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... perlata Lazarenko, 1966и P. lucida Lazarenko, 1966 Кроме этих видов, в составе данного рода из вестны еще четыре вида, которые были описаны за пределами Сибирской платформы. Это P. kindlei Shaw, 1951и P. nyensis Taylor, 1976, из вестные из верхнего кембрия Северной Америки (Shaw, 1951;Taylor, 1976), P. scalpta Harrington et Leanza, 1957из низов ордовика Аргентины (Har rington, Leanza, 1957 и P. partita Lisogor, 1970 из верхнего кембрия Казахстана (Лисогор, 1970). ...
... perlata Lazarenko, 1966и P. lucida Lazarenko, 1966 Кроме этих видов, в составе данного рода из вестны еще четыре вида, которые были описаны за пределами Сибирской платформы. Это P. kindlei Shaw, 1951и P. nyensis Taylor, 1976, из вестные из верхнего кембрия Северной Америки (Shaw, 1951;Taylor, 1976), P. scalpta Harrington et Leanza, 1957из низов ордовика Аргентины (Har rington, Leanza, 1957 и P. partita Lisogor, 1970 из верхнего кембрия Казахстана (Лисогор, 1970). ...
... В ходе исследований отмечено, что род Plicato lina Shaw, 1951 Plicatolina lucida: Лазаренко, 1966, с. 62, табл. VII, фиг. ...
... This convention also reflected the early convention to assign the Laurentian "Missisquoia Zone" to the lowest Ordovician. Landing (1983) followed Keith (1932), Schuchert (1937), and Shaw (1951) in regarding the black mudstone-dominated interval under the Highgate thrust as the type section of the Ordovician Highgate Formation, and saw the Gorge Formation as a Cambrian interval dominated by debris flows and turbiditic sandstones. ...
... "Missisquoia typicalis" type locality.-The type locality of the upper Upper Cambrian trilobite "Missisquoia typicalis" Shaw, 1951[now Parakoldinioidia stitti Fortey, 1983, lies in poorly exposed lime mudstones in unit 40 ( Figure 16). Current-disarticulated, allochthonous trilobites reported from this horizon (R. J. Ross, Jr., in Landing, 1983) include Geragnostus sp.; Parakoldinioidia stitti; Symphysurina minima Shaw, 1951;Parabolinella?;and ...
... type locality of the upper Upper Cambrian trilobite "Missisquoia typicalis" Shaw, 1951[now Parakoldinioidia stitti Fortey, 1983, lies in poorly exposed lime mudstones in unit 40 ( Figure 16). Current-disarticulated, allochthonous trilobites reported from this horizon (R. J. Ross, Jr., in Landing, 1983) include Geragnostus sp.; Parakoldinioidia stitti; Symphysurina minima Shaw, 1951;Parabolinella?;and Terranovella? sp. ...
... In west-central \Termont, Cady (1945) has brought order to the chaotic concepts of stratigraphy and structure that had existed there. In the St. Albans area, Shaw (1949 and has even more recently rationalized the stratigraphic relations. However, the rocks in west-central Vermont are dominantly calcareous, whereas those in the St. Albans area contain extensive argillaceous and arenacous beds. ...
... These studies consisted of analyses of the insoluble residues of some of the carbonate rocks, a brief petrographic study of some forumtions, and a spectrographic analysis of the Dunham Dolomite. Fossils were scarce and the few specimens collected were studied by Alan B. Shaw, who recently described the Cambrian faunas of northwestern Vermont (Shaw, 1951(Shaw, , 1954(Shaw, , 1958. ...
... These studies consisted of analyses of the insoluble residues of some of the carbonate rocks, a brief petrographic study of some forumtions, and a spectrographic analysis of the Dunham Dolomite. Fossils were scarce and the few specimens collected were studied by Alan B. Shaw, who recently described the Cambrian faunas of northwestern Vermont (Shaw, 1951(Shaw, , 1954(Shaw, , 1958. ...
... Members of the genus Plicatolina Shaw, 1951 are widespread in Upper Cambrian deposits in the north east of the Siberian Platform in the area of the lower reaches of the Lena River (Kharaulakh Mountains) and on the Olenek Uplift (Pokrovskaya, 1966;Laza renko, 1966;Kembrii.., 2008). Cambrian deposits appear on the surface in wings of anticline folds (Chekurovka and Bulkur Anticlines). ...
... lucida Lazarenko, 1966. In addition to these species, four other species of this genus were described from areas other than the Siberian Platform: P. kindlei Shaw, 1951 andP. nyensis Taylor, 1976 from the Upper Cambrian of North America (Shaw, 1951;Taylor, 1976), P. scalpta Har rington et Leanza, 1957 from lower beds of the Ordov ician of Argentina (Harrington and Leanza, 1957), and P. partita Lisogor, 1970 from the Upper Cambrian of Kazakhstan (Lisogor, 1970). ...
... In addition to these species, four other species of this genus were described from areas other than the Siberian Platform: P. kindlei Shaw, 1951 andP. nyensis Taylor, 1976 from the Upper Cambrian of North America (Shaw, 1951;Taylor, 1976), P. scalpta Har rington et Leanza, 1957 from lower beds of the Ordov ician of Argentina (Harrington and Leanza, 1957), and P. partita Lisogor, 1970 from the Upper Cambrian of Kazakhstan (Lisogor, 1970). 4 During an expedition working in 2009 in the lower reaches of the Lena River, in the northern wing of the Chekurovka Anticline, a collection of trilobites was amassed (Fig. 1). ...
A collection of trilobites of the genus Plicatolina Shaw, 1951 from the upper Ogon'or Formation, Cambrian Section, Chekurovka Anticline (northeastern Siberian Platform, Kharaulakh Mountains), is studied. It is shown that all specimens of this collection belong to the same species, Plicatolina lucida Lazarenko, 1966, but represent different age stages. It is also shown that species of the genus Plicatolina (P. quadrata Pokrovskaya, 1966 and P. yakutica Pokrovskaya, 1966) described from the Upper Cambrian of the Siberian Platform are probably synonyms of P. lucida.
... described from Vermont (Landing 1978;Shaw 1951), New York (Taylor and Halley 1974), Ok-Correlation Problems in the Early Ordovician lahoma (Stitt 1971(Stitt , 1977, Utah (Miller 1978), and (1) The base of the Tremadoc Series has not vet Texas (Winston and Nicholls 1967 The section at Ogof-ddu, near Criccieth in North proposed by Bulman (1967). position of the boundary has varied somewhat but the base of the Missisquoia Zone has found general favour in recent years. ...
