taxonID	type	description	language	source
4D4287F9367BFFD1FEE6FD7389FCF91D.taxon	description	Figs 2 – 7. Hyalella sp. 6 — Hankel et al., 2023	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F9367BFFD1FEE6FD7389FCF91D.taxon	materials_examined	MATERIAL EXAMINED. Holotype. Argentina: 1 ♂, Catamarca Province, Calalaste, – 25.70791 ° S – 67.52827 ° W, alt. 4429 m a. s. l, 16. X. 2020, J. Rodriguez leg., (FML-CRUST 01337), 9.6 mm. Paratypes: 1 ♀ measuring 6.18 mm, and 2 ♂♂ and 1 ♀ (FML-CRUST 01338), 2 ♂♂ and 2 ♀♀ (IBN-EcoPP- 25 D), same data as holotype. Additional material: Argentina: 5 ♂♂ and 4 ♀♀, La Rioja Province, Río Los Baños, – 28.1725 ° S – 69.17408 ° W, 3915 m a. s. l., 24. II. 2016, 3 ♂♂ and 2 ♀♀, Catamarca Province, Quebrada del Diablo, – 26.02902778 ° S – 67.69330556 ° W, 3955 m a. s. l, 15. V. 2017, 3 ♂♂, Calalaste, – 25.7135 ° S – 67.52336 ° W, 4392 m a. s. l, 15. XII. 2015, J. Rodriguez leg.	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F9367BFFD1FEE6FD7389FCF91D.taxon	diagnosis	DIAGNOSIS. Body smooth. Antenna II slightly longer than head and longer than Antenna I. Maxilla I palp with a medial constriction and with two plumose setae on tip. Gnathopod I propodus with sinuous palm margin exhibiting slight medial concavity; palm angle with four cuspidate setae. Two short setae placed subdistally on outer surface of basis of pereiopod 7. Sternal gills present on pereonites 3 to 7. Epimeral plate 1 rounded, plates 2 and 3 slightly acuminate. Uropod 1 not sexually-dimorphic.	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F9367BFFD1FEE6FD7389FCF91D.taxon	materials_examined	TYPE LOCALITY AND REFERENCE SEQUENCES. Calalaste peatbog, – 25.70791 ° S – 67.52827 ° W, 4429 m a. s. l, Catamarca Province, Argentina. GenBank accession numbers: COI: OR 726343, OR 726347, OR 726345, OR 726346 (Fig. 1).	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F9367BFFD1FEE6FD7389FCF91D.taxon	etymology	ETYMOLOGY. The species was named in honour of the first author’s grandfather.	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F9367BFFD1FEE6FD7389FCF91D.taxon	description	DESCRIPTION OF MALE Body: Stout and smooth. Maximum length observed 9.78 mm. Head: Eye ellipsoid, pigmented. Antenna I: shorter than antenna II but slightly longer than its peduncle. Peduncular segments 1 - 3 with few simple setae and numerous plumose setae C 2, alongside microsetae (Ib type). The flagellum consists of nine articles with groups of simple setae A 1, additionally featuring distally positioned aesthetascs, occurring between articles 5 – 7 (Fig. 3 a, b). Antenna II: longer than Antenna I, with its peduncle approximately equal to the length of the head. Peduncular segment 4 much shorter than 5. Peduncular segment 3 with a plumose thin seta; segments 3 – 5 with distal and medial simple A 1 or plumose setae C 2. Flagellum comprises 11 articles, each bearing groups of simple setae (Fig. 3 c, d). Upper lip: ordinary, with minute setae on the distal part (Fig. 4 a). Mandible: Right mandible incisor 6 - denticulate, lacinia mobilis complex bifurcate, setal row with 4 pappose setae (Fig. 4 b). Left mandible incisor 5 - denticulate, lacinia mobilis 4 - denticulate, setal row with six pappose setae (Fig. 4 c). Both mandibles with well-developed triturative molars. Lower lip: ordinary, outer lobes covered with minute setae (Fig. 4 d). Maxilla I (Fig. 4 e): palp unsegmented, long and narrow, with a medial constriction, reaching more than half the length of the distance between the base of the palp and the apex of the outer plate, with two plumose distal setae on tip. Outer plate with nine serrate setae type F 4, some of them larger and spatulate, as can be observed in detail in the SEM image (Fig. 4 e). Inner plate shorter than outer one, with two apical papposerrate setae, and several marginal setules. Maxilla II (Fig. 4 f): Inner plate subequal in length to the outer with 1 strong pappose seta on inner margin; outer and inner plates with few hair-like setae. Maxilliped (Fig. 4 g): Inner plate longer than wide, with three stout robust cuspidate B 1 setae, accompanied by additional pappose setae and setules on both apex and margins. Outer plate with simple setae on inner and distal margins. Palp 4 - segmented, second one as long as wide; segment 4 short and unguifom; segments 1 – 3 with simple setae at outer distal end; segment 3 distally ornamented with denticles of type t 5, featuring setae of both simple type A 1 and serrated type F 3. Gnathopod I (Fig. 5 a): subchelate. Coxal plate longer than wide, with microtrichs (type Ia) along margin. Basis with four simple setae on posterior margin. Propodus (Fig. 5 b) hatchetshaped, longer than its maximum width, with group of slender simple setae at anterodistal corner; inner face with oblique row of seven serrate setae (F 3) arranged in two groups; palmar margin sinuous; palm angle equipped with four cuspidate setae and comb / setose-scales. Dactylus claw-like, with denticles on the inner margin. Additionally, microtrichs of type Ib are observed on the dactylus and surface of the propodus. Palmar Index (sensu Ruffo [1973]) = 0.49. Gnathopod II (Fig. 5 c): subchelate. Basis approximately three times longer than its maximum width, bearing four groups of setae at posterior margin. Basis, ischium and merus each with group of setae on postero-distal angle. Posterior lobe of carpus with pectinate border lined with row of serrate setae. Propodus ovate; palm margin oblique, slightly longer than posterior margin; palm margin with several strong, short to medium-length setae; palm angle with two cuspidate setae B 5 with accessory seta and comb / setose scales. Dactylus claw-like, congruent with palm, carrying single thin plumose seta dorsally. Palmar Index (sensu Ruffo [1973]) = 0.34. Pereiopods 3 and 4 (Fig. 6 a, b): similar in size and shape. Coxal plates: pereiopod 3 longer than wide; pereiopod 4 excavated posteriorly, longer than wide; both coxal plates with margins lined with thin simple setae (type Ia); posterior margin of basis, merus, carpus and propodus with simple or cuspidate setae; dactylus short, less than half length of propodus. Pereiopods 5 – 7 (Fig. 6 c – e): pereiopod 5 notably shorter than pereiopods 6 and 7, which are subequal in length. Coxal plates: pereiopod 5: wider than long, posterior lobe deeper than anterior; pereiopod 6: as long as wide with a significantly reduced anterior lobe; pereiopod 7: wider than long; all coxal plates with thin, simple setae along their margins (type Ia). Basis: posterior margin expanded, notably more in pereiopod 7 than in pereiopods 5 and 6, finely serrated; additionally, the seventh pereiopod has two reduced setae subdistally on outer surface; anterior margin of basis of pereiopod 5 bearing group of four plumose setae. Anterior and posterior margins of ischium, merus, carpus, and propodus with simple or cuspidate setae. Dactylus short, like pereiopods 3 and 4. Coxal gills: sacciform, present on gnathopod II to pereiopod 6 (Fig. 6 a – d). Sternal gills tubular (Fig. 6 d), present on pereonites 3 to 7. Pleopods: Biramous, similar; peduncle shorter than rami, with retinacula; rami multi-annulated and bearing long plumose setae. Uropod 1 (Fig. 7 a): Peduncle longer than rami, with four proximal cuspidate setae on dorsal surface and two other distal cuspidate setae all aligned in a longitudinal row; rami subequal in length; outer ramus with three dorsal and four distal cuspidate setae; inner ramus with two dorsal and five distal cuspidate setae, without modified curved seta on inner side. Microtrichs of type Ib on both peduncle and rami. Uropod 2 (Fig. 7 b): shorter than uropod 1. Peduncle longer than rami, with three dorsal cuspidate setae aligned in a longitudinal row and other cuspidate setae on dorsolateral and dorsomedial distal margin; inner ramus with two dorsal and six distal cuspidate setae, one of them longer than rest; outer ramus with one dorsal and three distal cuspidate setae, one of them longer than