243
Node. Spionidae
Phylogenetic justification. Cameron (1967) interpreted external structures such as
a prostomium, anterior tentacle-like palps, peristomial cirri, parapodia, and dorsal cirri of the parapodia. Its habit together with its residence within a bivalve
shell would speak for its assignment to the Spionidae. Nevertheless, the worm is
not associated with a U-tube or mud blister attributed to be characteristic for in
situ damage of most of this group (Blake and Evans 1973; Huntley 2007).
Host. Bivalve Cornellites flabellum
Min age. The fossil assemblage derive from a small quarry north of Morrisville
where the middle part of the Cardiff shale member of the marine Marcellus
Formation is exposed (Cameron 1967). This member correlates with the upper
part of the Marcellus Formation (Oatna Creek Member) at other localities which
are considered to represent the upper part of the hemisiatus conodont zone of the
Givetian (Brett et al. 2011). The upper boundary of the zone would yield a minimum age of 387.3 Ma according to GTS 2016 (Ogg et al. 2016).
Clitellata can be confidently traced back to the Triassic based on characteristic
cocoons (Manum et al.1991, 1994; Bomfleur et al. 2012, 2015; McLoughlin et al.
2016). The most likely producers of these cocoons are considered true leeches and
branchiobdellids (Manum et al. 1991; Bomfleur et al. 2015). Clitellate cocoons
sometimes function as conservation traps for other remains including nematodes or
ciliates (Bomfleur et al. 2015; McLoughlin et al. 2016). In one case, they contain
spermatozoa, which suggest branchiobdellids could have produced these coccoons
at least since the Eocene and that this group had a significantly different geographic
range in the past. This group is usually considered as ectoparasitic of, or at least
ectosymbiotic with, crayfish—although they show a variety of relationships ranging
from symbiotic, commensal to parasitic (Skelton et al. 2013). More precise evidence is necessary to tie older Triassic cocoons to Branchiobdellids as they could
also belong to Euhirudinae (Hirudinida: compare Tessler et al. 2018). True leeches
might occur in the Upper Jurassic (Kozur 1970), but this specimen is rather considered a carnivorous then a parasitic species.
Node. Total group Hirudinae
Phylogenetic justification. Characteristic cocoons are only produced by true
leeches (Euhirudinae) and branchiobdellids. They may also provide the oldest
evidence for clitellata as a whole (Parry et al. 2014), but a putative oligochaete
has recently been described from the Lower Triassic (Shcherbakov et al. 2020).
Min age. 201.4 Ma. The earliest finds are attributed to the Rhaetian (Manum et al.
1991; Bomfleur et al. 2015) which would yield a minimum age for this group of
201.4 Ma according to GTS 2016 (Ogg et al. 2016).
Node. Total group Branchiobdellida
Host. Unknown, but modern representatives are mostly leech-like ectoparasites of
crayfish (Govedich et al. 2010).
Phylogenetic justification. Annelid sperm described from inclusions in cocoons
from the Eocene of Antarctica possess characteristic elongate acrosomes and
7 Fossil Constraints on the Timescale of Parasitic Helminth Evolution
Node. Spionidae
Phylogenetic justification. Cameron (1967) interpreted external structures such as
a prostomium, anterior tentacle-like palps, peristomial cirri, parapodia, and dorsal cirri of the parapodia. Its habit together with its residence within a bivalve
shell would speak for its assignment to the Spionidae. Nevertheless, the worm is
not associated with a U-tube or mud blister attributed to be characteristic for in
situ damage of most of this group (Blake and Evans 1973; Huntley 2007).
Host. Bivalve Cornellites flabellum
Min age. The fossil assemblage derive from a small quarry north of Morrisville
where the middle part of the Cardiff shale member of the marine Marcellus
Formation is exposed (Cameron 1967). This member correlates with the upper
part of the Marcellus Formation (Oatna Creek Member) at other localities which
are considered to represent the upper part of the hemisiatus conodont zone of the
Givetian (Brett et al. 2011). The upper boundary of the zone would yield a minimum age of 387.3 Ma according to GTS 2016 (Ogg et al. 2016).
Clitellata can be confidently traced back to the Triassic based on characteristic
cocoons (Manum et al.1991, 1994; Bomfleur et al. 2012, 2015; McLoughlin et al.
2016). The most likely producers of these cocoons are considered true leeches and
branchiobdellids (Manum et al. 1991; Bomfleur et al. 2015). Clitellate cocoons
sometimes function as conservation traps for other remains including nematodes or
ciliates (Bomfleur et al. 2015; McLoughlin et al. 2016). In one case, they contain
spermatozoa, which suggest branchiobdellids could have produced these coccoons
at least since the Eocene and that this group had a significantly different geographic
range in the past. This group is usually considered as ectoparasitic of, or at least
ectosymbiotic with, crayfish—although they show a variety of relationships ranging
from symbiotic, commensal to parasitic (Skelton et al. 2013). More precise evidence is necessary to tie older Triassic cocoons to Branchiobdellids as they could
also belong to Euhirudinae (Hirudinida: compare Tessler et al. 2018). True leeches
might occur in the Upper Jurassic (Kozur 1970), but this specimen is rather considered a carnivorous then a parasitic species.
Node. Total group Hirudinae
Phylogenetic justification. Characteristic cocoons are only produced by true
leeches (Euhirudinae) and branchiobdellids. They may also provide the oldest
evidence for clitellata as a whole (Parry et al. 2014), but a putative oligochaete
has recently been described from the Lower Triassic (Shcherbakov et al. 2020).
Min age. 201.4 Ma. The earliest finds are attributed to the Rhaetian (Manum et al.
1991; Bomfleur et al. 2015) which would yield a minimum age for this group of
201.4 Ma according to GTS 2016 (Ogg et al. 2016).
Node. Total group Branchiobdellida
Host. Unknown, but modern representatives are mostly leech-like ectoparasites of
crayfish (Govedich et al. 2010).
Phylogenetic justification. Annelid sperm described from inclusions in cocoons
from the Eocene of Antarctica possess characteristic elongate acrosomes and
7 Fossil Constraints on the Timescale of Parasitic Helminth Evolution