... This fauna is undoubtedly indicative of the Missisquoia Zone. The specimen of the index species agrees well with the original description of Shaw (1951) and with widespread occurrences in the United States (Winston and Nicholls 1967;Taylor and Halley 1974;Stitt 1971) and Canada (Dean 1977). Highgatella cordilleri is also widespread in the same zone. ...
... figured by Stitt (1977, P1. 6, Fig. 3) from the Missisquoia Zone of Oklahoma can be matched exactly in our fauna. The Symphysurina species is very like material figured by Shaw (1951), which accompanies Missisquoia, but its precise determination must await examination of the types. ...
The Cow Head Group in western Newfoundland includes a record of continuous graptolite evolution across the Cambrian–Ordovician boundary. In sections at Broom Point, interbedded breccias contain blocks with rich platform trilobite faunas which give a complete succession of North American zones. The stratigraphic relationship between graptolites and trilobites clearly establishes that the base of the type Tremadoc Series lies above that of the Missisquoia Zone. The sequence of earliest planktonic graptolites is the most complete known and serves to remove objections to the selection of Dictyonema flabelliforme, or one of its subspecies, as an index for the base of the Ordovician System.
... The family Missisquoiidae is an important group of Furongian (late Cambrian) and early Ordovician trilobites in eastern Gondwana and Laurentia. The type genus Missisquoia Shaw, 1951 was long employed as an index taxon for defining the base of the Ordovician in Laurentia (Winston and Nicholls, 1967;Stitt, 1971Stitt, , 1977Ross et al., 1982;Loch et al., 1993;Ross et al., 1997). More recently, the Global Stratotype Section and Point for the base of the Ordovician was ratified at the slightly younger level at the lowest occurrence of a conodont species, Iapetognathus fluctivagus Nicoll et al., 1999(Cooper et al., 2001. ...
... Other species included: Parakoldinioidia stitti Fortey, 1983 (= Missisquoia typicalis Shaw, 1951); P. bigranulosa Shergold, 1975;P. sp. ...
... Parakoldinioidia stitti was based on variously distorted specimens (Shaw, 1951) and subsequently was reported from many localities in Laurentia (see Appendix 1). As noted by Taylor and Halley (1974) and Dean (1977), however, a wide range of morphological variations within P. stitti is evident. ...
The missisquoiids are among the most important trilobites in the Cambrian–Ordovician boundary interval of Laurentia and Gondwana. This study deals with a systematic review of the family Missisquoiidae based on a cladistic analysis and explores their palaeobiogeographical history. A total of 22 missisquoiid species were selected for cladistic analysis. The cladistic results demonstrate that the family Missisquoiidae includes Parakoldinioidia, Pseudokoldinioidia, Tangshanaspis, and Tasmanocephalus; Lunacrania and Hardyia are included with reservation. The well-known genus Missisquoia is treated as a junior synonym of Parakoldinioidia. Based on the distribution of the missisquoiids, six palaeogeographical areas are recognised: Sino-Korea, Yangtze, Australia, southern Laurentia, northwestern Laurentia, and northeastern Laurentia. Palaeogeographical analyses show that the missisquoiids originated in Gondwana and continued to expand their geographical range within the continent and eventually expanded into the Laurentia. Optimisation results of geographical area transitions demonstrate that there were transitions between the two continents, and evolution of the Laurentian missisquoiids appears to have been strongly influenced by the Gondwanan counterparts. We suggest that dispersal of non-fossilised egg stage probably transported by oceanic currents may have been responsible for these inter-continental transitions.
... 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. ...
... However, noted that this taxon likely represents more than one species, and were unable to code it for phylogenetic analysis. Westrop (in Landing et al. 2011) agreed with Lee et al., and restricted P. stitti to its variably deformed type material from Vermont (Shaw 1951). Westrop (2013) recently evaluated the record of Tangshanaspis in Laurentia and concluded that Stitt (1971) erroneously associated sclerites of two distinct species when he named Missisquoia depressa. ...
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.
... For each specimen the measurements were taken in one plane. Symbols used for sc1erite dimensions of non-agnostidean trilobites are taken from SHAW (1956SHAW ( , 1957 and TEMPLE (1975) (Thble 1,Textfig. 5), and for the Agnostina from AHLBERG & AHLGREN (1996) (Table 2, Text- fig. ...
... The number of specimens, for which Table 1. Symbols applied for the measured linear dimensions of non-agnostidean trilobites, after SHAW (1956SHAW ( , 1957 and TEMPLE (1975) al total cranidiallength (sag.) -compnted as b 1 + f1 b total glabellar length (sag.) ...
Thirty-seven trilobite taxa from the Upper Cambrian of the Holy Cross Mountains are described; eighteen are noted for the first time in Poland. Eleven of the previously recognised species are considered to be junior synonyms. Restorations of the exoskeleton for Aphelaspis rara (Orłowski), Leptoplastides irae (Orłowski), Peltura protopeltorum Orłowski, and Trilobagnostus rudis (Salter) are provided. Large morphological variation in cephala of Parabolina (Neoparabolina) frequens (Barrande), observed in the literature and exemplified by the analysed material indicates that the hitherto recognised subspecies, P. (N.) frequens frequens (Barrande), P. (N.) frequens argentina (Kaiser) and P. (N.) frequens finnmarchica (Nikolaisen & Henningsmoen), represent one taxon. Parabolina (Neoparabolina?) lapponica Westergard is most probably related to Parabolina (Neoparabolina) frequens (Barrande). Beltella Lake is considered a junior synonym of Leptoplastides Raw, and the genus belongs to the Pelturinae rather than the Oleninae.
... They were designated the Mictosaukia, Missisquoia-Onychopyge, and kainellid-dominated faunas. Of particular interest is the occurrence of Missisquoia Shaw, 1951, inasmuch as the genus Missisquoia was for some time employed as an index fossil for recognizing the base of the Ordovician in North America (Winston and Nicholls, 1967;Stitt, 1971Stitt, , 1977Loch et al., 1993;Ross et al., 1997). However, the recently ratified global standard stratotype section and point (GSSP) for the Cambrian-Ordovician boundary was set at a slightly younger level at the lowest occurrence of the conodont Iapetognathus fluctivagus Nicoll et al., 1999(Cooper et al., 2001, thereby placing the Missisquoia Zone in the uppermost Cambrian (Miller et al., 2003). ...
