A small yet occasional meal: predatory drill holes in Paleocene ostracods from Argentina and methods to infer predation intensity

Abstract

Ostracods are common yet understudied prey item in the fossil record. We document drill holes in Paleocene (Danian) ostracods from central Argentina using 9025 specimens representing 66 species. While the percentage of drilled specimens at assemblage-level is only 2.3%, considerable variation exists within species (0.3-25%), suggesting prey preference by the drillers. This preference is not determined by abundance because no significant correlation is found between species abundance and drilling percentages. Seven methods were used, some of which are new, to quantify drilling percentages for the abundant and commonly drilled Togoina argentinensis. The resulting range, from 9.9% to 14.6%, suggests that drilling percentages are fairly insensitive to the method used, implying that comparisons across studies are possible. This information, combined with data from the literature, suggests the Cretaceous-Palaeogene mass extinction may have had a limited effect on drilling intensity in ostracods. The cylindrical (Oichnus simplex) and parabolic (O. paraboloides) drill holes from Argentina may have been caused primarily by naticid and possibly muricid gastropods. Two oval drill holes (O. ovalis) are morphologically similar to octopod drill holes, but their small size, the fact that extant octopods are not known to drill ostracods and the absence of such holes in co-occurring gastropods, preclude ascription to a predator clade. Drill holes are located preferentially in the median and dorsal regions, where most soft tissue, including the adductor muscle, is located. Drilled specimens are statistically taller than non-drilled specimens for T. argentinensis and larger predators selected larger ostracods. The drilling percentage does not significantly differ in ornamented ostracods.

Cryptic moulting behaviour of some Carboniferous Ostracoda

“…2019; Villegas‐Martin et al . 2019 and references therein). Therefore, some moulting arthropods retreat to a sheltered place while the new exoskeleton is formed and hardened (e.g.…”

Bounded by crises: An overview of the evolution of marine ostracods during the Triassic

“…Identifiable traces of predation on ostracods in the fossil record are related to drilling Naticidae and Muricidae gastropods (e.g., Maddocks, 1988;Reyment and Elewa, 2002), the oldest record being of Early Albian, Early Cretaceous, age (Maddocks, 1988). Predation on ostracods is most of the time disregarded and most works focus on relatively young assemblages (e.g., Reyment et al, 1987;Ruiz et al, 2010Ruiz et al, , 2011Villegas-Martin et al, 2019). Because of the small size of ostracods, they provide an important food source for juvenile gastropods as well as an alternative nutritive resource when regular preys are lacking (e.g., Reyment, 1967;Maddocks, 1988).…”

Predation in the marine fossil record: Studies, data, recognition, environmental factors, and behavior

“…Because of problems in interpreting selectivity from repair scars, much of the fossil evidence interpreted as supporting selectivity of prey species comes from shell-drilling predation (but see Leighton, 2002). Examples include prey taxon selectivity of ostracods in the Paleocene of Nigeria (Reyment and Elewa, 2003) and Argentina (Villegas-Martín et al, 2019); mollusks from the Triassic of Italy (Klompmaker et al, 2016a), the Miocene of Bulgaria (Kojumdjieva, 1974) and Poland (Hoffman et al, 1974), and the Pliocene of Spain (Hoffman and Martinell, 1984) and The Netherlands (Klompmaker, 2009); of gastropods in the Miocene of Panama (Fortunato, 2007) and the Pliocene of Ecuador (Walker, 2001); and among brachiopods in the Devonian of New York state, USA (Smith et al, 1985) and the Miocene of Poland (Baumiller and Bitner, 2004). Selectivity of prey taxon is consistent with studies that have found a lack of correlation between drilling frequency and relative abundance (encounter frequency) of taxa (Kelley and Hansen, 2006;Martinelli et al, 2015), although more rigorous tests against null models of predator preference (per Smith et al, 2018) would be welcome.…”

“…Among drilling gastropods, muricids manipulate their prey less and show more random distributions of drill-hole sites on the prey shell compared to naticids (Carriker and Yochelson, 1968;Casey et al, 2015;Stump, 1975; but see , for muricid drilling on barnacles). However, stereotyped drill-hole positions have been reported on a wide range of prey: bivalves (Kelley, 1988;Kong et al, 2017;Taylor, 1970), gastropods (Berg and Nishenko, 1975;Blustein and Anderson, 2016;Taylor, 1970), scaphopods (Klompmaker, 2011;Yochelson et al, 1983), brachiopods (Ausich and Gurrola, 1979;Harper and Wharton, 2000;Smith et al, 1985), echinoids (Kowalewski and Nebelsick, 2003), barnacles (Donovan and Novak, 2015;, ostracods (Villegas-Martín et al, 2019), serpulid polychaetes (Martinell et al, 2012), and foraminifers (Malumián et al, 2007).…”