A new Middle Permian locality in northern Johore, Peninsular Malaysia, yields a small-sized, but compositionally unique, brachiopod fauna consisting of eight species: 'Pseudoleptodus' sp., 'Caricula' cf. 'salebrosa' Grant, 'Neochonetes' ('Nongtaia') aff. 'arabicus' (Hudson & Sudbury), 'Karavankina' sp., 'Transennatia' cf. 'insculpta' (Grant), 'Hustedia' sp., 'Orthothetina' sp., and martiniid indet. The first four genera are new records for Malaysia; in particular, the rare taxa 'Pseudoleptodus' and 'Caricula' characterize the fauna. The brachiopods occur together with the ammonoid 'Agathiceras' sp., the nautiloid 'Foordiceras'? sp., bivalves, and crinoid stems. The locality belongs to the East Malaya terrane of the Cathaysian biotic region, but some affinities to species of the Sibumasu province are recognized. The Malaysian forms of 'Pseudoleptodus', 'Caricula' and 'Transennatia' are similar to those of the Ratburi Limestone (southern Thailand). A Roadian–early Wordian age is interpreted for the Johore fauna. The similarity of brachiopods reported here with those from the Ratburi Limestone suggests that there was species interchange or one-way migration between shallow waters of East Malaya and Sibumasu across the main Palaeo-Tethys. The Tethyan seaway between the two terranes must have been narrower than previously interpreted by some authors to allow such faunal traffic during the Roadian–Wordian time period.

Coiled nautiloid Shells referred to 'Sibyllonautilus bamaensis' Sone sp. nov. are reported from the top of the Gua Bama limestone hill in Pahang, Peninsular Malaysia. This is the first record of the genus in Southeast Asia; a pre-Ladinian, Triassic age is indicated for the occurrence. Based on the presence of 'Sibyllonautilus' and previously reported Late Permian (Lopingian) foraminifers and algae, the Gua Bama limestones are interpreted to range from the Late Permian to the Triassic. It further seems plausible that some parts of Gua Bama are stratigraphically correlated to those of the nearby Gua Sei limestone hill, which has yielded basal Triassic conodonts, and that either or both the Gua Bama and Gua Sei hills may contain yet unconfirmed successions of the Permian-Triassic boundary.

The Permian–Triassic boundary (PTB) is defined by the first appearance of the conodont species 'Hindeodus parvus' (Kozur & Pjatakova). It is now indicated to be 252.3 Ma by zircon U-Pb radio-isotopic dating (Mundil et al., 2004; Mundil et al., 2010). Despite decades of searching (e.g. Metcalfe, 1984), the PTB has not been located precisely to date in Malaysia. In Pahang, central Peninsular Malaysia, there are several limestone sections, which have yielded biostratigraphic data indicating the plausible presence of the PTB. Two of them, Gua Bama and Gua Sei, have now emerged as the most promising localities, since they both exhibit carbonate strata ranging from Upper Permian to Triassic. The Triassic nautiloid 'Sibyllonautilus bamaensis' was recently reported from the top of Gua Bama, confirming the presence of the Triassic (Sone et al., 2004). The Triassic nautiloid-bearing deposit accompanies abundant algae, which in general are extremely rare in the Early Triassic; therefore, it is interpreted that the uppermost part of the Gua Bama strata likely extends to the post-Early Triassic, most likely Middle Triassic (Sone et al., 2008). From the base of Gua Bama, Late Permian colaniellid foraminifers have been reported (Lim and Nuraiteng, 1994), and conodonts and brachiopods have recently been discovered. The conodonts include several species of 'Clarkina', 'Hindeodus julfensis' and 'Iranognathus movschovitschi', confirming a Changhsingian age. The brachiopods were found in the siliciclastic strata 2 m below the conodont beds; that is, passage strata from the underlying siliciclastic sequence to the limestones. They include the rare genus 'Dongpanoproductus', known elsewhere only from the upper Changhsingian of South China (He et al., 2005). Thus, the lowest part of Gua Bama is dated as late Changhsingian age, suggesting that the Gua Bama sequence probably includes the PTB transition.

The Permian-Triassic boundary (PTB), despite decades of searching, has not been located precisely to date in Malaysia. We are currently focusing our search for the PTB in central Peninsular Malaysia as part of our contribution to the geological heritage scheme launched by the National University of Malaysia (Universiti Kebangsaan Malaysia) and as a contribution to the new IGCP 572 Project "Restoration of marine ecosystems following the Permian-Triassic mass extinction: Lessons for the present". In central Peninsular Malaysia, there are several limestone karst hills which have yielded data indicating the possible presence of the PTB. Among them, Gua Bama has now emerged as the most prospective site, as it displays strata ranging from Upper Permian to Triassic. Its lithofacies is a thickly to massively bedded succession of limestones, with occasional tuffaceous layers.