Monophyly of brachiopods and phoronids: reconciliation of molecular evidence with Linnaean classification (the subphylum Phoroniformea nov.)

Molecular phylogenetic analyses of aligned 18S rDNA gene sequences from articulate and inarticulate brachiopods representing all major extant lineages, an enhanced set of phoronids and several unrelated protostome taxa, confirm previous indications that in such data, brachiopod and phoronids form a well-supported clade that (on previous evidence) is unambiguously affiliated with protostomes rather than deuterostomes. Within the brachiopod-phoronid clade, an association between phoronids and inarticulate brachiopods is moderately well supported, whilst a close relationship between phoronids and craniid inarticulates is weakly indicated. Brachiopod-phoronid monophyly is reconciled with the most recent Linnaean classification of brachiopods by abolition of the phylum Phoronida and rediagnosis of the phylum Brachiopoda to include tubiculous, shell-less forms. Recognition that brachiopods and phoronids are close genealogical allies of protostome phyla such as molluscs and annelids, but are much more distantly related to deuterostome phyla such as echinoderms and chordates, implies either (or both) that the morphology and ontogeny of blastopore, mesoderm and coelom formation have been widely misreported or misinterpreted, or that these characters have been subject to extensive homoplasy. This inference, if true, undermines virtually all morphology-based reconstructions of phylogeny made during the past century or more

Schmidtites celatus (Obolida, Brachiopoda) from the "Obolus sands" (Upper Cambrian - Lower Ordovician) of Estonia

International audienceLarge collections of the brachiopod obolid Schmidtites celatus have been gathered from Upper Cambrian-Lower Ordovician strata in four northern Estonian localities. The morphological features and the taxonomic characters of the genus and of the single species representing it are re-described and illustrated. New diagnoses are proposed based on characters of the shell and morphological traits that permit Schmidtites celatus to be compared with and distinguished from the other obolid genera occurring in the same samples or areas, i.e. Ungula ingrica, Oepikites, and Obolus apollinis which now includes specimens formerly described as Ungula convexa. Schmidtites celatus differs from them mainly in the arrangement of its musculature

Tools for linguloid taxonomy: the genus Obolus (Brachiopoda) as an example

International audienceThis study points out some basic problems of linguloid systematics and proposes solutions for them. A taxonomic examination of the unique species of the genus Obolus found in the Upper Cambrian of Estonia and Russia, O. apollinis (= O. ruchini, O. transversus, O. rebrovi and Ungula convexa) is used as an example of a methodology employing all of the characters valid for distinguishing species of both extant and fossil Lingulidae. These characters are: - umbonal region; - body musculature; - septa or ridges; - main mantle canals - as established and figured by EMIG (1982, 1983) and BIERNAT and EMIG (1993). All of them have been determined to be taxonomically stable and have been studied and compared to take into account intraspecific variability; they should be used to describe or to redescribe any taxon of the superfamily Linguloidea. Characters of the shell and valves, such as shape, size, and dimensional ratios have no taxonomic value. ––– Des outils pour la taxinomie des Lingulidoida : le genre Obolus (Brachiopoda) pris comme exemple.- Cette étude met en exergue des problèmes fondamentaux de la systématique des Linguloïdes et propose des solutions méthodologiques basées sur les caractères utilisés pour identifier les espèces de Lingulides actuelles et fossiles. L'unique espèce du genre Obolus, O. apollinis (= O. ruchini, O. transversus, O. rebrovi and Ungula convexa), récoltée dans divers gisements du Cambrien moyen et supérieur en Estonie et Russie, sert ici d'exemple. Les caractères sont : - la région umbonale ; - la musculature du corps ; - les septums et crêtes internes ; - les canaux du manteau ; selon la description et la représentation faites par EMIG (1982, 1983) et BIERNAT et EMIG (1993). Tous ces caractères se sont révélés taxinomiquement stables tout en présentant une relative variabilité intraspécifique ; ils sont donc à être utilisés pour décrire ou redécrire tous les taxons de la superfamille des Linguloidea. Il convient de souligner que les caractères de la coquille ou des valves, tels que formes, tailles, rapports dimensionnels n'ont aucune valeur taxinomique

