Diphascon rugosum (Bartos, 1935)

Gąsiorek, Piotr, Blagden, Brian, Morek, Witold & Michalczyk, Łukasz, 2024, What is a ‘ strong’ synapomorphy? Redescriptions of Murray’s type species and descriptions of new taxa challenge the systematics of Hypsibiidae (Eutardigrada: Parachela), Zoological Journal of the Linnean Society 202 (1), pp. 1-63 : 47-49

publication ID	https://doi.org/ 10.1093/zoolinnean/zlad151
publication LSID	lsid:zoobank.org:pub:044A402-2A0F-4135-9410-7DE081CB11C4Corresponding
persistent identifier	https://treatment.plazi.org/id/03AF87C4-A617-FF82-AE37-6B12FB5E8CB1
treatment provided by	Plazi
scientific name	Diphascon rugosum
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D. rugosum View in CoL ; various locales, Poland; Dastych (1988).

Material examined: 40 individuals in total (for details, see Supporting Information, Table S1).

Description: Body small to medium in size ( Table 13), corpulent ( Fig. 38A View Figure 38 ) and white. Cuticle uniformly sculptured on the entire dorsal surface by polygons of various sizes placed tightly adjacent to each other ( Fig. 38B, C View Figure 38 ); legs smooth. Cribriform areas not visible under PCM. Legs short, plump, and barely delimited from the trunk ( Fig. 38A View Figure 38 ). Eyes present in living animals, but usually quickly dissolving in Hoyer’s medium. Buccopharyngeal apparatus of the Pilatobius type, with a short pharyngeal tube ( Fig. 38D View Figure 38 ). The OCA not visible under PCM ( Fig. 38D View Figure 38 ). Furcae of the Hypsibius type. The DABT large and slightly elongate. Pharynx circular, with large pharyngeal apophyses. Macroplacoid length sequence 2 <1, the first with a delicate central constriction ( Fig. 38D View Figure 38 ). Septulum large, but clearly shorter than the second macroplacoid.

Claws of the Hypsibius type, with external and internal claws of similar size ( Fig. 39 View Figure 39 ). Accessory points slightly divergent. All claw bases distinctly narrowed, but especially the anterior claws, which have calyx-like bases ( Fig. 39B, D View Figure 39 ). Pseudolunulae absent. Cuticular bars present and of three types: (i) internal, long thickenings terminating at the claw I–III bases ( Fig. 39A View Figure 39 ); (ii) anterior and (iii) posterior short rods ( Fig. 39B View Figure 39 ). All cuticular bars are undetectable in SEM ( Fig. 39C, D View Figure 39 ).

Remarks: Currently, there are two discriminative traits separating P. rugosus and P. iltisi ( Schuster & Grigarick, 1965) : the presence of deep transverse cuticular folds in P. iltisi and, according to Bartoš (1935) and Schuster and Grigarick (1965), the diameter of the polygonal granules that constitute the sculpturing increasing posteriorly in P. rugosus but not in P. iltisi . These cuticular folds could be a result of the preparation technique [see ‘Remarks’ on P. sexbullatus ( Ito, 1995) ]. The dorsal sculpturing in our examined population does not agree with the original description but conforms to specimens identified as P. rugosus by Dastych (1988), thus indicating that resampling in the Turiec Basin is needed to verify the true morphotype of P. rugosus . General claw morphology is similar in P. rugosus , P. recamieri (Richters, 1911) (see Gąsiorek et al. 2017), and P. secchii ( Bertolani & Rebecchi, 1996) nom. inq. ( Fig. 42E View Figure 42 ). Sculpture of P. ramazzottii ( Robotti, 1970) is similar to that of P. rugosus ; however, the polygons are larger and closer to each other ( Fig. 42F View Figure 42 ). Within the rugosus group (species with the entire dorsum covered by sculpturing and lacking dorsal gibbosities), four other species are gathered: P. granifer ( Greven, 1972) , P. latipes ( Mihelčič, 1955) sp. dub., P. procerus ( Pilato et al., 2014) , and P. ziliense ( Lisi et al., 2014) . Of these, Dastych (2015) has already expressed doubts regarding the validity of P. latipes , with which we concur. P. granifer differs from P. rugosus by a completely dissimilar type of sculpturing [irregular small polygons in P. rugosus vs. large polygons resembling the caudal sculpturing of some species of the Ramazzottius oberhaeuseri ( Doyère, 1840) complex, but clearly larger and with a conspicuous light centre in P. granifer ; see Fig. 42G View Figure 42 ]. Unfortunately, other differences cannot be given, because the description of P. granifer is insufficient, and the type material lost (H. Greven, pers. comm.). In our opinion, both P. procerus and P. ziliense are poorly differentiated from P. rugosus and require further investigation. P. nodulosus is distinguished from P. rugosus by its dissimilar type of sculpturing: very large polygons in the caudal zone ( Fig. 42D View Figure 42 ), with the size of the polygons subsequently decreasing anteriorly. The internal and anterior claws of the former species are also more massive ( Fig. 42C, D View Figure 42 ), rectangular bars are present below claws ( Fig. 42C, D View Figure 42 ), and claws IV have evident pseudolunulae ( Fig. 42D View Figure 42 ).