Terebralia Swainson, 1840

Thivaiou, Danae, Harzhauser, Mathias & Koskeridou, Efterpi, 2023, Cenozoic diversity and distribution of the mangrove- and mudflat-associated gastropod genus Terebralia Swainson, 1840 (Potamididae: Caenogastropoda) in Europe, Comptes Rendus Palevol 22 (14), pp. 245-264 : 247-248

Genus Terebralia Swainson, 1840

Terebralia Swainson, 1840: 315 .

REMARKS

Species of the genus present shells of medium size, ranging from c. 20 to c. 100 mm, with high-spired turreted or bulky shapes with flat to moderately convex teleoconch whorls. The protoconch is rarely preserved even for recent species ( Houbrick 1991), although a direct development is described for the veligers of the type species, T. palustris (Linnaeus, 1767) , and for T. sulcata (Born, 1778) ( Houbrick 1991) . Harzhauser & Kowalke (2001) noted that T. palustris has a very bulbous embryonic shell of 0.75 whorls, measuring 170-180 µm in diameter. This suggests a very short planktotrophic stage, which appears to have remained undetected by Houbrick (1991). The protoconch of T. lignitarum shows a clear demarcation between the embryonic and larval shell and a sinusigera notch, which suggests a planktonic veliger stage ( Harzhauser & Kowalke 2001). Furthermore, the larval shell bears two strong spiral keels on the lower part of the whorls ( Harzhauser & Kowalke 2001). Teleoconch sculpture comprises several broad spiral cords separated by narrow interspaces and densely spaced axial ribs; prominent beads typically form at the intersections of spiral cords and axial ribs; in a few species beads may grade into short spines in the adapical half of whorls. The last whorl is often somewhat inflated with a convex base. The aperture is ovate, the outer lip expanding, moderately to strongly thickened, forming a continuous peristome in some species, or in others it can be interrupted by a moderately deep anterior canal. The inner lip is thin to moderately thickened, rarely expanding on the base. Columella morphology is straight to slightly concave, with a columellar fold. Distinct varices on which axial sculpture is usually weak, coincide with axial rows of internal denticles, which are not developed on the internal surface of the outer lip (for descriptions see Houbrick 1991; Healy & Wells 1998; Vermeij 2007, 2014; Reid et al. 2008; for anatomical data see Houbrick 1991). According to Vermeij (2007) the siphonal canal is tubular and closed for Terebralia sulcata . This feature – associated with olfactory organs that detect chemical signals from a distance in recent species – appeared during the Early Miocene and has been lost for the recent Terebralia palustris ( Vermeij 2007) .

A B

The genus is not speciose ( Houbrick 1991; Reid et al. 2008). MolluscaBase (2020) lists only three extant species, all of which are restricted to the IWP. Similarly, the fossil record of the genus suggests that Terebralia has never been rich in species. However, the morphological variability of fossil Terebralia species ( Sälgeback & Savazzi 2006) has led to the description of numerous subspecies and varieties (e.g. Sacco 1888), which have hampered biogeographical and stratigraphic analyses. The same problem arose for recent species, especially during the 19th century, but was overcome during the last decades by revisions and improved knowledge ( Houbrick 1991; Bandel 2006; Reid et al. 2008).

SYNOPSIS OF EUROPEAN TeRebRaLia SPECIES

This list gives an overview of species-level taxa in alphabetical order.