Proof that Lingula (Brachiopoda) is not a living-fossil, and emended diagnoses of the Family Lingulidae

International audienceLingula is often considered a "living-fossil" based on its supposed lengthy morphological conservatism owing to its absence of evolution, and its remarkable survival for more than 550 M.Y. This conclusion is based on the typical apparently unchanged "linguliform" shape of the shell. However the taxa of the family Lingulidae show morphological evolutionary changes despite the fact that the group appears panchronic among the Recent Brachiopoda. Consequently, traditional opinion that Lingula is a "living-fossil" should be rejected. Diagnoses of the Family Lingulidae and of its three genera are herewith emended. Résumé : Preuves que Lingula (Brachiopoda) n'est pas un fossile vivant, avec de nouvelles diagnoses pour les taxons de la Famille des Lingulidae. ––– Lingula est souvent considérée comme un fossile-vivant, voire le plus ancien actuellement connu, à cause de son long conservatisme morphologique basé sur une supposée absence d'évolution, ainsi qu'en raison de sa remarquable survie depuis plus de 550 MA. Cette assertion est basée sur une forme inchangée de la coquille, dite "linguliforme". Cependant, les taxons de la famille des Lingulidae montrent des changements évolutifs de la morphologie et de l'anatomie interne bien que ce groupe puisse être considéré comme panchronique au sein des Brachiopoda actuels. Il est démontré que l'opinion traditionnellement véhiculée selon laquelle les Lingula seraient des fossiles vivants doit être rejetée. En conséquence, de nouvelles diagnoses sont proposées pour la famille des Lingulidae et pour les trois genres pouvant s'y rapporter avec certitude

De l'origine historique des noms lingule, Lingula, anatina, et de la confusion des formes chez les Brachiopodes

Les premiers auteurs à publier sur les lingules – Lingula - furent français : BRUGUIÈRE créa le genre Lingula en 1791 [et non en 1797], cette date acceptée par tous les auteurs jusqu'à la fin du XIXème siècle et confirmée dans ce travail. Elle fut remise en cause à partir du début du XXème siècle et remplacée officiellement par 1797 par la Commission Internationale de Nomenclature zoologique en 1982, puis confirmée en 1985. La signification de lingule ou lingula (ou ligula) est communément considérée comme un diminutif (signifiant languette ou élément en forme de langue) du latin lingua "langue". D'autres possibilités peuvent être suggérées, comme un diminutif savant du latin lingua + le suffixe –ula [en français –ule] ou encore une autre traduction du latin ligula ou lingula à savoir cuillère. LAMARCK (1801) puis CUVIER (1802) décrivirent la première espèce du genre sous Lingula anatina. L'origine du nom d'espèce est inconnue, mais, en latin, ce nom évoque une ressemblance avec le "bec de cane" cité par CUVIER (1798). Auparavant SEBA (1758) indiquait qu'il s'agit "d'une espèce particulière de conque anatifère", anatina signifiant en latin du canard ou appartenant au canard. J. SOWERBY (1812) se basa sur la ressemblance de forme de la coquille pour décrire les premières lingules fossiles dans le Jurassique de Grande-Bretagne. À partir des années 1840, notamment avec la description des "Lingula-flags" dans le Paléozoïque inférieur du Pays de Galles, il y a amalgame, devenu classique, de la forme – linguliforme – entre les espèces actuelles de Lingula et les lingulides fossiles paléozoïques et mésozoïques. L'extension géologique des Lingula à travers tout le Phanérozoïque a influencé DARWIN (1859) lors de la création du terme "fossile vivant". Dans son livre "Sur l'origine des espèces", il fait plusieurs fois référence aux lingules. Depuis cette époque, les Lingula ont été décrites, dans la plupart des traités de paléontologie, "avec une forme pratiquement inchangée depuis leur origine au Cambrien, il y a environ 550 Millions d'années". La conséquence en est que tout brachiopode fossile linguliforme a été décrit, et l'est parfois encore de nos jours, comme appartenant au genre Lingula sur ce seul critère. Pourtant, le traditionnel concept introduit par DARWIN que les Lingula sont des "fossiles vivants" a été rejeté depuis plus de 20 ans, et auparavant par CUVIER (1798). La persistance de cette hérésie scientifique ne peut s'expliquer que par le conservatisme de la communauté internationale des paléontologues avec des modèles difficilement remis en question..The first descriptions of Lingula were made from then extant specimens by three famous French scientists: BRUGUIÈRE, CUVIER, and LAMARCK. The genus Lingula was created in 1791 (not 1797) by BRUGUIÈRE and in 1801 LAMARCK named the first species L. anatina, which was then studied by CUVIER (1802). In 1812 the first fossil lingulids were discovered in the Mesozoic and Palaeozoic strata of the U.K. and were referred to Lingula on the basis of similarity in the form of the shell. In the 1840's other linguliform brachiopods from the Palaeozoic were described. The similarity of the shell form of the extant Lingula and these fossils led DARWIN in 1859 to create the description "living fossil" in his book "On the Origin of Species". Thereafter, this Darwinian concept became traditional in that Lingula was considered to lack morphological evolutionary changes. Although denounced as scientifically incorrect for more than two decades, the concept still remains in many books, publications and Web sites, perhaps a witness to palaeontological conservatism

