Paleoecology of gastropods preserved in turbiditic slope deposits from the Upper Pliocene of Ecuador

Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 141±163

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Paleoecology of gastropods preserved in turbiditic slope deposits from the Upper Pliocene of Ecuador S.E. Walker* Department of Geology, University of Georgia, Athens, GA 30602, USA

Abstract Upper Pliocene gastropods preserved in turbiditic deposits from the Upper Onzole Formation of northwestern Ecuador provide an excellent window into the past for understanding paleoecological dynamics in deep-water habitats, such as shells used as substrata by epi- and endobionts (encrusters and bioeroders), shell use by hermit crabs, and predation (shell repair and drilling) just prior to the closing of the Isthmus of Panama. Previously, paleoecological and taphonomic information was lacking for deep-water (mid-to-outer shelf) and bathyal fossil gastropods in contrast to shallow-water habitats that have been relatively well studied. This study showed that while epibionts were relatively rare on the fossil shells because of curatorial bias, endobionts (bioeroders) occurred on 51% of the 59 species examined. Of the bioeroders, the trace fossil Helicotaphrichnus commensalis was found on 27% of the species. The presence of Helicotaphrichnus indicates that hermit crabs were also a part of the deep-water assemblage prior to burial by the turbidity ¯ow although there are no body fossils of hermit crabs yet reported from this area. Using epi- and endobiont criteria preserved on the shells, the hermit crabs appeared to prefer shells that had large last whorl volumes. Recycling and retention of Upper Pliocene shells by Recent hermit crabs (biological remanieÂ) on the coast of Ecuador also occurs, which could lead to potential temporal anomalies in the fossil record. In addition, the trace fossil Helicotaphrichnus is now reported for the ®rst time from the Upper Pliocene of Ecuador. This trace fossil also occurred on bathyal shells, suggesting that its bathymetric range may be much deeper than previously reported. Records of predation retained on the deep-water fossils were common (66% of the species had shell repair; 68% of the species had drilled shells) and represented a variety of molluscivorous predators. The durophagous predators (e.g. crabs) and drilling predators (naticids, octopods, and muricids) appeared to be selective in their choice of prey items. High-spired gastropods (especially of the family Turridae) were statistically more likely to be affected by predators than all other prey species and groups examined. Shell architecture for other shell types examined, however, did not appear to affect the frequency of shell repair occurrence. Although predation is thought to be a generalist activity in deep-water environments, it may be that in certain areas, specialist predators may be more common than previously considered. Thus, fossil deep-water communities may contain a rich legacy of paleoecological interactions that can then be used for evolutionary ecological questions pertaining to selective predation with depth, variation in encrusters and bioeroders with depth, and to compare differences in paleoecological structure of these molluscan communities before and after the closure of the Isthmus of Panama. q 2001 Elsevier Science Ltd All rights reserved. Keywords: deep-water molluscs; epi- and endobionts; bioeroders; shell repair; drilling predation

1. Introduction

* Fax: 11-706-542-2425. E-mail address: [email protected] (S.E. Walker).

Deep-water (mid-to-outer shelf and bathyal) molluscs have an excellent fossil record but little is known about their paleoecology or taphonomy. For

0031-0182/01/$ - see front matter q 2001 Elsevier Science Ltd All rights reserved. PII: S 0031-018 2(00)00206-6

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Fig. 1. Localities (black dots on map) for the Upper Pliocene fossils in northwestern Ecuador. Map modi®ed from Miller and Vokes.

example, well-preserved outer shelf to bathyal molluscs are reported from the Paci®c Rim region but these studies are chie¯y taxonomic in nature (Itoigawa, 1958; Olsson, 1964; Hickman, 1972, 1976; Noda and Kikuchi, 1980; Vokes, 1988). Hickman (1984), however, examined both the taxonomic and ecological structure of deep-water molluscan communities from the northeastern Paci®c. She documented six distinctive deep-water molluscan associations that were important for age determination and correlation of deep-water facies. Additionally, she showed that the Cenozoic fossil molluscan communities were diverse taxonomically and ecologically. Despite the recent and exciting ®ndings in ecological research from the deep-sea (bathyal and deeper) and deep-water (mid-to-outer shelf) habitats (Callender and Powell, 1992; Grassle and Maciolek, 1992; Callender et al., 1994; Parsons et al., 1997; Walker et al., 1998), the paleoecological study of deep-water molluscs has not progressed since Hickman's seminal work (Walker and Voight, 1994). It is known that Recent deep-water gastropods have epi- and endobionts, shell repair, and drill holes on their shells (e.g. Sander and Lalli, 1982; Vale and Rex, 1988, 1989; Kropp, 1992; Walker and Voight, 1994; Voight and Walker, 1995). However, it is not known if these paleoecological (and taphonomic) signatures are present in the fossil record of deep-water molluscs. This project was undertaken to determine the type and amount of paleoecological information (i.e. epiand endobionts, shell repair, and drilling predation)

that occur on mid-to-outer shelf and bathyal gastropods preserved in turbiditic deposits from the Upper Pliocene of Ecuador. The term deep-water is used in this paper to denote the mid-to-outer shelf and bathyal species. Use of the Upper Pliocene shells of Dalium by Recent hermit crabs at the Punta Gorda site is also discussed as biological remanieÂ. 2. Methods 2.1. Locality A total of 795 gastropods representing 59 species were examined from the museum collections of Emily and Harold Vokes in addition to a sample of Dalium ecuadorium collected by the author from Punta Gorda, Ecuador (Fig. 1). At Punta Gorda, shells were encapsulated within thick mudstone turbidites which were deposited on the inner trench-slope of the continental margin (see Aalto and Miller, 1999, Fig. 11B). The Vokes sample came from Quebrada Camarones, Ecuador, Tulane locality Tu-1397, which is described as follows (Vokes, 1988): Esmeraldas Beds, Quebrada Camarones, cutbank on east side of canyon, which is at east edge of village of Camarones, 20 km (by road) east of bridge over Rio Esmeraldas at Esmeraldas or approximately 10 km east of mouth of Rio Esmeraldas, Province of Esmeraldas, Ecuador.

