Oamaru Diatoms
Scanning Electron Microscope Images
by Mary Ann Tiffany

bains2_orig.jpg
Seam of Diatomite Adjacent to Collection Outcrop

Update June 2023. This earlier html version retained for issue archive but has been replaced by a pdf version here where nearly all species have been identified.

Introduction

IntroductionImage GalleryAcknowledgementsAppendicesReferences

The rolling hills near the town of Oamaru, on the east coast of the South Island of New Zealand, are famous for their beds of Late Eocene-Early Oligocene diatomite, laid down about 32-35 million years ago. The beds are exposed at several sites sandwiched between igneous and limestone layers on farms around Oamaru (Dailey 2004). While the rolling hills of the Oamaru region are not especially remarkable, the diatomite found there is quite remarkable indeed! Some people mine the diatomite for products such as kitty litter while some of us appreciate these fossil beds for learning.

The climate during this period was much warmer than now with tropical seas dominating the planet, tropical forest common on land, and temperate forests reaching all the way to near the North and South Poles.

The beds were deposited in a shallow, tropical sea rich in nutrients which encouraged successive plankton blooms. The diatom flora speciated wildly, resulting in the fantastic diversity found in the diatomite, including some of the most exotic marine forms in the world. The beds are believed to have formed in a quiet basin about 50 kilometers offshore that received very little terrestrial sediment. The silica skeletons of the diatoms fell on the sea floor and were covered and compressed by overlying layers of plankton to form the soft rock, diatomite. Subsequently, they were covered by volcanic deposits and earth movements. Remarkably, many of these diatoms remain intact and perfectly preserved over many millions of years.

This speciation resulted in perhaps the most diverse fossil marine diatom community ever recorded with over 700 species from about 120 genera. A few species have been recorded only from Oamaru (e.g. species of Kittonia). Others are known from widely dispersed Eocene-Oligocene fossil sites around the world, such as Barbados, providing evidence that tropical seas were interconnected during these epochs. Some species are still living today. (Richman & Carter 2007, Charles 2017, Edwards 1991)

The specimens in this collection came from Bain's Farm near Oamaru in New Zealand (lat -45.100657 lon 170.888204, elevation ~ 100 meters). In 2003, friends of Bill Dailey collected samples at the outcrop of diatomite shown at the arrow in the illustration. Bill cleaned the samples and sent material to Mary Ann Tiffany (then at the Center for Inland Waters and Department of Biology of San Diego State University, California, US) who made the images in this collection. This web page is a tribute to their work.

This selection of images is certainly not an exhaustive inventory of Oamaru diatoms but it contains studies of genera such as Kittonia, Gyrosigma, and Aulacodiscus.

IntroductionImage GalleryAcknowledgementsAppendicesReferences

The Group column contains names adapted from the morphological groups used on Diatoms of North America. Centric diatoms have been split into radial and polar groups. Some genera defy these categories. For example, Stictodiscus is assigned to centric radials but contains members that have definite poles. The Name column contains our attempts to identify the diatoms. (Names are without italics for faster sorting.) Several specimens are identified to genus with a provisional species identifier until more is learned. In the file name below the image, the number stands for the magnification, "tilt" signifies that the specimen was tilted at 45 degrees in the SEM, and a letter before "tilt" or the magnification in a group of images denotes the same specimen. The Comment column contains our observations about the specimen.

Sorting columns can be done in several ways. (1) Sort Group or Name by clicking on the heading. Click again to the reverse the sort. Sorting by Name may be the most useful since it puts all those with the same name together. (2) Sort on two columns by arranging the second column of the sort, then arrange the first column. (3) Restore the file name order by reloading the page.

For a larger image, click on an image in the gallery. It will open in a separate tab, allowing several images to be open at once. This window also contains the references for the specimen. Click the X or press Esc to close the image.

The species list, arranged by Name and Group, can be found here. See the Appendix for abbreviations used in the names.

