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Duck K. Choi - One of the best experts on this subject based on the ideXlab platform.
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recent advances of Trilobite research in korea taxonomy biostratigraphy paleogeography and ontogeny and phylogeny
Geosciences Journal, 2017Co-Authors: Duck K. Choi, Tae-yoon ParkAbstract:Trilobites are among the most diverse and abundant fossil groups in Korea and occur in the Cambrian–Ordovician Joseon Supergroup of the Taebaeksan Basin. The Cambrian–Ordovician Trilobites of the Joseon Supergroup have been intensively studied during the last quarter century, with emphasis on taxonomic revision, refining biostratigraphic zonation, paleogeographic implications, and ontogeny and phylogeny. A total of 243 species have hitherto been known to occur in the Joseon Supergroup of the Taebaeksan Basin: 118 and 110 species were reported in the Taebaek and Yeongwol groups, respectively, whilst 15 species were described from the Mungyeong Group. Contrasting Trilobite faunal contents of the Taebaek and Yeongwol/Mungyeong groups resulted in two separate biostratigraphic schemes for the Cambrian–Ordovician of the Taebaeksan Basin: 22 biozones or fossiliferous horizons were recognized in the Taebaek Group; 19 zones were established in the Yeongwol Group; and four biozones were known from the Mungyeong Group. These Trilobite biozones of the Taebaeksan Basin can be correlated well with those of North China, South China, and Australia. The distribution of some of the Cambrian and Ordovician endemic Trilobites and the detrital zircon spectra of the pertinent areas suggest that the Sino-Korean Craton was located at the margin of east Gondwana and was separated from the South China Craton by an oceanic basin, and that the Taebaeksan Basin was a part of an epeiric sea in east Gondwana. Focus of the ontogenetic research of Korean Trilobites was initially on the Cambrian Trilobites from the Machari Formation of the Yeongwol Group, and then, was shifted to the silicified sclerites dissolved out of the carbonates of the Guzhangian to Tremadocian strata of the Taebaek Group, which have played a crucial role in resolving the Trilobite phylogeny. Still, much of the carbonate strata of the Taebaek Group containing silicified Trilobites has remained unstudied. The future ontogenetic research on the Trilobites from the middle Cambrian (Cambrian Series 3) and the Furongian strata of the Taebaek Group would significantly contribute to elucidating the muddled Trilobite phylogeny.
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global cambrian Trilobite palaeobiogeography assessed using parsimony analysis of endemicity
Geological Society London Memoirs, 2013Co-Authors: Javier J Alvaro, Duck K. Choi, L Babcock, Per Ahlberg, Osvaldo L Bordonaro, Roger A Cooper, Gappar Kh Ergaliev, Wesley I Gapp, Mansoureh Ghobadi PourAbstract:Abstract Palaeobiogeographical data on Cambrian Trilobites obtained during the twentieth century are combined in this paper to evaluate palaeoceanographic links through c. 30 myr, once these arthropods biomineralized. Worldwide major tectonostratigraphic units are characterized at series intervals of Cambrian time and datasets of Trilobite genera (629 for Cambrian Series 2, 965 for Cambrian Series 3, and 866 for the Furongian Series) are analysed using parsimony analysis of endemicity. Special attention is given to the biogeographical observations made in microcontinents and exotic terranes. The same is done for platform-basinal transects of well-known continental margins. The parsimony analysis of endemicity analysis resulted in distinct palaeogeographical area groupings among the tectonostratigraphic units. With these groupings, several palaeobiogeographical units are distinguished, which do not necessarily fit the previously proposed biogeographical realms and provinces. Their development and spatial distributions are broadly controlled by Cambrian palaeoclimates, palaeogeographical conditions (e.g. carbonate productivity and anoxic conditions) and ocean current circulation. Supplementary material: Global dataset of Cambrian Epoch 2 (A), Cambrian Epoch 3 (B) and the Furongian Epoch (C) Trilobite genera are provided at: http://www.geolsoc.org.uk/SUP18669
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Trilobite faunal successions across the base of the furongian series in the taebaek group taebaeksan basin korea
Geobios, 2011Co-Authors: Tae-yoon Park, Duck K. ChoiAbstract:Abstract The base of the Furongian Series in the Sino-Korean Block has not been clearly defined due to the lack of the index taxon, Glyptagnostus reticulatus. The Sesong Formation of the Taebaek Group, Taebaeksan Basin, Korea, has been known to range from the Guzhangian Stage of the Cambrian Series 3 to the middle Furongian Series, hence embracing the base of the Furongian Series. Silicified polymerid Trilobites were recovered from the middle part of the Sesong Formation. Described are a total of 18 polymerid species of 13 genera: Neodrepanura sp. 1, Teinistion sp. 1, Huzhuia sp. 1, Huzhuia sp. 2, Liostracina simesi, Liostracina sp. 1, Parachangshania monkei, Parachangshania rectangularis nov. sp., Placosema bigranulosum, Fenghuangella laevis nov. sp., Baikadamaspis jikdongensis nov. sp., Baikadamaspis sp. 1, Prochuangia mansuyi, Maladioides coreanicus, Alataspis sesongensis nov. gen., nov. sp., Chuangia sp. 1, and ceratopygids genus and species indeterminate 1 and 2. The stratigraphic occurrence of these Trilobites provides a basis for recognition of five zones across the base of the Furongian Series (in ascending order): the Neodrepanura, Liostracina simesi, Fenghuangella laevis, Prochuangia mansuyi, and Chuangia zones. The Neodrepanura and Chuangia zones are provisionally adopted from the previous biostratigraphic scheme, while the three other ones are newly proposed. The recommended base of the Furongian Series in the Taebaek Group of Korea coincides with the base of the Fenghuangella laevis Zone, which appears to represent an episode of profound Trilobite faunal turnover.