... Certainly Missisquoia displays a variety of glabellar morphologies; e.g., forwardly tapering (M. typicalis Shaw, 1951) and bulging in the middle (M. inflata Winston and Nicholls, 1967). ...
The Pseudokoldinioidia Fauna is a newly documented uppermost Cambrian trilobite assemblage from the Dongjeom Formation of the Taebaek Group, Taebaeksan Basin, Korea. It is characterized by low species diversity comprising six trilobite taxa: Micragnostus chiushuensis, Koldinioidia typicalis, leiostegiid genus and species indeterminate, Pseudokoldinioidia perpetis, Onychopyge borealis, and pilekiid genus and species indeterminate. Of these, special attention has been paid to Pseudokoldinioidia perpetis, which was originally assigned to Missisquoia, an index fossil for the uppermost Cambrian in Laurentia. Pseatdokoldinioidia is restricted to eastern Asia, whereas Missisquoia is confined to Laurentia. The appearance of the Pseudokoldinioidia Fauna is interpreted as contemporaneous with the base of the `Missisquoia' perpetis Zone of North China, which in turn is correlated with the base of the Missisquoia typicalis Subzone of Laurentia. The associated Koldinioidia and Onychopyge make it possible to compare the Pseudokoldinioidia Fauna of Korea and North China with the latest Cambrian trilobite assemblages of South China, Australia, South America, and Mexico, and also suggests an interesting biogeographic connection among these areas in the latest Cambrian.
... Although sclerites of P. triarthroides were reported from the upper Cambrian of Vermont and the basal Ordovician of Texas (Shaw, 1951;Winston and Nichols, 1967), Rushton (1988) reconsidered their identity and removed them from the synonymy list of the species. In addition, Rushton (1988, text- fig. ...
The upper part of the Santa Rosita Formation (Ordovician, Tremadocian) in the Nazareno area, Cordillera Oriental, northwestern Argentina, records the vertical passage of high-energy, shallow water platform environments to offshore settings. Eighteen trilobite species are described from this locality for the first time. Although the taxa from the lower part of the succession ( Leptoplastides sp., Asaphellus sp.) are scarce and non-age diagnostic, those from the upper part include diverse assemblages partially assigned to the late Tremadocian Notopeltis orthometopa Zone. Systematic descriptions of several species ( Geragnostus nesossii Harrington and Leanza, G. callaveiformis Harrington and Leanza, Asaphellus jujuanus Harrington, Notopeltis orthometopa [Harrington], Mekynophrys nanna Harrington, Ceratopyge forficuloides Harrington and Leanza, Apatokephalus tibicen Přibyl and Vanĕk) are improved, the genus Nileus Dalman (including N. australis n. sp.) is first reported from the Tremadocian of western Gondwana, and new species of Asaphellus Callaway ( A. nazarenensis n. sp.), Conophrys Callaway, and Apatokephalus Brøgger are described. The trilobites have their closest affinities with faunas from Norway and Sweden. Notopeltis orthometopa and Mekynophrys nanna are restricted to the uppermost part of the succession, well above the first records of most other trilobites recognized.
... parva Raymond, 1937;S. corlissensis (Raymond, 1937); S. lata (Raymond, 1937); S. minima Shaw, 1951; S. sp. A and sp. ...
The Ibexian (Lower Ordovician) Symphysurina Zone has been subdivided into three subzones (in ascending order): the Symphysurina brevispicata, Symphysurina bulbosa and Symphysurina woosteri subzones. During deliberations over the selection of the GSSP for the base of the Ordovician System the base of the S. bulbosa Subzone was believed to closely approximate the First Appearance Datum (FAD) of the conodont Iapetognathus fluctivagus and the associated restricted occurrence of the cosmopolitan trilobite Jujuyaspsis. This correspondence allowed the approximate position of the Cambrian-Ordovician boundary in platform sequences of Laurentia to be determined on the basis of the endemic trilobite faunas. However, recent work has shown the tripartite division of the Symphysurina Zone to be untenable and, in particular, raised doubt regarding the suitability of the base of the S. bulbosa Subzone as a proxy for the base of the Ordovician System. This study describes four new species from the Cambrian-Ordovician boundary interval that are assigned to the Family Symphysurinidae. Symphysurina ethingtoni sp. nov. and Symphysurina straatmannae sp. nov. are recovered from the uppermost Cambrian. The genus Chasbellus gen. nov. is erected to include punctate symphysurinids that exhibit a concave pygidial border that extends posteriorly as a flat shelf. Two species are formally described: C. milleri (the type species) and C. repetskii, while a third is left in open nomenclature. All species of Chasbellus are restricted to the lowest Ordovician. Collectively, these species allow more confident distinction of the lower (Cambrian) from upper (Ordovician) portions of the Symphysurina Zone than was previously possible.
... Subfamilia PLICATOLININAE Robison y Pantoja-Alor, 1968 Género Plicatolina Shaw, 1951 AMEGHINIANA 44 (3) Material. Cuatro cranidios y 1 tórax (PIL 11403a-b, 14273a-c). ...
The Filo Azul Member of the Volcancito Formation (Famatina range, La Rioja, Argentina) consists of a lower part (30 m) of thinly laminated marls and calcareous shales with intercalations of fine-grained sandstones, a middle part (85 m) of massive middle to thick-grained calcareous sandstones, and an upper part (50 m) of shales with interbedded layers of fine sandstones. Previous studies on trilobites, graptolites and conodonts assigned the section to the Upper Cambrian-Lower Ordovician. The lower portion of the member (Parabolina frequens argentina Biozone, lower part) contains a diverse trilobite fauna that was studied by Harrington and Leanza in the 1950s. Since then, new collections have been obtained, which are the subject of the present study. New polymerid trilobites, originally described on the basis of scarce material, are re-illustrated (Onychopyge riojana Harrington, Asaphellus riojanus Harrington and Leanza, Rhadinopleura eurycephala Harrington and Leanza, Plicatolina scalpta Harrington and Leanza) and the assignations of several taxa are reconsidered (Angelina cf. hyeronimi (Kayser), Parabolinella sp. 1, Parabolinella sp. 2, Pseudokainella tosellii sp. nov., Conophrys sp.) (since the agnostoids have been recently revised, they are not included in this study). The fauna comprises several endemic species. On the other hand, the occurrence of Parabolina (Neoparabolina) frequens (Barrande) permits the outcrop to be correlated with other Upper Cambrian sections. The abundance of nutrients in the sea bottom must have favoured the development of a diverse trilobite community, which included different morphotypes and feeding habits. Several taxa were especially adapted to live under low-oxygen conditions, probably in symbiosis with sulfur bacteria.