A Sense of Scale
Magnification is the last part of the file name below each image.
Image widths in microns (µm), rounded to nearest whole number.
Magnification 200 250 300 350 400 450 500 600 700 800 900 1000 1100
Width (µm) 583 467 389 333 292 260 233 194 167 146 130 117 106
Magnification 1300 1500 1800 2000 2500 3000 3500 4000 4500 5000 6000 7000
Width (µm) 90 78 65 58 47 39 33 29 26 23 19 17
Group Name Image Comment
Centric RadialAsterolampra insignis (I)oamar3a800.jpg
oamar3a800
Internal view of valve. Open chambers of the raised rays appear as black bars. Species distinguished by trapezoidal blocks of areolae at the margin between the rays.
Centric RadialAsterolampra insignis (I)oamar3a2000.jpg
oamar3a2000
Internal view of central area. Detail of image oamar3a800.
Centric RadialAsterolampra insignis (I)oamar3a4500.jpg
oamar3a4500
Internal view of valve edge showing internal opening of a rimoportula at end of open chamber. Detail of image oamar3a800.
Centric RadialAsterolampra vulgaris (I)oamar3b1100.jpg
oamar3b1100
Internal view of eroded valve. Species distinguished by the pair of rows of closely packed pores on each side of the ray chamber.
Centric PolarKittonia elaborataoamar3c800.jpg
oamar3c800
Internal valve view.
Centric PolarKittonia elaborataoamar3c2500.jpg
oamar3c2500
Internal view of rimoportulae in central area. Detail of image oamar3c800.
Centric PolarKittonia elaborataoamar3c3000.jpg
oamar3c3000
Internal view of opening to one of the tubular processes. Detail of image oamar3c800.
Centric RadialBrightwellia coronataoamar3d900.jpg
oamar3d900
External valve view. Diameter 89 µm.
Centric RadialBrightwellia coronataoamar3d4000.jpg
oamar3d4000
Detail of image oamar3d900. External view of ring of ovals and areolae.
Centric RadialAsterolampra vulgaris (E)oamaru_3a1300.jpg
oamaru_3a1300
External valve view. Species distinguished by the pair of rows of densely packed pores on each side of the raised ray.
Centric RadialAsterolampra vulgaris (E)oamaru_3a5000.jpg
oamaru_3a5000
Detail of external valve view. Pair of densely packed rows of pores on each side of raised ray. Rimportula visible at base of eroded ray hole.
Centric RadialAsterolampra vulgaris (E)oamaru_3atilt1500.jpg
oamaru_3atilt1500
External valve view tilted.
Centric RadialAsterolampra vulgaris (E)oamaru_3atilt3000.jpg
oamaru_3atilt3000
External valve view detail. Two eroded ray holes each with rimoportula at its bottom lip.
Centric RadialStictodiscus californicus var. nitidaoamaru_3btilt1800.jpg
oamaru_3btilt1800
External valve view.
Centric RadialAulacodiscus cellulosusoamaru_3c450.jpg
oamaru_3c450
External valve view. Distinctive central rosette and two parallel rows of areolae along the furrows leading to the rimoportulae.
Centric RadialAulacodiscus cellulosusoamaru_3c1500.jpg
oamaru_3c1500
Detail of image oamaru_3c450.
Centric RadialAulacodiscus cellulosusoamaru_3ctilt500.jpg
oamaru_3ctilt500
External valve view. Distinctive central rosette and two parallel rows of areolae along the furrows leading to the rimoportulae.
Centric RadialAulacodiscus cellulosusoamaru_3ctilt1500.jpg
oamaru_3ctilt1500
External view of valve margin.
Centric RadialAulacodiscus cellulosusoamaru_3ctilt2500.jpg
oamaru_3ctilt2500
Detail of external opening of a rimoportula.
Centric RadialAulacodiscus sollittianus var. novaezealandicaoamaru_3d1tilt900.jpg
oamaru_3d1tilt900
External valve view tilted. Distinguishing features of this species include (a) angular areolae covering surface of valve (cribra, which usually occlude areolae in this genus, appear to have eroded); (b) distal ends of rimoportulae broadly rounded; (c) collar visible at junction of mantle and valvocopula; (d) valvocopula with vertical rows of small areolae.
Centric RadialAulacodiscus sollittianus var. novaezealandicaoamaru_3d1tilt1800.jpg
oamaru_3d1tilt1800
Detail of image oamaru_3d1tilt900 showing areolae, rimoportula, mantle collar, and valvocopula.
Centric RadialAulacodiscus sollittianus var. novaezealandicaoamaru_3d800.jpg
oamaru_3d800
External valve view. Distinguishing features of this species include (a) angular areolae covering surface of valve (cribra, which usually occlude areolae in this genus, appear to have eroded); (b) distal ends of rimoportulae broadly rounded; (c) collar visible at junction of mantle and valvocopula; (d) valvocopula with vertical rows of small areolae.
Centric RadialAulacodiscus sollittianus var. novaezealandicaoamaru_3d1800.jpg
oamaru_3d1800
Detail of areolae on valve face, distal end of a rimoportula, and valvocopula below the mantle rim.
Centric RadialAulacodiscus cellulosusoamaru_3e450.jpg
oamaru_3e450
External view of valve with two broken rimoportulae. Distinctive central rosette and two parallel rows of areolae along the furrows leading to the rimoportulae.
Centric RadialAulacodiscus cellulosusoamaru_3e4000.jpg
oamaru_3e4000
Detail of broken rimoportula.
Centric PolarKittonia elaborataoamaru_3f1300.jpg
oamaru_3f1300
View of external process (a type of ocellus).
Centric PolarKittonia elaborataoamaru_3f2000.jpg
oamaru_3f2000
View of external openings of central rimoportulae.
Centric PolarKittonia elaborataoamaru_3f3000.jpg
oamaru_3f3000
View of external process (a type of ocellus).
Centric PolarKittonia elaborataoamaru_3ff1300.jpg
oamaru_3ff1300
View of external process (a type of ocellus).
Centric PolarKittonia elaborataoamaru_3fffftilt500.jpg
oamaru_3fffftilt500
Whole valve.
Centric PolarKittonia elaborataoamaru_3ffftilt500.jpg
oamaru_3ffftilt500
Whole valve.
Centric PolarKittonia elaborataoamaru_3fftilt900.jpg
oamaru_3fftilt900
Magnification of whole valve.
Centric PolarKittonia elaborataoamaru_3ftilt500.jpg
oamaru_3ftilt500
Whole valve.
Centric PolarKittonia elaborataoamaru_3ftilt900.jpg
oamaru_3ftilt900
Magnification of whole valve.
Centric PolarKittonia elaborataoamaru_3ftilt2500.jpg
oamaru_3ftilt2500
View of external openings of central rimoportulae.
Centric RadialAsterolampra insignis (E)oamaru_3g1000.jpg
oamaru_3g1000
External view of valve. Diameter 93 µm. Raised rays lie between blocks of areoale. Species distinguished by trapezoidal blocks of areolae at the margin between the rays.
Centric RadialAsterolampra insignis (E)oamaru_3g2000.jpg
oamaru_3g2000
External view of central area.
Centric RadialAsterolampra insignis (E)oamaru_3g3500.jpg
oamaru_3g3500
External view of valve margin.
Centric RadialAsterolampra insignis (E)oamaru_3gtilt1100.jpg
oamaru_3gtilt1100
External valve view tilted. Illustrates ray holes with tiny rimoportula at the base of each ray hole.
Centric RadialAsterolampra insignis (E)oamaru_3gtilt3500.jpg
oamaru_3gtilt3500
Detail of external view of valve margin. Illustrates eroded ray holes with tiny rimoportula at the base of each ray hole.
Centric PolarTriceratium secedensoamaru_3htilt350.jpg
oamaru_3htilt350
External view. Convex sides separate this from T. pantocsekii.
Centric RadialAulacodiscus cellulosusoamaru_3i500.jpg
oamaru_3i500
Internal view of valve. Distinctive ring around central area and pair of parallel rows of areolae along the rays leading to the rimoportulae. Internal openings of rimoportulae visible.
Centric RadialAulacodiscus cellulosusoamaru_3i4000.jpg
oamaru_3i4000