rest. Microtrichs of type Ib on peduncle and rami. Uropod 3 (Fig. 7 c): shorter than peduncle of uropod 2. Peduncle much wider than ramus, as long as wide, with five strong cuspidate distal setae and other six thin simple setae on ventral face; ramus stout, shorter than peduncle, apex with one simple seta and five strong cuspidate setae. Telson (Fig. 7 e): wider than long, entire, with many thin simple setae on distal margin and microtrichs type Ib; dorsal surface with a scale pattern. The telson of a male paratype features only two simple setae at each side (Fig. 7 d). Epimeral plates (Fig. 7 f): Plate 1 is rounded posterodistally, while Plates 2 and 3 are slightly acuminate; all posterior margins bear a few setules. Intraspecific Variability in males: some males (IBN-EcoPP- 23 C) exhibit six setae on the inner face of gnathopod I propodus, while others display nine, in contrast to the seven displayed by the holotype. Variability was observed also in the setae count at telson and uropod 2 apices; in one of the male paratypes (FML-CRUST 01338), the telson exhibited only two simple setae on each side (Figs. 7 d, e), while the inner ramus of uropod 2 apex carries seven setae. FEMALE (PARATYPES). Maximum body length observed 7.76 mm. Habitus similar to male except for the following characters: palp of maxilla I shorter, with two significantly longer setae at apex compared to male (Fig. 4 e). Gnathopods I and II closely resemble each other in size and shape, inner face of gnathopod I displaying seven serrate setae, while gnathopod II features six. Gnathopod II differs from its male counterpart in both shape and the relatively smaller size of its propodus (Fig. 5 d, e). Oostegites broad and subtriangular, with larger curled setae on the margins (Fig. 5 d).	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F93675FFC9FE10F9388D31FB82.taxon	description	Figs 8 – 13. Hyalella aff. puna — Hankel et al., 2023	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F93675FFC9FE10F9388D31FB82.taxon	materials_examined	MATERIAL EXAMINED. Holotype. Argentina: ♂, Catamarca Province, Laguna Antofagasta, – 26.1058 ° S – 67.42058 ° W, alt. 3338 m a. s. l, 13. XII. 2015, J. Rodríguez leg., (FML-CRUST 01335), 9.8 mm. Paratypes: 1 ♀ measuring 7.35 mm, 2 ♂♂ and 1 ♀ (FML-CRUST 01336); 4 ♂♂ and 2 ♀♀ (IBN-EcoPP- 23 C); same data as holotype. Additional material: Argentina: 5 ♂♂ and 1 ♀, Salta Province, Aguas Calientes, – 24.39164 ° S – 66.56256 ° W, 3795 m a. s. l., 3. II. 2014, 3 ♂♂ and 2 ♀♀, Pastos Grandes, – 24.42852 ° S – 66.67161 ° W, 4048 m a. s. l, 3. II. 2014, 4 ♂ ♂ and 2 ♀♀, Catamarca Province, Laguna Antofagasta, – 26.10413889 ° S – 67.4185 ° W, 3331 m a. s. l, 14. XII. 2015. J. Rodríguez leg.	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F93675FFC9FE10F9388D31FB82.taxon	diagnosis	DIAGNOSIS. Body smooth. Palp of maxilla I asymmetrical, with right branch bearing two setae on tip vs. only one on left branch. Sternal gills present on pereonites 2 to 7. Epimeral plate 1 rounded; plates 2 and 3 acuminate. Uropod 3 elongated, peduncle longer than ramus; ramus thin, approximately twice as long as wide. Uropod 1 sexually-dimorphic, with male inner ramus displaying a distinct modified seta (‘ copulatory spine’ of Bousfield, 1996).	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F93675FFC9FE10F9388D31FB82.taxon	materials_examined	TYPE LOCALITY AND REFERENCE SEQUENCES. Laguna Antofagasta, – 26.1058 ° S – 67.42058 ° W, 3338 m a. s. l, Catamarca Province, Argentina. GenBank accession numbers: COI: OR 726344 (Fig. 1).	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F93675FFC9FE10F9388D31FB82.taxon	etymology	ETYMOLOGY. The term “ Inca ” in the specific epithet should be interpreted as a noun in conjunction with the generic name, in reference to the Inca Empire, which historically occupied vast areas of South America, including the highland and Puna regions.	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
