J. Nannoplankton Res. 32 (1), 2011, pp37-41 © 2011 International Nannoplankton Association
ISSN 1210-8049 Printed by Harcourt Colour Print, Swansea, UK

37

Unusual examples of the silicoflagellate Lyramula simplex
from the Campanian of northwestern Canadian Arctic
Kevin McCartney

Department of Environmental Studies, University of Maine at Presque Isle, Presque Isle, ME 04769 USA email: kevin.mccartney@umpi.edu

David M. Harwood

Department of Geosciences, University of Nebraska-Lincoln, Lincoln, NE 68588-0340 USA

Jakub Witkowski

Department of Historical and Regional Geology, Faculty of Geology, University of Warsaw, ul. Zwirki i Wigury 93, 02-089 Warsaw, Poland
and Department of Paleoceanology, Faculty of Earth Sciences, University of Szczecin, ul. Mickiewicza 18, 70-383 Szczecin, Poland
Manuscript received 4th April, 2010; revised manuscript accepted 10th August, 2010.

Abstract Three varieties of the silicoflagellate Lyramula simplex based on distinct morphological expressions are
documented herein from the Campanian Smoking Hills and Mason River Formations of the Mackenzie District in
the Northwest Territories, Canadian Arctic. The presence of two new morphological structures broaden the species
concept for this taxon to now include specimens with a spine and an inflation or ‘bulb’ at the juncture of the two limbs.
Variability of this species is inferred to result from local environmental variation associated with a nearshore setting
and variable proximity to terrestrial influence. Two new forms of L. simplex are proposed herein, L. simplex var. inflataand L. simplex var. spinosa, to accompany the original morphology of L. simplex var. simplex.
Keywords Silicoflagellate, Upper Cretaceous, Canadian Arctic
1. Introduction
Lyramula simplex is one of five silicoflagellate species reported from the Upper Cretaceous of California by Hanna(1928). This species has a simple robust, tubular siliceous
skeleton forming a “U” shape. It is distinguished from theusually more common and better known Lyramula furcula,which bears a spine at the junction of the two limbs. Hanna(1928) did not explicitly state that L. simplex lacks a spine,
but this has been a commonly held distinction between
these two taxa. This Cretaceous species is also known
from the Ural Mountains (Jousé, 1949, 1951; Gleser 1966)
and from Seymour Island in the Antarctic Peninsula (Harwood, 1988), but it is uncommon to rare at Alpha Ridge in
the Arctic Ocean (Bukry, 1981), at DSDP Site 216 in the
E. Indian Ocean (Bukry, 1974), and Site 275 in the S.W.
Pacific Ocean (Bukry, 1975; Perch-Nielsen, 1975; Hajósand Stradner, 1975). It is absent from shallow-water, neritic
sequences exposed at Devon Island in the Canadian High
Arctic (McCartney et al., 2011a).
2. Results
A new occurrence of L. simplex is reported here from the
Smoking Hills and Mason River Formations near the Horton River, District of Mackenzie in the Northwestern Territories of Canada (Yorath et al., 1975). This taxon was
identified in the course of studies on diatoms (Tapia andHarwood, 2002) and silicoflagellates (McCartney et al.,2011b). Silicoflagellate preservation is excellent in many
samples of the nearly 200 m-thick interval, where L. simplex is present throughout the interval, often as the mostcommon silicoflagellate.
Two interesting varieties of L. simplex are noted in thissection. The first variety possesses a small spine at the
point where the two limbs meet. A second unusual morphology of Lyramula simplex bears an inflated region or‘bulb’ at the junction of the two limbs. Although the presence of a spine would suggest identification as Lyramula
furcula (Plate 1, Fig. 10), other aspects of these skeletonssuggest a closer connection with co-occurring L. simplex,
and they are consistently larger than L. furcula. In addition, the spines are not as long or pointed as with L. furcula. The bulbs are also associated with a skeleton that inshape and size is similar to co-occurring L. simplex. For
these reasons, we conclude that the spine-bearing and bulbous forms are unusual and previously unreported variants of L. simplex.
3. Systematic palaeontology
Lyramula simplex var. simplex Hanna, 1928 n. var.
Pl. 1, Figs 1-5
1928 Lyramula simplex Hanna: pl. 41, figs. 4, 5
Original description: “A simple U-shaped bar of hollow
silica, the terminations being incurved and blunter thanin the preceding species [Lyramula furcula]; the surfaceof the bar is more or less scalariform and pitted on theoutside. Distance from base of U to extreme tips, 0.0932mm” (Hanna, 1928).
Discussion: We distinguish three varieties of L. simplex as an expansion of the morphology of L. simplex
Hanna. Those specimens that most closely match Hanna’s description (without a spine or inflation) are referredhere as L. simplex var. simplex.
Lyramula simplex var. spinosa McCartney,
Harwood & Witkowski (this study)
Pl. 1, Figs 6-9, 11
Description: A simple U-shaped bar of hollow silica,
with two incurved limbs the terminations of which usually point towards each other. The two limbs of this va-

