Plate 32, Figs. 1, 2, 5-7, 9-11
Holotype: Plate 32, Figure 1, 2
Paratype: Plate 32, Figure 9, 10

Type Locality: Speeton Bed C8B, early Hauterivian, regale ammonite Zone. Holotype: Slide topC8B(2), E.F. N44.1.
Paratype: Slide upperC8B(2), E.F. O53.4.

Derivation of Name: From the Latin crassus, thick, stout - in reference to the thick-walled endocyst.

Diagnosis: A small, suturocavate to camocavate species, subcircular in outline, with a thick, fibroperforate endocyst and a much thinner, microperforate pericyst. The degree of cavation is most pronounced around the cingulum and over the hypocyst, increasing towards the antapex. A small area of cavation may also be present at the apex. Poorly-defined tabulation is sometimes outlined by sutural folds but it may be absent. No clear sulcal groove is discernible. The archeopyle is apical with the operculum often retained.

Dimensions: Holotype: Length - 43 μm. Width - 41 μm.
Paratype: Length - 48 μm. Width - 35 μm.
Complete specimens: 48 (46) 43 μm × 43 (40) 35 μm.
Specimens Measured: 3.
Overall (operculum lost): 46 (40) 35 μm × 46 (42) 38 μm.
Specimens Measured: 5.

Remarks: Polygonifera crassa is a small but robust species, mainly characterised by the contrast between the thick endocyst and the delicate, microreticulate pericyst. It occurs between Speeton Beds C9A and C7H (early Hauterivian, upper regale to basal inversum ammonite Zones).