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Constraints on using ontogenetic data for Trilobite phylogeny
Lethaia, 2011Co-Authors: Tae-yoon Park, Duck K. ChoiAbstract:In the latter half of the twentieth century, studies of ontogeny had a vital influence on Trilobite systematics. Protaspid morphology especially has been regarded as one of the most significant criteria in classifying Trilobites (Whittington 1957; Palmer 1962; Robison 1967; Fortey & Owens 1975; Chatterton 1980; Edgecombe et al. 1988; Fortey & Chatterton 1988; Speyer & Chatterton 1989; Fortey 1990, 2001; Edgecombe 1992; Chatterton et al. 1994, 1999; Lee & Chatterton 2003, 2007; Campbell & Chatterton 2009). Although it has been pointed out that a versatile morphological diversity of Trilobite larvae could be independent of mature morphology (Bergstrom 1977; Lane & Thomas 1983; Thomas & Holloway 1988), protaspid morphology has been widely used for the higher-level classification of Trilobites. For instance, the Order Phacopida was recognized by a morphologically distinctive protaspis with three prominent marginal spines in a characteristic disposition and a forwardly expanding glabella (Whittington 1957). Fortey & Owens (1975) claimed that one of the main characters of the Order Proetida was the protaspides having a preglabellar field. The protaspides of the members of the Order Asaphida were known to have a unique globular shape (Fortey & Chatterton 1988; Fortey 1990). This protaspis-based approach for suprageneric classification of Trilobites has been proved to be successful so far and the morphological information from protaspides is expected to help elucidate many of unsolved conundrums in Trilobite systematics (Fortey 2001). Whittington (1957) proposed that great emphasis should be given to protaspid morphology in Trilobite classification, and the application of this idea to the study of post-Cambrian Trilobites has been quite successful (Whittington 2007). This is in part attributable to already distant phylogenetic relationship between the post-Cambrian Trilobite orders. One of the seemingly intractable problems in Trilobite phylogeny is to find the Cambrian ‘roots’ of post-Cambrian Trilobites, and Cambrian ptychoparioid ontogenies are expected to help elucidate the problem (Fortey 2001). However, even though many protaspides of the Cambrian ptychoparioids have been reported (see Chatterton & Speyer 1997 for full list and Lee & Chatterton 2007 and references therein), Trilobite phylogeny still seems to be far from being resolved. The current state-of-play in Trilobite systematics, in which protaspid morphology has played a significant role, is rooted in von Baer’s rule, and this rule has been applied well to Trilobites. Hence, ontogenetic studies are expected to reveal the currently unresolved phylogenetic relationships. Chatterton & Speyer (1997) mentioned ‘as a rule, monophyletic groups based on characteristics of adult growth stages have similar larvae and life-history strategies so that larval morphology appears to be a useful indicator of relationship’, implying that protaspides are more informative for systematics than later growth stages. However, von Baer’s rule does not always apply well. Recently, Poe (2006) quantitatively tested von Baer’s rule and raised doubts about the rule per se. A similar conclusion has been drawn for the phylogenetic use of the crustacean nauplius. Dahms (2000) pointed out significant differences in the morphology of nauplii of closely related species and emphasized that, for phylogenetic use, characters of the whole ontogenetic sequence including the adults should be considered and evaluated. These studies raise the possibility that protaspid morphology alone is not as useful as traditionally expected. With the application of von Baer’s rule to Trilobites aside, the validity of using protaspid morphology in Trilobite classification has seldom been questioned from a logical perspective. Even if the hypothesis that Trilobites with similar protaspides share a common ancestry is considered to have withstood the test of time rather well (Fortey 2001), there seems a logical pitfall that is derived from tradition rather than sound scientific reasoning.
