Chaerilus tessellatus Qi, Zhu & Lourenço, 2005

Tang, Victoria, 2025, Current challenges and preliminary morphological reassessment of the genus Chaerilus Simon, 1877 in China (Scorpiones: Chaerilidae), Euscorpius 406, pp. 1-89 : 24-25

Chaerilus tessellatus Qi, Zhu & Lourenço, 2005

( Tables 1–2) http://zoobank.org/urn:lsid:zoobank.org:act:0C5F0557-

1B6D-4BFE-A2E3-9A2CA9789B39

Chaerilus tessellatus : Qi et al., 2005: 1 , 30–34, 38; Yang, 2008: 8, 46, 48–50, 76; Zhu et al., 2008: 37–38 , 40, 44– 46, 50; Di et al., 2009: 131–133; Di, 2009: 98, 104–106, 193–195; Di & Zhu, 2009: 97, 101; Sun, 2010: 101, 106– 107; Kovařík, 2012: 3; Kovařík & Ojanguren-Affilastro, 2013: 132–133, 141; Di et al., 2013: 52 , 56, 88, 95; Di et al., 2014: 4, 9, 14; Yin et al., 2015: 42, 48, 50; Di et al., 2015: 111; Tang, 2022a: 55; Tang, 2022b: 3, 14; Tang, 2025: 16 .

TYPE MATERIAL ( Qi et al., 2005: 30) [lost]. China, Tibet Autonomous Region, Nyingchi City, Mêdog County, Drepung Township (?), 29°02'N 95°03'E (type locality), 1♀ , MHBU; Nyingchi City, Mêdog County (incorrectly given as “ Bomê County ”), 29°08'N 95°07'E ( Drepung Township ?), 2♀ , MHBU & MNHN; Nyingchi City , Mêdog County, 1♀ , MHBU.

OTHER MATERIAL. China, Tibet Autonomous Region, same locality as holotype, 1 juv. ♀ paratype? ( Yang, 2008: 48); Nyingchi City, Bayi District (incorrectly given as “ Bayi Town to Bomê County ”), Sejila Mountain (“ Mt. Sela ”), 29°37'38.3''N 94°39'28.4''E (approximated), 1♀ , MHBU ( Zhu et al., 2008: 44; Di, 2009: 105); Nyingchi City, Bayi District , Dongjiu Village , 29°49'46.6''N 94°44'35.6''E (approximated), 2 juv. ♀ , MHBU ( Zhu et al., 2008: 44); Nyingchi City, Mainling City , 1 juv. (♀?; Di, 2009: 105) .

MATERIAL EXAMINED. None.

DIAGNOSIS. TL ca. 35.3–51.66 mm for ♀; ♂ unknown. General color dark brown, variegated; chelal manus and telson reddish brown; legs pale brown (MNHN-RS-RS8623). Two pairs of lateral ocelli and one pair of median ocelli. Carapace and tergites smooth or granular (MNHN-RS-RS8623); CAM weakly concave to straight; sternite III –VII smooth, VII tetracarinate. Metasoma I– V with carinae 10-10-10-8-7. PTC 3 (MNHN-RS-RS8623) or 5 in ♀. VADC of cheliceral movable/fixed fingers 6–8/7. Pedipalp chela ChL/W ca. 2.2 in ♀; manus with D 1, D 3(?) – 5, and V 1 , 3 present and granular, E and I obsolete; DSC of movable finger 11, dorsal edge of movable finger straight .

CURRENT ASSESSMENT OF TAXONOMIC VALIDITY. Dubious and pending the designation of a neotype; the status of paratype RS8623 is indeterminate (the specimen on which the minimum TL of 35.3 mm was based was not explained in their description, but it could possibly be this paratype). See also discussions under ‘7. Taxonomic conclusion’.

REMARKS. This species was the second Chaerilus described from China, by Qi et al. (2005). The type series included 4 adult females from Mêdog County, with the type locality allegedly situated in Drepung Township. Qi et al. (op. cit. 30) incorrectly attributed one paratype locality to Bomê County, an error eventually repeated for eight years by Zhu et al. (2008: 44), Di et al. (2009: 133), and Di et al. (2013: 56). It is noteworthy that the Drepung Township (ca. 29°14'15.9''N 95°10'33.7''E) is much closer (ca. 13 km) to the coordinates they provided for this locality than to the type locality (ca. 26 km), which enters Arunachal Pradesh. In his dissertation, Yang (2008: 48) included an additional juvenile female (regarded as a paratype) allegedly collected alongside the holotype, and modified the type locality coordinates to “N 29.11 E 95.10”, which do not even align with the original ones in decimal form (29.03, 95.05). If these new coordinates are in decimal form, they are now closer to Drepung Township (ca. 16 km); if in DMS form (29°11'N 95°10'E), the distance would be even smaller (ca. 6 km). He also added another adult female collected by M.-S. Zhu from “Mt. Sejila” (ϐψϋ山), which seems to be located in Bayi District (originally given as “Bayi Town to Bomê County”). These changes were later adopted by Di (2009: 105) in his dissertation, who documented a new juvenile collected by himself from an unspecified locality in Mainling County. In their redescription of this species, the record from Mt. Sejila was changed into “Bomi County, Mt. Sela” ( Zhu et al., 2008: 44), and two additional female juveniles were reported from Dongjiu Village (Bayi District). All specimens, except for the female “ paratype ” juvenile ( Yang, 2008: 48), and one juvenile from Mainling (Di, 2009: 105), were finally listed in Di et al. (2013: 56).

