Trilobite Family Research Articles

Taxonomy, biostratigraphy and paleobiogeography of Strenuaeva (Trilobita) from the Marianian (Cambrian Series 2) of Iberia

Problems surrounding the identification and systematics of taxa belonging to the trilobite family Ellipsocephalidae have been discussed for several decades. The ellipsocephalid genus Strenuaeva is revised herein on the basis of material from Spain, including the type material of the identified species together with newly collected specimens from the Ossa-Morena Zone and the Iberian Chains. Two species are recognized as valid for these regions: S. sampelayoi and S. incondita. The species ‘S. melendezi’ and ‘Ellipsostrenua alanisiana’ from Spain, as well as ‘S. marocana’ from Morocco, are considered junior synonyms of S. sampelayoi. Previous assignment of the Spanish species to Issafeniella is rejected. The abundant available material of S. sampelayoi made it possible to evaluate the taphonomical role in the preservation of some characters and to recognize intraspecific variability similar to that described in S. inflata from Baltica, reinforcing its assignment to Strenuaeva. Biostratigraphically, Strenuaeva ranges from uppermost Cambrian Stage 3 to uppermost Cambrian Stage 4. In Iberia, it is restricted to the middle Marianian in the Ossa-Morena Zone, whereas it is known from the lowermost middle Marianian to the lowermost upper Marianian in the Iberian Chains. Strenuaeva is known from Baltica (Scandinavia and Holy Cross Mountains, Poland), Iberia (Spain), Morocco and, possibly, western Avalonia (Newfoundland), hence being a characteristic genus of the Acadobaltic faunal Province.

Rise and fall of the phacopids: the morphological history of a successful trilobite family

AbstractPhacopidae were a successful family of the Silurian–Devonian period. Although their diversity trends are well identified, their shape evolution is unknown; their morphology often considered to be conservative. We have quantified these morphologies using geometric morphometrics (landmarks) and investigated their evolution using morphological disparity indices. Results identified morphological variations between the genera, and through time. Phacopids differ from each other by the position of the facial suture linked to the size of the visual complex, the shape of the genal angle and the elongation of both cephalon and pygidium. The morphological disparity of cephala was high from the Silurian, contrary to that of pygidia. Subsequently, the morphological disparity increased in the Early Devonian with the development of narrow cephala and triangular pygidia. Morphological disparity was greater in the Emsian for both cephala and pygidia, more than 50 myr after the origination of phacopids. It constituted a perfect example illustrating that a peak of biodiversity does not necessarily happen in the early history of a clade. Subsequently, a strong decrease of morphological disparity occurred in the Middle Devonian, in conjunction with sea‐level changes and anoxic events. Taxonomic richness and morphological disparity declined strongly in the Givetian, in a non‐random extinction affecting particularly blind genera. The morphological disparity remained low in the Frasnian despite progressive eye reduction influenced by environmental changes. An extensive recovery occurred in the Famennian with an important increase of both taxonomic and morphological diversity. The Hangenberg event caused the final extinction of phacopids.

Coupling of taxonomic diversity and morphological disparity in Devonian trilobites?

ABSTRACT Morphological disparity and taxonomic richness are two major aspects of evolution used to understand biodiversity changes. These metrics are often decoupled in time, particularly during the early history of clades. To assess the pervasiveness of this pattern during the post-acme of a clade, both morphological disparity and taxonomic diversity of the well-documented Devonian trilobites from North Africa were analysed. Morphospace occupancy and body size were estimated and compared to genus richness through time. This study highlights that, during the Early Devonian, morphological disparity of the pygidium and the cephalon strongly increased, whereas cranidium disparity remained low. Interestingly, the pygidium and cephalon morphological dynamics were decoupled. Taxonomic diversity also increased. Then, the Middle Devonian anoxic events affected the trilobite communities with simultaneous drastic loss of both morphologies and taxonomic richness. This coupling between diversity and disparity dynamics could be explained by either the intensity of extinctions or strong internal constraints. Finally, the weak Famennian recovery of both disparity and diversity did not reach the Early Devonian levels, thus making trilobites a ‘dead clade walking’ during their late evolutionary history. Devonian trilobite families are thus identified as ‘Bottom-Heavy Clades’, characterised by a diversity peak at the end of their history.

