Journal articles: 'Corynexochida'

1

Geyer, Gerd. "Cambrian corynexochid trilobites from Morocco." Journal of Paleontology 68, no. 6 (November 1994): 1306–20. http://dx.doi.org/10.1017/s0022336000034296.

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Corynexochid trilobites of the Cambrian of Morocco are described and the subfamily Acontheinae is revised. With Kootenia beethoveni n. sp., Kootenia spp. indet., Strettonia sp. A, Clavigellus annulus n. gen. and sp., and gen. et sp. incert., the Moroccan Corynexochida comprise only a few forms that are almost exclusively restricted to the High Atlas Mountains. Biogeographical relationships are weak; strong relationships may exist with the faunas of the Shropshire area as already exemplified by some eodiscid and ellipsocephalid taxa.

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Holloway, David J. "Middle Silurian trilobites from Arkansas and Oklahoma, USA. Order Corynexochida." Palaeontographica Abteilung A 319, no. 1-6 (August 27, 2021): 1–55. http://dx.doi.org/10.1127/pala/2021/0101.

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3

Sundberg, Frederick A. "Phylogenetic Analysis of the Spiny Oryctocephalids (Trilobita, Corynexochida?, Oryctocephalidae), Cambrian." Journal of Paleontology 88, no. 3 (May 2014): 556–87. http://dx.doi.org/10.1666/12-130.

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Phylogenetic analyses of the Cambrian spiny oryctocephalids support the elevation to familiar rank of Oryctocephalidae Beecher, 1897 and indicate that the family can be divided into two clades, here designated as the subfamilies Oryctocephalinae Beecher, 1897 and Lancastriinae Kobayashi, 1935. Curvoryctocephaliinae Zhao and YuaninYuan et al., 2002 is considered here a junior synonym of Lancastriinae. Oryctocephalinae have tapered or parallel sided glabella and is composed of species ofOryctocephalusWalcott, 1886. The subgeneraOryctocephalus(Oryctocephalus) andO. (Eoryctocephalus) Zhao and YuaninYuan et al., 2002 do not form separate clades and are here rejected.The genera of the Lancastriinae have expanding glabellae. The subfamily is composed of a broad variety of genera that can be divided into three major subclades:Lancastria,Protoryctocephalus, andOryctocephalites. TheLancastriasubclade is composed ofLancastriaKobayashi, 1935,ChangaspisLeeinChien, 1961, andGoldfieldiaPalmer, 1964 occurring at the base of the Lancastriinae.GoldfieldiaandLancastriaform a sister group toChangaspis. The long branches in the phylograms indicated significant differences between these taxa; thus, the genusGoldfieldiais maintained. TheProtoryctocephalussubclade is monogeneric and forms a sister group to theOryctocephalitessubclade. TheOryctocephalitessubclade consists of several species of this genus and the more derived formsMetabalangiaQian and YuaninZhang et al., 1980 andTonkinellaMansuy, 1916.OryctocephaloidesYuaninZhang et al., 1980 is considered a junior synonym ofOryctocephalitesResser, 1939. The subgeneraOryctocephalites(Oryctocephalites) andO. (Parachangaspis) Zhao and YuaninYuan et al., 2002 do not form separate clades. The later subgenus occurs in the basal portion of theOryctocephalitessubclade indicating that it is a paraphyletic taxon.OpsiosoryctocephalusSundberg, 1994,OryctocephalopsLermontova, 1940, andCurvoryctocephalusZhao and YuaninYuan et al., 2002 are not consistent in their placement within the phylogenetic analyses, although they always occur in the Lancastriinae. As a result they are not placed within a subclade within Lancastriinae.The type speciesGoldfieldia pacificaPalmer, 1964 was based solely on cranidia. This species is redescribed using topotype material that includes cranidia, librigenae, hypostomes, thorax, and pygidia.

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Lee, Dong-Chan, and Brian DE Chatterton. "Protaspides of uppermost Cambrian trilobite Missisquoia, with implications for suprafamilial level classification of the genus." Canadian Journal of Earth Sciences 44, no. 4 (April 1, 2007): 493–506. http://dx.doi.org/10.1139/e06-113.

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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.

