Leiostracus ferreirai ( Palma & Brito, 1974 ) comb., 2013

Salvador, Rodrigo Brincalepe & Simone, Luiz Ricardo Lopes De, 2013, Taxonomic Revision Of The Fossil Pulmonate Mollusks Of Itaboraí Basin (Paleocene), Brazil, Papéis Avulsos de Zoologia 53 (2), pp. 5-46 : 5-46

Genus Leiostracus Albers, 1850 Leiostracus ferreirai ( Palma & Brito, 1974) comb.

nov.

( Figs. 51-58 )

Bulimulus ferreirai Palma & Brito, 1974: 393 (pl. 2, fig. 1, 6); Breure, 1979: 137; Simone & Mezzalira, 1994: 50 (pl. 15, fig. 421); Rodrigues & Fonseca, 2007: 253.

Itaborahia ferrairai : Breure, 1978: 238.

Bulimulus fazendicus : Bergqvist et al., 2006: 57. (in synonymy, non Maury, 1935).

Holotype: DGM 5409-I (examined; Fig. 56 ).

Paratype: MNRJ 5186 -I (1 specimen, examined; Figs. 57-58 ) .

Type Locality: Limestones of Parque Paleontológico de São José de Itaboraí, Rio de Janeiro, Brazil. Park’s center coordinates: 22°50’20”S, 42°52’30”W .

Geographic and stratigraphic occurrence: Known only from the type locality: Sequences S1 and S2 ( Medeiros & Bergqvist, 1999; Bergqvist et al., 2006).

Age : Tertiary, Middle Paleocene.

Etymology: Species dedicated to Prof. Cândido S. Ferreira (Museu Nacional, Rio de Janeiro, Brazil).

Diagnosis: Shell small. Protoconch with fine axial ribs. Aperture rounded and diagonally elongated.

Re-Description: Shell small, conical-oval, with an acuminated apex; 7 whorls. Greatest width on last whorl; width ~⅔ shell length. Spire angle ~55°. Protoconch with 1½ whorl, pointed, sculptured by fine axial ribs; transition to teleoconch clear. Teleoconch smooth, except for growth lines. Profile of whorls convex. Suture well-marked, slightly oblique (diagonal) to columellar axis; less oblique (approximately horizontal) on first whorl. Aperture medium-sized, orthocline, rounded, diagonally elongated; aperture ~3/5 shell width. Lamellae and teeth absent. Peristome complete, reflect- ed; more strongly reflected in columellar region. Body whorl with bottom slightly flattened; ~½ shell length. Umbilicus narrow, partially covered by peristome.

Measures (in mm): Holotype: 6 whorls (shell apex and aperture broken); H = 9.7; S = 6.2. Paratype: 7 whorls; H = 10.8; D = 6.7; S = 7.2. Figured specimen (DGM 4993-I): 7 whorls; H = 12.2; D = 7.2; S = 7.7; h = 4.5; d = 4.2.

Examined material: Types. DGM 4993 -I (4 specimens) .

Discussion: This species was originally described as Bulimulus ferreirai by Palma & Brito (1974). These authors offered a diagnosis to differentiate the species from Bulimulus fazendicus : more convex whorls and a well-marked suture. Ribeiro (2003) proposed the synonymy between these two species, but has done it in a congress abstract, which is not valid according to Article 9.9 of the ICZN (1999). However, the work of Ribeiro (2003) is cited by Bergqvist et al. (2006), making the synonymy valid. In any case, no one has explained the decision in favor of the synonymy. Besides, the only later work dealing with this species is a short note, and it maintained the two species as distinct ( Rodrigues & Fonseca, 2007). Therefore, as the species present significant differences between them, such synonymy is not accepted here. Additionally, after analyzing a greater number of well-preserved specimens, we decided for the reallocation of the species in the genus Leiostracus Albers, 1850 . This is an additional indication of the differences between this species and B. fazendicus . Leiostracus is a recent genus and its distribution reaches from Guyana and Suriname to the states of Minas Gerais and Espírito Santo, in Brazil ( Breure, 1979; Schileyko, 1999a; Simone, 2006).

Until now there were only two known specimens of Leiostracus ferreirai : the type material. The holotype ( DGM 5409-I) has a broken aperture and approximately one third of the body whorl is broken (seen by the scar left in the previous whorl; Fig. 56 ). The paratype ( MNRJ 5186-I) is not an adult, lacking a reflected lip ( Fig. 57-58 ). This makes the shell smaller and does not allow the study of important characters for taxonomy such as the shell aperture. However, specimens in an excellent preservational state were found in the collections ( DGM 4993-I; Figs. 51-55 ), erroneously identified as B. fazendicus . The analysis of these new specimens made the generic reallocation possible.

Leiostracus ferreirai has some of the typical characters of the genus: a conical shell with the sides of the spire straight, the protoconch sculptured by fine axial ribs, a strongly marked suture, the aperture diagonally elongated, and a thickened lip. Breure (1978) had already noticed that the protoconch of L. ferreirai (which he calls Itaborahia ferreirai ) had axial ribs. L. ferreirai differs from the other species in the genus by its smaller size, greater number of whorls for its size, and more convex whorls. Besides, L. ferreirai can be easily differentiated of B. fazendicus by its smaller size, a larger, rounded and diagonally elongated aperture, a more strongly reflected lip and the two characters already pointed by Palma & Brito (1974): more convex whorls and a better-marked suture.