38

McCartney, Harwood, Witkowski

Plate 1
Lyramula simplex

Figs. 1-9, 11-19. Lyramula simplex from the Horton River region, Northwest Territories, Canada. Unless stated otherwise all photographs are fromsample C-9610. Figs 1-5. Specimens exhibiting the common morphology of L. simplex var. simplex, Fig. 4 from sample C-9586; Figs 6-9, 11.
Specimens of L. simplex var. spinosa with a spine, Fig. 9 from sample C-8596; Fig. 10, Specimen of L. furcula; Figs 12, 14. examples of distorted
skeletons of L. simplex, Fig. 14 from sample C-8596; Figs 13, 15-19. Specimens of L. simplex var. inflata with a ‘bulb’ or inflation of the skeleton,
Fig. 13 from sample C-8619; Fig. 17 from sample C-8621.

Unusual examples of the silicoflagellate Lyramula simplex

riety, divided by the small spine, diverge at a more acuteangle than the smooth curve of non-spinose skeletons of
Lyramula simplex var. simplex. The spine on specimensof this variety is short and blunt.
Remarks: Spine-bearing morphologies were noted inall seventeen samples over 80 m of section (distribution
data provided in a range chart in McCartney et al., 2011b).
This spinose variety comprised between 5 and 25% of thetotal number of Lyramula simplex. This variety is lesscommon and less consistent in the upper 20 m of the section, which is of late Campanian to early Maastrichtianage.
Lyramula simplex var. inflata
McCartney, Harwood & Witkowski (this study)
Pl. 1, Figs 13, 15-19
Description: A simple U-shaped bar of hollow silica,
with two incurved limbs the terminations of which usually point towards each other. The point where the two
limbs meet is marked by an obvious inflated area. The
cross-sectional diameter of the skeleton increases to several times the diameter of the limbs outside of the inflated
region. The inflated area may take the shape of a sphereor teardrop-shaped ‘bulb’.
Remarks: A specimen of Lyramula simplex with an
inflation at the point where the two limbs meet was illustrated previously by Jousé (1951), with a form similar
to that illustrated in Plate 1, Figure 4 of this study. Specimens reported herein are generally more pronounced than
the specimen illustrated by Jousé, bearing a bulb-like
ornamentation. More than fifty specimens with inflated
central and bulbous structures were noted through most of
the Horton River section. The relative abundance of thisvariety varied from 0 to more than 50% of all L. simplex
specimens.
4. Discussion
Skeletons of Lyramula simplex are typically large (withlimbs sometimes exceeding 80 μm) and have two limbs
which curve towards the axis of the skeleton, and usually
pointing towards the other limb. Specimens were usuallylarger and of more robust construction than co-occurring
specimens of L. furcula. The distal ends of L. furcula
limbs generally point away from one another and the terminations are relatively distant. All other Lyramula species observed in this stratigraphic section are smaller andeasily distinguished from L. simplex.
In specimens of Lyramula simplex var. spinosa, thespine is located where the two limbs meet at an angle.
Specimens of Lyramula simplex var. simplex bear asmooth curve (which is more characteristic) and do nothave a spine. L. simplex var. spinosa may provide a clue
to the rules of silicoflagellate skeletal design. McCartney and Loper (1989; see also McCartney et al., 1994),
in their optimization modeling of silicoflagellate skeletal
design, commented on general rules for silicoflagellates,
where angular intersections nearly always comprise threeelements. This is also observed in the corners of silicoflagellate basal rings, where rounded corners lack spines, but