... Family MISSISQUOllDAE Hupe, 1955 The family was restricted (Shergold, 1975;Ludvigsen, 1982) to include only Missisquoia Shaw, 1951and Parakoldinioidia Endo, 1937but Fortey (1983 considered these two genera as synonymous. He separated Lunacrania Kobayashi, 1955 within the family on the basis of "minute palpebral lobes well removed from the glabella". ...
... Subfamily PLICATOLININAE Robison & Pantoja-Alor, 1968 Plicatolina Shaw, 1951 Type species. Plicatolina kindlei Shaw, 1951 (original designation Plicatolina scalpta Harrington & Leanza, 1957 (Fig. 11J, K, L-part-) ...
... Although sclerites of P. triarthroides were reported from the upper Cambrian of Vermont and the basal Ordovician of Texas (Shaw, 1951;Winston and Nichols, 1967), Rushton (1988) reconsidered their identity and removed them from the synonymy list of the species. In addition, Rushton (1988, text- fig. ...
The upper part of the Santa Rosita Formation (Ordovician, Tremadocian) in the Nazareno area, Cordillera Oriental, northwestern Argentina, records the vertical passage of high-energy, shallow water platform environments to offshore settings. Eighteen trilobite species are described from this locality for the first time. Although the taxa from the lower part of the succession (Leptoplastides sp., Asaphellus sp.) are scarce and non-age diagnostic, those from the upper part include diverse assemblages partially assigned to the late Tremadocian Notopeltis orthometopa Zone. Systematic descriptions of several species (Geragnostus nesossii Harrington and Leanza, G. callaveiformis Harrington and Leanza, Asaphellus jujuanus Harrington, Notopeltis orthometopa [Harrington], Mekynophrys nanna Harrington, Ceratopyge forficuloides Harrington and Leanza, Apatokephalus tibicen Pribyl and Vanek) are improved, the genus Nileus Dalman (including N. australis n. sp.) is first reported from the Tremadocian of western Gondwana, and new species of Asaphellus Callaway (A. nazarenensis n. sp.), Conophrys Callaway, and Apatokephalus Brogger are described. The trilobites have their closest affinities with faunas from Norway and Sweden. Notopeltis orthometopa and Mekynophrys nanna are restricted to the uppermost part of the succession, well above the first records of most other trilobites recognized.
... Pseudorhaptagnostus (Pseudorhaptagnostus) sp. Lermontova, 1951 (e.g., Shaw, 1951;Shergold, 1977;Shergold et al., 1990;Nielsen, 1997). Although imperfect preser- vation prevents a species assignment, they can be confidently assigned to the "Bilobus group" of Shergold (1977), which is typically represented by Pseudorhaptagnostus bilobus (Shaw, 1951, pl. ...
Late Furongian (late Cambrian) trilobites are described from the black, deep water limestones of the El Relincho Formation in Cerro Pelado, Precordillera of Mendoza, western Argentina. In addition, selected type specimens of the Carlos Rusconi collections at the Museo de Ciencias Naturales y Antropologicas J.C. Moyano, (Mendoza) are revised. The assemblages are largely dominated by the agnostoid Lotagnostus peladensis (Rusconi), which proved to be a species with variably effaced dorsal furrows. Polymeroids include Mendoparabolina pirquinensis Rusconi, Hungaia peladensis Rusconi, and Loganellus cf. macropleurus Rasetti, as well as some fragmentary remains of uncertain affinities. Generic occurrences strongly support connections with Laurentia. Although the species identified are endemic to the southern Pre-cordillera, they mostly resemble faunas from the lower Saukia Zone of western North America, and the Onchonotus richardsoni and Keithia subclavata faunas of eastern Canada and USA.
... Lee et al. (2008) published a paper discussing the Missisquoiidae family of trilobites. The type genus of Missisquoiidae, Missisquoia Shaw, 1951, was viewed as an important marker taxon for defining the base of the Ordovician System (Lee et al., 2008). Originally confined to Laurentia, Missisquoia was later discovered in North China and Korea. ...
Systematic biostratigraphy is based on the exclusive use of monophyletic marker taxa. Non-monophyletic, or artificial, marker taxa have been shown to change biostratigraphic correlations, a situation that can be rectified by using systematics to ensure that marker taxa are monophyletic or natural. Both hypothetical and real examples demonstrate the validity of the methodology. The foraminiferal genera Praemurica and Parvularugoglobigerina are examples of non-monophyletic marker taxa. Cladistic results permit the reclassification of both genera, and a revision of foraminiferal biostratigraphy. Systematic biostratigraphy ensures the use of monophyletic marker taxa, preventing artificial classifications from hindering biostratigraphic correlations and producing more accurate, and stable, biostratigraphic zonations.
... Jujuyaspis and Parabolinella frrst appear in the lower Tremadocian of South America and Scandinavia (Henningsmoen 1957) and British Columbia (Kobayashi, 1955). Parabolinella occurs in the North American Missisquoia Zone in Vermont (Shaw, 1951), Nevada (Taylor, 1976), and Texas (Winston and Nicholls. 1967). ...
The conodont form species Cordylodus proavus Müller, 1959, occurs in the Acado-Baltic faunal province below the Cambrian-Ordovician (Olenidian-Tremadocian Series) boundary on Navy Island, New Brunswick, Canada. Its lowest occurrence in the North American faunal province is in the uppermost Cambrian Corbinia apopsis Subzone of the Saukia Zone. These data, combined with the appearance of the olenid trilobites Jujuyaspis and Parabolinella in the Acado-Baltic lower Tremadocian and in the North American lowermost Ordovician Missisquoia and Symphysurina Zones, suggest but do not prove an approximate equivalency of the Cambrian-Ordovician boundary in the two faunal provinces.
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.
