409
some modern, siphonapteran morphology are an Early Cretaceous (Aptian) lineage,
Tarwiniidae, from Australia, consisting of laterally compressed and small bodies,
slender hind limbs for jumping, pseudoctenidial combs, diminutive eyes, and robust,
grasping tarsal claws (Huang 2015; Leung 2017). A third lineage is Saurophthiridae,
related to Pseudopulicidae and Tarwiniidae (Huang 2014), or alternatively with
Tarwiniidae as sister clade to Strashilidae (Rasnitsyn and Quicke 2002; Nagler and
Haug 2015). Saurophthirus resembles modern fleas by having a smaller size, more
abbreviated mouthparts, and very long legs (Fig. 11.6). However, once considered
as pterosaur ectoparasites (Ponomarenko 1976), Saurophthiridae lack ctenidia necessary for their ensconcement during flight on a pterosaur’s wing membrane, as
proposed by Ponomarenko (1976). By comparison, ichnopsyllid fleas on modern
bats possess ctenidia that affix them securely to bat wings in flight (Huang 2014).
For Saurophthiridae, life habits were more likely as nest inquilines or cleptoparasites feeding on a variety of dermal fluid substances, rather than as ectoparasites on
the body directly feeding on pterosaur blood (Huang 2014). Recent evidence based
on reconstruction of massive tracheae required for respiration indicates a larval
aquatic existence, while adults might have maintained a parasitic presence on pterosaurs (compare Leung 2021; Shcherbakov 2017; Rasnitsyn and Strelnikova 2017).
These three lineages likely had a similar timing of origin during the midMesozoic. One study indicates that modern fleas originated considerably later, during the Paleogene, and possibly earlier in the Late Cretaceous (Zhu et al. 2015).
Such origins and phylogenetic relationships would indicate that mid-Mesozoic lineages of fleas, which evidently became extinct during the mid Cretaceous, constituted a separate clade or group of related clades of flea-like organisms, possibly
affiliated with Siphonaptera or originating from a separate scorpionfly ancestor
(Huang et al. 2012). Accordingly, mid-Mesozoic “giant” fleas and modern, diminutive fleas were the two, distinctive subclades of a more broadly inclusive Siphonaptera
clade (Huang et al. 2012; also see Gao et al. 2014). Both subclades might have
evolved independently in parallel with the similarly independent evolution of
homoeothermic body temperatures on their respective host clades in a manner similar to blood-feeding Diptera and their major vertebrate host lineages (Lukashevich
and Mostovski 2003). The three lineages of Pseudopulicidae, Tarwiniidae and
Saurophthiridae evidently are closely related, share several features in common
typical of ectoparasites, and likely fed on the blood, lymph, sebum and other dermal
secretions of haired early mammals, birds or feathered dinosaurs (Huang 2014).
Modern aspect fleas, typical of all modern Siphonaptera lineages, are found in
major amber deposits of the Cenozoic (Leung 2017). The flea lineages fed on the
blood of birds and monotreme, metatherian and eutherian mammals (Zhu et al.
2015), through stylate mouthparts that were more gracile in almost every structural
aspect than those of the mid Mesozoic (Gao et al. 2014). An extensive list of characters, including mouthpart features, differentiate and link the five, major, midMesozoic flea-like lineages that are related by a Tarwinia + [(Pseudopulex +
Hadropsylla) + Tyrannopsylla] + [Saurophthirus + modern fleas] phylogeny (Huang
et al. 2012; Gao et al. 2014). Characters defining the six lineages include those of
the head, eyes, antennae, pronotum, coxae, tarsi, genitalia and cerci, but mouthpart
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution
some modern, siphonapteran morphology are an Early Cretaceous (Aptian) lineage,
Tarwiniidae, from Australia, consisting of laterally compressed and small bodies,
slender hind limbs for jumping, pseudoctenidial combs, diminutive eyes, and robust,
grasping tarsal claws (Huang 2015; Leung 2017). A third lineage is Saurophthiridae,
related to Pseudopulicidae and Tarwiniidae (Huang 2014), or alternatively with
Tarwiniidae as sister clade to Strashilidae (Rasnitsyn and Quicke 2002; Nagler and
Haug 2015). Saurophthirus resembles modern fleas by having a smaller size, more
abbreviated mouthparts, and very long legs (Fig. 11.6). However, once considered
as pterosaur ectoparasites (Ponomarenko 1976), Saurophthiridae lack ctenidia necessary for their ensconcement during flight on a pterosaur’s wing membrane, as
proposed by Ponomarenko (1976). By comparison, ichnopsyllid fleas on modern
bats possess ctenidia that affix them securely to bat wings in flight (Huang 2014).
For Saurophthiridae, life habits were more likely as nest inquilines or cleptoparasites feeding on a variety of dermal fluid substances, rather than as ectoparasites on
the body directly feeding on pterosaur blood (Huang 2014). Recent evidence based
on reconstruction of massive tracheae required for respiration indicates a larval
aquatic existence, while adults might have maintained a parasitic presence on pterosaurs (compare Leung 2021; Shcherbakov 2017; Rasnitsyn and Strelnikova 2017).
These three lineages likely had a similar timing of origin during the midMesozoic. One study indicates that modern fleas originated considerably later, during the Paleogene, and possibly earlier in the Late Cretaceous (Zhu et al. 2015).
Such origins and phylogenetic relationships would indicate that mid-Mesozoic lineages of fleas, which evidently became extinct during the mid Cretaceous, constituted a separate clade or group of related clades of flea-like organisms, possibly
affiliated with Siphonaptera or originating from a separate scorpionfly ancestor
(Huang et al. 2012). Accordingly, mid-Mesozoic “giant” fleas and modern, diminutive fleas were the two, distinctive subclades of a more broadly inclusive Siphonaptera
clade (Huang et al. 2012; also see Gao et al. 2014). Both subclades might have
evolved independently in parallel with the similarly independent evolution of
homoeothermic body temperatures on their respective host clades in a manner similar to blood-feeding Diptera and their major vertebrate host lineages (Lukashevich
and Mostovski 2003). The three lineages of Pseudopulicidae, Tarwiniidae and
Saurophthiridae evidently are closely related, share several features in common
typical of ectoparasites, and likely fed on the blood, lymph, sebum and other dermal
secretions of haired early mammals, birds or feathered dinosaurs (Huang 2014).
Modern aspect fleas, typical of all modern Siphonaptera lineages, are found in
major amber deposits of the Cenozoic (Leung 2017). The flea lineages fed on the
blood of birds and monotreme, metatherian and eutherian mammals (Zhu et al.
2015), through stylate mouthparts that were more gracile in almost every structural
aspect than those of the mid Mesozoic (Gao et al. 2014). An extensive list of characters, including mouthpart features, differentiate and link the five, major, midMesozoic flea-like lineages that are related by a Tarwinia + [(Pseudopulex +
Hadropsylla) + Tyrannopsylla] + [Saurophthirus + modern fleas] phylogeny (Huang
et al. 2012; Gao et al. 2014). Characters defining the six lineages include those of
the head, eyes, antennae, pronotum, coxae, tarsi, genitalia and cerci, but mouthpart
11 The History of Insect Parasitism and the Mid-Mesozoic Parasitoid Revolution