The silicoflagellate genus Distephanus (Distephanopsis) Robert Baldwin University Day April 14, 2010

What is a silicoflagellate? “Silicoflagellates are protists and claimed both by zoologists (as protozoans) and botanists (as algae). However, due to their autotrophic phytoplanktonic nature it is more logical to regard them as planktonic algae.” “The silicoflagellates are minute (20−50 µm, rarely up to 100 µm), unicellar, marine flagellates with a siliceous skeleton.” Bilal U. Haq et al., 1978 “The silicoflagellates are a group of planktonic protists, exclusively marine, that contain chromatophores for photosynthesis. In that respect they are like other ‘algae’. They possess a single flagellum, presumably to maintain proper orientation to the sun for maximum efficiency in photosynthetic production. Unlike other “algae”, however, they also possess pseudopodia – a fact that led several early scholars to classify them as ‘animals’.” Richard T. Carter, 2008

How silicoflagellates are used Silicoflagellates are silica-secreting marine microplankton. “Recent revival of interest in the history of ocean basins and paleoclimates has enhanced their importance in paleooceanographic interpretations, especially in those areas where calcareous microfossils are either relatively scarce or completely lacking (e.g., in higher latitudes and deeper waters).” Bilal U. Haq et al., 1978 The carbonate compensation depth The reason why silica fossils are useful in deeper waters is because calcareous fossils dissolve below the calcite compensation depth. The calcite compensation depth (CCD), at the present time, is about 4200 to 4500 meters and can be 5000 meters deep in some places at the present time. It has not always been the same in the past. (Wikipedia)

Skeletal Terminology Figure 1. Maximum length = 65 microns. Richard T. Carter, 2007

Richard T. Carter, 2007

Silicoflagellate descriptive terminology McCartney et al., 1990

Distephanus speculum has a hollow skeleton Y. T. Mandra

Distephanus speculum with a double skeleton J. A. Barron

McCartney et al., 1990

McCartney et al., 1990

McCartney et al., 1990

Pseudofibula Plexus map McCartney et al., 1993

pseudofibulid morphologies McCartney et al., 1990

The second column shows the minimum-distance configuration that connects all points (from Almgren and Taylor, 1976; Isenberg, 1976). McCartney et al., 1990

Scanning electron micrographs of specimens of the pseddofibula plexus from Leg 113, 100x. McCartney et al., 1990

Pseudofibula Plexus of Distephanus speculum speculum from ODP Leg 113 McCartney et al., 1990

Richard T. Carter, 2008

Richard T. Carter, 2008

Distribution of Dictyocha and Distephanus McCartney, 1995 Distephanus

Multiwindowed morphologies and some many sided types from ODP Leg 113 McCartney et al., 1990

Cretaceous genera McCartney et al., 1990

Wide band indicates relative abundance > 50 %. Narrow band denotes relative abundance = 10 %. Line indicates a regular presence. Small numbers refer to DSDP Leg. McCartney, 1987

Richard T. Carter, 2008

Richard T. Carter, 2007

Corbisema triacantha (Ehrenberg) McCartney et al., 1990

Richard T. Carter, 2007

Richard T. Carter, 2008

Richard T. Carter, 2007

Richard T. Carter, 2008

Richard T. Carter, 2007

Richard T. Carter, 2008

Richard T. Carter, 2007

Dictyocha calida Poelchau, abapical view McCartney et al., 1990

Richard T. Carter, 2008

Richard T. Carter, 2007

Richard T. Carter, 2008

Richard T. Carter, 2007

Richard T. Carter, 2007

Richard T. Carter, 2007

Distephanus bolivensis McCartney et al., 1990

Distephanus polyactis 1973

Cannopilus hemisphaericus A Bachmann et al., 1963

Cannopilus hemisphaericus A Bachmann et al., 1963

Richard T. Carter, 2008

Cannopilus sphaericus A Bachmann et al, 1963

Cannopilus picassori A Bachmann et al., 1963

Cannopilus picassori A Bachmann et al., 1963

References: Silicoflagellate: Distephanus speculum, showing hollow skeleton. Upper Miocene near San Felipe, Baja California. Upper specimen is about 60 microns from spine tip to tip. Scanning electron micrograph. From Y. T. Mandra and H. Mandra, Occasional Papers of the California Academy of Sciences, no. 99. Used with the permission of Y. T. Mandra, San Francisco State University. Silicoflagellate: Distephanus speculum with a double skeleton. Late Miocene. Lompoc, California. Length is 45 microns. Courtesy of J. A. Barron, U. S. G. S. http://www.cushmanfoundation.org/resources/slides/silmicros.html Carbonate compensation depth (Wikipedia) This page was last modified on 21 February 2010 http://en.wikipedia.org/wiki/Carbonate_compensation_depth