Bairdia songthami Chitnarin, 2017

Chitnarin, Anisong, Crasquin, Sylvie, Forel, Marie-Béatrice & Tepnarong, Prachya, 2017, Ostracods (Crustacea) of the Early-Middle Permian (Cisarulian-Guadalupian) from Central Thailand (Indochina Block): Part II, Orders Podocopida, Platycopida and Myodocopida, Geodiversitas 39 (4), pp. 651-690 : 660

Bairdia songthami Chitnarin , n. sp.

( Figs 3 M-P; 6)

TYPE MATERIAL. — Holotype: one complete carapace (SUT-09- 2283, Fig.3M ); paratypes: two complete carapaces (SUT-09-2278, Fig. 3N and SUT-09-2284; Fig. 3P ).

ETYMOLOGY. — In honour of Dr Wichanet Songtham, Northeastern Institute of Petrified Wood and Mineral Resources, Nakhon Ratchasima Rajabhat University, Thailand.

MATERIAL EXAMINED. — Six complete carapaces.

DIMENSIONS. — H = 0.30-0.57 mm, L = 0.64-1.12 mm, H/L = 0.45-0.46, Holotype: H = 0.360 mm, L = 0.83 mm; Paratype ( Fig. 3N ): H = 0.47, L = 1.00; Paratype ( Fig. 3P ): H = 0.57 mm, L = 1.23 mm ( Fig. 6 ).

TYPE HORIZON. — Sample 07LB05-2, Ta Kli section, Tak Fa Formation, Middle Permian.

TYPE LOCALITY. — Ta Kli section (15°19’05’’N, 100°22’46’’E), Nakhon Sawan Province, central Thailand.

OCCURRENCES. — Sample 07 PB03-1 , Khao Kana section, Pha Nok Khao Formation, Phetchabun Province, Early Permian ; sample 07 PB05-6 , Ban Naen Sawan I section, Tak Fa Formation, Phetchabun Province, Middle Permian ; samples 07LB05-2 and 07LB05-A2, Ta Kli section, Tak Fa Formation, Nakhon Sawan Province, Middle Permian, Central Thailand .

DIAGNOSIS. — Species of Bairdia with flat carapace, DB nearly straight and long, AVB, VB, PVB flattened laterally and underlined by a ridge all along ventral part at RV.

DESCRIPTION

Carapace flat and subtrapezoid; dorsal outline broadly arched; DB of both valves long, straight, horizontal to slightly inclined to anterior; ADB long, angle between ADB and DB is 150°; angle between PDB and DB is 135°; AB rounded with medium radius of curvature, maximum convexity located below mid H; AVB convex; VB concave; PVB long and slightly convex; AVB, VB, PVB flattened and underlined by a fine ridge all along the ventral margin at RV; PB tapered, located at lower fourth of H; maximum of H located at mid L; surface smooth; LV larger than RV, and moderately overlaps RV all around the carapace, except at anterior and posterior ends; in dorsal view, carapace very thin.

R EMARKS

Bairdia songthami Chitnarin , n. sp. can be compared to B. girtyi from the Early Permian of South China ( Chen 1958); however, in the present Thai material, the maximum of convexity of AB and PB is located lower and DB is longer. Bairdia songthami Chitnarin , n. sp. differs from B. fontainei Chitnarin , n. sp. by its more convex AVB and PVB; here, AVB, VB and PVB are flattened latteraly and the ventral margin is underlined by a ventral ridge.

Figures

FIG. 3. — Ostracods from Indochina Block, Central Thailand. All specimens are stored at the Suranaree University of Technology Collections (Nakhon Ratchasima,Thailand), numbers SUT-09-xxxx. All the specimens are represented by complete carapaces.A-D, Bairdia khaokanaensis Chitnarin,n. sp.; A, holotype, right lateral view, SUT-09-2223, sample 07PB03-3; B, paratype, right lateral view, SUT-09-2226, sample 07PB03-3; C, paratype, right lateral view, SUT-09- 2231, sample 07PB03-3; D, left lateral view, SUT-09-2232, sample 07PB03-5; E, F, I, J, Bairdia incisedorsa Chitnarin, n. sp.; E, holotype, right lateral view, SUT-09-2216, sample 07PB05-3; F, paratype, right lateral view, SUT-09-2215, sample 07PB05-3; I, paratype, dorsal view, SUT-09-2221, sample 07PB05-3; J, ventral view, paratype, SUT-09-2220, sample 07PB05-3. G, H, K, L Bairdia fontainei Chitnarin, n. sp.; G, holotype, right lateral view, SUT-09-2187, sample 07LB05-3; H, paratype, right lateral view, SUT-09-2182, sample 07PB04-5; K, paratype, right lateral view, SUT-09-2183, sample 07PB05-3; L, right lateral view, SUT-09-2178, sample 07LB05-5; M-P, Bairdia songthami Chitnarin, n. sp.; M, holotype, right lateral view, SUT-09-2283, sample 07LB05-5; N, paratype, right lateral view, SUT-09-2278, sample 07PB05-4; O, paratype, left lateral view, SUT-09-2281, sample 07PB03-1; P, right lateral view, SUT-09-2284, sample 07LB05-A2. Scale bars: 100 μm.

FIG. 6. — Height (H)-length (L) diagram of Bairdia songthami Chitnarin, n. sp. Scale bar: 100 µm.