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ontogeny of the furongian late cambrian remopleuridioid Trilobite haniwa quadrata kobayashi 1933 from korea implications for Trilobite taxonomy
Geological Magazine, 2011Co-Authors: Tae-yoon Park, Duck K. ChoiAbstract:The monophyly of the Trilobite Order Asaphida has been challenged. The Superfamily Remopleuridioidea was included in the Order Asaphida, based on the ventral median suture and highly bulbous protaspis of the late Furongian–Tremadocian representatives of the group. The remopleuridioid, Haniwa quadrata Kobayashi, 1933 from the Furongian (late Cambrian) Hwajeol Formation of Korea, represents a primitive morphology of the Remopleuridioidea. This Trilobite does not have a typical globular morphology of asaphoid protaspis, and the free cheeks remained yoked together during the whole of the development. This supports the previous proposition that the Superfamily Remopleuridioidea should be excluded from the Order Asaphida. In addition, the evolution of a highly globular protaspis of the Ordovician remopleuridioid Trilobites from the less bulbous protaspis corroborates the possibility of multiple evolutions of a highly globular protaspis. It can be argued that the possession of a highly globular protaspis does not guarantee the membership of the Order Asaphida, and thus the concept of the Order Asaphida should be emended.
Nigel C Hughes - One of the best experts on this subject based on the ideXlab platform.
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thoracic structure and enrolment style in middle cambrian eccaparadoxides pradoanus presages caudalization of the derived Trilobite trunk
Palaeontology, 2013Co-Authors: Jorge Esteve, Nigel C Hughes, Samuel ZamoraAbstract:The ability to enrol effectively evolved several times among Trilobites. Here, we show that, unlike most redlichiid Trilobites that could not enrol, both morphotypes of Eccaparadoxides pradoanus from the middle Cambrian of Spain enrolled so as to enclose most of the ventral surface beneath the exoskeleton and possessed specialized articulat- ing devices that facilitated this behaviour. The holaspid tho- rax of all E. pradoanus was divided into two principal regions. The boundary between these marked a transition from anterior segments with short pleural spines, fulcra and ridge-and-groove inner pleural regions to posterior seg- ments with longer, acuminate pleural spines that lack fulcra and inner pleural regions. Devices that aid articulation, such as fulcra with short articulating pleural surfaces, the petaloid articulating facet and long articulating half rings, are concentrated in the anterior region. These features, and the large number of specimens preserved in various degrees of enrolment, suggest an enrolment procedure in which the rear part of the trunk, containing both the posterior thorax and the pygidium, rotated as a single unit without signifi- cant internal flexure. As these posterior trunk articulations were apparently not required to permit enrolment, concen- trating flexure in the anterior may have presaged the cau- dalized condition seen in many derived Trilobite groups that encapsulated, in which a larger proportion of the trunk segments were allocated to the mature pygidium, and there- fore unable to articulate.
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purujosa Trilobite assemblage and the evolution of Trilobite enrollment
Geology, 2011Co-Authors: Jorge Esteve, Nigel C Hughes, Samuel ZamoraAbstract:Localities bearing abundant enrolled Cambrian Trilobites are extremely rare, but here we report a new and exceptional such assemblage with a high diversity of enrolled specimens from the middle Cambrian of Spain. This novel find demonstrates that encapsulated enrollment was a behavioral response available to many of the early benthic Trilobite morphotypes. This result provides a new perspective for reviewing the evolution of Trilobite enrollment through the Paleozoic. We find a significant and consistent increase in the proportion of enrolled Trilobites within assemblages bearing abundant articulated Trilobites. Similarly, the mean number of coaptative devices also increased progressively during the Paleozoic. Such devices likely provided later enrolled Trilobites with greater structural integrity, and may support an escalatory model of Trilobite defense evolution. Likewise, environmental circumstances favoring the preservation of enrolled Trilobites may have become more common during post-Cambrian time.