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Locality Tu-1397 is thought to represent a collection of molluscs representing water depths greater than 73 m (Vokes, 1988, p. 8). The basis for this depth determination is the limited representation of Oliva (primarily a shallow-water species) and the relative abundance of Cantharus scissus which has a living relative (Cantharus panamicus) that has a depth distribution of up to 73 m (Vokes, 1988). The majority of the 59 species examined for this paper, based on comparisons with modern species and depth information provided by Olsson (1964) and Keen (1971), are considered to be mid-to-outer shelf species with three species representing bathyal depths (e.g. Natica scethra, Calliotectum ®sheri, and Dalium ecuadorium) (Appendix A). The fossil species which have Recent equivalents that represent mid-to-outer shelf depths off the coast of Ecuador are: Phos (Metaphos) spp. (37±232 m), Amaea (Scalia) ferminiana (44±277 m), Cirsotrema togatum (32±113 m), and Cochlespira cedonulli (55±275 m) (Appendix A). The Turridae family of gastropods are especially characteristic of deep-water environments, including bathyal habitats (Hickman, 1984). Tu-1397 has a relatively large fraction of turrids (especially Polystira spp., Appendix A). The associated foraminiferal assemblage, composed of benthic and planktonic forms, represent inner to outer shelf and upper slope paleo-depths (Haman and Kohl, 1986). Laurel S. Collins (Florida International University) is re-examining the depth determinations for foraminifera from the Esmeraldas beds and will provide more conclusive information in the near future (refer to Panama Paleontology Project, www.®u.edu/~collinsl). Therefore, until further information is available, the Tu-1397 locality is considered to be a mixed association of deep-water mollusc species, primarily representing mid-to-outer shelf depths with a limited component of bathyal species. The age of the Esmeraldas beds, as a whole, are considered to be 3.6±3.2 Ma (Hansson and Fischer, 1986; Miller and Vokes, 1998), which puts these beds coincident with the closure of the Isthmus of Panama (about 3.1±2.8 Ma, Coates and Obando, 1998). The Esmeraldas beds form the top part of the Upper Onzole Formation, which is thought to represent a deepening upward depositional cycle of Late Neogene age (Evans and Whittaker, 1982; Whittaker, 1988). The molluscs of these beds were deposited within

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the Bolivar Trough (Arato Strait), which was the longest lasting and probably largest sea way between the Caribbean and the eastern Paci®c prior to the closure of the Isthmus (Vokes, 1988). Thus, the molluscan fauna should be expected to be nearly identical to the Caribbean fauna, but in fact, the molluscs within the Esmeraldas beds are chie¯y representative of the Panamic Province (Vokes, 1988). 2.2. Paleoecological analysis All specimens were measured for shell height with digital calipers and examined under a dissecting microscope for the presence of epi- and endobionts (e.g. encrusting bryozoa, encrusting foraminifera, boring bryozoa, boring barnacles, boring spionid polychaetes). Major shell repair and drill holes from muricid, naticid or octopod predators were also noted for each shell. Major shell repair, resulting from predatory peeling or chipping of the shell, is expressed as a jagged repair scar that usually disrupts the growth or ornamentation of the shell (Raffaelli, 1978; Robba and Ostinelli, 1975; Vermeij et al., 1981). Shell repair is indicative of unsuccessful predation by crabs (e.g. Papp et al., 1947; Robba and Ostinelli, 1975; Vermeij, 1978, 1982) or perhaps other durophagous predators. Shell repair is not directly correlated with intensity of predation or predation rates (Schoener, 1979; Schindel et al., 1982). Rather, repaired scars are important for inferring that predation may have occurred in deep-water habitats or the fossil record where direct observation of predation is not possible (Robba and Ostinelli, 1975; Vermeij et al., 1981; Vale and Rex, 1988, 1989). Frequency of major shell repair was determined by the number of individuals that had at least one shell repair divided by the total number of individuals in the sample, a method that is now used by most researchers (see CadeÂe et al., 1997, pp. 69±70). Frequency of multiple repair scars was calculated in the same way. Drill holes that were circular and countersunk in appearance were attributed to naticid gastropod predators. If the holes were circular to subcircular and cylindrical with straight-sided walls, they were attributed to muricid gastropod predators; octopods if the drill hole was small (0.1±2.0 mm) and cylindrical to subcylindric in shape (after Kabat, 1990;

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Kowalewski, 1993). It was often dif®cult to distinguish between octopod and muricid drillings; drillings that could not be assigned to any drilling predator were considered as ªunknownsº. Although capulids were present within the Esmeraldas beds, no capulid drillings or attachment scars were observed on the shells. Frequency of drilling predation (drilling ªpresentº) was determined by the number of shells that had at least one complete drill hole per shell, divided by the number of shells examined in the assemblage. Three locations on the shell were also examined for the presence of drill holes: the apex, the last whorl and the other whorls (whorls located between the apex whorls and last whorl of the shell). Because epi- and endobionts were relatively rare on the shells, no statistical analyses were undertaken. For shell repair and drilling predation, however, samples sizes were adequate. One-way analyses of variance (ANOVAs) were performed at alpha-level 0.05 using the Systat 5.2.1 statistical package (Wilkinson et al., 1992). Least-squared-mean analyses from the ANOVA analyses were also reported. Tukey±Kramer tests (Wilkinson et al., 1992) were conducted to determine the signi®cance level among species. For shell repair, the null hypothesis tested was that there was no difference in shell repair for the most abundant species examined. An additional test examined if shell architecture was correlated with the frequency of shell repair. For drilled shells, the null hypothesis was that there was no difference in drilling occurrence among the most abundant species examined. If there was a signi®cant difference in drilling occurrence, then the predators may be selecting particular prey. 2.3. A note on the use of museum collections for paleoecological analysis An additional taphonomic bias exists at the museum level for shells. Usually only pristine examples of shells, cleaned of their epibionts, are housed in museums (Walker, 1989, p. 450; Lescinsky, 1996). Damaged specimens are usually discarded. Or, specimens heavily encrusted with epibionts are classi®ed with the biont, rather than the mollusc. However, even over-zealous shell cleaners may miss encrusting organisms that are preserved in taphonomic `refugia' (such as gastropod sutures and apertures) that protect

the encrusters from becoming dislodged (Walker and Carlton, 1995). Because museum collections may contain specimens from localities that are now destroyed, it is imperative to glean as much paleoecological information from these collections despite the potential for curation bias. In summary, the specimens examined here are biased against epibionts because in the washing process, encrusting organisms usually fall off (Vokes, personal communication, 1999). In contrast, endobiont trace fossils, shell repair, and drilling predation are well preserved on the shells and cannot be removed by the curatorial process.

3. Results and discussion 3.1. Epi- and endobionts on deep-water molluscs: an overview Shell-inhabiting epi- and endobionts are preserved in situ and have the longest fossil record of any invertebrate community (Alexander and Brett, 1990). Furthermore, epi- and endobionts are extremely important for paleoecological, paleoenvironmental and evolutionary analyses (Boucot, 1981, 1990). Few papers, however, document epi- and endobionts associated with deep-water molluscs (Walker and Voight, 1994; Voight and Walker, 1995). Gastropod shells are often the only hard substrate available for biont colonization in the soft-sediment of deep-water habitats (Walker and Voight, 1994; see also Abello et al., 1990, for deep-water crustaceans with epibionts). Indeed, modern deep-water gastropods do have epibionts that encrust their shells. For example, two Recent bathyal gastropods (Bathybembix and Gaza) had epi- and endobionts on half of the shells examined (Walker and Voight, 1994; Voight and Walker, 1995). However, the diversity of bionts was low and the preservation potential of the bionts differed among the two gastropod species examined. For example, Bathybembix had potentially preservable bionts (i.e. encrusting serpulid polychaetes, bryozoans and foraminiferans), while Gaza shells were encrusted with non-preservable chitinous epibionts (i.e. folliculinids and a bryozoan). Further, the occurrence of epibionts on Gaza shells was correlated with higher nutrient waters of river systems (Voight and Walker, 1995).

