Shao et al.—Fortunian cnidarians and cycloneuralians in South China
missing, and the TNT memory was enlarged to 10,000 trees. In the phylogenetic analysis of cnidarians, collapsing rule 3 (max. length=0) is adopted, consistent with the default collapsing rule of PAUP (Swofford, 2002), because PAUP was adopted in the ori- ginal phylogenetic analysis of Dong et al. (2016) with default set- tings. In the phylogenetic analysis of cycloneuralians, collapsing rule 1 (min. length=0) is adopted, and this is the default collapsing rule of TNT. Traditional search (heuristic search with 1,000 random stepwise addition replicates saving up to 10 trees per replicate, followed by TBR branch swapping) was adopted. The cladograms were redrawn with Adobe Illustrator CS5.
Repositories and institutional abbreviations.—The current specimens are now deposited in the collection of the University Museum of Chang’an University (UMCU), Xi’an, China.
Results
Olivooides multisulcatus.—Materials assigned to Olivooides multisulcatus Qian, 1977 are less common in our collection, and only three specimens are presented here (Fig. 4.1–4.3). They represent a progressive developmental sequence from a late embryonic stage (Fig. 4.1) to a large individual (Fig. 4.3). Olivooides multisulcatus differs from O. mirabilis (Yue in Xing et al., 1984) mainly by their different sizes, with the embryos and hatched stages being much smaller than those of O. mirabilis (Steiner et al., 2014). In addition, the hatched stages of O. multisulcatus have five rows of triangular thickenings on their post-embryonic tissues (Fig. 4.3).
Olivooides mirabilis.—Olivooides mirabilis is represented by two specimens here, including a pre-hatching embryo (Fig. 4.4) and a fragment of a large individual (Fig. 4.5). The fragment (Fig. 4.5) is part of the abapical end, with three distal annuli and one circlet of 10 terminal lobes preserved. It should be noted that the diameter of this fragment is ~3.16mm. If the maximum diameter of the hatched stages is positively related with the total length, the completely preserved length is estimated to be ~8.6mm, with at least 50 annuli. This is a very large individual, and it implies that the adults of O. mirabilis, and perhaps those of Olivooides multisulcatus and Quadrapyrgites quadratacris, could have reached centimeter-scale dimension with more than 50 annuli on their post-embryonic tissue.
Pseudooides prima.—Only three embryos assignable to Pseu- dooides prima Qian, 1977 were recovered (Fig. 5.1–5.3). The embryos have a so-called “germ-band” area made of 12 com- partments separated into six pairs by a median furrow and five lateral furrows. These compartments are arranged in biradial symmetry, defining the fundamental symmetry pattern of P. prima. The remaining part of the embryos is undifferentiated. The fossils are usually internally hollow or filled with secondary mineral matter. Generally, they are slightly collapsed and, therefore, the outer surface is much wrinkled.
Quadrapyrgites quadratacris.—The general morphology of Quadrapyrgites quadratacris has been described by Steiner et al. (2014) and Liu et al. (2014a), and will not be repeated here. Liu et al. (2014a) reconstructed the post-embryonic development of Q. quadratacris and demonstrated the growth mode of the term- inal lobes and annuli. The current material also exhibits a
119 difference in the number of annuli of the post-embryonic tissue,
ranging from two (Fig. 6.1, 6.2), three (Fig. 6.3), four (Fig. 6.4), five (Fig.6.5), six(Fig. 6.6),seven (Fig.6.7), 10 (Fig.6.8), 11 (Fig. 6.9), 14 (Fig. 6.10), to at least 18 (Fig. 6.11). Combinedwith the previously reported data (Liu et al., 2014a;Steiner et al., 2014), the number of annuli on the post-embryonic tissues of Q. quad- ratacris extended continuously fromone to at least 18, and this is interpreted to be a consecutive post-embryonic developmental sequence. It should be noted that the specimenwith 18 annuli (Fig. 6.11) is exceptionally large, ~3.28mm long and 1.2mm max- imum width. Its abapical end is broken, thus the total length and number of annuli are uncertain.
Eopriapulites sphinx.—Eopriapulites sphinx Liu and Xiao in Liu et al., 2014b is a millimeter-sized animal. The adult body length/width ratio is about more than 10, thus the animal looks a little slender (Shao et al., 2016). A detailed description of E. sphinx was given in Liu et al. (2014b) and Shao et al. (2016), and so is not repeated here. The ontogeny and developmental mode of E. sphinx is currently unknown because its embryonic and younger juvenile stages are lacking. The current specimens (Fig. 7.1, 7.4) are proposed to be
trunk parts of very large juveniles or adults. They are regarded as conspecific with Eopriapulites sphinx due to co-occurrence and identical morphology of the trunk annuli (Fig. 7.2, 7.3, 7.5, 7.6). UMCU.2014XXSY018 (Fig. 7.1) is ~2.55mm long and 550μm wide, whereas UMCU.2014XSY016 (Fig. 7.4) has a width of 750μm. These specimens are preserved in the Orsten-type pre- servation, and this type of preservation usually includes indivi- duals no larger than 2mm in size, and larger specimens would be fragmented during taphonomy (Maas et al., 2006). Evidently, the original animals that yielded these fragments should have a body length far more than 2mmin size, possibly even centimeter scale.
Phylogenetic perspectives
Pseudooides prima.—Pseudooides prima is reported with only embryonic stages exclusively from the Fortunian Stage of South China (Steiner et al., 2004b; Donoghue et al., 2006b). The infor- mation on P. prima comes exclusively from the outer surface because no internal structures have been discovered yet. The affinity of Pseudooides has been debated for a long time (Donoghue et al., 2015). Steiner et al. (2004b) interpreted the paired compartments as a possible “germ band”, and compared them with the “germ band” of modern arthropod embryos. Based on this assumption, Steiner et al. (2004b) connected the embryos of P. prima and some co-occurring arthropod or arthropod-like fragments in a consecutive ontogenetic sequence. The occurrence of arthropod fossils in the Fortunian Stage is dubious, although a number of SSFs can be interpreted as arthropod fragments (Yuan et al., 2002). However, an arthropod affinity of P. prima is unlikely and was challenged by Donoghue et al. (2006b, 2015) because the anatomy of P. prima is unusual for any modern arthropods. Here, we propose a new hypothesis, namely that the material
of Pseudooides prima is actually synonymous with embryos of the taxon of co-occurring hexangulaconulariids. Hexangulaconulariids exhibit biradial symmetry, and contain two genera: Arthrochites and Hexaconularia (Conway Morris and Chen, 1992). In the Kuanchuanpu Formation of Zhangjiagou section, P. prima co-
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