Actual State of Knowledge of the Limno-Terrestrial Tardigrade Fauna of the Republic of Argentina and New Genus Assignment for Viridiscus rufoviridis (du Bois-Reymond Marcus, 1944)

Abstract

Limno-terrestrial tardigrades of Argentina had been studied starting in 1908 and for a long time by European researchers, most frequently in the Patagonian region (incl. the Land of Fire). Starting during the 1980s, Claps, Rossi and collaborators published many surveys, studying other regions also, but with taxonomic criteria at that time. Since the 2000s, methodical and continuous studies using more modern criteria, have been carried out at the National University of La Pampa, contributing to the faunistic, taxonomic and ecological knowledge (including new species descriptions). This paper provides a comprehensive list of the limno-terrestrial tardigrade fauna reported from Argentina, with pertinent evaluations, owing to a careful study of every pertinent piece of literature since 1908, also solving some problems of discordance between the main past checklists. Summarizing, 39 genera and 119 species are present; of these, 72 represent records accepted by the literature, while 47 are records questioned in the literature but which represent distinct taxa surely present in Argentina; 14 additional taxa, instead, are clearly dubious. The authors also report the correct genus assignment to Viridiscus rufoviridis (du Bois-Reymond Marcus, 1944), which now becomes Barbaria rufoviridis comb. nov.

1. Introduction

The phylum Tardigrada consists of over 1400 species [1] that inhabit terrestrial, freshwater and marine environments throughout the world. In terrestrial habitats they live primarily in mosses, lichens, leaf litter and soil, whereas in freshwater and marine environments tardigrades are found mainly in sediments and on aquatic plants [2].

The present paper is focused on limno-terrestrial tardigrades, and it is possible to suggest how much taxonomic investigations have increased during the last decade by comparing the “Actual checklist of Tardigrada species” published in 2013 [3] with the most updated one of 2022 [1]: the number of valid limno-terrestrial species has increased from 876 to 1067 units (+191 units, i.e., +21.8%); additionally, this corresponds to increased activity of new species descriptions: taking the data from the ultimate checklist [1], in 2011, 22 new limno-terrestrial species were described, while in 2021, 39 new limno-terrestrial species were described, which results in an increase of 77.3%.

Taxonomists use species checklists as tools to communicate information on species diversity and distribution. These checklists are often a starting point for biodiversity-related analyses, from ecological studies to conservation plans. The protection of biodiversity is one of the relevant issues in global conservation. However, coherent conservation cannot take place if the species involved are unknown [4].

The Argentine limno-terrestrial tardigrade fauna was studied in the beginnings (starting in 1908) and for a long time by European researchers [5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27], with the only exception of Schuster [28] (an author from California, USA). Those studies regarded most frequently the Patagonian region (incl. the Land of Fire). In the 1980s and 1990s, Argentine researchers Claps, Rossi and collaborators [29,30,31,32,33,34,35,36] began to study and report findings of different species in provinces of the country such as Río Negro, Neuquén, Chubut, Tierra del Fuego, Tucumán, Salta and Corrientes. However, those studies were affected by what is now considered out-of-date taxonomy and zoogeography for tardigrades. Since the 2000s and until currently, methodical, continuous studies have been carried out in the framework of various scientific projects at the National University of La Pampa (UNLPam), with major focus on the Provinces of Salta, La Pampa, Buenos Aires, Santa Fé and Río Negro [37,38,39,40,41,42,43]. Since then, we have tried to contribute to the knowledge of the limno-terrestrial tardigrade fauna (including new species descriptions) and provide information about ecology (distribution, preference, population dynamics), using modern taxonomic and biogeographic criteria, owing to all the recent taxonomic novelties.

To date, the previous checklists of tardigrade species of Argentina are due to Rossi and Claps [34], McInnes [44], Claps et al. [35], Meyer [45] and Kaczmarek et al. [46].

This paper provides an updated comprehensive list of limno-terrestrial tardigrade fauna reported from Argentina, their distribution in the country and the references for the records. Species with locus typicus in Argentina, specifying if endemic, are also indicated separately.

The present paper also reports the correct genus assignment to Viridiscus rufoviridis (du Bois-Reymond Marcus, 1944), owing to the discovery of this species, or an extremely similar one, in Argentina [37,38,47]; the Argentine species (reported with “cf.” for caution) proved to belong not to the genus Viridiscus Gąsiorek & Michalczyk, 2019, in Gąsiorek et al. [48] but instead to Barbaria Michalczyk, Gąsiorek, Morek & Stec, 2019, in Gąsiorek et al. [48], thus becoming Barbaria cf. rufoviridis comb. nov.; as a consequence, the former V. rufoviridis is transferred to the genus Barbaria.

2. Materials and Methods

To build our checklist, we consulted all 42 papers (see Table 1) reporting species records (with or without a checklist) from Argentina, plus the past checklists by McInnes [44], Meyer [45] and Kaczmarek et al. [46]; the taxonomic nomenclature was obtained from Degma and Guidetti [1], together with the taxonomic status of currently valid species (excluding those in the situation of species dubia or inquirenda, and nomen dubium or inquirendum).

The map that provides the distribution of tardigrade species in Argentina (Figure 1) was generated through SimpleMappr [49] using the layers of “country” and “state/province”. Whenever possible, locations were extracted from the literature, which resulted in 143 records; when the original coordinates of the location were not provided, they were estimated using Google Earth Pro (ver. 7.3.4.8642 (64-bit)).

Table 1. List of valid species reported in Argentina from the literature. Status (record reliability): + = species reported with certainty; + * = species that need a diagnosis confirmation but each one representing a separate taxon from any other in Argentina; N = dubious record that cannot be taken into consideration because it may coincide with other species in the list. Province abbreviations: BA = Buenos Aires; CB = Córdoba; CH = Chaco; CR = Corrientes; CT = Chubut; ER = Entre Ríos; JY = Jujuy; LP = La Pampa; MI = Misiones; NQN = Neuquén; RN = Río Negro; SA = Salta; SC = Santa Cruz; SF = Santa Fé; SJ = San Juan; TF(IAS) = Isla de Atlántico Sur; TF(SS) = Tierra del Fuego; TU = Tucumán.

