256
free-living and lineages parasitizing arthropods similar to nematomorphs like
mermithidae are derived (Blaxter and Koutsovoulos 2015). This suggests stemnematomorphs were likely free-living and may have looked quite different from
crown-group nematomorphs.
The diversity of Cycloneuralia in the Cambrian fossil record might suggest an
even earlier origin (Maas 2013). Some free-living forms of Palaeoscolecidae even
closely resemble some Nematomorpha (Hou and Bergström 1994), but they are
usually interpreted as being early offshoots of the lineage towards Priapulida
(Harvey et al. 2010). Shergoldana australensis from the Cambrian of Queensland
resembles nematomorph larvae to some degree (Maas et al. 2007), and probably
also lived in the meiofauna, similar to kinorhynch cycloneuralians (Nagler and
Haug 2015).
The oldest constraints on the origin of Ecdysozoa are arthropod trace fossils
from the Cambrian (Benton et al. 2015).
Node. Gordioida
Fossil Taxon. Cretachordodes burmitis
Fossil evidence. Isolated body fossil (Poinar and Buckley 2006)
Fossil Host. Unknown—possibly a cockroach based on circumstantial evidence
(Poinar and Buckley 2006).
Phylogenetic Justification. No formal phylogenetic analysis has been performed,
but surface ornamentation, dimensions, characteristic coiling after death speak
for the assignment of these body fossils to Chordodidae (Gordioidea, Gordioida)
(Poinar and Buckley 2006).
Minimum age. 98.17 Ma. See Tylenchomorpha (Nematoda) for justification.
7.4.6 Fossil Record of Syndermata
Weinstein and Kuris (2016) considered that parasitism might have evolved at
least nine times independently in Rotifera (= Syndermata). However, earlier
reports (May 1989) considered the ectoparasitic Seison and Acanthocephala to
be independent transitions which is probably not the case (Sielaff et al. 2016).
The fossil record of Pararotatoria (Acanthocephala + Seisonidae), which are
now considered derived rotifers (syndermatans), is rare. Until recently, the
oldest fossil constraint for their presence was that of their close relatives—
bdelloid rotifers in Dominican amber (Waggoner and Poinar 1993; Poinar and
Ricci 1992). Other more distant relatives have become known from Eocene
non-marine deposits in South Australia (Southcott and Lange 1971).
Dominican amber has traditionally been dated from the Eocene to Oligocene,
but is currently attributed to the Miocene (Iturralde-Vinent and MacPhee
1996; Iturralde-Vinent 2001). New discoveries of acanthocephalan eggs from
Upper Cretaceous crocodile coprolites push back this record considerably
(Cardia et al. 2019a). However, estimates based on host relationships might
K. De Baets et al.
free-living and lineages parasitizing arthropods similar to nematomorphs like
mermithidae are derived (Blaxter and Koutsovoulos 2015). This suggests stemnematomorphs were likely free-living and may have looked quite different from
crown-group nematomorphs.
The diversity of Cycloneuralia in the Cambrian fossil record might suggest an
even earlier origin (Maas 2013). Some free-living forms of Palaeoscolecidae even
closely resemble some Nematomorpha (Hou and Bergström 1994), but they are
usually interpreted as being early offshoots of the lineage towards Priapulida
(Harvey et al. 2010). Shergoldana australensis from the Cambrian of Queensland
resembles nematomorph larvae to some degree (Maas et al. 2007), and probably
also lived in the meiofauna, similar to kinorhynch cycloneuralians (Nagler and
Haug 2015).
The oldest constraints on the origin of Ecdysozoa are arthropod trace fossils
from the Cambrian (Benton et al. 2015).
Node. Gordioida
Fossil Taxon. Cretachordodes burmitis
Fossil evidence. Isolated body fossil (Poinar and Buckley 2006)
Fossil Host. Unknown—possibly a cockroach based on circumstantial evidence
(Poinar and Buckley 2006).
Phylogenetic Justification. No formal phylogenetic analysis has been performed,
but surface ornamentation, dimensions, characteristic coiling after death speak
for the assignment of these body fossils to Chordodidae (Gordioidea, Gordioida)
(Poinar and Buckley 2006).
Minimum age. 98.17 Ma. See Tylenchomorpha (Nematoda) for justification.
7.4.6 Fossil Record of Syndermata
Weinstein and Kuris (2016) considered that parasitism might have evolved at
least nine times independently in Rotifera (= Syndermata). However, earlier
reports (May 1989) considered the ectoparasitic Seison and Acanthocephala to
be independent transitions which is probably not the case (Sielaff et al. 2016).
The fossil record of Pararotatoria (Acanthocephala + Seisonidae), which are
now considered derived rotifers (syndermatans), is rare. Until recently, the
oldest fossil constraint for their presence was that of their close relatives—
bdelloid rotifers in Dominican amber (Waggoner and Poinar 1993; Poinar and
Ricci 1992). Other more distant relatives have become known from Eocene
non-marine deposits in South Australia (Southcott and Lange 1971).
Dominican amber has traditionally been dated from the Eocene to Oligocene,
but is currently attributed to the Miocene (Iturralde-Vinent and MacPhee
1996; Iturralde-Vinent 2001). New discoveries of acanthocephalan eggs from
Upper Cretaceous crocodile coprolites push back this record considerably
(Cardia et al. 2019a). However, estimates based on host relationships might
K. De Baets et al.