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Later Cambrian trilobite genera Archikainella and Chencunia are respectively based solely on cranidia and pygidia. An articulated exoskeleton found recently from southwestern Guangxi Zhuang Autonom...

A previously unreported calymenid trilobite, Gravicalymene bakeri sp. nov., is described herein from Late Ordovician (latest Eastonian, Katian) shales of the Gordon Group, Tasmania. This is the fir...

Wei, X. & Zhan, R. B., 20 September 2018. A new trilobite species from the upper Rhuddanian (lower Silurian) of South China, and its biogeographical implications. Alcheringa 43, 33–42. ISSN 0311-55...

Jago, J.B., Bentley, C.J., Laurie, J.R. & Corbett, K.B., 26 June 2018. Some middle and late Cambrian trilobites and brachiopods from the Adamsfield Trough, Tasmania. Alcheringa 43, 1-17. ISSN 0311-5518.Cambrian Series 3 and Furongian trilobites and brachiopods are described from the Adamsfield Trough in southwestern Tasmania. The oldest fossils are very poorly preserved trilobites, assigned to Asaphiscidae gen. et sp. indet. from within the Island Road Formation a short distance above the unconformity with the underlying Proterozoic Wedge River Beds. A trilobite species from within the isolated Boyd River Formation is referred to Lioparia sp. The Island Road Formation and the Boyd River Formation are stratigraphically equivalent to the Trial Ridge Beds which have previously been dated as belonging to the Lejopyge laevigata Zone. The Trial Ridge Beds are overlain unconformably by the Singing Creek Formation. In the Adamsfield, Clear Hill and Stepped Hills areas, stratigraphic equivalents of the Singing Cre...

McCobb, L.M.E., Boyce, W.D., Knight, I. & Stouge, S., 2014. Lower Ordovician trilobites from the Septemberso formation, North-East Greenland. Alcheringa 38, 575–598. ISSN 0311-5518.The informally named Septemberso formation is a 76 m thick succession of microbial and peritidal shelf carbonates deposited on the North-East Greenland shelf of Laurentia. The formation, assigned to the lower part of the Cape Weber Formation in all previous studies, lies disconformably upon the Skullrockian Antiklinalbugt Formation (revised) and conformably below the Tulean to Blackhillsian Cape Weber Formation (revised) in the Fimbulfjeld Group. With the exception of Randaynia, the modest trilobite fauna recovered from the Septemberso formation consists exclusively of bathyurids, and all represent new species. Both Chapmanopyge knudseni sp. nov. and Punka adamsi sp. nov. are represented by sufficient material to merit specific names. The remaining taxa, belonging to Bolbocephalus, Peltabellia, Randaynia and Chapmanopyge are le...

A new faunal assemblage is reported from the Tempe Formation (Cambrian Series 2, Stage 4; Ordian) retrieved from the Hermannsburg 41 drillcore, Amadeus Basin, central Australia. Two trilobite taxa, including one new species Gunnia fava sp. nov., four brachiopod taxa, including the age-diagnostic Karathele napuru (Kruse), Kostjubella djagoran (Kruse) and Micromitra nerranubawu Kruse, together with a bradoriid, helcionellids, hyoliths, echinoderms, chancelloriids, sponges and problematic tubes are described. The fauna has close links to those of the neighbouring Daly, Georgina and Wiso basins and suggests that the Tempe Formation correlates with the Australian Ordian stage (either the Redlichia forresti or Xystridura negrina assemblage zones). The Giles Creek Dolostone in the eastern Amadeus Basin, previously regarded as coeval with the Tempe Formation, has recently been reported to be of early Templetonian age in its type section. The described taxa from the Tempe Formation confirm that these two sedimenta...