Internal view of valve edge showing opening of a marginal rimoportula.
Centric RadialAulacodiscus cellulosusoamaru_3itilt4000.jpg
oamaru_3itilt4000
Internal view of valve edge tilted showing opening of a marginal rimoportula.
Centric RadialAulacodiscus cellulosusoamaru_3itilt4500.jpg
oamaru_3itilt4500
Internal view of valve edge tilted showing opening of a marginal rimoportula. Also visible in some of the areolae are cribra covering the exterior side.
Centric RadialAulacodiscus janischiioamaru_3j200.jpg
oamaru_3j200
External view of valve. Diameter 354 µm.Distinguished by (a) tangentially undulating valve surface, (b) small hyaline area in the center, (c) small areolae of nearly uniform size covering the valve, (d) lack of ribs showing in SEM, (e) uniform spacing of the striae (slightly wider on the crests), (f) rimoportulae near the margin protruding from the crests.
Centric RadialAulacodiscus janischiioamaru_3j700.jpg
oamaru_3j700
External view of valve edge showing opening of two marginal rimoportulae.
Centric RadialAulacodiscus janischiioamaru_3j1800.jpg
oamaru_3j1800
External view of valve edge showing opening of a marginal rimoportulae.
Centric RadialAulacodiscus janischiioamaru_3jjtilt300.jpg
oamaru_3jjtilt300
External view of valve tilted. Distinguished by (a) tangentially undulating valve surface, (b) small hyaline area in the center, (c) small areolae of nearly uniform size covering the valve, (d) lack of ribs showing in SEM, (e) uniform spacing of the striae (slightly wider on the crests), (f) rimoportulae near the margin protruding from the crests.
Centric RadialAulacodiscus janischiioamaru_3jtilt1500.jpg
oamaru_3jtilt1500
External view of valve edge showing opening of a marginal rimoportulae.
Centric RadialAulacodiscus janischiioamaru_3jtilt1800.jpg
oamaru_3jtilt1800
External view of valve edge showing opening of a marginal rimoportulae.
Centric PolarSheshukovia castelliferaoamaru_3k1500.jpg
oamaru_3k1500
Single valve. Girdle view.
Centric PolarSheshukovia castelliferaoamaru_3ktilt1800.jpg
oamaru_3ktilt1800
Single valve. Girdle view.
Centric RadialAulacodiscus amoenusoamaru_3l450.jpg
oamaru_3l450
External view. Valve convex in center, rising suddenly to a marginal ridge with rimoportulae protruding away from center on marginal side of the ridge.
Centric RadialAulacodiscus amoenusoamaru_3l1800.jpg
oamaru_3l1800
Detail of external margin with rimoportula.
Centric RadialAulacodiscus amoenusoamaru_3ltilt500.jpg
oamaru_3ltilt500
External view tilted. Valve convex in center, rising suddenly to a marginal ridge with rimoportulae protruding away from center on marginal side of the ridge.
Centric RadialAulacodiscus amoenusoamaru_3ltilt1800.jpg
oamaru_3ltilt1800
Detail of external margin with rimoportula.
Centric RadialAulacodiscus amoenusoamaru_3ltilt2000.jpg
oamaru_3ltilt2000
Detail of external margin with rimoportula.
Centric PolarKittonia elaborataoamaru_3mtilt1300.jpg
oamaru_3mtilt1300
Internal view of rimoportulae in central area.
Centric RadialAulacodiscus janischiioamaru_3n2500.jpg
oamaru_3n2500
Detail of internal view of margin and inner opening of a rimoportula.
Centric RadialAulacodiscus janischiioamaru_3ntilt2500.jpg
oamaru_3ntilt2500
Detail of internal view tilted of margin and outer opening of a rimoportula in image oamaru_3n2500.
Centric RadialAulacodiscus sollittianus var. novaezealandicaoamaru_3ootilt1500.jpg
oamaru_3ootilt1500
Detail of rimoportula in image oamaru_3otilt500. Faint lines at edge of some areolae may be remainder of cribra.
Centric RadialAulacodiscus sollittianus var. novaezealandicaoamaru_3otilt500.jpg
oamaru_3otilt500
External valve view tilted. Distinguishing features of this species include (a) angular areolae covering surface of valve (cribra, which usually occlude areolae in this genus, appear to have eroded); (b) distal ends of rimoportulae broadly rounded; (c) collar visible at junction of mantle and valvocopula; (d) valvocopula with vertical rows of small areolae.
Centric RadialAulacodiscus sollittianus var. novaezealandicaoamaru_3otilt1500.jpg
oamaru_3otilt1500
Detail of external view clearly showing the base of the rimoportula. The concoidal fractures on flange at the mantle edge suggest broken glass.
Centric PolarSheshukovia castelliferaoamaru_3ptilt1100.jpg
oamaru_3ptilt1100
Single valve. Tilted view.
Centric RadialEllerbeckia clavigeraoamaru_3qtilt1800.jpg
oamaru_3qtilt1800
Internal view of two sibling linking valves. Diameter 44 µm. See image oamaru_3qtilt5000 for detail view. For an external view, see Ellerbeckia clavigera image oamaru3qtilt1300.
Centric RadialEllerbeckia clavigeraoamaru_3qtilt5000.jpg
oamaru_3qtilt5000
Magnified image of oamaru_3qtilt1800. Exterior of mantles of two sibling linking valves. Top valve is the intaglio valve. Bottom valve is the cameo valve with the step appearing as the light line two or three pores below the links. The black marks are spaces in the interlocking ridges and grooves. Image width 23 µm.
Centric RadialEndictya oceanicaoamaru_3rtilt500.jpg
oamaru_3rtilt500
External view. Valve center has a few projections intact but many appear to be crushed; valve rim has narrow flange and line of pores. See also internal view of an Endictya in this collection. Witkowski et al. (2017) figs 145-146 does not appear to have enough detail to distinguish Pyxilla from Endictya.
Centric PolarTriceratium castellatum var. fractumoamaru_3s700.jpg
oamaru_3s700
External view of valve with raised porefields on the poles.
Centric PolarTriceratium castellatum var. fractumoamaru_3s1500.jpg
oamaru_3s1500
Detail of a raised porefield at a pole.
Centric PolarTriceratium castellatum var. fractumoamaru_3stilt700.jpg
oamaru_3stilt700
External view of valve with raised porefields on the poles.
Centric PolarKittonia elaborataoamaru_3ttilt2500.jpg
oamaru_3ttilt2500
External openings of central rimoportulae in magnified view of image oamaru_3tttilt600.
Centric PolarKittonia elaborataoamaru_3tttilt600.jpg
oamaru_3tttilt600
Whole valve with fractured processes.
Centric PolarKittonia elaborataoamaru_3tttilt2500.jpg
oamaru_3tttilt2500
Fractured ocellus in magnified view of image oamaru_3tttilt600.
Centric PolarKittonia elaborataoamaru_3tttilt4000.jpg
oamaru_3tttilt4000
External opening of fractured stem of process in magnified view of image oamaru_3tttilt600.
Centric PolarRutilaria radiataoamaru2a1000.jpg
oamaru2a1000
External view of valve of a long form. Length 123 µm. Ocellus at one end is eroded. The opposite ocellus is missing. The twisted periplekton (a specialized rimoportula) arises from the center.
Centric PolarRutilaria radiataoamaru2a4000.jpg
oamaru2a4000
Detail of external view of periplekton of image oamaru2a1000. Erosion in two locations has exposed the hollow interior.
Centric PolarRutilaria radiataoamaru2aatilt1000.jpg
oamaru2aatilt1000
External view of valve tilted. Ocellus at one end is eroded. The opposite ocellus is missing. The twisted periplekton (a specialized rimoportula) arises from the center.
Centric PolarRutilaria radiataoamaru2atilt1000.jpg
oamaru2atilt1000
External view of valve tilted. Ocellus at one end is eroded. The opposite ocellus is missing. The twisted periplekton (a specialized rimoportula) arises from the center.
