Semigenetta qiae, Wang & Jiangzuo & Grohé & Chaimanee & Jaeger, 2024

Wang, Xiaoming, Jiangzuo, Qigao, Grohé, Camille, Bonis, Louis de, Chaimanee, Yaowalak & Jaeger, Jean-Jacques, 2024, A review of the Asian Semigenetta Helbing, 1927 (Viverridae, Feliformia, Carnivora) with a description of two new species, Semigenetta qiae n. sp. from South China and Semigenetta thailandica n. sp. from Thailand, Comptes Rendus Palevol 23 (26), pp. 417-432 : 421-424

Semigenetta qiae n. sp.

( Figs 1-5; Table 1)

urn:lsid:zoobank.org:act:C0E3D711-156D-40D1-BD4D-AC1BC105778B

MATERIAL EXAMINED. — Holotype. China. Lufeng, Lufeng Basin , Shihuiba ; IVPP V27106 , partial left dentary with p2-m1 and m2 alveolus.

DIAGNOSIS. — Possessing known diagnostic characters of the genus, Semigenetta qiae n. sp. differs from all other species of the genus in its small size, enlarged anterior and posterior accessory cuspids in lower premolars, slightly more hypocarnivorous lower carnassial with relatively enlarged and more basined m1 talonid and taller metaconid. S. qiae n. sp. has more laterally shifted main cuspids and accessory cuspids in the lower premolars than in S. thailandica n. sp.

REFERRED SPECIMEN. — IVPP V27120 , right maxillary fragment with P4 (broken)-M1 and left maxillary fragment with M1, fragmentary right dentary with posterior root of p3, p4-m1, Lufeng Basin , Yunnan Province .

ETYMOLOGY. — In honor of Professor Qi Guoqin for her contributions to fossil mammals of South China in general and Lufeng fossil site in particular.

TYPE LOCALITY. — China, Lufeng, Lufeng Basin, Shihuiba. IVPP 75033 loc. at 25°13’15”N, 102°03’09”E, about 1 km northwest of the village of Shihuiba and 9 km north of the county of Lufeng at the northern margin of Lufeng Basin ( Dong & Qi 2013) ( Fig. 1). Initial excavations of the fossil site in 1975 were conducted by personnel of the IVPP, Yunnan Provincial Museum, and Lufeng Cultural Heritage Bureau.

GEOLOGY, FAUNA AND AGE. — Discoveries in 1975-1976 of hominoids in a fossil site ( IVPP loc 75033) near the village of Shihuiba a few km from the county of Lufeng ( Xu et al. 1978; Xu & Lu 1979) has attracted much international attention. Multiple excavations ensued in subsequent years in Neogene deposits in the Lufeng Basin, consisting of fluviolacustrine and lignite beds with a thickness of 20-30 m, but fossils being concentrated in a 3-8 m lignite ( Qi 1979; Badgley et al. 1988). Early descriptions of litho- and biostratigraphy of the Shihuiba Formation were attempted ( Qi 1979, 1985b; Chen 1986; Badgley et al. 1988), as well as in more recent years ( Dong & Qi 2013). The paleoecological settings and fossil pollens were also studied (Sun X.-J. & Wu 1980; Badgley et al. 1988).

The Lufeng Basin is controlled by the Xianshuihe-Xiaojiang and Sagaing left-lateral strike-slip fault system, as well as associated dipslip extensions (Wang E.-C. et al. 1998; Li et al. 2015). This fault system mostly runs along the eastern edge of the Tibetan Plateau and a splay of these faults, the Lufeng Fault (F 2 in Li et al. 2015: fig. 1), passes through the Lufeng Basin. Further south at Kaiyuan, activation of the Xiaojiang Faults (F4) was initiated at around 11- 12 Ma, although Paleogene sediments are also present along the fault system ( Li et al. 2015). Several Neogene basins in eastern Yunnan are apparently all controlled by the above fault system, including Yuanmou, Lufeng, Zhaotong, and Kaiyuan basins.

A diverse vertebrate fauna is known in the Shihuiba section, including more than 100 taxa of fishes, reptiles, birds and mammals ( Qi 1979; Dong & Qi 2013). Various carnivorans from Lufeng have been described by Qi and her colleagues ( Qi 1983, 1984, 1985a; 2004, 2006, 2014; Qiu Z.-X. & Qi 1989, 1990, as well as syntheses on Hipparion horse (Sun B.-Y. 2013), suoids ( Han 1983; van der Made & Han 1994), hominoids ( Xu et al. 1978; Xu & Lu 1979; Wu et al. 1983), plus small mammals ( Flynn & Qi 1982).

