Strophodus

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
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Order:	†Hybodontiformes
Family:	†Acrodontidae
Genus:	†Strophodus; Agassiz, 1838
Species
	See text

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

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

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

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:^[4]

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.^[4]

References

^ Carrillo-Briceño, Jorge D.; Cadena, Edwin-Alberto (2022-06-02). "A new hybodontiform shark (Strophodus Agassiz 1838) from the Lower Cretaceous (Valanginian-Hauterivian) of Colombia". PeerJ. 10: e13496. doi:10.7717/peerj.13496. ISSN 2167-8359. PMC 9167585. PMID 35673391.
^ ^a ^b Stumpf, Sebastian; López-Romero, Faviel A.; Kindlimann, René; Lacombat, Frederic; Pohl, Burkhard; Kriwet, Jürgen (August 2021). Cavin, Lionel (ed.). "A unique hybodontiform skeleton provides novel insights into Mesozoic chondrichthyan life". Papers in Palaeontology. 7 (3): 1479–1505. Bibcode:2021PPal....7.1479S. doi:10.1002/spp2.1350. ISSN 2056-2799.
^ ^a ^b ^c Stumpf, Sebastian; Kettler, Christoph; Kindlimann, René; Cuny, Gilles; Kriwet, Jürgen (December 2023). "The oldest Gondwanan record of the extinct durophagous hybodontiform chondrichthyan, Strophodus from the Bajocian of Morocco". Swiss Journal of Palaeontology. 142 (1): 5. Bibcode:2023SwJP..142....5S. doi:10.1186/s13358-023-00270-w. ISSN 1664-2376.
^ ^a ^b Carrillo-Briceño, Jorge D.; Cadena, Edwin-Alberto (2022-06-02). "A new hybodontiform shark (Strophodus Agassiz 1838) from the Lower Cretaceous (Valanginian-Hauterivian) of Colombia". PeerJ. 10: e13496. doi:10.7717/peerj.13496. ISSN 2167-8359. PMC 9167585. PMID 35673391.

[:02-1] Carrillo-Briceño, Jorge D.; Cadena, Edwin-Alberto (2022-06-02). "A new hybodontiform shark (Strophodus Agassiz 1838) from the Lower Cretaceous (Valanginian-Hauterivian) of Colombia". PeerJ. 10: e13496. doi:10.7717/peerj.13496. ISSN 2167-8359. PMC 9167585. PMID 35673391.

[:2-2] Stumpf, Sebastian; López-Romero, Faviel A.; Kindlimann, René; Lacombat, Frederic; Pohl, Burkhard; Kriwet, Jürgen (August 2021). Cavin, Lionel (ed.). "A unique hybodontiform skeleton provides novel insights into Mesozoic chondrichthyan life". Papers in Palaeontology. 7 (3): 1479–1505. Bibcode:2021PPal....7.1479S. doi:10.1002/spp2.1350. ISSN 2056-2799.

[:1-3] Stumpf, Sebastian; Kettler, Christoph; Kindlimann, René; Cuny, Gilles; Kriwet, Jürgen (December 2023). "The oldest Gondwanan record of the extinct durophagous hybodontiform chondrichthyan, Strophodus from the Bajocian of Morocco". Swiss Journal of Palaeontology. 142 (1): 5. Bibcode:2023SwJP..142....5S. doi:10.1186/s13358-023-00270-w. ISSN 1664-2376.

[:0-4] Carrillo-Briceño, Jorge D.; Cadena, Edwin-Alberto (2022-06-02). "A new hybodontiform shark (Strophodus Agassiz 1838) from the Lower Cretaceous (Valanginian-Hauterivian) of Colombia". PeerJ. 10: e13496. doi:10.7717/peerj.13496. ISSN 2167-8359. PMC 9167585. PMID 35673391.

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