Search results for "Stylophora"
showing 9 items of 9 documents
First report of the mitrate Peltocystis cornuta Thoral (Echinodermata, Stylophora) in the Lower Ordovician of central Anti-Atlas (Morocco)
2007
The mitrate Peltocystis cornuta is one the best known and most abundant stylophoran echinoderms in the Lower Ordovician (upper Tremadoc - lower Arenig) of Montagne Noire (southern France). It is here documented outside this region for the first time, in coeval deposits of central Anti-Atlas (Morocco). This report confirms the strong faunal affinities between Montagne Noire and Moroccan assemblages in the Ordovician. Twenty-eight individuals of P. cornuta are described from two distinct localities of the Zagora region. Their overall morphology is very comparable to that of Montagne Noire specimens. However, the Moroccan Peltocystis differ from the French ones in their smaller mean size, and …
Stephen J. Gould, les mitrates et les monstres
2003
Resume L'interet de l'analyse des cas teratologiques pour la comprehension des mecanismes du developpement ontogenetique est un theme recurrent dans l'œuvre litteraire de Gould. Cet article aborde le theme des monstres a travers deux problematiques ayant pour sujet des echinodermes paleozoiques atypiques: les stylophores mitrates. Le premier theme s'interesse au debat concernant la position phyletique des stylophores au sein des deuterostomes. Trois interpretations ont ete proposees pour leur appendice articule, dont l'une implique que les mitrates soient des « monstres prometteurs » (modele calcichorde). Une analogie avec differents scenarios proposes pour l'extinction des dinosaures demon…
Are homalozoans echinoderms? An answer from the extraxial-axial theory
2000
Homalozoans include four classes of non-pentamerous Paleozoic echinoderms: Homostelea (cinctans), Ctenocystoidea (ctenoid-bearing homalozoans), Homoiostelea (solutes), and Stylophora (cornutes and mitrates). Their atypical morphologies have historically made it difficult to relate them to other classes. Therefore, their systematic positions have been represented by two hypotheses (H): as stem taxa to echinoderms (H1) or as stem taxa to chordates (H2). These conclusions rest on previous inability to recognize synapomorphies with more crownward echinoderms, resulting in a forcing of the homalozoans down the phylogenetic tree that is more artifactual than evolutionary. The Extraxial-Axial Theo…
Exceptionally preserved soft parts in fossils from the Lower Ordovician of Morocco clarify stylophoran affinities within basal deuterostomes.
2019
10 pages; International audience; The extinct echinoderm clade Stylophora consists of some of the strangest known deuterostomes. Stylophorans are known from complete, fully articulated skeletal remains from the middle Cambrian to the Pennsylvanian, but remain difficult to interpret. Their bizarre morphology, with a single appendage extending from a main body, has spawned vigorous debate over the phylogenetic significance of stylophorans, which were long considered modified but bona fide echinoderms with a feeding appendage. More recent interpretation of this appendage as a posterior “tail-like” structure has literally turned the animal back to front, leading to consideration of stylophorans…
Morphometric analysis of Tremadocian (earliest Ordovician) kirkocystid mitrates (Echinodermata, Stylophora) from the Taebaeksan Basin, Korea
2004
Abstract Abundant isolated remains of stylophoran echinoderms (cornutes and mitrates) are reported for the first time in the late Tremadocian (Asaphellus Zone) Tumugol Formation of Korea. Mitrate remains include numerous adorals of Kirkocystidae. Several new important anatomical features have been observed on these adorals, as an internal calcitic layer that is associated to s2 and possibly also to the palmar complex. This observation suggests that the palmar complex would be present not only in mitrocystitid mitrates, but also in peltocystitids. For the first time, several morphometric analyses have been undertaken based on isolated kirkocystid adorals, so as to explore the morphological d…
Biomineralization toolkit: the importance of sample cleaning prior to the characterization of biomineral proteomes.
2013
In an interesting work published recently in PNAS, Drake et al. (1) presented a proteomic study of the skeleton from the stony coral Stylophora pistillata . This study identified proteins that are associated to the mineral phase (i.e., that potentially contribute to shape the skeleton). In other words, this set of proteins is supposed to represent the so-called “biomineralization toolkit.” Although some of the 36 proteins reported in Drake et al. (1) appear as genuine extracellular matrix (ECM) proteins related to biomineralization, such as coral acid-rich proteins or carbonic anhydrase, some others are obvious intracellular contaminants that should not be considered as skeletal organic mat…
LATEST CAMBRIAN CORNUTES (ECHINODERMATA: STYLOPHORA) FROM THE TAEBAEKSAN BASIN, KOREA
2005
The oldest echinoderms and first cornute stylophorans ever reported from Korea are described, based on more than 40 specimens collected from the Late Cambrian of the Taebaeksan Basin. New material doubles the number of stylophorans described from Asia and the number of specimens of Late Cambrian stylophorans recorded throughout the world. Three different cornutes are identified: Sokkaejaecystis serrata n. gen. and sp. and two genus and species indeterminate forms A and B. Sokkaejaecystis serrata and indeterminate form B are assigned to the Chauvelicystinae, while the systematic position of indeterminate form A within cornutes is difficult to assess. This new material suggests paleobiogeogra…
Early Palaeozoic palaeobiogeography and palaeoecology of stylophoran echinoderms
2007
44 pages; International audience; Stylophorans (cornutes, mitrates) represent one of the most diverse classes of Cambro-Ordovician echinoderms. They were freeliving, benthic, non-radiate forms, closely related to asterozoans and crinoids. Taphonomic, sedimentological, and palaeosynecological data provide useful information on key aspects of stylophoran palaeoecology. Such a combined approach suggests that the rarity of stylophorans in proximal environments (above storm-wave base) was probably original and does not exclusively result from the possession of a loosely articulated polyplated calcitic test. Conversely, stylophorans were relatively abundant in deeper settings (below storm-wave ba…
New Ordovician mitrates (Echinodermata, Stylophora) from the Ancenis Basin (South Armorican Domain, France): Palaeogeographic and palaeoenvironmental…
2006
8 pages; International audience; Fossil echinoderms are extremely rare in Ordovician deposits of the South Armorican Domain (SAD), a structurally complex area stacked to the Medio-North Armorican Domain during the Hercynian orogeny. Two new occurrences of mitrate stylophorans are documented in the eastern part of the SAD (Ancenis Basin). The youngest known specimen of Lagynocystis pyramidalis is described from the Schistes du Fresne Formation (Late Ordovician). Mitrocystites mitra is reported from the Pierre Meliere Formation (Middle Ordovician), and for the first time, outside of Bohemia. The presence of these two cool-adapted taxa (both abundant in the Prague Basin) in the Ancenis Basin d…