Centric PolarRutilaria radiataoamaru2atilt2000.jpg
oamaru2atilt2000
Detail of periplekton. Erosion has exposed the hollow interior.
Centric PolarRutilaria radiataoamaru2atilt4000.jpg
oamaru2atilt4000
Detail of periplekton. Erosion has exposed the hollow interior.
Centric PolarRutilaria radiataoamaru2atilt5000.jpg
oamaru2atilt5000
Detail of marginal spines.
Centric RadialEndictya sp1oamaru2btilt1600.jpg
oamaru2btilt1600
Internal view. Areolae on mantle variable in size (in contrast to Endictya oceanica). Internal apertures of rimoportulae at angle of mantle and face. Internal pores arranged in rows radiating from valve center (similar to Melosira and Stephanopyxis).
Centric PolarEntogoniopsis venosaoamaru2ctilt1000.jpg
oamaru2ctilt1000
Pseudocelli raised on elevations and have a plain rim. Areolae large near center, smaller beneath elevations. Mantles distinct and vertical. See images oamaru21100 and oamaru22000 for other views of this specimen.
Centric PolarRutilaria radiataoamaru2d1500.jpg
oamaru2d1500
External valve view of a short form. Length 73 µm. Both ocelli, eroded, are visible at the poles. In the center, a fragment of the sibling valve shows the internal opening of the periplekton.
Centric PolarRutilaria radiataoamaru2d5000.jpg
oamaru2d5000
Detail of eroded ocellus of image oamaru2d1500.
Centric PolarRutilaria radiataoamaru2dtilt_1500.jpg
oamaru2dtilt_1500
External valve view of a short form, tilted. Length 73 µm. Both ocelli, eroded, are visible at the poles. In the center, a fragment of the sibling valve shows the internal opening of the periplekton.
Centric PolarRutilaria radiataoamaru2dtilt_1800.jpg
oamaru2dtilt_1800
External valve view of a short form, tilted. Length 73 µm. Both ocelli, eroded, are visible at the poles. In the center, a fragment of the sibling valve shows the internal opening of the periplekton.
Centric RadialBrightwellia coronataoamaru2etilt_3500.jpg
oamaru2etilt_3500
External view of areolae and ring of ovals. More eroded than other Brightwellia specimens here.
Centric RadialAsterolampra insignis (I)oamaru2ftilt_1000.jpg
oamaru2ftilt_1000
Internal valve view.
Centric RadialStephanopyxis sp1oamaru2gtilt_1500.jpg
oamaru2gtilt_1500
Two sibling valves joined by the valve faces. Internal openings to rimoportulae visible on the top valve.
Centric RadialArachnoidiscus oamaruensisoamaru2htilt_1100.jpg
oamaru2htilt_1100
External view of tilted valve. Diameter 95 µm. Species epithet oamaruensis was chosen by (1) key in Brown 1933, lead 17: primary rays slender, penetrating to the fourth, third, or second circle of areolae; and (2) the central area in this SEM which could be intepreted as hyaline, matching image in Charles 2017 and Brown 1933.
Biraphid SymmetricalGyrosigma sp1oamaru2i700gyrosigma.jpg
oamaru2i700gyrosigma
Internal view. Length = 184 µm. It might be surprising to see a diatom associated with mud flats in this collection. This specimen might be an indicator of the volcanic shoals that occassionally formed in the basin where the sediments were accumulating.
Biraphid SymmetricalGyrosigma sp1oamaru2i4500.jpg
oamaru2i4500
Internal view. Central area with proximal raphe ends.
Biraphid SymmetricalGyrosigma sp1oamaru2ii4500.jpg
oamaru2ii4500
Internal view. Apex with distal raphe ending in a helictoglossa.
Centric RadialHyalodiscus laevisoamaru2j600.jpg
oamaru2j600
External view of valve. Diameter 112 µm.
Centric RadialHyalodiscus laevisoamaru2jtilt800.jpg
oamaru2jtilt800
External view of valve tilted. Diameter 112 µm.
Centric RadialHyalodiscus laevisoamaru2jtilt1800.jpg
oamaru2jtilt1800
Detail of valve margin.
Centric PolarTrinacria excavataoamaru2ktilt1100.jpg
oamaru2ktilt1100
Genus distinguished by valves with 3 or 4 poles elevated at the corners. Elevations have spines which interlock neatly with the corresponding poles on adjacent cells.
Centric PolarTrinacria excavataoamaru2ktilt4500.jpg
oamaru2ktilt4500
Detail of image oamaru2ktilt1100. Corner eroded. Linking spines visible.
Centric PolarTrinacria excavataoamaru2ktilt5000.jpg
oamaru2ktilt5000
Detail of image oamaru2ktilt1100. Linking spines clearly visible.
Centric RadialAsterolampra vulgaris (E)oamaru2ltilt1500.jpg
oamaru2ltilt1500
External valve view.
Centric PolarHemiaulus sp1oamaru2mtilt1800.jpg
oamaru2mtilt1800
Girdle view of valve tilted.
Centric PolarPyxilla prolungataoamaru2ntilt1000.jpg
oamaru2ntilt1000
Tilted view of a valve.
Centric PolarWilliamriedelia tenuicornisoamaru2otilt1500.jpg
oamaru2otilt1500
Girdle view of complete valve. May also be placed in Riedelia.
Centric RadialPodosira corollaoamaru2ptilt1800.jpg
oamaru2ptilt1800
External view of valve tilted. These specimens look nothing like the images for Podosira in Round et al. Perhaps it is a different genus. Schmidt calls this P. corolla and D&S and DiatomBase use Schmidt as the source. Charles calls it P. corolla on the index but P. coronata on the image. Charles has an excellent LM image.
Centric RadialBrightwellia coronataoamaru2ptilt3500.jpg
oamaru2ptilt3500
Detail of external view of ring of ovals. Four of the ovals demonstrate the chamber beneath the oval and the corresponding single, round foramen leading to the cell interior.
Centric RadialPodosira corollaoamaru2qtilt1500.jpg
oamaru2qtilt1500
External view of valve tilted. These specimens look nothing like the images for Podosira in Round et al. Perhaps it is a different genus. Schmidt calls this P. corolla and D&S and DiatomBase use Schmidt as the source. Charles calls it P. corolla on the index but P. coronata on the image. Charles has an excellent LM image.
Centric RadialCestodiscus spiniferoamaru2r700.jpg
oamaru2r700
Internal view. Diameter = 106 µm. Distinguished from Arachnoidiscus by having no central ring with attached flange.
Centric PolarTriceratium pulvinaroamaru2s800.jpg
oamaru2s800
Internal view of valve. Rows of pores clustered and radiating from center of valve. Distance between adjacent apices at top of image 100 µm. Compare to T. unguiculatum.
Centric PolarTriceratium pulvinaroamaru2s3000.jpg
oamaru2s3000
Detail of internal view of an apex. Rows of pores clustered and radiating from center of valve. Compare to T. unguiculatum.
Centric PolarHemiaulus sp1oamaru2t1500.jpg
oamaru2t1500
Girdle view of valve.
Centric RadialPodosira corollaoamaru2t4500.jpg
oamaru2t4500
Detail of junction between valve face and mantle showing rimoportulae and striated band.
Centric PolarEntogoniopsis pseudonervataoamaru2utilt1000.jpg
oamaru2utilt1000
Pseudocelli on the poles have no rim. Mantles distinct and vertical.
Centric RadialCestodiscus spiniferoamaru2v1300.jpg
oamaru2v1300
External view. Diameter = 63 µm. Distinguished from Arachnoidiscus by having no central ring with attached flange.
Centric RadialCestodiscus spiniferoamaru2wtilt1500.jpg
oamaru2wtilt1500
Internal view. Tilted view of oamaru2ww1300. Diameter = 58 µm. Distinguished from Arachnoidiscus by having no central ring with attached flange.
Centric RadialCestodiscus spiniferoamaru2ww1300.jpg
oamaru2ww1300
Internal view. Diameter = 58 µm. Distinguished from Arachnoidiscus by having no central ring with attached flange.
Centric PolarTriceratium favus var. quadrataoamaru2x900.jpg
oamaru2x900
Internal view of valve. Clustered pores radiate from the center.