Jell, P.A., 2014. A Tremadocian asterozoan from Tasmania and a late Llandovery edrioasteroid from Victoria. Alcheringa 38, 528–540. ISSN 0311-5518.An asterozoan, Maydena roadsidensis gen. et sp. nov., is described from the mid-Tremadocian (La1b Zone) Florentine Valley Formation in southwestern Tasmania and is the oldest known asterozoan in the world. Although only a single, largely dissociated, specimen is available, enough is preserved to recognize distinctive ambulacral plates similar to those of Archegonaster Jaekel from the Llanvirn of the Czech Republic. Reciprocodiscus transambus n. gen., n. sp. is an isorophid edrioasteroid from the uppermost late Llandovery Springfield Formation exposed in the bed of Deep Creek, near Springfield, 65 km north northwest of Melbourne. It occurs with a low-diversity trilobite fauna indicating a deepwater, subphotic environment. This edrioasteroid has in each ambulacrum a single series of floor plates that are not visible on the oral surface, indicating its isorophid a...

During the Middle Ordovician (Darriwilian) sandstones and siltstones were deposited in the epicontinental Larapintine Sea, which covered large parts of central Australia. The Darriwilian Stairway Sandstone has, for the first time, been sampled stratigraphically for macrofossils to track marine benthic biodiversity in this clastic-dominated shallow-water palaeoenvironment situated along the margin of northeastern Gondwana. The faunas from the Stairway Sandstone are generally of low diversity and dominated by bivalves but include several animal groups, with trilobites representing 25% of the entire shelly fauna. Thirteen trilobite taxa are described from the Stairway Sandstone; the fauna displays a high degree of endemism. One new species, Basilicus (Parabasilicus) brumbyensis sp. nov. is described.

An entire exoskeleton of Neodrepanura recovered from the Cambrian Kushan Formation in Laiwu, Shandong, China, represents the first complete specimen recorded for the genus since its establishment over 110 years ago. As an important genus of the Family Damesellidae, the new discovery aids our understanding of the dorsal morphology of the genus, clarifies morphological diversity within the family and permits revision of the erroneous reconstruction made by Kobayashi in 1942.

The brachiopod fauna of the upper Cambrian (upper Furongian) Guole Formation, northwestern Jingxi County, southwestern Guangxi Province, southern China, comprises six genera and seven species, including one new genus, three new species and two indeterminate species (Obolidae gen. et sp. indet, Acrotretidae gen. et sp. indet., Billingsella guangxiensis, B. costata sp. nov., Guoleella lata gen. et sp. nov., Palaeostrophia jingxiensis, Plectotrophia imparicostata sp. nov.). This is the first systematic description of an upper Cambrian brachiopod fauna composed mainly of calcareous-shelled individuals from China. Brachiopod and trilobite faunal analyses suggest that this fauna has a prominent North American (Laurentian) affinity. It is notably different from the coeval, lingulate-dominated brachiopod fauna of South China, particularly of the Yangtze Platform, but shares some similarity with those of the North China Platform. Preliminary analysis reveals that this brachiopod fauna, named the Billingsella-Palae...

Dai, T. & Zhang., X., December, 2008. Ontogeny of the trilobite Yunnanocephalus yunnanensis from the Chengjiang lagerstatte, lower Cambrian, southwest China. Alcheringa 32, 465–468. ISSN 0311-5518....

Cyclolorenzella is an important member of the middle Cambrian trilobite faunas in China and Korea. Morphometric analysis based on well-preserved new material assignable to Cyclolorenzella from China and Korea reveals that most of the species assigned previously to Cyclolorenzella in China are morphologically distinct from the genotype. Accordingly, the new genus Jiulongshania, with J. acalle (Walcott, 1905) as type species, is proposed to accommodate the following species: J. acalle, J. regularis (Walcott, 1906), J. rotundata (Resser & Endo in Endo & Resser, 1937), J. longispina (Wittke & Zhu in Zhu & Wittke, 1989), J. acuta (Duan in Duan et al., 2005) and J. longa sp. nov. Species tentatively transferred to Jiulongshania are J.? subcylindrica (Chu, 1959), J.? yentaiensis (Chu, 1959), J.? humilis (Zhang in Qiu et al., 1983), and J.? latisulcata (Zhang in Qiu et al., 1983). This taxonomic revision results in only two species remaining in Cyclolorenzella, the type species C. quadrata (Kobayashi, 1935) and C...