39

less rounded corners will bear a spine.
The presence of bulbs in Lyramula simplex var. inflata
is more unusual and difficult to explain in silicoflagellatemorphology. Expansions or inflation of basal or apicalstrut attachments were reported by Deflandre (1933) and
Ichikawa et al. (1964) for Dictyocha and Distephanus.
After considering several possible explanations for thesestructures, Deflandre (1933) concluded that the most reasonable hypothesis for these “encystments” was a parasite, perhaps feeding on the material in the hollow canalsof the skeletal interiors. Similar expansion or inflation of
strut attachment areas were observed within specimens ofCorbisema archangelskiana in the lower part of the Horton River section (McCartney et al., 2011b).
Bulbous corners of the silicoflagellate skeleton distinguish the unusual Eocene genus Hannaites Mandra(1968), Mesocena oamaruensis (Martini and Müller,1976) and M. nodulifera (Tsumura, 1963). It remains to
be determined whether these occurrences are correlated
in any way to the perturbations in the silica cycle reported for the Eocene (McGowan, 1989; Muttoni and Kent,2007). Other unusual silicoflagellate taxa of comparable
age include extremely large Dictyocha grandis (Shaw &Ciesielski, 1983; McCartney & Harwood, 1992) associated with the Middle Eocene Climatic Optimum (MECOof Bohaty & Zachos, 2003; Witkowski et al., 2008).
The distribution of Lyramula simplex may provide
some clues to the occurrence of this variable morphology.
This taxon is known from marine sections representing
neritic and interior basin environments in Russia, California and Arctic Canada, but it is rare to absent in oceanic settings such as DSDP Sites 216, 275 (Bukry, 1975;
Hajós and Stradner, 1975; Perch-Nielsen, 1975) and Alpha Ridge in the Arctic Ocean (Ling et al., 1983; Bukry,
1981, 1985), and shallow-water neritic sections on Devon
Island, Arctic Canada (McCartney et al., 2011a). Thissuggests a higher abundance of this taxon in neritic andcoastal environments, where its morphological variation
and abundance may have been influenced by terrestrial
run-off, lower salinity, and nutrients.
Other evidence of environmental stress at the time ofdeposition is the occurrence of teratoid skeletons of L.
simplex, which were more abundant than for other Lyramula species. Two examples of distorted specimens areshown on Plate 1, Figures 12 and 14. High variability ofsilicoflagellate morphological elements, and the presenceof teratoid skeletons were suggested to have been associated with low salinity environments by Frenguelli (1935),
Dumitricǎ (1973) and Shitanaka (1983), among others.
Thomas et al. (1980) showed that distorted or incomplete
skeletons can result from growth in culture media that
contain heavy metals. However, distorted skeletons areuncommon among silicoflagellates in general, suggestingthat L. simplex may be more susceptible to such stress.
5. Conclusions
The presence of either a small spine or an inflated area or‘bulb’ at the central angle of L. simplex is interpreted toresult from this taxon’s response to variable environmen-