In the Argentinian Cordillera Oriental, the Iturbe River area represents an intermediate territory between Sierra de Santa Victoria to the north and the Quebrada de Humahuaca to the south. Lower Ordovician outcrops of this region were cited in the literature as highly fossiliferous, although they are still imperfectly known. A Tremadocian succession of the Santa Rosita Formation near the village of Iturbe, Jujuy Province, is described herein. It displays different marine paleoenvironments and a relatively high-diversity trilobite assemblage. The sedimentary features of the lower and middle parts of the succession denote deposition in upper offshore and offshore transition environments, whereas those of the upper part are characteristic of a deeper, lower offshore setting. Taxa recognized include Gymnagnostus sp., Micragnostus iturbensis sp. nov., Geragnostus callaveiformis Harrington and Leanza, Geragnostus sp., Conophrys cf. salopiensis (Callaway), Leptoplastides granulosus (Harrington), Bienvillia tetragonalis (Harrington), B. rectifrons (Harrington), Parabolinella boliviana Juarez Huarachi, Asaphellus stenorhachis (Harrington), Apatokephalus tibicen Přibyl and Vaněk, and Pyrimetopus sp. This association indicates correspondence with the Bienvillia tetragonalis Zone (lower upper Tremadocian); a unit that to date is recorded with confidence only in a few localities of the Cordillera Oriental, in diverse facies. This study provides information on the morphology of several key taxa of the biozone, as well as new evidence in favour of a correlation with the Conophrys salopiensis Zone of England. The assemblage studied is assignable to the middle Tremadocian Olenid-Asaphellus biofacies, which occurs typically in upper offshore to offshore transition deposits.
A comprehensive review and phylogenetic analysis of genera and species presently assigned to the rhyn-chonelliform superfamily Nisusioidea and family Nisusiidae suggests that this short-lived but important group of bra-chiopods first appeared in peri-Gondwana during the second half of the Cambrian Series 2, before going extinct by the end of Drumian times. Nisusiides achieved their maximum morphological disparity and geographical distribution during the Wuliuan Age, and Laurentia was probably the major centre of their dispersal. A new phylogenetic analysis suggests an early separation of the lineages of spinose and non-spi-nose nisusiids. The non-spinose nisusiids probably evolved in Laurentia by the end of Cambrian Series 4. The new nisusiid genus Bellistrophia is described. The new species Nisusia multicostata represents the first documented rhyn-chonelliform (kutorginide) brachiopod from the Miaolingian (Drumian) of the Alborz Mountains, Iran.
The Olenidae stands out for its abundance and biostratigraphical importance, especially in the Lower Palaeozoic rocks of northwestern Argentina. Their phylogenetic relationships have been traditionally determined stratigraphically and by direct morphological comparison. This study reports the first formal phylogenetic analysis of olenids. Eighty‐six characters (24 quantitative and 62 qualitative) were coded for 65 taxa (58 olenids). Quantitative characters were treated both as discrete and as continuous variables. To explore the best way of character coding for this group, continuous characters were coded as: median, log‐median, normalized and rescaled. Maximum parsimony and implied weighting were used as optimality criteria. A phylogenetic hypothesis more consistent with traditional taxonomy was reconstructed with both quantitative and qualitative partitions. All the trees obtained with quantitative characters coded as continuous and rescaled are better resolved, and those topologies were more similar among them. This treatment also reflects more effectively the behaviour of the original variables. Olenidae is not a monophyletic clade: Andrarina costata and Aphelaspis australis are included within the ingroup, as sister clade of Olenus gibbosus. Also, the results suggest that members of the Hypermecaspidinae constitute a new family within the Order Olenida. The traditional taxonomic scheme at subfamily level is partially supported. Triarthrinae and ‘pelturinds’ are recovered as monophyletic clades, but Oleninae is polyphyletic. This study proves, through a formal cladistic analysis, that characters disregarded by traditional taxonomy can be uncovered. Finally, this is the first step towards achieving a classification of the Olenidae taking into account the evolutionary process involved in its diversification history.
Cambrian genera and species of Agnostina (?Trilobita) found in Russia are revised. Agnostid trilobite species are used as index taxa in chronostratigraphic subdivisions of the traditional Middle and Upper Cambrian in both regional and global stratigraphic scales. The correlation of the regional and international stratigraphic schemes largely depends on the state of knowledge of the regional agnostid fauna. Therefore, an up-to-date revision of this group based on the Russian collections taking into account their global diversity is very timely. For this study we reexamined the type collections of agnostids, including the holotypes of species described by Russian authors. This paper contains new photographic images of the holotypes housed in Russian museums. The compiled data offered solutions for some difficult taxonomic problems of the families Agnostidae, Ptychagnostidae, Peronopsidae, and some genera of Pseudagnostidae, Diplagnostidae. Apart from listing the diversity, this paper serves as the basis for studying the biogeography and evolution of this interesting arthropod group.
The late Cambrian-Early Ordovician sequences of the Cordillera Oriental in northwestern Argentina are extensive and highly fossiliferous. The olenid trilobite Parabolinella argentinensis Kobayashi sensu Harrington and Leanza, 1957 was reported from a great number of Tremadocian localities and includes a wide range of morphologies. Based on specimens collected from the type locality (Purmamarca, Jujuy) and the quebrada Moya (Huacalera, Jujuy), as well as on material of the Harrington and Leanza collections in the University of Buenos Aires, classic morphometry and geometric morphometry methods were used to evaluate the variability in the cranidium of P . argentinensis . The results obtained from the two methodologies are similar. Both analyses allowed the review of the diagnosis of P . argentinensis , and the distinction of two new morphologies: Parabolinella clarisae n. sp. and Parabolinella pompadouris n. sp. The results show how morphogeometrics distinguishes more clearly the three morphotypes and provides graphical representations of the differences between those groups and how from the representations plus the correlation between classical variables and principal components, new diagnostic characters that distinguish the three morphospecies, can be identified.
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.
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.
The strata and fossils between the Cambrian and Ordovician boundany outcropping in the northwest region of the Sandu district are transitional both in biofacies and lithofacies. Two sections, about 8 km apart, were measured. One at Pu’an, here the late Upper Cambrian Maotian Formation contains dolomites, limestones, argillaceous dolostones, dolomitic and sandy mudstones with about 75% non-agnostid trilobites of the Yangtze Subprovince of the North China Faunal Province, 16.7% of the Jiangnan Subprovince of the Southeast China Faunal Province and 8.3% of endemic forms; while the early Tremadocian Guotang Formation is chiefly composed of striped dolostones and argillaceous dolostones bearing 22.2% non-agnostid trilobites of the Yangtze Subprovince, 72.2% of the Jiangnan Subprovince and 5.6% of the endemic elements. In the other section at Shizilu, the late Upper Cambrian Sandu Formation consists of thin-bedded striped argillaceous dolostones, calcareous mudstones, arenaceous dolostones and limestones with about 20% nonagnostid trilobites of the Yangtze Subprovince, 70% of the Jiangnan Subprovince and 10% of endemic forms; whereas the early Tremadocian Guotang Formation is almost entirely composed of thin-bedded striped argillaceous dolomites with very few mudstones containing 12.5% non-agnostid trilobites of the Yangtze Subprovince and 87.5% of the Jiangnan Subprovince. 57 species and 33 genera and subgenera of trilobites are described, among them, 18 species, 3 genera and 2 subgenera are new.
