Are protochordates chordates?

Raineri, Margherita

doi:10.1111/j.1095-8312.2006.00620.x

Cited by 4 publications

(7 citation statements)

References 2 publications

(1 reference statement)

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“…In eff ect, the dorsal and ventral wings of the W-shaped muscle block provide a separately controllable musculature for the compressed dorsal and ventral body margins and for the median fi ns, where present. Th e V-shaped pattern could be interpreted as another indication of a convergent evolution of free-moving animals compared to craniates (Raineri 2006).…”

Section: Folding Of the Muscular Somitesmentioning

confidence: 99%

“…Raineri (2006), however, recently refuted the chordate affi nities of the protochordates based on the development of their notochord and central nervous system on the ventral rather than dorsal side (indicating that they are gastroneuralians, bilateralia with ventral neural cord), the muscular structure of their notochord, and lack of attachment of the axial musculature to the notochord. Th is is not a new idea (Arendt & Nübler-Jung 1994;Bergström 1996Bergström , 1997Bergström et al 1998) for the problem was already discussed in the 19th century.…”

Section: Chordate Craniate Vertebrate Charactersmentioning

confidence: 99%

“…It might also have impeded cephalization in branchi- Turner S. et al ostomatoids (and also in Palaeo branchio stoma), and in any cephalochordates possessing this adaptation, but not in Early Cambrian Yunnanozoon. Raineri (2006), however, has countered homology of the notochord in Branchio stoma and craniates.…”

Section: Anterior End Of Notochordmentioning

confidence: 99%

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False teeth: conodont-vertebrate phylogenetic relationships revisited

et al. 2010

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MOTS CLÉSChordata, Craniata, animal-conodonte, codage des caractères, analyse cladistique, paléohistologie. KEY WORDSChordata, Craniata, conodont animals/ elements, character coding, cladistic analysis, palaeo-histology. ABSTRACTAn evidence-based reassessment of the phylogenetic relationships of conodonts shows that they are not "stem" gnathostomes, nor vertebrates, and not even craniates. A signifi cant group of conodont workers have proposed or accepted a craniate designation for the conodont animal, an interpretation that is increasingly becoming established as accepted "fact". Against this prevailing trend, our conclusion is based on a revised analysis of traditional morphological features of both discrete conodont elements and apparatuses, histological investigation and a revised cladistic analysis modifying that used in the keystone publication promoted as proof of the hypothesis that conodonts are vertebrates. Our study suggests that conodonts possibly were not even chordates but demonstration of this is beyond the scope of this paper. To summarize, in conodonts there is low cephalization; presence of simple V-shaped trunk musculature and unique large-crystal albid material in the elements; lack of a dermal skeleton including characteristic vertebrate hard tissues of bone, dentine and enamel; lack of odontodes with bone of attachment and a unique pulp system; lack of segmentally-arranged paraxial elements and dermal elements in median fi ns, all of which supports neither a vertebrate nor a craniate relationship for conodonts. RÉSUMÉ Des pseudo-dents : une réévaluation des relations phylogénétiques des conodontes et des vertébrés.Une réévaluation des relations phylogénétiques des conodontes est fondée sur de nouvelles preuves. Elle montre que les conodontes ne sont ni des gnathostomes-souches, ni des vertébrés, ni même des crâniates. Un groupe signifi catif de spécialistes des conodontes a proposé, ou accepté, que ces organismes soient considérés comme des crâniates, une interprétation qui est en train de s'installer en tant que fait avéré. Notre conclusion va à l'encontre de cette tendance ; elle est fondée sur une révision des traits morphologiques traditionnels à la fois des éléments isolés et des assemblages de conodontes, sur les données histologiques et sur une analyse cladistique révisée, ce qui modifi e les conclusions de la publication principale qui a promu l'hypothèse selon laquelle les conodontes seraient des vertébrés. Notre étude suggère même que les conodontes n'aient pas été des chordés, mais la démonstration de cette hypothèse va au-delà de l'objectif de cet article. En résumé, chez les conodontes, le degré de céphalisation est faible ; la musculature du tronc a une forme simple en V ; les éléments isolés montrent un tissu blanc avec des cristaux de grande taille, uniques pour ce tissu ; il n'y a pas de squelette dermique incluant les tissus durs caractéristiques des vertébrés tels que l'os, la dentine et l'émail ; il n'y a pas d'odontodes avec leur os et leur système pulpaire unique ; il ...

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Section: Folding Of the Muscular Somitesmentioning

confidence: 99%

Section: Chordate Craniate Vertebrate Charactersmentioning

confidence: 99%

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False teeth: conodont-vertebrate phylogenetic relationships revisited

et al. 2010

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“…However, a comparative analysis of the positions and gene expression patterns of the prospective territories in deuterostomes and gastroneuralians that was not limited to the fate maps, but that included the stages of gastrulation and neurulation, has produced a quite different picture (Raineri 1998(Raineri , 2006. When the prospective maps are oriented with reference to the axis of the egg and the future body axes, protochordates appear to be different from vertebrates, but similar to gastroneuralians.…”

Section: An Alternative View On the Phylogeny Of Protochordates And Tmentioning

confidence: 99%

“…6.5). For instance, taking into account the role of mesodermal signalling in neural induction and the peculiar ability of dorsal ectoderm to undergo invagination/expansion depending presumably on its position, the evolution of a nervous system like that of vertebrates could have been expected from a type of development shifting mesoderm towards the dorsal side (Raineri 2006). This predictability, and the underlying logic, is linked to the origin of homology, which is to be sought in similar combinations of modules, not necessarily in similar forms.…”

Section: An Alternative View On the Phylogeny Of Protochordates And Tmentioning

confidence: 99%

Old and New Concepts in EvoDevo

Raineri

2008

Evolutionary Biology From Concept to Application

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The concept of the modular organization of the organism is central to both classical experimental embryology and modern evolutionary developmental biology (EvoDevo). The latter discipline often ascribes homology, or the diversity of forms arising from the same module or combination of modules, to gene mutations or changes of gene regulation. This gene-centred atomistic view does not yield reliable criteria for homology, nor can it account convincingly for phenomena such as convergence and cooption. To understand the logic behind this plasticity, attention should be shifted from variation of existing characters to the preconditions for homology. This could be done by identifying the basic modules and their molecular regulation within the context of the most general, shared embryonic morphology. Mapping divergent embryonic trajectories onto different fates of these modules may allow us to throw light on the constrained sets of different, but related morphologies which can arise from different combinations of modules.

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