Australdonta teaae, Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2013

Sartori, André F., Gargominy, Olivier & Fontaine, Benoît, 2013, Anthropogenic extinction of Pacific land snails: A case study of Rurutu, French Polynesia, with description of eight new species of endodontids (Pulmonata), Zootaxa 3640 (3), pp. 343-372 : 361-362

Australdonta teaae sp. nov.

Figures 10 A, 11, 14E, 15E

Examined material (23 specimens). Holotype: MNHN 25205, Rr8. Paratypes: MNHN 25206, 8 shells, Rr8. Additional material: 3 shells, Rr8; 4 shells, Rr3; 3 shells, Rr4; 1 shell, Rr5; 1 shell, Rr46b; 2 shells, Rr61.

Diagnosis: Shell very large, much wider than high, with a long and narrow peripheral rostrum, devoid of a supraperipheral keel or groove.

Description: Shell discoidal, white, with reddish-brown flammulations on the apical surface, often faintly visible peripherally on the shell base through the subpellucid shell wall. Shell thin, opaque to subpellucid; periostracum adherent, matt. Apex and spire flat to moderately raised; later whorls descending more rapidly. Apical suture adpressed at apex, progressively deepening in subsequent whorls; umbilical suture impressed. Whorls strongly keeled peripherally, slightly to moderately concave in the vicinity of the keel, convex towards the shell axis. Transition between protoconch and teleoconch indistinct. Protoconch ornamented by fine spiral and axial lirae, forming a reticulated pattern. Spiral lirae persisting on the teleoconch. Axial lirae gradually transitioning into broader, very low ribs, with interspaces two to four times their width, comprising the primary axial sculpture of the teleoconch; secondary sculpture of the teleoconch formed by very fine, crowded axial riblets, with interspaces approximately equal to their width, overlaying the primary sculpture, and forming tiny nodules at intersections with spiral lirae. Umbilicus wide, shallow to moderately deep. Peristome elongated crescent, with rostrate periphery. Palatal wall with five shallowly recessed barriers, extending approximately one-eighth whorl, with gradual anterior and abrupt posterior descension; barriers one to four basal in position, regularly spaced, either similar in prominence or with the first barrier slightly lower than the remainder; barrier five supraperipheral, usually similar in prominence to the basal barriers, seldom trace-like. Parietal barriers three in number, regularly spaced, not recessed within aperture, with gradual anterior and abrupt posterior descension, extending approximately one-quarter whorl, decreasing in prominence slightly to markedly from the first to the third barrier. Other shell features that can be expressed numerically are shown in Table 2 .

Remarks: A. teaae displays great variability in spire elevation, umbilicus depth and angle of the peripheral rostrum. Isolated specimens may appear separable ( Fig. 11 E,F), but individuals exhibiting intermediate conditions suggest that only one species is involved. Specimens with a high spire ( Fig. 11 E) approach A. collicella Zimmermann et al., 2009 in general shell shape. However, A. teaae may be readily distinguished from that species by its much longer peripheral rostrum and by the position of the apical suture, which adjoins the infraperipheral wall of the previous whorl in A. teaae , rather than connecting peripherally as in A. collicella . More typical specimens of A. teaae exhibit a low to very low spire ( Figs 10 A, 11F) and may superficially resemble A. magnasulcatissima , which shares a long peripheral rostrum and a similar arrangement of apertural barriers. However, the heavy sculpture, much wider umbilicus and the supraperipheral keel and groove of A. magnasulcatissima are unparalleled by A. teaae and provide easy and reliable criteria to distinguish these species. Recovered specimens of A. teaae were considerably worn, and many had large portions of the shell broken or missing; on average, shells of this species are more deteriorated than those of most other taxa described herein.

Etymology: This species is dedicated to Priscille Tea Frogier, head of the Délégation à la Recherche in Tahiti, in recognition for her involvement in this project and in the preservation of the “fenua”.

Figures

FIGURE 10. Holotypes of: A. Australdonta teaae sp. nov.; B. Minidonta boucheti sp. nov.; C. M. bieleri sp. nov. Scale bars = 1 mm.

FIGURE 11. Australdonta teaae sp. nov. A. Holotype (MNHN 25205), apical view; B and C. Paratype 6 (MNHN 25206); B. Sculpture of the protoconch and early teleoconch; C. Sculpture of the late teleoconch; D. Paratype 2 (MNHN 25206), detail of the peristome; E. Paratype 1 (MNHN 25206), displaying a moderately raised spire; F. Paratype 2, displaying a flat spire. Scale bars: A = 1 mm; B – D = 400 µm; E – F = 2 mm.