Order, Family	Species/Subspecies	Status (Record Reliability)	Province	Report for Argentina
Echiniscoidea, Echiniscidae	Antechiniscus jermani Rossi & Claps, 1989	+	RN	[33]
Echiniscoidea, Echiniscidae	Antechiniscus lateromamillatus (Ramazzotti, 1964)	+	NQN	[36]
Echiniscoidea, Echiniscidae	Barbaria bigranulata (Richters, 1907)	+	BA; ER; CR; MI; TU; SA; NQN; RN; CT; SC; TF(SS)	[8,9,13,15,29,30,31,32,33,36]
Echiniscoidea, Echiniscidae	Barbaria charrua (Claps & Rossi, 1997)	+	MI; TU	[8]
Echiniscoidea, Echiniscidae	Barbaria jenningsi (Dastych, 1984)	+	TF(IAS)	[35]
Echiniscoidea, Echiniscidae	Barbaria madonnae (Michalczyk & Kaczmarek, 2006)	+	CT	[8]
Echiniscoidea, Echiniscidae	Barbaria ollantaytamboensis (Nickel, Miller & Marley, 2001)	+	SA	[8]
Echiniscoidea, Echiniscidae	Barbaria paucigranulata Wilamowski, Vončina, Gąsiorek & Michalczyk, 2022	+	SA	[8]
Echiniscoidea, Echiniscidae	Barbaria cf. rufoviridis comb. nov. (du Bois-Reymond Marcus, 1944)	+ *	BA; LP; SF	[37,38,47]
Echiniscoidea, Echiniscidae	Barbaria weglarskae Gąsiorek, Wilamowski, Vončina & Michalczyk, 2022	+	SC	[8]
Echiniscoidea, Echiniscidae	Bryodelphax parvulus Thulin, 1928	+ *	RN	[16,17]
Echiniscoidea, Echiniscidae	Claxtonia capillata (Ramazzotti, 1956)	+ *	TU; RN; CT	[29,30,33]
Echiniscoidea, Echiniscidae	Claxtonia corrugicaudata (McInnes, 2010)	+	RN	[27]
Echiniscoidea, Echiniscidae	Claxtonia marginopora (Grigarick, Schuster & Nelson, 1983)	+	SC	[13]
Echiniscoidea, Echiniscidae	Claxtonia wendti (Dastych, 1984)	N	RN; CT; SC; TF(SS)	[10,13,29]
Echiniscoidea, Echiniscidae	Cornechiniscus lobatus (Ramazzotti, 1943)	+	SA	[50]
Echiniscoidea, Echiniscidae	Echiniscus aonikenk Gasiorek, Bochnak, Vončina & Michalczyk, 2021	+	CT	[51]
Echiniscoidea, Echiniscidae	Echiniscus arctomys Ehrenberg, 1853	N	RN	[9]
Echiniscoidea, Echiniscidae	Echiniscus blumi Richters, 1903	+ *	RN; CT; SC	[9,13,16,17,29,33]
Echiniscoidea, Echiniscidae	Echiniscus canadensis Murray, 1910	+ *	RN	[16]
Echiniscoidea, Echiniscidae	Echiniscus columinis Murray, 1911	+	SC	[33]
Echiniscoidea, Echiniscidae	Echiniscus crassispinosus Murray, 1907	+ *	MI	[31]
Echiniscoidea, Echiniscidae	Echiniscus dreyfusi de Barros, 1942	+	MI	[31]
Echiniscoidea, Echiniscidae	Echiniscus evelinae de Barros, 1942	+	TU	[51]
Echiniscoidea, Echiniscidae	Echiniscus manuelae da Cunha & do Nascimento Ribeiro, 1962	+	CR; MI; SA	[31,51]
Echiniscoidea, Echiniscidae	Echiniscus merokensis merokensis Richters, 1904	+ *	NQN; RN; SC; TF(SS)	[6,13,36]
Echiniscoidea, Echiniscidae	Echiniscus pellucidus Gasiorek, Bochnak, Vončina & Michalczyk, 2021	+	CT	[51]
Echiniscoidea, Echiniscidae	Echiniscus testudo (Doyère, 1840)	+	RN; CT; SC	[33,51]
Echiniscoidea, Echiniscidae	Echiniscus trisetosus Cuénot, 1932	+ *	CT	[29]
Echiniscoidea, Echiniscidae	Mopsechiniscus granulosus Mihelčič, 1967	+	NQN; RN; CT	[5,7,16,17,29,33,36]
Echiniscoidea, Echiniscidae	Mopsechiniscus imberbis (Richters, 1907)	N	TF(IAS)	[35]
Echiniscoidea, Echiniscidae	Pseudechiniscus (Meridioniscus) bartkei Węglarska, 1962	+ *	SA; RN TF(SS)	[30,33]
Echiniscoidea, Echiniscidae	Pseudechiniscus (Meridioniscus) saltensis Rocha, Doma, González-Reyes & Lisi, 2020	+	SA	[42]
Echiniscoidea, Echiniscidae	Pseudechiniscus (Pseudechiniscus) marinae Bartoš, 1934	+ *	RN	[9]
Echiniscoidea, Echiniscidae	Pseudechiniscus (Pseudechiniscus) suillus (Ehrenberg, 1853)	+ *	MI; RN; SC	[13,16,17,31]
Echiniscoidea, Echiniscidae	Testechiniscus spitsbergensis spitsbergensis (Scourfield, 1897)	+ *	CT; SC	[29,33]
Echiniscoidea, Echiniscidae	Viridiscus viridis (Murray, 1910)	N	NQN	[29]
Echiniscoidea, Oreellidae	Oreella mollis (Murray, 1910)	+	CT	[5]
Apochela, Milnesiidae	Milnesium argentinum Roszkowska, Ostrowska & Kaczmarek, 2015	+	RN	[26,27]
Apochela, Milnesiidae	Milnesium beatae Roszkowska, Ostrowska & Kaczmarek, 2015	+	RN	[26,27]
Apochela, Milnesiidae	Milnesium brachyungue Binda & Pilato, 1990	+	RN	[26,27]
Apochela, Milnesiidae	Milnesium eurystomum Maucci, 1991	+ *	SC	[14]
Apochela, Milnesiidae	Milnesium granulatum Ramazzotti, 1962	+	RN	[26,27]
Apochela, Milnesiidae	Milnesium irenae Rocha, González-Reyes, Ostertag & Lisi, 2022	+	LP	[43,52]
Apochela, Milnesiidae	Milnesium kogui Londoño, Daza, Caicedo, Quiroga & Kaczmarek, 2015	+	SA	[41]
Apochela, Milnesiidae	Milnesium pelufforum Rocha, González-Reyes, Ostertag & Lisi, 2022	+	SA	[43,52]
Apochela, Milnesiidae	Milnesium quiranae Rocha, González-Reyes, Ostertag & Lisi, 2022	+	SA	[43,52]
Apochela, Milnesiidae	Milnesium tardigradum Doyère, 1840	N	BA; ER; CR; CH; TU; SA; JY; LP; NQN; RN; CT; SC; TF(SS); TF(IAS)	[9,16,29,30,31,32,33,36]
Parachela, Calohypsibiidae	Calohypsibius ornatus (Richters, 1900)	+ *	RN	[16,17]
Parachela, Doryphoribiidae	Doryphoribius cephalogibbosus Rocha, Doma, González-Reyes & Lisi, 2020	+	SA	[42]
Parachela, Doryphoribiidae	Doryphoribius evelinae (Marcus, 1928)	+ *	CR	[31]
Parachela, Doryphoribiidae	Doryphoribius zappalai Pilato, 1971	+ *	SA; SC	[30,33,34]
Parachela, Doryphoribiidae	Grevenius asper (Murray, 1906)	+ *	MI; TU; JY	[30,31,34]
Parachela, Doryphoribiidae	Grevenius deflexus (Mihelčič, 1960)	+	BA	[34]
Parachela, Doryphoribiidae	Pseudobiotus megalonyx (Thulin, 1928)	+ *	BA; CR; CB	[35]
Parachela, Doryphoribiidae	Thulinius augusti (Murray, 1907)	+	BA; CR; CB	[30,31,34]
Parachela, Doryphoribiidae	Thulinius stephaniae (Pilato, 1974)	+ *	BA	[34]
Parachela, Hexapodibiidae	Parhexapodibius castrii (Ramazzotti, 1964)	+	RN	[34]
Parachela, Hypsibiidae	Notahypsibius arcticus (Murray, 1907)	+	TF(IAS)	[35]
Parachela, Hypsibiidae	Acutuncus antarcticus (Richters, 1904)	+ *	NQN	[35,36]
Parachela, Hypsibiidae	Adropion greveni (Dastych, 1984)	+	TF(SS)	[6]
Parachela, Hypsibiidae	Adropion scoticum (Murray, 1905)	+ *	RN; CT; SC; TF(SS)	[9,13,16,17,25,33]
Parachela, Hypsibiidae	Diphascon alpinum Murray, 1906	N	RN	[29,33]
Parachela, Hypsibiidae	Diphascon chilenense Plate, 1888	+	RN	[17,29,33]
Parachela, Hypsibiidae	Diphascon mitrense Pilato, Binda & Qualtieri, 1999	+	RN	[22]
