Brachyopidae

Nonsrirach, Thanit, Manitkoon, Sita & Lauprasert, Komsorn, 2021, First occurrence of brachyopid temnospondyls in Southeast Asia and review of the Mesozoic amphibians from Thailand, Fossil Record 24 (1), pp. 33-47 : 41

Brachyopidae indet.

Reference material

KS34-1481, posterior part of a skull ( Fig. 6a–b ); KS34-1474 ( Fig. 3q–t ) and KS34-1489 ( Fig. 3u–x ), intercentrum.

Formation/age

Phu Kradung Formation (Upper Jurassic).

Locality and sediment

The specimens were found in an outcrop at the Phu Noi locality, near Ban Dinchi village, Kham Muang District, Kalasin Province. Sediments at this site are grey to green siltstones. Other vertebrate fossils consist of the hybodont shark Acrodus kalasinensis , the ginglymodian fish Isanichthys lertboosi , the lungfish Ferganoceratodus annekempae , the xinjiangchelyid turtles Phunoichelys thirakupti and Kalasinemys prasarttongosothi , the teleosaurid crocodilian Indosinosuchus potamosiamensis , dinosaurs, and pterosaurs ( Buffetaut et al., 2014; Cuny et al., 2014; Deesri et al., 2014; Tong et al., 2015, 2019; Martin et al., 2018; Cavin et al., 2020).

Description

The material consists of three temnospondyl specimens not found in association: the posterior part of the skull ( KS 34- 1481, Fig. 6a–b ) and two intercentra ( KS 34-1474, Fig. 3q–t and KS34-1489, Fig. 3u–x ). The skull ( KS 34-1481) is short (approximately 14 cm width and 12 cm length), lacking otic notch and tabular horn in the supratemporal region. Ventrally, the interpterygoid vacuities are large, and the cultriform process of the parasphenoid is gracile and long. Posteriorly, the occipital condyles are rounded and projected well behind the posterior edge of the skull. This specimen is under study for a more detailed anatomical description. The intercentra ( KS 34-1474 and KS34-1489) are wedge-shaped with concave posterior surface and slightly convex anterior surface. The anterior surface shows a well-marked deep circular pit. The short skull, which lacks otic notch and tabular horn, and the position of occipital condyles are typical characters of Brachyopidae ( Warren and Marsicano, 1998, 2000), similar to those of the Jurassic brachyopid temnospondyl skull from China such as Sinobrachyops placenticephalus ( Dong, 1985) .

Figures

Figure 3. Thai Brachyopoidea indet. intercentra, TF 3228 (a–d), TF 31229 (e–h), TF 3144 (i–l, after Buffetaut et al., 1994b; fig. 1), and KS37-8 (m–p). Thai Brachyopidae indet. intercentra, KS34-1474 (q–t) and KS34-1489 (u–x). Anterior views (a, e, i, m, q, u), posterior views (b, f, j, n, r, v), left views (c, g, k, o, s, w), and right views (d, h, l, p, t, x).

Figure 6. Posterior part skull of Brachyopidae indet. (KS34-1481) from Phu Noi locality, in dorsal (a) and palatal views (b). Reconstruction outline of KS34-1481 (estimate reconstruction outline of the anterior part based on Sinobrachyops placenticephalus Dong, 1985) in dorsal (c) and palatal views (d). Reconstruction of Thai Brachyopidae (e) is not to scale (drawn by Sita Manitkoon). Abbreviations: oc, occipital condyles; exo, exoccipital; int, interpalatal vacuities; ob, orbit; p, parietal; pp, postparietal; pt, pterygoid; psp, parasphenoid; st, supratemporal; sub, subtemporal fossa; t, tabular; q, quadrate.