Centric PolarTriceratium favus var. quadrataoamaru2xtilt500.jpg
oamaru2xtilt500
External view of valve tilted.
Centric PolarTriceratium favus var. quadrataoamaru2xtilt800.jpg
oamaru2xtilt800
Internal view of valve tilted.
Centric PolarTriceratium favus var. quadrataoamaru2xtilt2500.jpg
oamaru2xtilt2500
Detail of internal view of apex.
Centric PolarTriceratium favus var. quadrataoamaru2xxtilt2500.jpg
oamaru2xxtilt2500
Internal view of an ocellus at an apex.
Centric RadialAulacodiscus cellulosusoamaru3_a350.jpg
oamaru3_a350
Internal view of valve. Distinctive ring around central area and pair of parallel rows of areolae along the rays leading to the rimoportulae. Internal openings of rimoportulae eroded in the same direction.
Centric RadialAulacodiscus cellulosusoamaru3_a3000.jpg
oamaru3_a3000
Detail of internal view of eroded rimoportula.
Centric RadialAulacodiscus cellulosusoamaru3_atilt450.jpg
oamaru3_atilt450
Internal view of valve tilted. Distinctive ring around central area and pair of parallel rows of areolae along the rays leading to the rimoportulae. Internal openings of rimoportulae eroded in the same direction.
Centric RadialAsterolampra insignis (I)oamaru3_b1800.jpg
oamaru3_b1800
Detail of internal view of central area.
Centric RadialAsterolampra insignis (I)oamaru3_btilt1100.jpg
oamaru3_btilt1100
Internal valve view.
Centric RadialAsterolampra vulgaris (I)oamaru3_c1300.jpg
oamaru3_c1300
Internal view of valve. Visible are long ray chambers and short chambers on either side.
Centric RadialAsterolampra vulgaris (I)oamaru3_c2000.jpg
oamaru3_c2000
Detail of internal view of valve. The short parallel chambers show pores in the external side. At end of each ray chamber is the internal opening of a rimoportula.
Centric RadialAsterolampra vulgaris (I)oamaru3_c3500.jpg
oamaru3_c3500
Detail of internal view of central area.
Centric RadialAsterolampra vulgaris (I)oamaru3_ctilt1300.jpg
oamaru3_ctilt1300
Internal view of valve tilted. Visible are ray chambers with ray holes at the distal ends and a cross section of the valve edge.
Centric RadialAsterolampra vulgaris (I)oamaru3_d800.jpg
oamaru3_d800
Internal view of the valve.
Centric RadialAsterolampra vulgaris (E)oamaru3_d24500.jpg
oamaru3_d24500
Detail of valve edge. Visible are rows of dense pores, ray holes, and rimoportulae at base of ray holes.
Centric RadialAulacodiscus aemulansoamaru3_de3000.jpg
oamaru3_de3000
Detail of external valve edge. Cribra with a daisy shape cover the areolae. One rimoportula stem visible.
Centric RadialAulacodiscus aemulansoamaru3_e7000.jpg
oamaru3_e7000
Cribra with a daisy shape cover the areolae.
Centric RadialAulacodiscus aemulansoamaru3_etilt600.jpg
oamaru3_etilt600
External view of valve. Cribra with a daisy shape cover the areolae.
Centric RadialAulacodiscus aemulansoamaru3_etilt2000.jpg
oamaru3_etilt2000
Cribra with a daisy shape cover the areolae.
Centric RadialStictodiscus novaezealandiaeoamaru3_ftilt600.jpg
oamaru3_ftilt600
Internal view of valve. Distance between apices across center 163 µm.
Centric RadialStictodiscus novaezealandiaeoamaru3_ftilt3000.jpg
oamaru3_ftilt3000
Internal view of an apex.
Centric RadialStictodiscus novaezealandiaeoamaru3_ftilt4000.jpg
oamaru3_ftilt4000
Internal view of rimoportulae in central area.
Centric RadialAulacodiscus janischiioamaru3_g200.jpg
oamaru3_g200
Internal view of valve.
Centric RadialAulacodiscus janischiioamaru3_gtilt250.jpg
oamaru3_gtilt250
Internal view of valve tilted.
Centric RadialAulacodiscus janischiioamaru3_gtilt1500.jpg
oamaru3_gtilt1500
Internal view of opening of rimoportula.
Centric RadialAulacodiscus janischiioamaru3_gtilt1800.jpg
oamaru3_gtilt1800
External view of rimoportula.
Centric PolarTriceratium castellatum var. fractumoamaru3_h800.jpg
oamaru3_h800
Internal view of valve.
Centric PolarGoniothecium decoratumoamaru3_i1500.jpg
oamaru3_i1500
Girdle view of two cells linked by teeth.
Centric PolarTrinacria ventricosaoamaru3_j900.jpg
oamaru3_j900
Internal valve view.
Centric PolarTrinacria ventricosaoamaru3_j3500.jpg
oamaru3_j3500
Internal view of a pole.
Centric PolarTrigonium glandiferumoamaru3_k700.jpg
oamaru3_k700
Internal view. Heavy internal costae, a septum in each corner, and internal openings of the scattered rimoportulae on the central area of the valve face.
Centric PolarTrigonium glandiferumoamaru3_k1300.jpg
oamaru3_k1300
Internal view. Detail of image oamaru3_k700. Heavy internal costae and internal openings of the scattered rimoportulae on the central area of the valve face.
Centric PolarHemiaulus sp1oamaru3_l1300.jpg
oamaru3_l1300
Girdle view of valve.
Centric PolarTriceratium favus var. quadrataoamaru3a600.jpg
oamaru3a600
External view of valve.
Centric PolarTriceratium favus var. quadrataoamaru3atilt600.jpg
oamaru3atilt600
External view of valve.
Centric PolarTriceratium favus var. quadrataoamaru3atilt2500.jpg
oamaru3atilt2500
Detail of external view of ocellus.
Centric RadialAsterolampra insignis (I)oamaru3b1100.jpg
oamaru3b1100
Internal view of eroded valve.
Centric RadialAsterolampra insignis (I)oamaru3btilt1100.jpg
oamaru3btilt1100
Internal view of eroded valve tilted. Shows thickness of valve wall.
Centric RadialAsterolampra vulgaris (E)oamaru3c1100.jpg
oamaru3c1100
External valve view. Species distinguished by the pair of rows of densely packed pores on each side of the raised ray.
Centric RadialAsterolampra vulgaris (E)oamaru3c3500.jpg
oamaru3c3500
Detail of external view of central area.
Centric RadialAsterolampra vulgaris (E)oamaru3c4500.jpg
oamaru3c4500
Detail of external margin.
Centric RadialAsterolampra vulgaris (E)oamaru3ctilt1500.jpg
oamaru3ctilt1500
External valve view. Species distinguished by the pair of rows of densely packed pores on each side of the raised ray.
Centric RadialAsterolampra vulgaris (E)oamaru3ctilt6000.jpg
oamaru3ctilt6000
Detail of external margin.
Centric RadialAsterolampra vulgaris (E)oamaru3dtilt4000.jpg
oamaru3dtilt4000
External valve view tilted.
Centric RadialAsterolampra vulgaris (I)oamaru3e1100.jpg
oamaru3e1100
Internal view of valve.
Centric RadialAsterolampra vulgaris (I)oamaru3e3000.jpg
oamaru3e3000
Detail of internal view of ray chambers and parallel side chambers with external pores visible.
Centric RadialAsterolampra vulgaris (I)oamaru3e6000.jpg
oamaru3e6000
Detail of internal view of ray chambers and parallel side chambers with external pores visible.
Centric RadialAsterolampra vulgaris (I)oamaru3ee3000.jpg
oamaru3ee3000
Detail of internal view of central area.
Centric RadialAsterolampra vulgaris (I)oamaru3etilt1500.jpg
oamaru3etilt1500
Internal view of valve tilted. Cross section of valve wall visible.
Centric RadialStictodiscus splendidusoamaru3f400.jpg
oamaru3f400
External view. Distance between apices 208 µm! Pore fields at apices. Very clear example of the raised thickenings surrounding the areolae that define the genus. This specimen defies the category of a Centric Radial diatom.
Centric RadialStictodiscus splendidusoamaru3ftilt2000.jpg
oamaru3ftilt2000
External view of apical pore field. Width of image 58 µm. Very clear example of raised thickenings surrounding the areolae that define the genus.
Centric RadialStephanopyxis sp2oamaru3g900.jpg
oamaru3g900