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Basse, Martin. "Middle Devonian trilobites of the Rhenohercynian: I. Corynexochida and Proetida (1)." Palaeontographica Abteilung A 239, no. 4-6 (July 5, 1996): 89–182. http://dx.doi.org/10.1127/pala/239/1996/89.

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Lee, Dong-Chan, and Brian D. E. Chatterton. "Protaspides of Leiostegium and their implications for membership of the order Corynexochida." Palaeontology 46, no. 3 (May 2003): 431–45. http://dx.doi.org/10.1111/1475-4983.00306.

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7

Sundberg, Frederick A. "Corynexochida and Ptychopariida (Trilobita, Arthropoda) of the Ehmaniella Biozone (Middle Cambrian), Utah and Nevada." Contributions in science 446 (August 12, 1994): 1–137. http://dx.doi.org/10.5962/p.208082.

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8

Sundberg, Frederick A., and Linda B. Mccollum. "Oryctocephalids (Corynexochida: Trilobita) of the Lower-Middle Cambrian boundary interval from California and Nevada." Journal of Paleontology 71, no. 6 (November 1997): 1065–90. http://dx.doi.org/10.1017/s0022336000036040.

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Seven species of oryctocephalids occur in the Lower to Middle Cambrian boundary strata of the southern Great Basin. These include Oryctocephalites palmeri n. sp. and an Oryctocephalinae species from the uppermost Lower Cambrian (upper Olenellus Biozone); Oryctocephalus indicus (Reed, 1910), Microryctocara nevadensis n. gen. and n. sp., and Oryctocephalites rasettii n. sp. near the base of the Middle Cambrian (lower Plagiura Biozone); and Oryctocephalus primus Walcott, 1886, and Oryctocephalus nyensis Palmer, 1979, from slightly higher strata (upper Plagiura Biozone). Oryctocephalus and Oryctocephalites are emended based on a cladistic analysis of Oryctocephalinae Beecher, 1897.

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9

Lei, Qianping. "New ontogenetic information onDuyunaspis duyunensisZhang & QianinZhouet al., 1977 (Trilobita, Corynexochida) from the Cambrian and its possible sexual dimorphism." Alcheringa: An Australasian Journal of Palaeontology 40, no. 1 (September 16, 2015): 12–23. http://dx.doi.org/10.1080/03115518.2015.1069485.

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10

Fortey, Richard A. "Trilobite systematics: The last 75 years." Journal of Paleontology 75, no. 6 (November 2001): 1141–51. http://dx.doi.org/10.1017/s0022336000017194.

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The progress achieved in trilobite systematics over the last 75 years is briefly reviewed. Different approaches to phylogenetics have influenced the way trilobites have been classified. Classical evolutionary taxonomy, the stratigraphical approach, and cladistics have all contributed in different ways to the current classification, which has evolved piecemeal, and is still unsatisfactory is some ways. Nonetheless, progress towards a phylogenetic classification has been made, especially as the result of information from ontogenies provided by well-preserved silificified material. Trilobites are a well-defined clade within a larger arachnomorph group. Agnostida have been excluded from Trilobita, but are perhaps best considered as specialised trilobites, at least until limbs of eodiscids are described. The outstanding problems in classification of each trilobite order are reviewed. Most are concerned with the recognition of the appropriate Cambrian sister taxa, and the discovery of the relevant ontogenies. It is very likely that post-Cambrian clades “root” deeply into the Cambrian. The coherence, or otherwise, of Proetida, Asaphida, Corynexochida and the lichid/odontopleurid groups will be resolved by such studies. The problems of paraphyly in Ptychopariida and Redlichiina may prove more obdurate. The temporal brevity of certain Cambrian family ranges may be partly a taxonomic artefact. The possibility of a late Cambrian gap in the record on some clades should be considered.

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Whittington, Harry B. "The Corynexochina (Trilobita): a poorly understood suborder." Journal of Paleontology 83, no. 1 (January 2009): 1–8. http://dx.doi.org/10.1017/s002233600005808x.