Phylogeny and evolutionary modularity of a trilobite family over the Ordovician Radiation

Phylogeny and evolutionary modularity of a trilobite family over the Ordovician Radiation

First described fossil representatives of the parasitoid wasp taxa Asaphesinae n. n. and Eunotinae (Hymenoptera: Chalcidoidea: Pteromalidae sensu lato) from Eocene Baltic amber

ABSTRACT New Baltic amber species of Pteromalidae sensu lato are described, from two different subfamilies, Asaphesinae n. n. and Eunotinae. Asaphesinae is provided as a replacement name for Asaphinae Ashmead 1904, which is a junior homonym of the trilobite family Asaphidae Burmeister 1843. Coriotela lasallei gen. n., sp. n.. and Butiokeras costae gen. n., sp. n.. are described as the first known fossil species of Asaphesinae and Eunotinae, respectively. These species establish the minimum known age of both groups in the Eocene. Taxonomic changes are also proposed for some extant species. The genus Desantisiana Neder de Román syn. n.. is found to be a junior synonym of Notoglyptus, and its only described species is transferred as Notoglyptus jujuyensis (Neder de Román) comb. n.. The tribe Calyconotiscini, previously classified in Eunotinae, is abolished and Calyconotiscus Narendran & Saleem is transferred to Pireninae. http://www.zoobank.org/urn:lsid:zoobank.org:pub:7A107FF9-28E7-40AA-8A9B-71321E476C07

First cladistic analysis of the trilobite family Olenidae from the Furongian and Ordovician

The Olenidae stands out for its abundance and biostratigraphical importance, especially in the Lower Palaeozoic rocks of northwestern Argentina. Their phylogenetic relationships have been traditionally determined stratigraphically and by direct morphological comparison. This study reports the first formal phylogenetic analysis of olenids. Eighty-six characters (24 quantitative and 62 qualitative) were coded for 65 taxa (58 olenids). Quantitative characters were treated both as discrete and as continuous variables. To explore the best way of character coding for this group, continuous characters were coded as: median, log-median, normalized and rescaled. Maximum parsimony and implied weighting were used as optimality criteria. A phylogenetic hypothesis more consistent with traditional taxonomy was reconstructed with both quantitative and qualitative partitions. All the trees obtained with quantitative characters coded as continuous and rescaled are better resolved, and those topologies were more similar among them. This treatment also reflects more effectively the behaviour of the original variables. Olenidae is not a monophyletic clade: Andrarina costata and Aphelaspis australis are included within the ingroup, as sister clade of Olenus gibbosus. Also, the results suggest that members of the Hypermecaspidinae constitute a new family within the Order Olenida. The traditional taxonomic scheme at subfamily level is partially supported. Triarthrinae and ‘pelturinds’ are recovered as monophyletic clades, but Oleninae is polyphyletic. This study proves, through a formal cladistic analysis, that characters disregarded by traditional taxonomy can be uncovered. Finally, this is the first step towards achieving a classification of the Olenidae taking into account the evolutionary process involved in its diversification history.

阿武隈山地・高倉山層群(ペルム紀)のPhillipsiidae新属三葉虫

阿武隈山地・高倉山層群(ペルム紀)のPhillipsiidae新属三葉虫

How well does a part represent the whole? A comparison of cranidial shape evolution with exoskeletal character evolution in the trilobite family Pterocephaliidae

AbstractFor taphonomic and practical reasons, our understanding of morphological evolution within and among species is based primarily on measurements taken from one or a few morphological traits. However, patterns can be highly dependent on trait choice, making it difficult to draw conclusions about evolution of species or clades as a whole. In this paper, I test whether patterns of evolutionary change in the shape of a part are coincident with patterns of evolutionary change based on a more comprehensive description of the organism. The former is based on geometric morphometrics of the trilobite cranidium and the latter on discrete character data describing the exoskeleton, collected from species belonging to the Cambrian family Pterocephaliidae. Using these two datasets, I compare the amount of change occurring along phylogenetic branches, as well as changes in morphospace occupation and changes in different measures of disparity. Unlike previous studies, I apply as similar a data treatment as possible to each data set in order to facilitate the comparison and interpretation of discrepancies. Results suggest that cranidial shape is a robust proxy for species‐level disparity and rates of evolution in this family of trilobites. This indicates that studies that have relied on data collected from the cranidium may be representative of the patterns that would be detected if more comprehensive description of the specimens had been available.

