Search results for "Homalozoa"
showing 3 items of 3 documents
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…
A critical comment on ‘ankyroids’ (Echinodermata, Stylophora)
2001
Abstract A recent cladistic analysis of stylophoran echinoderms performed by Parsley suggested that mitrates are polyphyletic and derived from symmetrical cornutes. Parsley erected the order Ankyroida to include all derived cornutes and mitrates. The present paper addresses several significant problems in the data matrix of Parsley's cladistic analysis. Detailed morphological comparisons of various stylophorans suggest that important homologies have been ignored: cornute zygal crest and mitrate septum, adorals, glossal and digital. Subanals are not homologous in mitrates. Identification of plate homologies shows that similar-looking symmetrical thecal outlines have been acquired independent…
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…