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microstratigraphy Trilobite biostratinomy and depositional environment of the lower cambrian ruin wash lagerstatte pioche formation nevada
Palaeogeography Palaeoclimatology Palaeoecology, 2008Co-Authors: Mark Webster, Robert R Gaines, Nigel C HughesAbstract:Abstract The uppermost 43 cm of Dyeran strata at the Ruin Wash Lagerstatte (Chief Range, Lincoln County, Nevada) contain nonmineralized invertebrates and exceptionally preserved, articulated olenelloid Trilobites. However, the environmental factors responsible for the preservation of olenelloids in this unusual state at Ruin Wash have received little study and are therefore poorly understood. Microstratigraphic analysis of this interval reveals that the strata, comprised almost exclusively of clay-sized particles and rather monotonous and featureless in outcrop, were deposited as a series of thin event beds interpreted as tempestites. The energy of deposition progressively waned then waxed through the interval, and benthic redox conditions shifted concurrently. Biostratinomic data for more than 500 Trilobite specimens encountered in the measured section reveal that the Trilobite fauna was autochthonous, although winnowed surfaces rich in bioclasts occurring at the base and top of the section indicate intervals of prolonged pre-burial exposure time and/or in situ reworking. Trilobite biostratinomy was strongly influenced by subtle environmental shifts: the degree of disarticulation and sclerite fracturing correlate positively with event bed energy and inferred bottom-water oxygen content. These results demonstrate that (1) preservation of articulated Trilobites is favoured near the distal limit of scouring associated with depositional events, where rapid sedimentation occurs in the absence of substrate reworking; and (2) differential taphonomic overprint on Trilobite preservation can occur within a monofacial succession, driven by subtle environmental change insufficient to leave a distinct lithological signature. This highlights the need for careful microstratigraphic, sedimentological, and ichnological analysis prior to comparison of palaeobiological or palaeoecological parameters inferred from fossil assemblages, even when the assemblages occur within the same lithofacies.
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the oldest known stalk eyed Trilobite parablackwelderia kobayashi 1942 damesellinae cambrian and its occurrence in shandong china
Journal of Paleontology, 2008Co-Authors: Shanchi Peng, Xianfeng Yang, Nigel C HughesAbstract:Parablackwelderia is the oldest known stalk-eyed Trilobite and thrived during the middle–late Cambrian (Guzhangian Age) in eastern Gondwanaland. The elongated palpebral lobe extends outward and forward from the anterior corner of the cranidium and shows positive allometry, becoming markedly longer and relatively thinner in large specimens. The animal occurred in muddy environments and may have been a predator that burrowed for concealment. Stalked-eyes were independently derived in several Trilobite clades, but whenever they appeared were restricted to small numbers of taxa and thus do not appear to have served as a key innovation that promoted extensive diversification of species bearing the structure. The stalk-eyed condition in Trilobites has a striking modern analog in the hypercephaly of diopsinid flies, where it is commonly associated with mate recognition and mate selection. We document the first occurrence of Parablackwelderia in Shandong, North China and describe a new species, Parablackwelderia luensis sp. nov.
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the evolution of Trilobite body patterning
Annual Review of Earth and Planetary Sciences, 2007Co-Authors: Nigel C HughesAbstract:The good fossil record of Trilobite exoskeletal anatomy and ontogeny, coupled with information on their nonbiomineralized tissues, permits analysis of how the Trilobite body was organized and developed, and the various evolutionary modifications of such patterning within the group. In several respects Trilobite development and form appears comparable with that which may have characterized the ancestor of most or all euarthropods, giving studies of Trilobite body organization special relevance in the light of recent advances in the understanding of arthropod evolution and development. The Cambrian diversification of Trilobites displayed modifications in the patterning of the trunk region comparable with those seen among the closest relatives of Trilobita. In contrast, the Ordovician diversification of Trilobites, although contributing greatly to the overall diversity within the clade, did so within a narrower range of trunk conditions. Trilobite evolution is consistent with an increased premium on effective enrollment and protective strategies, and with an evolutionary trade-off between the flexibility to vary the number of trunk segments and the ability to regionalize portions of the trunk.
Shanchi Peng - One of the best experts on this subject based on the ideXlab platform.
