Pseudopulex

''Pseudopulex'' is an extinct genus of primitive fleas that lived between the Middle Jurassic and Early Cretaceous periods in what is now modern-day China. The Latin root for the name ''Pseudopulex'' roughly translates to "false fleas".

Discovery

There are currently four identified species in this genus: ''Pseudopulex jurassicus'', ''Pseudopulex magnus'', ''Pseudopulex wangi'', and ''Pseudopulex tanlan.'' The majority of current research focuses on ''P. jurassicus'' and ''P. magnus''.

Fossils of ''P. jurassicus'' date back to the middle Jurassic age of the Jiulongshan Formation in China, around 165 million years ago, while ''P. magnus'' was discovered from the Early Cretaceous Yixian Formation, around 125 million years ago. Currently, there have been a total of six other flea-like fossils that have been discovered along with this genus.

Description

''Pseudopulex'' species have dorsoventrally flattened bodies unlike modern fleas, but similar to common ectoparasites like ticks or bedbugs. They exhibit traits such as thinner, more elongated clawed appendages and extended mouthparts that can distinguish them from similar parasites such as lice. Several traits differentiate them from extant crown group fleas, which may be an indication of this genus possibly having an early evolution that resulted in a dead-end lineage. Their legs were quite long and each ended in a pair of long claws; however, unlike extant fleas, they lacked enlarged saltatorial hind legs.

Several features are used to distinguish the species of ''Pseudopulex''; ''P. jurassicus'' was slightly longer and possessed a shorter stylet, while ''P. magnus'' was thicker and had very long mouthparts.

''P. jurassicus'' has a body length of and a mouthpart length of 3.4 mm, which was twice the size of its head. This species had very small eyes, antennae, and a short torso covered in long thin bristles (setae).

''P. magnus'' was long with 5.2 mm long mouthparts. Their heads were relatively small, and their bodies were compressed and stout compared ''to P. jurassicus''. This species also exhibited antennae, dense setae, and claws on the ends of their legs, but had a distinctively large abdomen.

''P. wangi'' females were about long and had small heads, relatively short mouthparts, and short antennae. Males, however, were much smaller and had longer bodies with larger genitalia, indicating ''P. wangi'' was more sexually dimorphic than other species in its genus.

''P. tanlan'' was smaller than the other ''Pseudopulex'' species at about long, with a relatively small head and thoracic cavity. The body of ''P. tanlan'' also exhibits very short and stiff setae. Compared to ''P. magnus'' and ''P. jurassicus'', ''P. tanlan'' has relatively small male genitalia and short tibias in females. ''P. tanlan'' is considered to be a transitional organism between ''P. jurassicus'' or ''P. magnus'' and extant fleas as it has a smaller body plan, more compact antennae, and other features associated with extant fleas.

Paleobiology

Despite ''Pseudopulex'' having some similar characteristics to modern fleas, major differences in body morphology suggest differences in hosts compared to extant fleas. They possessed serrated stylets, which were likely used for feeding on blood through thick layers of skin, and are estimated to have been about fifty times larger than the dog flea.

Potential hosts for ''P. jurassicus'' include '' Pedopenna daohugouensis'' or ''Epidexipteryx hui'', while ''P. magnus'' may have parasitized '' Sinosauropteryx prima'' or '' Microraptor gui.'' They may have later adapted to parasitizing smaller birds and mammals, altering their morphology to more closely resemble modern-day fleas.

References

{{Taxonbar, from=Q140746

Fossil taxa described in 2012
Middle Jurassic insects
Late Jurassic insects
Cretaceous insects
Parasitic insects
Parasites of reptiles
Insects described in 2012
Prehistoric insects of Asia
Prehistoric insect genera
Fleas