Hendricks—Miocene Conidae from the Gatun Formation of Panama


sigmoidal profile. Shoulder carinate to angulate; smooth. Widest part of shell at or just below shoulder. Aperture uniform in width from base to shoulder. Siphonal notch absent. Spiral grooves present on anterior third to half of last whorl, with cords between; axial growth lines sometimes evident in grooves. Spire whorls.—Spire moderate to high (RSH 0.20–0.24;


x=0:22; N=4); outline slightly concave. Protoconch multi- spiral. First several postnuclear whorls tuberculate. Early whorls strongly stepped; later whorls weakly stepped. Sutural ramp typically concave; sometimes flat or sigmoidal. Spiral orna- mentation on ramp is variable: several strong spiral threads are present on ANSP 1688, while these are reduced to fine spiral threads on USNM 645749 and USNM 645750; on UF 259873, a single spiral cord and one to two fine spiral grooves are pre- sent. Subsutural flexure asymmetrical (ASSF 0.6–0.8, x=0:7, N=3), depth approximately equal to width (DWSSF 0.9–1.1, x=1:0, N=3) (Fig. 3.2). Coloration pattern.—The coloration pattern of this species


is characterized from a single specimen, UF 259873 (Fig. 3.12– 3.14). It is not possible to determine if only a single pattern is present, or if there are two noninteracting patterns. The stronger component of the pattern consists of three well-defined, discontinuous spiral bands that result in irregularly shaped blotches. The weaker component consists of spiral rows of irregularly spaced dots and dashes between these bands. The two components do not differ in the color of emitted light under exposure to UV, nor does one component appear to overlay the other. Sutural ramp with irregular blotches.


Materials.—ANSP 1688 (lectotype of Conus imitator Brown and Pilsbry, 1911; Fig. 3.1–3.3); ANSP 78910 (paralectotype of C. imitator); NHMW 1933/0018/0225 (lectotype, Fig. 3.4, and two paralectotypes, one of which is shown in Fig. 3.5, of Conus dalli Toula, 1911); NHMW 1933/0018/0226 (two paralectotypes of C. dalli Toula; Fig. 3.6, 3.7); USNM 645749 (one specimen, figured by Woodring, 1970; Fig. 3.8); USNM 645750 (one specimen, figured by Woodring, 1970; Fig. 3.9, 3.10); UF 259770 (one specimen; Fig. 3.11); and UF 259873 (one specimen; Fig. 3.12–3.14).


Remarks.—Toula’s (1911) name for this species, Conus dalli,is occupied by the extant eastern Pacific species Conus dalli Stearns, 1873. The type material for this species resides at the


NHMWand is represented by five specimens, four of which are figured here (Fig. 3.4–3.7), including the lectotype designated by Woodring (1970, p. 355), NHMW 1933/0018/0225-1 (Fig. 3.4). These correspond closely with the lectotype of Conus imitator Brown and Pilsbry, 1911 (ANSP 1688; Fig. 3.1–3.3), as do the two specimens figured by Woodring (1970; Fig. 3.8–3.10). Additional work is needed to determine if Maury’s (1917) specimen (PRI 28624) from the Dominican Republic is Conasprella imitator. Woodring (1970) synony- mized his subspecies Conus imitator lius Woodring, 1928 from the Bowden Formation of Jamaica as C. imitator imitator based on the Jamaican specimens apparently lacking tubercles on the early postnuclear whorls, a trait that Woodring (1970) con- sidered variable in the species based on his material from the Gatun Formation: he reported that some lower Gatun Formation specimens lack tubercles on the early postnuclear whorls, while


811


other specimens of similar age possess the feature. The presence or absence of tubercles on early postnuclear whorls is not known to be an intraspecifically variable feature of cone snail shells, so additional work is needed to determine whether the early whorls of the Jamaican and lower Gatun Formation specimens in question are eroded or not. In any case, Woodring’s decision to synonymize his earlier Jamaican subspecies is tentatively followed here pending future study. The coloration pattern of Conasprella imitator revealed


under UV light, in addition to other aspects of its shell morphology, support a close relationship with the extant eastern Pacific species Conasprella (Kohniconus) arcuata (Broderip and Sowerby I, 1829), an association also recognized by Woodring (1966), and the extant western Atlantic species Conasprella delessertii (Récluz, 1843). Given their similar shells and radular tooth morphologies, Tucker and Tenorio (2009) assigned both extant taxa to their new genus Kohnico- nus. More recent molecular phylogenetic work (Puillandre et al., 2014, 2015), however, suggests that while they both belong to the clade Conasprella sensu Puillandre et al. (2014, 2015), they are otherwise not closely related; other species assigned to Kohniconus by Tucker and Tenorio (2009) were not included in the molecular phylogenetic analysis of Puillandre et al. (2014). Thus, additional work will need to be done to test the degree of relationship between C. arcuata and C. delessertii, as well as other similar species. In any case, C. imitator shares much in common with both extant species and can be confidently assigned to the genus Conasprella sensu Puillandre et al. (2014, 2015), if not the subgenus Kohniconus sensu Puillandre et al. (2014, 2015). In terms of coloration pattern, C. imitator shares more in common with C. arcuata, which has only one layer of pigmentation; C. delessertii has two interacting layers of pigmentation. Tucker and Tenorio (2009) assigned C. imitator to the genus Gradiconus (genus Conus, subgenus Dauciconus sensu Puillandre et al., 2014, 2015), but for the reasons stated above, an assignment to Conasprella is better supported. Among co-occurring fossil species, C. imitator might be confused with a species that is assigned here to the subgenus Dauciconus: Conus taphrus Woodring, 1970. Both species have somewhat similar overall shell shapes, but their coloration patterns are very different (see remarks under Conus taphrus for additional discussion). Even though Brown and Pilsbry (1911, p. 342) reported


Conasprella imitator as “rather abundant at Gatun,” only one specimen (UF 259873) is confirmed from UF locality YN020. Brown and Pilsbry’s (1911) specimens, which were collected from exposures associated with the construction of the locks at Gatun, are from the middle Gatun Formation, while the two records from YN020 (UF 259873, UF 271035) are from the lower Gatun Formation. Woodring (1970, p. 355) reported C. imitator as spanning the lower (six localities) to middle (six localities) to upper (10 localities) Gatun Formation. Of the 70 specimens available to him, the greatest abundance of C. imitator (20 specimens) came from his locality 177b, which is positioned in the upper Gatun Formation. At the very least, these reports suggest that, owing to differences in paleoenvir- onment and/or geological age, C. imitator may have been less common in the lower Gatun Formation relative to the upper Gatun Formation.


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