolinoides Biofacies is of lower diversity, but has an equally broad geographic and environmental range -it is clearly present in the Reagan Sandstone and the Honey Creek Limestone of Oklahoma (Stitt, 1971(Stitt, , 1977Text-fig. 16) and similar collections appear to occur in Texas (Longacre, 1970), the Upper Mississippi Valley (Berg, 1953), Montana-Wyoming (Grant, 1965), Missouri (Kurtz, 1975) and, possibly, Utah (Taylor and Cook, 1976, fig. ...
... TRILOBITES of the family Missisquoiidae Hupé 1955 occur throughout Laurentian North America in a relatively narrow interval of what is now the latest Cambrian succession (e.g., Shaw 1951;Winston & Nicholls 1967;Stitt 1971Stitt , 1977Taylor & Halley 1974;Ludvigsen 1982;Fortey 1983;Westrop 1986;Dean 1989). Although widely distributed, both geographically and environmentally, missisquoiid trilobites have been assigned traditionally to a small number of species of Missisquoia Shaw 1951. ...
... Despite these revisions to the supraspecific systematics, the number of missisquoiid species reported from the Laurentian uppermost Cambrian strata remains low. Nowhere is this more obvious than in the classic succession of Oklahoma, which was collected in fine stratigraphic detail by Stitt (1971Stitt ( , 1977. Through an interval of 61 metres in the Joins Ranch section (JoR-1058-JoR-1257Stitt 1971), Stitt viewed Missisquoiidae as represented by only two species, Tangshanaspis depressa (Stitt 1971) and Parakoldinioidia stitti Fortey 1983 (= Missisquoia typicalis of Stitt). ...
... Nowhere is this more obvious than in the classic succession of Oklahoma, which was collected in fine stratigraphic detail by Stitt (1971Stitt ( , 1977. Through an interval of 61 metres in the Joins Ranch section (JoR-1058-JoR-1257Stitt 1971), Stitt viewed Missisquoiidae as represented by only two species, Tangshanaspis depressa (Stitt 1971) and Parakoldinioidia stitti Fortey 1983 (= Missisquoia typicalis of Stitt). The latter species has been recorded throughout Laurentia under the name, Missisquoia typicalis Shaw (e.g., Shaw 1951;Winston & Nicholls 1967;Stitt 1971Stitt , 1977Taylor & Halley 1974;Fortey et al.,1982;Westrop 1986;Dean 1989). ...
Missisquoiid trilobites are widespread in Laurentian North America but most occurrences have been reported under a single name, Missisquoia typicalis Shaw 1951 (now = Parakoldinioidia stitti Fortey 1983). The base of the Parakoldinioidia Zone (= Missisquoia typicalis Subzone of older publications) is usually defined by the first appearance of the eponymous genus. In central Texas, the type area of the zone, three species have been recorded, and only one species is reported from correlative strata in Oklahoma. Restudy of archival collections from southern Oklahoma made by J.H. Stitt, as well as type and figured material from Texas and western Canada, revealed unexpected diversity of missisquoiid species. Our revision shows that there are at minimum ten species of Parakoldinioidia and three species of Lunacrania recorded in the uppermost Furongian successions of the southern Midcontinent and the southern Canadian Rocky Mountains. This indicates that Missisquoiidae underwent a significant radiation following the extinction interval at the base of the Eurekia apopsis Zone. It also demonstrates the potential for a high-resolution species based zonation of at least regional utility. New species are Parakoldinioidia akerfeldti, P. lindgreni, P. mendezi, P. lopezi and P. akessoni; three additional new species are placed in open nomenclature.
... Rusconi (1954a) and Borrello (1965Borrello ( , 1971) called attention to the general resemblance between the "Hungaia puelchana fauna" from the Quebrada Oblicua and that from upper Cambrian boulders of the Lower Ordovician Levis Formation in Quebec (Rasetti 1944). Certainly, the trilobites described in the present paper are comparable with carbonate shelf margin trilobites of Quebec (Billings 1860(Billings , 1865Rasetti 1944Rasetti , 1945Rasetti , 1963, western Newfoundland (Kindle & Whittington 1958;Kindle 1982;James & Stevens 1986;Ludvigsen et al. 1989), Vermont (Raymond 1924(Raymond , 1937Gilman Clark & Shaw 1968), and the Central Appalachians (Rasetti 1959); with deep-water trilobites of Alaska (Kobayashi 1935;Palmer 1968) and the northern Mackenzie Mountains, northwestern Canada (Westrop 1995); and with shelf faunas from Alberta, Montana-Wyoming, Texas and Oklahoma (Bell & Ellinwood 1962;Grant 1965;Stitt 1971;Westrop 1986). Ludvigsen et al. (1989) described in great detail the Furongian trilobites from limestone boulders of the Shallow Bay Formation (Cow Head Group) of western Newfoundland, and provided a complete shelf margin biostratigraphy that is applicable to other regions, including the southern Precordillera. ...
... Rasettia Lochman is also a rare but persistent element of the upper Furongian faunas in North America (e.g., Lochman-Balk & Wilson 1958;Palmer 1968). Rasettia crucensis is morphologically similar to the type species Rasettia capax (Billings), from the lower Upper Sunwaptan of Quebec, western Newfoundland (Onchonotus richardsoni and Keithia subclavata faunas), Alaska ("Trempealeauan 1-Fauna" of Palmer 1968), Wisconsin (lower Saukia Zone), Texas, and Oklahoma [upper part of the Saratogia Zonelower part of the Rasettia magna Subzone (=Saukiella pyrene Subzone) of the Saukia Zone] (e.g., Rasetti 1944;Peck & McFarland 1954;Wilson 1954;Palmer 1968;Kindle 1982;Ludvigsen et al. 1989;Stitt & Loch 1993); as well as to Rasettia magna Ellinwood from the lower Upper Sunwaptan of Texas, Oklahoma (Rasettia magna Subzone, Saukia Zone) and Alberta (upper part of the Illaenurus Zone) (Bell & Ellinwood 1962;Stitt 1971;Westrop 1986 and references therein; Stitt & Loch 1993). ...
... The type species, Rasettia capax (Billings 1860 (Bell & Ellinwood 1962;Stitt 1971;Westrop 1986 and references therein), also has a close affinity with Rasettia crucensis. Specimens from Texas (Bell & Ellinwood 1962, pl. ...
The trilobites from the "Hungaia puelchana Zone" (=Saukia Zone) of the San Isidro area (Mendoza, western Argentina) were briefly described by Carlos Rusconi in the 1950s, and since then they have been cited frequently in the literature but not fully revised. Large numbers of specimens from late Cambrian allochthonous carbonate blocks (La Cruz Olistolith) of the Quebrada Oblicua are available in the ángel Borrello collections of the Museum of Natural Sciences of La Plata, Argentina. On the basis of this material, Micragnostus pehuenchensis (Rusconi), Hungaia puelchana Rusconi and Rasettia crucensis (Rusconi) are redescribed herein. In addition, Phoreotropis Raymond and Tatonaspis Kobayashi are reported from the Argentine Precordillera for the first time. The fauna studied has a clear Laurentian aspect and is assigned to the Upper Sunwaptan (upper Furongian).