The Burlingiidae (Trilobita): revised generic composition, stratigraphy, and the first species from the early Middle Cambrian of West Gondwana

A single specimen of a new genus and species of the trilobite family Burlingiidae from the lower part of the Middle Cambrian in Morocco augments both the geographic distribution to the Cambrian continent West Gondwana and the modern continent Africa and the stratigraphic range of the family to base of the Middle Cambrian. A reconsideration of species assigned to Schmalenseeia requires a revision of the genus. Schmalenseeia acutangula Westergård, 1948, previously discussed as atypical for the genus Schmalenseeia, is separated as the type species of the new genus Niordilobites, and its characters and relation to the other Burlingiidae are discussed. Schmalenseeia jagoi Whittington, 1994 is discussed to differ from Schmalenseeia and Burlingia as well and is raised to the type species of Alumenella n. gen. Schmalenseeia fusilis Peng et al., 2004, unique because of the fusion of its tagmata, is the type species of the new genus Pengia. Burlingia laevis Westergård, 1936 is retained as a distinct species, and its suggested synonymy with Burlingia hectori is challenged. Additional discussions deal with a clarification of its stratigraphic origin, the possible origin of the clade, and morphological developments.http://zoobank.org/urn:lsid:zoobank.org:pub:79F59028-5C03-4AF5-891D-F08B6FECAC81

Chronostratigraphy and significance of the Rugosa Group (Cruziana, trace fossil) in the Ordovician strata of the South American Central Andean Basin

Although most trace fossils display long temporal ranges, certain forms as the Paleozoic mostly trilobite trace Cruziana have particular biostratigraphic significance. The evolution and replacement of trilobite families during the Paleozoic are reflected by the morphological characteristics of trace fossils that have contributed to interpret ages in the “non-fossiliferous” shallow marine Gondwanan realm. The “Cruziana stratigraphy” concept is based on this scheme, where different sets of traces replace each other on the stratigraphical record. The Cruziana rugosa Group is part of this scheme, and has been classically mis-referred as an exclusively Lower Ordovician element in the Central Andean Basin of South America. This contribution reevaluates the presence of the C. rugosa Group in the Lower to Middle Ordovician strata of the Cordillera Oriental and Subandean ranges of Argentina and in the Lower to Upper Ordovician of the Cordillera Oriental and Subandean ranges of Bolivia, and highlights its original distribution on its type area. The current paper displays a biostratigraphically-supported analysis of its record, also contributing with little known data from the northern sector of the continent, in the Colombian Andes.

Mansuyia Sun, and Tsinania Walcott, from the Furongian of North China and the evolution of the trilobite family Tsinaniidae

AbstractThe Furongian trilobite family Tsinaniidae is characterized by a highly effaced surface and forms an important constituent of the Furongian trilobite faunas of east Gondwana. However, the origin of the characteristic morphology of this family has remained unclear. Only recently has the tsinaniid trilobite Lonchopygella megaspina been suggested to represent an intermediate stage in the evolutionary transition to other tsinaniids on the basis of the trunk segmentation. Here, we report successive occurrences of four species of the kaolishaniid genus Mansuyia and a tsinaniid trilobite Tsinania canens from the Furongian (late Cambrian) Chaomidian Formation in Shandong Province, China. A cladistic analysis including these taxa reveals that the four species of Mansuyia constitute stem‐group taxa to the family Tsinaniidae, rendering Mansuyia and the Kaolishaniidae paraphyletic. The youngest species of Mansuyia, M. taianfuensis, turns out to be the immediate sister taxon of the Tsinaniidae, displaying a closely similar morphology to the tsinaniid trilobite, Shergoldia laevigata. The generic and familial boundary therefore situated between M. taianfuensis and S. laevigata.

Decoupling of taxonomic diversity and morphological disparity during decline of the Cambrian trilobite family Pterocephaliidae

Although discordance between taxonomic diversity and morphological disparity is common, little is known about the underlying dynamics that drive this decoupling. Early in the history of the Cambrian trilobite family Pterocephaliidae, there was an increase in taxonomic diversity and morphological diversity. As taxonomic diversity declined in the later history of the clade, range of variation stayed high and disparity continued to increase. However, per-branch rates of morphological evolution estimated from a recent phylogeny decreased with time. Neither within-trait nor within-species variation increased or decreased, suggesting that the declining rates of morphological evolution were more likely related to ecological opportunity or niche partitioning, rather than increasing intrinsic constraints. This is further supported by evidence for increased biofacies associations throughout the time period. Thus, the high disparity seen at low taxonomic diversity late in the history of this clade was due to extinction - either random or targeting mean forms - rather than increased rates of morphological evolution. This pattern also provides a scenario that could account for instances of low taxonomic diversity but high morphological disparity in modern groups.