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.
The Lampazar Formation is well exposed in the northern part of Cajas Range, at the Azul and Llama Creeks (Jujuy, Eastern Cordillera, Argentina). It is mainly composed of shales and subordinate sandstones representing an outer shelf setting with some transitions to shallower environments. Oxygen and energy levels were not uniform during deposition: fine grained sediments vary from laminated black and dark grey shales (Facies 1 and 2) in the lower part of the formation to laminated greenish shales (Facies 3) with intercalations of siltstones and sandstones (Facies 4-7) in the middle and upper parts. The unit contains the trilobites Lotagnostus (Distagnostus) sp., Gymnagnostus bolivianus (Hoek in Steinmann and Hoek), Gymnagnostus perinflatus (Harrington and Leanza), Micragnostus vilonii Harrington and Leanza, Pseudorhaptagnostus (Machairagnostus) tmetus Harrington and Leanza, Pseudorhaptagnostus (Machairagnostus) corrugatus (Suárez-Soruco), Akoldinioidia sp., Parabolina (Neoparabolina) frequens argentina (Kayser), Angelina hyeronimi (Kayser), Parabolinella coelatifrons Harrington and Leanza, Beltella ulrichi (Kayser), Plicatolina scalpta Harrington and Leanza, and Asaphellus cf. aspinus Robison and Pantoja-Alor. Some agnostoids previously described from the Azul Creek are revised here. Trilobites are assignable to the lower part of the Parabolina frequens argentina Biozone (Pseudorhaptagnostus-Gymnagnostus subzone; latest Cambrian). Olenid-agnostoid assemblages are especially diverse in dark shales, corroborating the suggestion that these faunas were especially adapted to low-oxygen-water bottom conditions. The Lampazar Formation in Cajas Range is correlated with the lower part of the Volcancito Formation (Famatina Range).
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.
A consolidated list of available generic names introduced since the beginning of the binomial nomenclature system for trilobites is presented for the first time. Each entry is accompanied by the author and date of availability, by the name of the type species, by a lithostratigraphic or biostratigraphic and geographic reference for the type species, by a family assignment and by an age indication of the type species at the Period level (e.g. MCAM, LDEV). A second listing of these names is taxonomically arranged in families with the families listed alphabetically, higher level classification being outside the scope of this work. We also provide a list of names that have apparently been applied to trilobites but which remain nomina nuda within the ICZN definition.
The trilobite fauna of the upper Tremadoc Bjorkasholmen Formation in the Oslo Region is revised and redescribed, recognizing 36 species assigned to 28 genera. The regional and vertical distribution of the trilobite fauna are also discussed. The Bjorkasholmen Formation is found in the Lower Allochthon of the Synfjell Nappe and across the Oslo Region in Norway. In Sweden it crops out in Vastergotland, Scania and on Oland. Generally the unit is 60-120 cm thick, comprising micritic to intrasparitic limestone composed of several individual limestone beds, covering the Zone of Apatokephalus serratus. Near the base of the formation a horizon consisting of dark limestone nodules appears, containing a trilobite fauna dominated by Bienvillia angelini. This level is found throughout the studied area and is an important correlatable horizon. New material of rare species, such as Peltocare modestum Henningsmoen, 1959, Parabolinella lata Henningsmoen, 1957, Falanaspis aliena Tjernvik, 1956, Harpides rugosus (Sars and Boeck, 1838) and Parapilekia speciosa (Dalman, 1827), is described and figured. Orometopus elatifrons (Angelin, 1854) is recognized as distinctly different from British material formerly assigned to this taxon. Three new species are described, Saltaspis stenolimbatus n.sp., Apatokephalus dactylotypos n.sp., and Niobe (Niobella) eudelopleura n.sp. Additionally, the species Apatokephalus cf. sarculum Fortey and Owens 1991 from the upper part of the Alum Shale Formation is described. Biostratigraphical studies were carried out at six localities distributed across the Oslo Region. A relative-abundance distribution shows that Ceratopyge acicularis dominates the lower limestone beds above the dark limestone nodules and is followed by a small acme of Apatokephalus serratus, then a dominance of Euloma ornatum, and, finally, Symphysurus angustatus in the uppermost fossiliferous beds of the formation. Species of the large asaphid Niobe are present throughout the unit in relatively constant numbers. The remaining species are present in limited numbers. Older views claiming a greater diversity in the Oslo-Asker district compared to the rest of the Oslo Region are erroneous. All data suggest a coherent distribution and diversity across the Oslo Region, with local variations.
Phylogenetic relationships among species of the family Olenidae (Trilobita, Ptychopariida) were traditionally established by the direct comparison of morphological features and the evaluation of stratigraphic placement. In this study, a cladistic analysis of Parabolinella Brøgger is conducted in order to test the supposed monophyly of the genus and to determine the relationships of its species. Twenty-one taxa (sixteen of this genus) from the late Cambrian and Tremadocian of Baltica, Avalonia, Laurentia, South China and the western margin of Gondwana were revised. Forty non-ordered characters were considered in the analysis, 34 belonging to the cephalon, four to the pygidium, and two to the thorax. Some of these characters were specially defined for this study. The phylogenetic analysis was performed under unweighted parsimony. The obtained tree is partially consistent with the stratigraphic record of the studied species and shows correspondence with global late Cambrian and early Ordovician palaeogeography. Parabolinella may have originated in deep water sites of the Oaxaca region, Mexico and then migrated to other regions. The genus diversified in outer shelf facies of the Baltica Province during the late Cambrian and Tremadocian, whereas it would have dispersed to the South China Province in early Tremadocian times. Copyright © 2012 John Wiley & Sons, Ltd.