... In fact, many of the new genera and species described from the Frederick and Grove Formations were collected from loose blocks in a stone wall near Frederick, Maryland! In contrast, systematic sampling of faunas within superbly exposed Upper Cambrian carbonate platform successions in the western U.S. and Canada eventually allowed development of highly refined trilobite-based zonations (Palmer 1954(Palmer , 1960(Palmer , 1965aGrant 1965;Winston & Nicholls 1967;Stitt 1971aStitt , 1977Stitt , 1983Ludvigsen 1982;Westrop 1986; among others). ...
... After protracted consideration of several families for which the new biomere might be named, she selected the Ptychaspididae and named the interval the Ptychaspid Biomere. (1971)(1972)(1973)(1974)(1975)(1976)(1977) James H. Stitt (Fig. 2B), a contemporary of Longacre's and also a doctoral student under Charlie Bell, documented a similar faunal succession through the Ptychaspid Biomere in southern Oklahoma (Stitt 1971a). Jim Stitt was an exceptionally methodical and diligent individual whose sampling of the fairly well-exposed, but only sparsely fossiliferous Upper Cambrian strata in the Arbuckle Mountains produced a data set (Stitt 1971a) that has been drawn upon heavily in many subsequent studies (see below). ...
... (1971)(1972)(1973)(1974)(1975)(1976)(1977) James H. Stitt (Fig. 2B), a contemporary of Longacre's and also a doctoral student under Charlie Bell, documented a similar faunal succession through the Ptychaspid Biomere in southern Oklahoma (Stitt 1971a). Jim Stitt was an exceptionally methodical and diligent individual whose sampling of the fairly well-exposed, but only sparsely fossiliferous Upper Cambrian strata in the Arbuckle Mountains produced a data set (Stitt 1971a) that has been drawn upon heavily in many subsequent studies (see below). Stitt sampled the entire 500-550 m Upper Cambrian succession, splitting rock from each 0.3 m (1foot) interval for a minimum of 10 minutes, thereby covering approximately 15 m of section per day. ...
... The radiation was divided into studies are here incorporated into an exfour phases. Early phases were characterized panded database which, in addition to inforby low diversity assemblages of species with mation from Oklahoma (Stitt 1971b(Stitt , 1977, short stratigraphic ranges, whereas those of Texas (Longacre 1970), and Montana and Wylater phases comprised many long-ranging oming (Grant 1965), also includes new results species. ...
... From a new analysis of Stitt's vigsen et al. in press). data from Oklahoma, Hardy (1985) concluded A major goal of this paper is to use the (Ludvigsen and Westrop, in Ludvigsen et al. in press), southern Alberta (Westrop 1986), and Oklahoma (Stitt 1971b(Stitt , 1977 The basal extinction interval comprises the I, major and Parabolinoides subzones and their correlatives. It is characterized by patterns of rapid species turnover and extensive cratonward migration of trilobites, similar to those described by Westrop and Ludvigsen (1987)for the upper boundary interval of the Sunwaptan Stage. ...
... As an alternative method of investigating trends in taxonomic diversity, patterns of within-collection species richness were examined in 85 large collections available from Alberta (Westrop 1984), Oklahoma (Stitt 1971b(Stitt , 1977,and Newfoundland (Ludvigsen and Westrop, in Ludvigsen et al. in press). Diversity was expressed as a simple index (number of species/log number of individuals) in order to allow for differences in Sample size between collections. ...
Recovery of trilobite faunas following a mass extinction during the Upper Cambrian Sunwaptan Stage (equal to the "Ptychaspid Biomere') involved increases in both within-habitat (alpha) diversity and in levels of biofacies differentiation. This pattern parallels, at a lower hierarchical level, the global increase in Phanerozoic marine invertebrate species richness which was influenced by changes in provinciality and in alpha diversity. Diversification slowed markedly in subtidal shelf carbonate habitats in the upper half of the stage, but continued in carbonate shelf margin environments, possibly due to higher rates of immigration from off-shelf sites. Trilobite clades appearing early in the stage have low centers of gravity, reflecting high immigration rates during and shortly after an interval of mass extinction. Expansion of shallow-water carbonate deposition in the upper half of the stage was accompanied by the spread of carbonate bank biofacies. Families occurring in these biofacies gradually increased in species richness and tended to have high centers of gravity. -Author
... However, one interval, corresponding to the Elvinia Zone of the Laurentian Steptoean Stage and the global Jiangshanian Stage, has yielded only three boulders (out of more than 460 fossiliferous boulders from the Miaolingian and Furongian; Kindle 1982). In contrast, Elvinia Zone faunas are abundant and widespread over the rest of the shelf (e.g., Wilson 1949Wilson , 1951Bell et al. 1952;Grant 1965;Stitt 1971;Kurtz 1975;Ludvigsen and Westrop 1983;Westrop 1986), not least because this interval is characterized by a major rise in sea level that pushed the shoreline far into the continental interior (the Sauk III transgression of various authors, including Palmer 1981;Brezinski et al. 2012;Miller et al. 2012). Nonetheless, the Jiangshanian boulders provide a unique glimpse of shelf margin trilobites of the Elvinia Zone and the fauna is unusual in being dominated by the "catillicephalid" Buttsia Wilson 1951. ...
... discussion: A few sclerites document the presence of Dellea in shelf margin settings. The genus has been reported widely in Laurentian North America, including Texas (Wilson 1949), Oklahoma (Frederickson 1949;Stitt 1971), Pennsylvania (Wilson 1951;Loch and Taylor 2004), Montana and Wyoming (Grant 1965), Missouri (Kurtz 1975), New York (Ludvigsen and Westrop 1983), Alberta (Westrop 1986), and the Northwest Territories (Pratt 1992). Unfortunately, most records are poorly illustrated by modern standards, and a debate regarding synonymy of two species first described from Texas, Dellea wilbernsensis Wilson 1949 (the type species of Dellea) and Dellea suada (Walcott, 1890) remains unresolved (see Ludvigsen andWestrop 1983, andTaylor 2004 for discussion). ...
Three shelf-derived boulders in debris flow conglomerates of the Downes Point Member of the Shallow Bay Formation of western Newfoundland yielded the first record of an Upper Cambrian shelf-margin trilobite fauna from the Elvinia Zone (Steptoean; Jiangshanian) in eastern North America. The fauna is dominated by the “catillicephalid” Buttsia Wilson, 1951, and resembles trilobite biofacies from microbial buildups in the Gatesburg Formation of Pennsylvania. It is correlative with the Cliffia latagenae Subzone, which is the youngest Steptoean biostratigraphic unit in the Gatesburg. New taxa are Triorygma burkhalteri gen. et sp. nov. and Buttsia trema sp. nov.
... Wilson (1949) left the genus unassigned and made only general comparisons with the pterocephaliid Pterocephalia Roemer, 1849; subsequent work in Pennsylvania (Wilson 1951) offered no further insight on relationships. In a similar vein, Bell et al. (1952) and Deland & Shaw (1956) simply ignored the question of affinities, whereas Stitt (1971) followed Lochman (in Moore 1959) in assigning the genus to the polyphyletic family Avonidae Lochman, 1936. Palmer (1965 made a case for a relationship with the family Menomoniidae Walcott, 1916, and his view was endorsed by Kurtz (1975). ...
