Hendricks—Miocene Conidae from the Gatun Formation of Panama


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Figure 1. A fossil specimen (UF 271043) of Conus spurius Gmelin from the Gatun Formation of Panama shown under (1) regular light, (2), ultraviolet light, and (3) as a inverse UV image, causing the brightly fluorescing regions in (2) to become darkened, as they would have appeared in life. Scale=1 cm.


(Hendricks, 2015), and the Plio-Pleistocene of the southeastern United States (Hendricks, 2009; Petuch et al., 2015). An exception is the cone snail fauna of the late Miocene Gatun Formation of Panama, which was last intensively studied by Woodring (1970) (supplemental information about the fauna was later provided by Pitt and Pitt [1993]). This richly fossili- ferous, siliciclastic unit, which is exposed on the Caribbean coast of Panama in the province of Colón, has attracted the attention of paleontologists for over a century (e.g., Toula, 1909, 1911; Brown and Pilsbry, 1911; Cossmann, 1913; Vaughan, 1919; Olsson, 1922; Woodring, 1957, 1959, 1964, 1970, 1973, 1982; Hendy, 2013; Pimiento et al., 2013; Anderson et al., 2017). Nearly 400 species of mollusks have been reported from the Gatun Formation (Paleobiology Database, accessed July 12, 2016) and modern work on the fauna continues to reveal additional diversity (e.g., Landau et al., 2012). As noted by Pimiento et al. (2013), exposures of the Gatun Formation tend to depend upon recent construction activity because urban devel- opment and fast-growing vegetation cause many collecting localities to be short lived. Building on earlier work by Coates (1999), Hendy (2013)


provided a detailed overview of the stratigraphy and paleoen- vironmental context of the Gatun Formation (also see Pimiento et al., 2013; Anderson et al., 2017). The total thickness of the Gatun Formation, which is divided into a lower, middle, and upper unit (see Woodring, 1957), is likely >600m and accumulated over a four-million-year interval between ca. 12–8 Ma (Hendy, 2013). Based on quantitative paleoecological analyses of molluscan assemblages, Hendy (2013, p. 223) found that “different parts of the formation accumulated in a range of depositional environments, despite only subtle variations in their sedimentology” and that these marine environments ranged in depth from 0–100m. This contrasts somewhat with earlier estimates that suggested that theGatun Formationwas not formed in depths exceeding ~50m; for example, Collins (1999) used benthic foraminifera to estimate that the lower, middle, and upper Gatun Formation were each deposited at a depth of ~25m. Twenty-five species-group names (species and subspecies,


including conferred records) have been applied to fossil Conidae from the Gatun Formation of the Panama Canal Zone (Table 1). Toula (1909) published the first report of a cone snail fossil from the Gatun Formation (not identified to species); this


was followed two years later by his descriptions of three taxa (Toula, 1911). Cossmann (1913) reported four species from the Gatun Formation, one of which was described as new. Brown and Pilsbry (1911) described five new species from the Gatun Formation and reported the occurrence of four additional taxa that were originally described from elsewhere. Olsson (1922) focused on the Neogene molluscan fauna of Costa Rica, reporting that several cone snail species co-occurred in the Gatun Formation of the Canal Zone, including one newly described species. Woodring (1970) provided the most thorough systematic treatment of Conidae from the Gatun For- mation and included detailed taxonomic summaries of the work described above. Further, Woodring (1970) described two additional cone snail species from the Gatun Formation and reported on taxa found in the Gatun Formation that were originally described from other tropical American Neogene localities. His work on the cone snails from the Gatun Formation was based on ~350 specimens from existing collections at the Smithsonian Institution and material that he collected himself in 1947 (Woodring, 1957, p. 46). He recognized 16 species and subspecies of Conidae from the Gatun Formation: “eight in the lower part, 14 in the middle part, seven in the upper part in the eastern area, and six in the upper part in the western area” (Woodring, 1970, p. 346).Woodring (1970) further noted that two of the 54 localities he studied had a maximum of eight co-occurring species; one of these localities (Woodring’s locality 138c) is from the lower Gatun Formation, while the other (Woodring’s locality 155) is from the middle Gatun Formation. Amaximum of five co-occurring species was reported from a locality positioned in the upper Gatun Formation (Woodring’s locality 175). Pitt and Pitt (1993) published the most recent work on fossil Conidae from the Gatun Formation; these authors illustrated three specimens that they could not confidently assign to known taxa, but otherwise did not add to the total diversity of Conidae from the Gatun Formation. In contrast to Woodring’s (1970) broad treatment, the focus


of this paper is characterization of the diversity of fossil Conidae from a single well-studied locality positioned in the lower Gatun Formation. Cone snail specimens were intensively sampled from this locality in July and October 2015 by the author and others, which resulted in the collection of nearly 900 specimens belonging to at least nine species, allowing intraspecific varia- bility to be characterized for many of these taxa. Special atten- tion is given to description of the preserved coloration patterns of many of the species, which are often revealed by exposure to ultraviolet (UV) light (see Fig. 1), an approach that Hendricks (2015) recently discussed and applied to fossil Conidae from the Dominican Republic. This technique, pioneered by Olsson (1967), has been previously applied to other molluscan fossils (e.g., Vokes and Vokes, 1968; Krueger, 1974; Hoerle, 1976; Kase et al., 2008; Hendricks, 2009; Caze et al., 2010, 2011a, b; Landau et al., 2013; Harzhauser and Landau, 2016), including by Pitt and Pitt (1993) who were the first to publish photographs of Conidae (as well as other taxa) from the Gatun Formation under UV light. This paper builds upon the work of Pitt and Pitt (1993) by fully characterizing the variability in coloration pat- terns in cone snail fossils from the Gatun Formation, including those of taxa that they did not study. These preserved coloration patterns are of special interest because they—in conjunction


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