Thalassites morozakiensis T.Yamada

Plant Fossil Names Registry Number: PFN003624

Act LSID: urn:lsid:plantfossilnames.org:act:3624

Author: T. Yamada

Rank: species

Genus: Thalassites Benzecry et Brack-Hanes

Reference for this name: Yamada, T. (2025): Seagrass fossils from the lower Miocene Morozaki Group in Aichi Prefecture, central Japan. – Aquatic Botany 201: 103913.

Page of description: 2

Illustrations or figures: Figure 2A–C

Original diagnosis/description

Constricted, short and fibrous leaf sheaths persistent at the base of shoot.
The obtained shoot bears six leaves in distichous or decussate arrangement with short internodes (Fig. 2A). The shoot base displays a darker, striated zone (proximal to the arrowhead in Fig. 2B), distal to which is a region where veins are faintly visible (between the arrowhead and double arrowhead in Fig. 2B). The former corresponds to an older fibrous leaf sheath, while the latter represents the most recent sheath. The total sheath region measures 2.4 cm in length and 0.7 cm in width (Fig. 2B). The junction between the sheath and lamina is indis tinct, with no ligule present at the junction (Fig. 2B). The leaves lack a petiole and are entire, strap-shaped, measuring 4.0–7.0 cm in length and 1.0–1.5 cm in width (Fig. 2A). The leaf apex is rounded (Fig. 2A). Each leaf contains 20–26 parallel veins, with the midvein being slightly thicker than the others (Fig. 2A). The parallel veins are interconnected by cross veins that run perpendicular or slightly oblique to them (Fig. 2A). Small dots scattered across the epidermal cells likely represent tannin deposits (Fig. 2C).

Stratigraphy

Neogene, Miocene
in the lower part of the Toyohama Formation (Kondo and Kimura, 1987), Morozaki Group. The Toyohama Formation is estimated to be approximately 18.0–17.6 Ma in age, based on diatom, foraminiferal, and paleomagnetic data (Ito et al., 1999).

Locality

Japan
Toyohama Port in Minamichita Town, Aichi Prefecture