New goniodomacean dinoflagellates with a compound hypotractal archeopyle from the late Cenozoic: Capisocysta Warny and Wrenn, emend.

• Published in: Journal of Paleontology
• Main Author: Head, Martin J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1998
• Subjects: North Atlantic
• Online Access: http://dx.doi.org/10.1017/s0022336000027153; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000027153

Two new species of dinoflagellate are described from the upper Cenozoic of the North Atlantic region. They are assigned to the goniodomacean genus Capisocysta Warny and Wrenn, 1997 emend., whose archeopyle uniquely forms by the extensive and exclusive dissociation of hypocystal plates. Capisocysta lata new species is recorded from the upper lower Pliocene Coralline Crag Formation of eastern England, the lower and upper Pliocene of the subsurface Great Bahama Bank, and as a living cyst from Phosphorescence Bay, Puerto Rico. Capisocysta lyellii new species is reported from the Coralline Crag Formation of eastern England. Capisocysta provides the only unambiguous example of a hypocystal archeopyle in the order Gonyaulacales and the only example of a hypotractal archeopyle in the division Dinoflagellata. The spherical, proximate cysts have pre-formed lines of weakness that occur exclusively on the hypocyst, where they follow plate boundaries. Upon excystment, these sutures facilitate the separate release of plates 2–6″′, ps, 1p, and 1″″. Sulcal plates 1s and rs and postcingular plate 1″′ typically remain attached to the epicyst, forming a distinctive hyposulcal tab. The single antapical plate in C. lata is represented in C. lyellii by two plates (left and right first antapical homologues) that are released separately. Capisocysta has a tropical to warm temperate distribution today. It thrived and perhaps formed blooms in tropical carbonate platform environments of the Bahamas during the Pliocene, and might prove to be a useful indicator of very warm intervals within the Pliocene of higher latitude regions including the southern North Sea basin. To facilitate discussion of Capisocysta , several morphological terms have been modified or newly introduced. These terms more precisely describe archeopyle position and extent in dinoflagellates.