Based on biochronological assessment of the rhizomyid rodents from Siwalik of Pakistan and Lufeng, Flynn & Qi (1982) estimated an age of c. 8 Ma for the Lufeng Fauna, although this estimate was later revised to be at least 1 million years younger ( Badgley et al. 1988: 179). Recent assessment on the fossil records of the striped rabbits, Nesolagus Forsyth-Major, 1899 , is also consistent with a divergence time of about 7 Ma based on mitochondrial evidence ( Flynn et al. 2019). Two sections at the Lufeng hominoid sites were sampled for magnetostratigraphic studies ( Yue & Zhang 2006). The resulting six normal and six reversed magnetochrons were correlated to part of C3r through C4Bn.1n, spanning c. 5.8-7.6 Ma in GTS2020 calibration ( Raffi et al. 2020). The hominoid-producing lignite beds (including the Semigenetta specimen), however, were restricted to C3An.2n and C3Ar, which is c. 6.2-6.9 Ma in the late Miocene ( Dong & Qi 2013).

DESCRIPTION AND COMPARISON

An associated right P4-M1 and an isolated left M1 are preserved in similar condition as the right lower jaw with p4-m1, with extensive crush on the bones embedded within a dark, lignitic matrix. These are catalogued as a single specimen, IVPP V27120, with similar stage of wear on the teeth, and we treat them as belonging to the same individual.

The right P4 is broken and partially embedded within a crushed bone matrix. Both parastyle and protocone are missing, and the only observable structure is the presence of a narrow lingual cingulum and a carnassial notch that are consistent with a general basal feliform morphology. This narrow cingulum seems to be absent in known records of European species of Semigenetta ( Dehm 1950; Viret 1951; Bonis 1994), although the Hammerschmiede sample apparently has this lingual cingulum at the base of the metastyle as well as on its buccal side ( Kargopoulos et al. 2021).

Both the left and right M1s are broken in the lingual half but the general outlines of the teeth are still intact. A prominent parastyle is the most outstanding feature, as is consistent with upper M1s of Semigenetta , such as S. laugnacensis ( Bonis 1994: fig. 2), S. elegans ( Dehm 1950: fig. 224), S. sansaniensis ( Viret 1951: pl. I, fig. 18b), and a referred specimen (NHMUK M5306) of S. sansaniensis from la Grive-Saint-Alban (Isère), France. Associated with the large parastyle, the paracone is also larger than the metacone. Although not well preserved, the lingual part of the M1s appears to be consisted of a protocone without a surrounding cingulum. Also consistent with European Semigenetta , there is no paraconule and metaconule on M1s.

There is no evidence for the presence of an M2, although the poor preservation of IVPP V27120 makes this less certain. Assuming this is the case, the lack of an M2 is consistent with the diagnosis of Semigenetta .

The left dentary in the holotype (IVPP V27106) is long and slender with relatively uniform depth and minimum tapering toward the anterior end, in contrast to a more distinct subangular lobe in S. huaiheensis (compare Figure 2 and Figure 6). Below the p2, the posterior end of the symphysis is slightly deepened.

The most prominent feature of the lower premolars is their large, discrete, anterior and posterior accessory cuspids, plus a small posterior cingular cuspid. These conspicuously cuspidate premolars are highly distinct and differ from those of other species of Semigenetta . This distinction is particularly striking for the anterior accessory cuspids. This is especially pronounced in the anterior premolars, such as the p2 and p3, which typically have a more diminished accessory cuspid in older and more primitive species of Semigenetta .

The p2 is a slender tooth (see measurements in Table 1) without a cingulid on both lingual or labial sides. It is dominated by the main cuspid, which is positioned toward the buccal side of the tooth and flanked by the anterior and posterior accessory cuspids in lateral view. Of these two cusps, the posterior accessory cuspid is larger and taller-crowned.

The p3 is transitional between p2 and p4, as in most carnivorans. The posterior accessory cuspid in more integrated to the main cuspid as does in the p4. The anterior accessory cuspid, however, is more blade-like.

The p4 features prominently enlarged anterior and posterior accessory cuspids. The anterior accessory cuspid is blade-like, following the anterior ridge of the main cuspid. This structure is apparently dislocated and rotated in the referred specimen, IVPP V27120. The posterior accessory cuspid is also highly integrated into the posterior ridge of the main cuspid, forming a serrated blade. The p4 is also slightly widened at its posterior end, forming a short talonid basin with the posterior cinglular cuspid as its posterior rim, best seen in IVPP V27120. The p4 posterior accessory cuspid is also buccally positioned, which is a character shared with S. thailandica n. sp. from Thailand.

As in Semigenetta sansaniensis from La Grive ( Viret 1951: pl. I, fig. 17c) and from Captieux ( Helbing 1927: fig. 1c), the m1 trigonid of S. qiae n. sp. has a straight shearing blade with the paraconid blade lacking a lingual bend as compared to S. huaiheensis ( Fig. 3). The metaconid is slightly taller than paraconid, whereas most European species have a metaconid equal to or slightly lower than paraconid, as does the Chinese S. huaiheensis .

The main distinction of the lower carnassials (m1s) is its relatively large (both length and width) and basined talonid. Although still narrower than the trigonid, the talonid is relatively wider than those of all other species of Semigenetta . Related to this enlargement of the talonid is the more basin-like structure with about equal size of the hypoconid and entoconid, both of which are ridge-like and enclosing a shallow basin. This slight hypocarnivorous tendency in S. qiae n. sp. is distinguishable from all European species.

A single-rooted m2 alveolus is present in the holotype, but no m2 is preserved in either holotype or referred specimen.