Parachela, Hypsibiidae	Diphascon ongulense Morikawa, 1962	+	TF(SS)	[33]
Parachela, Hypsibiidae	Diphascon pingue pingue (Marcus 1936)	N	TU; JY; RN	[9,30,33]
Parachela, Hypsibiidae	Diphascon stappersi Richters, 1911	N	RN	[9]
Parachela, Hypsibiidae	Diphascon tenue Thulin, 1928	N	NQN; RN	[33,36]
Parachela, Hypsibiidae	Hypsibius allisoni Horning, Schuster & Grigarick, 1978	+	SC; TF(SS)	[6,13]
Parachela, Hypsibiidae	Hypsibius convergens (Urbanowicz, 1925)	+	TU; NQN; RN; SC	[10,13,17,29,30,33,36]
Parachela, Hypsibiidae	Hypsibius dujardini (Doyère, 1840)	+ *	TU; NQN; RN; CT; SC; TF(SS)	[9,30,33]
Parachela, Hypsibiidae	Hypsibius marcelli Pilato, 1990	+	BA; TF(SS)	[19]
Parachela, Hypsibiidae	Hypsibius microps Thulin, 1928	N	BA; ER; NQN; RN; SC	[9,13,32,33,36]
Parachela, Hypsibiidae	Hypsibius montanus Iharos, 1940	+ *	CT	[29]
Parachela, Hypsibiidae	Hypsibius pallidus Thulin, 1911	N	NQN	[36]
Parachela, Hypsibiidae	Itaquascon umbellinae de Barros, 1939	+	SC	[13]
Parachela, Hypsibiidae	Mixibius fueginus Pilato & Binda, 1996	+	TF(SS)	[6,20]
Parachela, Hypsibiidae	Mixibius saracenus (Pilato, 1973)	+	TF(SS)	[6]
Parachela, Hypsibiidae	Pilatobius brevipes (Marcus, 1936)	+ *	RN; TF(SS)	[10,29]
Parachela, Hypsibiidae	Pilatobius bullatus (Murray, 1905)	+ *	RN; CT	[9,17]
Parachela, Hypsibiidae	Pilatobius recamieri (Richters, 1911)	+ *	RN	[9,29,34]
Parachela, Hypsibiidae	Platicrista angustata (Murray, 1905)	+ *	RN; SC	[13,34]
Parachela, Isohypsibiidae	Dianea papillifera (Murray, 1905)	+	TF(IAS)	[35]
Parachela, Isohypsibiidae	Dianea sattleri (Richters, 1902)	+ *	RN	[9,17]
Parachela, Isohypsibiidae	Isohypsibius prosostomus Thulin 1928	+ *	CB	[17]
Parachela, Isohypsibiidae	Isohypsibius sculptus (Ramazzotti, 1962)	+	NQN; RN	[9]
Parachela, Isohypsibiidae	Ursulinius nodosus (Murray, 1907)	N	RN; CT	[9]
Parachela, Isohypsibiidae	Ursulinius tucumanensis (Claps & Rossi, 1984)	+	TU	[30,35]
Parachela, Macrobiotidae	Macrobiotus anderssoni Richters, 1908	+	RN; TF(SS)	[25]
Parachela, Macrobiotidae	Macrobiotus andinus Maucci, 1988	+	RN; SC	[13]
Parachela, Macrobiotidae	Macrobiotus echinogenitus Richters, 1903	+ *	SA; CT; TF(SS)	[17,18,23,24,29,30]
Parachela, Macrobiotidae	Macrobiotus hufelandi C.A.S. Schultze, 1833	N	BA; ER; CR; MI; CB; TU; SA; JY; NQN; RN; CT; SC; TF(SS)	[9,13,16,17,25,29,30,31,32,33]
Parachela, Macrobiotidae	Macrobiotus kazmierskii Kaczmarek & Michalczyk, 2009	+	RN	[12]
Parachela, Macrobiotidae	Macrobiotus kristenseni Guidetti, Peluffo, Rocha, Cesari & Moly de Peluffo, 2013	+	LP	[40]
Parachela, Macrobiotidae	Macrobiotus occidentalis Murray, 1910	+ *	RN	[9]
Parachela, Macrobiotidae	Macrobiotus papillosus Iharos, 1963	+	RN	[9]
Parachela, Macrobiotidae	Macrobiotus patagonicus Maucci, 1988	+	NQN; RN; SC	[13,36]
Parachela, Macrobiotidae	Macrobiotus porteri Rahm, 1931	+	?	[17]
Parachela, Macrobiotidae	Mesobiotus coronatus de Barros, 1942	+	BA	[32]
Parachela, Macrobiotidae	Mesobiotus erminiae Binda & Pilato, 1999	+ *	TF(SS)	[6]
Parachela, Macrobiotidae	Mesobiotus furciger (Murray, 1906)	+ *	RN; CT; TF(SS)	[17,25,29]
Parachela, Macrobiotidae	Mesobiotus harmsworthi (Murray, 1907)	N	CR; RN; SC	[9,13,17,31]
Parachela, Macrobiotidae	Mesobiotus montanus Murray, 1910	+ *	RN	[10]
Parachela, Macrobiotidae	Mesobiotus neuquensis Rossi, Claps & Ardohain, 2009	+	NQN	[36]
Parachela, Macrobiotidae	Mesobiotus nuragicus (Pilato & Sperlinga, 1975)	+ *	RN	[34]
Parachela, Macrobiotidae	Mesobiotus orcadensis (Murray, 1907)	+	CR; TF(SS)	[31,33]
Parachela, Macrobiotidae	Mesobiotus ovostriatus (Pilato & Patanè, 1998)	+	TF(SS)	[21]
Parachela, Macrobiotidae	Mesobiotus pseudoblocki Roszkowska, Stec, Ciobanu & Kaczmarek, 2016	+	RN	[27]
Parachela, Macrobiotidae	Mesobiotus szeptyckii (Kaczmarek & Michalczyk, 2009)	+	RN	[12]
Parachela, Macrobiotidae	Mesobiotus tehuelchensis (Rossi, Claps & Ardohain, 2009)	+	NQN	[36]
Parachela, Macrobiotidae	Minibiotus acontistus (de Barros, 1942)	+	CR; MI	[17,31]
Parachela, Macrobiotidae	Minibiotus claxtonae Rossi, Claps & Ardohain, 2009	+	NQN	[36]
Parachela, Macrobiotidae	Minibiotus furcatus (Ehrenberg, 1859)	+	BA; TF(SS)	[35]
Parachela, Macrobiotidae	Minibiotus intermedius (Plate, 1888)	+ *	ER; CR; RN; TF(SS)	[9,10,16,17,31]
Parachela, Macrobiotidae	Minibiotus pseudostellarus Roszkowska, Stec, Ciobanu & Kaczmarek, 2016	+	RN	[27]
Parachela, Macrobiotidae	Minibiotus subintermedius (Ramazzotti, 1962)	+	NQN; CB	[29,36]
Parachela, Macrobiotidae	Paramacrobiotus areolatus (Murray, 1907)	+ *	BA; CR; SA; LP; RN; SC	[13,30,31,32,33,38,39]
Parachela, Macrobiotidae	Paramacrobiotus richtersi (Murray, 1911)	+ *	BA; CR; MI; TU; SA; JY; NQN; RN; CT; TF(SS)	[9,10,29,30,31,32,33]
Parachela, Macrobiotidae	Schusterius tridigitus (Schuster, 1983)	+	TF(SS)	[11,28]
Parachela, Macrobiotidae	Sisubiotus spectabilis (Thulin, 1928)	+ *	SA	[30]
Parachela, Murrayidae	Dactylobiotus ambiguus (Murray, 1907)	+ *	BA; RN; TF(IAS)	[34]
Parachela, Murrayidae	Dactylobiotus dispar (Murray, 1907)	+ *	BA; CR; JY; RN	[30,33,34]
Parachela, Murrayidae	Dactylobiotus grandipes (Schuster, Toftner & Grigarick, 1978)	+	LP	[35]
Parachela, Murrayidae	Dactylobiotus lombardoi Binda & Pilato, 1999	+	TF(IAS)	[35]
Parachela, Murrayidae	Dactylobiotus parthenogeneticus Bertolani, 1981	+ *	BA; SJ; NQN	[34]
Parachela, Murrayidae	Murrayon pullari (Murray, 1907)	+ *	TF(SS)	[33]
Parachela, Ramazzottiidae	Hebesuncus conjungens (Thulin, 1911)	+ *	NQN; RN; SC	[13,16,17,29,33]
Parachela, Ramazzottiidae	Hebesuncus mollispinus Pilato, McInnes & Lisi, 2012	+	RN	[27]
Parachela, Ramazzottiidae	Ramazzottius anomalus (Ramazzotti, 1962)	+ *	ER; SA; SJ	[30,31]
Parachela, Ramazzottiidae	Ramazzottius baumanni (Ramazzotti, 1962)	+ *	ER; SA; JY; NQN; RN; CT; SC	[9,13,29,30,31,33,36]
Parachela, Ramazzottiidae	Ramazzottius oberhaeuseri (Doyère, 1840)	+ *	MI; SA; LP; RN; CT; TF(SS)	[16,17,25,30,31,33,38]
Parachela, Ramazzottiidae	Ramazzottius saltensis Claps & Rossi, 1984	+	SA	[30]