4D4287F93675FFC9FE10F9388D31FB82.taxon	description	DESCRIPTION OF MALE Body: smooth. Maximum length observed 9.87 mm. Head: Eye ellipsoid, pigmented. Antenna I (Fig. 9 a, b): shorter than antenna II but longer than its peduncle. Peduncular segments 1 – 3 progressively shorter, all segments with many simple and plumose setae, along with microtrichs Ib. Flagellum with eleven articles, with groups of simple setae (type A 1) and some isolated plumose setae; aesthetascs ordinary occurring distally between articles 8 – 10. Antenna II (Fig. 9 c): less than half body length. Peduncular segments 3 – 5 bearing groups of simple and plumose setae. Flagellum comprising 14 articles each bearing distal and subdistal simple setae of type A 1. Upper lip: Ordinary, with minute setae on the distal part (Fig. 10 a). Mandible: Right mandible (Fig. 10 b) incisor 5 - denticulate (three long, two short); lacinia mobilis complex with many denticles; setal row with 4 pappose setae; molar triturative, well developed. Left mandible (Fig. 10 c) incisor broadened, 5 - denticulate; lacinia mobilis 4 - denticulate (two long, two short); setal row with six pappose setae. Lower lip: Ordinary, outer lobes covered with minute setae (Fig. 10 d). Maxilla I: Asymmetrical. Outer plate with nine robust serrate setae F 4 and setules on the inner surface. Inner plate shorter than outer one, with two apical papposerrate setae, and several marginal setules. Palp of right Maxilla I longer than wide, reaching more than half the length of the distance between the base of the palp and the apex of the outer plate, bearing two simple apical setae (Fig. 10 e). Palp of left maxilla shorter than right counterpart, with only one simple distal seta (Fig. 10 f). Maxilla II (Fig. 10 g): Inner plate slightly shorter than outer plate, with 2 unequal strong pappose setae on inner margin; outer and inner plates with simple and plumose setae distally and few setules on the surface. Maxilliped (Fig. 10 h): Inner plate with three apical robust cuspidate setae; distal and medial margins with plumose setae. Outer plate ovate, longer than first segment of palp; distal and medial margins with simple setae. Palp longer than plates, 4 - segmented; segment 3 slender, longer than wide; segments 1 – 3 bearing both simple and serrated setae on medial margin and lateral margins; segment 4 unguiform, shorter than segment 3, with simple setae shorter than nail placed distally. Gnathopod I (Fig. 11 a): Subchelate, coxal plate longer than wide, margin with small simple setae (type Ia). Basis hind margin with a single simple seta; basis, ischium and merus with denticles type T 1 on margins. Posterior margin of basis and ischium with groups of 5 serrated setae. Carpus longer than wide, posterior pectinate lobe bordered with serrate setae. Propodus (Fig. 11 b) longer than broad, hammer-shaped, anterodistal margin with A 1 - type simple setae, inner face with 10 – 11 serrate setae type F 3 arranged obliquely; palm margin bearing a subrectangular hump near the dactylus, lined with A 1 - type setae; palm angle with T 1 - type denticles, and two cuspidate setae with accessory seta. Dactylus with T 1 - type denticles. Palmar Index (sensu Ruffo [1973]) = 0.37. Gnathopod II (Fig. 11 c): Subchelate. Coxal plate longer than wide. Basis, ischium and merus with groups of simple setae on posterior margin. Carpus subtriangular, notably shorter than propodus. Propodus ovate, with oblique palm; palm margin bordered with several rows of simple setae; palm angle with two cuspidate setae and T 1 - type denticles. Dactylus claw-like, congruent with the palm. Palmar Index (sensu Ruffo [1973]) = 0.43. Pereiopods 3 and 4 (Fig. 12 a, b): Similar in size. Coxal plates: pereiopod 3 subrectangular, longer than wide; pereiopod 4 broad, excavated posteriorly, 1.2 x as long as wide; both coxal plates with margins lined with thin simple setae type Ia; posterior margin of basis, ischium, merus, carpus and propodus with simple or cuspidate setae; dactylus elongated, approximately ½ length of propodus. Pereiopods 