Tianzhushanellidae Conway Morris

Kouchinsky, Artem, Bengtson, Stefan, Landing, Ed, Steiner, Michael, Vendrasco, Michael & Ziegler, Karen, 2017, Terreneuvian stratigraphy and faunas from the Anabar Uplift, Siberia, Acta Palaeontologica Polonica 62 (2), pp. 311-440 : 385-386

Family Tianzhushanellidae Conway Morris in Bengtson et al., 1990

Remarks.—Tianzhushanellids are represented by disarticulated, bilaterally symmetrical, and probably originally bivalved (although no firm evidence exists, see Li et al. 2014) and aragonitic shells assignable to stem-group brachiopods. The type genus, Tianzhushanella Liu, 1979 , was synonymized with Lathamella Liu,1979 ( Esakova and Zhegallo 1996; Parkhaev in Gravestock et al. 2001; Li et al. 2014; compare Li 2012). Other genera attributed to tianzhushanellids are the apistoconchs ( Apistoconcha spp. ) from Cambrian Stage 3 of Gondwana ( Australia and Turkey; Bengtson et al. 1990; Gravestock et al. 2001; Sarmiento et al. 2001; Elicki and Gürsu 2009), North China (Li et al. 2014), Mongolia ( Esakova and Zhegallo 1996), and Laurentia ( Greenland; Skovsted 2006). Apistoconchs have been discussed as stem-group brachiopods ( Balthasar 2008; Skovsted et al. 2010) or referred to the molluscs (Parkhaev 1998; Parkhaev in Gravestock et al. 2001). Although Tianzhushanella ovata is often attributed to paterinid brachiopods, the shell composition of this form was originally calcareous, probably aragonitic (Li and Chen 1992), and is thus different from the primarily phosphatic paterinids.

The first appearance of tianzhushanellids ( Tianzhushanella ) predates the first brachiopods (Kouchinsky et al. 2010, 2012) such as the organophosphatic paterinids (e.g., Aldanotreta sunnaginensis Pel’man, 1977, from the Nochoroicyathus sunnaginicus Zone of the lower Tommotian Stage of Siberia) and calcareous obolellids ( Nochoroiella isitica Pel’man, 1983, and Obolella sp. from the Dokidocyathus lenaicus Zone of the middle Tommotian; see Bengtson et al. 1987; Ushatinskaya and Malakhovskaya 2001) from the upper part of Cambrian Stage 2. Tianzhushanellids (= lathamellids) are reported from lower part of Cambrian Stage 2 of South China, where their first undoubted representatives are known from the Watsonella crosbyi Assemblage Zone Li and Chen 1992 ; Steiner et al. 2007; see Kouchinsky et al. 2012: online appendix 1). Besides the poorly illustrated Tianzhushanella ovata Liu, 1979 , redescribed by Xing and Yue (in Xing et al. 1984), such forms are also known from South China as Lathamella caeca Liu, 1979 , and L. symmetrica Li and Chen, 1992 . Tianzhushanella sp. and T. tolli sp. nov. are herein described from the age-equivalent beds of the Siberian Platform. It appears, therefore, that tianzhushanellids are widespread in the terminal Fortunian–lower part of Cambrian Stage 2 interval.