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Journal of Paleontology 92(3):478–487
offset at breaks. Themostly dorsal attitude of preservationmay be due to the millipede being flattened, or simply due to the lack of strong coiling. Strong coiling, even if partial, results in preserva- tion of fossil millipedes in lateral view. Specimen LPI-63009 has 21 segments, most of which are similar in length. It lacks diag- nostic features, but is described here for the sake of completeness.
Methods.—The specimens were photographed with a Leica M125 stereo-microscope using a Leica DFC295 digital camera in the Chengdu Center of China Geological Survey (CDCGS), Chengdu, China, and photographed in more detail by a VH- Z20R digital camera with the Keyence three-dimensional ima- ging system in the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of Beijing. Micro-ornamentation was scanned by scanning electron microscope (SEM) using the Zeiss EVO-MA25 in IVPP.
Repository and institutional abbreviation.—Specimens are deposited at the Chengdu Center of China Geological Survey (CDCGS), (LPI=Luoping invertebrates).
Systematic paleontology
Class Diplopoda Blainville in Gervais, 1844 Subclass Helminthomorpha Pocock, 1887 Superorder, Order, and Family incertae sedis
Remarks.—Characters present do not allow confident assign- ment to any extant or extinct order of millipedes, but the seg- ment number (39), ring structure (sternites not fused to the pleurotergites), large head, simple collum that does not cover the head, and presence of a pair of pits on the lateral swellings of the metazonites that may have been insertion points for setae, suggest a nematophoran affinity, although a colobognath affi- nity cannot be ruled out. A distinct midline is lacking however; therefore this taxon is not assigned to the Nematophora. A nematophoran, specifically calipodidan, affinity has been sug- gested for Hannibaliulus wilsoniae Shear, Selden, and Gall, 2009 (Shear et al., 2009; Edgecombe, 2015, p. 347), which is a form that bears some resemblance to Sinosoma n. gen.
Genus Sinosoma Huang and Hannibal new genus
Type species.—Sinosoma luopingense new genus new species, by original designation and monotypy.
Diagnosis.—Millipedes with 39 body segments, including a small collum. Metazonites divided by grooves into three transverse parts that are flanked laterally by narrow, suboval swellings bearing a pair of posterolateral pits (?spine bases). Sternites free. Legs of medium length, stout.
Etymology.—The generic name is derived from the stem Sino-, meaning “pertaining to China,” in reference to the coun- try where the specimen was collected. The ending -soma (Greek for body [soma, neuter]) is a common ending for millipedes that has the advantage of not implying membership in a particular millipede order.
Occurrence.—The upper thin-bedded unit of the Luoping biota, Member II of the Guanling Formation, Anisian, Middle Triassic. Luoping County, Yunnan Province, southwest China.
Remarks.—Sinosoma n. gen. is similar to Hannibaliulus Shear, Selden, and Gall, 2009, which also has an elongate body, a large number of the body segments, lateral features that might be interpreted as swellings, and a small collum that does not cover its head. Segment number differs (39 versus up to 44) as well as the number of transverse grooves on the metazonites (two versus one). Sinosoma n. gen. also bears a pair of distinctive posterolateral pits on its swellings, a feature that Hannibaliulus lacks.
Sinosoma luopingense Huang and Hannibal new species Figures 2, 3
Holotype.—Specimen LPI-61593. Diagnosis.—As for genus.
Occurrence.—The upper thin-bedded unit of the Luoping biota, Member II of the Guanling Formation, Anisian, Middle Trias- sic. Luoping County, Yunnan Province, southwest China.
Description.—Medium-sized millipede, ~19mm long, elongate with 39 segments, inclusive of collum and telson (epiproct). Most segments more-or-less uniform in width, widest midbody segments ~1 mm wide as preserved, reconstructed width slightly more than 1mm; first few body segments at anterior tapering anteriad, last few segments tapering posteriad. Prozo- nites well exposed, exposed length up to 0.18mm, metazonites up to 0.38mm long. Ratio of exposed length of prozonites (excluding anteriormost and posteriormost segments) to length of metazonites ranging from ~34% to 50%, indicating that prozonites were probably well exposed in life (although not quite as exposed in the fossil, since the specimen is relaxed). Penultimate segment reduced in length. Head medium sized, triangular in shape as preserved, but
difficult to interpret because of twisting from dorsal position and crushing (oval missing area on right side is the result of preparation). Parts of gnathocliarium(?) exposed below head, slightly displaced. Antennae swollen, club-shaped, at least five antennomers preserved on ?right antenna (Fig. 3.1), the third and fourth of which are the largest. Collum small, not covering head, quadrangular, slightly smaller than metazonite of
Figure 2. Sinosoma luopingense n. gen. n. sp., holotype, from the Middle Triassic Guanling Formation. Specimen LPI-61593, mostly in dorsal view. (1) Entire millipede after preparation; (2) explanatory drawing of holotype; (3) anterior, showing the antenna, head, collum, metazonite, prozonite, and lateral swellings (?paranota); (4) segments toward anterior, including what may be sutures, but are more likely cracks; (5) segments toward posterior with preserved appendages, free sternites below lateral swellings (?paranota), and a transverse groove identified; (6) posterior of millipede, with telson, lateral swellings (?paranota), and transverse grooves on a pleurotergite identified. (an=antenna, ap=appendages, c=collum, cr=crack, ls=lateral swelling (?paranotum), h=head, mz=metazonite, pz=prozonite, st=sternite, t=telson, tg=transverse groove).
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