Table 1. List of valid species reported in Argentina from the literature. Status (record reliability): + = species reported with certainty; + * = species that need a diagnosis confirmation but each one representing a separate taxon from any other in Argentina; N = dubious record that cannot be taken into consideration because it may coincide with other species in the list. Province abbreviations: BA = Buenos Aires; CB = Córdoba; CH = Chaco; CR = Corrientes; CT = Chubut; ER = Entre Ríos; JY = Jujuy; LP = La Pampa; MI = Misiones; NQN = Neuquén; RN = Río Negro; SA = Salta; SC = Santa Cruz; SF = Santa Fé; SJ = San Juan; TF(IAS) = Isla de Atlántico Sur; TF(SS) = Tierra del Fuego; TU = Tucumán.

Order, Family	Species/Subspecies	Status (Record Reliability)	Province	Report for Argentina
Echiniscoidea, Echiniscidae	Antechiniscus jermani Rossi & Claps, 1989	+	RN	[33]
Echiniscoidea, Echiniscidae	Antechiniscus lateromamillatus (Ramazzotti, 1964)	+	NQN	[36]
Echiniscoidea, Echiniscidae	Barbaria bigranulata (Richters, 1907)	+	BA; ER; CR; MI; TU; SA; NQN; RN; CT; SC; TF(SS)	[8,9,13,15,29,30,31,32,33,36]
Echiniscoidea, Echiniscidae	Barbaria charrua (Claps & Rossi, 1997)	+	MI; TU	[8]
Echiniscoidea, Echiniscidae	Barbaria jenningsi (Dastych, 1984)	+	TF(IAS)	[35]
Echiniscoidea, Echiniscidae	Barbaria madonnae (Michalczyk & Kaczmarek, 2006)	+	CT	[8]
Echiniscoidea, Echiniscidae	Barbaria ollantaytamboensis (Nickel, Miller & Marley, 2001)	+	SA	[8]
Echiniscoidea, Echiniscidae	Barbaria paucigranulata Wilamowski, Vončina, Gąsiorek & Michalczyk, 2022	+	SA	[8]
Echiniscoidea, Echiniscidae	Barbaria cf. rufoviridis comb. nov. (du Bois-Reymond Marcus, 1944)	+ *	BA; LP; SF	[37,38,47]
Echiniscoidea, Echiniscidae	Barbaria weglarskae Gąsiorek, Wilamowski, Vončina & Michalczyk, 2022	+	SC	[8]
Echiniscoidea, Echiniscidae	Bryodelphax parvulus Thulin, 1928	+ *	RN	[16,17]
Echiniscoidea, Echiniscidae	Claxtonia capillata (Ramazzotti, 1956)	+ *	TU; RN; CT	[29,30,33]
Echiniscoidea, Echiniscidae	Claxtonia corrugicaudata (McInnes, 2010)	+	RN	[27]
Echiniscoidea, Echiniscidae	Claxtonia marginopora (Grigarick, Schuster & Nelson, 1983)	+	SC	[13]
Echiniscoidea, Echiniscidae	Claxtonia wendti (Dastych, 1984)	N	RN; CT; SC; TF(SS)	[10,13,29]
Echiniscoidea, Echiniscidae	Cornechiniscus lobatus (Ramazzotti, 1943)	+	SA	[50]
Echiniscoidea, Echiniscidae	Echiniscus aonikenk Gasiorek, Bochnak, Vončina & Michalczyk, 2021	+	CT	[51]
Echiniscoidea, Echiniscidae	Echiniscus arctomys Ehrenberg, 1853	N	RN	[9]
Echiniscoidea, Echiniscidae	Echiniscus blumi Richters, 1903	+ *	RN; CT; SC	[9,13,16,17,29,33]
Echiniscoidea, Echiniscidae	Echiniscus canadensis Murray, 1910	+ *	RN	[16]
Echiniscoidea, Echiniscidae	Echiniscus columinis Murray, 1911	+	SC	[33]
Echiniscoidea, Echiniscidae	Echiniscus crassispinosus Murray, 1907	+ *	MI	[31]
Echiniscoidea, Echiniscidae	Echiniscus dreyfusi de Barros, 1942	+	MI	[31]
Echiniscoidea, Echiniscidae	Echiniscus evelinae de Barros, 1942	+	TU	[51]
Echiniscoidea, Echiniscidae	Echiniscus manuelae da Cunha & do Nascimento Ribeiro, 1962	+	CR; MI; SA	[31,51]
Echiniscoidea, Echiniscidae	Echiniscus merokensis merokensis Richters, 1904	+ *	NQN; RN; SC; TF(SS)	[6,13,36]
Echiniscoidea, Echiniscidae	Echiniscus pellucidus Gasiorek, Bochnak, Vončina & Michalczyk, 2021	+	CT	[51]
Echiniscoidea, Echiniscidae	Echiniscus testudo (Doyère, 1840)	+	RN; CT; SC	[33,51]
Echiniscoidea, Echiniscidae	Echiniscus trisetosus Cuénot, 1932	+ *	CT	[29]
Echiniscoidea, Echiniscidae	Mopsechiniscus granulosus Mihelčič, 1967	+	NQN; RN; CT	[5,7,16,17,29,33,36]
Echiniscoidea, Echiniscidae	Mopsechiniscus imberbis (Richters, 1907)	N	TF(IAS)	[35]
Echiniscoidea, Echiniscidae	Pseudechiniscus (Meridioniscus) bartkei Węglarska, 1962	+ *	SA; RN TF(SS)	[30,33]
Echiniscoidea, Echiniscidae	Pseudechiniscus (Meridioniscus) saltensis Rocha, Doma, González-Reyes & Lisi, 2020	+	SA	[42]
Echiniscoidea, Echiniscidae	Pseudechiniscus (Pseudechiniscus) marinae Bartoš, 1934	+ *	RN	[9]
Echiniscoidea, Echiniscidae	Pseudechiniscus (Pseudechiniscus) suillus (Ehrenberg, 1853)	+ *	MI; RN; SC	[13,16,17,31]
Echiniscoidea, Echiniscidae	Testechiniscus spitsbergensis spitsbergensis (Scourfield, 1897)	+ *	CT; SC	[29,33]
Echiniscoidea, Echiniscidae	Viridiscus viridis (Murray, 1910)	N	NQN	[29]
Echiniscoidea, Oreellidae	Oreella mollis (Murray, 1910)	+	CT	[5]
Apochela, Milnesiidae	Milnesium argentinum Roszkowska, Ostrowska & Kaczmarek, 2015	+	RN	[26,27]
Apochela, Milnesiidae	Milnesium beatae Roszkowska, Ostrowska & Kaczmarek, 2015	+	RN	[26,27]
Apochela, Milnesiidae	Milnesium brachyungue Binda & Pilato, 1990	+	RN	[26,27]
Apochela, Milnesiidae	Milnesium eurystomum Maucci, 1991	+ *	SC	[14]
Apochela, Milnesiidae	Milnesium granulatum Ramazzotti, 1962	+	RN	[26,27]
Apochela, Milnesiidae	Milnesium irenae Rocha, González-Reyes, Ostertag & Lisi, 2022	+	LP	[43,52]
Apochela, Milnesiidae	Milnesium kogui Londoño, Daza, Caicedo, Quiroga & Kaczmarek, 2015	+	SA	[41]
Apochela, Milnesiidae	Milnesium pelufforum Rocha, González-Reyes, Ostertag & Lisi, 2022	+	SA	[43,52]
Apochela, Milnesiidae	Milnesium quiranae Rocha, González-Reyes, Ostertag & Lisi, 2022	+	SA	[43,52]
Apochela, Milnesiidae	Milnesium tardigradum Doyère, 1840	N	BA; ER; CR; CH; TU; SA; JY; LP; NQN; RN; CT; SC; TF(SS); TF(IAS)	[9,16,29,30,31,32,33,36]
Parachela, Calohypsibiidae	Calohypsibius ornatus (Richters, 1900)	+ *	RN	[16,17]
Parachela, Doryphoribiidae	Doryphoribius cephalogibbosus Rocha, Doma, González-Reyes & Lisi, 2020	+	SA	[42]
Parachela, Doryphoribiidae	Doryphoribius evelinae (Marcus, 1928)	+ *	CR	[31]
Parachela, Doryphoribiidae	Doryphoribius zappalai Pilato, 1971	+ *	SA; SC	[30,33,34]
Parachela, Doryphoribiidae	Grevenius asper (Murray, 1906)	+ *	MI; TU; JY	[30,31,34]
Parachela, Doryphoribiidae	Grevenius deflexus (Mihelčič, 1960)	+	BA	[34]
Parachela, Doryphoribiidae	Pseudobiotus megalonyx (Thulin, 1928)	+ *	BA; CR; CB	[35]
Parachela, Doryphoribiidae	Thulinius augusti (Murray, 1907)	+	BA; CR; CB	[30,31,34]
Parachela, Doryphoribiidae	Thulinius stephaniae (Pilato, 1974)	+ *	BA	[34]
Parachela, Hexapodibiidae	Parhexapodibius castrii (Ramazzotti, 1964)	+	RN	[34]
Parachela, Hypsibiidae	Notahypsibius arcticus (Murray, 1907)	+	TF(IAS)	[35]
Parachela, Hypsibiidae	Acutuncus antarcticus (Richters, 1904)	+ *	NQN	[35,36]
