Tonglaiia bispinosa, Zhu & Zeng & Liu & Zhao, 2023
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publication ID |
https://doi.org/ 10.4202/app.01080.2023 |
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persistent identifier |
https://treatment.plazi.org/id/038B87F0-2F52-D345-6C27-FCCCFC09BF03 |
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treatment provided by |
Felipe |
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scientific name |
Tonglaiia bispinosa |
| status |
gen. et sp. nov. |
Tonglaiia bispinosa gen. et sp. nov.
Fig. 2 View Fig .
ZooBank LSID: urn:lsid:zoobank.org:act:259646CE-8087-4865-BA77-CEE7E47CD387
Etymology: From Latin, bi, double and spinosa, spinous.
Holotype: NIGP 200050 View Materials , specimen preserving complete cephalon and most part of thorax and abdomen, part only ( Fig. 2 View Fig ).
Type locality: Kuangshan section, Malong, Yunnan, China.
Type horizon: Maotianshan Shale Member, Yu’anshan Formation, Wutingaspis –Eoredlichia Trilobite Zone, Cambrian Series 2, Stage 3.
Material.— Type material only.
Diagnosis.—As for the genus.
Description.—Oblong exoskeleton, measuring 27 mm long and 19 mm wide, is composed of cephalon, thorax, and pygidium.
Cephalon is subelliptic to subrectangular, measuring 11 mm long and 16 mm wide ( Fig. 2A View Fig 3 View Fig : ce). Anterior margin of cephalon is rounded, and posterior margin is approximately straight. Cephalon has a pair of triangular marginal spines located almost halfway on cephalic lateral margin ( Fig. 2A View Fig 3 View Fig , C, D: cs). Two rimmed oval eyes are located close to anterior cephalic margin ( Fig. 2B View Fig : e). A pair of flap-like structures, presumably appendages, are present beyond cephalon lateral margins ( Fig. 2E View Fig : ap?). Some marginal lines can be found around cephalon ( Fig. 2C, D View Fig : ml). The numerous wrinkles near the anterior and lateral cephalic margins indicate convexity of cephalon.
Thorax consists of seven partially overlapping tergites with subequal sagittal lengths, measuring 15 mm long. For
→ Fig. 1. Artiopodan euarthropod Zhugeia acuticaudata gen. et sp. nov. from the Cambrian Stage 3 Chengjiang fauna at Malong, Yunnan, China; holotype NIGP 200049 View Materials . A. Whole specimen, under high-angle light (A 1), inverted red channel image (A 2), interpretative drawing (A 3). B. Right eye. C. Left eye. D. Left genal spine. E. Thoracic tergites under low-angle light (E 1), under high-angle light (E 2). F. Sixth to ninth thoracic tergites under low-angle light (F 1), under high-angle light (F 2). G. Median pygidial spine under low-angle light (G 1), under high-angle light (G 2). H. Lateral pygidial spine under low-angle light (H 1), fluorescence photograph under 532 nm green laser (H 2). Abbreviations: br, bradoriid; ce, cephalon; ct1–ct2, thoracic tergite number covered by cephalon; e, eye; gs, genal spine; ls, lateral pygidial spine; ms, median pygidial spine; py, pygidium; t1–t9, thoracic tergites .
the first to fourth thoracic tergites, overlapping area between adjacent tergites accounts for about one-fifth of the sagittal length of tergite. Overlapping area among last three thoracic tergites is approximately one-third of the sagittal length of the tergite. Thoracic tergites gradually curve backwards. Widths of first two tergites are close, approximately 19 mm wide ( Fig. 2A View Fig 3 View Fig : t1–t3; Table 2), and widths of more posterior thoracic tergites are narrowing towards rear ( Table 2). Pleural angles of the first six thoracic tergites exhibit a similar shape absent elongate spine. Pleural angle of the last thoracic tergite forms a spine towards the pygidium ( Fig. 2G View Fig : pa). Pleural angles of thoracic tergites have numerous tiny marginal spines ( Fig. 2F View Fig : sp).
Pygidium is micropygous and subrectangular in shape measuring 3 mm long and 4 mm wide ( Fig. 2A View Fig 3 View Fig : py; G: py, ts). Width of pygidium is slightly narrower than that of posteriormost thoracic tergite. Posterior pygidial margin bears a pair of closely spaced robust triangular spines that form a notch between pygidial spines, measuring approximately 1 mm wide. Margin of notch is smooth and featureless.
Remarks.—The cephalic spines present in most of non-trilobite artiopodans are located at the genal angles ( Hou and Bergström 1997), but Tonglaiia has its cephalic marginal spines placed halfway on the cephalon. The teardrop-shaped lateral eyes that form bulges on the anterior cephalic shield are analogous to the helmetiid counterparts, such as Helmetia , Kuamaia , and Saperion , but Tonglaiia bears no anterior sclerite associated with eyes in helmetiids ( Hou and Bergström 1997; Edgecombe and Ramsköld 1999). Among trilobitomorphs, the extensive overlapping of thoracic tergites in Tonglaiia is most comparable to that of xandarellids ( Hou and Bergström 1997). The micropygous pygidium is found in most xandarellids and some other trilobitomorphs like Zhiwenia and Longquania , and the pygidium with a pair of posteriormost spines is shared by Tonglaiia and Longquania ( Luo et al. 2008; Hu et al. 2013; Du et al. 2018). The difference is that the notch formed by the pygidial spines in Tonglaiia is smooth, but the notch in Longquania bears serrated spines ( Luo et al. 2008; Hu et al. 2013). In addition, phylogenetic analyses suggest that the evolutionary affinity of Tonglaiia is uncertain (see below).
Stratigraphic and geographic range.— Type locality and horizon only.
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