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cambrian Trilobite biostratigraphy and its role in developing an integrated history of the earth system
Lethaia, 2017Co-Authors: L Babcock, Shanchi Peng, Per AhlbergAbstract:One of the principal biostratigraphical tools used in the lower Palaeozoic, and especially the Cambrian System, is Trilobites. Historically, both polymerids and agnostoids have commonly been included as 'Trilobite' groups, although currently the question of whether they comprise a monophyletic group or are polyphyletic is unsettled. Beginning in the late 1800s, the base of the Cambrian System was marked by the lowest occurrence of olenelline Trilobites. Discovery of a rich pre-Trilobite metazoan record in the mid-1900s led to significant modification of that concept, but polymerids and especially agnostoids still rank among the leading biostratigraphical and chronostratigraphical guides through much of the Cambrian. Chronostratigraphical sub-division of the Trilobite-bearing part of the Cambrian System derives largely from biostratigraphical, ecological and evolutionary concepts about agnostoids and polymerids introduced in the 1940s to 1970s by A.H. Westergard, A.R. Palmer and R.A. Robison. Westergard introduced a zonation for Scandinavia that was largely based on agnostoids. Palmer explained the distribution of Cambrian Trilobite faunas in terms of restricted and unrestricted access to open oceans. Together, these ideas coalesced in Robison's recognition of separate zonation schemes for restricted-shelf polymerids, open-shelf polymerids and open-shelf (cosmopolitan) agnostoids. Palmer also introduced the concept of biomeres, which placed sharp limits on biostratigraphical intervals recognizable from Trilobites. Global correlation in the upper half of the Cambrian today depends to a large extent on the ranges of agnostoids and some polymerids characteristic of open-shelf to slope areas, ones that facilitate identification of precise intercontinental tie points. Agnostoid and polymerid biostratigraphy is now being integrated with information about coastal onlap and eustatic sea-level history, geochemical cycling and other data to provide a more complete understanding of the early Palaeozoic biosphere and its complex physico-chemical context.
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morphology and development of the eodiscoid Trilobite tsunyidiscus yanjiazhaiensis from the cambrian stage 3 series 2 of south china
Journal of Systematic Palaeontology, 2016Co-Authors: Xingliang Zhang, Shanchi PengAbstract:The post-protaspid ontogenetic series of the eodiscinid Trilobite Tsunyidiscus yanjiazhaiensis S. Zhang et al. in Yin & Li, 1978 is described, on the basis of crack-out specimens including numerous articulated specimens and a large number of disarticulated sclerites from the lower Cambrian (Stage 3, Series 2) Shuijingtuo Formation, Zhenba County, Shaanxi Province, South China. In addition, hundreds of phosphatized sclerites assigned to this species were obtained by dilute acetic acid dissolution of thin-bedded limestones from the same horizon. These sclerites exhibit considerable morphological detail and even some delicate structures, such as the axial pores and marginal spines on the pygidium and the bacculae that can be retained from the protaspid to the holaspid period. Ontogenetic study of T. yanjiazhaiensis provides new evidence to support and reconfirm the unique developmental pattern shared by early Cambrian eodiscoid Trilobites, i.e. the processes of liberation of the thoracic segment and segment ...
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morphology and ontogeny of hunanocephalus ovalis Trilobite from the cambrian of south china
Gondwana Research, 2014Co-Authors: Xingliang Zhang, Shanchi PengAbstract:article i nfo The juvenile morphology and ontogeny of the Cheiruroidid Trilobite Hunanocephalus ovalis Lee, 1963 from the lower Cambrian Shuijingtuo Formation in Hubei Province, South China is presented. The new material com- prises a relatively complete meraspid ontogenetic series (degree 0 to 10), which reveals more details on their morphological changes such as the contraction and disappearance of the pronounced posteromedial notch in the pygidium and the addition of the trunk segments, which are all documented for the first time and can also be used as developmental markers defining their ontogenetic phases. The trunk segmentation schedule of H. ovalis is also discussed, which is similar to the other early Cambrian oryctocephalid Trilobites, i.e. as the boundary between the thorax and pygidium migrated posteriorly there is no change in the trunk segment number; the processes of liberation of the thoracic segment and segment insertion into the pygidium are separated from one another, implying that the control of trunk exoskeletal segment appearance and articulation might be decoupled in these Trilobites.
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the oldest known stalk eyed Trilobite parablackwelderia kobayashi 1942 damesellinae cambrian and its occurrence in shandong china
Journal of Paleontology, 2008Co-Authors: Shanchi Peng, Xianfeng Yang, Nigel C HughesAbstract:Parablackwelderia is the oldest known stalk-eyed Trilobite and thrived during the middle–late Cambrian (Guzhangian Age) in eastern Gondwanaland. The elongated palpebral lobe extends outward and forward from the anterior corner of the cranidium and shows positive allometry, becoming markedly longer and relatively thinner in large specimens. The animal occurred in muddy environments and may have been a predator that burrowed for concealment. Stalked-eyes were independently derived in several Trilobite clades, but whenever they appeared were restricted to small numbers of taxa and thus do not appear to have served as a key innovation that promoted extensive diversification of species bearing the structure. The stalk-eyed condition in Trilobites has a striking modern analog in the hypercephaly of diopsinid flies, where it is commonly associated with mate recognition and mate selection. We document the first occurrence of Parablackwelderia in Shandong, North China and describe a new species, Parablackwelderia luensis sp. nov.