5 – 7 (Fig. 12 c – e): Pereiopod 5 shorter than pereiopods 6 and 7, with the last two being equal in length. Coxal plate of pereiopod 5 bilobated, wider than long, with posterior lobe deeper than anterior lobe; coxa of pereiopod 6 as long as wide, with significantly reduced anterior lobe; coxa of pereiopod 7 wider than long; all coxal plates with thin simple setae along their margins (type Ia). Basis of pereiopods 5 – 7 expanded and finely serrated, anterior and posterior margin of ischium, merus, carpus and propodus with simple or cuspidate setae and few microtrichs type Ib. Dactylus of all limbs elongated, similar to pereiopods 3 – 4. Coxal gills: Sacciform, present on gnathopod II to pereiopod 6 (Fig. 12 a – d). Sternal gills also sacciform but shorter, present on pereonites 2 to 7 (Fig. 12 a). Pleopods: Biramous. Peduncle with pair of retinacula. Rami multiarticulate, provided with long plumose setae (Fig. 13 a). Uropod 1 (Fig. 13 b): Peduncle longer than rami, with four dorsal cuspidate setae aligned in a longitudinal row and other three cuspidate setae on dorsolateral and dosomedial distal margin. Rami subequal in length with three dorsal cuspidate setae; inner ramus with seven distal setae, one of which notably elongated, slender and slightly curved, surpassing tip of ramus (‘ copulatory spine’ sensu Bousfield [1996]); outer ramus with five distal setae, one of them larger than rest. Uropod 2 (Fig. 13 d): slightly shorter than peduncle of uropod 1. Peduncle slightly longer than rami. Peduncle and both rami each with three dorsal cuspidate setae. Outer ramus with seven distal cuspidate setae, one notably longer and more robust than rest; inner ramus bearing five distal cuspidate setae, one of which longer and stronger than rest. Uropod 3 (Fig. 13 e): subequal in length to peduncle of uropod 2; peduncle rectangular, wider and longer than ramus, with six robust distal setae and two additional marginal setae, all cuspidate. Outer ramus basal width nearly 2.5 times width at tip of ramus, with six to seven simple setae and one shorter cuspidate seta distally; another group of subdistal setae placed close to apex consisting of row of four long, thin simple setae (left uropod 3; Fig. 13 f) or only one seta (right uropod 3) (Fig. 13 e). Telson: subrectangular, with two widely spaced, long simple setae on distal margin (setae serrate in one of male paratypes); additionally, other two short plumose setae placed subdistally on each side (three setae in one of male paratypes) on dorsal surface of telson (Fig. 13 g, h). Epimeral plates (Fig. 13 i): Plate 1 is rounded posterodistally; Plates 2 and 3 are acuminate posterodistally with angle strongly produced. Intraspecific variability in males: Variations were observed, including differences in the setation of ramus of uropod 3, as outlined in the main description. Additionally, in one male an apparent notch was observed on coxa 5, and two setae were absent on the anterodistal part of the gnathopod I propodus. Some individuals exhibited 13 articles in antenna II flagellum (14 in holotype). Further variations were noted in the number and type of setae on the telson, as described in the main text. FEMALE (PARATYPES). Maximum body length observed 7.32 mm. Female gnathopod II propodus (Fig. 11 d) smaller and slenderer than in male, with five serrate setae on the inner face. Oostegites subtriangular, featuring curled setae along margin (Fig. 11 e). Female Uropod 1 without modified seta (‘ copulatory spine’) on inner ramus (Fig. 13 c). TAXONOMICAL REMARKS Hyalella oscari sp. n. was discovered in the Puna and High Andes ecoregions, specifically in Catamarca and La Rioja provinces to the east of the Andes, Argentina, at elevations ranging from approximately 3900 to 4400 m a. s. l. This species bears a close resemblance to Hyalella fatimae Isa-Miranda et Peralta, 2022, yet it can be primarily distinguished by distinct morphological features. Notably, H. oscari sp. n. is characterized by the morphology and