Fontourion Gąsiorek, Morek & Michalczyk, 2024

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 : 57-58

Fontourion Gąsiorek, Morek & Michalczyk gen. nov.

ZooBank registration: urn:lsid:zoobank.org:act:ACDC00E5-6B25-4823-BFE8-79CEA2A9457E

Diagnosis: Cuticle smooth. The AISMs are in the shape of semilunar hooks. Buccal tube is followed by a flexible annulated pharyngeal tube; the pharyngeal annulation is semi-complex (annuli single laterally and forking dorsoventrally). A DABT is present. There is a spherical pharynx, with two macroplacoids and a septulum. Macroplacoids are arranged rhomboidally (◊). Claws are of the Hypsibius type, i.e. asymmetrical both with respect to the sequence of primary and secondary branches (2-1-2-1) and with respect to their size, with external and posterior claws always evidently larger than the internal and anterior claws. Pseudolunulae below claws I–IV may be present; only internal and posterior cuticular bars may be present.

Composition: Fontourion boreale comb. nov., Fontourion brevipes comb. nov., Fontourion glaciale comb. nov., Fontourion islandicum comb. nov., Fontourion recamieri comb. nov. (type species), and Fontourion secchii comb. nov. et nom. inq.

Etymology: The name honours Dr. Paulo Fontoura, an esteemed Portuguese tardigradologist.

Differential diagnosis: Within Pilatobiinae , Fontourion gen. nov., Degmion gen. nov., and Pilatobius possess a pharyngeal tube (absent in Notahypsibius ) but:

• Fontourion gen. nov. has a smooth dorsal cuticle and lacks dorsolateral gibbosities, whereas Pilatobius either exhibits gibbosities and/or its dorsal cuticle is uniformly sculptured throughout the trunk;

• for the distinction with Degmion gen. nov., see above.

Remarks: Large pores used by Buda et al. (2018) to characterize F. islandicum comb. nov. are muscle attachment points that have no taxonomic value. With the exception of F. brevipes comb. nov., the species in the recamieri complex are extremely similar ( Zawierucha et al. 2020), and we are of the opinion that the morphometric differences used to delineate them could result from discrepancies in the morphometry conducted by the various researchers. The species are clearly delineated genetically ( Fig. 1 ), thus until proper redescriptions are performed, species identification in this lineage should rely on DNA barcoding.

Figures

Figure 1. Schematic depiction of six types of cuticular pedal bars and other leg structures found in the Hypsibiidae. Note that the edges of convex pulvini may overlap with fully sclerotized cuticular bars but are generally faint and weakly defined when observed under light microscopy. Historically, these edges of pulvini were sometimes described as ‘bars’ [e.g. see Dastych (1988) for Adropion belgicae or Gąsiorek et al. (2016) for Mesocrista].