Modern Dinocyst Key

Cyst of Protoperidinium lewisiae Mertens et al., 2015

Characteristics:
Spherical to subspherical brown cysts covered with numerous apiculocavate processes. Wall is microgranular. Process tips are acuminate, more or less evenly distributed. Process basis is ovoidal to spherical and carry many small spinulae. Archeopyle is therophylic probably situated along the cingulum.

Dimensions: Cyst body: 22.6 to 30.9 µm diameter, Process length: 2.8 to 8.1 µm, Process density: 8 to 20 processes 10 x 10 µm2.
Motile affinity: Protoperidinium lewisiae.
Stratigraphic range: Recent.

Comparison with other species:
Cysts most closely resemble cysts of Echinidinium granulatum in having a granulate cyst wall and processes that can bear numerous spinulae. However, processes of Cyst of Protoperidinium lewisiae are apiculocavate rather than hollow. Furthermore, the cyst wall is microgranulate rather than granulate as can be observed by E. granulatum.