Molecular phylogeny of brachiopods and phoronids based on nuclear-encoded small subunit ribosomal RNA gene sequences

Brachiopod and phoronid phylogeny is inferred from SSU rDNA sequences of 28 articulate and nine inarticulate brachiopods, three phoronids, two ectoprocts and various outgroups, using gene trees reconstructed by weighted parsimony, distance and maximum likelihood methods. Of these sequences, 33 from brachiopods, two from phoronids and one each from an ectoproct and a priapulan are newly determined. The brachiopod sequences belong to 31 different genera and thus survey about 10% of extant genus-level diversity. Sequences determined in different laboratories and those from closely related taxa agree well, but evidence is presented suggesting that one published phoronid sequence (GenBank accession UO12648) is a brachiopod-phoronid chimaera, and this sequence is excluded from the analyses. The chiton, Acanthopleura, is identified as the phenetically proximal outgroup; other selected outgroups were chosen to allow comparison with recent, non-molecular analyses of brachiopod phylogeny. The different outgroups and methods of phylogenetic reconstruction lead to similar results, with differences mainly in the resolution of weakly supported ancient and recent nodes, including the divergence of inarticulate brachiopod sub-phyla, the position of the rhynchonellids in relation to long- and short-looped articulate brachiopod clades and the relationships of some articulate brachiopod genera and species. Attention is drawn to the problem presented by nodes that are strongly supported by non-molecular evidence but receive only low bootstrap resampling support. Overall, the gene trees agree with morphology-based brachiopod taxonomy, but novel relationships are tentatively suggested for thecideidine and megathyrid brachiopods. Articulate brachiopods are found to be monophyletic in all reconstructions, but monophyly of inarticulate brachiopods and the possible inclusion of phoronids in the inarticulate brachiopod clade are less strongly established. Phoronids are clearly excluded from a sister-group relationship with articulate brachiopods, this proposed relationship being due to the rejected, chimaeric sequence (GenBank UO12648). Lineage relative rate tests show no heterogeneity of evolutionary rate among articulate brachiopod sequences, but indicate that inarticulate brachiopod plus phoronid sequences evolve somewhat more slowly. Both brachiopods and phoronids evolve slowly by comparison with other invertebrates. A number of palaeontologically dated times of earliest appearance are used to make upper and lower estimates of the global rate of brachiopod SSU rDNA evolution, and these estimates are used to infer the likely divergence times of other nodes in the gene tree. There is reasonable agreement between most inferred molecular and palaeontological ages. The estimated rates of SSU rDNA sequence evolution suggest that the last common ancestor of brachiopods, chitons and other protostome invertebrates (Lophotrochozoa and Ecdysozoa) lived deep in Precambrian time. Results of this first DNA-based, taxonomically representative analysis of brachiopod phylogeny are in broad agreement with current morphology-based classification and systematics and are largely consistent with the hypothesis that brachiopod shell ontogeny and morphology are a good guide to phylogeny

