(3129) Proposal to conserve the name <i>Lithodinia jurassica</i> var. <i>ornata</i> ( <i>Ctenidodinium ornatum</i> ) ( <i>Dinophyceae</i> ) with a conserved type

(3129) Ctenidodinium ornatum (Eisenack) Deflandre in Trav. Sta. Zool. Wimereux 13: 181. 1938 ≡ Lithodinia jurassica var. ornata Eisenack in Z. Geschiebeforschung 11: 176. 1935, nom. cons. prop. Typus: Sample at 239.20 m in a borehole drilled at Nettleton Bottom Quarry, south of Caistor, Lincolnshire, eastern England, 53.467222°, −0.304000°, Ampthill Clay Formation, Middle Oxfordian, Cardioceras tenuiserratum ammonite zone (British Geol. Surv. figured specimen No. MPK 4059); [illustrated in] Proc. Yorkshire Geol. Soc. 46: 246, fig. 9.15. 1987, typ. cons. prop. Alfred Eisenack (in Z. Geschiebeforschung 11: 176, t. 4, figs. 9–10. 1935) introduced the dinoflagellate cyst variety Lithodinia jurassica var. ornata, describing it as follows: “Die seltener auftretenden, starke Kammleisten besitzenden Formen werden als L. jurassica var. ornata bezeichnet. Es gibt solche mit feinerer und solche mit gröberer Zähnelung der Leisten (Taf. 4 Fig. 9–10). Dem gezeichneten Exemplar kommt folgendes Täfelungsschema zu: 4 ap + 5 pr + ? g + 5 pst + 1 p + 1 at. Der Apex ist durch ein Apextäfelchen verschlossen (Abb. 1–4).” (The less common forms with strong crests are called L. jurassica var. ornata. There are those with finer and those with coarser serration of the ridges (pl. 4, figs. 9–10). The example drawn [in the text-figures] has the following tabulation: 4 ap + 5 pr + ? g + 5 pst + 1 p + 1 at. The apex is closed by an apical plate (figs. 1–4).) Eisenack (l.c. 1935) illustrated two specimens, one at two focal levels (his t. 4, figs. 9a, b) and the other with just one photograph (t. 4, fig. 10). Eisenack (l.c. 1935) did not indicate a type, but such a designation was not required until 1958 (ICN Art. 40.1; Turland & al. in Regnum Veg. 162. 2025). Eisenack (in Ann. Protistol. 5: 61, t. IV, figs. 5, 6a, 6b & text-figs. 1–4. 1936) also described and illustrated Lithodinia jurassica var. ornata, using the same illustrations as in the protologue, but again did not designate a type. Eisenack (l.c. 1935) used the term “die Gonyaulacaceen” in relation to Lithodinia jurassica var. ornata, which reflects the “botanical” family name Gonyaulacaceae Lindemann. Thus, it seems reasonable to assume that Eisenack (l.c. 1935) was using botanical nomenclature. Deflandre (in Trav. Sta. Zool. Wimereux 13: 181. 1938) raised this taxon to species rank and transferred it to his new genus Ctenidodinium, as C. ornatum (Eisenack) Deflandre, designating it as type of the genus name. Deflandre (l.c: t. IX, figs. 1–7) illustrated several new specimens, among which he designated a “plésiotype” (l.c.: t. IX, figs. 1–2) and several paratypes (l.c.: t. IX, figs. 3–7). The term plesiotype is used neither in the current ICN nor in the current version of the International Code for Zoological Nomenclature (https://www.iczn.org/the-code/the-code-online/). Several definitions of the term plesiotype can be found online: for example, “A specimen used for any redescription, supplementary description, or figure published by any author after the original description of the species” (https://essigdb.berkeley.edu/admin/types.html). From the online definitions clearly the term was used historically to supplement formal definitions, and so it seems that Deflandre (l.c.) did not intend the specimen he labelled as a plesiotype to be considered the type of the species name. Nor did he identify any other specimen as the type of C. ornatum. Nevertheless, significantly, it was from these illustrations that future concepts of C. ornatum arose. Eisenack (Katalog Foss. Dinoflagellaten, Hystrichosphären 1: 157. 1964) finally designated a “Holotypus” for Ctenidodinium ornatum as Eisenack 1935, t. 4, fig. 9 (actually two photographs, figs. 9a, b, of the same specimen), the specimen of which thus became the lectotype as it was designated from the original material subsequent to the protologue (Art. 9.10, 9.11). That specimen, then, is also the type of the genus Ctenidodinium (Art. 10.1). The two specimens illustrated in the protologue would now be considered separate species through broad current consensus and usage—that shown in Eisenack (l.c. 1935: t. 4, figs. 9a–b and text-figs. 3–4) being attributable to Ctenidodinium continuum Gocht, and that shown in Eisenack (l.c. 1935: t. 4, fig. 10 and text-figs. 1–2) being attributable to C. ornatum. Unfortunately, the morphology of the lectotype, as designated by Eisenack (l.c. 1964) matches that of C. continuum, as described by Gocht (in Palaeontographica, Abt. B, Paläophytol. 129: 141–142, t. 32, fig. 15. 