40

McCartney, Harwood, Witkowski

tal conditions. Other features of this taxon are consistentin most specimens, suggesting the presence of a spine or‘bulb’ results from environmental influences rather than
genetic differences. Future studies may identify this variability as a useful tool to infer events of greater fluvial
input into coastal and neritic settings. Future detailed
studies of Cretaceous sediments from Arctic Canada may
reveal a stratigraphic or paleobiogeographic correlationthat would improve their potential value in chronostratigraphic division of the Upper Cretaceous, or in paleoecological reconstructions.
Acknowledgements
The materials used for this study were part of a Master’s
Thesis by P.M. Tapia completed at the University of Nebraska - Lincoln (UNL). Financial support was provided
by the National Science Foundation grant OPP-9158075
to D.M. Harwood. We thank D. McNeil (Geological
Survey of Canada) who furnished the Canadian Arctic
Cretaceous samples. Diane Winter provided constructive comments on an early version of this manuscript
and Sherwood Wise, Jr. provided additional comments in
peer-review.
References
Bohaty, S.M. & Zachos, J.C. 2003. Significant Southern
Ocean warming event in the late middle Eocene. Geology, 31: 1017-1020.
Bukry, D. 1974. Coccolith and silicoflagellate stratigraphy, eastern Indian Ocean, Deep Sea Drilling Project Leg 22. In: C. C. von der Borch et al. (Eds.). Init.
Repts. DSDP, 22: 601-607.
Bukry, D. 1975. Silicoflagellate and coccolith stratigraphy, Deep Sea Drilling Project Leg 29. In: J. P. Kennett
et al. (Eds.). Init. Repts. DSDP, 29: 845-872.
Bukry, D. 1981. Cretaceous Arctic silicoflagellates. GeoMarine Letters, 1: 57-63.
Bukry, D. 1985. Correlation of late Cretaceous Arctic
silicoflagellates from Alpha Ridge. In H. R. Jackson
et al (eds.), Initial Geological Report on CESAR - theCanadian Expedition to Study the Alpha Ridge, Arctic Ocean. Geological Survey of Canada, Paper 84-22:
125-135.
Deflandre, G. 1933, Formations énigmatiques dusquekette chez quelques Silicoflagellés. Bulletin de laSociété Botanique de France, 80: 809-814, pl. 9, 10.
Dumitricǎ, P. 1973. Miocene and Quaternary silicoflagellates in sediments from the Mediterranean Sea.
In: Ryan, W. B. F., Hsü, K.J., et al. (Eds.). Init. Repts.
DSDP, 13: 902-933.
Frenguelli, J. 1935. Variaciones de Dictyocha fibula en el
Golfo de San Matias. Annales del Museo Argentino deCiencias Naturales, 38: 263-381.
Gleser, Z.I. 1966. Silicoflagellatophycaea. In Gollerbakh,
M. M. (Ed.), Cryptogamic Plants of the U.S.S.R. (Vol.
7). V. A. Komarova Botanical Institute, 1-363. (Translated from Russian by Israel Program for Scientific
Translations Ltd, Jerusalem, 1970.)
Hajós, M. & Stradner, H. 1975. Late Cretaceous archaeo-monads, diatomaceae, and silicoflagellata from thesouth Pacific Ocean, Deep Sea Drilling Project, Leg
29, Site 275. In: J.P. Kennett et al. (Eds.). Init. Repts.
DSDP, 29: 913-1010.
Hanna, G D. 1928. Silicoflagellata from the Cretaceous of
California. Journal of Paleontology, 1: 259-263.
Harwood, D.M. 1988. Upper Cretaceous and lower Paleocene diatom and silicoflagellate biostratigraphy of
Seymour Island, Eastern Antarctic Peninsula. In: R.
Feldmann & M.D. Woodburne (Eds.). Geology andPaleontology of Seymour Island. Geological Societyof America Memoir. 169: 55-129.
Ichikawa, W., Fuji, N. & Bachmann, A. 1964. Microfossils found from Noto, Japan. Sci. Rep. Kanazawa
Univ., 9: 25-118.
Jousé, A.P. 1949. Novye diatomovye I kremnevye zhgutikovye vodorosli verkhnemelovogo vozrasta iz glinistykh peskov basseina reki Bol’shoi Aktai (vostochnyi
sklon Severnogo Urala) (New Diatoms and Silicoflagellates from Upper Cretaceous Argillaceous Sands of
the Basin of Bol’shoi Aktai River [Eastern Slope of
the Northern Urals]). Botanicheskie Materialy Otdela
Sporovykh Rastenii Botanicheskogo Instituta SSSR,
6: 65-78.
Jousé, A.P. 1951. Diatomaceae et silicoflaggellatae aetatis supernecretaceae ex arenis argillaceis systematis
fluminis Bolschoy Aktay in declivitate oreintali Ural
Borealis. Otdela Sporovykh Rastenii, Botanischeskii
Institut, Akademia Nauk SSSR. 10: 72-76 (in Russian).
Ling, H.-L., McPherson, L.M. & Clark, D.L. 1973. Late
Cretaceous (Maastrichtian?) silicoflagellates from theAlpha Cordillera of the Arctic Ocean. Science 180:
1360-1361.
Mandra, Y.T. 1968. Silicoflagellates from the Cretaceous,
Eocene and Miocene of California, U.S.A. California
Academy of Sciences, Proceedings, 36: 231-277.
Martini, E. & Müller, C. 1976. Eocene to Pleistocene
silicoflagellates from the Norwegian-Greenland Sea(DSDP Leg 38). In: Talwani, M. et al. (Eds.). Init.
Repts. DSDP, 38: 857-895.
McCartney, K. & Harwood, D.M. 1992. Silicoflagellates
from Leg 120 on the Kerguelen Plateau, Southeast
Indian Ocean. In: Wise, S.W., Jr., Schlich, R., et al.
(Eds.). Proc. ODP, Sci. Results, 120: 811-831.
McCartney, K. & Loper, D.E. 1989. Mathematical modeling of Dictyocha and Distephanus skeletal morphology, Paleobiology, 15: 283-298.
McCartney, K., Loper, D.E. & Ernissee, J. 1994. Mathematical modeling of silicoflagellate skeletal morphology and implications concerning skeletal latticeworks.
Proceedings of the XIth International Symposium on
Living and Fossil Diatoms, Memoirs of the California
Academy of Sciences, Number 17: 87-94.
McCartney, K., Witkowski, J. & Harwood, D.M. 2011a.
Unusual early assemblages of Upper Cretaceous silicoflagellates from the Canadian Archipelago. Revuede Micropaléontologie, 54: 31-58.
McCartney, K., Witkowski, J. & Harwood, D.M. 2011b.
Upper Cretaceous silicoflagellate taxonomy andUnusual examples of the silicoflagellate Lyramula simplex