External view of valve of a domed form.
Centric RadialStephanopyxis sp3oamaru3g1500.jpg
oamaru3g1500
External view of form with nearly flat valve.
Centric RadialCoscinodiscus subdivicusoamaru3h1500.jpg
oamaru3h1500
External view of valve. Radial lines of large areolae lead to the rimoportulae near margin. The marginal rimoportulae suggest an Aulacodiscus.
Centric RadialAulacodiscus aemulansoamaru3i1000.jpg
oamaru3i1000
External view of valve. Cribra with a daisy shape cover the areolae. Some cribra have eroded showing the areolae.
Centric RadialAulacodiscus aemulansoamaru3i4500.jpg
oamaru3i4500
Detail of image oamaru3i1000.
Centric RadialAulacodiscus aemulansoamaru3itilt1100.jpg
oamaru3itilt1100
External view of valve tilted. Cribra with a daisy shape cover the areolae. Tubes of rimoportulae form a ring near the margin.
Centric RadialAulacodiscus aemulansoamaru3itilt3000.jpg
oamaru3itilt3000
Detail of image oamaru3itilt1100. Areola diameter ~ 2.5 µm. Diameter of pore in cribra ~ 0.4 µm. Rimoportula external opening ~ 1.9 µm.
Centric RadialEllerbeckia clavigeraoamaru3itilt3500.jpg
oamaru3itilt3500
External view of both mantles of image oamaru3vtilt1000.
Centric RadialEllerbeckia clavigeraoamaru3itilt6000.jpg
oamaru3itilt6000
Internal view of mantle of intaglio valve of image oamaru3vtilt1000.
Centric RadialStephanopyxis sp2oamaru3jtilt1000.jpg
oamaru3jtilt1000
External view of valve tilted of a domed form.
Centric RadialPodosira corollaoamaru3ktilt2000.jpg
oamaru3ktilt2000
External view of valve tilted. These specimens look nothing like the images for Podosira in Round et al. Perhaps it is a different genus. Schmidt calls this P. corolla and D&S and DiatomBase use Schmidt as the source. Charles calls it P. corolla on the index but P. coronata on the image. Charles has an excellent LM image.
Centric RadialPodosira corollaoamaru3ktilt5000.jpg
oamaru3ktilt5000
Detail of external view of valve edge. Rimoportulae protrude through the striated band. The mantle is below the flange at the junction of face and mantle.
Centric RadialStephanopyxis sp3oamaru3ltilt1800.jpg
oamaru3ltilt1800
External view of form tilted with nearly flat valve.
Centric RadialEllerbeckia sp1oamaru3mtilt1000.jpg
oamaru3mtilt1000
Two linking valve faces, the only preserved parts of these valves. Diameter 106 µm. External view of the bottom valve and internal view of the upper valve. The fine rays around the upper valve are cross-sections of mantle areolae. The hollowed rim of the upper valve was caused by erosion of the valve. The ring of narrow uprights on the lower valve are costae on the valve face visible from the side. They are interlocking with the corresponding costae on the upper valve face.
Centric RadialEllerbeckia sp1oamaru3mtilt4000.jpg
oamaru3mtilt4000
Detail of valve mantles. Image width 29 µm. Two linking valve faces. External view of the bottom valve and internal view of the upper valve. The fine rays around the upper valve are cross-sections of mantle areolae. The hollowed rim of the upper valve was caused by erosion of the valve. The ring of narrow uprights on the lower valve are costae on the valve face visible from the side. They are interlocking with the corresponding costae on the upper valve face.
Centric RadialStephanopyxis sp4oamaru3ntilt1800.jpg
oamaru3ntilt1800
External view of a form with hemispheric valve.
Centric RadialPodosira corollaoamaru3otilt1800.jpg
oamaru3otilt1800
Wide striated band below the flange. External view of valve tilted. These specimens look nothing like the images for Podosira in Round et al. Perhaps it is a different genus. Schmidt calls this P. corolla and D&S and DiatomBase use Schmidt as the source. Charles calls it P. corolla on the index but P. coronata on the image. Charles has an excellent LM image.
Centric RadialEllerbeckia clavigeraoamaru3qtilt1300.jpg
oamaru3qtilt1300
External view of linking valve. The wavy rim suggests the linking area of Ellerbeckia clavigera in image oamaru_3qtilt1800 which shows two sibling valves linked. Diameter 71 µm. Round et al. (1990) has an SEM image very similar to this specimen.
Centric RadialCoscinodiscus subdivicusoamaru3rtilt1800.jpg
oamaru3rtilt1800
External view of valve tilted. Radial lines of large areolae lead to the rimoportulae near margin. The marginal rimoportulae suggest an Aulacodiscus.
Centric PolarTriceratium pantocsekii oamaru3stilt700.jpg
oamaru3stilt700
External view. Straight sides separate this from T. secedens.
Centric RadialCoscinodiscus argusoamaru3stilt1000.jpg
oamaru3stilt1000
Valve diameter 97 µm. Areola diameter ~ 2.2 µm. Areolae on a radius 11-12. By comparison, Coscinodiscus asteroides appears to have denser areolae arranged in more distinct rows and has a more definite central area in Charles and in Heck. Edwards shows a distribution of areolae similar to this specimen.
Centric RadialStrangulonema barbadenseoamaru3stilt1100.jpg
oamaru3stilt1100
External view of valve face with collar at edge giving rise to spines. Round et al. (1990) has these spines as flattened and furcate (forked) though they are not here. Only this one species has been described.
Centric PolarRattrayella oamaruensisoamaru3t1500.jpg
oamaru3t1500
External view. Large openings around the valve margin are ocelli with the coverings of small porelli eroded. Valve diameter = 52 µm. Ocelli diameter = 4 µm. Rimoportulae between the ocelli distinguish this from Glyphodiscus.
Centric PolarRattrayella oamaruensisoamaru3t7000.jpg
oamaru3t7000
External view of an ocellus with covering of small porelli eroded. Ocellus diameter = 4 µm.
Centric PolarRattrayella oamaruensisoamaru3ttilt1500.jpg
oamaru3ttilt1500
External view. Large openings around the valve margin are ocelli with the coverings of small porelli eroded. Valve diameter = 52 µm. Ocelli diameter = 4 µm. Rimoportulae between the ocelli distinguish this from Glyphodiscus.
Centric PolarRattrayella oamaruensisoamaru3ttilt3500.jpg
oamaru3ttilt3500
External view of valve margin with ocelli and rimoportulae. Large openings along the margin are ocelli with the coverings of small porelli eroded. Remnants of the coverings visible around inner edge of an ocellus. Ocellus diameter 4 µm. Rimoportulae between the ocelli distinguish this from Glyphodiscus.
Centric RadialBrightwellia coronataoamaru3u1100.jpg
oamaru3u1100
External view of central area.
Centric RadialEllerbeckia clavigeraoamaru3vtilt1000.jpg
oamaru3vtilt1000
Linking valves of two sibling cells. Intaglio valve (internal view) at the top, cameo valve with the step in the mantle at the bottom. The wavy pattern of the ridges and grooves where the cells join matches the pattern in image oamaru3qtilt1300.
Centric PolarEntogoniopsis venosaoamaru21100.jpg
oamaru21100
Tilted view of image oamaru2ctilt1000. Pseudocelli raised on elevations and have a plain rim. Areolae large near center, smaller beneath elevations. Mantles distinct and vertical.
Centric PolarEntogoniopsis venosaoamaru22000.jpg
oamaru22000
Magnified view of oamaru21100. Pseudocelli raised on elevations and have a plain rim. Areolae large near center, smaller beneath elevations. Mantles distinct and vertical.
Acknowledgements
IntroductionImage GalleryAcknowledgementsAppendicesReferences