One of the most prolific trilobites in the mid-Palaeozoic of central Victoria is the dalmanitid Dalmanites wandongensis Gill, 1948. Extensive museum collections permit a revised diagnosis and a redescription of the species, and an interpretation of its distribution. The affinities of D. wandongensis lie with South American species assigned to Dalmanites and the closely related Kasachstania rather than northern hemisphere taxa including the D. caudata group. It occurs between Heathcote and Yan Yean in central Victoria, in late Wenlock and early Ludlow (Silurian) strata of the Dargile Group, on the eastern margins of the Melbourne Zone; its greatest abundance is between Kilmore and Wandong, where it is documented from over fifty localities, occurring rarely with other trilobite taxa. At Heathcote, Upper Plenty, Yan Yean and Kilmore East D. wandongensis stratigraphically underlies a more diverse trilobite fauna dominated by the encrinurid Cromus simpliciculus. This trilobite faunal succession defines a signi...

Well-preserved internal and external moulds of a shumardiid species are described from the late Furongian (Late Cambrian) “Fengshan Formation” at Poben, Napo, southwestern Guangxi, which is close to the type locality of Shumardia orientalis, the type species of Eoshumardia. All features observed on the internal moulds indicate that the new material is definitely S. orientalis, whereas the morphology of the external moulds indicates that S. orientalis should be referred to Koldinioidia. The change of generic assignment of the type species means that Eoshumardia is a junior synonym of Koldinioidia.

The Late Cambrian trilobite genus Hamashania Kobayashi, 1942a has hitherto been poorly understood and is herein revised based on well-preserved specimens from Korea. Platysaukia Kobayashi, 1960 and Goumenzia Guo & Duan, 1978 are treated as junior synonyms of Hamashania. Hamashania comprises only two species, H. pulchera Kobayashi, 1942a and Pterocephalus busiris Walcott, 1905, and is restricted to North Chinaand Korea. The new genus Pacootasaukia is proposed to accommodate the Australian species Platysaukia jokliki Shergold, 1991 as type species, and Platysaukia tomichi Shergold, 1991, which are so distinct that they cannot be included within Hamashania. The generic concept of Mareda Kobayashi, 1942b, which was often confused with Hamashania, is confined to the type material.

A Pragian (Early Devonian) trilobite fauna from the Norton Gully Formation in the Upper Yarra area of central Victoria consists exclusively of the phacopid Prokops moorei sp. nov., a species with a highly variable visual surface including greatly reduced and blind morphologies. Several trilobites are preserved as moult assemblages, but most occur as isolated tergites on bedding-planes crowded with dacryoconarids and small bivalves. The autecology and taphofacies of the fauna indicate a deep-water setting, with the biofacies associations closely resembling deep-water assemblages described from Devonian sequences elsewhere. The distributions of laterally equivalent late Pragian facies from eastern areas of the Melbourne Zone indicate an inclined shelf between Lilydale and the Upper Yarra area, deepening eastwards from shoreline to outer shelf settings. To the northwest and northeast of the Upper Yarra area, the shelf was bounded by tectonically active margins associated with the converging Benambra Terrain,...

Prosopiscus is particularly important in Ordovician palaeobiogeography because of its wide geographic distribution in Gondwana and peri-Gondwanan regions. It appears to have been confined to low palaeolatitudes, representing a characteristic member of the warm water eastern Gondwanan shelf faunas. Trends in the distribution of the Ordovician genus can be observed due to its long stratigraphic range. Prosopiscus was restricted to, and may have originated in, Australia during the late Early Ordovician (Bendigonian-Chewtonian). By the Middle Ordovician (Darriwilian), Prosopiscus had dispersed to other parts of Gondwana and peri-Gondwana, including the North and South China blocks, Tarim, central Himalayas, and the Argentine Precordillera (South America). Possible explanations for the distribution of Prosopiscus are that: (1) there were no oceanic barriers preventing dispersal of trilobites between different regions of Gondwana, thus permitting uninhibited migration over vast distances; (2) Prosopiscus was no...