Tangshanaspis Zhou and Zhang, 1978 (Family Missisquoiidae), has been reported widely from western North America and has been assigned invariably to a single species, T. depressa (Stitt, 1971b). The base of the T. depressa Subzone as defined in Oklahoma is an important biostratigraphic datum for inter-regional correlation of uppermost Cambrian strata. Study of previously undescribed material in collections from Oklahoma shows that T. depressa is, in fact, a composite of cranidia and pygidia that belong to two stratigraphically segregated species in the Signal Mountain Formation. Tangshanaspis silveri n. sp. includes the pygidial morph originally attributed to T. depressa. Revision of the species from Oklahoma allows definition of a new biostratigraphic unit, the Tangshanaspis Zone, which is divided into a lower T. silveri Fauna and an overlying T. depressa Fauna; in addition to the eponymous species, the T. depressa Fauna includes pygidia that represent two additional species of Tangshanaspis that are placed in open nomenclature. Correlation with other areas suggests that the “Missisquoia” mackenziensis Fauna of northern Canada may be equivalent to the T. silveri Fauna of Oklahoma, rather than a pre-Tangshanaspis interval that is unrepresented elsewhere in Laurentian North America.
This study illustrates the usefulness of carbon isotopes in stratigraphic interpretations of poorly fossiliferous strata beyond the resolution possible by biostratigraphy. The Upper Cambrian strata of the lower Gorge Formation in northwestern Vermont have been interpreted as highly condensed continental-slope deposits with a hiatus bracketed by the trilobite fauna of the Dunderbergia zone (Steptoean) and the Saukia zone (upper Sunwaptan). This interpretation was based on information from two thin fossiliferous intervals, the occurrence of one of them being unconfirmed in a recent study. Carbon isotopes provide a means for testing this interpretation because marine carbonate rocks deposited during the Steptoean Age of the Late Cambrian record a large, global, positive carbon isotope excursion (delta13C values of up to +50/00 relative to the Vienna Peedee belemnite standard). If the proposed age for the lowermost Gorge Formation is correct, these strata should record the start of the excursion, and the hiatus should produce an abrupt termination in the record of the excursion near maximum values. The determined delta13C values (-0.570/00 to +0.390/00) indicate that the excursion is not recorded at this locality. The results question the age for these strata and suggest that the hiatus is greater than previously recognized, encompassing most of the Steptoean. This major sedimentary hiatus lends supporting evidence for a significant eustatic or pan-Laurentian sea- level event during the Steptoean perturbation in the global cycling of carbon.
Regional biofacies analysis has been neglected in biostratigraphic studies of the Cambrian-Ordovician boundary interval. Cluster analysis of relative abundance data of trilobites in thirty-seven large collections from ten localities in North America outlines eleven biofacies in the mid-Trempealeauan to early Tremadocian interval. The biofacies are largely lithofacies-specific and are differentiated at generic and familial levels. The composition of trilobite zonal associations in the boundary interval is controlled principally by the sequence of biofacies. Available trilobite zonal schemes can be used only within single lithofacies. The biofacies patterns and faunal dynamics across the upper boundary of the Ptychaspid Biomere do not support hypotheses requiring catastrophic events. In coherence and geographic distribution, Late Cambrian trilobite biofacies are similar to post-Cambrian benthic biofacies.
Forty‐one species of trilobites and two of graptolites are described from the Patriarch Formation and the overlying Summit Limestone of the northwest Nelson area, New Zealand. Most of the trilobites are recorded for the first time from Australasia. The stratigraphy of both formations is revised and stratigraphic columns presented. Five successive faunules, shown to span the Cambrian‐Ordovician boundary, are recognised in the sequence, and are correlated internationally. Stratigraphically important conodonts from the area are figured and briefly discussed. Faunule 1, in the lower 220 m of the Patriarch Formation, contains the Lotagnostus‐Hedinaspis‐Hysterolenus trilobite fauna, which is found around the world in Late Cambrian strata. Twenty‐three trilobite species occur, including three new species: the aulacopleurid Proteuloma ahu, the shumardiid Shumardia (Conophrys) tauwhena, and the nepeid Amzasskiella kupenga. Faunule 2, from the upper 250 m of the Patriarch Formation, contains the graptolites Rhabdinopora ex gr. scitulum and Anisograptus cf. dclicatulus, and the conodonts Cordylodus angulatus, Oistodus lanceolatus, TAcanthodus costatus, and Hirsutodontus simplex, together with five species of trilobites. The conodonts and graptolites indicate an early Tremadoc age. Faunule 3, from the lower 64 m of the Summit Limestone, contains 18 species of trilobites, including one new species, Leptoplastides grindleyi, as well as the South American taxa Kainella meridionalis Kobayashi, 1935, Apatokephalus sp. aff. A. tibicen Pribyl & Vaněk, 1980, and Onychopyge sp. aff. O. riojana Harrington, 1938 indicating a late Tremadoc age. The lower of the two conodont faunules described by Cooper and Druce from Unit 1 of the Summit Limestone, constitutes Faunule 4, and is here assigned a late Tremadoc age; their upper conodont faunule, from Unit 3 of the Summit Limestone, constitutes Faunule 5 (early Arenig).Faunule 3 has generic links with South America but, overall, cosmopolitan genera dominate the trilobite assemblages and, especially in Faunule 1, faunal composition reflects biofacies rather than paleogeography. The environments inferred for the Anatoki Formation and lower Patriarch Formation are a turbidite fan or basin in an off‐shelf setting; subsequent “shallowing is indicated by carbonate development near the top of the Patriarch Formation, and further shallowing, to shelf depths, is indicated by the Summit Limestone and its trilobite fauna.
Fifty‐four trilobite taxa from 15 new localities in the Bowers Terrane of Northern Victoria Land, including the first fossils from Molar Formation, are described. The fossils indicate an age range from late Middle Cambrian (Boomerangian or older) to mid Late Cambrian (late Idamean). At Reilly Ridge, the Spurs Formation crops out in a number of fault‐bounded slices; the new fossils indicate marked lateral facies contrasts between slices and suggest considerable lateral displacement along the bounding faults. At Houliston Glacier, trilobites of Mindyallan age in Molar Formation imply that the boundary between the Molar and Spurs Formations is strongly time transgressive. New species described in this paper are Reillopleura braddocki gen. et sp. nov. and Notoaphelaspis horizontalis sp. nov. Faunal affinities are mainly with the Ellsworth Mountains (West Antarctica), western Queensland, and China.