chaetotaxy of maxilla I palp, particularly the presence of two plumose setae vs. only one seta present in H. fatimae, the former being a feature unique within the genus Hyalella. Additionally, in H. fatimae, the antenna II extends notably longer than the head, about 25 % of the body length, whereas in H. oscari sp. n., it is only slightly longer. The propod of male gnathopod I of H. oscari sp. n. has a slightly concave palm margin gradually increasing in height towards the palmar angle (vs. it is regularly convex in H. fatimae). The excavation of coxa 4 in H. oscari sp. n. is more pronounced than in H. fatimae, and the former exhibits four cuspidate setae on the palm angle (vs. three in H. fatimae). Hyalella oscari sp. n. also shows resemblances to H. fossamancinii Cavalieri, 1959, also reported in the Puna and High Andean region. However, notable differences exist, particularly in maxilla I: in H. fossamancinii the palp is straight and bears only one simple distal seta, whereas H. oscari sp. n. features a slightly arched palp with a constriction and two plumose setae on tip. Additionally, regarding the setation on the peduncle of uropod 3, H. oscari sp. n. bears numerous fine marginal setae, which are absent in H. fossamancinii. The shape of gnathopod I propodus male differs between the species, with H. fossamancinii having a straight palm margin while H. oscari sp. n. exhibits a sinuous one. Hyalella oscari sp. n. is further distinguished from both H. fatimae and H. fossamancinii by the presence of two short external setae on the basis of pereopod 7, a feature not observed in the other species. The only species exhibiting this trait is Hyalella gonzalezi Jaume, 2021, endemic to Lake Titicaca, yet it differs primarily due to differences in uropod 3 setation, the distinctive maxilla I palp of H. oscari sp. n., and the longer and sharper coxa 4 in H. gonzalezi compared to H. oscari sp. n. Additionally, the body of H. gonzalezi presents a faint but distinct transverse hump along the posterodorsal margin of pereionites and pleonites, a feature not observed in H. oscari sp. n. In molecular phylogenetic analyses, H. oscari sp. n. is genetically closely affiliated with H. armata, H. krolli, and H. franciscae. It is worth mentioning that H. oscari sp. n. displays a ‘ smooth’ body whereas H. armata (endemic to Lake Titicaca) exhibits extremely elongated, laterally directed spines on each of the pereiopodal coxal plates I – IV. In comparison to H. franciscae (found in Patagonia, Chile, and southern South America), similarities were noted in the length of palp of maxilla I and setae on peduncle of uropod 3. However, distinctions arise in the length of uropod 3 ramus, a more ‘ triangular’ male propod of male gnathopod II, and presence of 16 setae on the inner face of propodus of gnathopod I. In contrast to H. krolli (from Lake Titicaca), similarities were observed in the length of palp of maxilla I, but differences were evident, as H. krolli has a compact body, shorter antennae I and II, and notably elongated and narrow coxal plates. Hyalella inca sp. n. was found in the Puna and High Andes ecoregions, precisely within the Salta and Catamarca provinces, situated to the east of the Andes, at elevations ranging from approximately 3300 to 4000 m a. s. l. This species exhibits several similarities to H. puna Peralta et Isa-Miranda 2019, which initially led to its designation as “ Hyalella aff. puna ” in the study conducted by Hankel et al. [2023]. However, there are several diagnostic traits enabling the differentiation of both species. Notably, some individuals of H. puna exhibit posterodorsal flanges on pleonites I – III, while other individuals of the same species have a smooth body. In contrast, H. inca sp. n. possesses a consistently smooth body (therefore, this feature cannot be used to distinguish these two species). Furthermore, in H. inca sp. n., the right maxilla I palp is longer than in H. puna, and it features two simple setae at the apex, as