15
parasites are rare and difficult to find, it is possible to anticipate the potential presence of certain parasite taxa in fossil taxa of vertebrates, based on the kind of parasites which are found on their extant relatives or modern ecological equivalents.
This can be done by applying two concepts taken from palaeontology and ecology
respectively: Extant Phylogenetic Bracketing and Ecological Fitting.
Extant Phylogenetic Bracketing (EPB; Bryant and Russell 1992; Witmer 1995)
is often used for inferring the potential presence of certain soft tissues in extinct
taxa, however, it can also be applied in a manner to inferring the potential parasite
communities of extinct taxa. For example based on the ubiquity of tapeworms in
extant vertebrates, it is possible to infer that many extinct fossil taxa bracketed
within Vertebrata would had served as definitive hosts to the adult tapeworms (see
Fig. 1.1). Similar, for monogeneans discussed above, since they are found in all
extant groups of jawed fish and fossils of their hooks have been found on two wholly
extinct groups (placoderms and acanthodians), it is possible to infer that many
extinct taxa of fish could have potentially hosted monogeneans. By applying the
EPB framework to parasite communities of fossil taxa, this would allow us to use
their closest living relatives as a rough guide to the potential composition of their
parasite communities.
But what if the extinct taxa are morphologically and ecologically very different
from their closest living relatives (for example sphenacodontid synapsids, large theropod dinosaurs, sauropod dinosaurs, sauropterygians)? That is where the concept
of “Ecological Fitting” (Agosta and Klemens 2008) would be useful. The term was
coined by Janzen (1985) to describe an organism that is able to live and persist in a
Fig. 1.1 An example of applying Extinct Phylogenetic Bracketing to fossil host taxa. Here, the
focal parasites are the adult stage of cestodes (tapeworms). By looking at the extant groups which
are known to act as definitive hosts for cestodes, it can be inferred that some wholly extinct vertebrate taxa may have also hosted adult cestodes in their gastrointestinal tract. Silhouette of the different hosts are from PhyloPic (http://phylopic.org/)
1 Parasites of Fossil Vertebrates: What We Know and What Can We Expect…
parasites are rare and difficult to find, it is possible to anticipate the potential presence of certain parasite taxa in fossil taxa of vertebrates, based on the kind of parasites which are found on their extant relatives or modern ecological equivalents.
This can be done by applying two concepts taken from palaeontology and ecology
respectively: Extant Phylogenetic Bracketing and Ecological Fitting.
Extant Phylogenetic Bracketing (EPB; Bryant and Russell 1992; Witmer 1995)
is often used for inferring the potential presence of certain soft tissues in extinct
taxa, however, it can also be applied in a manner to inferring the potential parasite
communities of extinct taxa. For example based on the ubiquity of tapeworms in
extant vertebrates, it is possible to infer that many extinct fossil taxa bracketed
within Vertebrata would had served as definitive hosts to the adult tapeworms (see
Fig. 1.1). Similar, for monogeneans discussed above, since they are found in all
extant groups of jawed fish and fossils of their hooks have been found on two wholly
extinct groups (placoderms and acanthodians), it is possible to infer that many
extinct taxa of fish could have potentially hosted monogeneans. By applying the
EPB framework to parasite communities of fossil taxa, this would allow us to use
their closest living relatives as a rough guide to the potential composition of their
parasite communities.
But what if the extinct taxa are morphologically and ecologically very different
from their closest living relatives (for example sphenacodontid synapsids, large theropod dinosaurs, sauropod dinosaurs, sauropterygians)? That is where the concept
of “Ecological Fitting” (Agosta and Klemens 2008) would be useful. The term was
coined by Janzen (1985) to describe an organism that is able to live and persist in a
Fig. 1.1 An example of applying Extinct Phylogenetic Bracketing to fossil host taxa. Here, the
focal parasites are the adult stage of cestodes (tapeworms). By looking at the extant groups which
are known to act as definitive hosts for cestodes, it can be inferred that some wholly extinct vertebrate taxa may have also hosted adult cestodes in their gastrointestinal tract. Silhouette of the different hosts are from PhyloPic (http://phylopic.org/)
1 Parasites of Fossil Vertebrates: What We Know and What Can We Expect…