Pseudagnostus rugosus Ergaliev, 1980 is described from the Furongian Ctenopyge tumida Zone at Gislövshammar, Scania, southern Sweden. This is the first record of this distinctive agnostoid in Scandinavia. The species is known previously from Malyi Karatau, Kazakhstan, and northwestern Hunan and western Zhejiang, South China, and provides a newly recognized link between middle–upper Furongian successions in Baltica, Kazakhstan and South China. The occurrences of P. rugosus allow a correlation between the C. tumida Zone of Baltica, the lower Eolotagnostus scrobicularis–Jegorovaia Zone of Kazakhstan and the lower Lotagnostus americanus Zone of South China.
The protaspides of Missisquoia depressa (Missisquoiidae, Trilobita), from the uppermost Cambrian part of the Rabbitkettle Formation, Mackenzie Mountains, northwestern Canada, are described. Three metaprotaspid stages are recognized, using size as well as features of the anterior border of the cranidium and the shape of the glabella. The morphology of the protaspides is not typical of the Order Corynexochida, suggesting that Missisquoia is not a member of the order to which the genus has been previously assigned. This further indicates that its affinity to the stratigraphically younger styginids and illaenids is questionable.
We propose a candidate for the Global Standard Stratotype-section and Point (GSSP) for the base of the highest stage of the Furongian Series of the Cambrian System. The section is at Lawson Cove in the Ibex area of Millard County, Utah, USA. The marker horizon is the first appearance datum (FAD) of the conodont Cordylodus andresi Viira et Sergeyeva in Kaljo et al. [Kaljo, D., Borovko, N., Heinsalu, H., Khazanovich, K., Mens, K., Popov, L., Sergeyeva, S., Sobolevskaya, R., Viira, V., 1986. The Cambrian–Ordovician boundary in the Baltic–Ladoga clint area (North Estonia and Leningrad Region, USSR). Eesti NSV Teaduste Akadeemia Toimetised. Geologia 35, 97–108]. At this section and elsewhere this horizon also is the FAD of the trilobite Eurekia apopsis (Winston et Nicholls, 1967). This conodont characterizes the base of the Cordylodus proavus Zone, which has been recognized in many parts of the world. This trilobite characterizes the base of the Eurekia apopsis Zone, which has been recognized in many parts of North America. The proposed boundary is 46.7m above the base of the Lava Dam Member of the Notch Peak Formation at the Lawson Cove section. Brachiopods, sequence stratigraphy, and carbon-isotope geochemistry are other tools that characterize this horizon and allow it to be recognized in other areas.
Two completely dissimilar faunal changes occur between the Sunwaptan and Skullrockian Stages (Ptychaspid and Symphysurid ‘Biomeres’) in the uppermost Cambrian on the east Laurentian craton. An undolomitized section in the Little Falls Formation in Washington County, New York, shows a typical ‘biomere’ extinction, with highest Sunwaptan trilobites followed by the abrupt appearance of Cordylodus proavus Zone conodonts and the lowest post-extinction trilobites (Parakoldinioidia Endo) 5.0 m higher. This stage boundary interval is very condensed by comparison with coeval Great Basin and Texas sections. Approximately 70 km southwest, typical pre-extinction taxa (the catillicephalid Acheilops Ulrich and several dikelocephalid species) are shown for the first time to persist well beyond the extinction as they occur with middle C. proavus Zone conodonts (Clavohamulus elongatus or, more likely, Hirsutodontus simplex Subzone). The Ritchie Limestone member of the uppermost Little Falls Formation yields a succession of conodont faunas that spans the C. elongatus–H. simplex–Clavohamulus hintzei Subzones (middle–upper C. proavus Zone). These data prove that the trilobites are a relict fauna that persisted into the Symphysurina Zone of the Skullrockian Stage. The massive (burrow-churned), mollusc-dominated Ritchie Limestone, with the second Upper Cambrian cephalopod locality in east Laurentia, represents an inner-shelf refugium for Sunwaptan trilobites that has not been previously encountered. Final extinction of typical Sunwaptan clades is at least locally diachronous, and a simple, genus-based approach to trilobite biostratigraphy in the Cambrian–Ordovician boundary interval is untenable. The relict fauna appears to be distinct at the species level, so it is likely that a viable, species-based biostratigraphy can be developed. Teridontus gallicus Serpagli et al. 2008 is a synonym of T. nakamurai (Nogami, 1967), and T.? francisi Landing sp. nov., with a large base and tiny cusp, is a lower C. proavus Zone form. New trilobites are Acheilops olbermanni Westrop sp. nov. and Parakoldinioidia maddowae Westrop sp. nov. The lowest Ordovician ‘Gailor Dolomite’ is a junior synonym of the Tribes Hill Formation, and the Ritchie Limestone is assigned to the top of the terminal Cambrian Little Falls Formation.
The definition and scope of Ordovician genera of agnostid trilobites are discussed, and the generic affiliation of Ordovician species and well-illustrated material referred to in open nomenclature is assessed. Some 198 Ordovician species plus 25 species of uncertain latest Cambrian/earliest Ordovician age are enumerated, representing 24 genera and subgenera, of which Geragnostus (Novoagnostus) n.subg. and Lotagnostus (Semagnostus) n.subg. are new. Geragnostella is ranked as a subgenus of Geragnostus. The species of Arthrorhachis are tentatively divided among a tardus species group and an elspethi species group. Species of Dividuagnostus are divided among a sensu stricto group and an early species group. Pseudorhaptagnostus Lermontova, 1951 is restored as senior synonym of Neoagnostus Kobayashi, 1955. It is concluded that Ordovician agnostids were largely adapted to temperate and colder water habitats.
Detailed analysis of trilobite assemblages at the Cambrian–Tremadoc transition reveals the presence of four, possibly five, biogeographic provinces: Baltic, North China, Southeast China, North American, and possibly Siberian. One or more discrete biofacies characterize the transition in each province. When plotted palaeogeographically these appear to be largely temperature controlled. Interdigitation of provincialized trilobite biofacies is recognized by the representation of dominant types of trilobite, olenaceans, ceratopygaceans, remopleuridaceans, dikelocephalaceans and leio-stegiaceans in particular, on key boundary sections. These sections, at Nochixtlán, Mexico; Batyrbay, southern Kazakhstan; Broken Skull River, District of Mackenzie, Canada; and Jiangshan–Chang-shan, western Zhejiang, China, permit the correlation of biogeographic provinces globally. As a result of the application of trilobite biostratigraphy relatively few problems prevent the maintenance of a Cambrian–Ordovician Boundary stratotype section in its traditional Baltic biogeographic setting.
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