opposed to H. puna, which has only one. These two setae were also observed in Hyalella echinus (Faxon, 1876) from Lake Titicaca, although with significant differences, primarily associated with body structure, as H. echinus has spines on each body somite. The left and right maxilla I are similar in H. puna, while in H. inca sp. n., they are asymmetrical. Concerning the setation of male gnathopod I propodus, H. inca sp. n. features two reduced setae on dorsal margin, in contrast to H. puna, which shows an unarmed margin. Additionally, H. inca sp. n. has a notably larger uropod 3 ramus, with a basal width exceeding twice the height of the ramus, whereas H. puna maintains a 1.7 ratio of base width to ramus height. Another distinguishing trait is the presence of a row of setae on the ramus of uropod 3 in H. inca sp. n., which is absent in H. puna. H. inca sp. n. possesses also a modified seta on the inner ramus of uropod 1, not found in H. puna. In molecular phylogenetic trees, H. inca sp. n. is closely related to H. kochi, H. montforti, and H. simplex. They share the modified seta on the inner ramus of the male uropod 1. This curved seta is a diagnostic morphological character of the “ curvispina species complex ” used by Bousfield [1996] to propose the subgenus Hyalella (Mesohyalella). The new species shares similarities with H. montforti (Lake Titicaca) in the overall morphology of the male gnathopod II and male gnathopod I propodus. They differ primarily in the distinctive the dorso-posterior flanges on peraeon segments 7, pleonites 1, 2, and 3 of H. montforti (compared to the smooth body of H. inca sp. n.), and the size and shape of the peduncle and ramus of uropod 3, which in H. montforti is much smaller and stouter than in H. inca sp. n. Compared to H. simplex (Southern Chile), there are similarities in the morphology and setation of the telson, as well as in the long palp of maxilla I. However, distinctions arise in the morphology and setation of uropod 3, and it is noteworthy that H. simplex exhibits sternal gills on somites 3 to 7. Similarities with H. kochi and the new species extend to the morphology of the propodus of male gnathopod I. However, notable differences are primarily observed in the reduced length of palp of maxilla I, the equal length of ramus and peduncle of uropod 3, and the presence of sternal gills on somites 3 to 7 in H. kochi. PHYLOGENETIC ANALYSES Our phylogenetic analyses include a total of 36 species of both Hyaloidea (with 4 families represented) and Talitroidea (with 2 families represented) (Table 2). When considering South American species of Hyalella, there have been identified four clades (we maintained the same terminology for these clades as proposed previously by Adamowicz et al. [2018]). Clade A, housing H. kochi González et Watling, 2001, H. nefrens González et Watling, 2003, H. longipalma (Faxon, 1876), H. cuprea (Faxon, 1876), and H. hirsuta Jaume, 2021, was strongly supported only by Bayesian inference (BI: 100) and weakly supported by maximum likelihood (ML: 79). Clade C (BI: 100, ML: 97) including H. franciscae González et Watling, 2003, H. gonzalezi Jaume, 2021 in Jaume et al. [2021], K. krolli Jaume, 2021 in Jaume et al. [2021], H. armata (Faxon, 1876) plus the new species H. oscari. Clade D (BI: 100, ML: 95) comprised species exclusively confined to the altiplano (Titicaca), namely H. tiwanaku González et Watling 2003, H. longipes (Faxon 1876), and H. neveulemairei Chevreux 1904. Clade E (BI: 100, ML: 98) including H. montforti Chevreux 1907, H. simplex Schellenberg 1943, H. kochi González et Watling 2001, and the new species H. inca. All analyses agreed on locating the two new species within the clades C and E respectively (Fig. 14 a, b).	en	Isa-Miranda, Águeda Verónica, Peralta, Marcela A., González, Juan Cruz, Nieto, Carolina (2025): Two new Hyalella (Amphipoda: Hyalellidae) from the Puna and High Andean ecoregions of South America. Arthropoda Selecta 34 (1): 17-40, DOI: 10.15298/arthsel.34.1.02
