Publisher Summary This chapter discusses brachiopod evolution. Brachiopods are one of the few groups of living metazoans to be represented by distinctive and complex skeletal remains more or less continuously throughout the Phanerozoic record. The geological history of brachiopods, as measured by generic diversity and commonness of occurrence, is also revealing. A complete anatomy can never be reconstructed from skeletal impressions alone. There are basic differences in soft parts such as the loss of the anus or the rearrangement of filaments into pairs during lophophore growth that marks significant changes in phyletic history. The juvenile lophophore supports that grew into the complex lobate structures of adult Praelacazella and Thecidiopsis from the Cretaceous are identical to adult supports of Jurassic Thecidella and Rioultina , respectively. In the Lacazella group, only a few secondary fibres survive on the teeth of living species, and no fibres have been found in the late Cretaceous Eolucazella , which may indicate accelerated neoteny in an aberrant stock.

Chapter 4 Brachiopod Evolution

Holorhynchus giganteus Kiaer, 1902, a common Late Ordovician (mid-Ashgill) pentameride brachiopod in the Baltic region, Kazakhstan, and southern Tien Shan, is documented for the first time from the Badanjilin Formation (mid-Ashgill) of western Inner Mongolia (Alxa block), North China. Serial sections of the Chinese material confirm the presence of a vestigial ventral median septum in the early growth stage of H. giganteus, but the septum becomes embedded in the secondary shell thickening at the adult growth stage. A survey of the type material from Norway and additional material from other regions indicates that the incipient ventral median septum is a much more commonly developed structure than was previously believed. The presence of a well-developed pseudodeltidium in the Tien Shan material of H. giganteus and the absence of such a structure in conspecific material from many other regions require a systematic revision of the generic group. Holorhynchus has rodlike crura (=brachial processes) t...

The late ordovician and early silurian pentameride brachiopod holorhynchus kiaer, 1902 from north china

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESICN: The trilobite Phacops rana Green. Library of Congress Cataloging in Publication Data Doescher, Rex A Living and fossil brachiopod genera 1775-1979. (Smithsonian contributions to paleobiology ; no. 42) Bibliography: p. 1. Brachiopoda. 2. Brachiopoda, Fossil. 3. Brachiopoda—Bibliography. 4. Brachiopoda, Fossil — Bibliography. I. Title. II. Series: Smithsonian Institution. Smithsonian contributions to paleobiology ; no. 42. QE701.S56no. 42 [QL395] 560s [594'.8] 80-607773 rev

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Living and fossil brachiopod genera, 1775-1979 : lists and bibliography

Silurian pentameracean brachiopods of the Fossil Hill Formation, Ontario

Silurian and basal Devonian strata can be followed throughout the study area. In the western part the following formations are recognized, in ascending order: Sources (new name) lithographic limestone (which is similar to the White Head Formation), Val Brillant orthoquartzite, Sayabec limestone, St. Leon siltstone (including the Lefrancois Member [new name] which forms a reef complex), and Cap Bon Ami Formation. This sequence is very similar in age and lithology to the one in the Matapedia Valley area. In the eastern part of the area the succession is: Griffon Cove River Formation composed predominantly of heterogeneous terrigenous strata, Sayabec limestone, Roncelles very calcareous mudstone, St. Leon siltstone, and Cap Bon Ami Formation. The Sayabec limestone forms a co venient datum, and both it and the St. Leon Formation are continuous throughout the area. The Roncelles Formation interfingers with the lower half of the St. Leon Formation in the central part of the area. The following formations are dated with fossils: in the west, Sources (late Llandoverian) and basal St. Leon (early Ludlovian); in the east, Griffon Cove River (Pridolian), Sayabec (Pridolian and Gedinnian), and Roncelles (two separate faunas of early and late Gedinnian). A major transgression from the western to the eastern part of the area occurred in Pridolian time. The following formations are time transgressive, and are youngest at their eastern outcrop: Sayabec (Wenlockian-Gedinnian), St. Leon (Ludlovian-Gedinnian), and Cap Bon Ami (Pridolian-Siegenian). The position of the Silur an-Devonian boundary in Gaspe Peninsula is discussed in relation with the position of this boundary in the so-called "standard" (of New York) for the Devonian of North America.

Silurian and Basal Devonian Stratigraphy of Northeastern Gaspe Peninsula, Quebec

Two New Genera of Stricklandid Brachiopods

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Two New Genera of Stricklandid Brachiopods