A comparison of ecdysial patterns between trilobites and other macrobenthic marine arthropods (crabs, shrimp, lobsters, horseshoe crabs) reveals differences that may have evolutionary consequences. Limulus and many malacostracans apparently have a signature ecdysial style; conversely, a range of moult configurations characterized trilobite ecdysis, and this variation is evident even within individual species. A canalised ecdysial habit may be safer or metabolically more efficient and therefore, summed over the history of the class, evolutionarily advantageous. Some trilobite clades show evolutionary trends toward morphologies that would have facilitated ecdysis (e.g. reduction in the number of thoracic segments, reduction in the number and prominence of spines), but co-adaptation or multiple-use effects complicate the evolutionary signal of ecdysial selection. Survivorship analysis supports a possible link between ecdysial habit and evolutionary success: genera with fewer thoracic segments (= easier ecyds...

On the basis of representative collections made from seven measured sections in western Hubei and Hunan, four early Llanvirn and five late Llanvirn-early Caradoc trilobite biofacies are distinguished along a bathymetric gradient from shallow to deep outer shelf. The diversity and relative abundance of mesopelagic cyclopygids gradually increased southwards or seawards. According to the facies association exhibited in the region, the upper limit of living depth for different forms is inferred as follows: 1) more than 70 m (M. (Microparia)); 2) less than 100 m (M. (Quadratapyge), Pricyclopyge, Aspidaeglina); 3) at approximately 100 m (Cyclopyge); and 4) more than 100 m (Symphysops, Psilacella). Benthic forms were absent in the deep outer-shelf basin because of stagnant conditions. In shallower sites of the outer shelf, genera of nileids in the carbonate facies and raphiophorids in the clastic facies were relatively abundant, but some endemic forms, such as the asaphid Birmanites and remopleuridid Hexacopyge,...

The Taebaeksan Basin occupies the central-eastern part of the Korean peninsula and was a low-relief shallow marine carbonate shelf on which the Cambro-Ordovician Choson Supergroup was deposited. In the Taebaeksan Basin trilobites are among the most dominant fossil groups in the Lower Ordovician, but they become less important in Middle Ordovician faunal assemblages. The Early Ordovician trilobite faunas of the Taebaeksan Basin are characterised by the common occurrence of pandemic genera such as Jujuyaspis, Leiostegium, Asaphellus, Protopliomerops, Hystricurus, Apatokephalus, Shumardia, Asaphopsoides, and Kayseraspis. Biogeographically significant trilobite taxa include Yosimuraspis, Dikelokephalina, Koraipsis, and Chosenia. These Ordovician trilobite faunas, which thrived in shallow marine environments, show a remarkable similarity with faunas from North China, implying that the Taebaeksan Basin was connected through contiguous shallow waters to North China. These Sino-Korean faunas exhibit a close bioge...

The Billabong Creek Formation and overlying Gunningbland Formation within the Northparkes Group in the Gunningbland area, 28 km west of Parkes, range in age from late Darriwilian (late Middle Ordovician) to late Eastonian (middle Late Ordovician). These strata provide the most complete sequence through this interval in the central Lachlan Orogen in New South Wales. A biostratigraphic zonation spanning the Darriwilian to Gisbornian is proposed, employing conodonts and corals. This supplements the existing coral/stromatoporoid, brachiopod and trilobite faunal assemblages defining Eastonian and Bolindian shelly fossil zones. The Pygodus anserinus Zone (late Darriwilian) in the basal Billabong Creek Formation is succeeded by the Foerstephyllum-Billingsaria-Stratodictyon Assemblage-Zone (of Gisbornian age) in the middle Billabong Creek Formation. A further five Assemblage-Zones extending through the Eastonian succession are formally defined to replace the existing shelly fossil ‘faunas’. New coral species desc...

