Palaeacanthocephala ("ancient thornheads") is a class within the phylumAcanthocephala. The adults of these parasiticplatyzoans feed mainly on fish, aquatic birds and mammals. This order is characterized by the presence of lateral longitudinal lacunar canals and a double-walled proboscis receptacle.[1] The nuclei of the hypodermis (outer layer of skin) are fragmented and the males have two to seven cement glands, unlike their relatives the Archiacanthocephala, which always have eight.
There are three orders in the class Palaeacanthocephala:[2]
^Bursey, C. R., Goldberg, S. R., & Kraus, F. (2007). New family, new genus, new species of Acanthocephala (Echinorhynchida) from the lizard, Sphenomorphus granulatus (Sauria: Scincidae), from Papua New Guinea. Open Parasitology Journal, 1, 41-44. Found at: https://benthamopen.com/contents/pdf/TOPARAJ/TOPARAJ-1-7.pdf