Bairdia incisedorsa 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 : 658-659

Bairdia incisedorsa Chitnarin , n. sp.

( Figs 3 E-F, I-J)

TYPE MATERIAL. — Holotype: one complete carapace (SUT-09-2216; Fig. 3E ); paratype, one complete carapace (SUT-09-2215; Fig.3F ).

ETYMOLOGY. — From diagnosis character.

MATERIAL EXAMINED. — Five complete and three incomplete carapaces.

DIMENSIONS. — H = 0.46-0.50 mm, L = 0.85-0.90 mm, H/L = 0.54-0.55, Holotype: H = 0.501 mm, L = 0.901 mm; Paratype: H = 0.469, L = 0.855.

TYPE HORIZON. — Sample 07 PB 05-3, Ban Naen Sawan I section, Tak Fa Formation, Roadian, Middle Permian.

TYPE LOCALITY. — Ban Naen Sawan I section (15° 54’11’’N, 100° 53’36’’E), Phetchabun Province, Central Thailand.

OCCURRENCES. — Sample 07 PB 05-3, Ban Nean Sawan I section, Phetchabun Province, Tak Fa Formation, Middle Permian, Central Thailand.

DIAGNOSIS. — Species of Bairdia with robust carapace, strong overlap of LV over RV in dorsal region, hinge invaginated, AB with very small radius of curvature and maximum of convexity located very high, tapering PB with maximum of curvature located at mid H, slight overlap of LV on RV at AVB and PVB, dorsal view spindle-shaped.

DESCRIPTION

Carapace robust; dorsal outline broadly arched, DB of RV convex, DB of LV, hinge short and strongly invaginated; ADB short and concave; anterior end tapered and pointing upward, located above mid H; AVB long and slightly convex, angle between AVB and VB is 120°; VB short, VB of RV concave, VB of LV slightly convex; PVB long and slightly convex, angle between PVB and VB is 155°; PB tapering and located at mid H; PDB long and concave; anterior, posterior, anteroventral and posteroventral regions flattened laterally; maximum H located at mid L; surface smooth; LV larger and strongly overlaps RV at dorsal and ventral borders, slightly overlaps at AVB and PVB; in dorsal view, carapace spindle-shaped, with median part inflated and extremities strongly flattened.

REMARKS

Bairdia incisedorsa Chitnarin , n. sp. could be easily identifiable by its diagnostic characters. However, in lateral view, it is closed to B. permiana Hamilton, 1942 from the Guadalupian, Middle Permian of Texas ( Hamilton 1942). The two species can be differentiated by dorsal characteristics and the lower H/L ratio of B. incisedorsa Chitnarin , n. sp. The present species can be compared with B. subleguminoides Chen, 1987 from the Late Permian of South China ( Shi & Chen 1987) but the latter species is more elongated with longer anterior part and DB more convex at RV.

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.