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Fig. 2. Frequency of endobionts (bored species) and epibionts (encrusting species) on the Upper Pliocene gastropod shells. Each shell with at least one biont is divided by the total number of shells examined to determine the biont frequency of occurrence.

Deep-water gastropod shells can also be inhabited by hermit crabs which have epibionts attached to the gastropod shells (e.g. Cairns and Barnard, 1984). Although the potential for using epi-and endobionts for paleoecological interpretations exists, it is not known if deep-water fossil molluscs from Cenozoic deposits have epi- and endobionts preserved on their shells. 3.2. Endobionts (bioeroders) on the fossil deep-water shells Half (51%) of the fossil gastropod species examined had bioeroders (Fig. 2, Bored spp.); of the total individuals, 18% had bioeroders. Spionid polychaete borings (i.e. Helicotaphrichnus and other spionid traces) and fungal/algal borings were the most common trace fossils present on the shells (Fig. 2). Boring barnacles (Zaphella) and clionid sponge borings (Entobia) were much less common (Fig. 2). The lack of sponge borings was surprising. Many more fossil gastropod species were expected to have clionid borings on the shell because ®eld experiments in the Caribbean have shown that clionids are common to a depth of 73 m on empty shells emplaced for two years (Walker et al., unpublished data). The lack of clionids on the Upper Pliocene shells could be

due to a number of ecologic and taphonomic factors. The most parsimonious explanation for the lack of clionids on the fossil shells may be that many of the gastropods were alive prior to burial as clionids rarely attack shells of living gastropods (Walker, 1998). Hermit crabs were also a component of this deepwater fossil assemblage, although their body fossils are missing. Based on the presence of speci®c types of trace fossils, one can infer the presence of hermit crabs (Walker, 1988, 1989, 1992). For example, boring barnacles within the aperture of the fossil shells may be indicative of hermit crab-inhabited shells (Fig. 3B; Seilacher, 1969; reviewed by Walker, 1992). Helicotaphrichnus commensalis, however, is the best trace fossil to determine the presence of hermit crabs in a fossil assemblage as it is uniquely associated with hermit crab-inhabited shells (Fig. 3A; Kern et al., 1974; Kern, 1979; Walker, 1992). In this study, Helicotaphrichnus commensalis, was present on 27% of the fossil gastropod species (Fig. 2). Sixteen gastropod species with an adequate sample size were then examined for the presence of Helicotaphrichnus among the individuals (Table 1). In those deep-water gastropod species, Helicotaphrichnus occurred on 10% of the individuals (Table 1). Helicotaphrichnus is reported from shelf waters from the Eocene of the Atlantic Gulf and Coastal

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Table 1 Gastropod shells that were once inhabited by hermit crabs from the Upper Pliocene of Ecuador. Number of individuals and frequency of occurrence (within parentheses) are reported for each species. ªOther hermit crab associatesº represent epi- and endobionts present within at least two of the following areas on the gastropod shell: the aperture notch, outer lip, columella or the siphonal canal Species and sample size

Helicotaphrichnus present

Other hermit crab associates

Total hermit crab inhabitation

Aforia ecuadoriana n ˆ 8 Cancellaria esmeralda n ˆ 5 Cantharus scissus n ˆ 31 Cantharus scrupeus n ˆ 13 Conus cacuminatus n ˆ 40 Echinophoria woodringi n ˆ 31 Fusiturricula thranis n ˆ 34 Glyphostoma annae n ˆ 34 Hindsiclava militaris n ˆ 30 Mitra woodringi n ˆ 16 Natica scethra n ˆ 39 Polystira oxytropis ecuadoriana n ˆ 30 Sthenorytis dianae n ˆ 6 Strioterebrum guanabanum n ˆ 40 Thatcheria ecuadoriana n ˆ 3 Dalium ecuadorium n ˆ 87 Mean frequency of occurence

1 (0.12) 1 (0.20) 2 (0.06) 1 (0.07) 0 (0.00) 3 (0.10) 2 (0.06) 1 (0.03) 1 (0.03) 2 (0.12) 1 (0.02) 0 (0.00) 1 (0.16) 1 (0.02) 2 (0.66) 2 (0.02) 0.10

0 (0.00) 2 (0.40) 2 (0.06) 1 (0.07) 2 (0.05) 1 (0.03) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 0 (0.00) 5 (0.16) 0 (0.00) 1 (0.02) 0 (0.00) 0 (0.00) 0.05

1 (0.12) 3 (0.60) 4 (0.13) 2 (0.15) 2 (0.05) 4 (0.13) 2 (0.06) 1 (0.03) 1 (0.03) 2 (0.12) 1 (0.02) 5 (0.16) 1 (0.16) 2 (0.05) 2 (0.66) 2 (0.02) 0.16

Plain (Walker, 1992), the Miocene of the Korytnica Clays (Kern, 1979), the Miocene of the St. Mary's Formation (Walker, 1992), the shallow subtidal of the Pleistocene of southern California to Baja California (Kern et al., 1974), the Pleistocene of northern California in nearshore shelf deposits (Walker, 1988), and the nearshore shelf deposits of the GalaÂpagos Pleistocene (Walker, 1991). From the previous studies, it appears that this particular trace fossil is more characteristic of nearshore shelf habitats. Hermit crabs, however, have a wide bathymetric range and have the potential to travel great distances mixing deep-water shells with shallow-water shells (Walker, 1989). While this hermit crab-induced bathymetric sorting may have taken place, it may also be possible that Helicotaphrichnus has a deeper depth distribution than previously reported. Certainly, this is the ®rst time that the trace fossil, Helicotaphrichnus is recorded from the Upper Pliocene of the Panamic region (previously, it was

reported from the Pleistocene of the GalaÂpagos Islands, Walker, 1991). 3.3. Epibionts on the fossil shells Despite the Vokes' excellent curatorial cleaning, epibionts occurred on 12 of the gastropod species (20% of the species; Fig. 2 for encrusting species). Only 2% of the total individuals had encrusting organisms. Serpulid tubes, basal plates from balanid barnacles (Fig. 3C), an encrusting oyster (Ostreidae), an unidenti®ed encrusting solitary coral (Fig. 3D), large encrusting foraminiferans (Planorbulina spp.) and one bryozoan (a lichenoporid) occurred on the shells (Fig. 2). A similar encrusting guild (with the exception of the barnacles) was observed on tethered empty shells to a depth of 73 m in the Caribbean (Walker et al., 1998). Solitary corals occurred only on tethered gastropod shells that were emplaced for six years to a depth of 73 m in the Caribbean (Walker

Fig. 3. Endo- and epibionts on the Upper Pliocene deep-water gastropods. (A) Fusiturricula thranis with the trace fossil Helicotaphrichnus commensalis within the columella (arrow), shell height 38.21 mm. (B) Cantharus scissus with boring barnacles on the columella (arrow), shell height 35.48 mm. (C) Cantharus scrupeus with encrusting balanid barnacle plate on apex (arrow), shell height 32.60 mm. (D) Solitary coral encrusting Fusiturricula thranis, shell height 42.41 mm.

