Itaborahia Maury, 1935

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 Itaborahia Maury, 1935

( Figs. 43-50 )

Itaborahia Maury, 1935: 9 ; Oliveira, 1936: 5; Magalhães & Mezzalira, 1953: 220; Trindade, 1956: 13; Parodiz, 1969: 182; Breure, 1978: 236; 1979: 137; Bergqvist et al., 2006: 58.

Itaborahya (error): Mezzalira, 1946: 18.

Bulimulus ? ( Itaborahia ): Zilch in Wenz, 1959-60: 485. (in synonymy, non Leach, 1814).

Bulimulus : Brito, 1967: 16; Palma & Brito, 1974: 393; Simone & Mezzalira, 1994: 50; Rodrigues & Fonseca, 2007: 253. (in synonymy, non Leach, 1814).

Type species: Itaborahia lamegoi Maury, 1935 .

Included species: I. lamegoi Maury, 1935 .

Geographic and stratigraphic occurrence: Known only from Itaboraí Basin, limestone Sequences S1 and S2 ( Medeiros & Bergqvist, 1999; Bergqvist et al., 2006).

Age : Tertiary, Middle Paleocene.

Etymology: Reference to place of discovery: Itaboraí Basin.

Diagnosis: Shell fusiform. Spire apex sharply acuminated, with concave outline. Aperture prosocline. Peristome reflected, incomplete (absent in parietal region). Columellar fold in the uppermost part of the columellar region (next to parietal region). Umbilicus imperforated.

Re-Description: Shell dexterous, fusiform. Greatest width on body whorl. Profile of whorls slightly convex. Spire apex sharply acuminated, with concave outline. Suture well-marked, linear, slightly oblique (diagonal) to columellar axis. Protoconch apparently smooth; transition to teleoconch unclear. Shell smooth, except for growth lines. Aperture large, sub-oval, prosocline. Peristome reflected, incomplete (absent in parietal region). Columellar fold in the uppermost part of the columellar region (next to parietal region), extending itself towards interior. Umbilicus imperforated.

Discussion: Maury (1935) has created the genus Itaborahia , classifying it in Bulimulinae , in order to house one of the new species found in Itaboraí Basin, I. lamegoi . Maury (1935) pointed the similarity between the new species and the genera Rhinus Martens in Albers, 1860 and Neopetraeus Martens, 1885 , but has decided to create a new genus due to the presence of a “prominent fold in the columella”.

The genus was maintained until Zilch (1959 -60) has put it in doubt, presenting Itaborahia as a possible subgenus of Bulimulus . Brito (1967) followed Zilch (1959 -60), but did not maintain Itaborahia as a subgenus; instead, treated it as a synonym of Bulimulus and referred to the type species as Bulimulus lamegoi . Additionally, Brito (1967) also described the new species B. carvalhoi . A couple of years later, Parodiz (1969) maintained Itaborahia as a valid genus due to the columellar fold, but including only I. lamegoi in the genus; showing that he possibly did not know the work of Brito (1967). Ferreira & Coelho (1971) maintained the synonymy with Bulimulus and described one more species, B. trindadeae . Later, Palma & Brito (1974) described the new species B. coelhoi , also maintaining the synonymy, but citing the columellar fold for B. lamegoi , B. carvalhoi , B. trindadeae and B. coelhoi .

Ribeiro (2003) has revalidated the genus Itaborahia , but has done so in a congress’ abstract, which has no validity according to Article 9.9 of the ICZN (1999). Moreover, Ribeiro (2003) transferred the four species cited above to the genus Itaborahia ; however, she did not explain the reason of the revalidation and the reallocation. In any case, the work of Ribeiro (2003) is cited and accepted by Bergqvist et al. (2006), thus validating these nomenclatural acts, resulting in the combinations I. lamegoi , I. carvalhoi , I. trindadeae and I. coelhoi . Bergqvist et al. (2006) indicate the columellar fold as the character responsible for the genus revalidation. Still, the only later work dealing with these mollusks is a short note, and it maintained the synonymy of Itaborahia with Bulimulus ( Rodrigues & Fonseca, 2007) . The revalidation of Itaborahia is accepted here, by the reasons explained below, but containing only the type species, I. lamegoi . Moreover, the genus description and diagnosis are complemented.

Shell shape: In a general way, Itaborahia ’s shell has typical orthalicid shape and, more specifically that of Bulimulinae . Maury (1935) commented about the similarity between Itaborahia and Rhinus , but such similarity is treated with caution here. Rhinus has a more oval and broader shell, its aperture is not prosocline and it does not have a columellar fold. Besides, Rhinus has a pilose periostracum, a character that unfortunately is not preserved in the fossil record. Moreover, the apex of the shell of Itaborahia is very characteristic, sharply acuminated and with a somewhat concave outline. Some species of the genus Corona Albers, 1850 have an acuminated apex, but have a straighter outline, never concave.

Sculpture: Protoconch sculpture is an important character in orthalicid taxonomy, especially for the Bulimulinae ( Breure, 1979; Schileyko, 1999a). All known specimens of Itaborahia display smooth shell, including the protoconch. This can be a diagnostic feature of the genus but, despite the apparently good preservation state of the fossils, it could also be a preservation artifact, since this kind of sculpture is very delicate and can be easily erased during fossil diagenesis.

Aperture, peristome and lamellae: The closest genus to Itaborahia is perhaps Bulimulus , since so many authors have treated them as synonyms. However, such similarity is not as deep as it seems, especially when the aperture is taken into account. Itaborahia ’s aperture is completely distinct: (1) it is sub-oval, with an expand- ed and reflected peristome, two features uncommon but not unheard of in the family; (2) the most striking feature however is its prosocline aperture, a rare character in orthalicids. Moreover, Itaborahia has a columellar fold, the very character used by all authors who maintained it as a distinct genus from Bulimulus ( Maury, 1935; Parodiz, 1969; Ribeiro, 2003; Bergqvist et al., 2006). However, similar folds have been found in other orthalicids as, for example, in the genus Drymaeus Albers, 1850 . Therefore, it is regarded that only the columellar fold is not enough for the definition of Itaborahia as a distinct genus. As stated before, beside the columellar fold, other diagnostic features of Itaborahia are the sharply acuminated spire apex with a concave outline and the prosocline aperture.

Figures

FIGURES 43-50: 43-47. Itaborahia lamegoi (DGM 5001-I); shell length 30 mm. 43-45. Overview. 46. Imperforated umbilicus. 47. Smooth protoconch. 69-70. I. lamegoi (AMNH 24240; holotype); shell length 31.5 mm. 50. ”Bulimulus sommeri” (DGM 5411-I; holotype); shell length 20.5 mm.