285
2011; Beltrame et al. 2015, 2018; Mowlavi et al. 2015), although the mostly poor
preservation of the outer shell layer impairs comparisons with modern eggs (compare Table III in Fugassa et al. 2011; Beltrame et al. 2015). In other cases, the
archiacanthocephalan genus remained unspecified (Table 8.1: Reinhard 1990; Horne
2002; Gonçalves et al. 2003 Hunt et al. 2012; Camacho et al. 2013; Nezamabadi
2014). A very recent paper additionally reports eggs of Oligacanthorhynchus, in
addition to Macracanthorhynchus and Gigantorhynchus, from Tamandua tetradactyla coprolites which were collected from 3,190 to 8,870 year old layers at archeological sites in Piauí state, Brazil (de Souza et al. 2020). However, keratin- and
chitin-like substances are not restricted to archiacanthocephalan eggs (see above).
So the question arises why archiacanthocephalan eggs predominate and why are
there so many human and carnivore coprolites among the egg-carrying samples.
This could partly reflect sampling bias because terrestrial caves usually attract high
research attention when they were human shelters in pre-historic times (e.g., Araújo
et al. 2015). But the skew might have a natural background in addition: First, higher
thickness of their shells should render archiacanthocephalan eggs particularly resistant to damaging effects (compare Camacho et al. 2013, 2018). Second, preservation through dehydration and undisturbed storage should be more likely to happen
to droppings in terrestrial caves than to feces released in other environments. Yet,
the gnathostomes that have left larger droppings in land caves in the relevant time
were mostly members of Carnivora and humans (e.g., Camacho et al. 2018). In any
case, these finds suggest that archiacanthocephalan eggs could be contained not
only in preserved human stool from mummies and latrines but also in mummified
cats etc., as has already been shown for eggs of endoparasitic nematodes (Nematoda)
and flatworms (Platyhelminthes) (Ferreira et al. 1983; Novo and Ferreira 2016; Yeh
and Mitchell 2016).
A recent report of ancient acanthocephalan eggs refers for the first time to fossilized remains. The corresponding four eggs were included in a phosphatized coprolite from Upper Cretaceous sediments in São Paulo State, Brazil (Cardia et al.
2019). The assignment of the four eggs to Acanthocephala and especially to
Archiacanthocephala is supported by the thickness and multi-layered appearance of
their eggshells, and also by the structures enclosed which in at least three cases are
reminiscent of acanthors (see Fig. 6b–d in Cardia et al. 2019). The fact that these
egg remains maximally show three eggshell layers does not preclude an archiacanthocephalan origin since the outermost egg shell layer generally tends to be poorly
preserved (see above). However, the extant species of Archiacanthocephala are primarily known to use mammals and birds as definitive hosts (e.g., Near 2002), while
the Cretaceous coprolite presumably has a crocodyliform origin (Cardia et al. 2019).
Although a wider spectrum of taxa from Tetrapoda may serve as paratenic host (see
e.g., Petrochenko 1958), there appears to be no indication that crocodiles belong to
the usual hosts. It would therefore be conceivable that—comparable to the above
example of a hairball—the Cretaceous animal, which left the dropping, devoured at
least one paratenic or definitive host of an archiacanthocephalan. In support of such
possibility, Cardia et al. (2019) state that the fluvial deposits of the respective
Brazilian Lagerstätte contain fossilized bones of fishes, lizards (Lacertilia), turtles
8 Thorny-Headed Worms (Acanthocephala): Jaw-Less Members of Jaw-Bearing…
2011; Beltrame et al. 2015, 2018; Mowlavi et al. 2015), although the mostly poor
preservation of the outer shell layer impairs comparisons with modern eggs (compare Table III in Fugassa et al. 2011; Beltrame et al. 2015). In other cases, the
archiacanthocephalan genus remained unspecified (Table 8.1: Reinhard 1990; Horne
2002; Gonçalves et al. 2003 Hunt et al. 2012; Camacho et al. 2013; Nezamabadi
2014). A very recent paper additionally reports eggs of Oligacanthorhynchus, in
addition to Macracanthorhynchus and Gigantorhynchus, from Tamandua tetradactyla coprolites which were collected from 3,190 to 8,870 year old layers at archeological sites in Piauí state, Brazil (de Souza et al. 2020). However, keratin- and
chitin-like substances are not restricted to archiacanthocephalan eggs (see above).
So the question arises why archiacanthocephalan eggs predominate and why are
there so many human and carnivore coprolites among the egg-carrying samples.
This could partly reflect sampling bias because terrestrial caves usually attract high
research attention when they were human shelters in pre-historic times (e.g., Araújo
et al. 2015). But the skew might have a natural background in addition: First, higher
thickness of their shells should render archiacanthocephalan eggs particularly resistant to damaging effects (compare Camacho et al. 2013, 2018). Second, preservation through dehydration and undisturbed storage should be more likely to happen
to droppings in terrestrial caves than to feces released in other environments. Yet,
the gnathostomes that have left larger droppings in land caves in the relevant time
were mostly members of Carnivora and humans (e.g., Camacho et al. 2018). In any
case, these finds suggest that archiacanthocephalan eggs could be contained not
only in preserved human stool from mummies and latrines but also in mummified
cats etc., as has already been shown for eggs of endoparasitic nematodes (Nematoda)
and flatworms (Platyhelminthes) (Ferreira et al. 1983; Novo and Ferreira 2016; Yeh
and Mitchell 2016).
A recent report of ancient acanthocephalan eggs refers for the first time to fossilized remains. The corresponding four eggs were included in a phosphatized coprolite from Upper Cretaceous sediments in São Paulo State, Brazil (Cardia et al.
2019). The assignment of the four eggs to Acanthocephala and especially to
Archiacanthocephala is supported by the thickness and multi-layered appearance of
their eggshells, and also by the structures enclosed which in at least three cases are
reminiscent of acanthors (see Fig. 6b–d in Cardia et al. 2019). The fact that these
egg remains maximally show three eggshell layers does not preclude an archiacanthocephalan origin since the outermost egg shell layer generally tends to be poorly
preserved (see above). However, the extant species of Archiacanthocephala are primarily known to use mammals and birds as definitive hosts (e.g., Near 2002), while
the Cretaceous coprolite presumably has a crocodyliform origin (Cardia et al. 2019).
Although a wider spectrum of taxa from Tetrapoda may serve as paratenic host (see
e.g., Petrochenko 1958), there appears to be no indication that crocodiles belong to
the usual hosts. It would therefore be conceivable that—comparable to the above
example of a hairball—the Cretaceous animal, which left the dropping, devoured at
least one paratenic or definitive host of an archiacanthocephalan. In support of such
possibility, Cardia et al. (2019) state that the fluvial deposits of the respective
Brazilian Lagerstätte contain fossilized bones of fishes, lizards (Lacertilia), turtles
8 Thorny-Headed Worms (Acanthocephala): Jaw-Less Members of Jaw-Bearing…