214
fossil (drill hole) Oichnus halo on the tests of Late Cretaceous (Campanian) to Early
Paleocene holasteroid echinoids. In this case the drill holes look exactly the same as
those produced by the recent cap-shaped eulimid genus Thyca. The drill holes are
sufficiently complex (concentric scars surmount the hole) and together with an echinoderm being the prey it is reasonable to assume that an eulimid gastropod was the
producer. In other cases, traces are not sufficiently complex, e.g. simple drill holes
or galls. There are several modern examples of galls produced by parasitic gastropods in skeletons of their host for instance eulimid galls in an echinoderm spine
(Warén 1983) and in principal, this has a fossilization potential but according to my
knowledge there are few reports of such cases from the fossil record (Boucot 1990;
Baumiller and Gahn 2002; Boucot and Poinar 2010). Breton et al. (2017) interpreted a bioerosion trace fossil on Cenomanian oysters as product of parasitic
gastropods.
Hayami and Kanie (1980) reported large Late Cretaceous (Campanian) limpets
(Gigantocapulus) in association with inoceramid bivalves. In analogy with some
recent gastropod limpets of the family Capulidae, they interpreted this as parasitism
(see also Baumiller and Gahn 2002). In the absence of protoconch and shell microstructure the assignment to Capulidae of this limpet is doubtful. Beu (2007) noted
that the systematic placement of Gigantocapulus is doubtful and placed it tentatively in the caenogastropod superfamily Vanikoroidea but stated it could also represent Monoplacophora. This author stated an epiparasitic mode of life was possible
but a filter feeding sedentarily on bivalves was more likely.
Petit et al. (2014) reported gastropods attached to fossil fishes, but their attribution to scavengers or parasites is not straightforward. They putatively assigned the
gastropod specimens to Aclis which is normally not associated with fishes.
6.2.2 Taxonomic Uniformitarianism
The most commonly used tool to infer parasitism in fossil gastropods is taxonomic
uniformitarianism. If for instance all extant pyramidellids are ectoparasites, it is
plausible and the most parsimonious assumption that fossil pyramidellid species
were parasites too and that this feeding type is a synapomorphy of this clade.
Difficulties arise when assignment of fossil species is uncertain and it may be
impossible to establish the life style of fossil sister-groups of parasitic families or
genera and hence the timing of the acquirement of the parasitic life style in evolutionary lineages. It is also generally true that taxonomic uniformitarianism becomes
increasingly problematic the higher the geological age is. As stated above, modern
groups of parasitic gastropods belong to ‘higher’ gastropods (Apogastropoda) i.e.,
Caenogastropoda and Heterobranchia and the mentioned families are usually present since the Late Cretaceous or Paleocene. Hence, it is evident that parasitism has
been pervasive at least since the Paleocene.
A. Nützel
fossil (drill hole) Oichnus halo on the tests of Late Cretaceous (Campanian) to Early
Paleocene holasteroid echinoids. In this case the drill holes look exactly the same as
those produced by the recent cap-shaped eulimid genus Thyca. The drill holes are
sufficiently complex (concentric scars surmount the hole) and together with an echinoderm being the prey it is reasonable to assume that an eulimid gastropod was the
producer. In other cases, traces are not sufficiently complex, e.g. simple drill holes
or galls. There are several modern examples of galls produced by parasitic gastropods in skeletons of their host for instance eulimid galls in an echinoderm spine
(Warén 1983) and in principal, this has a fossilization potential but according to my
knowledge there are few reports of such cases from the fossil record (Boucot 1990;
Baumiller and Gahn 2002; Boucot and Poinar 2010). Breton et al. (2017) interpreted a bioerosion trace fossil on Cenomanian oysters as product of parasitic
gastropods.
Hayami and Kanie (1980) reported large Late Cretaceous (Campanian) limpets
(Gigantocapulus) in association with inoceramid bivalves. In analogy with some
recent gastropod limpets of the family Capulidae, they interpreted this as parasitism
(see also Baumiller and Gahn 2002). In the absence of protoconch and shell microstructure the assignment to Capulidae of this limpet is doubtful. Beu (2007) noted
that the systematic placement of Gigantocapulus is doubtful and placed it tentatively in the caenogastropod superfamily Vanikoroidea but stated it could also represent Monoplacophora. This author stated an epiparasitic mode of life was possible
but a filter feeding sedentarily on bivalves was more likely.
Petit et al. (2014) reported gastropods attached to fossil fishes, but their attribution to scavengers or parasites is not straightforward. They putatively assigned the
gastropod specimens to Aclis which is normally not associated with fishes.
6.2.2 Taxonomic Uniformitarianism
The most commonly used tool to infer parasitism in fossil gastropods is taxonomic
uniformitarianism. If for instance all extant pyramidellids are ectoparasites, it is
plausible and the most parsimonious assumption that fossil pyramidellid species
were parasites too and that this feeding type is a synapomorphy of this clade.
Difficulties arise when assignment of fossil species is uncertain and it may be
impossible to establish the life style of fossil sister-groups of parasitic families or
genera and hence the timing of the acquirement of the parasitic life style in evolutionary lineages. It is also generally true that taxonomic uniformitarianism becomes
increasingly problematic the higher the geological age is. As stated above, modern
groups of parasitic gastropods belong to ‘higher’ gastropods (Apogastropoda) i.e.,
Caenogastropoda and Heterobranchia and the mentioned families are usually present since the Late Cretaceous or Paleocene. Hence, it is evident that parasitism has
been pervasive at least since the Paleocene.
A. Nützel