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Peng et al.—Revision of oryctocephalid genra


are all referable to Oryctocarella, showing that Qian’s (1961) paper influenced subsequent work on Arthricocephalus and created confusion about the concepts of both Oryctocarella and Arthricocephalus (see Qian and Lin in Zhou et al., 1977; Yin and Li, 1978; Zhang et al., 1980; Liu, 1982; Ju, 1983; Zhang and Zhou, 1985; Blaker, 1986; Blaker and Peel, 1997; Yuan et al., 2002, 2006; McNamara et al., 2003; Geyer, 2005; Peng et al., 2005a, b). Subsequent synonymization of Oryctocarella with Arthricocephalus (Suvorova, 1964; Shergold, 1969; Blaker and Peel, 1997) apparently stems in part from this broad interpreta- tion of Arthricocephalus. Tomashpolskaya (in Khalfin, 1960, p. 199, pl. 23, fig. 5)


erected a new species, Oryctocara sibirica, and this species was later used (Tomashpolskaya and Karpinski, 1961) as the type species of the new genus Oryctocarella. Suvorova (1964, p. 235) considered the genus to be a junior synonym of Arthricocephalus. This suppression proved to be incorrect and, as revised here, Oryctocarella is revived as an independent genus. Qian and Lin (in Lu et al., 1974) erected a monotypic


subgenus Arthricocephalus (Arthricocephalites) with the new species A.(Arthricocephalites) xinzhaiheensis as its type species. Differential characteristics of the subgenus were not published until six years later. At that time Qian and Lin (in Zhang et al., 1980, p. 275–279) stated that A.(Arthricocephalites) differed from A.(Arthricocephalus) in having a longer palpebral lobe, a narrower fixigena, and a shorter (exsag.) posterior area of the fixigena. As now understood, their concept of A.(Arthricocephalus) is identical with that of Oryctocarella, whereas their concept of A.(Arthricocephalites) is identical with that of Arthricocephalus (as revised here). The unfortunate designation of cranidium E.M. 90001b as


the lectotype of Arthricocephalus chauveaui Bergeron, 1899 by Lane et al. (1988) has led to misunderstanding about the concept of Arthricocephalus.The cranidium is here referred to Oryctocarella duyunensis (Qian, 1961). Some generic names have been mistakenly interpreted as junior synonyms of Arthricocephalus (see Blaker and Peel, 1997; Yuan et al., 2002), and some species have been mistakenly interpreted as Arthricocephalus (see Blaker and Peel, 1997; Yuan et al., 2002; McNamara et al., 2003; Yuan et al., 2006; Geyer and Peel, 2011). Blaker and Peel (1997, p. 109) were unable to determine


any consistent differences between A.(Arthricocephalus) and A.(Arthricocephalites), citing individual variability in the three features identified by Qian and Lin (in Zhang et al., 1980) as differentiating the subgenera. For this reason, Blaker and Peel (1997) suppressed A.(Arthricocephalites) as a junior synonym of Arthricocephalus. However, they included specimens now referable to Arthricocephalus (Blaker and Peel, 1997, fig. 62.1) and Oryctocarella (Blaker and Peel, 1997, fig. 62.2, 62.3) in A. chauveaui, leading to a broad concept of Arthricocephalus that embraces what we now consider to be Arthricocephalus and Oryctocarella. In their 1997 paper, Blaker and Peel also erected a new


genus, Haliplanktos, with Arthricocephalus (Arthricocephalites) jishouensis Zhou in Zhou et al., 1977 as its type species (Blaker and Peel, 1997, p. 112). Haliplanktos, as revised here, is regarded as a junior synonym of Arthricocephalus,and A.(A.) jishouensis is apparently based on a meraspid of A. chauveaui (Lei, 2016, and discussion below).


939 Yuan et al. (2002, p. 120–123) elevated A.(Arthricocephalites)


and A.(Arthricocephalus) to generic rank and did not fully accept Blaker and Peel’s (1997) synonymization of the taxa. They argued that Arthricocephalus differs from Arthricocephalites in having a proportionately wide cranidium with a broad fixigenae; narrow librigenae; a cylindrical glabella; short palpebral lobes; proparian facial sutures; a thorax having a narrow axis and eight to 11 seg- ments; a small (micropygous [or heteropygous; see Kobayashi, 1942]) pygidium with four to five axial rings and well-defined interpleural furrows. In contrast, Arthricocephalites, in their view, is characterized by having a narrower crandium with narrow fix- igenae; wide librigenae; a forwardly expanding glabella; mod- erately long palpebral lobes; a gonatoparian facial suture; a thorax with a relatively wide axis and five to eight segments; a large (isopygous) pygidium with six to eight axial rings and faint or obsolescent interpleural furrows. The concept of Arthricocephalus used by Yuan et al. (2002) equates to that of Oryctocarella as revised here, whereas their concept of Arthricocephalites equates to that of Arthricocephalus as revised here. McNamara et al. (2003) considered A.(Arthricocephalites)


(= Arthricocephalites of Yuan et al., 2002) and Arthricocephalus (sensu Yuan et al., 2002) to be synonymous. Their concept of Arthricocephalus embraced taxa assigned here to both Arthricocephalus and Oryctocarella. The concept of Arthricocephalus used by Geyer and Peel


(2011), being guided by the publication of Lane et al. (1988), equates to that of Oryctocarella as used here. Geyer and Peel (2011) considered Haliplanktos to be a valid genus, whereas as revised here, it is considered to be a junior synonym of Arthricocephalus. Large collections of oryctocephalid trilobites, including


some topotypic material, have been amassed from the Balang Formation in eastern Guizhou and western Hunan onward from about 1961 (see Qian, 1961; Zhou in Zhou et al., 1977; Yin and Li, 1978; Zhang et al., 1980; Yuan et al., 2002, 2006, 2009; McNamara et al., 2003, 2006; Peng et al., 2006; Ma et al., 2011; Lei and Peng, 2014; Lei, 2016), and this material helps to clarify the morphology and characterize the various taxa now under discussion. Together with restudy of Bergeron’s (1899) slab from the Balang Formation of eastern Guizhou, the new material provides clarification about the concept of Arthricocephalus, and leads us to revive Oryctocarella as an independent, well-recognizable genus, and to regard Arthricocephalites and Haliplanktos as junior synonyms of Arthricocephalus.


Validity of Oryctocarella


Tomashpolskaya and Karpinski (1961) erected the genus Oryctocarella (with Oryctocara sibirica Tomashpolskaya in Khalfin, 1960 as the type species) for an oryctocephalid trilobite based on material from the Kuznetsk Alatau of the Altay-Sayan Foldbelt, southwestern Siberia. At that time, at least 10 variously complete exoskeletons were known. Oryctocarella was characterized by having eight thoracic segments (similar to the number of segments in Arthricocephalus chauveaui). The Siberian material appears to be congeneric with material from easternGuizhou that was incorrectly assigned to Arthricocephalus by Qian (1961), leading Suvorova (1964, p. 235) to suppress


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