... Xenocheilos is confined to the Elvinia Zone, a Furongian (Steptoean) biostratigraphic unit that is recognised widely across Laurentian North America. Many workers have noted that this zone could be subdivided to provide more resolution (e.g., Wilson 1951;Stitt 1971;Westrop 1986) and is in need of revision. For the purposes of this discussion, we will follow recent practice of dividing the Elvinia Zone into two informal 'subzones' or divisions (e.g., ). ...
... Although homotaxial successions of trilobite species useful for local intrabasinal correlation have been documented in some studies (e.g., Fisher, 1977; Ludvigsen, and modern trilobite-based zones within the Upper Cambrian and the Lower Ordovician platform carbonates of Laurentia with references (Refs.) to articles that describe taxonomic and biostratigraphic refinements for intervals delineated by numbered rectangles near the center of the diagram: 1, Rasetti (1965), Westrop (1992); 2, Palmer (1965a), Pratt (1992); 3, Rasetti (1961); 4, Taylor et al. (1999), Loch and Taylor (2004); 5, Longacre (1970); 6, Stitt (1971b); 7, Westrop (1986); 8, Stitt (1983); 9, Adrain et al. (2003); 10, Berg and Ross (1959); 11, Pratt (1988); 12, Boyce (1989);13, Ross et al. (1997), Dean (1989);14, Loch (2007); 15, Fortey (1979), Boyce (1989), Brett and Westrop (1996); 16, Hu (1963); 17, Adrain et al. (2009). Tremp. ...
... At various levels within the Cambrian and the Ordovician, recent systematic and biostratigraphic research has resurrected a problem confronted by biostratigraphers in the 1940s and 1950s. Lochman-Balk and Wilson (1958), and those who followed their lead in the next few decades, accomplished continent-wide correlation of many Cambrian and Ordovician zones by applying relatively broad species concepts that attributed appreciable morphologic variation to within-species geographic variation (Rasetti, 1961;Robison, 1964Robison, , 1976Grant, 1965;Palmer, 1965a;Winston and Nicholls, 1967;Longacre, 1970;Stitt, 1971bStitt, , 1977Stitt, , 1983Ludvigsen, 1982;Ludvigsen and Westrop, 1983;Westrop, 1986Westrop, , 1995Boyce, 1989;Palmer and Repina, 1993;Taylor et al., 1999;among others). In the last decade, more rigorous morphometric analysis of large collections from tightly constrained collection horizons has greatly narrowed the accepted range of morphologic variation for many Cambrian and Ordovician species. ...
... D shows that the highest beds of the type section of the Gorge Formation range into the highest Cambrian. Conodonts, including Monocostodus sevierensis (Miller, 1969) and presently undescribed trilobites from unit 24 indicate a correlation with the upper Symphysurina brevispicata or lower Symphysurina bulbosa Subzones on the Laurentian platform (see Stitt, 1971Stitt, , 1977. The trilobites include Geragnostus sp., Hystricurus sp., and Symphysurina sp. ...
... (see also Shaw, 1951Shaw, , 1931Shaw, , 1955aShaw, , 1958. Fryxellodontus lineatus Miller, 1969, a conodont restricted to Stitt's (1971) "Missisquoia typicalis" Subzone and lower Symphysurina brevispicata Subzone (Miller, 1980) in the Great Basin and south-central United States, occurs in sample F40-01 (Landing, 1983). ...
... Steptoean; Elvinia Biozone) from Oklahoma and was reported soon afterward from the coeval Gatesburg Formation of Pennsylvania (Wilson, 1951) with a larger sample that included a pygidium and librigena. However, the ensuing 50 years added only a handful of cranidia from Wyoming (Lochman and Hu, 1960), Oklahoma (Stitt, 1971), and Missouri (Kurtz, 1975), so that the genus remains at best a minor component of Elvina Zone faunas of Laurentian North America. ...
The Cambrian dokimocephalid trilobite genus Deckera Frederickson, 1949 is a minor component of Steptoean (Jiangshanian) faunas of Laurentian North America. The original diagnosis emphasized strongly inflated palpebral areas of fixed cheeks and elevated palpebral lobes as important and novel characters. An appraisal of archival and new specimens from Oklahoma, Missouri, Pennsylvania, Nevada, Utah, and Newfoundland show that the genus is geographically widespread and likely represented by as many as nine species, although only two of them are named formally. Deckera cf. D . aldenensis Frederickson, 1949 from Nevada extends the stratigraphic range of Deckera down to the base of the Jiangshanian Stage, and new species from Nevada and Newfoundland take the genus down farther, into upper Paibian strata. Paibian species show that some basal members of the genus have weakly inflated, nearly flat palpebral areas with palpebral lobes that sit well below the crest of the glabella. A revised diagnosis of Deckera focuses on the broad cranidium with width across the palpebral lobes much greater than the sagittal length. Pygidia are known for a few species and all of them have an unusual flexure of the posterior margin and border. Lectotype and paralectotype specimens are designated for Deckera completa .
... D. wilbernensis Wilson, 1949, as well as Plataspella, Pseudosaratogia and Kindbladia. It is worth noting that our collections from the lower Honey Creek Formation include cranidia of Kindbladia that both possess and lack occipital spines, so that previous identifications of only a single species in the Honey Creek (Stitt 1971(Stitt , 1977 may be incorrect; cranidia associated with B. kimbellorum are non-spinose and resemble K. angustana Resser, 1942. New data from Pennsylvania (Loch & Taylor 2004, fig. ...
... This "Cambrian Diversity Plateau" followed the Cambrian Explosion and preceded the Great Ordovician Biodiversification Event (Servais et al., 2010). The cause of the global diversity plateau is unclear, but repeated trilobite extinctions that affected shelf communities punctuate this interval in Laurentia (e.g., Lochman and Duncan, 1944;Lochman-Balk and Wilson, 1958;Palmer, 1965Palmer, , 1979Palmer, , 1984Longacre, 1970;Stitt, 1971aStitt, , b, 1975Stitt, , 1977Stitt, , 1983Westrop and Ludvigsen, 1987;Westrop, 1988Westrop, , 1989Westrop, , 1990Westrop, , 1996Loch et al., 1993;Westrop and Cuggy, 1999;Taylor et al., 2004;Adrain et al., 2009;Saltzman et al., 2015). The term 'biomere' refers to the stratigraphic packages bounded by these extinctions (Palmer, 1965;review in Taylor, 2006). ...