Martin Stein - One of the best experts on this subject based on the ideXlab platform.
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arthroaspis n gen a common element of the sirius passet lagerstatte cambrian north greenland sheds light on Trilobite ancestry
BMC Evolutionary Biology, 2013Co-Authors: Martin Stein, John S Peel, Graham E Budd, David A T HarperAbstract:Background Exceptionally preserved Palaeozoic faunas have yielded a plethora of Trilobite-like arthropods, often referred to as lamellipedians. Among these, Artiopoda is supposed to contain taxa united by a distinctive appendage structure. This includes several well supported groups, Helmetiida, Nektaspida, and Trilobita, as well as a number of problematic taxa. Interrelationships remain unclear, and the position of the lamellipedian arthropods as a whole also remains the subject of debate.
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isoxys arthropoda with preserved soft anatomy from the sirius passet lagerstatte lower cambrian of north greenland
Lethaia, 2009Co-Authors: Martin Stein, Derek J Siveter, John S Peel, M WilliamsAbstract:Arthropods have a rich fossil record spanning the Phanerozoic. Biomineralized forms such as the extinct Trilobites are particularly common and are proven index fossils for biostratigraphy. Forms with an unmineralized cuticle are more rare, preserved only in so called konservat lagerstatten. Cambrian strata of Greenland have yielded rich Trilobite faunas with potential for intercontinental correlation of Cambrian strata, but also an exceptionally preserved fauna, the Sirius Passet Lagerstatte. The first part of this thesis is concerned with Trilobite biotratigraphy of the provisional Cambrian Series 2 in Greenland. The second part is concerned with exceptionally preserved arthropods from the Sirius Passet Lagerstatte, but also from 'Orsten' deposits from the Cambrian of Sweden. Perissopyge phenax occurs in the Henson Gletscher and Paralleldal formations spanning the Series 2 and 3 boundary interval in North Greenland. It also occurs in the Sekwi Formation of Yukon Territory, demonstrating that the species may hold potential for correlation within Laurentia. An indeterminate species of Perissopyge is shown to occur in the Ella Island Formation of North-East Greenland together with Olenellus cf. hanseni, which is similar to Olenellus cf. truemani described from the Henson Gletscher Formation. If this correlation is further corroborated it would offer a first tie-point for the An t'Sron Formation of North-West Scotland which yields Fritzolenellus lapworthi, herein reported for the first time from the Bastion Formation which underlies the Ella Island Formation. Oelandocaris oelandica from ‘Orsten’ deposits in the Cambrian series 3 and 4 boundary interval in Sweden is an early representative of the Crustacean stem lineage. Kiisortoqia avannaarsuensis is a new arthropod from the Sirius Passet Lagerstatte with robust antennulae strikingly similar to the 'raptorial' limb of the problematic anomalocaridids. The ventral morphology of the 'bivalved' Isoxys volucris is described for the first time and compared with other species assigned to Isoxys from Cambrian lagerstatten around the world. Finally, Siriocaris trolla, is a new arthropod that similarities with Trilobites and certain ‘trilobitomorphs’ but seems to lack important synapomorphies of these taxa, though this may be due to preservational limitations in the material at hand.
Tae-yoon Park - One of the best experts on this subject based on the ideXlab platform.
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recent advances of Trilobite research in korea taxonomy biostratigraphy paleogeography and ontogeny and phylogeny
Geosciences Journal, 2017Co-Authors: Duck K. Choi, Tae-yoon ParkAbstract:Trilobites are among the most diverse and abundant fossil groups in Korea and occur in the Cambrian–Ordovician Joseon Supergroup of the Taebaeksan Basin. The Cambrian–Ordovician Trilobites of the Joseon Supergroup have been intensively studied during the last quarter century, with emphasis on taxonomic revision, refining biostratigraphic zonation, paleogeographic implications, and ontogeny and phylogeny. A total of 243 species have hitherto been known to occur in the Joseon Supergroup of the Taebaeksan Basin: 118 and 110 species were reported in the Taebaek and Yeongwol groups, respectively, whilst 15 species were described from the Mungyeong Group. Contrasting Trilobite faunal contents of the Taebaek and Yeongwol/Mungyeong groups resulted in two separate biostratigraphic schemes for the Cambrian–Ordovician of the Taebaeksan Basin: 22 biozones or fossiliferous horizons were recognized in the Taebaek Group; 19 zones were established in the Yeongwol Group; and four biozones were known from the Mungyeong Group. These Trilobite biozones of the Taebaeksan Basin can be correlated well with those of North China, South China, and Australia. The distribution of some of the Cambrian and Ordovician endemic Trilobites and the detrital zircon spectra of the pertinent areas suggest that the Sino-Korean Craton was located at the margin of east Gondwana and was separated from the South China Craton by an oceanic basin, and that the Taebaeksan Basin was a part of an epeiric sea in east Gondwana. Focus of the ontogenetic research of Korean Trilobites was initially on the Cambrian Trilobites from the Machari Formation of the Yeongwol Group, and then, was shifted to the silicified sclerites dissolved out of the carbonates of the Guzhangian to Tremadocian strata of the Taebaek Group, which have played a crucial role in resolving the Trilobite phylogeny. Still, much of the carbonate strata of the Taebaek Group containing silicified Trilobites has remained unstudied. The future ontogenetic research on the Trilobites from the middle Cambrian (Cambrian Series 3) and the Furongian strata of the Taebaek Group would significantly contribute to elucidating the muddled Trilobite phylogeny.