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et al., unpublished data). In the Caribbean, corals settle in response to coralline algae (E. Hoffman, personal communication, 1999). Indeed, many of the experimental shells with corals had coralline algae adjacent to the skeletonized polyp (Walker, personal observation, 1999). However, coralline algae were present on the experimental shells for ®ve years without coral recruitment to the shells. Perhaps this is due to the vagaries of coral recruitment or that the shell needed to ªseasonº for a long period of time before coral settlement. Although the fossil encrusting guild is similar to the encrusting guild on the Caribbean experimental shells, there is still too little information from the eastern Paci®c to determine the shell-guild's biogeographic af®nities. For example, Recent Bathybembix shells from bathyal depths of the eastern Paci®c had primarily serpulid tubes and spionid borings on the shells (Walker and Voight, 1994). But, serpulids are cosmopolitan in distribution and their tubes are dif®cult to assign to species. Therefore, serpulid worm tubes may not be good biogeographic indicators. The encrusting foraminiferans on the fossil shells may be of bene®t, but they appear to be of the cosmopolitan genus Planorbulina. Additionally, encrusting organisms are common on experimental shells in the Caribbean to a depth of 73 m but are rare on mollusc shells below depths of 200 m (Parsons et al., 1997; Walker et al., 1998). If these fossil molluscs are inferred to be at a depth of 73 m, they should have more preservable bionts present on their shells. Future collections of deep-water molluscan fossils should be treated with care and washed very carefully to prevent dislodgment of the epibionts from the shell. That way, the maximum amount of paleoecological information can be retained on the shells. Fossil epi- and endobiont trace fossil information was important for determining hermit crab-inhabitation of the shells. Using the fossil bionts, one can also determine the particular shell type most commonly inhabited by the hermit crabs. A particular suite of trace fossils (e.g. boring bryozoa, boring barnacles, and boring spionids such as Helicotaphrichnus) with epibionts (serpulid polychaete tubes) associated with the aperture region of the fossil shells are considered to be diagnostic criteria for hermit crab-inhabitation of the shell (after Walker, 1988, 1992; Walker and Carlton, 1995). Using the biont criteria, only 16 of

the 59 (or 27%) of the gastropod species were once affected by hermits (Table 1). The 16 gastropod species represented a wide range of morphology, from large aperture and round shells of the bathyal Natica scethra and Dalium ecuadorium, to highspired shells with small apertures such as Fusiturricula thranis. The most commonly used morphotype, however, appeared to be shells with a large last whorl volume (i.e. Cantharus scissus, Cantharus scrupeus, Cancellaria esmeralda, Polystira ecuadoriana, and Thatcheria ecuadoriana). The results of the present study revealed that even though the shells were cleaned by the curation process, well preserved epi- and endobionts did occur on the fossil deep-water shells and were useful for paleoecological and paleobiogeographic interpretations. The biont guild on the Ecuador fossils was similar to those reported from experimental shells in the Caribbean to a depth of 73 m (Walker et al., 1998). However, the presence of the suspension-feeding barnacles and spionid polychaetes on the shells (which are absent on experimental shells in the Caribbean) may indicate that the Bolivar Strait waters were more nutrient-rich than those in the Recent Caribbean. 3.4. Biological remanie and Recent shallow-water epibionts on deep-water Pliocene shells Two Upper Pliocene bathyal gastropods (Dalium ecuadorium and Turricula spp.) were commonly reworked into the modern intertidal of Punta Gorda. These species are excellent examples of time-skewed and habitat-skewed biological remanie because they are reworked from their slope (bathyal) deposits into the adjacent intertidal at Punta Gorda (Walker, personal observation, 1994). In particular, Dalium ecuadorium entered into a form of ªtaphonomic feedbackº (Kidwell and Jablonski, 1983). That is, its dead Pliocene hardparts in¯uenced the settling of Recent organisms: hermit crab occupants with their epibionts and other invertebrates. For example, empty Dalium were lodged within bedrock crevices in the intertidal zone with their apertures exposed to Recent mussel colonization (Fig. 4A). Approximately 20% of the hermit crab population (of the high intertidal marine hermit crab, Clibanarius) used the empty fossil shells of Dalium as domiciles (Fig. 4B).

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Fig. 4. Recent biological reÂmanie (taphonomic feedback) on the bathyal Pliocene gastropod, Dalium ecuadorium. (A) Recent mussels encrusting the aperture, shell height 37.51 mm. (B) Recent marine hermit crab, Clibanarius, inhabiting a fossil Dalium, shell height 30.17 mm.

Recycling and retention of fossil gastropods by hermit crabs can occur if the fossil deposits erode into the modern intertidal (Walker, 1989, 1994). The deep-water shells of Dalium are quite robust and if the Recent intertidal became an obrution deposit on this tectonically active coast, then a future paleoecologist would have quite a time trying to ®gure out the bathymetric relationships of the shells. This problem has been particularly true for the paleoecological interpretation of the Pleistocene shells from the tectonically active Californian coast where deep-water shells in shallow-water deposits are attributed to a variety of biological and physical factors including older shells reworked into younger deposits (Woodring et al., 1946; Emerson and Addicott, 1953; Emerson, 1956; Valentine and Mallory, 1965; Addicott, 1966, 1969; Zinmeister, 1974; Walker, 1989). It is not known how extensive these temporal anomalies are in Central or South American fossil deposits.

3.5. Shell repair overview Predation is generally considered to be more common in shallow-water environments, while deep-water habitats are considered to be safe places for relicts of the Paleozoic and weakly defended invertebrates that tend to lack predatory defenses (Vermeij, 1987). Vermeij (1987, p. 106) stated that this generalization is provisional and he underscored the need to study deep-water habitats to critically examine this generalization. Indeed, it is now thought that predation is a potentially important factor for structuring deep-sea benthic communities (Jumars and Eckman, 1983; Grassle, 1989) and this may be true of deep-water environments as well. Recent work on shell repair on deep-water gastropods indicates that it is more common than previously thought. Repaired shells of small (,3 mm) living prosobranch gastropods from outer shelf to abyssal depths were common, however, no depth trends were evident (Vale and Rex,

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Fig. 5. Shell repair frequency of occurrence on the Upper Pliocene deep-water gastropod shells.