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Trilobites of this suborder from Europe and North America have not been studied in detail, in contrast to the attention given to relationships within the orders Agnostida and Ptychopariina. The basis of the Corynexochina is the type species of Corynexochus from the middle Cambrian of Sweden. The type material redescribed here is only the cranidium, and is inadequate for diagnosis of the genus. A species attributed to this genus occurring in the Cambrian of southern France is represented by entire dorsal exoskeletons and is urgently in need of redescription. Similar material is recorded in northern Spain. Both complete exoskeletons and growth stages of Corynexochina have been described from Cambrian strata in Russia, Australia, Morocco and China, showing the wide geographical range and varied morphology of the Suborder. The type species of two genera from boulders of middle Cambrian age found in Quebec, Canada, are redescribed from exceptionally well preserved, though small, specimens. They appear to represent a distinct group related to some of the Zacanthoididae. Families of Corynexochina are inadequately discriminated one from another, so that a family name can only be used with question. Until this is remedied, diagnosis of a new group is not possible.

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12

Chatterton, B. D. E., D. J. Siveter, G. D. Edgecombe, and A. S. Hunt. "Larvae and relationships of the Calymenina (Trilobita)." Journal of Paleontology 64, no. 2 (March 1990): 255–77. http://dx.doi.org/10.1017/s0022336000018424.

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Up to four discrete protaspid larval stages are described for calymenid trilobites of Ordovician to Devonian age. The earliest growth stages are nonadult-like planktonic protaspides; later protaspides are adult-like and benthonic. In contrast, the related homalonotid trilobites apparently lack planktonic protaspides, but have up to two large benthonic protaspid stages that are similar in form to calymenid benthonic protaspides. These differences in life history patterns between these families are reflected in their paleobiogeographic distributions. Calymenids werre widely dispersed from Ordovician to Devonian times, both being common in warm, low latitude provinces (particularly from the Late Ordovician onwards) and well represented in cooler, higher latitude regions. The paleogeographic distribution of the homalonotids during the Ordovician (Arenig to the Ashgill) was concentrated in high paleolatitudes, with only a few forms occurring at low paleolatitudes (often in deeper, cooler environments?). Both families survived the Ordovician–Silurian mass extinction, with the calymenids again being widely dispersed but the homalonotids being best represented in the cool-water Malvinokaffric Province and in other regions where they are largely restricted to clastic facies.So few complete growth series of calymenine trilobites are known that it is unlikely that the ontogenies of taxa that form parts of ancestor–descendant clades can be identified. However, some evidence for heterochronic, particularly paedomorphic (neotenic), evolution is suggested for larval stages of members of both the Calymenidae and the Homalonotidae. Such possible neotenic evolution leading to very large planktonic larval stages of calymenid trilobites during the Devonian could have enhanced dispersal during a period of widespread warm and equable climates. Comparisons of homalonotid protaspides with equivalent stages of calymenids support the close relationship of these families within the Calymenina. A data matrix based upon characters of protaspides of two calymenine trilobites (Flexicalymene Shirley, 1936, and Brongniartella Reed, 1918) and eight other trilobites, belonging to the Phacopina (Calyptaulax), Cheirurina (Physemataspis and Hyrokybe), Proetida (Scharyia), Lichida (Acanthopyge), Odontopleurida (Diacanthaspis), Corynexochida (Bathyuriscus), and Ptychopariida (Crassifimbra) was subjected to cladistic analysis using the parsimony program “Hennig 86.” The shortest length cladogram produced is consistent with the inclusion of the Homalonotidae in the Calymenina, and inclusion of the Calymenina in the order Phacopida. “Cheirurina” is the paraphyletic “stem group” of Phacopina. The hypothesis that Lonchocephalidae is most closely related to part of post-Cambrian Phacopida is poorly supported by protaspid characters.

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Eddy, Julie D., and Linda B. McCollum. "Early Middle Cambrian Albertella Biozone trilobites of the Pioche Shale, southeastern Nevada." Journal of Paleontology 72, no. 5 (September 1998): 864–87. http://dx.doi.org/10.1017/s0022336000027207.

