Brazilian species of Gadila (Mollusca: Scaphopoda: Gadilidae): rediscovery of Gadila elongata comb. nov. and shell morphometrics

Abstract

Gadila elongata comb. nov. was described in 1920 from the northern Gulf of Mexico. Until recently, it was only known from the type locality. Herein we present the first record of G. elongata from Brazil (Northeast coast, Ceará state, collected at 177 m) and a morphometrics analysis of the Brazilian species of Gadila. A multivariate Discriminant Function Analysis, based on nine shell morphometric variables (length, maximum diameter, length to maximum diameter ratio, distance of point of maximum diameter from anterior aperture, maximum curvature, anterior aperture height to anterior aperture width ratio, apical aperture height, apical aperture width and apical aperture height to apical aperture width ratio) enabled the distinction between all species studied. Comparisons of shell morphometrics show that length and length to maximum diameter ratio are the most important variables in the differentiation of Gadila species

A revision of the genus Olivancillaria (Mollusca: Olividae) from the southwestern Atlantic

“…Geometric morphometric methods applied to this problem are a good tool to reduce these difficulties. Armbruster (1995) reported an effective separation among four species of the genus Cochlicopa Férussac, 1821 (Pulmonata: Cochlicopidae) based on a canonical discriminant analysis and Caetano et al (2010) differentiated four species of the genus Gadila Gray, 1847 by the same technique. Conde-Padín et al (2007) demonstrated through a discriminant analysis that geometric morphometric methods are very efficient for diagnosing differences among sympatric populations of the genus Littorina.…”

Morphometry of the shell in Scaphopoda (Mollusca): a tool for the discrimination of taxa

“…The material examined was selected in an attempt to do a broad taxonomic sampling and based on the availability for study in the collections studied. The shells measured are related to previous taxonomic studies of scaphopods from Brazil (Absalão et al ., 2005; Caetano & Absalão, 2005; Caetano et al ., 2006, 2010; Scarabino & Caetano, 2008; Caetano & Santos, 2010; Scarabino et al ., 2011; Souza & Caetano, 2013), which is reflected in the geographic account of the dataset. The identifications of the specimens were based on the shell morphology with comparisons to the type material, based on original descriptions and illustrations.…”

“…For the congeneric analysis of Gadila , see Caetano et al . (2010); the data published by the latter authors were included here at other levels (i.e. genera, families).…”

“…Morphometric variables were taken according to Caetano et al . (2010) (Figure 1). The variables measured are total length (L), maximum diameter (Max), the distance of the point of maximum diameter from anterior aperture (Dmax), maximum curvature (Arc), the distance of the point of maximum curvature from the apex (Larc), anterior aperture height (Ha), anterior aperture width (Wa), apical aperture height (Hp), apical aperture width (Wp) (Figure 1).…”

“…The use of this approach applied to the class Scaphopoda has increased since Shimek (1989) proposed the first indices based on measurements of the shell accompanied by statistical evaluation. Recent studies used the same or similar indices as a tool for the discrimination of scaphopod species, focusing on the comparisons of congeneric species of Gadilidae (Absalão et al ., 2005; Caetano & Absalão, 2005; Scarabino & Caetano, 2008; Caetano et al ., 2010; Scarabino et al ., 2011). Groups of Dentaliida have rarely been studied using this combined approach, despite successful results within Fissidentalium P. Fischer, 1885 (Shimek & Moreno, 1996; Shimek, 1997).…”