1970). Strictly following the ICN and current taxonomic concepts, C. ornatum would be used in the sense of C. continuum as currently conceived and the name C. continuum would be a heterotypic junior synonym of C. ornatum. The concept circumscribed by the currently understood morphology of C. ornatum would require a new species name. This would be very disruptive, altering the concept of the type of the genus name and hence the much-used species names Ctenidodinium ornatum and C. continuum. Searching on Google Scholar (on 1 Oct 2025) for “Ctenidodinium” and “ornatum” yielded 237 search results. A similar search on “Ctenidodinium” and “continuum” returned 184 search results. Palynodata (see White & al. in Palynology 33(2): 157–174. 2009) is a useful database in checking nomenclature and taxonomic revisions for palynologists (Gravendyck & al. in Palynology 46: 1–11. 2022). Palynodata (on 28 Apr 2025) contains 164 records of Ctenidodinium ornatum observed from separate publications and with an age range that the authors consider in place (10 others probably represent contamination or misidentification). Both species, using current concepts, have been used extensively as biostratigraphic markers, determining ages used in applied and commercial studies. Throughout northwestern Europe and neighbouring regions, C. ornatum (“sensu Deflandre, l.c.”) ranges from the earliest Bathonian to the middle Oxfordian (Riding in Proc. Yorkshire Geol. Soc. 46: 231–266. 1987, and in Palynology 29: 87–142. 2005; Riding & Thomas in Scott. J. Geol. 33: 59–74. 1997; Wiggan & al. in Rev. Palaeobot. Palynol. 238: 55–87. 2017). In Europe and adjacent regions in Laurasia, C. continuum ranges from the late Bajocian to the Callovian/Oxfordian transition (Riding & Thomas, l.c. 1997; Riding & al. in Contr. Ser. Amer. Assoc. Stratigr. Palynologists 36: 1–179. 1999; Riding, l.c. 2005; Wiggan & al., l.c.). Other significant studies in which both species are cited include: Woollam & Riding, Rep. Inst. Geol. Sci. 83/2. 1983; Feist-Burkhardt & Wille in Cah. Micropaléontol., n.s., 7: 141–163. 1992; Riding & Thomas in Powell, Stratigraph. Index Dinoflagellate Cysts, Brit. Micropalaeontol. Soc. 1992; Poulsen & Riding in Geol. Denmark Greenland Surv. Bull. 1: 115–144. 2003; Riding, l.c. 2005; Borges & al. in Rev. Palaeobot. Palynol. 170: 40–56. 2012; Hssaida & al. in Ann. Paléontol. 103: 197–215. 2017). Because of the great potential disruption, especially beyond systematics, we propose the conservation of Ctenidodinium ornatum and its basionym Lithodinia jurassica var. ornata with a conserved type. Proposing the other specimen illustrated by Eisenack (l.c.: 1964: t. 4, fig. 10) as the conserved type would not be ideal in our view. Its illustration is a small high-contrast photograph and shows insufficient morphological detail to confirm its identity. We have attempted to access the type material, but Dr. Ingmar Werneberg, Kustos der Paläontologischen Sammlungen (Curator of Palaeontology Collections) at Senckenberg Centre for Human Evolution and Palaeoenvironment, Tübingen, Germany, informs us that the collection containing Eisenack's materials is in “horrible condition” and that a search for specific specimens would be impractical. There is a high chance that the type specimen is lost and, even if not, the poor condition typical for such old types makes them so uninformative (see discussion in Gravendyck & al. in Palynology 45: 717–743. 2021) that it usually renders them “destroyed” in the sense of Art. 9.16. One alternative would be to propose the specimen illustrated by Deflandre (l.c.: t. IX, figs. 1–2) as a conserved type; this specimen was influential in the development of the current concept of C. ornatum. However, after correspondence with Dr. Marie-Béatrice Forel at the Muséum national d'Histoire naturelle in Paris, it proved impractical to view the specimen. Hence, we choose as conserved type a specimen curated and easily accessible at the British Geological Survey, originally figured in Riding (l.c. 1987: 246, fig. 9.15) and refigured here as Figs. 1A–D. The acceptance of this specimen as conserved type would retain the current concept of Ctenidodinium ornatum and would also avert the designation of C. continuum as a heterotypic junior synonym of C. ornatum and hence not lose the current concept and important stratigraphic usage of that species; in so doing, it would avoid disadvantageous nomenclatural changes as well as averting confusion in non-taxonomic uses of the two species. We thank Susanne Feist-Burkhardt for discussion and Ingmar Werneberg of Senckenberg Centre for Human Evolution and Palaeoenvironment, Tübingen, Germany, for assistance in trying to locate the relevant type material. Additionally we thank Graham Williams for his internal GSC review of the manuscript, Marie-Béatrice Forel at the Muséum national d'Histoire naturelle in Paris for help with locating Georges Deflandre's original material, and Jan Hennison at the British Geological Survey for photographing the proposed conserved type. JBR publishes with the approval of the Director, British Geological Survey (NERC).

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