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Thirty-four species of trilobites belonging to 21 genera are recognized in the Albertella Biozone within the Grassy Spring Member (new name) of the Pioche Shale of southeastern Nevada. Genera include Pagetia, Poliella, Kootenia, Olenoides, Albertella, Albertellina, Albertelloides, Delamarella, Mexicaspis, Paralbertella, Ptarmiganoides, Ursinella, Zacanthoides?, Amecephalites, Mexicella, Nyella, Onchocephalites?, Pachyaspis, Panacus, Plagiura, and Volocephalina. Two new corynexochid genera and species, Delamarella brevispinaspis and Ursinella major, are described. The existing corynexochid genus Albertella is revised to include two new species, A. fritzi and A. highlandensis. A new species, Albertelloides kitai, is described. Two new ptychopariid genera, Amecephalites and Panacus, plus four new ptychopariid species, Amecephalites sundbergi, Mexicella granulata, Panacus palmeri, and Volocephalina variosa, are described and Nyella immoderata Palmer is revised. In addition, the Albertella Biozone is divided into three new subbiozones, the lower Albertellina aspinosa Subbiozone, the middle unnamed subbiozone, and the Albertella highlandensis Subbiozone.

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Whittington, Harry B. "The Corynexochina (Trilobita): A Poorly Understood Suborder." Journal of Paleontology 83, no. 1 (January 2009): 1–8. http://dx.doi.org/10.1666/08-047.1.

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Whittington, Harry B. "Hanburia gloriosa: Rare trilobite from the Middle Cambrian, Stephen Formation, British Columbia, Canada." Journal of Paleontology 72, no. 4 (July 1998): 673–77. http://dx.doi.org/10.1017/s0022336000040385.

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Hanburia gloriosa is probably blind, the smaller specimens having a forwardly expanding glabella with lateral lobes, and six (rarely five) thoracic segments; larger specimens have a parallel-sided glabella with faint traces of lateral lobes, and six, in one case seven, thoracic segments; pygidium equal in size to the cephalon. All specimens may be holaspid, the larger corynexochoid-like; however, the smaller ones are not like any known corynexochoid. Hanburia gloriosa is the rarest trilobite from the Stephen Formation. This species, and other rare but widely distributed Lower and Middle Cambrian species from deeper water faunas are all of uncertain affinities. They do not fit into the general picture of trilobite evolution, nor appear likely ancestors of shallow water species.

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Fortey, Richard A., and Robert M. Owen. "Phylogenetic history of major trilobite clades in relation to paleoenvironment." Paleontological Society Special Publications 6 (1992): 104. http://dx.doi.org/10.1017/s247526220000664x.

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Because trilobites occupied a wide a range of Paleozoic marine habitats they are a good group to examine hypotheses concerning the sites in which new major clades first appear, and their subsequent history of diversification and decline. There are several problems in this endeavour. The first concerns classification. Until a complete phylogenetic classification is available, there is no objective way to assess the equivalence or otherwise of groups which have been claimed as orders. For example, Odontopleurida and Lichida are treated as separate orders in some classifications, but are considered as a single major clade - presumably of ordinal status - in others. Some of the most commonly accepted groups (Olenellida, Ptychopariida) are paraphyletic. The second problem is taphonomic. The first appearance of a major group often coincides with a major extrinsic change, such as a regressive-transgressive couplet. Does the event initiate the novelty, or simply permit it to be preserved? Does such an event “punctuate” the fossil record, such that earlier, ancestral taxa belonging to the same clade go unrecognised?Trilobites are already paleogeographically diversified when they make their first appearance in the Lower Cambrian. Since trilobites constitute a true clade, this implies an earlier phase of vicariance of dispersal which is not recorded in the rocks. In China, Siberia, North America, and North Africa these first occurrences are in rocks of inshore origin: still earlier trilobites may have had thin cuticles which militated against their being preserved in the highest energy environments where “small shelly” fossils occurred. The groups Olenellida, Redlichiida, Corynexochida, Ptychopariina (?Lichida) appear in the early Cambrian. The earliest polymerids with morphology corresponding to deep water, atheloptic, is latest Lower Cambrian (Atops, Australia): there are many such in the mid-Cambrian.Opinions differ on the classification of Agnostida. Our own view relates Agnostina to Eodiscina, and on this view the early representatives of the clade (Lower Cambrian, China) are inshore compared with later agnostid occurrences, which typify outer shelf to slope. Ordovician agnostids are comparatively rare; the youngest agnostids were not confined to deep water sites.There is good evidence of early occurrences of Odontopleurida, Lichida s.s., Illaenina, Proetida and Phacopida in shallow water deposits. Evidence from Asaphida is more equivocal. Colonisation of deeper water habitats from shallow is rapid, although not achieved at the same time in each group. The scenario is of repeated production of deeper water forms from shelf taxa rather than wholesale movement of clades into that environment. After the demise of other groups in the late Devonian, for example, in the youngest Devonian and Carboniferous proetides radiated into deep water habitats. But the last trilobites of all in the Permian were shallow shelf inhabitants.

