24 July, 2009


In my micropaleontological studies in the 1980’s I dealt with peridinioid dinoflagellates, as a morphologically defined group, from the Upper Cretaceous (Maastrichtian) of Trelleborg at the southwestern part of Scania (Skåne), southern Sweden. My intention was to contribute to the taxonomy of this group by describing the forms present, recording their dimensions, and analysing the relations in shape between endocyst and pericyst.

Fossil dinoflagellates that appear morphologically related to modern Peridinium and Protoperidinium were treated as peridinioid dinoflagellate cysts. Several types, styles, and shape variants of archeopyles were recognized in this group.

In peridiniacean genera as a rule the archeopyle corresponds to the second anterior intercalary paraplate (2a) and the inferred paratabulation is of the hexastyle.

Genera which reveal indications of a quadrastyle paratabulation or have intercalary archeopyles corresponding to more than one paraplate (e.g. Trithyrodinium) or combination archeopyles corresponding to paraplates of different series (e.g. Palaeoperidinium) were not included in the peridiniacean genera, but regarded as peridinioid.

In papers on dinoflagellates detailed recordings of dimensions of the material studied and calculations on those data were rarely presented. Before 1980 I found only three studies that used morphometry:

  • Regression analysis was used to study the relation between horns and cyst body
  • The distribution of length/width ratio was used to study the interspecific variation and taxonomy of Alterbia
  • Dimensions of length, width, and length of horns and spines were graphically presented in one paper

I have treated ten species of acid resistant peridinioid dinoflagellates of Deflandrea, Isabelidinium, Palaeoperidinium, Phelodinium, Subtilisphaera, Svalbardella, and Trithyrodinium from this Upper Cretaceous (Maastrichtian) material from southern Sweden.

Taxonomical conclusions

  • The discrimination between Isabelidinium Lentin & Williams (1977) and Eurydinium Stover & Evitt (1978) according to the diagnoses, by means of length/width ratio of the endocyst is not justified in my studies. This ratio displays a normal distribution which includes values which originally have been considered critical for the discrimination of two separate genera.
  • The features discriminating Isabelidinium Lentin & Williams (1977) and Chatangiella Vozzhennikova (1967) are not clearly indicated in the original descriptions. Most of the diagnostic differences may be modifications due to environmentally controlled factors. In preserved material those morphologic features seem to display ranges which include both genera. I have published the new combination Isabelidinium armatum (Cookson & Eisenack) Lindgren.
  • Lejeunia kozlowskii Górka (1963) is a cornucavate cyst referable to Phelodinium Stover & Evitt and different from Lejeunecysta tricuspis (Wetzel) Artzner & Dörhöfer (1978). I have published the new combination Phelodinium kozlowskii (Górka) Lindgren.
  • Palaeocystodinium Alberti (1961) is a later synonym of Svalbardella Manum (1960). So is Cystodiniopsis Vozzhennikova (1963) which name however is illegitimate; the designation of a new type species is contrary to the ICBN.
  • Ceratiopsis Vozzhennikova (1967) and Pentagonum Vozzhennikova (1967) as names of dinoflagellate genera are illegitimate and must be rejected, as they are later homonyms of Ceratiopsis De Wildeman (1896) and Pentagonium Schauer (1843), which were validly published for a genus of fungi and an asclepiadacean genus, respectively.


Lindgren, S., 1984.
Acid resistant peridinioid dinoflagellates from the Maastrichtian of Trelleborg, southern Sweden. (Summary in Russian.) Stockholm Contrib. Geol., 39(6): 145—201. Stockholm. ISSN 0585-3532. ISBN 91-22-00519-6. — Buy at the lowest prices among books in Sweden.
Lindgren, S., 1985.
Nomenclatural notes on fossil peridinioid dinoflagellates. Taxon, 34 (4): 670—671. Utrecht. ISSN 0040-0262.

Web Links

Dinoflagellates; by Matthew Olney, University College, London.

Dinoflagellates; by Mona Hoppenrath and Juan F. Saldarriaga, Forschungsinstitut Senckenberg, Germany, and University of British Columbia, Canada

Introduction to the Dinoflagellata; by Graham Williams & Andrew MacRae, Museum of Paleontology, University of California, Berkeley.

Peridinium; by Charles J. O’Kelly, Protist Image Database.

Graham Williams, Dartmouth, 1996

Charles Downie, Sheffield, 1923—1999

Bill Sarjeant, Saskatoon, 1935—2002; also in The Encyclopedia of Saskatchewan.

Lewis Stover, Kerrville, 1925—1993

Tamara Vozzhennikova, Novosibirsk, 1914—2000

Morphometry of peridinioid dinoflagellates

24 July, 2009

In peridinioid dinoflagellates of the Maastrichtian (Upper Cretaceous) of Trelleborg (Scania, southern Sweden) analyses of the length/width ratio of the pericysts and the endocysts of different species also indicate that the variation of the pericysts generally is greater than that of the endocysts. The endocysts display a less elongated shape which is fairly constant within a species. The specific mean values of the length/width ratio of endocysts range between 0.8 and 1.4 with the median value = 1.0, while the specific mean values for the pericysts range from 1.3 to 4.5, with the median value = 2.1

In these peridinioid dinoflagellates the restricted variation in size and shape of the endocysts indicates that the endophragm was developed under strong genetic control inside the motile, vegetative theca. The pericysts, however, display a wide morphologic variation which may be the result of influences by environmentally controlled factors during the development of the periphragm. This development may have taken place also on the outer side of the motile theca, or even after its decay.

