New Transitional Fleas from China Highlighting Diversity of Early Cretaceous Ectoparasitic Insects

Abstract

Fleas are a group of highly specialized blood-feeding ectoparasites whose early evolutionary history is poorly known. Although several recent discoveries have shed new light on the origin of the group, a considerable gap exists between stem fleas and crown fleas. Here we report a new transitional flea, Saurophthirus exquisitus sp. nov., assigned to a new family Saurophthiridae fam. nov., from the Lower Cretaceous Yixian Formation of northeastern China. Saurophthirids are more similar to crown fleas than other stem fleas in having a relatively small body size, relatively short and slender piercing-sucking stylet mouthparts, comparably short and compact antennae, rows of short and stiff bristles on the thorax, and highly elongated legs. The new finding greatly improves our understanding of the morphological transition to the highly specialized body plan of extant fleas. However, saurophthirids also display several features unknown in other fleas, and some of these features are suggestive of a possible ectoparasitic relationship to contemporaneous pterosaurs, though other possibilities exist. The new fossils, in conjunction with previous discoveries, highlight a broad diversity of ectoparasitic insects in the mid-Mesozoic.

Fleas (Siphonaptera) are Cretaceous, and evolved with Theria

“…Because the Mesozoic fleas co-occur in the same general fossil beds as feathered dinosaur fossils, ancestral evolution with feathered or ''hairy'' dinosaurs or pterosaurs has been suggested (Gao et al, 2013(Gao et al, , 2012Huang et al, 2013aHuang et al, , 2012. This conflicts with the currently accepted idea of an early siphonapteran association with mammals, which had been proposed after conducting general host-association mapping on a topology with a subset of flea lineages (Whiting et al, 2008).…”

“…1). On the other hand, Gao et al (2013) place only Saurophthiridae into the Siphonaptera, and also suggest it was a transitional ancestral form of extant fleas (Fig. 1).…”

“…Sequence data stem from an increased gene sampling of previously published data (Whiting et al, 2008), as well as an extended species sampling (GenBank accession numbers KM890312-KM891539) (Table S1). Gao et al (2013) and Huang et al (2012Huang et al ( , 2013a …”

“…1). The presumed flea finds (also referred to as pre-fleas) are dated from the Early Cretaceous to the Mid Jurassic, thus extending the possible origins of the flea lineage significantly into the past (Gao et al, 2013(Gao et al, , 2012Huang et al, 2013aHuang et al, , 2012.…”

The Jurassic Bajanzhargalanidae (Insecta: Grylloblattida?): New genera and species, and data on postabdominal morphology

“…Gao et al, 2013;Gao et al, 2012;Ren et al, 2010;Wang et al, 2012Wang et al, , 2010. They are deposited in the Key Laboratory of Insect Evolution & Environmental Changes, College of Life Sciences, Capital Normal University (CNU; Beijing, China; Ren Dong, Curator).…”