Back
Pareodinia tripartita var. rotunda
Pareodinia tripartita "var. rotunda" Johnson and Hills, 1973, p.209, pl.3, figs.1–2; text-fig.11C. Holotype: Johnson and Hills, 1973, pl.3, fig.2. Originally Pareodinia tripartita var. rotunda, subsequently Pareodinia tripartita subsp. rotunda, thirdly Evansia tripartita subsp. rotunda. Taxonomic senior synonym (at specific rank): Tenua (as Pareodinia, now Evansia) evittii, according to Wiggins (1975, p.105) and Below (1990, p.73). Age: late Bathonian.
Original description (Johson and Hills, 1973)
Description:
Cysts of P. tripartitus having circular outlines surmounted by a short apical rounded horn. Archeopyle observed infrequently.
Dimensions: (10 specimens) Over-all length 48-55 µm, width 40-46 µm, apical horn 5-8 µm.
Holotype: P-7-39 1/5 93/8/33; Paratype P-7-37 1/5 100/34.6
Distribution: As for species.
Remarks:
This species is distinguished from others of the genus primarily by its archeopyle, which forms by loss of 3 intercalary plates. At Vantage Point all three varieties appear immediately above the Arctocephalites Bed (Middle Bathonian). P. tripartitus var. rotundus was found only in the lower 30 ft of the range of the species, although round forms with longer horns resembling the horns of the other two varieties do occur rarely within the superjacent 50 ft. P. tripartitus var. obtusus terminates at 850 ft, 25 ft below the Lower Cadoceras Bed (Lower Callovian). P. tripartitus persists to 1050 ft, 80 ft below the Upper Cadoceras Bed (Lower Callovian); however, only 6 specimens were seen in the samples above the Lower Cadoceras Bed. It is believed that these latter 6 specimens are reworked.
Original description (Johson and Hills, 1973)
Description:
Cysts of P. tripartitus having circular outlines surmounted by a short apical rounded horn. Archeopyle observed infrequently.
Dimensions: (10 specimens) Over-all length 48-55 µm, width 40-46 µm, apical horn 5-8 µm.
Holotype: P-7-39 1/5 93/8/33; Paratype P-7-37 1/5 100/34.6
Distribution: As for species.
Remarks:
This species is distinguished from others of the genus primarily by its archeopyle, which forms by loss of 3 intercalary plates. At Vantage Point all three varieties appear immediately above the Arctocephalites Bed (Middle Bathonian). P. tripartitus var. rotundus was found only in the lower 30 ft of the range of the species, although round forms with longer horns resembling the horns of the other two varieties do occur rarely within the superjacent 50 ft. P. tripartitus var. obtusus terminates at 850 ft, 25 ft below the Lower Cadoceras Bed (Lower Callovian). P. tripartitus persists to 1050 ft, 80 ft below the Upper Cadoceras Bed (Lower Callovian); however, only 6 specimens were seen in the samples above the Lower Cadoceras Bed. It is believed that these latter 6 specimens are reworked.