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Head segmentation of Trilobites
Lethaia, 2016Co-Authors: Tae-yoon Park, Ji-hoon KihmAbstract:Although Trilobites have provided research subjects for more than two centuries, their head segmentation has remained unresolved. Four glabellar furrows (SO and S1–S3) marking the segmental boundaries are generally present in the cephalic axis, but there are Trilobites with one more pair of furrows, the so-called S4, in the cephalic axis, causing confusion in understanding Trilobite head segmentation. Recent advances in developmental biology and palaeontology have shed light on the arthropod head problem, and thus, Trilobite head segmentation can be reviewed in the light of this knowledge. Based on the information from the anatomy of exceptionally preserved Trilobites and artiopodans closely related to Trilobites, it is inferred that Trilobite head contains five segments: the anteriormost ocular segment potentially associated with the hypostome, the antennal segment and the following three segments with walking legs. When present, the S4 furrows are situated where the eye ridges meet the cephalic axis of Trilobites, indicating that the furrows are incised ‘within’ the anteriormost segment in Trilobites with an anteriorly enlarged frontal lobe. Trilobites of the Order Redlichiida, the most primitive stock, show variable conditions in the frontal glabellar conditions, while in other more derived groups, the condition is rather constant. The frontal glabellar condition, therefore, could provide a clue to elucidate the unresolved Cambrian Trilobite phylogeny and the Cambrian roots of the post-Cambrian Trilobites.
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Trilobite faunal successions across the base of the furongian series in the taebaek group taebaeksan basin korea
Geobios, 2011Co-Authors: Tae-yoon Park, Duck K. ChoiAbstract:Abstract The base of the Furongian Series in the Sino-Korean Block has not been clearly defined due to the lack of the index taxon, Glyptagnostus reticulatus. The Sesong Formation of the Taebaek Group, Taebaeksan Basin, Korea, has been known to range from the Guzhangian Stage of the Cambrian Series 3 to the middle Furongian Series, hence embracing the base of the Furongian Series. Silicified polymerid Trilobites were recovered from the middle part of the Sesong Formation. Described are a total of 18 polymerid species of 13 genera: Neodrepanura sp. 1, Teinistion sp. 1, Huzhuia sp. 1, Huzhuia sp. 2, Liostracina simesi, Liostracina sp. 1, Parachangshania monkei, Parachangshania rectangularis nov. sp., Placosema bigranulosum, Fenghuangella laevis nov. sp., Baikadamaspis jikdongensis nov. sp., Baikadamaspis sp. 1, Prochuangia mansuyi, Maladioides coreanicus, Alataspis sesongensis nov. gen., nov. sp., Chuangia sp. 1, and ceratopygids genus and species indeterminate 1 and 2. The stratigraphic occurrence of these Trilobites provides a basis for recognition of five zones across the base of the Furongian Series (in ascending order): the Neodrepanura, Liostracina simesi, Fenghuangella laevis, Prochuangia mansuyi, and Chuangia zones. The Neodrepanura and Chuangia zones are provisionally adopted from the previous biostratigraphic scheme, while the three other ones are newly proposed. The recommended base of the Furongian Series in the Taebaek Group of Korea coincides with the base of the Fenghuangella laevis Zone, which appears to represent an episode of profound Trilobite faunal turnover.