Relation between directed polymers in random media and random bond dimer models

We reassess the relation between classical lattice dimer models and the continuum elastic description of a lattice of fluctuating polymers. In the absence of randomness we determine the density and line tension of the polymers in terms of the bond weights of hard-core dimers on the square and the hexagonal lattice. For the latter, we demonstrate the equivalence of the canonical ensemble for the dimer model and the grand-canonical description for polymers by performing explicitly the continuum limit. Using this equivalence for the random bond dimer model on a square lattice, we resolve a previously observed discrepancy between numerical results for the random dimer model and a replica approach for polymers in random media. Further potential applications of the equivalence are briefly discussed.Comment: 6 pages, 3 figure

Comment on ``Roughening Transition of Interfaces in Disordered Media''

Emig and Nattermann (Phys. Rev. Lett. 81, 1469 (1998)) have recently investigated the competition between lattice pinning and impurity pinning using a Renormalisation Group (RG) approach. For elastic objects of internal dimensions $2 < D < 4$, they find, at zero temperature, an interesting second order phase transition between a flat phase for small disorder and a rough phase for large disorder. These results contrast with those obtained using the replica variational approach for the same problem, where a first order transition between flat and rough phases was predicted. In this comment, we show that these results can be reconciled by analysing the RG flow for an arbitrary dimension $N$ for the displacement field.Comment: Submitted to Phys. Rev. Let

Novocrania turbinata synonym of N. anomala

Anomia turbinata, ou Anomie conique, (= Novocrania turbinata) a été décrite par Poli (1795) dans le Bathyal des côtes du Royaume des Deux-Siciles, avec comme synonyme Patella anomala Müller, 1776 (= N. anomala). Longtemps considérée comme la forme méditerranéenne de N. anomala, son histoire est brièvement décrite. Récemment, N. turbinata a été considérée par plusieurs auteurs, comme une espèce valide, mais sur quelques caractères ne correspondant pas à ceux de la description originelle ; ils apparaissent comme des variations des caractères de N. anomala. La présence conjointe des deux "espèces" dans plusieurs localités surtout sur le plateau continental tend à accréditer leur synonymie. Celle-ci a été récemment corroborée par des analyses moléculaires et est discutée en prenant aussi en compte les caractéristiques des bassins méditerranéens et leur histoire depuis le Miocène.Anomia turbinata, or conical Anomia (= Novocrania turbinata), was described by Poli (1795) in the bathyal environment off the coast of the Kingdom of the Two Sicilies, Patella anomala Müller, 1776 (= N. anomala) being considered a synonym. The history of this species, commonly considered as the Mediterranean form of N. anomala, will be described. Recently, several authors have described N. turbinata as a valid species on the basis of shell variations, as compared to N. anomala. After analysis of the taxonomic validity of these characters, both species are considered as synonymous. That is supported by their occurrence in various localities, mainly in the continental shelf. Their synonymy has been corroborated by molecular analyses and is discussed with reference to the characteristics of the Mediterranean basins and their history since the Miocene

Reply to L.E. POPOV and L.E. HOLMER (CG2003_A06_LEP-LEH): Obolid taxonomy

International audienceReply to L.E. POPOV and L.E. HOLMER (2003): Obolid taxonom