1988, 1989). The median frequency of repair for these deep-water gastropods falls within the values for temperate and tropical shallow-water sites (Vale and Rex, 1989, 1988). Vale and Rex (1989) also found that there was no convincing evidence that differences in shell size and architecture were related to predation. They suggested that their ®ndings supported the hypothesis that gastropod prey and their predators are more ªgeneralizedº in deep-water habitats compared to shallow-water habitats. High shell repair frequencies were also found on large (.20 cm) deep-sea (bathyal) gastropods, Gaza and Bathybembix (Walker and Voight, 1994). Both Gaza and Bathybembix have relatively thin shells with large apertural openings (Hickman and McLean, 1990). This type of shell architecture is susceptible to crushing by durophagous prey yet these shells retain frequent repair scars. In contrast, Kropp (1992) found low frequencies of shell repair for prosobranch gastropod species examined from inner shelf to slope environments off Point Conception, California. It is not clear, however, if live or dead species of gastropods (or both) were used for his analysis nor was it clear how he recorded shell repair frequencies. Relatively few papers have been published on shell repair in deep-water environments. What has been published, indicates that shell repair does occur in modern deepwater habitats and may be more signi®cant than

previously thought. This modern record may therefore be used to compare to the fossil record of deep-water gastropods. The incidence of shell repair on relatively large (.10 mm) Pliocene gastropods was examined in addition to whether shell architecture was associated with the incidence of predation. For shell architecture, shell repair would be less likely on thin shells with large round apertures because these shells would be readily destroyed by peeling and crushing crabs (see Vermeij, 1979). Alternately, shell repair should occur frequently on high-spired shells with narrow apertures because the living snail can retract farther back into the shell, making it harder for the crab to extract the prey and more likely for unsuccessful predation to occur (Signor, 1985; Vermeij, 1987). Similarly, well-armored, low-spired and narrow-aperture gastropods should also have high repair, as it would be more dif®cult to peel the shells (Vermeij, 1979, 1987). 3.6. Shell repair on deep-water Pliocene gastropods The incidence of major shell repair was quite high for the Pliocene deep-water gastropods. Major shell repair occurred on 66% of the 59 species and 25% of the individuals (Fig. 5). The method section discusses how the frequency of shell repair was calculated (Section 2.2). Multiple repair scars were not as

S.E. Walker / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 141±163

common on the shells: 31% of the 59 species and 5% of the individuals had evidence of more than one predation attempt per shell (Fig. 5). Few shells had shell repair on the apex whorls. In contrast, most shell repair occurred on either the last whorl (Fig. 6A and B) or other whorls (Fig. 5). Sander and Lalli (1982) also observed that large, deep-water gastropods had shells with a high percentage of ªmutilatedº lips. They tentatively concluded that predation mortality was very high in the mollusc populations from their sites near Barbados. The results reported here do suggest that predation may be an important agent of selection for large, deep-water gastropods, but more data is needed on bulk modern and fossil mollusc populations to address whether predation is an important selection agent in structuring deep-water communities. 3.7. Shell repair and shell architecture Fourteen species of deep-water gastropods with a relatively large sample size (ranging from 16 to 87 individuals) were used to determine if shell architecture was correlated with the frequency of shell repair (Fig. 7). These fourteen species were organized into four groups. Group 1 was represented by the gastropods Natica scethra …n ˆ 39† and Dalium ecuadorium …n ˆ 87†; taxa that are low-spired, with thin shells and rounded apertures. These shells should be predicted to have less shell repair because they are vulnerable to successful predation. The second group represented high-spired, narrow-aperture species: Compsodrillia paci®ca …n ˆ 32†; Strioterebrum guanabanum (Fig. 6C; n ˆ 40†; Hindsiclava militaris …n ˆ 30†; Fusiturricula thranis …n ˆ 34†; and Glyphostoma annae …n ˆ 34†: Group 2 species would be predicted to have the highest frequency of shell repair because the living mollusc can retract deeply within the shell, making extraction of the food less cost effective for the predator. Group 3 represented species that were low-spired but with a relatively thick or slightly armored angular aperture: Echinophoria woodringi …n ˆ 31†; Cantharus scissus …n ˆ 31†; and Cancellaria trochilia …n ˆ 17†: Group 3 species would also be predicted to have a high frequency of repair but less than that of Group 2. Group 4 was comprised of low-spired species with narrow and unarmored apertures: Neosconsia ecuadoriana …n ˆ 25†; Mitra woodringi …n ˆ 16†; Conus cacuminatus …n ˆ 40†; and Conus

151

camarones …n ˆ 26†: Group 4 species would be expected to have high shell repair similar to Group 2 because of the greater dif®culty for a crab to manipulate the narrow apertures. Shell repair was signi®cantly different between the fourteen species (F-ratio ˆ 4.41, p ˆ 0:00† and between the groups (F-ratio ˆ 9.59, p ˆ 0:00†: Results indicated that Group 1 species appeared to have the lowest incidence of shell repair and Group 2, the highest amount of shell repair (Fig. 6). However, a least-squared-mean analysis revealed that Group 2 and Group 3 had the highest mean occurrence of shell repair, while Group 4 had the lowest. A Tukey±Kramer analysis showed that Group 2 was signi®cantly different from all other groups …0:03 , p . 0:00†: Groups 1, 3 and 4 were not signi®cantly different from each other. A least-squared-mean analysis indicated that only some of the species within Group 2 affected the statistical signi®cance. Three of the ®ve species within Group 2 have the highest shell repair occurrence: C. paci®ca, F. thranis and G. annae (Fig. 7). A Tukey±Kramer analysis revealed that C. paci®ca was signi®cantly different from almost all other species (except for F. thranis and G. annae). For multiple shell repair, there was no signi®cant difference among the species (F-ratio ˆ 1.42, p ˆ 0:32† or groups (F-ratio ˆ 1.91, p ˆ 0:13†: Most of the shell repair on the species examined occurred on the last whorl or other whorls not associated with the apex. There was a signi®cant difference between the species that had shell repair on the last whorl (F-ratio ˆ 2.03, p ˆ 0:02†: Analysis of shell repair on the last whorl between the groups, however, was not statistically signi®cant (Fratio ˆ 1.97, p ˆ 0:12†: Within the species, leastsquared-mean analysis revealed that C. trochilia (from Group 3), C. camarones (from Group 4) and C. paci®ca (from Group 2) had the highest mean incidence of repair in this region. In contrast, C. cacuminatus (from Group 4) had the lowest incidence of shell repair in this region. A Tukey±Kramer analysis revealed that C. camarones (from Group 4) was signi®cantly different from the Group 1 species, N. scethra …p ˆ 0:05† and D. ecuadorium …p ˆ 0:03†: All other species were not signi®cantly different from each other. Shell repair on the apex whorls was not signi®cantly different between the species (F-ratio ˆ 1.01,

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153

Fig. 7. Frequency of occurrence of shell repair, multiple repair scars, and location of repair scars on a selected subset of the Upper Pliocene gastropods. Groups are indicated by numbers to the left of the species names (see text for explanation).