Parachela, Hypsibiidae	Adropion greveni (Dastych, 1984)	+	TF(SS)	[6]
Parachela, Hypsibiidae	Adropion scoticum (Murray, 1905)	+ *	RN; CT; SC; TF(SS)	[9,13,16,17,25,33]
Parachela, Hypsibiidae	Diphascon alpinum Murray, 1906	N	RN	[29,33]
Parachela, Hypsibiidae	Diphascon chilenense Plate, 1888	+	RN	[17,29,33]
Parachela, Hypsibiidae	Diphascon mitrense Pilato, Binda & Qualtieri, 1999	+	RN	[22]
Parachela, Hypsibiidae	Diphascon ongulense Morikawa, 1962	+	TF(SS)	[33]
Parachela, Hypsibiidae	Diphascon pingue pingue (Marcus 1936)	N	TU; JY; RN	[9,30,33]
Parachela, Hypsibiidae	Diphascon stappersi Richters, 1911	N	RN	[9]
Parachela, Hypsibiidae	Diphascon tenue Thulin, 1928	N	NQN; RN	[33,36]
Parachela, Hypsibiidae	Hypsibius allisoni Horning, Schuster & Grigarick, 1978	+	SC; TF(SS)	[6,13]
Parachela, Hypsibiidae	Hypsibius convergens (Urbanowicz, 1925)	+	TU; NQN; RN; SC	[10,13,17,29,30,33,36]
Parachela, Hypsibiidae	Hypsibius dujardini (Doyère, 1840)	+ *	TU; NQN; RN; CT; SC; TF(SS)	[9,30,33]
Parachela, Hypsibiidae	Hypsibius marcelli Pilato, 1990	+	BA; TF(SS)	[19]
Parachela, Hypsibiidae	Hypsibius microps Thulin, 1928	N	BA; ER; NQN; RN; SC	[9,13,32,33,36]
Parachela, Hypsibiidae	Hypsibius montanus Iharos, 1940	+ *	CT	[29]
Parachela, Hypsibiidae	Hypsibius pallidus Thulin, 1911	N	NQN	[36]
Parachela, Hypsibiidae	Itaquascon umbellinae de Barros, 1939	+	SC	[13]
Parachela, Hypsibiidae	Mixibius fueginus Pilato & Binda, 1996	+	TF(SS)	[6,20]
Parachela, Hypsibiidae	Mixibius saracenus (Pilato, 1973)	+	TF(SS)	[6]
Parachela, Hypsibiidae	Pilatobius brevipes (Marcus, 1936)	+ *	RN; TF(SS)	[10,29]
Parachela, Hypsibiidae	Pilatobius bullatus (Murray, 1905)	+ *	RN; CT	[9,17]
Parachela, Hypsibiidae	Pilatobius recamieri (Richters, 1911)	+ *	RN	[9,29,34]
Parachela, Hypsibiidae	Platicrista angustata (Murray, 1905)	+ *	RN; SC	[13,34]
Parachela, Isohypsibiidae	Dianea papillifera (Murray, 1905)	+	TF(IAS)	[35]
Parachela, Isohypsibiidae	Dianea sattleri (Richters, 1902)	+ *	RN	[9,17]
Parachela, Isohypsibiidae	Isohypsibius prosostomus Thulin 1928	+ *	CB	[17]
Parachela, Isohypsibiidae	Isohypsibius sculptus (Ramazzotti, 1962)	+	NQN; RN	[9]
Parachela, Isohypsibiidae	Ursulinius nodosus (Murray, 1907)	N	RN; CT	[9]
Parachela, Isohypsibiidae	Ursulinius tucumanensis (Claps & Rossi, 1984)	+	TU	[30,35]
Parachela, Macrobiotidae	Macrobiotus anderssoni Richters, 1908	+	RN; TF(SS)	[25]
Parachela, Macrobiotidae	Macrobiotus andinus Maucci, 1988	+	RN; SC	[13]
Parachela, Macrobiotidae	Macrobiotus echinogenitus Richters, 1903	+ *	SA; CT; TF(SS)	[17,18,23,24,29,30]
Parachela, Macrobiotidae	Macrobiotus hufelandi C.A.S. Schultze, 1833	N	BA; ER; CR; MI; CB; TU; SA; JY; NQN; RN; CT; SC; TF(SS)	[9,13,16,17,25,29,30,31,32,33]
Parachela, Macrobiotidae	Macrobiotus kazmierskii Kaczmarek & Michalczyk, 2009	+	RN	[12]
Parachela, Macrobiotidae	Macrobiotus kristenseni Guidetti, Peluffo, Rocha, Cesari & Moly de Peluffo, 2013	+	LP	[40]
Parachela, Macrobiotidae	Macrobiotus occidentalis Murray, 1910	+ *	RN	[9]
Parachela, Macrobiotidae	Macrobiotus papillosus Iharos, 1963	+	RN	[9]
Parachela, Macrobiotidae	Macrobiotus patagonicus Maucci, 1988	+	NQN; RN; SC	[13,36]
Parachela, Macrobiotidae	Macrobiotus porteri Rahm, 1931	+	?	[17]
Parachela, Macrobiotidae	Mesobiotus coronatus de Barros, 1942	+	BA	[32]
Parachela, Macrobiotidae	Mesobiotus erminiae Binda & Pilato, 1999	+ *	TF(SS)	[6]
Parachela, Macrobiotidae	Mesobiotus furciger (Murray, 1906)	+ *	RN; CT; TF(SS)	[17,25,29]
Parachela, Macrobiotidae	Mesobiotus harmsworthi (Murray, 1907)	N	CR; RN; SC	[9,13,17,31]
Parachela, Macrobiotidae	Mesobiotus montanus Murray, 1910	+ *	RN	[10]
Parachela, Macrobiotidae	Mesobiotus neuquensis Rossi, Claps & Ardohain, 2009	+	NQN	[36]
Parachela, Macrobiotidae	Mesobiotus nuragicus (Pilato & Sperlinga, 1975)	+ *	RN	[34]
Parachela, Macrobiotidae	Mesobiotus orcadensis (Murray, 1907)	+	CR; TF(SS)	[31,33]
Parachela, Macrobiotidae	Mesobiotus ovostriatus (Pilato & Patanè, 1998)	+	TF(SS)	[21]
Parachela, Macrobiotidae	Mesobiotus pseudoblocki Roszkowska, Stec, Ciobanu & Kaczmarek, 2016	+	RN	[27]
Parachela, Macrobiotidae	Mesobiotus szeptyckii (Kaczmarek & Michalczyk, 2009)	+	RN	[12]
Parachela, Macrobiotidae	Mesobiotus tehuelchensis (Rossi, Claps & Ardohain, 2009)	+	NQN	[36]
Parachela, Macrobiotidae	Minibiotus acontistus (de Barros, 1942)	+	CR; MI	[17,31]
Parachela, Macrobiotidae	Minibiotus claxtonae Rossi, Claps & Ardohain, 2009	+	NQN	[36]
Parachela, Macrobiotidae	Minibiotus furcatus (Ehrenberg, 1859)	+	BA; TF(SS)	[35]
Parachela, Macrobiotidae	Minibiotus intermedius (Plate, 1888)	+ *	ER; CR; RN; TF(SS)	[9,10,16,17,31]
Parachela, Macrobiotidae	Minibiotus pseudostellarus Roszkowska, Stec, Ciobanu & Kaczmarek, 2016	+	RN	[27]
Parachela, Macrobiotidae	Minibiotus subintermedius (Ramazzotti, 1962)	+	NQN; CB	[29,36]
Parachela, Macrobiotidae	Paramacrobiotus areolatus (Murray, 1907)	+ *	BA; CR; SA; LP; RN; SC	[13,30,31,32,33,38,39]
Parachela, Macrobiotidae	Paramacrobiotus richtersi (Murray, 1911)	+ *	BA; CR; MI; TU; SA; JY; NQN; RN; CT; TF(SS)	[9,10,29,30,31,32,33]
Parachela, Macrobiotidae	Schusterius tridigitus (Schuster, 1983)	+	TF(SS)	[11,28]
Parachela, Macrobiotidae	Sisubiotus spectabilis (Thulin, 1928)	+ *	SA	[30]
Parachela, Murrayidae	Dactylobiotus ambiguus (Murray, 1907)	+ *	BA; RN; TF(IAS)	[34]
Parachela, Murrayidae	Dactylobiotus dispar (Murray, 1907)	+ *	BA; CR; JY; RN	[30,33,34]
Parachela, Murrayidae	Dactylobiotus grandipes (Schuster, Toftner & Grigarick, 1978)	+	LP	[35]
Parachela, Murrayidae	Dactylobiotus lombardoi Binda & Pilato, 1999	+	TF(IAS)	[35]
Parachela, Murrayidae	Dactylobiotus parthenogeneticus Bertolani, 1981	+ *	BA; SJ; NQN	[34]
Parachela, Murrayidae	Murrayon pullari (Murray, 1907)	+ *	TF(SS)	[33]
Parachela, Ramazzottiidae	Hebesuncus conjungens (Thulin, 1911)	+ *	NQN; RN; SC	[13,16,17,29,33]
Parachela, Ramazzottiidae	Hebesuncus mollispinus Pilato, McInnes & Lisi, 2012	+	RN	[27]
Parachela, Ramazzottiidae	Ramazzottius anomalus (Ramazzotti, 1962)	+ *	ER; SA; SJ	[30,31]
Parachela, Ramazzottiidae	Ramazzottius baumanni (Ramazzotti, 1962)	+ *	ER; SA; JY; NQN; RN; CT; SC	[9,13,29,30,31,33,36]
Parachela, Ramazzottiidae	Ramazzottius oberhaeuseri (Doyère, 1840)	+ *	MI; SA; LP; RN; CT; TF(SS)	[16,17,25,30,31,33,38]
Parachela, Ramazzottiidae	Ramazzottius saltensis Claps & Rossi, 1984	+	SA	[30]

