Keijella gonia Zhao & Whatley, 1989

Figs. 7A–E, 10

Keijella gonia Zhao & Whatley, 1989: 181, pl. 3 figs 7–10, 16.

Keijella gonia – Montenegro et al. 2004: pl. 1 fig. 8. — Forel 2021: 8, fig. 5h–i.

Dimensions

L = 0.380 –0.710 millimeters; H = 0.187 –0.380 millimeters; H/L = 0.49–0.62.

Distribution

Modern distribution: Mae Khlong River mouth, north west Gulf of Thailand (Montenegro et al. 2004); Sedili River, Jason Bay (Zhao & Whatley 1989); Central Vietnam (Tan et al. 2021); Indonesia (Fauzielly 2013); Southwestern coast of Peninsular Thailand, Ao Nun, Satun Province, Andaman Sea (Forel 2021).

Fossil distribution: Bangkok Clay (samples 20SS01B, 02A, 02B, 03A, 04A, 04B), whale excavation site, Samut Sakhon Province, Thailand, Late Holocene (this work, Fig. 4).

Remarks

Keijella gonia is easily recognized by the distinct angle formed by the posteroventral intersection of vertical and horizontal muri extending into a spine, sometimes sharp and long. The carapace is subrectangular in lateral view, strongly reticulated. Well-preserved specimens show laterally compressed anterior and posterior marginal denticles, especially along AVB. Prominent postero-marginal spines are distinct and located below the marginal denticles especially in juvenile specimens (Fig. 7A–C). Figure 10 shows H and L plots of K. gonia compared to the types from Malaysia (Zhao & Whatley 1989), the specimens from Thailand consist of adults and juveniles.