Taxonomic Re-Investigation and Geochemical Characterization of Reid’s (1974) Species ofSpiniferitesfrom Holotype and Topotype Material

Abstract

The genus Spiniferites currently encompasses 142 dinoflagellate cyst species. Some Spiniferites species are difficult to identify because of an incomplete or doubtful description, and/or substandard iconography. This study re-describes and re-illustrates the Spiniferites holotypes first described by Reid in 1974. It also discusses topotype material from surface sediments recovered from British estuaries, and attempts to provide further constraints on the classification of species in this genus using the geochemical characterization of their cyst walls. Reid described four new Spiniferites species: Spiniferites belerius, Spiniferites delicatus, Spiniferites elongatus and Spiniferites lazus. New photomicrographs are presented here for the holotypes of Spiniferites delicatus and Spiniferites elongatus, and additional morphological observations based on newly processed topotype material are given. The geochemical characterization of the Spiniferites cyst walls showed overall consistency with a carbohydrate-based dinosporin. However, variability in the dinosporins suggests that, in this genus, the cyst wall composition may be species-specific. Analysis of the characteristic spectral regions for unclassified Spiniferites species showed that, in some cases, it may be possible to constrain the likely species affinity using the cyst wall chemistry. However, in most cases, the morphologically unspeciated cysts did not show sufficient similarity to an identified species' cyst wall chemistry to be more conclusive. This could either reflect an intermediate species that cannot be clearly characterized using morphology or dinosporin composition, or it represents a completely different species. In either case, both the morphological and geochemical evaluations highlight the difficulties in classifying species of this genus unequivocally.

Better molecular preservation of organic matter in an oxic than in a sulphidic depositional environment: evidence from of <i>Thalassiphora pelagica</i> (Dinoflagellata, Eocene) cysts

“…Bogus et al (2014) shows for all members of the Gonyaulacaceae (Lingulodinium, Spiniferites, Impagidinium, Protoceratium) a band C with weaker absorption than bands D and E). In Gurdebeke et al (2018), all members of the gonyaulacacean Spiniferites (except S. pachydermus which spectrum was taken from Bogus et al, 2014) 200 show a strong absorption near 1600 cm -1 in band C that exceeds the absorptions in band D. This we also see for T. pelagica which, considering the variability of this band in recent cysts, we consider intrinsic feature of the biopolymer. In band C recent gonyaulacacean cysts also show a shoulder near 1705 cm -1 , which is always of much smaller amplitude than the absorption 1590 cm-1.…”

“…Nevertheless, the T. pelagica cysts differ from 190 the fresh dinosporin of Lingulodinium in having relatively stronger absorptions by CH 2 , CH 3 and C=O are weaker absorption by C-O. Infra-red analysis of extant cysts of other members of this group of Gonyaulacoid dinoflagellate cysts show structural differences between the species (Bogus et al, 2014;Gurdebeke et al, 2018). Hence, the question arises to which part of the differences recorded between the spectra of these T. pelagica with other Gonyaulacoid taxa arises from differences in cyst biosynthesis and what part arises from post-mortem modification.…”

“…Within these groups there is considerable structural variation between the different species (Versteegh et al, 2012;Mertens et al, 2016;Mertens et al, 2015;Mertens et al, 2015;Bogus et al, 2014;Gurdebeke et al, 2018;Luo et al, 2018).…”

“…The molecular structure of the walls of extant organic dinoflagellate cysts, where known, may vary considerably between species (e.g. Mertens et al, 2016;Bogus et al, 2014;Gurdebeke et al, 2018). They all seem to consist of a carbohydratebackbone but with various contributions of proteinaceous material that appears to be species specific (Versteegh et al, 2012;Bogus et al, 2014).…”

Unique preservation of siliceous dinoflagellate motile cells from the Oligocene fossil Lagerstätte of Sieblos, Germany

“…; Gurdebeke et al . ). In contrast to motile thecate forms, the only functional sutures in the dinocyst wall are those associated with the pre‐determined excystment opening or archeopyle (Fensome et al .…”