Trilobites are common faunal elements in the Melbourne Formation, a unit of early Ludlow (upper nilssoni Biozone) age, which crops out extensively in the Darraweit Guim Province of the Melbourne Zone, central Victoria. New diagnoses are given for species previously described, including Maurotarion euryceps (McCoy, 1876; = Cyphaspis spryi Gregory, 1901), Raphiophorus jikaensis (Chapman, 1912; = Ampyx yarraensis Chapman, 1912), Cromus simpliciculus (Talent, 1964), Cromus spryi (Chapman, 1912), Sthenarocalymene kilmorensis (Gill, 1945; = Gravicalymene hetera Gill, 1945) and Trimerus harrisoni (McCoy, 1876). A new phacopid genus, Orygmatos is described, represented by the species O. yanyeani gen. et sp. nov. Other species newly described include Cromus melbournensis sp. nov., Arcticalymene australis sp. nov., “Ananaspis” woiwurrungi sp. nov. and Kettneraspis hollowayi sp. nov. Species composition of the trilobite fauna varies spatially, and a number of distinct assemblages can be defined. Abundant trilobite m...

An entire and fragmentary specimens of Bathynotus from the Northern Territory, Australia, are described and referred to B. holopygus. Entire specimens from the Kaili Formation, Guizhou, China, may also belong to this species which was widespread, inhabiting the outer shelf to slope facies of the olenellid and redlichiid (Perigondwana) faunal realms. Species based on fragmentary material may, or may not, be different. The stratigraphical range of B. holopygus lies within the currently debated late Lower Cambrian to early Middle Cambrian transition. The cranidial morphology and macropleural eleventh thoracic segment suggests that it may belong with the Redlichioidea; the morphology appears to allow complete enrolment.

Eastonian trilobite faunas of the Gordon Group in Tasmania include the new species Ceraurinella oepiki, Erratencrinurus trippi, and Pliomerina trisulcata, as well as a reedocalymeninid probably allied to Sarrabesia Hammann & Leone, 1997. Ceraurinella and Erratencrinurus have not previously been reported from Australia, the former being predominantly Laurentian but also known from NE China, the Himalaya, and Vietnam, and the latter mostly Baltic/Laurentian. Peri-Gondwanan species of Ceraurinella appear to form a clade, within which Tasmanian and Indian (central Himalayan) taxa are closest relatives.

Comparison of ontogenetics suggest that the Middle Cambrian Xystridura evolved from the Lower Cambrian species Hsuaspis bilobata by changes in the rate or timing of development of characters during ontogeny. Extension of the juvenile growth period delayed maturation, or hypermorphosis resulted in exaggeration of normally slow, early holaspid growth patterns within the rapid, late meraspid growth stage, producing a marked progradation of the glabella in Xystridura. Forms referable to H. cerastes from the upper Early Cambrian Cymbric Vale Formation of New South Wales appear to show the beginnings of this hypermophic trend.

The carbonaceous fossil Chuaria circularis Walcott (1899) is reported from the Raiwalla Shale of the Wessel Group (onshore Arafura Basin), Northern Territory. As most occurrences of Chuaria are Proterozoic and the majority of these are Neoproterozoic, the Early to Middle Cambrian age previously assigned to the Wessel Group is no longer well supported, especially since the main fossil evidence on which this was based is no longer applicable. A carbonate unit containing a Middle Cambrian trilobite fauna, previously considered part of the Wessel Group, is now interpreted to lie unconformably above this group. The discovery has regional stratigraphic significance in northern Australia and the ages of other poorly dated successions, commonly assumed to be of Early Cambrian age, requires reassessment.

New interpretations are available from recently published appendages of Eoredlichia intermedia (Early Cambrian Chengjiang fauna), the most primitive trilobite for which appendages are known. The basis (formerly identified as the coxa) is preserved in one

Three trilobite species, Lisogorites mistus sp. nov., Taklamakania tarimensis W. T. Zhang and Ampyxinella rotundata W. T. Zhang, are described from the Yingan Formation near Kalpin in southern Xinjiang, NW China. They occur with graptolites in an assemblage of late Caradoc age. Lisogorites is an aberrant asaphid, and is considered to be a senior synonym of Trigonoaspis and Tangyaia. Ampyxinella is regarded as referable to the subfamily Endymioninae. The raphiophorid Taklamakania has only three thoracic segments and may have been derived from Ampyxina by neoteny. The morphological and taphonomical features of the trilobites suggest that this faunule lived on a soft muddy substrate in a quiet, deeper-water, slope environment of the ‘Raphiophorid Biofacies’. Palaeogeographically the Kalpin area was located on the northwestern slopes of the Tarim carbonate platform during Caradoc times. Closest zoogeographic relationships of this fauna are with South China, Kazakhstan, North China and eastern Australia.

