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Trinovantedinium henrietii

From Fensome et al., 2019:
Trinovantedinium henrietii Louwye et al., 2008, p.138,140, pl.4, figs.1–9.
Holotype: Louwye et al., pl.4, figs.1–5.
Age: Middle Miocene.

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Original description (Louwye et al., 2008):
Trinovantedinium henrietii sp. nov. (Plate 4, figs. 1–9)
Trinovantedinium sp. A, Louwye et al., 2007, text-figs. 4c, 6o–q.
Holotype. Plate 4, figs. 1–9. Slide 120-P1, sample U1318C-9X-3, 30–32 cm, 138.6 mbsf. England Finder reference D19/1, IRSNB catalogue number b5107. Locality: Porcupine Basin, offshore southwest Ireland. Age: Middle Miocene (Chron C5ABn, Serravallian).
Etymology. Named after Jean-Pierre Henriet (Renard Centre of Marine Geology, Ghent University, Belgium) who discovered the Belgica Mound Province in the Porcupine Basin.

Diagnosis. A large Trinovantedinium species with a distinctive apical horn and two antapical horns, a hyaline wall ornamented with solid, nontabular processes. Planar cingulum delineated by two rows of processes. Large steno-deltaform archeopyle with free operculum.

Description. Large dorsoventrally compressed cyst with a pentagonal outline. The sides of the epicyst are straight to slightly convex, and an apical horn is well-developed. The epicyst and hypocyst are of equal size with straight sides, and two almost symmetrical antapical horns. The thin bilayered wall is pale and hyaline, and is not easily stained. Endophragm and periphragm are closely appressed, except at the apex where a small apical pericoel is observed. The periphragm is smooth to scabrate and scattered with isolated, solid processes. The bases of the processes are widened, and they are distally flared or truncated. The length of the processes varies on an individual specimen, with a highest variation of 100%. Reconstruction of the process distribution is hindered by the thin and pale nature of the wall, but appears to be nontabular. The cyst is widest at the cingulum, which is well delineated by two rows of processes. The width of the cingulum varies between 5 and 8 µm. Lateral indentations are observed. The archeopyle is large and formed by the release of intercalary plate 2a with a steno-deltaform outline. The operculum is free.

Dimensions. Holotype: maximum length excluding processes: 98 µm; maximum width excluding processes: 75 µm; maximum length of processes: 7 µm. Range: total length excluding processes: 81(89)99 µm; width excluding processes: 61(75)84 µm, length of processes: 5(7)10. Number of specimens measured: 6.

Comparison. Erymnodinium? delectabile de Verteuil & Norris 1992 differs from Trinovantedinium henrietii sp. nov. by the continuous sutural crests and the distinctive reticulum formed by the periphragm. Trinovantedinium henrietiisp. nov. is easily distinguished from other species of Trinovantedinium by the characteristic processes and its large size.
Occurrence. Trinovantedinium henrietii sp. nov. has only been recorded from the Middle Miocene of the Porcupine Basin by Louwye et al. (2007) as Trinovantedinium sp. A. The species is almost continuously present throughout the Langhian and the earliest Serravallian. An isolated record was noted in the middle Serravallian (Text-Figure 3).
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