253
Minimum age. 236 Ma. See Ascaridomorpha.
Based on modern host associations and fossil record, oxyurids might have parasitized invertebrates before vertebrates (Poinar 2015). The oldest direct evidence for
oxyurids parasitizing invertebrates, however, is Paleothelastoma tipulae found
associated with the crane fly Gonomyia found in Burmese Amber (Poinar 2011).
This species was compared with Thelastomatidae parasitizing modern crane flies.
Various other lineages of parasitic nematodes or at least containing parasitic representatives (Mermithidae, Heterorhabditidae, Cosmocercidae) are now known
from Cretaceous to Cenozoic amber (Poinar 2015); in various cases these are still
associated with their arthropod hosts (Poinar 2011). This does not necessarily mean
parasitism of invertebrates started later, but probably rather reflects a preservation
and/or collection bias associated with these deposits.
Mermithidae (Mermithida) have been reported from various amber deposits. The
oldest fossils which have been assigned to this group (Poinar et al. 1994) derive
from Lebanese amber now attributed to the Barremian (Maksoud et al. 2017).
Mermithids are reminiscent in size and shape to nematomorphs, but have a smooth
outer cuticle as opposed to prominences observed in the cuticle of nematomorphs
(Poinar and Buckley 2006).
Node. Mermithida
Fossil Taxon. Cretacimermis libani
Phylogenetic justification. The characteristic of the final molt occurring in the
host, the absence of cross fibers in the cuticle, the lack of a tail projection on the
postparasitic cuticle as well as the host family speak for their similarity to the
extant Heleidomermis and their assignment to Mermithidae (Poinar et al. 1994).
The specimen was interpreted to be moulting in post-parasitic late ontogenetic
stage which is rare, but also observed in some extant Mermithidae parasitizing
chironomid and biting midges (Poinar 2011).
Fossil Evidence. Body fossil coiled in abdominal cavity of host in Lebanese Amber
(Poinar et al. 1994; Poinar 2011).
Host. Midge (Chironomidae)
Minimum age. 126.3 Ma. The age of the Lebanese amber has been pushed back to
the Barremian (e.g., Maksoud et al. 2017). These authors argued that amber from
middle to late Barremian was reworked from older Early Barremian strata. We
conservatively use the age of the Barremian-Aptian boundary as the minimum
age until the reworking hypothesis is more generally accepted and it is better
established that all amber with inclusions can be confidently attributed to the
early Barremian.
The earliest evidence for parasitic Rhabditida (Infraorder Rhabditomorpha) are
the Cretaceous Proheterorhabditis burmanicus parasitizing a rove beetle found in
Burmese Amber (Poinar 2011). Free-living forms (Vetus libani) initially unattributed on the family level (Poinar 2011) but later attributed to a closely related family
Rhabditidae prove the earliest evidence for the order Rhabditida (Poinar 2014). The
latter are slightly older as they can be traced to the Barremian as they were reported
from Lebanese amber.
7 Fossil Constraints on the Timescale of Parasitic Helminth Evolution
Minimum age. 236 Ma. See Ascaridomorpha.
Based on modern host associations and fossil record, oxyurids might have parasitized invertebrates before vertebrates (Poinar 2015). The oldest direct evidence for
oxyurids parasitizing invertebrates, however, is Paleothelastoma tipulae found
associated with the crane fly Gonomyia found in Burmese Amber (Poinar 2011).
This species was compared with Thelastomatidae parasitizing modern crane flies.
Various other lineages of parasitic nematodes or at least containing parasitic representatives (Mermithidae, Heterorhabditidae, Cosmocercidae) are now known
from Cretaceous to Cenozoic amber (Poinar 2015); in various cases these are still
associated with their arthropod hosts (Poinar 2011). This does not necessarily mean
parasitism of invertebrates started later, but probably rather reflects a preservation
and/or collection bias associated with these deposits.
Mermithidae (Mermithida) have been reported from various amber deposits. The
oldest fossils which have been assigned to this group (Poinar et al. 1994) derive
from Lebanese amber now attributed to the Barremian (Maksoud et al. 2017).
Mermithids are reminiscent in size and shape to nematomorphs, but have a smooth
outer cuticle as opposed to prominences observed in the cuticle of nematomorphs
(Poinar and Buckley 2006).
Node. Mermithida
Fossil Taxon. Cretacimermis libani
Phylogenetic justification. The characteristic of the final molt occurring in the
host, the absence of cross fibers in the cuticle, the lack of a tail projection on the
postparasitic cuticle as well as the host family speak for their similarity to the
extant Heleidomermis and their assignment to Mermithidae (Poinar et al. 1994).
The specimen was interpreted to be moulting in post-parasitic late ontogenetic
stage which is rare, but also observed in some extant Mermithidae parasitizing
chironomid and biting midges (Poinar 2011).
Fossil Evidence. Body fossil coiled in abdominal cavity of host in Lebanese Amber
(Poinar et al. 1994; Poinar 2011).
Host. Midge (Chironomidae)
Minimum age. 126.3 Ma. The age of the Lebanese amber has been pushed back to
the Barremian (e.g., Maksoud et al. 2017). These authors argued that amber from
middle to late Barremian was reworked from older Early Barremian strata. We
conservatively use the age of the Barremian-Aptian boundary as the minimum
age until the reworking hypothesis is more generally accepted and it is better
established that all amber with inclusions can be confidently attributed to the
early Barremian.
The earliest evidence for parasitic Rhabditida (Infraorder Rhabditomorpha) are
the Cretaceous Proheterorhabditis burmanicus parasitizing a rove beetle found in
Burmese Amber (Poinar 2011). Free-living forms (Vetus libani) initially unattributed on the family level (Poinar 2011) but later attributed to a closely related family
Rhabditidae prove the earliest evidence for the order Rhabditida (Poinar 2014). The
latter are slightly older as they can be traced to the Barremian as they were reported
from Lebanese amber.
7 Fossil Constraints on the Timescale of Parasitic Helminth Evolution