Problems with this species extend to inconsistencies in its morphological characterization. Qi et al. (2005: 30) described this species based on the female holotype (incorrectly referred to as “male holotype ”) and provided a VADC of 6 for the cheliceral movable finger. Zhu et al. (2008: 44, 47) redescribed this species based on the same specimen but changed the count to 8 again without any explanation, adding a new VADC (7) for the fixed finger. Measurements for the holotype female also differed between the two works; for instance, TL was measured as 48.93 in Qi et al. (2005: 30) but as 51.66 in Zhu et al. (2008: tab. 1). Especially intriguing is their measurement for ChW, whereas Qi et al. (2005: 34) recorded 4.21 mm, Zhu et al. (2008: tab. 1) increased it to 5.22, a substantial difference. This is entirely understandable, yet it simultaneously reinforces my concern regarding the measurement accuracy (reproducibility) in scorpion taxonomy. However, the authors did not give any clarification for their data incongruence. In addition, both Qi et al. (2005: 30, 33) and Zhu et al. (2008: 46–47) recorded and illustrated a pair of pectines each with 5 teeth in the female holotype and suggested no intraspecific variation, but the paratype female (MNHN-RS-RS8623) shows only 3 teeth on either pectine. More recently, Yin et al. (2015: tab. 3) characterized the CAM of this species as “straight”, contradicting with Zhu et al. (2008: 44, “weakly concave”). In the paratype female (RS8623), however, the CAM is very weakly undulate and asymmetrical.

The most prominent discrepancy lies in the qualitative description of tergal granulation, signifying yet another “taxonomic Rashomon effect”—a term coined herein, referring to the phenomenon where different subjective interpretations are derived from the morphology of the same specimen and hence its taxonomic position. For the same specimen, Qi et al. (2005: 30) stated “… Carapace … with densely coarse granules … Tergites are coarsely granular …”, while Zhu et al. (2008: 38, 44, 47) claimed, respectively, “… carapace almost smooth on lateral and posterior margins …”, “… Carapace is almost smooth on lateral and posterior margins … Mesosomal tergites smooth …”, and “… Carapace covered with sparse granules of unequal size on inner portions of lateral carinae almost smooth on lateral and posterior margins … Mesosomal tergites not lustrous and almost smooth …” The stark contradiction in their descriptions, particularly in adjective terms, can be considered diagnostic for different species in some cases. This highlights the subjectivity in qualitative descriptions and underscores the importance of including detailed photographs in species descriptions. After scrutinizing the photograph of the paratype female (RS8623) deposited in MNHN, I corroborate the presence of a large, triangular, relatively smooth area on the lateral sides near the posterior surface on carapace. Current examination reveals that reduction of granulation on the lateral surfaces of carapace is a common condition in Tibetan Chaerilus species. However, only C. tessellatus has been described as such in previous papers ( Table 1), where this character was applied diagnostically. On the other hand, the same photograph shows dense granulation on nearly all tergite surfaces, as indicated by the reflections of those granules. Nonetheless, this could simply imply different conditions present in the holotype and paratype females. Subsequently, Di et al. (2009: 133) characterized this species with even more generalized phrasing in their dichotomous keys as follows (recycled in Di et al. (2013: 88), Di et al. (2014: 14), and Yin et al. (2015: 50)): “… Carapace, tergites nearly smooth in adults …” Similarly, both Qi et al. (2005: 30) and Zhu et al. (2008: 47) implied that sternite VII was “smooth” in this species (at least the holotype female, since they provided no comments on other materials): “… Sternites are smooth; segment VII has two pairs of dentated carinae …”, “… Sternites smooth; sternite VII with two pairs of dentated carinae weakly developed …” However, evident granules can be observed on the lateral sides and posterior region of sternite VII in the paratype female (RS8623). These confusions raise doubts about the accuracy of those authors’ qualitative description.

Despite the above complications, the presence of 11 subrows of denticles on its pedipalp movable finger presumably secures its validity ( Table 1), a count shared only with C. tricostatus (10–12), from which C. tessellatus can be, theoretically, most reliably distinguished by the presence of D 3 ( Yin et al., 2015: tab. 3; but see ‘7. Taxonomic conclusion’). Its distinction from C. pictus , a species recorded with a similar DSC (13–14), is discussed above.

DISTRIBUTION. Drepung Township (“Beibengxiang”) of Mêdog County, Dongjiu Village (“Dongjiucun”) and Sejila Mountain of Bayi District, and Mainling City, in Nyingchi City. However, most localities are dubious, as no descriptions were provided for specimens originating from those regions.