INTRODUCTION

In 1868, Pellegrino Strobel wrote his first comments about the continental mollusks of the Argentine Precordillera of Mendoza province. A few years later, in the same area, the author described a new species of Scolodontidae H.B. Baker, 1925, Hyalina (Ammonoceras) argen tina Strobel, 1874, classified as Streptaxidae Gray, 1860. With no new specimens, ^{Doering (1877}) transferred the species to his new sub genus, Streptaxis (Scolodonta) Doering, 1877; a few years later, ^{Tryon (1885}) combined it to Streptaxis (Ammonoceras) L. Pfeiffer, 1855 (a synonymous junior of Happia Bourguignat, 1889 (Worms, 2020). In 1920, Frenguelli called Scolodonta argentina to fossil specimens from Pleistocene and Holocene of Córdoba and Entre Ríos (Argentina), but the specific identity of them is dubious (^{Miquel & Aguirre, 2011}).

The Scolodontidae is an interesting group of landshells inhabiting Central and South America, with numerous living species; recent studies con sider it a clade of gastropods pulmonate (^{Ramírez et al., 2012}; Worms, 2020). Systrophia L. Pfeiffer, 1855 is a characteristic genus of tropical areas of Venezuela, Colombia, Ecuador, Peru, Brazil and Bolivia (Ramírez et al., 2012, fig. 10), with spe cies of large and thin shells, and spire very low.

Several species of this family have an al most transparent shell, with a very colored body (white, yellow, orange or red). These spe cies are carnivorous; they eat worms and oth er snails, being active and voracious (^{Ramírez, 1993}). In Argentina, the family Scolodontidae includes the genera Scolodonta^{Doering, 1875}, Happia Bourguignat, 1889, Drepanostomella Bourguignat, 1889, Miradiscops H.B. Baker, 1925 and Wayampia^{Tillier, 1980} (^{Fernández, 1973}; Ramírez, 1993; ^{Miquel et al., 2007}; ^{Hausdorf, 2006}). Wayampia was later synonymized to Scolodonta (Bank, 2017). Happiela H.B. Baker, 1925 has been recorded by Ramírez (1993) for Argentina, but this mention is dubious. Here, Systrophia argentina (^{Strobel, 1874}) n. comb. is re-described, based on new materials from the Precordillera of Mendoza province, Argentina. This is the first record of the species in the last 150 years and the first reliable cite of the genus Systrophia L. Pfeiffer, 1855.

MATERIALS AND METHODS

The specimens were housed in the Invertebrates Division of the Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” (MACN-In), Buenos Aires, Argentina. They are stored in ethanol 70%. The images of the rad ula were obtained in the Service of Scanning Electronic Microscopy of the MACN (Phillips XL Series 30), previously metalized with gold-palla dium. The classification of Worms (2020) is fol lowed; the number of whorls was counted accord ing to ^{Kerney & Cameron (1979}).

RESULTS

Scolodontidae

Systrophia L. Pfeiffer, 1855

Systrophia argentina (^{Strobel, 1874}) n. comb.

(Figs. 2-3)

Fig. 2 A-F: Systrophia argentina (^{Strobel, 1874}). MACN-In 42446. Quebrada San Isidro, 2.050 masl. Precordillera Mendoza province, Argentina. A. Apical view. B-C. Apertural view. D. Umbilical view. Radula. E. General view. F. Detail of central plate. 

Fig. 3: Systrophia argentina (Stro bel, 1874). MACN-In 42446. Que brada San Isidro, 2.050 msnm. Precordillera, Mendoza province, Argentina. Genital apparatus. 

Hyalina (Ammonoceras) Argentina^{Strobel, 1874}: 9, Tav. 1, Fig. 1.

Streptaxis (Scolodonta) Argentina^{Doering, 1877}: 310.

Streptaxis (Scolononta) (sic) Argentina^{Doering, 1878}: 229.

Streptaxis (Ammonoceras) Argentina^{Tryon, 1885}: 66, pl. 13, Figs. 58-60.

? Scolodonta argentina^{Frenguelli, 1920}: 162, 249.

? Scolodonta argentina^{Miquel & Aguirre, 2011}: 123, Fig. 35.

Diagnosis. Shell small, planispiral, 5- 6 whorls, protoconch with almost 2 whorls; radula with teeth aculeate, formula: 13 - C - 13; vagina and atrium short; spermathecal duct reaching the distal extreme of the vagina; penial sheath with some circumvolutions; penis occupying most of the penial sheath; large and quadrangular gland (“penial gland”) attached to the distal extreme of the penial sheath.

Description. Shell small (6 - 4.55 mm in adult stage), planispiral, 5.00 - 5.50 whorls, semitransparent (height low (2.00 - 1.69 mm), almost smooth, slow growth, suture deep, um bilicus large and perspective (1.95 - 1.82 mm), aperture circular (1.43 - 1.30 mm), peristome slightly expanded, superior edge of the peri stome a bit descendent and oblique, growth lines scarcely marked, more marked on the first adult whorls, body yellowish, protoconch with almost 2 whorls, smooth (Fig. 2A-D, Table 1). Radula with central plate tricuspid, and latero-marginal teeth aculeate, typical of the family: 13 - C - 13 (Fig. 2E-F). Genital tracts very long and slim. Gonadal hermaphrodite acini cream, spermathe ca ( or seminal vesiculae) and hermaphroditic duct typical ones; spermioviduct, albumen gland and prostate elongated; fertilization sac medium size; long and convolutioned free oviduct; vagina short (oviduct + vagina: 2.75 mm aprox.); sper matheca claviform, spermathecal duct very long (3.5 mm aprox.), reaching the distal extreme of the vagina, near the atrium; long penial sheath, with some circumvolutions; penis occupying most of the penial sheath, vas deferent penetrat ing laterally at the base of the penis; epiphallus with a retractor muscle adhered to its extreme (epiphallus + penial sheat: 4 mm aprox.); large and quadrangular gland (“penial gland”) at tached to the distal extreme of the penial sheath, with some sustentor muscles, the walls of this gland are internally fimbriated; atrium very short (Fig. 3; Table 1).