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17

Sundberg, Frederick A. "Arthropod pattern theory and Cambrian trilobites." Bijdragen tot de Dierkunde 64, no. 4 (1995): 193–213. http://dx.doi.org/10.1163/26660644-06404001.

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An analysis of duplomere ( = segment) distribution within the cephalon, thorax, and pygidium of Cambrian trilobites was undertaken to determine if the Arthropod Pattern Theory (APT) proposed by Schram & Emerson (1991) applies to Cambrian trilobites. The boundary of the cephalon/thorax occurs within the predicted duplomere node 1 (duplomeres 4 or 6). The boundary between the thorax and pygidium generally occurs within node 2 (duplomeres 11–13) and node 3 (duplomeres 18–20) for corynexochids and ptychopariids, respectively. This boundary occurs within field 4 (duplomeres 21–n) for olenellids and redlichiids. The termination of the body generally occurs within node 3 for corynexochids and within field 4 for olenellids, redlichiids, and ptychopariids. In addition, the location of macropleural spines, which may indicate the location of the gonopores or anus, generally falls at the predicted duplomeres. The boundary between the prothorax and opisthothorax of olenellids occurs within or near node 3. These results indicate that the number and distribution of duplomeres within Cambrian trilobites were somewhat constrained by some genetic patterning program. However, the common distribution of boundaries outside of the predicted locations and the possible shifting of nodes suggest that other factors were also controlling the number of duplomeres within the body parts. This variation supports the idea that Cambrian arthropods, unlike modern arthropods, had a simpler genetic program, which easily allowed for changes in the Bauplan.

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McNAMARA, KENNETH J., and RAIMUND FEIST. "NEW STYGINIDS FROM THE LATE DEVONIAN OF WESTERN AUSTRALIA— THE LAST CORYNEXOCHID TRILOBITES." Journal of Paleontology 80, no. 5 (September 2006): 981–92. http://dx.doi.org/10.1666/0022-3360(2006)80[981:nsftld]2.0.co;2.

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19

Bordonaro, Osvaldo Luis, and Carlos Fabían Fojo. "Bathyuriscus mendozanus (RUSCONI, 1945), TRILOBITES DEL CÁMBRICO MEDIO DE LA PRECORDILLERA ARGENTINA." Spanish Journal of Palaeontology 26, no. 1 (October 13, 2020): 11. http://dx.doi.org/10.7203/sjp.26.1.18466.

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Se realiza una revisión taxonómica del trilobite corynexochido Plesioparabolina mendozana, que es reclasificado como Bathyuriscus mendozanus, que presenta caracteres morfológicos distintivos respecto a las otras 19 especies laurénticas incluidas en este género. También se incluyen en esta especie algunos ejemplares del mismo género previamente determinados en nomenclatura abierta y, además, se incorporan nuevos especímenes coleccionados por los autores. La mayoría de los fósiles estudiados se encuentran en olistolitos cámbricos, de calizas de plataforma externa, que se hallan alojados en pelitas ordovícicas. Los trilobites estudiados proceden de las localidades ubicadas en quebrada Ojos de Agua, quebrada Los Sombreros, Cordón del Alojamiento y San Isidro, de la Precordillera Argentina. La edad de la especie estudiada se ubica en el Cámbrico medio, Marjumiense, Zona de Oryctocephalus, según el esquema cronoestratigráfico tradicional de Laurentia, lo que equivale en el esquema bioestratigráfico mundial propuesto por la International Subcommission on Cambrian Stratigraphy (ISCS) a la Series 3, a la parte superior del Piso 5 del Cámbrico

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Hopkins, Melanie J., and Mark Webster. "Ontogeny and geographic variation of a new species of the corynexochine trilobite Zacanthopsis (Dyeran, Cambrian)." Journal of Paleontology 83, no. 4 (July 2009): 524–47. http://dx.doi.org/10.1666/08-102r.1.

