New artiopodan euarthropods from the Chengjiang fauna (Cambrian, Stage 3) at Malong, Yunnan, China Zhu, Yuyan Zeng, Han Liu, Yao Zhao, Fangchen Acta Palaeontologica Polonica 2023 2023-09-08 68 3 427 440 Chen, Ramskold, Edgecombe, and Zhou Chen, Ramskold, Edgecombe, and Zhou Xandarellida 1 428 order  Genus  Zhugeianov.  Table 1. Measurements (in mm) of thoracic tergites of  Zhugeia acuticaudata gen. et sp. nov., based on holotype NIGP 200049.  ZooBank LSID: urn:lsid:zoobank.org:act: 10C13356-3E01-4721-9C8E- 5E30E3097946    Thoracic tergite number Width Length  t4 20 1.9  t5 18 1.9  t6 17 2.2  t7 16 2.4  t8 13 2.5  t9 11 3.5  Type species:  Zhugeia acuticaudata gen. et sp. nov.; see below, by monotypy.  Etymology: For the Zhuge Mountain where the Kuangshan section is located and where the respected prime minister Liang Zhuge of Shu- Han once camped at about 225 A.D. during the Three Kingdoms Period of ancient China.  Diagnosis.—Semi-elliptical cephalon with a pair of genal spines. A pair of ovoid lateral eyes near anterior margin of cephalon. Cephalon posteriorly covering two thoracic tergites. Nine partially overlapping tergites with pleural spines. Micropygous pygidium with two small lateral spines and an elongated needle-like median spine.  Remarks.—The order Xandarellidais diagnosed by the semicircular cephalic shield with stalk lateral eyes which extend posteriorly to cover multiple thoracic tergites and pygidium with broad median spine ( Chen et al. 1996; Ramsköld et al. 1997; Chen et al. 2019).  Zhugeiacomplies with the diagnosis of Xandarellida, such as a cephalic shield covering at least two thoracic tergites and pygidium with a median spine.  Zhugeiadiffers from the other xandarellids in various aspects (see more details in the Remarks of species). Thus,  Zhugeiais a new genus of Xandarellida.   Zhugeia acuticaudata gen. et sp. nov. Fig. 1.  ZooBank LSID: urn:lsid:zoobank.org:act: 224B5712-741A-44A1-B750- 1D6EDFAF5705  Etymology: From Latin acutispinous and caudata, tail.    Holotype: NIGP 200049, specimen preserving most part of exoskeleton, part only (Fig. 1).  Type locality: Kuangshan section, Malong, Yunnan, China.  Type horizon: Maotianshan Shale Member, Yu’anshan Formation,  Wutingaspis–EoredlichiaTrilobite Zone, Cambrian Series 2, Stage 3.  Material.— Typematerial only.  Diagnosis.—As for the genus.  Description.—Suboval exoskeleton consists of cephalon, thorax, and pygidium, measuring 49 mmlong (including the median spine on pygidium) and 23 mmwide. Cephalon is semi-circular. Anterior margin of cephalon is rounded, and posterior margin is approximately straight (Fig. 1A 3: ce). A pair of broad genal spines reach posteriorly to the third thoracic tergite, measuring 19 mmlong and 23 mmwide (Fig. 1A 3, D: gs). Two long ovoid lateral eyes are situated near the anterior margin of cephalon (Fig. 1A 3, B, C: e). Cephalon extends posteriorly to cover two anteriormost thoracic tergites (Fig. 1A 3, E: ct1, ct2). Cephalon excluding genal angles occupies approximately one-third of whole-body length. Except for two anteriormost thoracic tergites covered by cephalon, thoracic region, measuring 17 mmlong, consists of nine partially overlapping tergites. Tergites of thorax have overlapping areas. The average overlapping area accounts for about one-fourth to one-third of the sagittal length of the tergite. The first six thoracic tergites, which are almost equal in sagittal length, have nearly straight posterior margins (Fig. 1E: t1–t6). The last three thoracic tergites, which are progressively longer in sagittal length, are curved posteriorly (Fig. 1F: t7–t9, Table 1). Anterior thoracic tergites are almost as wide as cephalon. The fourth thoracic tergite is the broadest with maximum width of 19 mm, and following tergites narrow toward the rear. Lengths of pleural spines of thoracic tergites increase towards pygidium. Pygidium is situated within a notch formed by pleural spines of posteriormost thoracic tergite. Teardrop-shaped pygidium, measuring 16 mmlong including pygidial spine, bears a pair of triangular posterolateral pygidial spines and an elongated needle-like median pygidial spine. Median pygidial spine is slightly longer than main part of pygidial tergite (Fig. 1A 3, G: ms; Fig. 1A 3, H: ls).  Remarks.—Four genera have been erected in the order Xandarellida, including  Xandarella Hou, Ramsköld, and Bergström, 1991,  CindarellaChen, Ramsköld, Edgecombe, and Zhouin Chen et al., 1996,  Luohuilinella Zhang, Fu, and Dai, 2012, and  Sinoburius Hou, Ramsköld, and Bergström, 1991. The cephalon of Xandarellidashows marked morphological variations.  