A new species of conocoryphid trilobite, Atops rupertensis, is described from the upper part of the Lower Cambrian Hawker Group of the Flinders Ranges, South Australia. Atops has not been previously described from Australia. The specimens described herein represent the most detailed material yet available for the genus; a new generic diagnosis is given. It is suggested that Ivshiniellus Korobov is a synonym of Atops; the material described as Ivshiniellus briandailyi from the Heatherdale Shale near Adelaide probably belongs in Atops. It is possible that Atopina Korobov is a synonym of Pseudatops Lake.

A new monotypic genus of cheirurine trilobite, Azyptyx, is described based on the new species A. toongabbiensis from Early Devonian (late Lochkovian) limestones of the Wurutwun Formation near Toongabbie, Victoria. A feature of the genus that is unusual for the subfamily is a continuous basal glabellar furrow (S1) that does not normally meet the occipital furrow medially.

During recent investigations of the Middle Cambrian phosphate deposits south of Duchess in the Burke River Structural Belt, Georgina Basin, western Queensland, large numbers of the early growth stages of trilobites have been recovered by acid etching of samples from the Monastery Creek Phosphorite Member of the Beetle Creek Formation. Among these a late protaspid growth stage is recognised as belonging to Pagetia ocellata Jell 1970, described earlier from the same formation. The morphogenesis of this and the earliest meraspid growth stage are described, and their development compared to that of an associated agnostoid referred to Peronopsis. The differences between eodiscoid and agnostoid trilobites are reviewed in the light of much recently published information. A taxonomic separation of at least ordinal magnitude is advocated. If miomeran arthropods are related to polymeroid trilobites, then the eodiscoids are the closer of the two groups.

Donovan, S.K. & Hoek Ostende, L.W. van den., September 2012. Neoextrania, a replacement name for Extrania Sun & Wang, 1985 (Ostracoda), preoccupied by Extrania Qian in Qiu et al., 1983 (Trilobita). Alcheringa 36, 431. ISSN 0311-5518. The early Palaeozoic trilobite Extrania Qian in Qiu et al., 1983, is a senior homonym of the Devonian ostracod Extrania Sun & Wang, 1985. Neoextrania nom. nov. is proposed for the homonymous ostracod.

Examples of an undescribed species of the trilobite Redlichia from the Emu Bay Shale (Early Cambrian), Kangaroo Island, South Australia, show damage to the exoskeleton attributed to the action of predators. Injury was probably not lethal. The identity of the predators is unresolved, notwithstanding soft-part preservation within the fossil assemblage. Possible culprits include either a rare and presumably large animal such as an arthropod or conceivably cannibalism by Redlichia itself. This report provides new data on the occurrence of Cambrian predators, and casts further doubt on earlier suggestions that macrophagous predation was insignificant at this time. Aspects of trilobite predation during the Palaeozoic are reviewed, with emphasis placed on their ability to withstand substantial injuries and the possible repair mechanisms that promoted wound healing and survival.

Three forms of exuviation, involving inversion of exoskeletal elements, are described in three Australian species of the Cambrian trilobite Redlichia: R. forresti (Foord), R. idonea Whitehouse and R. micrograpta Opik. They are: inversion of the pygidium, in four specimens of R. forresti; inversion of some thoracic segments of R. idonea; and lateral inversion of a free cheek, in single specimens of R. forresti and R. micrograpta. This is the first record of thoracic segment inversion during exuviation in trilobites. Exuviae with inverted exoskeletal elements provide information on the techniques of exuviation, in particular the direction of egression of the postecdysial trilobite from the proecdysial exuvia and also in this genus, the extent of enrolment of the thorax.

A new species of trilobite, Doublatia matheri is described from the Early Permian Colraine Mudstone (Manning Group) of the Kimbriki district, near Wingham in central eastern New South Wales. Further Early Permian faunas are recorded from the diamictites of the ‘Kullatine Series’ underlying the Manning Group.