The Cambrian-Ordovician Diversity Plateau, between the Cambrian Explosion and the Ordovician Radiation, is punctuated by a series of well-documented Laurentian trilobite extinction events. These events define the bounding surfaces of trilobite ‘biomeres’ that correspond to North American stages, including those of the Sunwaptan and Skullrockian. Trilobites show a consistent pattern of recovery across these boundaries, and commonly each extinction and replacement of taxa is interpreted as a single event as changing environmental conditions spurred shoreward migration of shelf or oceanic faunas that displaced established cratonic faunas. Linguliform brachiopods are also abundant in strata of this interval, and we investigate their stratigraphic distribution across the Sunwaptan–Skullrockian Stage boundary in Texas through high-resolution stratigraphic sampling of subtidal sediments. We document complete genus- and species-level turnover of the linguliform brachiopod fauna coincident with trilobite extinction events, suggesting that these brachiopods were affected by the same factors that affected trilobites. The Skullrockian replacement fauna was cosmopolitan, with ties to Gondwana and Kazakhstan and to the Laurentian shelf environment. The timing of appearances of taxa suggests that the faunal migration onto the Laurentian shelf came from elsewhere during a transgression. The disappearance of the Sunwaptan fauna and the arrival of the Skullrockian fauna are distinct events. We suggest that ‘biomere’ events may be complex, and the cause of the extinction is not necessarily the same event that facilitates the appearance of a replacement fauna. We describe one new species, Schizambon langei .
UUID: http://zoobank.org/f6a5c11f-cd3d-4c16-b184-d808d3a5285f
... The zones shown in Figure 7.1 need future modification and refinement because the faunal change from one depositional belt to the next is too great for satisfactory correlation (Stitt, 1971). Lochman-Balk and Wilson (1958) demonstrated this problem by showing different ranges of genera in different areas of their shallow shelf and deeper depositional environments. ...
... 1965(Pal.mer, , 1965aLongacre, 1970;Stitt, 1971Stitt, , .1971a) and its application ~o the faunas under study. A new biomere is defined which irnrnediately underlies the type biomere. ...
PhD dissertation, SUNY Stony Brook, 1973
... 1965(Pal.mer, , 1965aLongacre, 1970;Stitt, 1971Stitt, , .1971a) and its application ~o the faunas under study. A new biomere is defined which irnrnediately underlies the type biomere. ...
PhD dissertation, SUNY Stony Brook, 1973
... The data set used to test the model consists of species from the critical period in shelf and shelf-margin biofacies in Alberta (Westrop 1986), District of Mackenzie (Ludvigsen 1982), Oklahoma (Stitt 1971b(Stitt , 1977, Texas (Winston and Nicholls 1967;Longacre 1970), and western Newfoundland (Ludvigsen and Westrop, in Ludvigsen et al. in press). The base of the critical period was used as a datum, and all portions of species ranges below this level were excluded from the analysis. ...
Survival of North American shelf trilobite families during the mass extinction across the upper boundary of the Upper Cambrian Sunwaptan Stage (="Ptychaspid Biomere') cannot be predicted from patterns of turnover among their component species: on the shelf, stratigraphic ranges of species belonging to surviving families do not differ significantly from those of eliminated families. Thus, the sorting of families during the extinctions cannot be explained by simple upward causation from the individual level. However, families that ranged from shelf to slope environments before the extinctions (most of which are pandemic) fared significantly better than those confined to shelf settings (which tend to be endemic to North America), indicating that family survival was influenced by geographic and environmental distribution, a property emergent above the individual level. -from Author
... Actual extinctions (upper large numbers) and apparent extinctions (lower small numbers) of species (S), genera (G), and families (F) in percentage across biofacies or subzonal boundaries in four sections through the uppermost Sunwaptan and basal Ibexian (District of Mackenzie, section KK[Ludvigsen 1982); Alberta, Wilcox Peak section[Westrop 1984); Oklahoma, U.S. Highway 57 and Joins Ranch sections[Stitt 1971b)). Biofacies codes as forFig. ...
We develop a simple biogeographic model which suggests that diversity of a faunal province is influenced profoundly by changes in the number of component biofacies. This model is tested with an analysis of biofacies distribution patterns across the upper boundary of the Sunwaptan Stage. The extinctions correspond closely to lithofacies shifts in the outer shelf that indicate the initiation of major paleogeographic changes. The effects of these changes cascade across the entire shelf by the shoreward migration of off-shelf and shelf-margin taxa. Biofacies become reduced in number through telescoping and their environmental ranges expand during the extinction interval. Selective survival of wide-ranging eurytopes may have influenced the dynamics of faunal replacement by lowering speciation rates of shelf taxa. Consequently, the proportion of shelf endemics will decline and biofacies will be dominated by immigrant taxa. There are sufficient similarities in extinction patterns across the upper boundary of the Sunwaptan Stage and those at other Upper Cambrian stage boundaries to suggest that the biogeographic model developed here may have broader application.-from Authors
... The trilobite genus Symphysurina is long established as an important faunal presence in Furongian to Lower Ordovician rocks of the allochthonous successions of the Cow Head Group (Kindle and Whittington, 1958;Whittington, 1968;Fortey and Skevington, 1980;Kindle, 1982;Fortey et al., 1982;Fortey, 1983;James and Stevens, 1986;Karim, 2008) and the Cooks Brook Formation (Boyce et al, 1992). It is also well represented in co-eval autochthonous platform carbonate shelf sequences throughout the Caledonian-Appalachian-Ouachitan orogenic belt of eastern and southern Laurentia, from Greenland (Poulsen, 1927(Poulsen, , 1937Cowie and Adams, 1957;McCobb and Owens, 2008;, in revision), through Scotland (Ingham et al., 1985, to northwestern Vermont (Shaw, 1951), the Champlain Valley and Mohawk Valley of New York-Vermont (Cleland, 1900(Cleland, , 1903Fisher, 1954;Landing et al., 2003;Westrop et al., 1993), New Jersey (Weller, 1903;Westrop et al., 1993), Pennsylvania (Raymond, 1910;Butts and Moore, 1936), Maryland (Sando, 1957), West Virginia (Woodward, 1951), Virginia (Orndorf et al., 1988;Taylor et al., 1992), and Oklahoma (Stitt, 1971(Stitt, , 1977(Stitt, , 1983 in the United States. Symphysurina and other trilobites, along with brachiopods, cephalopods, corals, echinoderms and gastropods, were lately discovered in western Newfoundland in the autochthonous Watts Bight Formation, St. George Group along the south coast of the Port au Port Peninsula near Ship Cove McCobb et al., 2011) and in 2012 at Pigeon Head a little farther to the west ( Figure 1 and Plate 1). ...
... Trilobite range data from the Wilberns Formation formed the basis of a second biomere, the Ptychaspid biomere, defined by Longacre (1970) to encompass the interval from the base of the Taenicephalus Zone upward to the base of the Missisquoia Zone. Stitt (1971bStitt ( , 1975 used the data from the Llano uplift, in combination with similarly precise range charts he produced through systematic sampling of the Ptychaspid biomere in Oklahoma (Stitt, 1971a), to construct his four-stage model of biomere development. Stage 1 involved the immigration of a low-diversity deepwater trilobite fauna onto the shallow shelf, which had been depopulated by extinctions at the end of the previous biomere. ...