p ˆ 0:44† or between groups (F-ratio ˆ 0.62, p ˆ 0:60†: Fusiturricula thranis was statistically different from all other species tested as it had a relatively high incidence of shell repair in the apex region. Shell repair that occurred on other whorls (not the apex or last whorl) was statistically signi®cant between species (F-ratio ˆ 3.41, p ˆ 0:00† and among the groups (F-ratio ˆ 6.57, p ˆ 0:00†: Least-squaremean analysis indicated that Group 2 had the highest incidence of shell repair in this region. A Tukey± Kramer analysis further revealed that Group 2 was

signi®cantly different from Group 1 …p ˆ 0:02†; Group 3 …p ˆ 0:01† and Group 4 …p ˆ 0:00†: Group 2 species, C. paci®ca, H. militaris, and F. thranis had the highest mean incidence of shell repair in this region. Groups 1, 3 and 4 were not signi®cantly different from each other. In summary, Group 2 species had the highest incidence of shell repair and Group 4 had the lowest mean incidence of shell repair. Group 1, 3 and 4 species were not statistically different in the frequency of shell repair. Only three of the ®ve species within

Fig. 6. Predation recorded on the shells of the Upper Pliocene deep-water gastropods. (A) Shell repair on the last whorl of Phos (Metaphos) paci®cus, shell height 40.18 mm. (B) Shell repair on the bathyal species, Dalium ecuadorium, shell height 26.68 mm. (C) Shell repair and drilling predation on Strioterebrum guanabanum, shell height 45.27 mm. (D) Naticid drilling predation on Cantharus scissus, shell height 32.19 mm.

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Fig. 8. Frequency of complete and incomplete drill holes, multiple borings and location of drill holes (aperture or external side of the shell) on the Upper Pliocene gastropods.

Group 2 had a high incidence of shell repair. This high incidence of shell repair was due to major repair scars that occurred on whorls other than the apex and last whorls of the shell. Thus, the null hypothesis that there is no difference in shell repair among the species is not supported by the data. The prediction that the highest amount of shell repair would be found in Group 2 species is not refuted, although the statistical signi®cance is due to only three of the ®ve species within this group that have the highest incidence of shell repair. The prediction that Group 1 (low-spired, round apertures and thin shells) would have signi®cantly lower repair frequencies from all other groups because of their vulnerable shells was not borne out by the data. The prediction that Group 3 (low-spired, thick or armored apertures) would have a high frequency of repair similar to Group 2 was also not supported by the data. Although Group 4 had the lowest mean occurrence of shell repair among the species, this group was not signi®cantly different from Groups 1 and 3. Thus, it appears that shell architecture may affect only the incidence of shell repair for high-spired deep-water gastropods that can retract deeply within their shells. Perhaps, durophagous predators that peel shells (such as crabs) may not be generalists in deepwater habitats. But, it is also likely that some prey species may be in locations were predators are

common or have behaviors that allow them to be protected from predators (Kropp, 1992; CadeÂe et al., 1997). 3.8. Drilling predation on Pliocene deep-water gastropods Few data exist on the incidence of predatory drilling on mid-to-outer shelf and bathyal molluscs in Recent environments. Sander and Lalli (1982) examined Recent molluscs from collections recovered between 125 and 225 m in water depth off Barbados Island in the Caribbean. They reported very high rates of drilling predation for most gastropod species in their samples (up to 75% of individuals drilled for some species). Sander and Lalli (1982) suspected that a wide range of drilling predators, including the genera Cymatium, Distorsio, Morum, Natica, Phalium and Polinices, were responsible for the drill holes. They concluded that drilling predators played a very important role in the deep-water communities they examined. Mollusc predators that drill may have also played a very important role in deep-water environments during the Upper Pliocene in the Bolivar Trough. Complete drill holes were present with a frequency of 68% on the fossil gastropods; of the individuals, 32% were completely drilled (Fig. 8). Incomplete drill

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155

Fig. 9. Frequency of drill hole type on the Upper Pliocene gastropods.

holes and multiple drillings were also frequently encountered on the shells (Fig. 8). Drill holes could occur on either the aperture or external (away from the aperture) side of the shell with equal frequency (Fig. 8). Countersunk boreholes (from naticid gastropod predators) were the most frequently encountered drill hole type and occurred on 47% of the shells examined (Figs. 5D and 9). Octopod and muricid drill holes were less frequently encountered, each occurred on 25% of the shells examined (Fig. 9). Drill holes that could not be attributed to a speci®c predator or that were taphonomically altered occurred on 45% of the shells (Fig. 9). Sixteen species of gastropod had relatively high frequencies of drilling predation (Fig. 10). Drill hole occurrence, however, was signi®cantly different between the species (F-ratio ˆ 8.78; p ˆ 0:00†: Least-square-mean analysis indicated that high-spired gastropod species were the most frequently drilled (i.e. Polystira andersoni, Polystira ecuadoriana, Polystira haitensis, Compsodrillia paci®ca, Strioterebrum guanabanum, and Fusiturricula thranis). Polystira species contained the highest frequency of drilled shells and multiple drilled shells (Fig. 10). A similar high frequency of drilling was reported for a Polystira species from bathyal depths in the Caribbean (Polystira tellea, 75% were drilled; Sander and Lalli, 1982). Dalium ecuadorium, Phos paci®cus, and Cantharus scissus had the lowest frequency of drilled shells. All of the frequently drilled species

were signi®cantly different from each other (Tukey± Kramer analysis, 0:03 , p . 0:00†: For multiple drilled shells, only C. paci®ca and P. ecuadoriana were signi®cantly different from the others (Tukey± Kramer analysis, 0:03 , p . 0:00†: Because the sample size averaged 30 individuals per most species examined, it appears that the high-spired species were indeed the most drilled species. Naticid drill holes occurred with the highest frequency on chie¯y turrids (i.e. P. andersoni, P. ecuadoriana, C. paci®ca, P. haitensis) and the naticid, N. scethra (Fig. 11). Polystira andersoni had the highest frequency of naticid drillings (Fig. 11) and was signi®cantly different from almost all other species in the frequency of naticid borings (Tukey±Kramer analysis, 0:01 , p . 0:00†: Natica scethra, C. paci®ca and P. haitensis were signi®cantly different only from species with the lowest frequency of drilling (Tukey±Kramer analysis, 0:01 , p . 0:00†: Octopod drill holes were also signi®cantly different between the species (F-ratio ˆ 2.15, p ˆ 0:01†: Highspired species had the highest level of octopod drilling (i.e. C. paci®ca, P. haitensis, S. guanabanum, and P. ecuadoriana; Fig. 11). Muricid drilling was also signi®cantly different between the species (Fratio ˆ 2.44, p ˆ 0:00†: Mitra woodringi, C. camarones, C. scissus, and G. annae had the highest frequency of muricid drillings. Unknown drillings were also signi®cantly different between the species (F-ratio ˆ 2.29, p ˆ 0:00†: The gastropod species,

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Fig. 10. Frequency of occurrence of drill holes (frequency of drilled, complete drill holes, incomplete drill holes and multiple drillings) on a subset of the Upper Pliocene gastropods. Complete drill hole frequency is determined by the total number of complete drill holes per shell divided by the number of individuals within the species examined.

