354
The first fossil representatives of Cymothoida are generally attributed to
Cirolanidae from the Permian (290 mya) in Brazil (Martins-Neto 2001). Given this
ancestral type of life style and no well formulated apomorphies, the group might
turn out as paraphyletic. Fossil cirolanid-type fossils have been found scavenging
on whales, fishes and water bugs (Wilson et al. 2011; Pasini and Garassino 2012;
Hyžný et al. 2013).
Within the remaining group of Cymothoida (excluding the cirolanid-like forms)
molecular and morphological data support a sistergroup relationship of Corallanidae
to all other parasitic representatives of Cymothoida (Wägele 1989; Dreyer and
Wägele 2001; Brandt and Poore 2003; Wetzer et al. 2013; Hata et al. 2017; Nagler
et al. 2017a). Some (modern) representatives of Corallanidae are scavengers and
predators. Yet, they possess already longer, thinner and more pointed mouthparts
typical for parasites than do representatives of Cirolanidae (Bruce 1986; Bruce et al.
1982; Bunkley-Williams and Williams 1998). Also, some representatives are known
to act as temporary parasites (see Nagler et al. 2017a and references therein).
However, the group might as well be paraphyletic, or otherwise some representatives of the group have evolved temporary parasitism independently.
Aegidae is usually interpreted as the sistergroup to all other remaining parasitic
representatives of Cymothoida (Brusca and Wilson 1991; Wilson 2009; Hadfield
2012; Nagler et al. 2017a). Yet, also this group has been suggested to be paraphyletic (Wägele 1989).
The sister group to Aegidae, with all the permanently attached isopodan parasites
has been suggested to have arisen in the Early Jurassic (180 mya) in the deep sea
(Schram 1977; Brusca 1981; Brandt and Poore 2003; Smit et al. 2014; Nagler et al.
2016; Hata et al. 2017). Within this group, Cymothoidae is sister group to all the
remaining ones. Cymothoiids seem to have expanded their habitats to shallower
seas and also brackish or freshwater by shifting their fish host species at the latest in
the Late Jurassic (150 mya; Nagler et al. 2016; Hata et al. 2017).
The sister group to Cymothoidae includes three groups with unresolved relationships among them. Epicaridea has been considered to represent the direct sister
group to Cymothoidae by many authors (see discussion in Nagler et al. 2017a), but
Gnathiidae also shares many characters with Epicaridea, hence very likely representing also an ingroup of Cymothoida, closer related to Epicaridea. This relationship has been disputed by many authors (see discussion in Nagler et al. 2017a) as
only the larval forms exhibit the shared characters of Gnathiidae and Epicaridea,
while adults have a derived biology and morphology. Yet, as the group Thecostraca
(sensu lato) demonstrates larval characters can be of prime importance to deduce
evolutionary relationships especially in lineages with parasitic forms (see further
below). The third group in the sister group to Cymothoidae is an exclusively fossil
one, Urda. More precisely, at least one representative of the group could be identified as a parasite based on functional morphology (Fig. 10.2b). It represents the
oldest indication for parasitism within Cymothoida, to the best of our knowledge,
back in the Jurassic (168 mya; Nagler et al. 2017a). Sharing morphological characters with modern representatives of Cymothoidae (plesiomorphic features) and
Gnathiidae, it seems that Urda is either closely related to Gnathiidae + Epicaridea
J. T. Haug et al.
The first fossil representatives of Cymothoida are generally attributed to
Cirolanidae from the Permian (290 mya) in Brazil (Martins-Neto 2001). Given this
ancestral type of life style and no well formulated apomorphies, the group might
turn out as paraphyletic. Fossil cirolanid-type fossils have been found scavenging
on whales, fishes and water bugs (Wilson et al. 2011; Pasini and Garassino 2012;
Hyžný et al. 2013).
Within the remaining group of Cymothoida (excluding the cirolanid-like forms)
molecular and morphological data support a sistergroup relationship of Corallanidae
to all other parasitic representatives of Cymothoida (Wägele 1989; Dreyer and
Wägele 2001; Brandt and Poore 2003; Wetzer et al. 2013; Hata et al. 2017; Nagler
et al. 2017a). Some (modern) representatives of Corallanidae are scavengers and
predators. Yet, they possess already longer, thinner and more pointed mouthparts
typical for parasites than do representatives of Cirolanidae (Bruce 1986; Bruce et al.
1982; Bunkley-Williams and Williams 1998). Also, some representatives are known
to act as temporary parasites (see Nagler et al. 2017a and references therein).
However, the group might as well be paraphyletic, or otherwise some representatives of the group have evolved temporary parasitism independently.
Aegidae is usually interpreted as the sistergroup to all other remaining parasitic
representatives of Cymothoida (Brusca and Wilson 1991; Wilson 2009; Hadfield
2012; Nagler et al. 2017a). Yet, also this group has been suggested to be paraphyletic (Wägele 1989).
The sister group to Aegidae, with all the permanently attached isopodan parasites
has been suggested to have arisen in the Early Jurassic (180 mya) in the deep sea
(Schram 1977; Brusca 1981; Brandt and Poore 2003; Smit et al. 2014; Nagler et al.
2016; Hata et al. 2017). Within this group, Cymothoidae is sister group to all the
remaining ones. Cymothoiids seem to have expanded their habitats to shallower
seas and also brackish or freshwater by shifting their fish host species at the latest in
the Late Jurassic (150 mya; Nagler et al. 2016; Hata et al. 2017).
The sister group to Cymothoidae includes three groups with unresolved relationships among them. Epicaridea has been considered to represent the direct sister
group to Cymothoidae by many authors (see discussion in Nagler et al. 2017a), but
Gnathiidae also shares many characters with Epicaridea, hence very likely representing also an ingroup of Cymothoida, closer related to Epicaridea. This relationship has been disputed by many authors (see discussion in Nagler et al. 2017a) as
only the larval forms exhibit the shared characters of Gnathiidae and Epicaridea,
while adults have a derived biology and morphology. Yet, as the group Thecostraca
(sensu lato) demonstrates larval characters can be of prime importance to deduce
evolutionary relationships especially in lineages with parasitic forms (see further
below). The third group in the sister group to Cymothoidae is an exclusively fossil
one, Urda. More precisely, at least one representative of the group could be identified as a parasite based on functional morphology (Fig. 10.2b). It represents the
oldest indication for parasitism within Cymothoida, to the best of our knowledge,
back in the Jurassic (168 mya; Nagler et al. 2017a). Sharing morphological characters with modern representatives of Cymothoidae (plesiomorphic features) and
Gnathiidae, it seems that Urda is either closely related to Gnathiidae + Epicaridea
J. T. Haug et al.