Subfamily Odontostominae

Genus Cyclodontina Beck, 1837 Cyclodontina coelhoi ( Palma & Brito, 1974) comb. nov.

( Figs. 59-61 )

Bulimulus coelhoi Palma & Brito, 1974: 396 (pl. II, figs. 2, 4); Breure, 1979: 137; Simone & Mezzalira, 1994: 50 (pl. 15, fig. 419).

Itaborahia coelhoi : Bergqvist et al., 2006: 58 (fig. 67).

Holotype: DGM 5410-I (examined; Fig. 61 ).

Paratype: MNRJ 5187 -I (1 specimen, examined; Figs. 59-60 ) .

Type Locality: Limestones of Parque Paleontológico de São José de Itaboraí, Rio de Janeiro, Brazil. Park’s center coordinates: 22°50’20”S, 42°52’30”W .

Geographic and stratigraphic occurrence: Known only from the type locality: Sequence S1 ( Medeiros & Bergqvist, 1999; Bergqvist et al., 2006).

Age : Tertiary, Middle Paleocene.

Etymology: Species dedicated to Prof. Arnaldo C.S. Coelho (Museu Nacional, Rio de Janeiro, Brazil).

Diagnosis: Shell small, smooth. Whorls with a weakly raised fold on its central or upper portions. Aperture more laterally positioned. Single columellar lamella.

Re-Description: Shell small to medium-sized, conical, slightly fusiform. Greatest width on body whorl; width ~2/5 shell length. Spire angle ~40°. Protoconch dome-shaped, blunt, smooth; transition to teleoconch unclear. Teleoconch smooth, except for growth lines. Suture well-marked, oblique (diagonal) to columellar axis. Profile of whorls flat. Central portion of first whorls raised, forming a weakly raised fold; same pattern present on other whorls, but on upper portion only. Aperture medium-sized, slightly prosocline, oval and vertically elongated; ~3/5 shell width and ~2/5 shell length. Peristome thickened and reflected, more markedly on basal and columellar regions. Columellar spiral lamella strong and raised, extending itself towards interior; outer portion of lamella more prominent (“bilobate” sensu Palma & Brito, 1974). Body whorl ~½ shell length. Umbilicus almost completely obstructed by peristome.

Measures (in mm): Holotype: 8 whorls; H = 15.3; D = 5.7; S = 9.1; h = 6.1; d = 3.4. Paratype: 7 whorls; H = 11.7; D = 4.7; S = 7.2; h = 4.3; d = 2.7.

Examined material: Types.

Discussion: This species was originally classified in the genus Bulimulus by Palma & Brito (1974) and posteriorly transferred to the genus Itaborahia due to its supposed columellar fold ( Ribeiro, 2003; Bergqvist et al., 2006). However, both generic attributions are mistaken. Besides its aperture and shell shape being completely different from Bulimulus , it also has a columellar lamella. The same holds true when comparing it to Itaborahia and, additionally, its strong columellar lamella is totally distinct from Itaborahia ’s simple columellar fold (and it is also located in a distinct region).

This species shares many similarities with the genus Cyclodontina Beck, 1837 and thus we propose here the new combination Cyclodontina coelhoi . Cyclodontina is a recent and diverse Odontostominae genus, occurring in tropical and subtropical regions of South America, including Brazil ( Simone, 2006). The typical features of Cyclodontina displayed by C. coelhoi are: a conical and slightly fusiform shell shape, flat whorls, incomplete (absent in parietal region) and reflected peristome, aperture oval and vertically elongated, and the presence of a strong columellar lamella. C. coelhoi differs from the other species in the genus by its small size, smooth shell, whorls with a weakly raised fold, aperture positioned more laterally, and by having only the columellar lamella (without other teeth or lamellae).

Despite shell sculpture being commonplace in the genus, there are several species with smooth shell as, for example, C. catharinae (Pfeiffer, 1856) and C. tudiculata (Martens, 1868) . Other Cyclodontina species show a strong columellar lamella, similar to what is found in C. coelhoi , but they have at least two more teeth/lamella in their apertures. As C. coelhoi has only the columellar lamella, it is plausible to suppose that, due to this fossil’s old age, the lamella has been the first structure to appear in the genus’ history; the other teeth and lamellae would have appeared later. The strong and raised lamella of C. coelhoi is a typical barrier to obstruct the aperture, protecting the animal against predators ( Solem, 1972; Goodfriend, 1986; Stanley, 1988; Vermeij, 1993; Gittenberger, 1996; Barker & Efford, 2004).

Figures

FIGURES 51-58: 51-55. Leiostracus ferreirai (DGM 4993-I); shell length 12 mm. 51-53. Overview. 54. Umbilicus. 55. Protoconch. 56. L. ferreirai (DGM 5409-I; holotype); shell length 9.5 mm. 57-58. L. ferreirai (MNRJ 5186-I; paratype); shell length 11 mm.

FIGURES 59-69: 59-60. Cyclodontina coelhoi (MN 5187-I; paratype); shell length 11.5 mm. 61. C. coelhoi (DGM 5410-I; holotype); shell length 15.5 mm. 62-65. Plagiodontes aff. dentatus (MCT 6944-I); shell length 9.5 mm. 66-67. Eoborus rotundus (MCT 6942-I; paratype); shell length 25.5 mm. 68-69. Eoborus rotundus (MCT 6943-I; paratype): shell length 25.5 mm.