Fossil Record of Dinoflagellates

In this article, we will discuss Fossil Record of Dinoflagellates. So, let’s get started.

Fossil Record of Dinoflagellates

Dinoflagellates are preserved in the fossil record predominantly through their resting cysts. Micropaleontologists mainly focus on organic-walled cysts (i.e., consisting of a refractory biomacromolecule called
dinosporin, Fensome et al., 1993) but calcified cysts are increasingly recognized in tropical to temperate environments (Zonneveld et al., 2005). Siliceous skeletons are rare. Taphonomic processes that alter
dinocyst assemblages while sinking through the water column are relatively little known (Matthiessen et al., 2005), but species-selective aerobic degradation at the seafloor is an important process (Zonneveld
et al., 2008).

Fossil cysts first occurred in the Triassic with a subsequent major radiation from late Triassic to mid-Jurassic, but molecular biomarkers indicate that ancestors of dinoflagellates originated in the Proterozoic (Hackett et al., 2004). Species diversity was highest in the Cretaceous declining throughout the Cenozoic and followed the global sea level record with high diversity corresponding to intervals of high sea level and large shelf seas (Pross and Brinkhuis, 2005). To date more than 4,000 fossil cyst species have been described. Separate classification schemes have been developed by biologists and paleontologists for living dinoflagellates and fossil cysts before their natural relationship was discovered. Therefore, the resting cysts are often attributed to a different genus and species than their motile stage. Due to their nutritional strategies, dinoflagellates have been handled under the International Code either of Botanical or Zoological Nomenclature. Based on morphological characteristics, a phylogenetic classification at suprageneric level including both extant and fossil vegetative cells and cysts has been proposed by Fensome et al. (1993). Cyst species are generally described based on morphology, but molecular genetic studies
become increasingly important to unravel the intricate phylogenetic relationship between taxa difficult to distinguish by morphology (Matsuoka and Head, 2013 and references therein). The database dinoflaJ2 comprises the classification of fossil and living dinoflagellates down to the generic rank; an index of fossil dinoflagellates at generic, specific, and intraspecific rank; and the references of original descriptions (Fensome et al., 2008b).