biostratigraphy of Horton River, Nunavut, Canada.
Micropaleontology, 57: 61-86.
McGowan, B. 1989. Silica burp in the Eocene ocean.
Geology, 17: 857-860.
Muttoni, G. & Kent, D.V. 2007. Widespread formation ofcherts during the early Eocene climatic optimum. Palaeogeography, Palaeclimatology, Palaeecology, 253:348-362.
Perch-Nielsen, K. 1975. Late Cretaceous to Pleistocene
silicoflagellates from the southern southwest Pacific,
DSDP, Leg 29. In: J.P. Kennett et al. (Eds.). Init.
Repts. DSDP, 29: 677-721.
Shaw, C.A. & Ciesielski, P.F. 1983. Silicoflagellate biostratigraphy of middle Eocene to Holocenesubantarctic sediments recovered by Deep Sea Drilling Project
Leg 71. In: Ludwig, W.J., Krasheninnikov, V.A., et al.
(Eds.). Init. Repts. DSDP, 71: 687-737.
Shitanaka, M. 1983. Silicoflagellate remains in the sediments of Lake Hiruga, Fukui, Japan. Bulletin of the
Mizunami Fossil Museum, N: 171-180 (in Japanese).
Tapia, P.M. & Harwood, D.M. 2002. Upper Cretaceous
diatom biostratigraphy of the Arctic archipelago andnorthern continental margin, Canada. Micropaleontology, 48: 303-342.
Thomas, W.H., Hollibaugh, J.T & Seibert, D.L. 1980.
Effects of heavy metals on the morphology of somemarine phytoplankton. Phycologia, 19: 202-209.
Tsumura, K. 1963. A systematic study of silicoflagellateae.
Yokohama Municipal University., Journal C-45: 1-28.
Witkowski, J., Harwood, D.M. & Bohaty, S.M. 2008.
Middle Eocene silicoflagellate ‘monsters’: association of Dictyocha grandis Ciesielski & Shaw with
the MECO warming event. In: Strong, C.P., Crouch,
E.M., Hollis, C. (Eds.). Climatic and Biotic Events of
the Paleogene, 12-15 January 2009, Te Papa, Wellington, New Zealand, GNS Science Miscellaneous Series
16: 138.
Yorath, C.J., Balkwill, H.R. & Klassen, R.W. 1975. Geology of the eastern part of the Northern Interior andArctic Coastal Plains, Northwest Territories. Geological Survey of Canada, Paper 74-36: 1-35.

41