Cascocauda (meaning "ancient tail") is an extinct genus of anurognathid pterosaur from the Late–⁠Middle Jurassic Tiaojishan Formation of Hebei Province, China.

The genus contains a single species, C. rong, known from a complete skeleton belonging to a juvenile individual preserved with extensive soft-tissues, including wing membranes and a dense covering of pycnofibres.

The specimen hails from the Mutoudeng locality of the Daohugou bed, located in Qinglong County in Hebei Province, which has been dated to around the Callovian to Oxfordian stages during the Middle to Late Jurassic period.

The second type consists of tufts of filaments joined near the base, similar to the branching down feathers of birds and other coelurosaurian dinosaurs, around 2.5–8.0 mm long and only cover the wing membranes.

Studies of sampled pycnofibres revealed the presence of microbodies within the filaments, resembling the melanosome pigments identified in other fossil integuments, specifically phaeomelanosomes.

[2] The identity of these branching structures as pycnofibres or feathers was challenged by Unwin & Martill (2020), who interpreted them as bunched-up and degraded aktinofibrils–stiffening fibres found in the wing membrane of pterosaurs–and attributed the melanosomes and keratin to skin rather than filaments.

Further, they argue that the restriction of melanosomes and keratin to the fibres, as occurs in fossil dinosaur feathers, supports the case they are filaments and is not consistent with contamination from preserved skin.

[2] NJU-57003 was initially reported as an anurognathid of undetermined species in 2018, although Yang and colleagues recognised that the specimen showed similarities to Jeholopterus and Dendrorhynchoides from the same local biota, and considered it likely to be a juvenile of one of these genera.

[1] A phylogenetic analysis performed in the same study found Cascocauda to be a member of the subfamily Batrachognathinae in a clade of relatively long-tailed anurognathids, potentially a primitive trait compared to the short-tailed derived anurognathines.

[1] A simplified version of their results is shown in the cladogram below: Cascocauda rong Sinomacrops bondei Batrachognathus volans Luopterus mutoudengensis Dendrorhynchoides curvidentatus Anurognathus ammoni Vesperopterylus lamadongensis