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Assessment of ontogenetic and geographic variation can have substantial influence on species delimitation and thereby on perceived patterns of species-level morphological variation and diversity in space and time. Here we describe the ontogeny and intraspecific variation of the early Cambrian trilobite, Zacanthopsis palmeri n. sp., based on silicified material from east-central Nevada, USA. Zacanthopsis palmeri is the oldest documented Cambrian corynexochine to shift from possessing a fused rostal-hypostomal plate to a functional hypostomal suture in mature specimens during ontogeny. Six geographically distinct samples of mature Z. palmeri from a single silicified limestone bed traceable over tens of kilometers in east-central Nevada permit exploration of geographic variation within this species using geometric morphometric methods. No one sample encompasses all of the shape variation expressed by Z. palmeri and several geographically segregated samples show some degree of morphological separation in pairwise comparison. Nonetheless, these samples are not qualitatively or quantitatively different from one another when all samples are taken into account. The degree of variation within Z. palmeri is similar in magnitude to the differences between other species in the genus known from much less material.

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Zhu, Xue-Jian, Nigel C. Hughes, and Shan-Chi Peng. "Ventral structure and ontogeny of the late Furongian (Cambrian) trilobite Guangxiaspis guangxiensis Zhou, 1977 and the diphyletic origin of the median suture." Journal of Paleontology 84, no. 3 (May 2010): 493–504. http://dx.doi.org/10.1666/09-070.1.

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Articulated meraspid and holaspid exoskeletons of Guangxiaspis guangxiensis from the Guole Township, Jingxi County, Guangxi Province, China, are preserved in mudstone deposited during an obrution event. The species has a short dorsal pre-cranidial median suture that splits ventrally into a pair of posteriorly divergent connective sutures. The rostral plate of G. guangxiensis is thus triangular in outline, as in the co-occurrent Shergoldia laevigata, which also bore a conterminant hypostome. These two taxa appear to be closely related. The cephalic venter of Shergoldia laevigata has recently been interpreted to suggest a diphyletic origin of the median suture within the order Asaphida, but Guangxiaspis guangxiensis, Shergoldia laevigata and other tsinaniid trilobites display several characters reminiscent of members of the non-asaphide suborder Leiostegiina. These include swellings adjacent to the margins of the L1 glabellar lobe, the shape and furrows of the glabella, a semi-circular pygidium with a long and thin axis, and macrospinous first opisthopleurae of the holaspid pygidium. Based on these characters and on other new information on the early ontogeny of other tsinaniids, all these taxa likely belong within Leiostegiina. This suggests that the median suture arose independently in corynexochide and asaphide trilobites. The degree of convergence between S. laevigata and members of the derived asaphide family Asaphidae was remarkable. Guangxiaspis guangxiensis shows marked morphological change during both meraspid and holaspid ontogeny and might include more than a single morphotype.

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Pratt, Brian R., and Osvaldo L. Bordonaro. "Early Middle Cambrian Trilobites from La Laja Formation, Cerro El Molle, Precordillera of Western Argentina." Journal of Paleontology 88, no. 5 (September 2014): 906–24. http://dx.doi.org/10.1017/s0022336000057577.

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A tectonically undeformed portion of the lower part of La Laja Formation is exposed at Cerro El Molle near San Juan, Precordillera of western Argentina. It consists of shallow-water, variably argillaceous lime mudstone and sporadically interbedded bioclastic grainstone deposited in an inner shelf setting. The El Estero Member and the basal 0.2 m of the Soldano Member contain a trilobite fauna of olenelloids and ‘simple’ ptychoparioids indicative of the early Cambrian (series 2, stage 4; Dyeran stage of Laurentia). The succeeding 50 m of the lower Soldano Member yield trilobites characteristic of the early middle Cambrian (series 3, stage 5; Delamaran stage of Laurentia). In ascending order of occurrence,Amecephalus arrojosensis,Kochiella maxeyiandEokochaspis nodosa, along with several other taxa, includingPtychobaban. gen. (type speciesPtychoparella buttsi), belong to the traditional lowerPlagiura–PoliellaBiozone. However, while this fauna is similar to that of the Great Basin, the nominative species of theEokochaspsis nodosaand overlyingAmecephalus arrojosensisbiozones recognized in southern Nevada occur in reverse order in the Soldano Member. This suggests that the ranges of these species overlap, thereby reducing the temporal resolution in the Precordillera into a combinedAmecephalus arrojosensis–Eokochaspis nodosaBiozone. Argillaceous lime mudstones at the top yieldMexicella mexicana, indicative of theMexicella mexicanaBiozone recognized in the Great Basin, which is equivalent to the traditionalAlbertellaBiozone of Laurentia. Because corynexochids are almost absent, the low-diversity ‘kochaspid’-dominated biofacies appears to typify the platform interior. The fauna is entirely Laurentian in composition, reinforcing notions of a close proximity of Cuyania to Laurentia during the Cambrian that enabled faunal migration and interchange. The absence of a late early Cambrian to early middle Cambrian hiatus correlative with the Hawke Bay Event, however, suggests no close affinity to the Iapetus-facing margin of eastern Laurentia.