Some methodological issues strictly correlated to the assessment of the checklist (e.g., regarding the literature or taxonomy) are, for readers’ convenience, discussed directly in the “Results” section together with the checklist presentation.

We checked the following slides of Peluffo and Moly de Peluffo, identified as Milnesium cf. tardigradum Doyère, 1840, in Peluffo et al. [38] and Moly de Peluffo et al. [39], to update the diagnosis; these slides, deposited in the Rocha–Doma collection (National University of La Pampa, Argentina), are UNLPam SR1: 2, 3, 5, 7, 8, 12, 15, 17, 28, 31, 34, 35, 45, 50, 52, 60.

For the study of the genus assignment of Viridiscus rufoviridis, we reviewed the following slides of Argentine material (36 specimens identified as Viridiscus cf. rufoviridis) from the Rocha–Doma collection (National University of La Pampa, Argentina); UNLPam SR3: 1439 (4), 1440 (4), 1441 (1), 1443 (4), 1444 (4), 1843 (3), 1845 (2), 1846 (4), 1848 (2), 1942 (4), 1947 (4).

3. Results

3.1. Actual Checklist of Limno-Terrestrial Tardigrades of Argentina

Both classes Eutardigrada Richters, 1926, and Heterotardigrada Marcus, 1927, are present. Within the class Eutardigrada, the families present are: Calohypsibiidae Pilato, 1969; Doryphoribiidae Gąsiorek, Stec, Morek & Michalczyk, 2019; Hexapodibiidae Cesari, Vecchi, Palmer, Bertolani, Pilato, Rebecchi & Guidetti, 2016; Hypsibiidae Pilato, 1969; Isohypsibiidae Sands, McInnes, Marley, Goodall-Copestake, Convey & Linse, 2008; Macrobiotidae Thulin, 1928; Murrayidae Guidetti, Rebecchi & Bertolani, 2000; Milnesiidae Ramazzotti, 1962; and Ramazzottiidae Sands, McInnes, Marley, Goodall-Copestake, Convey & Linse, 2008. Heterotardigrada are represented by the family Echiniscidae Thulin, 1928, and Oreellidae Ramazzotti, 1962. Therefore, in the country, 11 families in total are present.

At lower taxonomic level, at least 39 genera and 119 species are present. Of these 119 currently valid species, 72 represent reliable (unquestioned by the literature) records (“+” in Table 1), while 47 are records questioned in the literature but represent taxa surely present in Argentina because they cannot be confused with any others in the list (“+ *” in Table 1; e.g., single representatives of their genus or species group, see further for more details).

Concerning the reliability of the species records from the literature, we basically followed Kaczmarek et al. [46], with some adjustments/updates. In

Table 2. Species with locus typicus in Argentina, indicating if the species is currently endemic for the country (Y = yes; N = no).

