Cladistic Analysis of Early–middle Cambrian Kochaspid Trilobites (Ptychopariida)

Sundberg, Frederick A.

doi:10.1666/0022-3360(2004)078<0920:caoeck>2.0.co;2

Cited by 18 publications

(52 citation statements)

References 29 publications

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“…the kochaspid clade] is also on the order of just a few tens of thousands to hundreds of thousands of years; and (3) there is &1 million years separating E. nodosa from its last common ancestor with Crassifimbra. Such estimates are consistent with available phylogenetic and stratigraphic data (Sundberg 2004;Webster 2011;unpublished data), and apply minimal insult to the fidelity of the trilobite fossil record.…”

Section: Appendixsupporting

confidence: 81%

“…Eokochaspis nodosa occurs in slightly younger sediments (basal bed of the Delamaran). Phylogenetic analysis places E. nodosa as a member of a kochaspid clade separated from the two species of Crassifimbra by nine internal nodes, although branch lengths were very short (Sundberg 2004;Webster 2011;unpublished data). A new species representing the oldest kochaspid (to be described elsewhere) occurs at very low abundance in collections with C.?…”

Section: Appendixmentioning

confidence: 99%

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Evolutionary Lability of Integration in Cambrian Ptychoparioid Trilobites

Webster

Zelditch

2011

Evol Biol

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Phenotypic integration can influence evolutionary rate and direction by channeling variation into few dimensions. The extent to which that channeling serves as a constraint over macroevolutionary timescales is determined in part by the evolutionary lability of phenotypic integration. Evolutionary change in patterns of pleiotropy, potentially reducing that constraint, is thought to be more readily achieved when pleiotropy is structured by variation arising in parallel along different developmental pathways rather than by variation arising from direct interactions within and between those pathways. Herein we test two predictions that follow from that hypothesis: (1) that clades undergoing dramatic diversification are characterized by integration that is weakly influenced by direct interactions; and (2) that the structure of integration arising from direct interactions is more conservative than that arising from parallel variation. We examine integration of the cranidium of two Cambrian ptychoparioid trilobites, Crassifimbra walcotti and Eokochaspis nodosa, comparing them to each other and to a previously studied species, C.? metalaspis. Shape variation is decomposed into components representing variation among individuals and variation due to direct interactions. In all three species, variation among individuals was only weakly influenced by direct interactions, suggesting that integration was unlikely to have been a long-term constraint on the Cambrian diversification of ptychoparioids. Phenotypic integration of E. nodosa is no more similar than expected by chance to either Crassifimbra species, but the component due to direct interactions is more similar than expected by chance to that of C.? metalaspis. Conversely, the two Crassifimbra species are generally similar (although not identical) in phenotypic integration, but markedly differ in their structure of direct interactions. Integration arising from direct interactions was therefore not immune to restructuring over even short evolutionary timescales, and was not always more conservative than that arising from parallel variation.

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Section: Appendixsupporting

confidence: 81%

Section: Appendixmentioning

confidence: 99%

Evolutionary Lability of Integration in Cambrian Ptychoparioid Trilobites

Webster

Zelditch

2011

Evol Biol

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“…Notoriously difficult ptychoparioid clades such as the Alokistocaridae or the Ptychopariidae are in urgent need of a rigorous approach to the analysis of morphological characters to unravel the relationships of taxa. Thus, even serious attempts to provide robust systematic groupings based on careful cladistics analyses (Sundberg, 1999(Sundberg, , 2004Esteve et al, 2012) must await a much more comprehensive database. Accordingly, we are unable to provide a confident placement for Elrathina and Elrathia at this time.…”

Section: Methodsmentioning

confidence: 99%

Middle Cambrian trilobites from the Ekspedition Bræ Formation of North Greenland, with a reappraisal of the genusElrathina

Geyer¹,

Peel²

2016

J. Paleontol.

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Abstract.-The richly fossiliferous Ekspedition Brae Formation of North Greenland yields a typical oligospecific fossil assemblage with well-preserved trilobites, helcionelloids, and lingulate brachiopods. The trilobites include Itagnostus subhastatus new species, Itagnostus sp. cf. I. gaspensis (Rasetti, 1948), Elrathina aphrodite new species, Elrathina athena new species, Elrathina hera new species, and Elrathia groenlandica new species-a fossil assemblage typical of the Bathyuriscus-Elrathina Zone as known from the Cordilleran regions of Laurentia. Excellent preservation allows a detailed assessment of the prosopon and elucidates aspects of the ontogenetic development of Elrathina and Elrathia. An evaluation of Elrathina includes a redescription of its type species, E. cordillerae (Rominger, 1887), based on the type material, and indicates that most specimens collected from the Burgess Shale and previously dealt with as E. cordillerae represent a new species.

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“…Only two Tonkinella species were included. Tonkinella gavrilovae Dalmatov, 1975 was included due to its basal position in the Tonkinella clade (Sundberg, 2006; also see Yeates, 1995;Predini, 2001;Sundberg 2004) and T. spinosa Sundberg, 2006 was included due to its spinose pygidium.…”

Section: Phylogenetic Analysismentioning

confidence: 99%

Phylogenetic Analysis of the Spiny Oryctocephalids (Trilobita, Corynexochida?, Oryctocephalidae), Cambrian

Sundberg¹

2014

J. Paleontol.

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

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Cladistic Analysis of Early–middle Cambrian Kochaspid Trilobites (Ptychopariida)

Cited by 18 publications

References 29 publications

Evolutionary Lability of Integration in Cambrian Ptychoparioid Trilobites

Evolutionary Lability of Integration in Cambrian Ptychoparioid Trilobites

Middle Cambrian trilobites from the Ekspedition Bræ Formation of North Greenland, with a reappraisal of the genusElrathina

Phylogenetic Analysis of the Spiny Oryctocephalids (Trilobita, Corynexochida?, Oryctocephalidae), Cambrian

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