Permian plant fossils have never been reported from the Shan Plateau in eastern Myanmar. Recently, a black to gray carbonaceous mudstone unit containing abundant plant fossils was discovered just below the lowest part of Thitspin Limestone Formation from the Linwe Area, eastern Myanmar. Although only five taxa were identified, the plant assemblage provides the first evidence of the occurrence of Cathaysian elements in eastern Myanmar and potentially indicates the presence of a highly diverse Permian flora. Among the five species, Cordaites principalis and Annularia mucronata were cosmopolitan species; while Callipteridum cf. koraiense, Taeniopteris crassinervis Mo and Rhipidopsis lobata were mostly recorded in the Cathaysia Flora. Therefore, the present assemblage generally indicates a palaeobiogeographical affinity to the Cathaysian Province. Stratigraphically, Callipteridum cf. koraiense was mainly reported from Cisuralian to Wordian; whereas Taeniopteris crasssnervis Mo and Rhipidopsis lobata were recorded from Capitanian to Changhsingian, which suggests a general Permian age based on the plant assemblage itself only. However, the carbonaceous mudstone at the outcrop is overlain by the Thitspin Limestone Formation containing middle Guadalupian fusulinids. Based on previous faunal analyses, the Sibumasu terrane contains typical Gondwanan cold-water faunas during the early Cisuralian, warm-water faunas occurred after Sakmarian. Thus, age of the fossil-plant-containing carbonaceous mudstone is very likely between late Cisuralian and early Guadalupian as constrained by its overlying fusulinids and its warm Cathaysian palaeobiogeographical affinity.

缅甸东部的山高原从未有二叠纪植物化石的报道。最近，在缅甸东部的林威地区，在Thitspin石灰岩地层最低部分的下方发现了一个黑色至灰色的含碳质泥岩单元，其中含有丰富的植物化石。尽管仅识别出五个分类单元，但该植物组合提供了缅甸东部华夏元素发生的第一个证据，并可能表明存在高度多样性的二叠纪植物区系。在这五个物种中，CordaitesPrincipalis和Annularia mucronata是世界性物种。而Callipteridum cf. koraiense，Taeniopteris crassinervis Mo和Rhipidopsis野葛大多记录在国泰植物群中。因此，本组合通常表明对华夏省的古生物地理亲和力。从地层学上看，Callipteridum参见。koraiense主要是从Cisuralian到Wordian报道的；而Taeniopteris crasssnervis Mo和Rhipidopsis lobata从Capitanian到Changhsingian被记录下来，这表明仅基于植物组合本身就具有二叠纪的一般年龄。然而，露头处的碳质泥岩被包含中瓜达卢普岩藻林岩的Thitspin石灰岩地层覆盖。根据先前的动物分析，锡伯马苏地层包含早期Cisuralian时期的典型的Gondwanan冷水动物群，而在Sakmarian之后发生的温水动物群。因此，由于其上覆的融合藻类化合物及其温暖的凯撒地区古生物地理亲和力，在西奥拉期末和瓜达卢普期之间很可能含有化石植物的碳质泥岩的年龄。