998


Journal of Paleontology


from Pilophyllia in having distinctively different septa with wedge-shaped rhabdacanths, comparatively shorter major septa, and generally widely spaced tabulae. Minor septa generally extend beyond the peripheral stereozone in Neopilophyllia n. gen., whereas in Pilophyllia they are commonly confined within the stereozone. A few other Silurian genera characteristically possessing


amplexoid septa also show some similarities to Pilophyllia. They include Pseudomphyma, Zelophyllum, Amplexoides, Lindstroemophyllum, Synamplexoides, and Protopilophyllum, which were discussed in some detail by various authors, e.g., McLean (1977), Wang et al. (1986), He et al. (1989), and McLean and Copper (2013). Although detailed analysis of their concepts and relationships is beyond the scope of the present study, Pilophyllia is clearly distinguished from these genera by the combination of a distinct peripheral stereozone and generally long major septa with commonly club-shaped rhabdacanths. Our revision of Pilophyllia also contributes to clarification


of its controversial familial assignment. When proposing this genus, Ge and Yu (1974) did not make any mention of this issue. It was subsequently assigned variably to Mucophyllidae Soshkina, 1947 (Cao, 1975; He, 1978), Streptelasmatidae Nicholson in Nicholson and Lydekker, 1899 (Kong and Huang, 1978), Kodonophyllidae Wedekind, 1927 (Hill, 1981; Lin et al., 1995; McLean and Copper, 2013), or more widely by most Chinese authors to Amplexidae Chapman, 1893 (e.g., Wang et al., 1986; Chen et al., 1997; Tang et al., 2007; He and Tang, 2013). The presence of generally cylindrical forms, a wide peripheral stereozone commonly containing club-shaped rhabdacanths, and distinctive amplexoid septa throughout the growth stages, clearly excludes possibi- lities of its assignment to Mucophyllidae or Streptelasmatidae. The main reason suggested by McLean and Copper (2013) for inclusion of Pilophyllia in the Kodonophyllidae lies in its general similarity to Kodonophyllum Wedekind, 1927 in overall morphology, and weakly amplexoid septa observed in very late stages of some specimens of this genus. However, given its clearly developed amplexoid septa and septal microstructure of both lamellar and rhabdacanthine types, Pilophyllia, together with other simpler Silurian amplexoid forms such as Amplex- oides and Synamplexoides, is most appropriately referred to the new family Amplexoididae as defined above, rather than to the evolutionarily unrelated Amplexidae.


Pilophyllia involuta Ge and Yu, 1974 Figure 4


v*1974 ?1978


Pilophyllia involutus Ge and Yu, p. 170, pl. 78, figs. 1, 2.


v non 1975 Ningqiangophyllum involutum; Cao, p. 185, pl. 39, figs. 1a, b, 2a, b.


Pilophyllia involutus; He, p. 117, pl. 59, fig. 1a, b.


v non 1982 Protopilophyllum involutum; Cao and Lin, p. 13, pl. 5, figs. 3a, b.


non 1986 Pilophyllia involuta; Wang et al., pl. 1, figs. 3a −d.


Holotype.—NIGP 22131 (transverse section) and 22132 (long- itudinal section), Ningqiang Formation (middle Telychian), Ningqiang County, Shanxi Province.


Diagnosis.—Pilophyllia with large corallum (at least 35mm diameter). Marginarium a narrow peripheral stereozone. In tabu- larium, major septa amplexoid, thinning gradually at first, then rapidly becoming attenuate, and extending to axial region, where they can coil somewhat in one direction. Minor septa generally confined within stereozone. Cardinal septum short in indistinct fossula. Septal microstructure appears entirely lamellar. Tabulae mostly complete, densely spaced,with broad, subhorizontal central platform and narrow downturned margins. Dissepiments absent.


Description.—Corallum solitary, large. Number of major septa 46 at 35mm corallum diameter. Marginarium a distinct peripheral stereozone 3mm in thickness, composed of thick minor septa and thickened peripheral ends ofmajor septa. In tabularium,major septa amplexoid, thinning gradually at first, then rapidly becoming attenuate, and extending to axial region, where they can coil somewhat in one direction, without forming axial structure (Fig. 4.1, 4.2). Minor septa generally confined within stereozone. Cardinal septum short in indistinct fossula. Septal microstructure appears entirely lamellar (Fig. 4.3, 4.4, 4.6). Tabulaemostly complete, with broad, subhorizontal central platform and narrow downturned margins (Fig. 4.5). Tabular spacing 6 or 7 tabulae in 5mm. Dissepiments absent. [Modified from Ge and Yu (1974, p. 170).]


Materials.—Holotype only.


Remarks.—The description and revised diagnosis of Pilophyllia involuta given above is based on restudy of its holotype, currently the only known specimen. Therefore, species variability is still not understood.Despite this, the combination of its large corallum and seemingly lamellar septal microstructure seems sufficient to justify separation of it from other species of Pilophyllia. Several other forms were previously regarded as synonyms


of Pilophyllia involuta, including coralla described as Ningqian- gophyllum involutum by Cao (1975), Protopilophyllum involu- tum by Cao and Lin (1982), and Pilophyllia involuta by Wang et al. (1986), all of roughly comparable age. However, these forms are all much smaller in corallum size (commonly < 28mm diameter) compared to the holotype of P. involuta.We reexamined the type material of N. involutum, originally illustrated by Cao (1975, pl. 39, figs. 1, 2). It is now clear that its septa are composed of rod-like trabeculae coated by lamellar tissues (reillustrated in Figure 6), which is remarkably different from those of P. involuta. This is also the case in the type material of Cao and Lin (1982) reexamined for this study. Similarly, the same septal microstructure is also clearly shown in illustrations of


the specimen identified as P. involuta by Wang et al. (1986, pl. 1, fig. 3a−d). Therefore, we assign these forms to P. fenggangensis, rather than P. involuta (see more details below). A further specimen, identified as Pilophyllia involutus by


He (1978), from the Ningqiang Formation (middle Telychian) of Niufuling, Guangyuan, northern Sichuan, has superficially similar morphology to the holotype of P. involuta. Without information on its corallum size and septal microstructure, however, this identification is regarded here as tentative.


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