S. guanabanum, P. paci®cus, and G. annae, had the highest frequency of unknown drill holes (Fig. 11). In summary, the results clearly show that drilling predation is important in this deep-water molluscan assemblage from the Upper Pliocene of Ecuador. Naticid, muricid and octopods were the most common predators entombed within the turbiditic beds. A high frequency of drilling was also found along a depth gradient in the Eocene of the Atlantic Gulf and Coastal Plain (Hansen and Kelley, 1995). However, the outer shelf environment (the Yazoo Formation) examined by Hansen and Kelley (1995) had a lower incidence of drilling predation (21.2%) than recorded here for the Esmeraldas fossil gastropods. Selection by the predators for their favored prey is evident in this mixed assemblage. Naticids appeared to favor high-spired gastropods, like Polystira, or their own low-spired conspeci®cs. Selection by naticids for

particular prey has also been reported from Eocene shelf environments of the Atlantic Gulf and Coastal Plain (Hansen and Kelley, 1995). They found that naticid drill holes were highly correlated with highspired turritellid species and low-spired hipponicid species. Cannibalistic behavior is also well documented for naticids by Kelley (1991), who showed that this behavior is the expected result of selective predation. Octopods also appeared to select high-spired gastropod species. Muricids appear to favor lowspired forms (e.g. Conus and Cantharus species). Thus, the drilled prey that are encapsulated in this turbiditic deposit do not appear to be the result of generalist predators. Rather, prey selection by a suite of predators appears to be common and lends support to the hypothesis (after Sander and Lalli, 1982) that predation is important for structuring benthic communities in deeper water habitats.

S.E. Walker / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 141±163

157

Fig. 11. Frequency of occurrence of drill hole type (naticid, muricid, octopod or unknown) in a subset of Upper Pliocene gastropods. Frequency is determined by the least number of drill hole types per shell divided by the number of individuals within the species.

4. Conclusions Fossil gastropods from the mid-to-outer shelf and bathyal environments of the Upper Pliocene of northern Ecuador retain a wealth of paleoecological information recorded on their shells. This paleoecological information provides evidence for an encrusting and bioeroder guild of organisms that can then be compared to other regions. For example, the fossil encrusting guild was similar to the shell-encrusting guild found on experimentally deployed shells in the Caribbean (Parsons et al., 1997; Walker et al., 1998). However, there is still very little information on encrusting guilds associated with deep-water gastropods from the eastern Paci®c (Walker and Voight, 1994). The encrusting guild present on the fossil shells from the Upper Pliocene does suggest that suspension-feeding organisms were present in this assemblage indicating that enough particulate food was available to support these organisms, especially the

encrusting and bioeroding barnacles and spionid polychaetes. The encrusting and bioeroding guild associated with the shell can also be used to infer whether the shell was inhabited by other components of the community, such as hermit crabs, which do not have a fossil record from these Upper Pliocene beds. Using biont criteria, hermit crabs occupied 27% of the Upper Pliocene gastropod species examined. A trace fossil Helicotaphrichnus, which is unique to hermit crabinhabited shells, was used to determine that the most commonly used shell type were those with a large last whorl volume. Thus, it may be possible to infer some selection for favored shell types in the past by using the biont criteria associated with hermited shells. Additionally, Helicotaphrichnus is reported for the ®rst time from Upper Pliocene beds in the eastern Paci®c. Because of its association with Dalium, a bathyal species, this trace fossil may have a deeper bathymetric distribution than previously reported.

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However, hermit crabs can transport gastropod species across bathymetric gradients (Walker, 1989). Therefore, further evidence is required from deepwater modern shells occupied by hermit crabs to determine the actual bathymetric range of the spionid polychaete that makes the Helicotaphrichnus trace in shells. Paleoecological information from shell repair showed that the Upper Pliocene gastropods were subject to a variety of predators which frequently attacked the shells. For example, drilling predation occurred on 68% of the gastropod species examined. The Upper Pliocene molluscan predators (i.e. muricids, naticids, and octopods) also appeared to show prey selection. For example, deep-water naticids selected high-spired prey and their own conspeci®cs while muricids selected low-spired prey. Octopods appear to drill similar prey species favored by naticids. There is enough evidence to show that drilling predation is not a generalist activity, but rather a specialist activity in deep-water turbiditic assemblage examined for this paper. The incidence of shell repair (66% of the species examined) on the deep-water Pliocene gastropods is similar to the incidence of repair reported for shallow shelf environments (Geller, 1983; Vermeij et al., 1980; CadeÂe et al., 1997; Table 2 in Vale and Rex, 1988). However, the frequency of shell repair (i.e. the percentage of shells with at least one repair) can have high inter-habitat variation in shallow-water environments (Geller, 1983; CadeÂe et al., 1997). Additionally, habitat-mixing, time-averaging and collection bias may also affect the variation seen in reported repair frequencies (CadeÂe et al., 1997). Certain gastropod species were more prone to shell repair than others in the Upper Pliocene assemblage despite the potential biases afforded by time-averaging, habitat-mixing or collection. Shell architecture may affect the frequency of predation in deep-water habitats for some species of gastropods. High-spired species with narrow apertures had signi®cantly more shell repair than all other architectural groups tested. Only three of the ®ve species within the high-spired group, however, had high shell repair rates that were signi®cantly different than the rest of the species tested. Biological remanie was also observed to take place in the modern intertidal adjacent to the uplifted slope

deposits of the Punta Gorda fossil locality. Bathyal shells of the Upper Pliocene gastropod Dalium ecuadorium and Turricula sp., which had eroded out of the surrounding mudstones, were reworked as individual shells into the modern intertidal. Dalium, in particular, was used in a type of temporal taphonomic feedback (after Kidwell and Jablonski, 1983) where approximately 20% of the Recent hermit crab population used the fossil shells. Additionally, Recent mussels were found encrusting fossil Dalium shells that were lodged within bedrock crevices. Usually the taphonomic-temporal anomaly of fossils reworked into modern systems is rarely reported and is limited to a few fossil shells (reviewed by Walker, 1989), but this resurrection of robust bathyal Pliocene shells into the high intertidal is quite the exception. The deep-water environment is a vast area that encompasses many habitats and many depths. This research illustrates the need for more comparative information between deep-water communities from mid-to-outer shelf and bathyal environments. Fossils of deep-water gastropods do retain paleoecological information, such as suspension-feeding shell epibionts and bioeroders that use the shell as a substratum. These epibionts and trace fossils, in turn, can be used to infer that poorly preserved organisms also associated with the gastropod assemblage (i.e. hermit crabs). Drill holes provide a record of predatory organisms that are not preserved in the assemblage (i.e. octopods). The record of shell repair on the deep-water shells also indicates that predatory organisms may have been quite common despite the lack of preservation of these organisms. Thus, fossil deep-water molluscan communities retain a rich and as yet, poorly examined record of paleoecological interactions. These interactions will be important for addressing evolutionary ecological questions pertaining to selective predation with depth, paleoecological documentation of the encrusting and bioeroding guild with depth, and in this case, differences in the paleoecological structure of these communities before and after the closure of the Isthmus of Panama. Acknowledgements This research could not have been conducted without the Ecuadorian molluscan collections of Emily

