1304
Journal of Paleontology 91(6):1296–1305
(Fig. 11). Paleogeographically, these species were all restricted to the shallow- to moderately deep-marine environments of the Paleo-Tethys and Neo-Tethys region (Wu et al., 2016).
Conclusions
Figure 11. Stratigraphic ranges of all Fusichonetes species as recognized in this paper, including species that had previously been assigned to Tethyochonetes.
Fusichonetes by having a strongly concavoconvex profile and much coarser papillae and costae, although Rugaria also has a subquadrate outline and short dorsal median septum. Prorugaria Waterhouse, 1982, a Mississippian genus, is similar to Fusichonetes in having a subquadrate outline, but can be distinguished from the latter in having coarser papillae and costae and long accessory septa in the dorsal interior. Neochonetes Muir-Wood, 1962 differs from Fusichonetes in having a larger size, denser and bifurcate costellae, and papillae increasing in number and decreasing in size towards margin (Wu et al., 2016). Pygmochonetes Jin and Hu, 1978 could be easily distinguished from Fusichonetes by having a semicircular outline, being strongly concavoconvex, and lacking a sulcus and long accessory septa in the dorsal interior. Linshuichonetes Campi and Shi, 2002 differs frompresent genus in lacking anymedian, accessory or lateral septa. Waagenites Paeckelmann, 1930 differs from Fusichonetes by its much coarser costae, a more highly convex ventral valve and very incurved umbo. Waterhousiella Archbold, 1983 is similar to the present genus in its simple costellae, but differs in having a more convex ventral valve and vascular trunks developed in the ventral interior.
Implications for survival of brachiopods in the aftermath of the PTBME.—A final point that is worth mentioning is the impli- cation of this study in relation to the survival of brachiopods in the aftermath of the PTBME. According to some previous stu- dies on the Permian–Triassic brachiopods (Yang et al., 1987; Shen and Shi, 1996; Chen et al., 2005; Shen et al., 2006; Clapham et al., 2013; Ke et al., 2016), there are 17 Changhsin- gian brachiopod genera that survived into the aftermath of the PTBME, but did not play a role in the post-extinction recovery. After merging the two genera, the revised number of surviving Permian brachiopod genera is now 16, including Fusichonetes, as revised and its species expanded here. Following this revi- sion, the expanded Fusichonetes includes a total of 15 species at present time, comprised of 13 species transferred from Tethyochonetes and two original Fusichonetes species. Among the 15 species, two originated from the Capitanian (late Guadalupian), eight from the Wuchiapingian (early Lopingian) and five originated from the Changhsingian (late Lopingian), seven of which survived the PTBME until their final disappearance at the early Griesbachian (Chen et al., 2005)
Four different approaches (bivariate plots, Kolmogorov- Smirnov test, categorical principle component analysis, and cladistic analysis) were employed to analyze a dataset composed of 15 species belonging to Fusichonetes and Tethyochonetes by 15 variables. The variables chosen are a mixture of both numeri- cal and categorical characters and include important external and internal morphological features. Except for the Kolmogorov- Smirnov test demonstrating the possibility of separating the two genera in terms of shell outline approximated by the shell width/ length ratio, all other analytical procedures suggest that species of the two genera cannot be separated as two distinct taxa with consistency and statistical rigor. Consequently, we conclude that: (1) Tethyochonetes and Fusichonetes be merged, and (2) Fusichonetes be maintained as a valid genus in recognition of its chronological priority over Tethyochonetes, while the latter be suppressed as an invalid genus.With this revision and themerger of the two genera, the diagnosis of Fusichonetes is updated and refined, in part based on observations of new well-preserved material from South China. Additionally, the number of brachio- pod genera that survived the Permian−Triassic boundary mass extinction is revisedfrom17to16.
Acknowledgments
The authors thank S. Lee for helpful instructions on usage of TNT and revisions on the paper, J.B. Waterhouse for discussion on the paper, Y. Zhang for insightful suggestions on data collecting, and T. Yang, M. Yue, Y. Xiao, B. Chen, L. Zhu, B. Su for their help in fieldwork. Furthermore, we thank the journal editor and reviewers Y. Sun and C. Rasmussen for their constructive comments, and reviewer S. Shen for his valuable comments and help taking photos for the holotype of Fusichonetes. Support for this research was provided by NSFC (Grant Nos. 41372030, 41772016, 41602017), the Ministry of Education of China (B08030 of 111 Project), and an Australian Research Council grant to GRS (ARC DP150100690), as well as by Deakin University.
Accessibility of supplemental data
Data available from the Dryad Digital Repository: https://doi. org/10.5061/dryad.vb051
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