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Fletcher, Terence P., and Desmond H. Collins. "The Burgess Shale and associated Cambrian formations west of the Fossil Gully Fault Zone on Mount Stephen, British Columbia." Canadian Journal of Earth Sciences 40, no. 12 (December 1, 2003): 1823–38. http://dx.doi.org/10.1139/e03-057.

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West of the Fossil Gully Fault Zone on Mount Stephen, the three lowest members only of the Burgess Shale Formation are preserved: the Kicking Horse Shale, the Yoho River Limestone, and the Campsite Cliff Shale. The formation rests unconformably upon the Takakkaw Tongue Formation, whose dark basinal limestones conformably overlie paler shelf-like limestones of the Mount Whyte Formation. Mapping has resolved a long-standing problem and shown that the stratigraphical position of the famous Mount Stephen Trilobite Beds lies within the Campsite Cliff Shale. It has also revealed some of the complexities of the Fossil Gully Fault Zone, among which different periods and directions of component fault movements are indicated. Faunal evidence shows that the PlagiuraKochaspis to Albertella and Albertella to Glossopleura zonal boundaries lie within the Takakkaw Tongue sequence. Within the Burgess Shale, three distinct soft-bodied communities occur at different stratigraphical levels on this mountain slope. The oldest, characterized by the arthropod Alalcomenaeus and chelicerate Sanctacaris, occurs low in the Kicking Horse Shale Member and is best known from Collins Quarry. The others lie within the Campsite Cliff Shale Member. The Trilobite Beds, characterized by claws of the dinocarid Anomalocaris and moults of the trilobite Ogygopsis klotzi, onlap the sloping top of a proximal bench facies of the Yoho River Limestone Member close to the Cathedral Escarpment. Slightly older and farther out in the basin are beds characterized by the dinocarid Laggania and a tulip-like animal related to Dinomischus, excavated about 12 m above the top of a thin distal wedge facies of the Yoho River Limestone at the S7 site. Among the illustrated trilobites, a new corynexochine from the Campsite Cliff Shale Member is figured.

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Lei, Qian-Ping, Qing Liu, and Shan-Chi Peng. "Three species of Pagodia (Corynexochida, Trilobita) from the furongian (Cambrian) of northern anhui, china and their intraspecific variation." Palaeoworld, July 2022. http://dx.doi.org/10.1016/j.palwor.2022.07.002.

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Lei, Qian-Ping, and Qing Liu. "Two species of Tsinania (Trilobita, Corynexochida) from upper Furongian (Cambrian) of northern Anhui, China and their intraspecific variation." Palaeoworld, June 2020. http://dx.doi.org/10.1016/j.palwor.2020.06.010.

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26

Foster, John R. "Bonnima sp. (Trilobita; Corynexochida) from the Chambless Limestone (Lower Cambrian) of the Marble Mountains, California: First Dorypygidae in a cratonic region of the southern Cordillera." PaleoBios 30, no. 2 (October 19, 2011). http://dx.doi.org/10.5070/p9302021790.

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27

Wang, Yifan, Jorge Esteve, Xinglian Yang, Rongxing Yu, and Dezhi Wang. "First confident evidence of moulting in eodiscid trilobites from the Cambrian Stage 3 of South China." Geological Magazine, October 19, 2023, 1–5. http://dx.doi.org/10.1017/s0016756823000584.