Comparisons of conodont and trilobite communities from the Arenig-Llanvirn of northern Spitsbergen show that both groups were influenced by the same environmental factors, related to a shallow to deep water profile at the western edge of the proto-Atlantic Ocean (Iapetus). The majority of both conodonts and trilobites had benthic or nektobenthic habits; a few genera of both groups were pelagic. Temperature was a major influence on the distribution of conodonts; similar genera could occur on both sides of ancient oceans (e.g. Iapetus) given the same temperature regime.

Four different types of structures on fossil arthropods are shown to have been grouped under the term ‘genal caeca’. These are distinguished and the most conspicuous (i.e. the fine radiating cephalic ridges of trilobites that anastomose repeatedly before joining a major ridge in the border) are interpreted as the external representation of auxiliary respiratory systems at least in some Cambrian genera. A number of possible functions are considered for these ridges and none but respiration is found to be feasible. Supportive evidence for the hypothesis outlined is drawn from consideration of the paradigm for a dorsal respiratory system and from a comparison with living crustacea.

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.

Heterochrony, that is phyletic change in the onset or timing of morphological development, is considered to have been the principal factor affecting the evolution of a number of xystridurine trilobite species during the Middle Cambrian. Galahetes shows morphological and size characteristics which indicate that precocious maturation, that is progenesis, was the process responsible for its paedomorphic evolution during the Templetonian Stage. The morphological characteristics of adult Galahetes parallel those found in juvenile stages of Xystridura templetonensis, whose morphology is essentially that of the conservative, structurally ancestral xystridurine stem form which persisted through the Ordian and Templetonian Stages. Both X. altera and X. dunstani are also considered to have evolved from this stem form by paedomorphosis during the Templetonian Stage. In these species, however, the process is thought to have been neoteny, whereby retardation of somatic development resulted in retention of characters w...

Analysis of closely spaced and rich collections of trilobites across the base of the Pterocephaliid biomere shows a distinctive pattern of changes in relative abundance of trilobites and in trilobite diversity. These patterns are repeated at the base and top of the overlying Ptychaspid biomere, but they are near the basal boundaries of, or within, the Irvingella major and Corbinia apopsis Subzones respectively, rather than at the tops of these subzones. Thus, biomere boundaries are not consistently reflected by biostratigraphic boundaries of uniform importance in the current North American trilobite assemblage zone stratigraphy. The positions of the lower and upper boundaries of the Ptychaspid biomere are here revised downward to the bases of the I. major and C. apopsis subzones. As a consequence, they are now consistent with major changes in inarticulate brachiopod and conodont faunas. The evolutionary sequence within a biomere now commences with a brief ‘crisis’ period during which rare elements of the ...

The graptolite-bearing sequence across the Ordovician-Silurian boundary at Darraweit Guim, central Victoria is subdivided into four biostratigraphic units: the Dicellograptus ornatus-Climacograptus latus Zone, Climacograptus? extraordinarius Zone, Glyptograptus? persculptus Zone and Parakidograptus acuminatus Zone. Diagnostic graptolites of the upper three zones are described, and the trilobite D. (Dalmanitina) darraweitensis Campbell, characteristic of the C? extraordinarius Zone, is revised and assigned to the genus Songxites Lin within the subfamily Mucronaspidinae. Detailed correlation of the Darraweit Guim sequence with the Ordovician-Silurian boundary sequences of Dob's Linn (Scotland), Mirny Creek (northeastern Siberia), Chu-Ili Range (Kazakhstan), the Yangtze Gorge region (Hubei) and the northern Cordillera (Canada) is made on the basis of short-lived, cosmopolitan graptolite species. The relevant rock units at Darraweit Guim are defined for the first time.

An assemblage of well-preserved Devonian trilobites is described from limestones in Satun Province, southern Thailand. The biogeographic implications are briefly discussed. The fauna, which is of Early Devonian age, probably Emsian, includes Decoroproetus, Cornuproetus, Platyscutellum and two species of Reedops, one of which is new. No similar fauna has been described before from the Shan-Thai block. The fauna is a typical Hercynian assemblage with close specific comparisons with Turkey, Morocco and Bohemia.