Bill Dailey (US) provided the single list of the images used for the gallery. Rob Kimmich (US) provided text and code for the page. Mary Ann Tiffany (US) provided the images, magnification table, identifications, as well as the inspiration to attempt this project. David Walker (UK) hosted the project on Micscape Magazine. Bill and David provided testing and comments on design and content. These collaborators are members of Diatom Forum. Jakub Witkowski (University of Szczecin, Poland) helped greatly with naming specimens and provided insights into problems of working with fossil diatoms.

Appendices
IntroductionImage GalleryAcknowledgementsAppendicesReferences
Appendix I

Several abbreviations are used in the names on this web page (Wikipedia 2023).

var. variety (in Latin, varietas) is a taxonomic rank below species and subspecies, but above form.

f. form (in Latin, forma) is one of the secondary taxonomic ranks and is placed below variety which is below species. It is an infraspecific taxon. If more than three ranks are listed in describing a taxon, this is the "classification" of the taxon. The "name" of the taxon may be reduced to only three parts: a genus name, a specific epithet, and an infraspecific epithet (such as var. or f.).

Appendix II

Version 1 was started in February 2023 and completed in March 2023. This is Version 2. It was started in March 2023 and completed in May 2023. It contains name changes, puts the references in the enlargement window that is reached by clicking an image.

References
IntroductionImage GalleryAcknowledgementsAppendicesReferences

As often happens, diatom references may be out of print or behind various pay walls, though some may be in the public domain. Authors are often willing to share copies of their work.

