A review of the Sentusidinium complex of dinoflagellate cysts

Abstract

15The Jurassic to Neogene (Miocene) dinoflagellate cyst genus Sentusidinium has a relatively 16 simple overall morphology. This genus, together with Batiacasphaera, Kallosphaeridium and 17 Pentafidia, comprises the Sentusidinium complex. This is distinct from the superficially similar 18 laterally asymmetrical and subspheroidal/lenticular Cyclonephelium complex. complex is clearly polyphyletic, and all three genera are in the order Gonyaulacales. However, 45Batiacasphaera and Pentafidia can not be confidently assigned to a family, whereas 46Kallosphaeridium and Sentusidinium are both in the family Gonyaulacaceae. The number of 47 species within the complex has been reduced to xxx to yyy; furthermore, all infraspecific taxa 48 have been eliminated. Introduction 54Many species of acavate, subspheroidal to lenticular, sexiform gonyaulacalean dinoflagellate 55 cysts (Fensome et al. 1993) with broadly apical archaeopyles, low-relief ornamentation and 56 generally no or very weak development of parasutures have been described from the Mesozoic 57 and Cenozoic. These can be divided into two groups, the Cyclonephelium complex and the 58Sentusidinium complex. The Sentusidinium complex is characterised by laterally symmetrical 59 cysts that belong to the family Gonyaulacaceae; this complex, which is the focus of the present 60 study, comprises the genera Barbatacysta, Batiacasphaera, Escharisphaeridia, 61 3 Kallosphaeridium, Pentafidia, Pilosidinium and Sentusidinium. The Cyclonephelium complex 62 consists typically of laterally asymmetrical, subspheroidal to lenticular cysts that belong to the 63 family Areoligeraceae; this complex is the focus of a separate ongoing study and includes the 64 genera Aptea, Canningia, Canninginopsis, Cerbia, Circulodinium, Cyclonephelium, 65 Senoniasphaera and Tenua. The genera Prolixosphaeridium, Bourkidinium and 66 Tanyosphaeridium are similar to Sentusidinium in having process-bearing cysts with apical 67 archaeopyles. However, all three genera have markedly elongate cyst bodies and generally 68 longer, nontabular processes. Consequently, we do not consider them in this paper. A brief history of the Sentusidinium complex 77The first genus to be described in the Sentusidinium complex was Kallosphaeridium, which was 78 established by de Coninck (1969) and emended by Jan du Chêne et al. (1985a). 79Kallosphaeridium comprises proximate cysts with a five-plate archaeopyle that can be 80 interpreted as apical (5A) or combination (4A1I); the operculum is attached ventrally. Drugg 81 (1970, p. 813) proposed Batiacasphaera for proximate cysts with "rod-shaped elements, either 82 separate or arranged to form a reticulum", and with an apical archaeopyle. This genus was later 83 emended by Morgan (1975) and Dörhöfer and Davies (1980) (see section 3). Sentusidinium was 84 erected by Sarjeant and Stover (1978) to contain proximate to proximochorate cysts with an 85 apical archaeopyle and bearing low-relief ornamentation. Psilate forms with apical archaeopyles, 86 in...

Palinotaxonomia da seção cretácea a neogena da Bacia de Pelotas, Brasil: cistos de dinoflagelados das ordens Ptychodiscales e Gonyaulacales

“…As identificações taxonômicas foram realizadas por meio da observação em microscópio óptico binocular ZEISS Imager.A2, em aumentos entre 200 e 1000 vezes. A sistemática completa incluindo descrições das espécies reconhecidas é apresentada segundo ordenamento de Fensome et al (1993), Wood et al (2016) e Williams et al (2017). Medições seguem o modelo apresentado na figura 2.…”

Additional new organic-walled dinoflagellate cysts from two onshore UK Chalk boreholes

“…The processes are also much more numerous on S. pilosum (Ehrenberg, 1854) Sarjeant and Stover, 1978 and which also have variable tips. Spine length is comparable on S. sahii (Khanna and Singh, 1981) Wood et al, 2016 andS. seperatum (McIntyre andBrideaux, 1980) Lentin and Williams, 1981 Description.…”

“…Sentusidinium aptiense (Burger, 1980a) Burger, 1980b possesses hollow tubular spines and S. capillatum (Davey, 1975) Lentin and Williams, 1981, S. echinatum (Gitmez and Sarjeant, 1972) Sarjeant and Stover, 1978and S? millepiedii (Jain and Millepied, 1975) Islam, 1993 Sarjeant and Stover, 1978 has a denser cover of short processes with variable tips that are also variable in S. rioultii Sarjeant, 1968, S. sahii (Khanna and Singh, 1981) Wood et al, 2016, S. sparsibarbatum Erkmen and Sarjeant, 1980and S. villersense (Sarjeant, 1968) Sarjeant and Stover, 1978. Sentusidinium separatum (McIntyre and Brideaux, 1980 Lentin and Williams, 1981 has bifid and branched process tips.…”

Discussion on ‘Middle Jurassic multi‐scale transgressive–regressive cycles: An example from the Lusitanian Basin’, by Magalhães et al., Depositional Record, 2023, 9(1), 174–202

“…adecta ( Gonyaulacysta adecta in Riding et al, 2022) and Pareodinia ceratophora , are more abundant in the Bathonian and Callovian, but may also occur through the Upper Jurassic, especially in the Oxfordian (Borges et al, 2011; Correia et al, 2019; Feist‐Burkhardt & Wille, 1992; Jan du Chêne et al, 1985; Riding & Thomas, 1992; Riding et al, 2022; Smelror, 2021). It is well established that Meiourogonyaulax and Sentusidinium occur from the Bajocian onwards, and various species span the later Mesozoic (Riding & Thomas, 1992; Smelror, 2021; Wood et al, 2016). The presence of these genera without species‐level recognition assessment indicates only that the section is no older than Bajocian.…”