Decimeter-scale sampling of the Cambrian and the lowermost Ordovician (Sauk megasequence) rocks of the Llano uplift, Texas, has produced a finely resolved biostratigraphic framework based primarily on trilobites and conodonts. Systematically collected trilobites of the Llano Uplift allow recognition of 13 biozones that extend from the Bolaspidella Biozone (Cambrian System, Marjuman Stage) through the Symphysurina Zone (Ordovician System, upper Skullrockian Stage). Systematic collection of conodonts has produced specimens assignable to 13 zones that range from the Proconodontus tenuiserratus Zone (Cambrian System, Sunwaptan Stage) through the Rossodus manitouensis Zone (Ordovician System, upper Skullrockian Stage). The base of the Ordovician System in the Llano uplift, as elsewhere, has been identified by the lowest occurrence of the conodont Iapetognathus fluctivagus and is closely approximated by the lowest occurrences of the cosmopolitan trilobite Juyjuyaspis and the Laurentian trilobite Symphysurina ‘‘bulbosa.’’ Although the overlying Ordovician strata of the Ellenburger Group have not been systematically sampled, scattered trilobite collections do establish the approximate positions of the base of the Stairsian Stage (based on Paraplethopeltis) and the base of the Jeffersonian Stage (based on Rananasus and Jeffersonia) in the Tanyard and Honeycut Formations, respectively.
Two Lotagnostus-dominated faunas from the Windfall Formation at Ninemile Canyon in the Antelope Range of Nevada, USA, are described: an older Lotagnostus nolani Fauna and younger L. rushtoni Fauna. The former is dominated by two morphs of Lotagnostus, one strongly scrobiculate and the other smooth to weakly scrobiculate. Both morphs fall within the broad concept advocated for L. americanus by Peng et al. (2015). The numerous (>1400 sclerites) specimens of Lotaganostus in collections of the L. nolani Fauna confirm that the two morphs do not intergrade and remain distinct throughout ontogeny. Both display multiple traits that distinguish them from the type material of L. americanus, justifying treatment as separate species. Similarly unique, diagnostic features were identified to restore the Asian species L. punctatus and L. asiaticus to full species status, whereas deficiencies in the type material for L. americanus warrant restriction of the name to the holotype. New species described from the Windfall include five agnostoids (Lotagnostus nolani, L. clarki, L. morrisoni, L. rushtoni, and Neoagnostus parki) and one trilobite (Bienvillia eurekensis). Plicatolina nyensis Taylor is reassigned to Mendoparabolina on the form of its pygidium. Conodonts from the Catlin Member of the Windfall Formation and overlying informal Caryocaris shale member of the Goodwin Formation at Ninemile Canyon provide a late Sunwaptan (Eoconodontus Zone) age for the Lotagnostus rushtoni Fauna and assign the entire Caryocaris shale to the early Ordovician Rossodus manitouensis Zone. Combined with published data on trilobite faunas, the conodont faunas confirm strong diachroneity for the top of the Catlin, and a lack of overlap in age between the Caryocaris shale and Bullwhacker Member of the Windfall in ranges to the north and east. Co-occurrence of Lotagnostus nolani and Mendoparabolina nyensis establishes age equivalence of the L. nolani Fauna with the Hedinaspis-Charchaqia (HC) Fauna at the base of the Hales Limestone in the Hot Creek Range, and earlier correlations of the latter with the L. punctatus Zone in Asia are supported. However, isolation of the HC Fauna in starved-basin deposits above a major sequence boundary at the base of the Hales, and ecologic restriction of Lotagnostus to lower slope and basinal environments that prevented association with endemic shallow marine taxa, renders correlation into the biostratigraphy of Laurentian upper slope and platform imprecise on the order of 10s, if not 100s of meters.
Tuff‐bearing upper Cambrian to lowermost Ordovician strata on Ko Tarutao island, Satun province, southernmost peninsular Thailand, contain a rich trilobite fauna relevant to global biostratigraphy, peri‐Gondwanan palaeogeography and shifting evolutionary mode. This area of Sibumasu, a lower Palaeozoic marginal Gondwanan terrane, is shown to have been closely associated with Australia, North China (Sino‐Korea) and other continental fragments from the supercontinent's northern equatorial sector, including South China at that time. Shared faunas also suggest a Kazakhstani and Laurentian association. Collections from eight sections yielded 10 newly discovered species and one new genus from ancient shoreface and inner shelf siliciclastic deposits. With the new taxa and revision of taxa known previously, we refine the age of the upper two formations of the Tarutao Group to the middle of Cambrian Stage 10, and lower–middle Tremadocian. Two biozones are erected for Sibumasu: the Eosaukia buravasi Zone, encompassing all Cambrian sections from Ko Tarutao, and the Asaphellus charoenmiti Zone, encompassing the Tremadocian fauna discussed herein. The new genus is Tarutaoia and new species are Tsinania sirindhornae , Pseudokoldinioidia maneekuti , Pagodia ? uhleini , Asaphellus charoenmiti , Tarutaoia techawani , Jiia talowaois , Caznaia imsamuti , Anderssonella undulata , Lophosaukia nuchanongi and Corbinia perforata . Other taxa reported for the first time from Tarutao are Mansuyia ? sp., Parakoldinioidia callosa Qian, Pseudagnostus sp., Homagnostus sp., Haniwa mucronata Shergold, Haniwa sosanensis ? Kobayashi, Lichengia simplex Shergold, Pacootasaukia sp., Wuhuia ? sp., Plethopeltella sp., Apatokephalus sp., Akoldinioidia sp. 1 and Koldinioidia sp.
Sepkoski (1981a,b, 1988) has characterized the Cambrian fauna as unique, both in terms of taxonomic composition and in environmental distribution of taxa. Compared with the rest of the Phanerozoic, the frequency of mass extinction in the Cambrian must also rank as a distinctive feature which had a profound impact on macroevolutionary patterns. Three well-documented extinctions occurred in the Upper Cambrian of North America (Figure 1; Palmer, 1979; Westrop and Ludvigsen, 1987) and are best expressed in the trilobite faunas. Possible older extinctions may be present at the top of the Olenellus Zone and near the base of the Bolaspidella Zone (e.g., see Palmer, 1982) but more data are required.
The circum-Arctic region has received considerable attention over the past several decades with vigorous debate focused on topics such as mechanisms for opening the Eurasian and Amerasian basins, the importance of plume-related magmatism in the development of the Arctic Ocean, and mechanisms for ancient terrane translation along the Arctic margins. In recognition of the 25th anniversary of the Circum-Arctic Structural Events (CASE) program, an international polar research effort organized and led by the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) of Germany, this volume presents results from 18 major field expeditions involving over 100 international geoscientists from a broad spectrum of disciplines. The resulting publication focuses on the Proterozoic to Cenozoic tectonic evolution of the circum-Arctic region with correlations to adjacent orogens.
