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North American cyclocrinitid algae
Nitecki, Matthew H.
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Field Museum of Natural History
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p. vii-[xiv], 182 p. 61 ill., map ; 24 cm.
Cyclocrinitids are marine dasycladaceous algae of Ordovician and Silurian age.
Their skeletal elements consist of a seldom calcified main axis on which
lateral branches are borne in whorls. Calcified heads commonly form at the
termini of the laterals. In North America cyclocrinitids are represented by
three genera: Anomaloides, Cyclocrinites, and Lepidolites. Anomaloides
(=Anomalospongia) possesses laterals calcified throughout their extent. They
expand gently outward, and no heads form. Three secondary laterals form
threadlike projections at the terminus of each lateral. -- Cyclocrinites
(=Cyclocrinus, Lunulites, Cerionites, Pasceolus, Mastopora, and Nidulites)
with a globose thallus is the most diversified genus. The laterals expand at
the termini and form generally six-sided heads. In one species the laterals
branch to the second degree. The lateral heads are in some species supported
by four to six ribs. In at least one species the laterals constrict twice and
form two layers of heads, one above the other. The main axis is generally
short, and attachment is by means of a pedicle that is, however, frequently
not preserved. Calcification generally occurs above and below the lateral
heads. One new species, Cyclocrinites welleri, is described. -- Lepidolites
consists of one species only and is the most modified of all cyclocrinitids.
The laterals are short, small, and calcified; their ends are modified and form
overlapping plates. -- The cyclocrinitids have been variously assigned by many
authors to many groups, particularly as an appendix to the sponges. They are
here considered a basal receptaculitid stock that possesses the simplest
structures. They fill an important gap in the fossil record of Paleozoic
Pt. I: Introduction -- Previous major publications -- Morphology -- Taxonomic
position -- Ecology -- Pt. II: Systematic descriptions -- Pt. III: Original
definitions and descriptions of other authors. -- Annotated bibliography.
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[by] Matthew H. Nitecki --
"November 16, 1970."
Includes bibliographical references (p. 165-182).
Fieldiana series has been published as Geological Series by Field Columbian
Museum (1895-1909) and Field Museum of Natural History (1909-1943), and as
Fieldiana: Geology by Chicago Natural History Museum (1945-1966) and Field
Museum of Natural History (1966-).
QE1 .F4 vol. 21
Fieldiana. v. 21
Publication (Field Museum of Natural History) ; 1110