Strophodus

Strophodus is an extinct genus of durophagous hybodont known from the Triassic to Cretaceous. It was formerly confused with Asteracanthus.

Strophodus Temporal range: Middle Triassic–Hauterivian PreꞒ Ꞓ O S D C P T J K Pg N
Jaw fragment of Strophodus atlasensis
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	†Hybodontiformes
Family:	†Acrodontidae
Genus:	†Strophodus Agassiz, 1838
Species
See text

Taxonomy

It has long been confused with Asteracanthus due to the fin spines of the latter being found associated with the teeth of Strophodus. However, both genera can now be reliably be distinguished base on the morphology of both the fin spines and teeth.^[1][2]

Description

Teeth of Strophodus rebecae

Species of Strophodus had heavily rounded, durophagous crushing teeth, contrasting strongly with those of Asteracanthus, which are much more similar to those of Hybodus. Species of Strophodus have been estimated to reach up to 3 metres (9.8 ft) in length, making them some of the largest hybodonts.^[3] Like Asteracanthus, but unlike other hybodonts, the fin spines of Strophodus are covered in tubercles rather than being ribbed.^[2]

Ecology

Life reconstruction of Strophodus rebecae with associated fauna found in the Rosa Blanca Formation

Strophodus has been interpreted as a bottom-dwelling animal that fed on hard-shelled invertebrates, though isotopic evidence has suggested that it may have been pelagic. It may also have been euryhaline.^[3]

Species

Species of Strophodus:^[1]

• S. reticulatus (Agassiz, 1838) Middle-Late Jurassic (Bathonian–Tithonian) England, France, Germany, Hungary and Switzerland. A similar form S. cf. reticulatus is known from the Middle Triassic of Switzerland;
• S. atlasensis (Stumpf et al., 2023) Middle Jurassic (Bajocian) Morocco;^[3]
• S. smithwoodwardi (Peyer, 1946) Early Jurassic (Toarcian) Switzerland;
• S. dunaii (Szabó & Főzy, 2020) Middle Jurassic (Aalenian) Hungary;
• S. tenuis (Agassiz, 1838) Middle Jurassic (Aalenian-Bathonian) Germany, England;
• S. longidens (Agassiz, 1838) Middle Jurassic (Bathonian) France;
• S. magnus (Agassiz, 1838) Middle Jurassic (Bathonian) France, India, England;
• S. indicus (Sharma & Singh, 2021) Middle Jurassic (Bathonian) India;
• S. jaisalmerensis (Kumar et al., 2021) Middle Jurassic (Bathonian) India;
• S. medius (Owen, 1869) Middle Jurassic (Bathonian-Callovian) India, France, England;
• S. subreticulatus (Agassiz, 1838) Late Jurassic (Kimmeridgian) Switzerland;
• S. udulfensis (Leuzinger et al., 2017) Late Jurassic (Kimmeridgian) Switzerland, ?England;
• S. tridentinus (Zittel, 1870) Late Jurassic (Tithonian) Italy (possibly a nomen dubium);
• S. rebecae (Carrillo-Briceño & Cadena, 2022) Early Cretaceous (Valanginian-Hauterivian) Colombia.

Indeterminate remains of Strophodus possibly extend into the Albian stage of the Early Cretaceous. Claimed records of the genus from the Late Cretaceous are doubtful.^[1]