The first descriptions of Laurentian Lower Ordovician conodonts were in the 1930s in the central USA. Authors boiled shales to free the conodont elements. The use of acetic acid began in 1940 at the University of Missouri. The first study of Cambrian conodonts was in 1959; part of the material was from the western USA and part from northern Europe. In the mid 1960s, research began to be based on measured sections and systematically collected samples; many new taxa still were being described. Histological studies resulted in recognising three major groups of Cambrian conodonts, protoconodonts, paraconodonts, and euconodonts. The latter group was the most successful. Preliminary biozonal frameworks were established in the early 1970s and were tied into biozonations based on other fossil groups. Conodont studies became more widespread geographically during the 1980s, biozonations were refined, and conodont zones began to be correlated globally based on many cosmopolitan taxa. In the 1980s, geochemists found that conodonts were useful source materials for chemostratigraphy. The Pander Society was founded in 1967. Regular meetings of the society have been held since 1968 in the USA and internationally, resulting in many important proceedings volumes. The International Working Group on the Cambrian–Ordovician Boundary decided to use conodonts as the primary fossil group to define that boundary, thus stimulating intensive study of conodonts of that age. Definition of that boundary was achieved in 2001, although problems remain because of redeposited conodonts at the stratotype section. A Working Group will recommend a GSSP for the base of the highest stage of the Cambrian, Stage 10. The lowest occurrence of the euconodont Eoconodontus notchpeakensis (Miller Journal of Paleontology, 43(2), 413–439 1969) is being considered to define the base of that stage. The species occurs in depositional environments from nearshore sandstones and dolostones to deep-ocean radiolarian cherts, indicating that conodonts had become adapted to many depositional environments during the late Cambrian. The alternative fossil for marking the base of Stage 10 is the lowest occurrence of an agnostoid arthropod, Lotagnostus americanus (Salter 1860), which has a controversial taxonomy.
The Port au Port Group of western Newfoundland is a sequence of Upper Cambrian (Marjuman–Sunwaptan) shallow subtidal–supratidal carbonates and fine siliciclastics that are organized into three large scale sedimentary grand cycles. Low diversity trilobite faunas from the Marjuman and Steptoean portions (March Point and Petit Jardin Formations) include 17 species that are assigned to 16 genera; one species, Coosina kindlei , is new. Biostratigraphic analysis confirms earlier suggestions that the grand cycles boundaries record major intervals of onlap that can be recognized in other parts of North America and may be related to eustatic sea level rises.
The type section of the Basal Silty Member of the Survey Peak Formation spans the Cambrian–Ordovician boundary (North American usage) at Mount Wilson in the southern Canadian Rocky Mountains. The zonal and subzonal terminology through the boundary interval developed in Texas and Oklahoma is applicable to the trilobite faunas recovered from the section. The oldest trilobites recovered in this study occur in the top of the underlying Mistaya Formation and are assigned to the Saukiella serotina Subzone of the Upper Cambrian Saukia Zone. Trilobites and brachiopods of the S. serotina and Eurekia apopsis Subzones of the Saukia Zone occur in the lower half of the Basal Silty Member; trilobites and brachiopods assigned to the Lower Ordovician Missisquoia Zone and the Symphysurina brevispicata Subzone of the Symphysurina Zone occur in the upper half of the Basal Silty Member. The S. brevispicata Subzone extends an unknown distance into the Putty Shale Member of the Survey Peak Formation.
The extinction horizons at the base of the Eurekia apopsis Subzone and at the base of the Missisquoia depressa Subzone (the Cambrian–Ordovician boundary) occur within the Basal Silty Member of the Survey Peak Formation, not at the formational contact with the underlying Mistaya Formation. This leaves hypotheses linking immigration of the replacement trilobite faunas to major lithofacies changes through the boundary interval as untenable. Critical review of the evidence for the extinctions at the end of the Ptychaspid Biomere suggests that they were caused by an invasion of the shelf region by cold, anoxic water.
Forty-seven taxa are illustrated and 18 of those which provide new taxonomic information are discussed. One new genus, Rampartaspis Loch, is described in addition to four new species: Eurekia plectocanthus Loch, Highgatella wilsoni Derby, Macronoda punctata Derby, and Rampartaspis dissimulosulcus Loch. The identifications of trilobites and brachiopods in this paper revise those of Aitken and Norford (1967) and Derby et al. (1972) and result in minor changes in the reported positions of the bases of the Missisquoia and Symphysurina Zones. Revision of the identification of some trilobites in Dean (1989) changes the biostratigraphic interpretation of the Basal Silty Member at Wilcox Pass, Albert, Canada.
Trilobites from the Missisquoia Zone and the Symphysurina brevispicata Subzone of the Symphysurina Zone (Ibexian Series, lowest Ordovician) were collected from measured sections in the uppermost Deadwood Formation in the Black Hills of South Dakota and Bear Lodge Mountains in northeasternmost Wyoming. These collections were made by Christina Lochman-Balk and her students, and turned over to the author to complete the project. They are compared with previous reported occurrences of this fauna from this area. No trilobites from the underlying Sunwaptan Stage (Upper Cambrian) occur with the lowest Ordovician trilobites, suggesting that the sharp faunal extinction at the base of the Ordovician (North American sense = Eurekia apopsis Zone, Ibexian Series) occurred in the Deadwood Formation as it did over all of the North American continent.
Several localities within the heterolithic facies of the St. Lawrence Formation (Upper Cambrian) of Wisconsin and Minnesota yield specimens with phosphatic exoskeletons, quadrate cross sections composed of four equidimensional faces each bearing a midline, and possible holdfast attachment during life. These specimens are here referred to the order Conulariida, class Scyphozoa. Their fine, tuberculate surface ornament and serially invaginated midline structure serve to define a new genus, Baccaconularia, to which two new species, B. robinsoni and B. meyeri, are assigned. Conularia cambria Walcott 1890, also from the Cambrian of the northern Mississippi Valley and long dismissed as a misidentified trilobite fragment, is illustrated photographically for the first time. This species occurs in rocks stratigraphically beneath the St. Lawrence Formation. Specimens assigned to this species by Walcott are conulariids, but lack features now considered diagnostic of either Conularia or Baccaconularia. Walcott's material is insufficient to permit detailed taxonomic evaluation, and we isolate this name to this material, pending the collection of additional, better preserved specimens. Together, Baccaconularia and Conularia cambria contain the oldest large conulariids, and these narrow a stratigraphic gap between other large conulariids known from the Lower Ordovician onwards, and smaller fossils with conulariid affinities known only from Lower Cambrian rocks.
On Friday September 17 Jim Stitt died quietly in his sleep, ending a long and characteristically tenacious battle with cancer. His passing leaves a void of great magnitude in the geological sciences and in the lives of the many people whom he influenced as family, friends, or colleagues. I was Jim's first Ph.D. student at the University of Missouri, where he spent the past 31 years as a pillar of the geology program, serving at various times as Chair and Graduate Student Advisor. Jim is well known and respected for an impressive body of meticulously crafted taxonomic and biostratigraphic studies on trilobites and brachiopods. His three monographs on faunas in the Arbuckle and Wichita Mountains of Oklahoma (Stitt, 1971a, 1977, 1983) established that area as a standard for correlation of Upper Cambrian and Lower Ordovician strata in North America. This “Oklahoma trilogy” is a treasure trove of taxonomic and biostratigraphic data that has been drawn upon heavily in numerous subsequent biostratigraphic and paleobiologic studies. It provides a biozonation of unparalleled precision for carbonate platform facies of that interval, ironically assembled in an area where rocks of that age yield their fossils only reluctantly. Jim took great pride in extracting useful information from difficult rocks. He passed that laudable attitude on to his academic offspring, along with the sense of satisfaction he derived from seeing his data put to good use in solving geologic or paleobiologic problems, in his own work and in that of others. At the same time, he was always complimentary and supportive of more theoretical or abstract research, an attitude sadly lacking in some practitioners with a bent toward applied paleontology.
