2
parasites, both on their external surfaces as well as their various internal organs and
tissues. These parasites vary in their taxonomy, life-cycle, infection site, and the
effects that they have on their hosts. Many parasites are specialised to live on a specific part of the host’s body, and the body of a vertebrate animal can be thought of
as a collection of microhabitats, each inhabited by one or more specific parasite
species (Loker and Hofkin 2015).
Despite their abundance in many extant ecosystems, parasites are exceedingly
rare in the fossil record as most parasites are not conducive to being preserved as
fossils. Many of them are small and have soft bodies, or do not leave traces of their
presences on the host tissue in a way which will be fossilised (De Baets et al. 2021b).
Additionally, most palaeontological studies are not focused on looking for traces of
parasitism, so it is also possible that many fossil parasites are being overlooked
(Littlewood and Donovan 2003). As such, little is known about the effects they have
on their hosts or the ecological roles they played in various palaeoenvironments.
However, there are a small collection of studies which have found evidence of parasites from fossil vertebrates (Boucot and Poinar 2011; De Baets and Littlewood
2015; Leung 2017). These studies provide vital glimpses into the evolution of parasitism throughout Earth’s history.
The potential for detecting the signs of parasitism or parasites themselves in fossil samples has increased in recent years with technology such as computed tomography which allows well-preserved specimens to be examined for finer, microscopic
details (e.g. Siveter et al. 2015; Robin et al. 2016; Poinar et al. 2017; Peñalver et al.
2017). However, an important step in furthering the study of fossil parasites is for
palaeontologists to be aware of and recognise the potential for fossilised parasites.
As such, any prospective palaeoparasitologists needs to be aware of what to expect
and what to look for when it comes to potential fossil parasites. Since vertebrate
taxa have relatively large body sizes and are host to a variety of different parasites,
fossil vertebrates and their associated remains are great potential sources of parasite
fossils. So how would a prospective parasite palaeontologist know what to look for
when it comes to fossil parasites? How can they recognise a parasite when they see
one? This is where having a general idea of the likely parasite community of a given
fossil vertebrate taxa would be helpful, and there are methods for inferring potential
parasites of extinct vertebrate taxa and anticipate their association with wellpreserved vertebrate fossils.
The aim of this chapter is to provide an overview of vertebrate-infecting parasites which have been described from the fossil record, how they compare with their
equivalents found in extant vertebrates, and how we can combine concepts and techniques from palaeontology and ecological parasitology to further develop research
into this field. This chapter will be covering the types of macroparasites which have
been found from fossil vertebrates that are pre-Pleistocene in age. For each group, I
will provide (1) some background on the biology and ecology of their extant taxa,
(2) what groups can be expected to host such parasites, (3) what types of fossils can
be expect from such parasites, and (4) future research directions.
T. L. F. Leung
parasites, both on their external surfaces as well as their various internal organs and
tissues. These parasites vary in their taxonomy, life-cycle, infection site, and the
effects that they have on their hosts. Many parasites are specialised to live on a specific part of the host’s body, and the body of a vertebrate animal can be thought of
as a collection of microhabitats, each inhabited by one or more specific parasite
species (Loker and Hofkin 2015).
Despite their abundance in many extant ecosystems, parasites are exceedingly
rare in the fossil record as most parasites are not conducive to being preserved as
fossils. Many of them are small and have soft bodies, or do not leave traces of their
presences on the host tissue in a way which will be fossilised (De Baets et al. 2021b).
Additionally, most palaeontological studies are not focused on looking for traces of
parasitism, so it is also possible that many fossil parasites are being overlooked
(Littlewood and Donovan 2003). As such, little is known about the effects they have
on their hosts or the ecological roles they played in various palaeoenvironments.
However, there are a small collection of studies which have found evidence of parasites from fossil vertebrates (Boucot and Poinar 2011; De Baets and Littlewood
2015; Leung 2017). These studies provide vital glimpses into the evolution of parasitism throughout Earth’s history.
The potential for detecting the signs of parasitism or parasites themselves in fossil samples has increased in recent years with technology such as computed tomography which allows well-preserved specimens to be examined for finer, microscopic
details (e.g. Siveter et al. 2015; Robin et al. 2016; Poinar et al. 2017; Peñalver et al.
2017). However, an important step in furthering the study of fossil parasites is for
palaeontologists to be aware of and recognise the potential for fossilised parasites.
As such, any prospective palaeoparasitologists needs to be aware of what to expect
and what to look for when it comes to potential fossil parasites. Since vertebrate
taxa have relatively large body sizes and are host to a variety of different parasites,
fossil vertebrates and their associated remains are great potential sources of parasite
fossils. So how would a prospective parasite palaeontologist know what to look for
when it comes to fossil parasites? How can they recognise a parasite when they see
one? This is where having a general idea of the likely parasite community of a given
fossil vertebrate taxa would be helpful, and there are methods for inferring potential
parasites of extinct vertebrate taxa and anticipate their association with wellpreserved vertebrate fossils.
The aim of this chapter is to provide an overview of vertebrate-infecting parasites which have been described from the fossil record, how they compare with their
equivalents found in extant vertebrates, and how we can combine concepts and techniques from palaeontology and ecological parasitology to further develop research
into this field. This chapter will be covering the types of macroparasites which have
been found from fossil vertebrates that are pre-Pleistocene in age. For each group, I
will provide (1) some background on the biology and ecology of their extant taxa,
(2) what groups can be expected to host such parasites, (3) what types of fossils can
be expect from such parasites, and (4) future research directions.
T. L. F. Leung