331
parasitise mammals, such that this fossil nymph may be among the oldest examples of a mammalian ectoparasite.
4. The oldest soft tick (Argasidae) comes from the Cretaceous (ca. 90–94 Ma) New
Jersey amber (Klompen and Grimaldi 2001). This larval specimen was described
in the extant genus Carios, although this is usually subsumed under the genus
Ornithodoros now. Klompen and Grimaldi (2001) noted that most ticks originally
assigned to Carios were bat parasites, although bats had probably not evolved by
that time. Birds, or even pterosaurs, as possible alternative hosts were discussed.
An undescribed, bloated tick from Burmese amber figured as an argasid was
figured by Shi et al. (2012), although it likely belongs to a different tick group.
5. Eocene (ca. 49 Ma) Baltic amber has yielded the oldest record of the extant
genus Ixodes (Fig. 9.5f). First described by Weidner (1964), it was redescribed
with the help of computed tomography by Dunlop et al. (2016), who determined
that it is not closely related to the modern sheep tick Ixodes ricinus as originally
thought, but is instead closer to the Asian species Ixodes ovatus. These authors
also discussed molecular estimates for when tick-borne pathogens are thought to
have appeared compared to the fossil record of the ticks that may have carried
them. A putative Baltic amber record of another extant hard tick genus,
Hyalomma, figured in de la Fuente (2003) is probably a misidentified, and nonparasitic, caeculid mite (Chitimia-Dobler et al. 2017), but see Estrada Peña and
de la Fuente (2018) for a rebuttal. A contemporary non-amber record from the
Eocene Green River Formation of the USA (Scudder 1885) is a nomen dubium,
and probably not even a tick (Dunlop 2011).
6. Miocene (ca. 16 Ma) Dominican Republic amber hosts records of the soft tick
Ornithodoros Fig. 9.5g) described by Poinar Jr (1995) as well as several records
of the hard tick Amblyomma which appear to be very close to living Neotropical
species (Lane and Poinar Jr 1986; Keirans et al. 2002). Spirochete-like cells were
reported by Poinar Jr (2015b) from the body cavity of some of these Amblyomma
inclusions.
7. There are two subfossil records of living hard tick species, namely a Dermacentor
from the ear of a fossil rhinoceros (Kulczyński in Schille 1916) and an Ixodes
discovered in an owl pellet (Sanchez et al. 2010).
9.4.2.4 Mesostigmatids
Mesostigmatids—sometimes referred to as gamasid mites—are a diverse assemblage with around 11,400 extant species. They are sometimes referred to as predatory mites, but this conceals a range of lifestyles from free-living predators of
nematode worms or microarthropods, to animals which feed on fungi, pollen or
nectar and, of course, several parasites (Table 9.1). It should be noted that the feeding ecology remains equivocal for a number of groups. Many mesostigmatids are
found in association with insects or vertebrates, often with phoretic relationships
(see also Sect. 9.5). Note that the family Parasitidae was created for non-parasitic
species (e.g. Elbardy 1972) which were initially assumed to be parasites since they
9 Chelicerates as Parasites
parasitise mammals, such that this fossil nymph may be among the oldest examples of a mammalian ectoparasite.
4. The oldest soft tick (Argasidae) comes from the Cretaceous (ca. 90–94 Ma) New
Jersey amber (Klompen and Grimaldi 2001). This larval specimen was described
in the extant genus Carios, although this is usually subsumed under the genus
Ornithodoros now. Klompen and Grimaldi (2001) noted that most ticks originally
assigned to Carios were bat parasites, although bats had probably not evolved by
that time. Birds, or even pterosaurs, as possible alternative hosts were discussed.
An undescribed, bloated tick from Burmese amber figured as an argasid was
figured by Shi et al. (2012), although it likely belongs to a different tick group.
5. Eocene (ca. 49 Ma) Baltic amber has yielded the oldest record of the extant
genus Ixodes (Fig. 9.5f). First described by Weidner (1964), it was redescribed
with the help of computed tomography by Dunlop et al. (2016), who determined
that it is not closely related to the modern sheep tick Ixodes ricinus as originally
thought, but is instead closer to the Asian species Ixodes ovatus. These authors
also discussed molecular estimates for when tick-borne pathogens are thought to
have appeared compared to the fossil record of the ticks that may have carried
them. A putative Baltic amber record of another extant hard tick genus,
Hyalomma, figured in de la Fuente (2003) is probably a misidentified, and nonparasitic, caeculid mite (Chitimia-Dobler et al. 2017), but see Estrada Peña and
de la Fuente (2018) for a rebuttal. A contemporary non-amber record from the
Eocene Green River Formation of the USA (Scudder 1885) is a nomen dubium,
and probably not even a tick (Dunlop 2011).
6. Miocene (ca. 16 Ma) Dominican Republic amber hosts records of the soft tick
Ornithodoros Fig. 9.5g) described by Poinar Jr (1995) as well as several records
of the hard tick Amblyomma which appear to be very close to living Neotropical
species (Lane and Poinar Jr 1986; Keirans et al. 2002). Spirochete-like cells were
reported by Poinar Jr (2015b) from the body cavity of some of these Amblyomma
inclusions.
7. There are two subfossil records of living hard tick species, namely a Dermacentor
from the ear of a fossil rhinoceros (Kulczyński in Schille 1916) and an Ixodes
discovered in an owl pellet (Sanchez et al. 2010).
9.4.2.4 Mesostigmatids
Mesostigmatids—sometimes referred to as gamasid mites—are a diverse assemblage with around 11,400 extant species. They are sometimes referred to as predatory mites, but this conceals a range of lifestyles from free-living predators of
nematode worms or microarthropods, to animals which feed on fungi, pollen or
nectar and, of course, several parasites (Table 9.1). It should be noted that the feeding ecology remains equivocal for a number of groups. Many mesostigmatids are
found in association with insects or vertebrates, often with phoretic relationships
(see also Sect. 9.5). Note that the family Parasitidae was created for non-parasitic
species (e.g. Elbardy 1972) which were initially assumed to be parasites since they
9 Chelicerates as Parasites