18
whether they be in amber, coprolite, or compression fossils. Amber is an exceptional material that can preserve many organisms intact and in some cases, in their
original ecological context (Poinar 1992), including some parasite-host relationships as shown through the examples discussed in this chapter. However, researchers must be mindful that amber is subjected to preservation biases (e.g. De Baets
et al. 2021b; Kraemer et al. 2018), which provides an incomplete picture of the
range of interactions which existed in a given palaeoenvironment. For coprolites,
given the range of palaeoecology information that can be derived from studying the
coprolites of vertebrates (Chin 2002, 2021; Bajdek et al. 2016), it would be advisable for researchers to also be on the lookout for fossils of parasite propagules while
investigating such material.
1.4 Future Research Directions and Further Questions
Fossils can provide vital insights into the evolution of parasitism (De Baets and
Littlewood 2015; De Baets et al. 2021b). Based on molecular phylogeny and
fossils of parasites, it seems that major events in the history of parasite groups
were often associated with diversification and extinction events of their vertebrate host taxa. Future fossil discoveries can address some key questions about
evolution of parasites which are found on vertebrate hosts, and can in turn be
used to help calibrate molecular studies on the phylogeny of various parasite
groups. Many different taxa have independently evolved some kind of parasitic
life style and often the parasitic representatives have heavily derived morphology that differ very significantly from their closest living non-parasitic relatives.
Fossil parasites might provide insight into the transition between free-living and
parasitism, both in terms of changes in their morphology and pattern of host or
resource usage.
There are some fossil parasites that were discovered or described incidentally
such as the case of Zangerl and Case (1976), where microfossils of what appears to
be cestode eggs were found amidst the coprolitic material associated with the lower
intestinal tract of a Carboniferous elasmobranch. Re-examination of older specimens using more recent technology such as microCT scans and other techniques
(e.g., Maas 2013) may yield further discoveries. At the same time, microfossils of
parasite materials such as helminth eggs or monogenean hooks may become inadvertently dislodged or destroyed during some preparation processes, thus any prospective palaeoparasitologists should make use of preparation and analysis methods
that minimise disruption of the original material.
When examining, describing, and identifying potential fossil parasites, the
study by Poinar et al. (2017) on the trematode metacercaria embedded in the leg
of an amber-preserved lizard can be considered as an example of “best practice”. The fossil they described was of the type of deposit/material (in this case,
T. L. F. Leung
whether they be in amber, coprolite, or compression fossils. Amber is an exceptional material that can preserve many organisms intact and in some cases, in their
original ecological context (Poinar 1992), including some parasite-host relationships as shown through the examples discussed in this chapter. However, researchers must be mindful that amber is subjected to preservation biases (e.g. De Baets
et al. 2021b; Kraemer et al. 2018), which provides an incomplete picture of the
range of interactions which existed in a given palaeoenvironment. For coprolites,
given the range of palaeoecology information that can be derived from studying the
coprolites of vertebrates (Chin 2002, 2021; Bajdek et al. 2016), it would be advisable for researchers to also be on the lookout for fossils of parasite propagules while
investigating such material.
1.4 Future Research Directions and Further Questions
Fossils can provide vital insights into the evolution of parasitism (De Baets and
Littlewood 2015; De Baets et al. 2021b). Based on molecular phylogeny and
fossils of parasites, it seems that major events in the history of parasite groups
were often associated with diversification and extinction events of their vertebrate host taxa. Future fossil discoveries can address some key questions about
evolution of parasites which are found on vertebrate hosts, and can in turn be
used to help calibrate molecular studies on the phylogeny of various parasite
groups. Many different taxa have independently evolved some kind of parasitic
life style and often the parasitic representatives have heavily derived morphology that differ very significantly from their closest living non-parasitic relatives.
Fossil parasites might provide insight into the transition between free-living and
parasitism, both in terms of changes in their morphology and pattern of host or
resource usage.
There are some fossil parasites that were discovered or described incidentally
such as the case of Zangerl and Case (1976), where microfossils of what appears to
be cestode eggs were found amidst the coprolitic material associated with the lower
intestinal tract of a Carboniferous elasmobranch. Re-examination of older specimens using more recent technology such as microCT scans and other techniques
(e.g., Maas 2013) may yield further discoveries. At the same time, microfossils of
parasite materials such as helminth eggs or monogenean hooks may become inadvertently dislodged or destroyed during some preparation processes, thus any prospective palaeoparasitologists should make use of preparation and analysis methods
that minimise disruption of the original material.
When examining, describing, and identifying potential fossil parasites, the
study by Poinar et al. (2017) on the trematode metacercaria embedded in the leg
of an amber-preserved lizard can be considered as an example of “best practice”. The fossil they described was of the type of deposit/material (in this case,
T. L. F. Leung