Strobilops aeneus

Strobilops (Strobilops) aeneus Pilsbry, 1926
Bronze Pinecone

  • Strobilops aenea [sic] Pilsbry 1926: 69.
  • Strobilops aenea [sic] f. micromphala Pilsbry 1927 (1927–1935): 30.
  • Strobilops aenea [sic] f. spiralis Pilsbry 1927 (1927–1935): 31.
Strobilops aeneus; Morris Island Conservation Area, Ottawa, Ontario
Strobilops aeneus; Morris Island Conservation Area, Ottawa, Ontario; diameter 2.9 mm (NBM 009023).

Identification. Shell conical. Whorls ca 5½. Spire whorls not very convex. Suture shallow. Periphery somewhat more angular than the other Strobilops species. Protoconch smooth. Teleoconch with strong, curved colabral riblets, mostly absent on base; weak growth lines on base. Aperture subovate. Spiral lamellae, mostly internal in last whorl: 1 large and 2 smaller parietal lamellae; 3 or 4 basal lamellae; no palatal lamellae. Lip in adults thickened, expanded. Umbilicus small, ca ⅕ of shell width. Shell translucent, reddish brown; lip opaque, pale pinkish brown. Width to 2.9 mm (higher than wide).

Animal pale grey, with sides paler.

This species is more depressed than any other Canadian Strobilops, and with a more conical, nearly straight-sided spire. There are 3 or 4 basal folds and no folds above the periphery. The periphery is decidedly angular, and the base is flattened with the aperture not so deeply rounded. The colabral ribs are narrower and slightly sharper, the umbilicus slightly wider, and the colour darker.

Habitat. Rich, deciduous old-growth woods with deep litter layer. In leaf litter and on dead wood. Sympatric with S. labyrinthicus.

Global range. Ontario and Iowa, south to along the Atlantic coastal plain to Florida, Louisiana, and western Texas (Hubricht 1985); Mexico (?—see Remarks).

Canadian range. Southern Ontario, east to the Ottawa region. Rare.

Its occurrence in Nova Scotia (MacMillan 1954) is based on a misidentification (Forsyth & Oldham 2014). This species has been reported by Lauriol et al. (2003) from infill material retrieved from a cave in Gatineau Park, Quebec, but their identification could not be verified; its occurrence in Quebec seems plausible but remains unconfirmed.

Etymology. Latin, aeneus, “bronze-coloured”.

Remarks. This species was confused with the Mexican Strobilops strebeli (L. Pfeiffer, 1862) for several decades before Pilsbry (1926) provided it with a name. A year later, he described three infraspecific taxa (Pilsbry 1927 in 1927–1935). Of these, Hubricht (1985) considered one of these taxa, Strobilops aenea spiralis Pilsbry, 1927, to be a synonym of S. texasianus Pilsbry & Ferriss, 1906, and Pilsbry’s figures of spiralis do show it to have a spire with more strongly convex sides than in S. aeneus and more similar to S. texasianus. The second taxon, Strobilops aenea form micromphala, was described as a southwestern (lower Mississippi) race having a slightly smaller umbilicus than typical aeneus, among other characters, but Pilsbry (1948) later identified material from Washington, DC, Pennsylvania, and Illinois, which suggests that it is mixed in with typical S. aeneus over a greater part of its geographic range. A subspecies, Strobilops aeneus mexicanus Pilsbry, 1903 occurs in north-eastern and eastern Mexico (Pilsbry 1927 in 1927–1935, Correa-Sandoval et al. 2007). Pilsbry (1927 in 1927–1935: 33) wrote: “I have separated it from S. aenea [sic] with some doubt, as the difference is slight, but the umbilicus in aenea seems always to be a little smaller, the color of fresh shells is different, and adult individuals of aenea from the United States generally have four basal folds.” It is unknown if this presumed subspecies is disjunct from the main range, and there has been no recent discussion on the validity or formal synonymization of this or the other infraspecific taxa.

The masculine gender of Strobilops mandates that the species name should be spelled aeneus, not the feminine aenea.