Order, Family	Species	Type Locality	Endemic (Y/N)
Echiniscoidea, Echiniscidae	Antechiniscus jermani Rossi & Claps, 1989	41°11′ S, 71°49′ W, 1800 m asl: Río Negro Province, Nahuel Huapi National Park, Monte Tronador.	Y
Echiniscoidea, Echiniscidae	Barbaria bigranulata (Richters, 1907)	54°48′ S, 68°18′ W, 50 m asl: Tierra del Fuego Province, Isla Grande de Tierra del Fuego, Ushuaia.	N
Echiniscoidea, Echiniscidae	Barbaria paucigranulata Wilamowski, Vončina, Gąsiorek & Michalczyk, 2022	24°47′14″ S 65°43′30″ W, 2150 m asl: Salta Province, Rosario de Lerma Department.	Y
Echiniscoidea, Echiniscidae	Barbaria weglarskae Gąsiorek, Wilamowski, Vončina & Michalczyk, 2022	48°25′42″ S 71°44′48″ W, 803 m asl: Santa Cruz Province, vicinity of la Florida.	Y
Echiniscoidea, Echiniscidae	Echiniscus aonikenk Gasiorek, Bochnak, Vončina & Michalczyk, 2021	44°10′26″ S 71°33′58″ W, 716 m asl: Patagonia, Chubut Province, vicinity of Río Pico.	Y
Echiniscoidea, Echiniscidae	Echiniscus pellucidus Gasiorek, Bochnak, Vončina & Michalczyk, 2021	44°10′26″ S 71°33′58″ W, 716 m asl: Patagonia, Chubut Province, vicinity of Río Pico.	Y
Echiniscoidea, Echiniscidae	Mopsechiniscus granulosus Mihelčič, 1967	41°14′ S, 71°46′ W; 800 m asl: Río Negro Province, Pampalinda, near Cainquenes stream. 41°58′ S, 71°31′ W, 390 m asl: Río Negro Province, Bolson.	N
Echiniscoidea, Echiniscidae	Pseudechiniscus (Meridioniscus) saltensis Rocha, Doma, González-Reyes & Lisi, 2020	24°27′–25°47′ S, 64°55′–65°40′ W, 1150 m asl: Salta Province, Salta City.	Y
Apochela, Milnesiidae	Milnesium argentinum Roszkowska, Ostrowska & Kaczmarek, 2015	41°13′ S, 71°27′ W, ca. 1200 m asl: Río Negro Province, Nahuel Huapi National Park.	Y
Apochela, Milnesiidae	Milnesium beatae Roszkowska, Ostrowska & Kaczmarek, 2015	41°12′ S, 71°50′ W, ca. 1000 m asl: Río Negro Province, Nahuel Huapi National Park.	Y
Apochela, Milnesiidae	Milnesium irenae Rocha, González-Reyes, Ostertag & Lisi, 2022	36°37′13″ S, 64°17′26″ W, ca 177 m asl: La Pampa Province, Santa Rosa City.	Y
Apochela, Milnesiidae	Milnesium pelufforum Rocha, González-Reyes, Ostertag & Lisi, 2022	24°47′18″ S, 65°24′38″ W, 1150 m asl: Salta Province, Salta City.	Y
Apochela, Milnesiidae	Milnesium quiranae Rocha, González-Reyes, Ostertag & Lisi, 2022	24°47′18″ S, 65°24′38″ W, 1150 m asl: Salta Province, Salta City.	Y
Parachela, Doryphoribiidae	Doryphoribius cephalogibbosus (Rocha, Doma, González-Reyes & Lisi, 2020)	24°27′–25°47′ S, 64°55′–65°40′ W, 1150 m asl: Salta Province, Salta City.	Y
Parachela, Hypsibiidae	Diphascon mitrense Pilato, Binda & Qualtieri, 1999	54°47′ S, 68°16′ W; 100 m asl: Tierra del Fuego Province, Península Mitre, Estancia Río Pipo.	Y
Parachela, Hypsibiidae	Hypsibius marcelli Pilato, 1990	52°54′ S, 68°27′ W, 0 m asl: Tierra del Fuego Province, Isla Grande de Tierra del Fuego, near Estancia Cullen.	Y
Parachela, Hypsibiidae	Mixibius fueginus Pilato & Binda, 1996	54°47′ S, 68°24′ W, 650 m asl: Tierra del Fuego Province, San Martial Glacier.	Y
Parachela, Isohypsibiidae	Ursulinius tucumanensis (Claps & Rossi, 1984)	26°47′ S, 65°20′ W, 750 m asl: Tucumán Province, Horco Molle.	Y
Parachela, Macrobiotidae	Macrobiotus anderssoni Richters, 1908	54°48′ S, 68°18′ W, 50 m asl: Tierra del Fuego Province, Isla Grande de Tierra del Fuego, Ushuaia, valley. 54°46′ S, 68°12′ W, 150 m asl: Tierra del Fuego Province, Isla Grande de Tierra del Fuego, Río Olivia. 54°47′ S, 68°23′ W, 800 m asl: Tierra del Fuego Province, Isla Grande de Tierra del Fuego, mountain region of Ushuaia. 54°50′ S, 68°34′ W, 0 m asl: Tierra del Fuego Province, Tierra Mayor (Isla Grande de Tierra del Fuego), near Roca Lake.	Y
Parachela, Macrobiotidae	Macrobiotus andinus Maucci, 1988	50°06′ S, 73°18′ W, 200 m asl: Santa Cruz Province, Los Glaciares National Park, shores of Argentino Lake, near Onelli Glacier.	N
Parachela, Macrobiotidae	Macrobiotus kazmierskii Kaczmarek & Michalczyk, 2009	41°11.551′ S, 71°49.908′ W/41°12′N, 71°50′ W, 1100 m asl: Río Negro Province, Nahuel Huapi National Park, Ventisquero Negro.	Y
Parachela, Macrobiotidae	Macrobiotus kristenseni Guidetti, Peluffo, Rocha, Cesari & Moly de Peluffo, 2013	35°40′ S, 63°44′ W; 143 m asl: La Pampa Province, General Pico (125 km northeast of Santa Rosa). 36°39′ S, 64°17′ W; 177 m asl: La Pampa Province, Santa Rosa City. 36°55′ S, 64°16′ W; 150 m asl: La Pampa Province, Reserve Provincial Parque Luro (35 km south of Santa Rosa).	Y
Parachela, Macrobiotidae	Macrobiotus papillosus Iharos, 1963	41°59′ S, 71°31′ W, 360 m asl: Río Negro Province, El Bolsón, Mt. Piltriquitron.	Y
Parachela, Macrobiotidae	Macrobiotus patagonicus Maucci, 1988	50°06′ S, 73°18′ W, 200 m asl: Santa Cruz Province, Los Glaciares National Park, shores of Argentino Lake, near Onelli Glacier.	N
Parachela, Macrobiotidae	Mesobiotus neuquensis Rossi, Claps & Ardohain, 2009	40°07′ S, 71°39′ W, 700 m asl: Neuquén Province, Hua Hum, Junín de los Andes.	Y
Parachela, Macrobiotidae	Mesobiotus ovostriatus (Pilato & Patanè, 1998)	54°17′ S, 66°42′ W, 50 m asl: Tierra del Fuego Province, Isla Grande de Tierra del Fuego, Península Mitre, Cabo San Pablo. 54°47′ S, 68°16′ W, 100 m asl: Tierra del Fuego Province, Peninsula Mitre, Río Pipo.	N
Parachela, Macrobiotidae	Mesobiotus pseudoblocki Roszkowska, Stec, Ciobanu & Kaczmarek, 2016	41°12′ S, 71°50′ W, ca. 1000 m asl: Río Negro, Nahuel Huapi National Park, Ventisquero Negro.	Y
Parachela, Macrobiotidae	Mesobiotus szeptyckii (Kaczmarek & Michalczyk, 2009)	41°31′ S, 71°30′ W, 950 m asl: Río Negro Province, Nahuel Huapi National Park, 70 km south of San Carlos de Bariloche.	Y
Parachela, Macrobiotidae	Mesobiotus tehuelchensis (Rossi, Claps & Ardohain, 2009)	39°08′ S, 71°17′ W, 1000 m asl: Neuquén Province, Aluminé Ñorquinco Lake.	Y
Parachela, Macrobiotidae	Minibiotus claxtonae Rossi, Claps & Ardohain, 2009	39°25′ S, 71°17′ W, 1000 m asl: Neuquén Province, Aluminé, Quillén Lake.	Y
Parachela, Macrobiotidae	Minibiotus pseudostellarus Roszkowska, Stec, Ciobanu & Kaczmarek, 2016	41°12′ S, 71°51′ W, ca. 1200 m asl: Río Negro Province, Nahuel Huapi National Park, Bariloche, at the foot of the Tronador volcano, Garganta del Diablo waterfall.	Y
Parachela, Macrobiotidae	Schusterius tridigitus (Schuster, 1983)	54°47′ S, 68°24′ W, 600–750 m asl: Tierra del Fuego Province, Sierra Martial.	Y
Parachela, Ramazzottiidae	Ramazzottius saltensis Claps & Rossi, 1984	24°55′ S, 64°09′ W, 400 m asl: Salta Province, road from Las Lajitas to J.V. González.	Y

of that paper, only two categories were present: “+” (confirmed record) and “(+)” (dubious record). We (in Table 1) kept the “+” category but split the “(+)” one of Kaczmarek et al. [46] into two categories: “+ *” (dubious record, but cannot be confused with the other species in the list) and “N” (dubious record that may correspond to other species in the list).

Regarding Table 2 in Kaczmarek et al. [46], we maintained the “+” species with the exception of five species that were moved to the “+ *” category for caution, and also thanks to the reviewers of the present paper, these species are: Claxtonia capillata (Ramazzotti, 1956), Minibiotus intermedius (Plate, 1888), Pseudechiniscus (Pseudechiniscus) marinae Bartoš, 1934, Ramazzottius anomalus (Ramazzotti, 1962) and Ramazzottius baumanni (Ramazzotti, 1962). Of course, we added to the “+” category the recent and reliable records published after Kaczmarek et al. [46].

Two species belonging to the “(+)” category of Kaczmarek et al. [46] were moved to the “+” category, owing to recent reliable records confirming their real presence in Argentina; these species are Echiniscus testudo (Doyère, 1840) and Hypsibius convergens (Urbanowicz, 1925).

Our “N” category includes additional 14 species from the literature that have not been counted because they correspond to dubious records and the species might have been misidentified with possible confusion with other species in the list (“N” in Table 1; e.g., old records of Milnesium tardigradum that may correspond to other species of the genus, reported/identified more recently, present in the list).

Indeed, we were able to verify (by examining the pertinent material indicated in the Materials and Methods section) that the records of M. cf. tardigradum reported by Peluffo et al. [38] and Moly de Peluffo et al. [39] did refer to specimens belonging to three species recently described: M. pelufforum Rocha, González-Reyes, Ostertag & Lisi, 2022 (slides UNLPam SR1: 5, 8, 12, 15, 50); M. irenae Rocha, González-Reyes, Ostertag & Lisi, 2022 (slides UNLPam SR1: 2, 7, 17, 28, 31); or M. quiranae Rocha, González-Reyes, Ostertag & Lisi, 2022 (slides UNLPam SR1: 3, 34, 35, 45, 52, 60); the other old records of M. tardigradum [9,16,29,30,31,32,33,36] remain questionable.

Generally, all 14 species with dubious records (status “N” in Table 1) are in need of revision to verify if they can or cannot be definitively included.

Our “+ *” category (47 species) requires a clearer explanation in order to justify our choices.

Eight species in this category (Acutuncus antarcticus (Richters, 1904); Bryodelphax parvulus (Richters, 1904); Testechiniscus spitsbergensis (Scourfield, 1897); Calohypsibius ornatus (Richters, 1900); Pseudobiotus megalonyx (Thulin, 1928); Platicrista angustata (Murray, 1905); Sisubiotus spectabilis (Thulin, 1928) and Murrayon pullari (Murray, 1907)) are each the only representative of its own genus in the list, although at the time of the record some might be included in another genus with other representatives in the list (e.g., Macrobiotus), it is clear that the given species was clearly distinct from the other species actually belonging to the old genus.

In the case of species described in the far past, though often affected by incomplete/unclear descriptions, they have been counted because they are clearly distinguishable (in the past also) from the congeneric species; this criterion means that either the old species was described since the beginning for very obvious/peculiar characters, or the congeneric species of the list were described subsequently as very well differentiated from the old species (in spite of its incomplete description).

Another criterion we used was to consider as reliable the records of congeneric species by the same authors and in close times (i.e., with the same eyes, knowledge and methodologies), and occasionally the records are even in the same paper.