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and Harold Vokes. Emily and Harold Vokes generously provided access to the beautiful molluscan specimens and hospitality during two trips by the author to Tulane University. Additionally, Emily, Harold, and William Miller, III, were instrumental in inviting the author to the Esmeraldas and Punta Gorda, Ecuador, which culminated in this project. Fausto Cortez, the author's invaluable ®eld assistant, tirelessly collected fossil Dalium from the Punta

159

Gorda deposit. Suzanne White and Lisa Miller kindly critiqued the ®rst draft of this manuscript. Dan Miller is especially thanked for his thorough review of this manuscript. An anonymous reviewer also contributed to improving this manuscript. Research concerning Recent experimental shells in the Caribbean has been generously supported by NOAA, NURP, and NSF research grants awarded to the SSETI project (Shelf/Slope Taphonomic Initiative).

Appendix A. Upper Pliocene gastropods examined, including sample size (n), Tulane locality, and comments on depth distributions (depth information from Olsson, 1969; Keen, 1971) Family level and species

n

Tulane locality

Comments on depth

Architectonidae Architectonia nobilis

6

Tu1397

Recent species to depths of 37 m

Buccinidae Cantharus scrupeus Cantharus scissus Gordanops ?esmeraldensis Phos (Metaphos) scillus Phos (Metaphos) calathus Phos (Metaphos)?paci®cus Phos sp.

13 31 2 1 1 30 28

Tu1397 Tu1397 Tu1397 Tu1397 Tu1397 Tu1397 Tul397

Recent Cantharus spp. depths range between intertidal and 333m. Phos (Metaphos) considered to be moderately deep water species: Recent species between depths of 37 to 232 m

Bursidae Bursa sp.

5

Tu1397

In general, Recent Bursa spp., off the coast of Ecuador, down to depths of 120 m.

Cancellariidae Cancellaria esmeralda Cancellaria fragosa Cancellaria marksi Cancellaria trochilia Cancellaria xenia

5 2 6 17 1

Tu1397 Tu1397 Tu1397 Tu1397 Tu1397

Recent Cancellaria mostly an offshore species (Ecuador and GalaÂpagos).

Capulidae Capulus paci®cus

8

Tu1397

No information

Cassididae (Cassidae) Echinophoria woodringi Neosconsia ecuadoriana

31 25

Tu1397 Tu1397

E. woodringi: Probably deep water species (Olsson, 1969); Recent Cassids of Ecuador are offshore species.

Columbellidae Strombina (Cotonopsis) esmeraldensis

30

Tu1397

Recent species off the coast of Ecuador and Peru are offshore to depths of 100 m.

Conidae Conus angusturis

3

Tu1397

Conus cacuminatus Conus camarones Conus gripsus

40 26 1

Tu1397 Tu1397 Tu1397

Recent Conus spp. off Ecuador from intertidal to offshore (165 m).

160

S.E. Walker / Palaeogeography, Palaeoclimatology, Palaeoecology 166 (2001) 141±163

Appendix A (continued) Family level and species

n

Tulane locality

Comments on depth

Cymatidae Distorsio gatunensis

3

Tu1397

Similar Recent Distorsio decussata and D. constricta, offshore to depths of 82 m.

Epitonidae Amaea (Scalia) ferminiana Cirsotrema togatum Sthenorytis turbinus Sthenorytis dianae

4 2 2 6

Tu1397 Tu1397 Tu1397 Tu1397

Recent A. ferminiana found between depths of 43 m and 277 m; similar Recent species of Sthenorytis are deep water forms. Recent Cirsotrema togatum has a Recent depth distribution between 32 and 113 m.

Fasciolariidae Fusinus vokesi Fusinus esmeraldas

2 12

Tu1397 Tu1397

Mostly offshore to deep-water forms. Recent F. fragilissimus to depth of 2877 m; F. panamensis to depths from 35 to 275 m; F. dupetitthouarsi on mud¯ats to depths of 55 m.

Ficidae Ficus lanzi Ficus perplexa

1 1

Tu1397 Tu1297

Recent Ficus ventricosa is an offshore species.

Mitridae Mitra henekeni Mitra woodringi

6 16

Tu1397 Tu1397

Recent Mitra species occur off the coast of Ecuador between 5 and 73 m.

Naticidae Natica scethra

39

Tu1397

Recent N. scethra dredged from 277 m in Bay of Panama; to 280 m in Keen (1971).

Neptunidae Kelletia ecuadoriana

5

Tu1397

No information

Olividae Oliva cayapa

1

Tu1397

Recent Oliva spp. are intertidal

Oocoritidae or Oocorythidae Dalium ecuadorianum Dalium n. spp.

87 1

Walker collec.

Deep water species (bathyal)

Terebridae Buridrillia weberi

4

Tu1397

Hastula stalagina Strioterebrum guanabanum Strioterebrum indocayapum Terebra M. cf. ornata Thatcheria C. ecudoriana

2 40 2 2 1

Tu1397 Tu1397 Tu1397 Tu1397 Tu1397

Recent terebrid species off Ecuador, intertidal to 90 m (T. elata; T. hancocki; T. puncturosa); Recent Terebra lucana, 11± 275 m; Recent Terebra lucana, 11±275 m; Recent T. purdyae, 15±146 m.

8 18

Tu1397 Tu1397 Tu1397 Tu1397 Tu1397 Tu1397 Tu1397 Tu1397

Turritidae Aforia ecuadoriana Coclespira (Ancistrosyrinx) cedonulli Coclespira (Ancistrosyrinx) sp. Compsodrillia paci®ca Glyphostoma annae Glyphostoma gracilus Glyphostoma katherinae Fusiturricula thranis

32 34 1 4 34

Recent Aforia goodei from depths 1220 to 1950 m. Recent Cochlespira cedonulli between 55 and 275 m. Scobinella ecuadoriana probably lived in very deep water (Olsson, 1969). Recent Fusiturricula (from GalaÂpagos) between depths of 90 to 180 m. Recent Glyphostoma species 20±50 m off the coast of Ecuador (G. neglecta). Recent Hindsiclava militaris off Columbia between depths of 20±55 m. Recent Polyspira oxytropis, offshore to 110 m.

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161

Appendix A (continued) Family level and species

n

Tulane locality

Hindsiclava militaris Polystira andersoni Polystira hiatensis Polystira oxytropis ecuadoriana Scobinella ecuadoriana Thatcheria (Conicheria) ecuadoriana

30 15 13 30 16 3

Tu1397 Tu1397 Tu1397 Tu1397 Tu1397 Tu1397

Volutidae Calliotectum ®sheri

6

Tu1397

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Comments on depth

Recent Calliotectum vernicosum off the coast of Ecuador from depths 741 to 1036 m.

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