Chengxianoproductus Liao and Meng, 1986

Chen, Zhong-Qiang, Campi, Monica J., Shi, Guang R. & Kaiho, Kunio, 2005, Post-extinction brachiopod faunas from the Late Permian Wuchiapingian coal series of South China, Acta Palaeontologica Polonica 50 (2), pp. 343-363 : 357-358

Genus Chengxianoproductus Liao and Meng, 1986

Type species: Chengxianoproductus nitens Liao and Meng, 1986 , subsequent designation herein; Changhsingian (Late Permian), Hunan, South China.

Nomenclature discussion.— Liao and Meng (1986) applied two different species names, Chenxianoproductus nitens ( Liao and Meng, 1986) and C. typica ( Liao and Meng, 1986) , for the same specimens. Both species have been regarded as the type species of Chenxianoproductus . However, according to the principal of page priority, C. nitens Liao and Meng, 1986 is treated as a valid species and selected here as the type species for the genus, while C. typica Liao and Meng, 1986 is an invalid species name and abandoned.

Emended diagnosis.—Medium−sized Echinoconchinae , with subcircular to triangular−oval outline; sulcus and fold variously developed; dorsal valve flat to slightly concave with a deep corpus cavity. Ventral exterior with broad bands, each bearing rows of alternatively arranged spine bases; spines suberect. Dorsal valve with similar ornament to ventral valve. Cardinal process small, bilobate; median septum low, extending over half disc−length; lateral ridges originating at cardinal process base, curving down inside ears; inner surface densely pustulate. Chengxianoproductus superficially resembles Alatoproductus Jin and Hu, 1978 in terms of shell outline, spinose exteriors and internal characteristics; however, Chengxianoproductus embraces conspicuous concentric bands and smaller alternatively arranged spine bases; whereas the spine bases of Alatoproductus are much coarser and randomly arranged. Another ally is Stictozoster Grant, 1976 , which also possesses dense spines on concentric bands, a bilobate cardinal process, and a long, thin long dorsal median septum. However, Chengxianoproductus is distinct from Grant’s genus in having a more weekly concavo−convex profile, a sulcus, a fold, and dorsal lateral ridges. Chengxianoproductus also approaches moderately both Waagenoconcha Chao (1927) and Tschernyschewia Stoyanow, 1910 in externally spinose ornamentation, but differs clearly from the latter two genera in having unvaried sizes of its spines and conspicuous concentric bands. In addition, Chengxianoproductus lacks the well−developed ventral interarea and a rather high ventral median septum, which are diagnostic of Tschernyschewia .

Remarks.— Shen et al. (1992: 178) treated Chengxianoproductus Liao and Meng, 1986 as a junior synonymy of Parapulchratia Zhan, 1979 because (1) both genera are generally comparable in many respects and (2) Liao and Meng (1986) assigned parts of specimens of Productus pustulosus var. palliata Kayser, 1883 , type species of Parapulchratia , to their genus. However, Kayser’s (1883) species has long remained poorly understood and later has broadly applied to Chinese Upper Permian specimens (e.g., Frech 1911; Chao 1927; Wang et al. 1964; Zhan 1979). In particular, Chao (1927) upgraded Kayser’s variant species to species level and referred it to Waagenoconcha . Wang et al. (1964) refigured one of Chao’s (1927) specimens to represent Kayser’s species.

Kayser’s figured materials include a broken ventral valve, one complete dorsal valve, and three broken dorsal internal molds. Of these, the ventral valve (see Kayser 1883: pl. 27: 9) possesses a rather narrow, inflated umbo and nearly centrally arranged, coarse spines, lacks a median sulcus and concentric lamellae, and thus is easily separated from Chengxianoproductus that is defined by a broad ventral umbo, a broad but distinct median sulcus, and numerous broad lamellae, each bearing rows of alternatively arranged spines. Alternatively, the overall appearance of Kayser’s (1883) ventral valve is morphologically close to Alatoproductus Jin and Hu, 1978 or Tschernyschewia Stoyanow, 1910 or Waagenoconcha Chao, 1927 . The complete dorsal valve (see Kayser 1883: pl. 27: 13) internally embraces a broad cardinal process and costal impressions and is suggestive of a Haydenella species. Other three incomplete dorsal internal molds ( Kayser 1883: pl. 27: 10–12) are indeterminate but are morphologically close to Waagenoconcha or Edriosteges .

The materials ascribed to Waagenoconcha palliata species by Chao (1927) and Wang et al. (1964), housed in the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, are re−examined in this study (by ZQC in 2004). Chao’s W. palliata includes several specimens collected from various regions of South China. Of these, the specimen ( Chao 1927: pl. 7: 5, NIGP 984) from the Changxing coal mine of Zhejiang Province and the specimen ( Chao 1927: pl. 7: 6, unregistered) from the Fengcheng of Jiangxi Province are both possessing a strong, bilobed cardinal process and conspicuous cardinal ridges and are comparable with that of Tschernyschewia , as suggested by Liao and Meng (1986: 80). Both specimens ( Chao 1927: pl. 7: 3, 4a, b, NIGP 986 and NIGP 985, respectively) are externally similar. Of these, the specimen (NIGP 986) was later re−illustrated by Wang et al. (1964: pl. 40: 22–24) under the name “ Waagenoconcha ” palliata . Our (ZQC) and Prof. Z.T. Liao (personal communication 2004) re−examination reveals that this specimen (NIGP 986) is sculptured with varied spines and conspicuous concentrical lamellae, and each lamella bears rows of fine spines at its front edges. As a result, the specimens figured by Chao (1927) and Wang et al. (1964) can not share the same species name with Kayser’s figured materials. It is also noteworthy that Zhan (1979: 88), when he created Parapulchratia , stated that his materials of P. palliata are almost same to Chao’s (1927: pl. 7: 6) specimen from Jinagxi Province. The latter seems to be a Tschernyschewia species ( Liao and Meng 1986). Accordingly, Zhan’s specimens are readily different from Kayser’s materials.

In summary, Kayser’s (1883) species includes morphologically varied specimens. A re−examination of Kayser’s original type materials is necessitated. The figured materials by Kayser (1883) seem to be generically different from Chengxianoproductus . These specimens ascribed to Waagenoconcha palliata ( Kayser, 1883) by later workers ( Chao 1927; Wang et al. 1964; Zhan 1979) are not conspecific with Kayser’s figured materials. As such, Chengxianoproductus is tentatively regarded as an independent genus from Parapulchratia .

Depth of corpus cavity is crucial to the correct classification of Chengxianoproductus (C.H.C. Brunton, personal communication 2003). The slightly concave to flattened dorsal valve and highly convex ventral valve indicate that Chengxianoproductus possesses a rather deep corpus cavity, which is diagnostic of the genus. Placing stress on the deep corpus cavity, we consider that Chengxianoproductus fits better within the Echinoconchidae (C.H.C. Brunton, personal communication 2003) than the Sentosiidae McKellar, 1970 (see Brunton et al. 2000). However, the weak bands of spines on Chengxianoproductus are slightly more of a sentosiid character than echinoconchid character. This feature therefore also distinguishes Chengxianoproductus from other genera of the Echinoconchidae . Thus, the assignment of Chengxianoproductus to the Echinoconchini is tentative.