22


Journal of Paleontology 91(1):12–24 The early Permian fusulinids of the Cathaysian (tropical


Tethyan) region are characterized by many species in the subfamily Pseudoschwagerininae. By contrast, the Gondwana-derived blocks contain generally less diverse pseudoschwagerine. For example, the common genera Pseudoschwagerina, Robustoschwagerina, Sphaeroschwagerina,and Zellia are abundant in most sections of SouthChina (Zhu et al., 2002; Shi et al., 2009), but they are sparsely distributed in the Gondwana-derived blocks (Ueno, 2003; Table 1). Moreover, the overall diversities of early Permian fusulinids in the Gondwana-derived blocks are commonly lower than those in South China. For example, the Asselian–Sakmarian fusulinids typically include over 15 genera in South China, whereas most Gondwana- derived blocks have fewer than 10 genera. In the Tengchong Block, early Permian fusulinids are only composed of three genera, Eoparafusulina, Pseudofusulina,and Monodiexodina,and the association is devoid of Pseudoschwagerininae. The middle Permian fusulinids of the Gondwana-derived


blocks are characterized by: (1) the relatively poor development of the tropical/subtropical Verbeekinidae and Neoschwagerinidae taxa, and (2) the association of certain Schwagerinidae genera, such as Chusenella, Rogososchwagerina,and Eopolydiexodina (Ozawa, 1987). In the Tengchong Block, only one genus of Neoschwager- inidae, i.e., Cancellina, has been reported from themiddle Permian strata of the northern region. Instead, Chusenella is the principal element. It occurs abundantly and is accompanied by Nankinella or Monodiexodina in the Shanmutang area and by Schwagerina in the Shuangheyan valley. In this respect, the fusulinids from the Tengchong Block bear strong Gondwana affinity. With regard to the generic diversity through the early and


middle Permian, the Gondwana-derived blocks could be further divided into two groups. Group 1 contains Turkey, Iran, and Transcaucasia, south Afghanistan, south Pamir; Group 2 includes the Lhasa Block, PTNPM, Shan State, Baoshan, and the Tengchong Block. Fusulinids from the former have evidently higher diversities than those from the latter in general, especially during Kungurian and the succeeding middle Permian. Specifically, in the Asselian to Artinskian (early Permian)


times, the blocks of Group 2, except the Tengchong Block, hosted fewer fusulinid genera than those ofGroup 1. The generic number from Tengchong Block might have been overestimated because some of the previously reported genera cannot be checked due to the lack of illustration or description. In the Kungurian, fusulinids inGroup 1 areaswere diverse, characterized by the proliferation of newly developed Verbeekinidae and Neoschwagerinidae genera containing a new inner skeletal structure named parachomata. However in Group 2 areas, fusulinids scarcely occurred, and the only recorded genera, i.e., Monodiexodina and Parafusulina, developed another new structure called cuniculi. During the middle Permian, fusulinid in Group 1 areas were


more diverse, including certain newly evolved taxa, i.e., Neosch- wagerinidae and Verbeekinidae. Group 2 areas still hosted less diversified fusulinids, especially within the Neoschwagerindae and Verbeekinidae, than Group 1. The diversification of the families Verbeekinidae and Neoschwagerinidae is believed to be diagnostic for the middle Permian Tethyan region (Leven, 1993; Ross, 1995). Representatives of these families are thought to have been thermally stenotopic and typify tropical or subtropical warm-water environ- ment (Gobbett, 1967; Ozawa, 1970; Ross, 1982; Stevens, 1985; Ueno, 2003). They are abundant in the Cathaysian Tethyan region


and well developed in Group 1 areas, but obviously less so in Group 2. In most blocks of Group 2, Schwagerinidae fusulinids, such as Chusenella, play the major role. In the Tengchong Block, Chusenella co-occurs with either Schwagerina or Nankinella, and in the PTNPM it is accompanied by Schwagerina, Nankinella, and Staffella in several sites (Ingavat-Helmcke, 1993; Hassan et al., 2014). A Chusenella-Nankinella association was reported from the Xainza area of the Lhasa Block, although the dominant species are different from those of the Tengchong Block (Huang et al., 2007; Zhang et al., 2010). It is noteworthy that the Chusenella species in the Xainza area are rather small, displaying a certain similarity to those of the Tengchong Block as mentioned before. In the Baoshan Block, Chusenella was found in various locationswith Schwagerina, Rugosofusulina,or Nankinella (Huang et al., 2015b). The genus has not been reported yet from the Shan State. In summary, by comparison with Group 1, the regions of


Group 2 demonstrate overall fewer fusulinid taxa in both early and middle Permian and impoverished Neoschwagerinidae and Verbeekinidae. The Gondwana-derived blocks were geographically reconstructed to lie in a southern transitional region between the Paleo-equator and temperate/cool Gondwanan Pangea during most of the Permian (Shi et al., 1995; Grunt and Shi, 1997; Shi and Archbold, 1998; Ueno, 2003). Most Group 2 members, i.e., PTNPM, Shan State, Baoshan Block, are interpreted to occur in the higher latitude portion of the southern transition region (Ueno, 2003; Huang et al., 2015a, 2015b, personal communication, 2016). In this regard, the Tengchong Block shares more similarities with these temperate marine blocks. This is consistent with the aforementioned paleoenvironment inference. There are still several notable distinctions between the


and confined paleogeographically to the northern and southern middle latitudinal areas (Ueno, 2006). However, there is no Monodiexodina reported from the Lhasa Block, Shan State, or Baoshan Block, but Monodiexodina gigas is a dominant species of the middle Permian of the Tengchong Block. Moreover, this species is significantly distinct from the Monodiexodina species of PTNPM (Fontaine et al., 1994; Hassan et al., 2014), and any other reported Monodiexodina species, for evolving a huge test with the diameter of 2 cm (Shi et al., 2008). Among the fusulinids absent from the Tengchong Block,


fusulinids of Tengchong Block and those of other Gondwana- derived blocks, revealing a somewhat endemic nature of the block. Whereas there are several Neoschwagerinidae and Verbeekinidae genera developed in the Shan State, Baoshan Block, and Lhasa Block of Group 2, they are rather scarce in the PTNPM and Tengchong Block. In the Tengchong Block, only the genus Cancellina of Neoschwagerinidae was reported in the Guanyin- shan area (Fan, 1993).We searched that area during the fieldwork in 2010, but failed to verify its presence. Monodiexodina was suggested to be an antitropical genus


Eopolydiexodina is thought to have been restricted to the Laurentian and peri-Gondwanan borders of the Tethys (Ueno, 2003;Colpaert et al., 2014). It is an endemic genus in theWestern Tethys Province and constitutes a typical combo associated with Rugososchwagerina or Xiaoxinzhaiella (Ueno, 2003; Shi et al., 2005). This combo is absent in the Tengchong Block, but thrived in both Baoshan and Lhasa blocks.


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