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Halysis Hoeg, 1932; an Ordovician coralline red alga?

Robert Riding and Juan C. Braga
Halysis Hoeg, 1932; an Ordovician coralline red alga?
Journal of Paleontology (September 2005) 79 (5): 835-841


The systematic position of the Ordovician calcareous microfossil Halysis Hoeg, 1932 has long been uncertain. Only known from thin sections, its morphology has been suggested to be either a single chain of cells or a series of tubes and it has been regarded as a green alga or cyanobacterium. Here we propose that Halysis represents a single sheet of cells. This new morphological interpretation accounts for Halysis's appearance in thin section as an extended flexuous series of cells, some of which are not seen to be in mutual contact, exhibiting nonlinear cell-size variation. It is also consistent with the absence of tubiform sections unequivocally attributable to HALYSIS: This reassessment suggests comparisons between Halysis and Mesozoic-Cenozoic thin laminar unistratose coralline red algae. Halysis cells are relatively large (40-210 mu m), but their lower range is comparable to cells of corallinaceans such as Lithoporella (Foslie) Foslie, 1909. Applanate thallus morphology in Halysis resembles that of thin laminar species of Lithophyllum Philippi, 1837 that were traditionally included in Titanoderma Nageli, 1858. Interpretation of Halysis as a coralline-like alga strengthens the likelihood that a variety of corallines was present in the Ordovician, more than 300 Ma prior to the currently recognized major diversification of this important group of red algae in the Cretaceous.

ISSN: 0022-3360
EISSN: 1937-2337
Serial Title: Journal of Paleontology
Serial Volume: 79
Serial Issue: 5
Title: Halysis Hoeg, 1932; an Ordovician coralline red alga?
Affiliation: Cardiff University, School of Earth, Ocean and Planetary Sciences, Cardiff, United Kingdom
Pages: 835-841
Published: 20050901
Text Language: English
Publisher: Paleontological Society, Lawrence, KS, United States
References: 60
Accession Number: 2005-062625
Categories: Paleobotany
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
N63°07'00" - N63°07'00", E10°00'00" - E10°00'00"
Secondary Affiliation: Universidad de Granada, ESP, Spain
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, The Paleontological Society. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200521
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