Guzhangian (mid Cambrian) trilobites from siliceous concretions of the Valtorres Formation, Iberian Chains, NE Spain

AbstractIn the carbonate-siliciclastic strata of West Gondwana (e.g. in the Montagne Noire, France), the aftermath of the mid Languedocian (mid Cambrian) regression is characterized by a late Languedocian major turnover of trilobite families and a Furongian–early Tremadocian radiation related to the stepwise immigration of trilobite invaders from East Gondwana under persistent transgressive conditions. The scarcity of upper Languedocian fossil accumulations in clayey substrates has inspired the sampling of the palaeogeographically most distal parts of the Iberian Chains (Spain), where diagenetic dissolution of ubiquitous hexactinellid sponge spicules has favoured the formation of siliceous concretions. These have yielded the trilobitesPeronopsiscf.insignis,Oidalagnostus trispinifer,Proampyx difformis(=Proampyx aculeatus),Bailiaspis?glabrata(=Holocephalina agrauloides, by ontogeny),Holasaphuscf.centropygeand a paradoxidid gen. et sp. indet. Despite preservation and sampling biases, the identification of this taphonomic window in offshore clayey substrates of West Gondwana allows the recognition of a strong biogeographical link with Baltica, and the correlation of the global Guzhangian Stage and theSolenopleura?brachymetopaZone of Scandinavia with part of the Mediterranean upper Languedocian Substage.

Cope's rule in the Ordovician trilobite family Asaphidae (order Asaphida): patterns across multiple most parsimonious trees

Cope's rule defines lineages that trend towards an increase in body size through geological time. The trilobite family Asaphidae is one of the most diverse of the class Trilobita and ranges from the Upper Cambrian through to the Upper Ordovician. The group is one trilobite clades that displays a large size range and contains several of the largest trilobite species. Reduced major axis correlations between the lengths of cephala and pygidia and the total sagittal length of complete individuals have high support and were used to standardise all incomplete specimens to total axial length. Phylogenetic studies into Cope's rule tend to use supertrees, composite trees or a single tree selected through a fit criterion. Here, for the first time, all trees recovered from a maximum parsimony analysis were analysed equally. Maximum likelihood was used to fit four evolutionary models: random walk, directional, Ornstein–Uhlenbeck (evolution towards an adaptive optimum) and stasis. These were compared equally using Akaike weights. Fitting of evolutionary models by maximum likelihood supports stasis as consistently the most likely model across all trees with low support for directionality.

Middle Furongian (late Cambrian) shumardiids from the Sesong Formation, Taebaek Group, Korea

The trilobite family Shumardiidae is characterized by small size, lack of eyes, yoked librigenae, and a small number of thoracic segments. Here we report the successive occurrence of three middle Furongian shumardiid species from the Sesong Formation of Korea: Elaphraella? taebaeksanensis n. sp., Elaphraella microforma, and Elaphraella nodus. They appear to represent the oldest shumardiid morphology known so far. This genus lacks the anterolateral swellings on the glabella and has a conical glabella. Its yoked librigenae also encompass a comparatively wide genal field. Elaphraella? taebaeksanensis has a highly inflexed facial suture which may reflect the presence of small palpebral lobes. Taken together, the plesiomorphic morphology of the Shumardiidae can be summarized as having a conical glabella, small palpebral lobes, highly arched anterior cephalic margin, a wide librigenal field, and no anterolateral swellings on the glabella.

Phylogenetic and Biogeographic Analysis of Ordovician Homalonotid Trilobites

Cladistic parsimony analysis of the trilobite family Homalonotidae Chapman 1980 produced a hypothesis of re- latedness for the group. The family consists of three monophyletic subfamilies, one containing Trimerus Green 1832, Platycoryphe Foerste 1919, and Brongniartella Reed 1918; one containing Plaesiacomia Hawle and Corda 1847 and Col- pocoryphe Novak in Perer 1918; and one containing Eohomalonotus Reed 1918 and Calymenella Bergeron 1890. All genera are monophyletic, except Brongniartella, which is paraphyletic; as it was originally defined it gives rise to Trimerus and Platycoryphe. A modified Brooks Parsimony Analysis using the phylogentic hypothesis illuminates patterns of biogeography, in particu- lar, vicariance and geodispersal of homalonotids, during the late Ordovician. The analysis yields three major conclusions about homalonotid biogeography: homalonotids originated in Gondwana; Avalonia and Laurentia were close enough dur- ing the late Ordovician to exchange taxa, especially when sea level rose sufficiently; and long distance dispersal events occurred between Armorica and Florida, and also between Arabia and a joined Laurentia-Avalonia.