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Abstract Trilobite moulting behaviour has been extensively investigated. However, exuviae in eodiscid trilobites are poorly known. Here, we report two eodiscid trilobite specimens, Tsunyidiscus niutitangensis and Tsunyidiscus sp., showing Somersault configuration from the Niutitang Formation and Mingxinsi Formation of South China, respectively (Cambrian Series 2, Stage 3). The arrangements of the exoskeletons indicate that the two specimens are the slightly disturbed and undisturbed exuviae. The impression of the lower cephalic unit (LCU) displays the rostral plate in Tsunyidiscus niutitangensis. The exuviae showing the LCU inverted anteriorly under the trunk. The opening of the facial and rostral sutures would have allowed the emergence of the post-ecdysial trilobite with the partial enrolment of exoskeleton. Moreover, our discovery indicates a Somersault configuration which employed the facial and rostral sutures to create an anterior exuvial gape that also exists in eodiscid trilobites besides redlichiid trilobites, corynexochid trilobites and ptychopariid trilobites during the Cambrian.

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Handkamer, Neal M., Andrei Ichaso, Brian R. Pratt, M. Gabriela Mángano, and Luis A. Buatois. "Systematics and biostratigraphy of a new trilobite fauna collected from the subsurface Earlie Formation (Wuliuan Stage, Miaolingian Series, Cambrian) in southwestern Saskatchewan." Canadian Journal of Earth Sciences, May 19, 2023. http://dx.doi.org/10.1139/cjes-2023-0003.

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Trilobites were recovered from four cores of the middle Cambrian Earlie Formation in southwestern Saskatchewan. Fossils occur in silty mudstone with interbedded siltstone and limestone, deposited in the inner detrital belt of the craton interior, under low-energy, subtidal conditions. Taxa identified include Kootenia dawsoni (Walcott 1889), Asaphiscus wheeleri Meek 1873, Blainia gregaria Walcott 1916b, Parehmania princeps Deiss 1939b, Ehmania weedi Resser 1935, Bolaspis labrosa (Walcott 1916a), and corynexochid gen. and sp. indet., indicating an age ranging from the lower to upper Altiocculus subzone of the Ehmaniella Zone, upper Wuliuan Stage. The upper Eldon and lower Pika formations located farther west in subsurface Alberta and the Rocky Mountains are considered to be age equivalent. Biostratigraphy confirms that strata overlying the Basal Sandstone Unit are diachronous and become progressively younger eastward. The trilobite fauna is lower in diversity relative to those in temporally equivalent units in the Rocky Mountains as well as the Great Basin, indicating that it may have experienced some environmental stressors, and that seafloor colonization was sporadic and opportunistic.

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Sundberg, Frederick A., and Mark Webster. "Corynexochine trilobites of the Harkless Formation and Mule Spring Limestone (Cambrian Series 2, Stage 4), Clayton Ridge, Nevada." Journal of Paleontology, June 25, 2021, 1–18. http://dx.doi.org/10.1017/jpa.2021.41.

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Abstract Most Cambrian Series 2 faunas of Laurentia are dominated by olenelline trilobites; however, non-olenelline trilobites occur with the olenellines and sometimes dominate the assemblages. Reported here are such non-olenelline trilobites from the Harkless Formation and Mule Spring Limestone at Clayton Ridge, Nevada. At the bottom of the Saline Valley Tongue, Harkless Formation, are two assemblages that are characterized by corynexochines and/or ptychoparioids, with olenellines occurring as only rare components. The corynexochines present in these assemblages include Bonnia cf. B. brennus (Walcott, 1916), Ovatoryctocara cf. O. yaxiensis Yuan et al., 2009, Protoryctocephalus? aff. P.? arcticus Geyer and Peel, 2011, Ogygopsis sp. indet., and Oryctocephalops frischenfeldi Lermontova, 1940. These assemblages are from the mid-Dyeran Stage, below the lowermost zone in the upper Dyeran (Arcuolenellus arcuatus Biozone), and can be correlated to Series 2 Stage 4 (Cambrian) assemblages in Greenland, Siberia, and South China based on the corynexochines. Also in the Saline Valley Tongue and the overlying Mule Spring Limestone and lowermost Emigrant Formation are olenelloid-dominated assemblages that contain the corynexochines Bonnia columbensis Resser, 1936, Zacanthopsis aff. Z. levis (Walcott, 1886), and Z. sp. indet.

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Journal articles on the topic 'Corynexochida'

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