The Antiklinalbugt Formation of northeast Greenland comprises peritidal to subtidal carbonate sediments, deposited in shallow shelf settings during an early Tremadocian transgressive-regressive megacycle. The succession of shales and microbial, muddy and grainy limestone, with minor dolostone at the base and top, terminates at the cryptic Fimbulfjeld disconformity. The formation has yielded trilobites collected on Ella Ø, Albert Heim Bjerge, and Kap Weber by C. Poulsen (1920s and 1930s), J. W. Cowie and P. J. Adams (1950s), and during recent field studies in 2000 and 2001. The fauna includes dimeropygids Tulepyge cowiei and T. tesella n. spp., hystricurids Millardicurus and Hystricurus , and several species of Symphysurina. Micragnostus chiushuensis (Kobayashi, 1931) is rare, as are Chasbellus sp., Clelandia sp., and Lunacrania ?. The presence of several Symphysurina species places the Antiklinalbugt Formation within the Symphysurina Zone. Chasbellus indicates the upper (lower Ordovician) part of the Symphysurina Zone for the lower upper Antiklinalbugt Formation. Conodonts place the middle lower formation in the Cordylodus intermedius conodont Biozone, the lower upper part in the Cordylodus angulatus conodont Biozone and the uppermost part in the Rossodus manitouensis conodont Biozone. This combined fauna is characteristic of the upper Skullrockian Stage of the Ibexian Series, with the lower part of the Antiklinalbugt Formation lying within the uppermost Cambrian of North America, and the upper part within the lower Ordovician. The entire formation lies within the global Tremadocian Stage of the early Ordovician.
Jujuyaspis borealis is reported from earliest Ordovician (North American usage) limestones in central Texas and western Utah, the first time this species has been recognized in the United States. Jujuyaspis is a widespread olenid trilobite that occurs near the base of the Tremadoc Series in a variety of lithologies in North and South America, Europe, and Asia. When international agreement is reached on the exact horizon at or near the base of the Tremadoc Series that is to be used as the Cambrian-Ordovician boundary, Jujuyaspis will likely prove to be a very useful taxon for recognition of the boundary interval. -Authors
Uppermost Cambrian and lowest Ordovician slope deposits in Highgate Gorge, northwestern Vermont, yield a succession of conodont faunas (and a few associated trilobite species) similar to that observed in coeval North American carbonate-platform sequences. Decimeter-scale sampling of a 15-m-interval in two sections comprising thin-bedded limestone-shale rhythmites alternating with thick-bedded debris flow conglomerates yielded 60 trilobite specimens and more than 5000 conodont elements from 48 productive horizons. The new biostratigraphic control does not support earlier claims that the lowest occurrence of Cordylodus proavus in the Gorge Formation and presumably in other slope sequences is significantly older than the base of the C. proavus Zone in platform deposits; rather, it demonstrates the isochronous persistence of this boundary across the North American (Laurentian) shelf margin into Iapetan slope deposits. -from Authors
Trilobites assigned to 29 genera and 39 species are reported from the Deadwood Formation in the Black Hills of South Dakota. Two new species, Prosaukia lochmani and Arcifimbria pahasapaensis, are described. Brachiopods are reported from the Taenicephalus Zone.
A biostratigraphic zonation is established for the upper part of the Deadwood Formation. The Taenicephalus Zone in the lower part of the study interval is succeeded upsection by the Ellipsocephaloides Zone, both of which are assigned to the Franconian Stage. These two zones are overlain in turn by the Illaenurus and Saukia Zones of the Trempealeauan Stage. These zones are used to correlate this part of the Deadwood with coeval strata in Montana and Wyoming, central Texas, Oklahoma, and Alberta, Canada. The lowstand of sea level that occurred in the Great Basin at the time of the deposition of the Saukiella junia Subzone of the Saukia Zone probably extended eastward into the Black Hills, resulting in the absence of this fauna in the Black Hills.
Trilobites collected during the past 20 years from the Morgan Creek, Point Peak, and San Saba Members of the Wilberns Formation comprise 89 species assigned to 45 genera belonging to zones of the upper Franconian and Trempealeauan Stages of the Upper Cambrian Croixan Series. New zonal names are proposed in the interest of a regionally applicable nomenclature. Although none of the zonal nomenclature is identical to that of the 1944 Cambrian Correlation Chart of Howell et al. , the four zones recognized in central Texas are equivalent to the eight highest zones on the Chart. Stratigraphically lowest is the Franconian Taenicephalus Zone, with a locally recognized Parabolinoides Subzone at its base; this zone is equivalent to the Conaspis Zone of the Correlation Chart. The Franconian Idahoia Zone, with a locally recognized Idahoia lirae Subzone at its base, is equivalent to the Ptychaspis Subzone of the Ptychaspis-Prosaukia Zone of the Correlation Chart. The sparsely fossiliferous Ellipsocephaloides Zone corresponds to the Prosaukia Subzone of the Ptychaspis-Prosaukia Zone on the Chart. Almost two-thirds of the trilobite species described occur in the Trempealeauan Saukia Zone, which corresponds to the five highest zones of the Correlation Chart; local subzones, in ascending order, are the Saukiella pyrene Subzone, the Saukiella junta Subzone, the Saukiella serotina Subzone, and the Corbinia apopsis Subzone.
The succession of ptychoparioid trilobite faunas within these zones characterizes the Ptychaspid Biomere. The base of the biomere is at the base of the Taenicephalus Zone; the top coincides with the lowest occurrence of an Ordovician trilobite fauna. Trilobite families that characterize the Ptychaspid Biomere are the Ptychaspididae and the Parabolinoididae.
Systematic descriptions include two new subfamilies, Drumaspidinae and Ptychaspidinae, and eight new species, Conaspis leptoholcis, Idiomesus infimus, Euptychaspis frontalis, Keithiella scapane, Saukiella serotina, Prosaukia remora, Calvinella prethoparia , and Westonaspis ? texana .
Fourteen new species and six new genera of the molluscan class Monoplacophora are described from the Upper Cambrian Potosi and Eminence formations and the Lower Ordovician Gasconade Formation of the Ozark Uplift of Missouri and some new biostratigraphic horizons are introduced. A new superfamily, the Hypseloconellacea nom. trans. Knight, 1956, and a new family, the Shelbyoceridae, are named. The genus Proplina is represented by five new species: P. inflatus, P. suttoni from the Cambrian Potosi Formation, P. arcua from the Cambrian Eminence Formation and P. meramecensis and P. sibeliusi from the Lower Ordovician Gasconade Formation. A new genus and species in the subfamily Proplininae, Ozarkplina meramecensis , is described from the Upper Cambrian Eminence Formation. Four new monoplacophoran genera in the superfamily Hypseloconellacea and their species are described, including: Cambrioconus expansus, Orthoconus striatus, Cornuella parva from the Eminence Formation, and Gasconadeoconus ponderosa, G. waynesvillensis, G. expansus from the Gasconade Formation. A new genus in the new family Shelbyoceridae, Archeoconus missourensis , is described from the Eminence Formation and a new species of Shelbyoceras, S. bigpineyensis , is described from the Gasconade Formation.