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Constraints on using ontogenetic data for Trilobite phylogeny
Lethaia, 2011Co-Authors: Tae-yoon Park, Duck K. ChoiAbstract:In the latter half of the twentieth century, studies of ontogeny had a vital influence on Trilobite systematics. Protaspid morphology especially has been regarded as one of the most significant criteria in classifying Trilobites (Whittington 1957; Palmer 1962; Robison 1967; Fortey & Owens 1975; Chatterton 1980; Edgecombe et al. 1988; Fortey & Chatterton 1988; Speyer & Chatterton 1989; Fortey 1990, 2001; Edgecombe 1992; Chatterton et al. 1994, 1999; Lee & Chatterton 2003, 2007; Campbell & Chatterton 2009). Although it has been pointed out that a versatile morphological diversity of Trilobite larvae could be independent of mature morphology (Bergstrom 1977; Lane & Thomas 1983; Thomas & Holloway 1988), protaspid morphology has been widely used for the higher-level classification of Trilobites. For instance, the Order Phacopida was recognized by a morphologically distinctive protaspis with three prominent marginal spines in a characteristic disposition and a forwardly expanding glabella (Whittington 1957). Fortey & Owens (1975) claimed that one of the main characters of the Order Proetida was the protaspides having a preglabellar field. The protaspides of the members of the Order Asaphida were known to have a unique globular shape (Fortey & Chatterton 1988; Fortey 1990). This protaspis-based approach for suprageneric classification of Trilobites has been proved to be successful so far and the morphological information from protaspides is expected to help elucidate many of unsolved conundrums in Trilobite systematics (Fortey 2001). Whittington (1957) proposed that great emphasis should be given to protaspid morphology in Trilobite classification, and the application of this idea to the study of post-Cambrian Trilobites has been quite successful (Whittington 2007). This is in part attributable to already distant phylogenetic relationship between the post-Cambrian Trilobite orders. One of the seemingly intractable problems in Trilobite phylogeny is to find the Cambrian ‘roots’ of post-Cambrian Trilobites, and Cambrian ptychoparioid ontogenies are expected to help elucidate the problem (Fortey 2001). However, even though many protaspides of the Cambrian ptychoparioids have been reported (see Chatterton & Speyer 1997 for full list and Lee & Chatterton 2007 and references therein), Trilobite phylogeny still seems to be far from being resolved. The current state-of-play in Trilobite systematics, in which protaspid morphology has played a significant role, is rooted in von Baer’s rule, and this rule has been applied well to Trilobites. Hence, ontogenetic studies are expected to reveal the currently unresolved phylogenetic relationships. Chatterton & Speyer (1997) mentioned ‘as a rule, monophyletic groups based on characteristics of adult growth stages have similar larvae and life-history strategies so that larval morphology appears to be a useful indicator of relationship’, implying that protaspides are more informative for systematics than later growth stages. However, von Baer’s rule does not always apply well. Recently, Poe (2006) quantitatively tested von Baer’s rule and raised doubts about the rule per se. A similar conclusion has been drawn for the phylogenetic use of the crustacean nauplius. Dahms (2000) pointed out significant differences in the morphology of nauplii of closely related species and emphasized that, for phylogenetic use, characters of the whole ontogenetic sequence including the adults should be considered and evaluated. These studies raise the possibility that protaspid morphology alone is not as useful as traditionally expected. With the application of von Baer’s rule to Trilobites aside, the validity of using protaspid morphology in Trilobite classification has seldom been questioned from a logical perspective. Even if the hypothesis that Trilobites with similar protaspides share a common ancestry is considered to have withstood the test of time rather well (Fortey 2001), there seems a logical pitfall that is derived from tradition rather than sound scientific reasoning.
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ontogeny of the furongian late cambrian remopleuridioid Trilobite haniwa quadrata kobayashi 1933 from korea implications for Trilobite taxonomy
Geological Magazine, 2011Co-Authors: Tae-yoon Park, Duck K. ChoiAbstract:The monophyly of the Trilobite Order Asaphida has been challenged. The Superfamily Remopleuridioidea was included in the Order Asaphida, based on the ventral median suture and highly bulbous protaspis of the late Furongian–Tremadocian representatives of the group. The remopleuridioid, Haniwa quadrata Kobayashi, 1933 from the Furongian (late Cambrian) Hwajeol Formation of Korea, represents a primitive morphology of the Remopleuridioidea. This Trilobite does not have a typical globular morphology of asaphoid protaspis, and the free cheeks remained yoked together during the whole of the development. This supports the previous proposition that the Superfamily Remopleuridioidea should be excluded from the Order Asaphida. In addition, the evolution of a highly globular protaspis of the Ordovician remopleuridioid Trilobites from the less bulbous protaspis corroborates the possibility of multiple evolutions of a highly globular protaspis. It can be argued that the possession of a highly globular protaspis does not guarantee the membership of the Order Asaphida, and thus the concept of the Order Asaphida should be emended.