Brown, N.E. (1933) Arachnoidiscus. Watson & Sons, Ltd, London. http://www.microscopy-uk.org.uk/diatomist/Arachnoidiscus.pdf.

Charles, Nigel (2017). Oamaru diatoms. https://www.oamarudiatoms.co.uk/index.html. [Nigel died in 2018. His website is now maintained by Anne Gleich.]

Crawford, R.[M.] & Sims, P.A. (2006). The diatoms Radialiplicata sol (Ehrenberg) Glezer and R. clavigera (Grunow) Glezer and their transfer to Ellerbeckia Crawford, thus a genus with freshwater and marine representatives. Nova Hedwigia Beiheft 130: 137-162.

Dailey, W. (2004) Oamaru diatomite collection sites. https://diatomsamples.weebly.com/oamaru-diatomite.html.

Desikachary, T.V., and P.M. Sreelatha (1989) Oamaru diatoms. Bibliotheca Diatomologica, Berlin, Band 19, 330 pp plus 145 plates. [Abbreviated here as D&S.]

Edwards, A.R. (compiler) (1991) The Oamaru diatomite. New Zealand Geological Survey Paleontological Bulletin 64, 260 pp.

Guiry, M.D. in Guiry, M.D. & Guiry, G.M. (2016) Rattrayella oamaruensis. AlgaeBase, National University of Ireland, Galway. https://www.algaebase.org; retrieved on 28 February 2023. https://www.algaebase.org/search/species/detail/?species_id=136831

Heck, Paul-Rainer (2015) Die fossilen Diatomeen Oamarus (Neuseeland) aus den Sammlungen von Bernard Hartley und Nigel Charles. Self-published in PDF form.

Kociolek, J.P.; Blanco, S.; Coste, M.; Ector, L.; Liu, Y.; Karthick, B.; Kulikovskiy, M.; Lundholm, N.; Ludwig, T.; Potapova, M.; Rimet, F.; Sabbe, K.; Sala, S.; Sar, E.; Taylor, J.; Van de Vijver, B.; Wetzel, C.E.; Williams, D.M.; Witkowski, A.; Witkowski, J. (2023). DiatomBase. Accessed at https://www.diatombase.org on 2023-04-30. doi:10.14284/504 [Here, Kociolek et al. (2023)]

Miranda, Salvador Valenzuela in Guiry, M.D. & Guiry, G.M. (2016) Ellerbeckia clavigera. AlgaeBase https://www.algaebase.org/search/species/detail/?species_id=147257

Refsnes Data (1999-2023) A school for web developers. https://www.w3schools.com/about/default.asp. [Very useful for writing web applications. Contains many up to date examples of code for web pages.]

Richman, David B and Carter, Richard (2007). Oamaru Diatoms. http://www.microscopy-uk.org.uk/mag/imgjun07/dr-rc-oamaru.pdf.

Ross, Robert (1995) A revision of Rutilaria Greville (Bacillariophyta). Bulletin of the Natural History Museum. Botany series 25(1), 1–93. https://www.biodiversitylibrary.org/item/128057

Round, F.E., Crawford, R.M. & Mann, D.G. (1990). The diatoms: biology and morphology of the genera. pp. [i-ix], 1-747. Cambridge: Cambridge University Press.

Schmidt, A. (0) (1874-1959). Atlas der Diatomaceen-Kunde, von Adolf Schmidt, continued by Martin Schmidt, Friedrich Fricke, Heinrich Heiden, Otto Muller, Friedrich Hustedt. Reprint 1972, 480 plates.

Sims, P.A. (2006) A REVISION OF THE GENUS RATTRAYELLA DE-TONI INCLUDING A DISCUSSION ON RELATED GENERA, Diatom Research, 21:1, 125-158, DOI:10.1080/0269249X.2006.9705656

Spaulding et al. (2021) Glossary. Retrieved on 27 Feb 2023 from https://diatoms.org/glossary.

Spaulding et al. (2023) Taxa by Morphology. Retrieved on 23 Feb 2023 from https://diatoms.org/morphology.

Strelnikova, N.I., Fourtanier, E., and Kociolek, J.P. (2004) MORPHOLOGICAL STUDIES OF AULACODISCUS SPECIES FROM THE “RUSSIAN COLLECTION” OF THE CALIFORNIA ACADEMY OF SCIENCES, Diatom Research, 19:2, 283-310, DOI: 10.1080/0269249X.2004.9705876

Tiffany, Mary Ann (2023) numerous personal communications to identify specimens.

Tiffany, Mary Ann and Hernández-Becerril, David U. (2005) Valve development in the diatom family Asterolampraceae H. L Smith 1872. Micropaleontology, vol. 51, no. 3.

Williams, D.M. (1988) An illustrated catalogue of the type specimens in the Greville diatom herbarium. Bulletin of the British Museum (Natural History), Botany Series Vol 18 No 1.

Witkowski, Jakub (2023a) personal communication.

Witkowski, Jakub (2023b) Fossil diatom atlas (https://fossil-diatoms.com/atlas/index.php?page=atlas-home)

WITKOWSKI, JAKUB, PATRICIA A. SIMS, NINA I. STRELNIKOVA & DAVID M. WILLIAMS (2015) Entogoniopsis gen. nov. and Trilamina gen. nov. (Bacillariophyta): a survey of multipolar pseudocellate diatoms with internal costae, including comments on the genus Sheshukovia Gleser. Phytotaxa 209 (1): 001–089. http://dx.doi.org/10.11646/phytotaxa.209.1.1 [Here, Witkowski et al. (2015).]

Witkowski, Jakub, Patricia A. Sims & David M. Williams (2017) Typification of Eocene–Oligocene diatom taxa proposed by Grove & Sturt (1886–1887) from the Oamaru Diatomite, Diatom Research, 32:4, 363-408. [Here, Witkowski et al. (2017)]

Wikipedia (2023) https://en.wikipedia.org/wiki/Variety_(botany) which refers to the ICN: McNeill, J.; Barrie, F.R.; Buck, W.R.; Demoulin, V.; Greuter, W.; Hawksworth, D.L.; Herendeen, P.S.; Knapp, S.; Marhold, K.; Prado, J.; Prud'homme Van Reine, W.F.; Smith, G.F.; Wiersema, J.H.; Turland, N.J. (2012). International Code of Nomenclature for algae, fungi, and plants (Melbourne Code) adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011. Vol. Regnum Vegetabile 154. A.R.G. Gantner Verlag KG. ISBN 978-3-87429-425-6. Chapter I. Article 4

Version 2

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