251
et al. 1994) and the Late Cretaceous Palaeoenoploides alessandrellianus (Mattavelli
and Bracchi 2008). These have been assigned to their own families (Eophasmidae,
Captivonematidae, Palaeoenoploididae) which in turn have been attributed to modern orders (Desmoscolecida, Plectida and Enoplida, respectively; Poinar 2011).
However, their assignment to modern lineages (Poinar 2011) is based on limited and
possibly plesiomorphic traits (e.g., small size, finely annulated cuticle and dense
coating of prominent irregularly distributed setae in Captivonema; coarsely annulated cuticle in Eophasma). The second oldest fossil attributed to the order Plectida
is Oligoplectus succini derived from Baltic amber (Poinar 2014).
The oldest confidently identified nematode body fossils derives from the Early
Devonian (Poinar et al. 2008; Maas 2013). These specimens are associated with the
early land plant, Aglaophyton major, and are considered the earliest evidence for
plant parasitic nematodes (Poinar 2011, 2015). The fossils placed in their own family (Paleonematidae) have also been assigned tentatively to Enoplida.
Node. Crown-group Nematoda
Fossil Taxon. Palaeonema phyticum
Fossil Evidence. Up to 500 nematodes and eggs from substomatal chambers and
intercellular spaces of early land plants (Poinar et al. 2008).
Host. Aglaophyton major
Phylogenetic justification. The body fossils are well-preserved revealing fine morphological details such as buccal cavity, surface ornamentation, pharynx, ovaries,
tail and various other features (Poinar et al. 2008) which allows them to be placed
unequivocally within Nematoda (Maas 2013). They were assigned to their own
family based on the presence of transverse cuticular striations and structure of
pharynx and buccal cavity, but could be assigned tentatively to Enoplia (Enoplida
according to Poinar 2011) due to inconspicuous lips, a buccal cavity divided in
two sections, presence of teeth (two visible, probably three) in the buccal cavity,
didelphic and reflexed ovaries, spiral amphidial apertures and a cylindrical pharynx it shares with members of Tripyloididae (Poinar et al. 2008).
Minimum age. 407.6 Ma. The relationship of the radiometric dating of the Milton
of Noth Andesite (Parry et al. 2011) with the Rhynie chert is still disputed (Mark
et al. 2013; Parry et al. 2013). Therefore, it is more conservative to use the age of
the Pragian-Emsian boundary (407.6 Ma according to GTS 2016: Ogg et al.
2016) based on the constraints of spore assemblages of Windyfield and stratigraphically underlying Rhynie chert (Parry et al. 2011).
Burmese amber provides the first evidence for mycetophagous nematodes in the
form of fungal-feeding Cretaciaphelenchoides burmensis which Poinar (2011)
assigned to the Aphelenchoididae; this is also considered the oldest evidence for the
order Tylenchomorpha in the fossil record (Poinar 2015).
Node. Tylenchomorpha
Fossil Taxon. Cretaciaphelenchoides burmensis
Fossil evidence. Worm body associated with host in Burmese amber (Poinar 2011)
Host. Crane fly (Gonomyia)
7 Fossil Constraints on the Timescale of Parasitic Helminth Evolution
et al. 1994) and the Late Cretaceous Palaeoenoploides alessandrellianus (Mattavelli
and Bracchi 2008). These have been assigned to their own families (Eophasmidae,
Captivonematidae, Palaeoenoploididae) which in turn have been attributed to modern orders (Desmoscolecida, Plectida and Enoplida, respectively; Poinar 2011).
However, their assignment to modern lineages (Poinar 2011) is based on limited and
possibly plesiomorphic traits (e.g., small size, finely annulated cuticle and dense
coating of prominent irregularly distributed setae in Captivonema; coarsely annulated cuticle in Eophasma). The second oldest fossil attributed to the order Plectida
is Oligoplectus succini derived from Baltic amber (Poinar 2014).
The oldest confidently identified nematode body fossils derives from the Early
Devonian (Poinar et al. 2008; Maas 2013). These specimens are associated with the
early land plant, Aglaophyton major, and are considered the earliest evidence for
plant parasitic nematodes (Poinar 2011, 2015). The fossils placed in their own family (Paleonematidae) have also been assigned tentatively to Enoplida.
Node. Crown-group Nematoda
Fossil Taxon. Palaeonema phyticum
Fossil Evidence. Up to 500 nematodes and eggs from substomatal chambers and
intercellular spaces of early land plants (Poinar et al. 2008).
Host. Aglaophyton major
Phylogenetic justification. The body fossils are well-preserved revealing fine morphological details such as buccal cavity, surface ornamentation, pharynx, ovaries,
tail and various other features (Poinar et al. 2008) which allows them to be placed
unequivocally within Nematoda (Maas 2013). They were assigned to their own
family based on the presence of transverse cuticular striations and structure of
pharynx and buccal cavity, but could be assigned tentatively to Enoplia (Enoplida
according to Poinar 2011) due to inconspicuous lips, a buccal cavity divided in
two sections, presence of teeth (two visible, probably three) in the buccal cavity,
didelphic and reflexed ovaries, spiral amphidial apertures and a cylindrical pharynx it shares with members of Tripyloididae (Poinar et al. 2008).
Minimum age. 407.6 Ma. The relationship of the radiometric dating of the Milton
of Noth Andesite (Parry et al. 2011) with the Rhynie chert is still disputed (Mark
et al. 2013; Parry et al. 2013). Therefore, it is more conservative to use the age of
the Pragian-Emsian boundary (407.6 Ma according to GTS 2016: Ogg et al.
2016) based on the constraints of spore assemblages of Windyfield and stratigraphically underlying Rhynie chert (Parry et al. 2011).
Burmese amber provides the first evidence for mycetophagous nematodes in the
form of fungal-feeding Cretaciaphelenchoides burmensis which Poinar (2011)
assigned to the Aphelenchoididae; this is also considered the oldest evidence for the
order Tylenchomorpha in the fossil record (Poinar 2015).
Node. Tylenchomorpha
Fossil Taxon. Cretaciaphelenchoides burmensis
Fossil evidence. Worm body associated with host in Burmese amber (Poinar 2011)
Host. Crane fly (Gonomyia)
7 Fossil Constraints on the Timescale of Parasitic Helminth Evolution