squamodisc

File:Pseudorhabdosynochus epinepheli (Monogenea, Diplectanidae) - squamodiscs.png Pseudorhabdosynochus epinepheli. Left, ventral squamodisc; right, dorsal squamodisc.]]

File:Parasite140121-fig3 Pseudorhabdosynochus jeanloui (Monogenea, Diplectanidae) Fig3d Squamodisc SEM.png Pseudorhabdosynochus jeanloui Bar: 2 μm.]]

File:Lamellodisc of Calydiscoides euzeti (Monogenea, Diplectanidae).png of the diplectanid Calydiscoides euzeti]]

Squamodiscs are epidermal structures, which are typical of and found only in certain monogeneans of the family Diplectanidae. There are, typically, two squamodiscs, one ventral and one dorsal, located on the haptor of the monogenean. Squamodiscs are usually made up of scales embedded in the epidermis, which appear from the outside as rodlets arranged in rows.{{cite thesis|first1=Guy|last1=Oliver|title=Les Diplectanidae Bychowsky, 1957 (Monogenea, Monopisthocotylea, Dactylogyridea). Systématique. Biologie. Ontogénie. Écologie. Essai de phylogenèse.|year=2015 |publisher=Figshare |doi=10.6084/M9.FIGSHARE.1295274|type=thesis |doi-access=free}}

According to the classical book of Bychowsky (1967),Bychowsky, B. E. (1957) Monogenetic Trematodes. Their systematic and phylogeny. Akad. Nauka. USSR. English translation by the American Institute of Biological Science, Washington. 509 pp.{{doi|10.5962/bhl.title.7475}} {{open access}} “the Diplectanidae] have special paired attaching formations lying above the disc and also partially on it, on the dorsal and ventral sides in the shape of small rounded convexities equipped with numerous [...] thorn-shaped little hooks or thin thread-like plates located more or less in concentric rows ("squamodisc")".

Ultrastructural studies of squamodiscs {{cite journal|last1=Shaw|first1=M. K.|title=The ultrastructure of the pseudohaptoral squamodiscs of Diplectanum aequans (Monogenea)|journal=Parasitology|volume=82|issue=2|year=2009|pages=231–240|issn=0031-1820|doi=10.1017/S0031182000056961|s2cid=85841816 }}{{cite journal|last1=Knoff|first1=Marcelo|last2=Cohen|first2=Simone Chinicz|last3=Cárdenas|first3=Melissa Querido|last4=Cárdenas-Callirgos|first4=Jorge M.|last5=Gomes|first5=Delir Corrêa|title=A new species of diplectanid (Monogenoidea) from Paranthias colonus (Perciformes, Serranidae) off Peru|journal=Parasite|year=2015|volume=22|pages=11|doi=10.1051/parasite/2015011|url= |pmid=25754099|pmc=4353888}}{{open access}} have shown that they include epidermally-embedded spines which are covered by the outer epidermal membrane. The spines are composed of a moderately electron-dense material with denser fibrils embedded within it.

A diplectanid genus Squamodiscus Yamaguti, 1934 was created but is now consideredYamaguti, S.(1963). Systema Helminthum Volume IV Monogenea and Aspidocotylea: John Wiley & Sons. a synonym of Diplectanum Diesing, 1858.

Some diplectanids, such as members of the genera Lamellodiscus or Calydiscoides, have a similar structure which is composed of lamellae, not rodlets; in this case the structure is called a lamellodisc.