996
Journal of Paleontology
Figure 15. Neopilophyllia irregularis (Cao, 1975), XACGS-G361, holotype: (1, 4) transverse section of earlier growth stage and an enlarged portion (4); (2, 5) longitudinal section and an enlarged portion (5); (3, 6) transverse section of later growth stage and an enlarged portion (6). Scale bars=2mm.
concept basically follows that of Wang et al. (1986), whose revision was based on material that we do not regard as conspecific with the type species, P. involuta. As noted by McLean and Copper (2013, p. 95, 96), uncertainties over phylogenetic relationships between the type species and other species attributed to Pilophyllia would likely remain pending restudy of the type material of P. involuta to clarify its septal nature and microstructure. In the present study, holotypes and paratypes of the type
species belonging to either Pilophyllia or Neopilophyllia n. gen. were rephotographed to figure the characteristics, particularly septal microstructure, of the specimens. Illustrations of the holotype of P. involuta show that major septa are apparently intermittently discontinuous in transverse section (Fig. 4.2), and septal ridges rest on successive tabular floors in longitudinal section (Fig. 4.5). Both clearly indicate the amplexoid nature of the major septa. Septal microstructure appears to be entirely composed of lamellar stereomes, with no fibrous tissues observed (Fig. 4.3, 4.4, 4.6), which does not fit characteristics of the species group mentioned above. However, the trabeculae that are observed in the species currently assigned to Pilophyllia appear to be variably developed. The trabeculae generally arise from lamellar tissues, and gradually become thicker, as described commonly in species documented by Tang et al.
(2007), or rarely are consistently rather thin and even seemingly absent with a replacement of lamellar tissues (Figs. 8.6, 9.6, 9.9). This observation could indicate that the two types of septal microstructure are closely related and are probably transitional. We emphasize the significant taxonomic value of
septal microstructure in amplexoid corals and regard the appearance of rhabdacanths of wedge-like shape in septa as representing a major step in the evolution of this distinctive coral clade. In view of this, those forms previously included in Pilophyllia that develop generally short septa with wedge- shaped rhabdacanths are transferred herein to a new genus Neopilophyllia n. gen. (see further discussion of Neopilophyllia n. gen., below). They are separated from other forms with longer major septa consisting of club-shaped rhabdacanths set in thick lamellar stereomes, which are retained within the redefined concept of Pilophyllia. The revised concept of Pilophyllia necessitates reconsidera-
tion of its relationships with other morphologically similar genera, as discussed below. Ningqiangophyllum Cao has been closely associated with Pilophyllia (Wang et al., 1986; McLean and Copper, 2013), but is clearly a homonym of the unrelated Ningqiangophyllum Ge and Yu, 1974, as noted by Hill (1981) and other authors (Lin et al., 1995; McLean and Copper, 2013).
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