Zhugeiahas a pair of broad genal spines similar to  Sinoburius( Hou and Bergström 1997; Chen et al. 2019), while  Xandarellaand  Luohuilinellahave acute genal angles rather than genal spines ( Hou and Bergström 1997; Zhang et al. 2012; Hou et al. 2018), and  Cindarellahas rounded genal angles ( Ramsköld et al. 1997). As in  Xandarella,  Sinoburius, and  Cindarella,  Zhugeialacks the anterolateral eye notches typical of  Luohuilinella( Zhang et al. 2012; Hou et al. 2018). Regarding eyes,  Zhugeiashares anteroventral lateral eyes that are incorporated into the dorsal cephalic shield with  Xandarellaand  Sinoburius, in contrast to a pair of lateral stalked eyes positioned at the anterolateral cephalic margin in  Luohuilinellaand  Cindarella( Ramsköld et al. 1997; Zhang et al. 2012; Hou et al. 2018; Chen et al. 2019).  Zhugeiahas no eye slits associated with eyes that are present in  Xandarella( Hou and Bergström 1997). Other xandarellids exhibit different thoracic morphology from that of  Zhugeia. The number of thoracic tergites of  Zhugeia(9 tergites) is more than that in  Sinoburius(7 tergites) and less than those in  Xandarella(10 tergites),  Cindarella(17 tergites), and  Luohuilinella(27–30 tergites) ( Hou and Bergström 1997; Ramsköld et al. 1997; Zhang et al. 2012; Hou et al. 2018; Chen et al. 2019). As in  Xandarella,  Luohuilinella, and  Cindarella, the anteriormost thoracic tergites of  Zhugeiaare almost as wide as the cephalon ( Hou and Bergström 1997; Ramsköld et al. 1997; Zhang et al. 2012; Hou et al. 2018), while the anteriormost thoracic tergites of  Sinoburiusare narrower than the cephalon ( Hou and Bergström 1997; Chen et al. 2019). In addition, the first thoracic tergite of  Zhugeiais narrower than successive tergites, like  Sinoburius( Chen et al. 2019). Thoracic tergites of  Zhugeianarrow toward the rear, as shown in  Xandarella,  Cindarella, and  Luohuilinella( Hou and Bergström 1997; Ramsköld et al. 1997; Zhang et al. 2012; Hou et al. 2018), while in  Sinoburiusfirst thoracic tergite is the narrowest ( Hou and Bergström 1997; Chen et al. 2019). Although all known members of Xandarellidahave micropygous pygidium, their pygidia still show distinctions. Relative to width of cephalon, pygidium of  Zhugeiais similar to that of  Xandarellaand is narrower than that of  Sinoburius( Hou and Bergström 1997; Chen et al. 2019).  Zhugeiahas a dorsal needle-like spine like  Xandarellainstead of the broad median spine of  Sinoburius( Hou and Bergström 1997; Chen et al. 2019). The micropygous pygidia of two species of  Luohuilinellaare smallest among xandarellids ( Zhang et al. 2012; Hou et al. 2018). A terminal spine is recognized in  L. deletres( Hou et al. 2018), but other pygidial morphologies of  Luohuilinellaare unclear ( Zhang et al. 2012; Hou et al. 2018). Among xandarellids, only  Cindarellalacks median pygidial spine ( Ramsköld et al. 1997). As in  Xandarellaand  Cindarella,  Zhugeiahas a pair of small lateral spines, while  Sinoburiushas two pairs of lateral spines ( Hou and Bergström 1997; Ramsköld et al. 1997; Chen et al. 2019).  Stratigraphic and geographic range.— Typelocality and horizon only. Order and family incertae sedis Genus  Tonglaiianov.  ZooBank LSID: urn:lsid:zoobank.org:act: DA8A8456-AB77-4C7A-AB 23-336517CD1EDE  Etymology: After Tonglai, an ancient name of Malong where the fossil was discovered.  Type species:  Tonglaiia bispinosa gen. et sp. nov.; see below, by monotypy.  Diagnosis.—Elliptical cephalon with a pair of marginal cephalic spines. Two oval eyes situated near the anterior margin of cephalon. Seven partially overlapping tergites with posterolateral marginal spines. Micropygous pygidium with a pair of posteriormost triangular spines.  Remarks.—The dorsal eyes of  Tonglaiiaare located in an anterior position which is similar to the aglaspidid counterparts. However, the cephalon of  Tonglaiiahas a rounded genal area and a unique pair of lateral marginal spines, lacking the characteristic genal spines of aglaspidids. The posterior margin of pygidium is intact, showing no evidence of the diagnostic tailspine in aglaspidids. Additionally, cuticle of  Tonglaiiais non-biomineralized, another obvious difference from aglaspidids. With these distinctions,  Tonglaiiadoes not comply the diagnosis of Aglaspididaand Vicissicaudata( Lerosey-Aubril et al. 2017). The presence of pygidium in  Tonglaiiais a typical character of trilobitomorph artiopodans ( Ortega-Hernández et al. 2013), but  Tonglaiiais distinguished from other trilobitomorphs in several aspects, such as a suboval cephalon with special lateral marginal spines and a micropygous pygidium with two posterior spines. Therefore,  Tonglaiiarepresents a new genus (see details in the remarks for the typespecies below). NIGP 2 429 NIGP 200049 1 holotype