Cambrian–Ordovician trilobite family Missisquoiidae Hupé, 1955: Systematic revision and palaeogeographical considerations based on cladistic analysis

The missisquoiids are among the most important trilobites in the Cambrian–Ordovician boundary interval of Laurentia and Gondwana. This study deals with a systematic review of the family Missisquoiidae based on a cladistic analysis and explores their palaeobiogeographical history. A total of 22 missisquoiid species were selected for cladistic analysis. The cladistic results demonstrate that the family Missisquoiidae includes Parakoldinioidia, Pseudokoldinioidia, Tangshanaspis, and Tasmanocephalus; Lunacrania and Hardyia are included with reservation. The well-known genus Missisquoia is treated as a junior synonym of Parakoldinioidia. Based on the distribution of the missisquoiids, six palaeogeographical areas are recognised: Sino-Korea, Yangtze, Australia, southern Laurentia, northwestern Laurentia, and northeastern Laurentia. Palaeogeographical analyses show that the missisquoiids originated in Gondwana and continued to expand their geographical range within the continent and eventually expanded into the Laurentia. Optimisation results of geographical area transitions demonstrate that there were transitions between the two continents, and evolution of the Laurentian missisquoiids appears to have been strongly influenced by the Gondwanan counterparts. We suggest that dispersal of non-fossilised egg stage probably transported by oceanic currents may have been responsible for these inter-continental transitions.

Lower-Middle Cambrian boundary in open shelf facies of the Siberian Platform

In the Early and Middle Cambrian (of traditional usage), three broad facies belts were developed over the Siberian Platform. The lithofacies belts comprise evaporitic-carbonate, reef-shoal, and open-marine environments. Trilobites assemblages are most diverse in the open-marine lithofacies (Judoma-Olenek facies), represented especially by the Kuonamka Formation, in the eastern part of the platform. Species, genera and families of trilobites gradually increased through the Middle-Cambrian boundary interval in the Kuonamka Formation. Protolenidae dominated in the time represented by the Lermontovia Zone. In strata assigned to the Anabaraspis Zone, the protolenids disappear, the paradoxidids appear, and the diversity of dorypygids increases. The number of trilobite families increases in the Oryctocara and Kounamkites zones. Well represented in the Kuonamka formation of the eastern Siberian Platform are three levels of trilobites that have potential for global correlation. They are the Oryctocephalus reticulatus (= O. indicus latus), Oryctocephalus indicus, and Ovatoryctocara granulatus levels. The Lower-Middle Cambrian boundary in the South China correlates to the lower part of the Kounamkites Zone of the Siberian Platform.

HOLMIIDAE (TRILOBITA: OLENELLINA) OF THE MONTEZUMAN STAGE (EARLY CAMBRIAN) IN WESTERN NEVADA

Holmiids are a major component of the trilobite fauna in the middle part of the Montezuman Stage, the lowermost stage of the Cambrian of Laurentia with a continuous trilobite record. They are less common in the upper Montezuman where nevadiids predominate and other trilobite families appear. New material from western Nevada allows a revision of these holmiids. Palmettaspis parallela Fritz, 1995 and Palmettaspis cometes (Fritz, 1995) are assigned to a new genus, Montezumaspis, based primarily on thoracic characters, including a prominent axial spine on the thorax. A second new genus, Grandinasus, is based on Esmeraldina argenta (Walcott, 1910), in which the L3 lobe is incorporated in an expanded anterior lobe (LA) of the glabella. New species described are Esmeraldina elliptica, Grandinasus auricampus, G. patulus, Holmiella falx, and H. millerensis. The Laurentian taxa appear to be more primitive than the holmiids of Baltica by having simple, unfurrowed ocular lobes that are separated from the LA by an axial furrow. Three informal biofacies are suggested with a holmiid-dominated biofacies in a deep subtidal dysoxic environment, and two nevadiid-dominated biofacies in shallower subtidal environments.

SYSTEMATICS OF THE CAMBRIAN TRILOBITE FAMILY NEPEIDAE, WITH REVISION OF AUSTRALIAN SPECIES

Abstract: Taxonomy of the Cambrian trilobite family Nepeidae is revised. Morphometric analyses of the genera Nepea and Penarosa demonstrate that use of proportions of linear dimensions of the cranidium to differentiate species is invalid, and that infrageneric variation is continuous. The taxonomy and biostratigraphy of all Australian species of Nepeidae is revised. Species considered valid herein include: Nepea narinosa (type species), N. tonsillata, N. nans, Penarosa retifera (type species), P. elaticeps, P. rhinodelphis, P. netenta, Loxonepea loxophrys (type species) and Ferenepea hispida (type species). Folliceps is considered to be a junior subjective synonym of Nepea, Trinepea is regarded as a junior subjective synonym of Penarosa, and Ascionepea is considered to be a junior subjective synonym of Ferenepea.