Examples of the application of these criteria are:

(1)

For Minibiotus intermedius (Plate, 1888) (indeed, indicated as “+” in Kaczmarek et al. [46], but, to be cautious, we put it into the “+ *” category). The only other Minibiotus R.O. Schuster, 1980, species of the list of the intermedius group with smooth cuticle is M. acontistus (de Barros, 1942), but the questioned records of M. intermedius were together with records of M. acontistus [17,31], indicating that the pertinent authors were able to distinguish between them.

(2)

For Ramazzottius oberhaeuserii (Doyère, 1840), two species of the genus reported for Argentina, R. anomalus (Ramazzotti, 1962) and R. baumanni (Ramazzotti, 1962), were described with notorious characters distinguishing them from R. oberhaeuseri. All three species were recorded together in Claps and Rossi [31]; similarly, the fourth Argentine species, R. saltensis, was recorded together with R. oberhaeuseri in Claps and Rossi [30]. All this clearly indicates no confusion between R. oberhaeuseri and the other three congeneric species.

(3)

The three dubious species of the genus Dactylobiotus R.O. Schuster, 1980, and the only two species of the genus Grevenius Gąsiorek, Stec, Morek & Michalczyk, 2019, were recorded together in Rossi and Claps [34], and the only two species of the genus Paramacrobiotus Guidetti, Schill, Bertolani, Dandekar & Wolf, 2009, were recorded together in Claps and Rossi [30,31] and Rossi and Claps [32,33].

The updated checklist is given in Table 1, with the indication, for each species of status (record reliability “+”, “+ *” or “N”, as mentioned above), Argentine province, and literature source for the records.

In Figure 1, a map showing Argentina with all currently known and studied sites in the various provinces is provided.

A total of 33 species were described from samples collected in Argentina (terra typica), 28 of which are currently endemic for the country. These data are provided in Table 2, and include geographic coordinates for the loci typici.

3.2. Genus Assignment for Viridiscus rufoviridis (du Bois-Reymond Marcus, 1944): Barbaria rufoviridis comb. nov.

The species currently called Viridiscus rufoviridis (du Bois-Reymond Marcus, 1944) was first described as Echiniscus rufoviridis in 1944 from São Paulo State (Brazil). The species was also reported in various localities of Argentina by Peluffo et al. [37], Peluffo et al. [38] and Rocha et al. [47], and from Ecuador by Nelson et al. [53].

We have not had the possibility to determine, yet, if the type material of the species still exists, in order to compare it directly with the Argentine material in our possession. Thus, one might put into doubt the exact attribution of the Argentine material to V. rufoviridis sensu stricto; however, we examined the Argentine specimens (slides indicated in the Materials and Methods section) and we compared our observations plus the description and images published in the abovementioned papers, with the original description and drawing of the types from Brazil (the drawing is shown in figure 4, page 21, of du Bois-Reymond Marcus [54]), which were of good quality for that time, and we feel confident to conclude that the Argentine specimens and the Brazilian types are at least two extremely similar species (if not exactly the same species). Thus, they must surely belong to the same genus, modernly intended also. In addition, our morphotype is the same or very similar to that from Ecuador, identified as V. rufoviridis by Nelson et al. [53], and Kaczmarek et al. [46] did not put in doubt the records of this species from Argentina, as a confirmation that they can also be reliable zoogeographically. Just to be cautious, we refer to the Argentine morphotype as V. cf. rufoviridis.

Falling back to history, before the paper by Gąsiorek et al. [48], V. rufoviridis was included in the viridis group within the genus Echiniscus C.A.S. Schultze, 1840; then, in the abovementioned paper, the genus Echiniscus was split in different genera, and the old viridis group was transferred into the new genus Viridiscus Gąsiorek & Michalczyk, 2019, in Gąsiorek et al. [48], currently including V. clavispinosus (Fontoura, Pilato & Lisi, 2011), V. perviridis (Ramazzotti, 1959), V. rufoviridis (du Bois-Reymond Marcus, 1944), V. viridianus (Pilato, Fontoura & Lisi, 2007), V. viridis (Murray, 1910) and V. viridissimus (Péterfi, 1956).

Gąsiorek et al. [48] put the species under discussion into the genus Viridiscus with some perplexities, and those authors did not consider or discuss the papers by Peluffo et al. [37] and Rocha et al. [47], in which important data (including photographs) were present, allowing for realization that V. rufoviridis cannot be attributed to the genus Viridiscus, but, instead, to the genus Barbaria Michalczyk, Gąsiorek, Morek & Stec, 2019, in Gąsiorek et al. [48]. As a matter of fact, in Peluffo et al. [37] the species under discussion was partially redescribed, and, above all, there are images under PCM and SEM, and in Rocha et al. [47] the cuticle ultrastructure was examined under TEM. In both papers, all images and descriptions are not compatible with the genus Viridiscus, but they are with Barbaria instead. The images of B. cf. rufoviridis comb. nov. by Peluffo et al. [37] (cuticular ornamentation: PCM and SEM) and Rocha et al. [47] (cuticle structure: TEM) can be compared with those of Gąsiorek et al. [48] (cuticular ornamentation of Viridiscus: PCM and SEM; cuticular ornamentation of Barbaria: PCM) and of Michalczyk & Kaczmarek [15] (for Barbaria: cuticular ornamentation under PCM and SEM; cuticle structure under SEM and through drawings), clarifying any doubt. In

Table 3. References for the various images from [15,37,47,48] showing the cuticle characteristics of the genera Viridiscus and Barbaria, and of B. cf. rufoviridis comb. nov.

Characters	Image Type	Figures of the Genus Viridiscus	Figures of B. cf. rufoviridis comb. nov. (Argentine Material)	Figures of the Genus Barbaria
Cuticular ornamentation	PCM	4e, 5e, 6f in Gąsiorek et al. [48]	1–2 in Peluffo et al. [37]	4a, 5a, 6a in Gąsiorek et al. [48] 2, 6, 13, 15, 25 in Michalczyk & Kaczmarek [15]
	SEM	7d in Gąsiorek et al. [48]	3–5 in Peluffo et al. [37]	3–4; 9–10; 14, 16, 23 in Michalczyk & Kaczmarek [15]
Cuticle structure	SEM	-	-	11–12, 53–54 in Michalczyk & Kaczmarek [15]
	TEM	-	1–2 in Rocha et al. [47]	-
	drawings	-	-	72–74 in Michalczyk & Kaczmarek [15]

, all possible image comparisons from the abovementioned literature reports are indicated. It is true that B. cf. rufoviridis observed by us and shown, for example, in Nelson et al. [53] (from Ecuador) shares with Viridiscus the presence of green pigments that do not dissolve in mounting media, but we do believe that this simple character in common is far less relevant in the genus definition with respect to the complexity of the cuticular structure.

4. Discussion and Conclusions

The present work allowed us to update the checklist of Argentine limno-terrestrial tardigrade species and subspecies; such checklist has grown from 111 units (reliable plus dubious records from Kaczmarek et al. [46]) to 119 units in spite of the fact that 14 dubious records (included in the old checklist) have been excluded. We also provide evidence that 33 species were described from samples collected in Argentina (terra typica); of those, a good 28 are currently endemic for the country.

The Republic of Argentina occupies 2.78 million km² and is the second largest country in South America and the eighth largest in the world. Its vast surface comprises a very high diversity of macro- and microenvironments, many still unknown or unexplored; thus, the numbers of species reported to-date are most likely highly underestimated.

This can also be noticed from Figure 1, in which it is evident that previous surveys did not take into account any attempt to have a uniform distribution in order to explore the various part of the country. There are areas with many records and others unexplored. This may be due to at least two factors: one is the vicinity to the place of Argentinean authors’ residence or work (as is the case for sampling in the province of La Pampa and Salta); the second factor is related to areas exploited touristically (as occurs for southern Patagonia and northern Argentina), analogously stated by Jörgensen [55] for Africa.

On the contrary, of the 23 provinces in which the country is divided, there are 7 in which there are no records because there have been no studies at all.

Indeed, the most studied provinces also still produce good results through investigations (e.g., Rocha et al. [42]; Rocha et al. [52]), showing that we are far from a satisfactory knowledge from the faunistic and taxonomic (and more) point of view.

These observations clearly indicate that it is necessary to continue studying the limno-terrestrial tardigrades of the regions already under study, and to complete the knowledge for the entire country by adding areas still not investigated.

The present work also provides a taxonomic adjustment (the case of Barbaria rufoviridis comb. nov.), and to correct past uncertain diagnoses (the case of the previous Milnesium cf. tardigradum, which was hiding three different species). These are examples of how working only with lists of species can produce collateral data that are useful in other fields.

Several past species records still remain dubious, and this is another task challenging future studies.