Les Echinodermes Cincta du Cambriende la Montagne Noire (France)

Termier, Henri; Termier, Geneviève

doi:10.1016/s0016-6995(73)80019-1

Cited by 16 publications

(14 citation statements)

References 3 publications

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“…The presence of a single left marginal groove that reaches M1l is a trait shared with some species of Sucocystis Cabibel, Termier & Termier, 1959; however, Protocinctus gen. nov. differs from these forms in other respects (the shape and height of the theca, the number of marginal plates, and the development of ventral swellings). The elongate thecal shape of Protocinctus gen. nov. is similar to that of Gyrocystis Jaekel, 1918, Progyrocystis Friedrich, 1993, or Elliptocinctus Termier & Termier, 1973. The arrangement of three plates in the lintel is similar to Gyrocystis , Sucocystis , and Elliptocinctus , and the absence of prominent ventral swellings is a feature shared with Trochocystoides parvus Jaekel, 1918, T. planus , S. ubaghsi , A. jaekeli , and Gyrocystis platessa Jaekel, 1918.…”

mentioning

confidence: 61%

The oldest cinctan carpoid (stem-group Echinodermata), and the evolution of the water vascular system

Rahman

Zamora

2009

Zoological Journal of the Linnean Society

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A new cinctan (Protocinctus mansillaensis gen. et sp. nov.), from the early Middle Cambrian of the Iberian Chains (north-east Spain), is described with the aid of X-ray microtomography and three-dimensional computer models. Investigation in this manner was possible because of the unusual condition of the fossils, which are preserved as recrystallized calcite. Protocinctus gen nov. possesses an elongate body with a single left anterior feeding groove and an open posterior marginal frame (in ventral view): this combination of characters is unique amongst cinctans. Through the study of original specimens and 'virtual fossils' it was possible to reconstruct the palaeobiology of Protocinctus gen. nov.: cinctans are interpreted as pharyngeal basket feeders with a U-shaped gut, using their posterior appendage to aid stability on the sediment surface. Cinctans are critical to understanding the evolutionary history of the echinoderm stem group, as they illustrate the transition from a paired water vascular system (basal) to one constructed from just the left hydrocoel (derived). The former condition is also observed in another group of stem-group echinoderms, the ctenocystoids, and is hypothesized for the latest common ancestor of the echinoderms and hemichordates.

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mentioning

confidence: 61%

The oldest cinctan carpoid (stem-group Echinodermata), and the evolution of the water vascular system

Rahman

Zamora

2009

Zoological Journal of the Linnean Society

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“…Several other genera described by Cabibel et 01. (1958) and Termier and Termier (1973) appear to be synonyms. Homosteleans were apparently slow-moving, benthic detritus or suspension feeders.…”

Section: Class Homostelea (Three Genera)mentioning

confidence: 95%

Radiation of Echinodermata

Sprinkle

1992

Topics in Geobiology

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“…Cinctans are confined to only a brief interval of time during the Middle Cambrian and were a component of benthic marine assemblages in Western Gondwana, Siberia and Avalonia (Barrande 1887; Termier and Termier 1973; Schröder 1973;Friedrich 1993, 1995; Sdzuy 1993; Fatka and Kordule 2001; Rozhnov 2006; Zamora and Smith 2008). Isolated plates of cinctans are very common in Middle Cambrian rocks but complete skeletons are preserved only under special conditions in specific echinoderm Lagerstätten.…”

Section: The Competing Classifications Proposed By Friedrich (1993) mentioning

confidence: 99%

Rooting Phylogenies of Problematic Fossil Taxa; A Case Study Using Cinctans (Stem‐group Echinoderms)

Smith

Zamora

2009

Palaeontology

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Extinct clades whose higher-level relationships are problematic or disputed pose a particular problem for phylogenetic analysis because of the difficulty of establishing a convincing root. Cinctans are a problematic group of primitive preradiate echinoderms whose morphology is so distinct that few characters can be usefully homologized with any other group. Here we use a two stage approach, first constructing an unrooted network using the totality of phylogenetically informative characters in which individual plates are homologized, and then determining the root position with a much smaller set of recast characters that can be polarized by outgroup and ⁄ or ontogenetic criteria. Furthermore, when rooting is based on stratigraphic criteria the same two major derived clades are identified, although basal relationships are somewhat different. We contend that the congruence of results obtained using our various approaches provides confidence that we have correctly rooted the cladogram. A revised taxonomy for Cincta is presented.Key words: Stem group, echinoderms, cladistics, rooting, phylogenetic analysis, Cambrian, new taxa.C ladistic analysis is a powerful means of determining relationships amongst taxa. Parsimony programs such as PAUP* (Swofford 2002) are very efficient at finding the shortest network connecting taxa on the basis of their observed traits, be they morphological or molecular. The most parsimonious network minimizes the number of character state changes across the entire topology and tells us about overall similarity of the taxa included. When character state changes are optimized over this network it is possible to differentiate homologous states from those that are homoplasious (i.e. those apparently identical states which arise in two or more parts of the network independently). However, networks are not very useful for biological sciences where we are often interested in the direction in which character state changes have occurred over time. To establish the polarity of traits and thus distinguish the primitive condition from the derived condition, the root of the cladogram needs to be identified. Furthermore, rooting a cladogram is the only way to distinguish between monophyletic and paraphyletic groups and thus establish the necessary framework for classification.There are two widely accepted methods of rooting plus two additional ad hoc rules of thumb (Weston 1994). The most widely used method is outgroup polarization (e.g. Maddison et al. 1984; Nixon and Carpenter 1993), whereby one or more closely related taxa that lie outside the group of interest are used to establish which character state is more general in its distribution and which more restricted. The assumption here is that character states shown by just some ingroup taxa, but not found within the wider ensemble, are derived. The more ingroup characters that can be polarized the more likely it is that the root position will be estimated accurately. Consequently, the outgroup method works best where a closely related taxon ...

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Les Echinodermes Cincta du Cambriende la Montagne Noire (France)

Cited by 16 publications

References 3 publications

The oldest cinctan carpoid (stem-group Echinodermata), and the evolution of the water vascular system

The oldest cinctan carpoid (stem-group Echinodermata), and the evolution of the water vascular system

Radiation of Echinodermata

Rooting Phylogenies of Problematic Fossil Taxa; A Case Study Using Cinctans (Stem‐group Echinoderms)

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