Table 1 Measurements of Systrophia argentina (^{Strobel, 1874}) (*shell and body lost, dissected for radula and genitalia). 

Typical locality. “Angostura” or “garganta” (gullet) of Villa Vicencio and Casa de Piedra, Precordillera, Argentina (here restricted) (Fig. 1).

Fig. 1: Location of area where the species were found (▲) and the typical locality restricted (“Angostura” or “garganta” of Villa Vicencio and Casa de Piedra, Pre cordillera, Argentina) (●). 

Distribution. Argentina: Mendoza province: Precordillera, ca. 2,000 m. Found on the ground with Artemisia echegarayi Hieron. (Asteraceae) and specimens of Scolodonta semperi^{Doering, 1875} (Fig. 1).

Materials studied. S. argentina: MACN-In 42446. Argentina: Precordillera, Mendoza province. Quebrada San Isidro, 2,050 m asl. 4/ IV/1983. C. and A. Roig. 3 exs. in ethanol (1 ex. complete, 2 exs. dissected with their soft parts, and 1 radula metallized. S. semperi. MACN-In 42284. Similar locality. 2 exs. in ethanol. S. cere onitens Haas, 1951. MACN-In 29466. N-Peru, to the south of San Ignacio, valley of the Chinchipe river. Col. and det. W. Weyrauch. 5 exs.

Taxonomic remarks. The type series is lost. ^{Strobel (1874}) described this Argentine species based on specimens larger than those here an alyzed (6 mm). ^{Frenguelli (1920}) cited this spe cies for the Ensenadan (“pre-bonaerian”) age -middle Pleistocene- from the cities of Córdoba (Córdoba province) and Paraná (Entre Ríos prov ince), and in recent loess in Paraná; however, the specimens studied by this author are not co-spe cific with S. argentina and could be a species of Scolodonta (^{Miquel & Aguirre, 2011}). So far, S. argentina has not been found in the other areas indicated by Strobel (1874): Napostá Grande val ley and Sierra de la Ventana (Buenos Aires prov ince). Thus, it is considered necessary to restrict the typical locality to the localities of Mendoza province.

Hyalina (Ammonoceras) argentina is includ ed in the genus Systrophia due to the following features: shell discoid, whorls that grow slowly, last whorl not larger than previous whorls, ap ertural teeth absent, genital ducts very long and thin, similar to generic model (^{Ramírez, 1993}). Now, Hyalina S. Studer, 1820 is a synonym of Vitrina Draparnaud, 1801 (Vitrinidae Fitzinger, 1883), and Ammonoceras L. Pfeiffer, 1855 is a synonym of Happia (Zilch, 1960; Bank, 2017).

An uncommon feature found in S. argentina is the penial gland (Fig. 3). This large gland does not seem to be present in other genera and spe cies of Scolodontidae; an “atrial gland” of similar location has been described in Tamayoa sp. (from uncertain locality) (^{Ramírez, 1993}), whereas an “organe amatorial” (“organ of love”) has been described in T. (Tamayops) decolorata (Drouët, 1859), from Cayenne (French Guiana) (^{Tillier, 1980}). The former structure could be homolo gous to the gland of S. argentina, not so the lat ter, which has an apparent mechanical, not glan dular, function.

Systrophia argentina is different from Scolodonta spp. in the larger size, more num ber of whorls, and the planispiral coiling. S. semperi, which inhabits north and central Argentina, has a smaller discoid shell, genital ducts thickened, atrium long, vagina short, and deferent duct inserted in the proximal extreme of the epiphallus (^{Hylton Scott, 1945}; ^{Hausdorf, 2006}). S. argentina is different from the species of Happia in the shell morphology, which, in the latter is subcircular to subdiscoidal, with whorls with fast growing (^{Ramírez, 1993}). The species of Happia found in Argentina are H. skiaphila (d’Orb., 1835) and H. ordinaria (Smith, 1881) (Hylton Scott, 1948, 1972). The former species lives in the north of the country, measures 11 mm, has 7 whorls and genital ducts thick and convolutioned, principally those of the male via (Hylton Scott, 1948), and was classified as Wayampia by Ramírez (1993). Happia ordina ria, from Patagonia, has a width of 3 mm, 3.5 whorls with fast growing, and radula with the formula 12 - C - 12, where there are lateral teeth tricuspid and monocuspid (Hylton Scott, 1972), very different from those of S. argentina.

The austral distribution of Systrophia reach es Bolivia (^{Ramírez, 1993}; Ramírez et al., 2012), so, S. argentina could be considered a relict spe cies, surviving in a warm and slightly humid mountainous area, being the distribution more austral for the genus. According to ^{Strobel (1874}), this species coexists with Bostryx men dozanus (Strobel, 1874), B. cordillerae (Strobel, 1874) and B. cuyana (Strobel in Pfeiffer, 1867) (^{Breure, 1979}; ^{Miquel, 1995}).