The 70 Ma Ordovician Period is characterized by extensive epeiric seas, paleocontinent dispersal, intervals of intense volcanism and black shale deposition, a greenhouse climate state deteriorating to a brief icehouse state, strong faunal provincialism, and profound changes to the biota including the changeover from the Cambrian Fauna to the Paleozoic Fauna. Although many invertebrate phyla diversify during the Ordovician, precise biostratigraphic and global biogeographic data are provided best by conodonts, trilobites and graptolites. These three groups are used in this chapter to recognize five major bio-events four of which correspond closely to Series boundaries: Basal Tremadoc (BTc), Basal Arenig (B’Ag), Basal Llanvirn (B’Ln), Basal Caradoc (B’Cc) and Upper Ashgill (U’Al). Most of these correspond to significant eustatic events and the latter to the terminal Ordovician glaciation. The first four are each characterized by extinctions but these are overshadowed by a rapid innovation event with a radiation of a more diversified fauna; the U’Al is a severe extinction event, second only to the terminal Permian event in the entire Phanerozoic. Compared to many other Phanerozoic systems, the Ordovician is a period of considerable biologic, climatic and oceanographic complexity within which the balance between the forcing processes that produced the major and minor events is still not well understood.
Analysis of 164 collections from shelf facies of Laurentian North America indicates that three successive trilobite mass extinctions at Late Cambrian stage boundary intervals ('biomere' boundaries) are characterized by a common pattern of change in distributional paleoecology and species diversity. In all cases, the extinction intervals are marked by a shift to biofacies that have broader environmental distributions than those prior to the onset of extinctions, implying a reduction in between-habitat (beta) diversity. Significant declines in within-habitat (alpha) diversity also characterize each extinction and the compositions of shelf biofacies record extensive immigration of taxa from off-shelf and shelf-margin sites; The nature and extent of ecologic disruption of the shelf appears to be comparable to changes associated with major mass extinctions, such as those at the end of the Ordovician and Permian. Unlike major mass extinctions, the Cambrian events are followed by a complete recovery of diversity and biofacies structure within a few million years.
The potential role of stratigraphic order in phylogeny reconstruction is among the most contentious issues in contemporary paleontology (e.g., Norell, 1996; Wagner, 1996). Most workers agree that the distribution of taxa in time is essential information which should inform any evolutionary hypothesis. What is not agreed upon is whether that sampled distribution is itself evidence of relationship, and whether time-ordering should constrain a primary phylogenetic hypothesis. The question boils down to whether relationship should be determined using intrinsic biological information alone, or by using a certain amount of biological information, countermanded to some or other extent by extrinsic temporal information.
The Ordovician saw the transformation of marine benthic communities from the trilobite-based Cambrian Fauna to the brachiopod-dominated Paleozoic Fauna. An evaluation of the changing importance of trilobites during the Ordovician can be made from accurate assessments of taxonomic richness in various habitats. Here we present a new compilation of trilobite alpha diversity based on field collections and survey of the literature. The data indicate that trilobite species richness within nearshore, shallow subtidal, carbonate buildup and deep subtidal shelf environments was essentially constant between the Late Cambrian and the Late Ordovician. The alpha diversity patterns do not support the notion that trilobites became displaced from inner shelf environments during the Ordovician. Rather, the data are consistent with a decline in relative importance of the group through dilution as newly radiating invertebrate groups entered Ordovician paleocommunities. They also imply that direct interactions between elements of the Cambrian and Paleozoic faunas were not involved in the Ordovician reorganization of paleocommunities. Like many other major faunal transitions during the Phanerozoic, the Ordovician radiations appear to have been essentially non-competitive in nature.
An abundant and well preserved trilobite fauna is described from Upper Cambrian calcareous mudstones of the McKay Group, near Cranbrook in southeastern British Columbia. The trilobites are mostly atriculated, consisting of similar numbers of molts and carcasses. They are representative of a new deep water biofacies, the Wujiajiania Biofacies, and a new Wujiajiania sutherlandi Fauna of late Steptoean age. Thr trilobites were collected from a narrow interval (<20 m thick) of richly fossiliferous strata, in a thick sequence of unfossiliferous to sparsely fossiliferous strata of similar lithology. The fauna includes fourteen species, six of which are new: Aciculolenus palmeri, Burnetiella leechi, Hedinaspis canadensis, Labiostria westropi, Pterocephalia norfordi, and Wujiajiania sutherlandi.
Six third-order depositional sequences are documented for Late Cambrian time by interbasinal correlation of cyclic carbonates from tectonic settings in the Appalachian and Cordilleran passive margins, the Texas cratonic embayment, and the southern Oklahoma aulacogen. Paleobathymetric interpretation, integrated with graphic correlation, is used to establish the relative synchroneity of Upper Cambrian depositional sequences and is crosschecked with two quantitative techniques that provide an approximation of the accommodation history independent of fluctuations in carbonate sediment production. The first technique, Fischer plots, graphically illustrates systematic changes in the stacking patterns of meter-scale cycles that presumably reflect third-order changes in accommodation potential. The second technique, subsidence analysis, determines the accommodation remaining after the isostatic and thermo-tectonic components of total decompacted subsidence have been removed. Integrating the three methods enhances the interbasinal correlation of individual third-order depositional sequences and permits the construction of a robust relative sea-level curve for the Upper Cambrian of North America.
Brachiopods assigned to eight genera and 15 species have been recovered from Upper Cambrian (Franconian and Trempeauan Stages) and lowest Ordovician strata in the Arbuckle and Wichita Mountains of Oklahoma. Species of Ocnerorthis and Eoorthis occur in the Reagan Sandstone and Honey Creek Limestone of the Timbered Hills Group. Species of Billingsella appear in the Honey Creek and range upward into the overlying Fort Sill and Signal Mountain Limestones of the Arbuckle Group. Species of Cymbithytis, Finkelnburgia, Nanorthis, and Apheoorthis succeed each other upsection in the Signal Mountain Limestone. Five brachiopod zones and one subzone have been established that can be used to correlate the measured sections in the Arbuckle and Wichita Mountains, and to correlate with varying degrees of confidence from Oklahoma to similar brachiopod occurrences in other areas in the United States.
Within the Cambrian about six globally traceable extinction events are recognised, of which those across the Mid Botomian through to Toyonian/Amgan are of highest order. All events are associated with facies changes, mostly combined with stepwise extinctions that preferentially affected nearshore and endemic taxa. The events appear to have coincided with changes in climatic and/or oceanographic parameters, such as sea level or fluctuation in oxygen-depleted water masses.
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