Analyses of the Trelleborg material of the length/width ratio of pericysts and endocysts by reduced major axis in scatter diagrams indicate that within a genus the slopes of the regression lines are close to each other within a genus with statistically significant correlation coefficients. Thus the slope of the regression lines may be used for taxonomical purposes.

See also >> Dinoflagellater: mätningar och klassifikation (in Swedish only)

Dinoflagellater: mätningar och klassifikation

24 July, 2009


Dinoflagellater är en grupp encelliga, mikroskopiska alger som kan variera kraftigt till utseendet. Dinoflagellaterna är kända från silur men förekommer främst från mellersta mesozoikum. De är i nutiden en viktig del av havens plankton men lever även i sötvatten.Dinoflagellaternas livscykel har två stadier: det vegetativa stadiet med en theca och ett vilstadium med en cysta. I thecastadiet är cellen aktivt rörlig och omges av ett cellulosaskal. I vilstadiet bildar cellen som skydd mot ogynnsamma miljöförhållanden ett hölje innanför thecan och omkring plasman. Cystan är orörlig.
Hos levande dinoflagellater är det främst theca-stadiet som studerats. Inom paleontologin är det vilstadiet som är intressant eftersom endast cystorna bevaras som fossil.
Eftersom cystan bildas innanför thecans vägg och eftersom båda är kontrollerade av samma genotyp är det naturligt att de kan uppvisa betydande likheter så att cystan motsvarar thecans morfologi. Cystornas form kan variera kraftigt. De kan vara sfäriska och släta, men de har ofta olika slags utskott. Flera former är tillplattade. Peridinioida dinoflagellater är tillplattade och försedda med horn (figur 1). Cystans vägg kan ha varierande uppbyggnad och bestå av ett eller två (eventuellt tre) lager. Den yttre väggen benämns pericyst och den inre väggen endocyst.
  figur 1






Figure 1. Peridinioid dinoflagellate with pericyst and endocyst.

Analyser av längden och längd/bredd-kvoten hos pericysten och endocysten av olika arter visar att pericystens variation i allmänhet är större än endocystens. Endocysten har en mindre långsträckt form som är tämligen konstant inom en art (figur 2). Medelvärdet för längd/bredd-kvoten för endocysten varierar för de arter jag undersökt mellan 0.8 och 1.4 med medianvärdet = 1.0, medan medelvärdet för längd/bredd-kvoten för pericysten varierar mellan 1.3 och 4.5, med medianvärdet = 2.1

figur 2

















Figure 2. Peridinioid dinoflagellate Deflandrea diebeli. Distribution of length (L) and length/width ratio (L/W) of endocyst (E) and pericycst (P). n = number of specimens.


En ändring av cystans form mellan olika stratigrafiska nivåer kan visa på ett utvecklingsförlopp som orsakar en morfologisk förändring av fenotypen (figur 3).

 figur 3












Figure 3. Peridinioid dinoflagellate Paleoperidinium pyrophorum. Scatter diagrams with regression line showing cyst length (L) to cyst width (W) in two different samples. The slope (m), correlation coefficient (r), and number of specimens (n) are recorded on the figure. The correlation betweenL and W is statistically significant on the 0.1% level


Förhållandet mellan formen hos pericysten och endocysten är relativt konstant inom ett släkte men varierar mellan olika släkten (figur 4 och figur 5).

 figur 4



















Figure 4. Peridinioid dinoflagellates Deflandrea diebeli and Isabelidinium cooksoniae. Scatter diagrams with regression line showing length/width ratio of pericysts (L/W P) to length/width ratio of endocysts /L/W E). The slope (m), correlation coefficient (r), and number of specimens (n) are recorded on the figure. The correlation between L/W P and L/W E is statistically significant on the 0.1 % level.

 figur 5_750

Figure 5. Regression lines based on reduced majoraxis in scatter diagrams showing length/width ratio of pericysts (P) to length/width ratio of endocysts (E) for species of peridinioid dinoflagellates of genera Deflandrea, Isabelidinium, Subtilisphaera, and Trithyrodinium from the Trelleborg boring core T-1 (southern Sweden). The slope (m), correlation coefficient (r) and its significance level (* = 5 %, ** = 1 %, *** = 0.1 %), and number of specimens (n) are recorded on the figure.


Den begränsade variationen av storleken och formen hos endocysten av de studerade dinoflagellaterna visar att den inre väggen utvecklades under genetisk kontroll inuti en theca. Pericysten visar en vid morfologisk variation som kan vara resultat av påverkan av miljöfaktorer under den yttre väggens utveckling.

De båda släktena Isabelidinium och Eurydinium skiljs genom formen hos endocysten. I Isabelidinium skall längden av endocysten vara lika stor som eller mindre än bredden (L/W<1.0) medan i Eurydinium skall längden av endocysten vara större än bredden (L/W>1.0).

 figur 6









Figure 6. Peridinioid dinoflagellate Isabelidinium cooksoniae. Distribution of length (L) and length/width ratio (L/W) of endocyst (blank) and pericycst (dotted). n = number of specimens.


I det material jag studerat varierar längd/bredd-kvoten hos en art mellan 0.6 och 1.2. Kvoten är normalfördelad och har medelvärdet = 0.9 (figur 6). Detta visar att det inte finns någon anledning att särskilja dessa två släkten med endocystens form som kriterium.



Lindgren, S., 1984.
Acid resistant peridinioid dinoflagellates from the Maastrichtian of Trelleborg, southern Sweden. (Summary in Russian.) Stockholm Contrib. Geol., 39(6): 145—201. Stockholm. ISSN 0585-3532. ISBN 91-22-00519-6. — Buy at the lowest prices among books in Sweden.