Ichthyodectes

Ichthyodectes Temporal range: Late Cretaceous (Cenomanian to Campanian) PreꞒ Ꞓ O S D C P T J K Pg N
Life restoration of I. ctenodon
Skeleton of I. ctenodon
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	†Ichthyodectiformes
Family:	†Ichthyodectidae
Subfamily:	†Ichthyodectinae
Genus:	†Ichthyodectes Cope, 1870
Species
See text

Ichthyodectes is an extinct genus of marine ichthyodectid ray-finned fish known from the Late Cretaceous of North America & Europe.^[1][2]

Taxonomy

The following definitive species are known:^[2]

• I. ctenodon Cope, 1870 - Cenomanian of Saskatchewan, Canada (Ashville Formation), Turonian of Northwest Territories (Lac des Bois)^[3] & Alberta (Kaskapau Formation), Canada and Kansas & South Dakota, US (Carlile Shale & Niobrara Formation), Coniacian to mid-Campanian of Manitoba, Canada (Pierre Shale Formation), and late Santonian/early Campanian of Alabama, US (Mooreville Chalk).^[1] All other Ichthyodectes species from the Niobrara Formation are now considered synonymous with I. ctenodon.^[4]
• I. tenuidens Woodward, 1901 - Cenomanian of England (English Chalk)^[5][6]

Another small indeterminate Ichthyodectes, previously assigned to the nomen dubium species I. minor (Egerton, 1850) is known from the Cenomanian to the Turonian of the English Chalk.^[6]

Although a number of species have previously been placed in the genus, more recent analyses indicate that only two species can confidently be placed in the genus, with the rest being synonymous with this species or belonging to different genera.^[2]

Biology

Skull of I. ctenodon

Ichthyodectes ctenodon ("fish biter with comb teeth") was an ichthyodectid over 3 m (9.8 ft) in length.^[7] It lived in the Western Interior Seaway of North America during the late Cretaceous. It was closely related to the 4–6 m (13–20 ft) long Xiphactinus audax, and the 2 m (6 ft 7 in) long Gillicus arcuatus, and like other ichthyodectids, I. ctenodon is presumed to have been a swift predator of smaller fish. As its species name suggests, I. ctenodon had small, uniformly sized teeth, as did its smaller relative, G. arcuatus, and may have simply sucked suitably sized prey into its mouth.^{[citation needed]}

A notable specimen of I. ctenodon was collected by Charles H. Sternberg from the Smoky Hill Chalk prior to 1919 and officially described in 2010. This specimen comprises a complete individual with the skeleton of a smaller fish, most likely an Enchodus petrosus, within its stomach. This specimen is reminiscent of the famous "fish-within-a-fish" Xiphactinus specimen, and confirms that Ichthyodectes had a piscivorous diet.^[8]

References

1. "PBDB Taxon". paleobiodb.org. Archived from the original on 2025-02-19. Retrieved 2026-06-23.
2. Cavin, Lionel; Forey, Peter L.; Giersch, Samuel (2013-02-01). "Osteology of Eubiodectes libanicus (Pictet & Humbert, 1866) and some other ichthyodectiformes (Teleostei): phylogenetic implications". Journal of Systematic Palaeontology. 11 (2): 115–177. doi:10.1080/14772019.2012.691559. ISSN 1477-2019.
3. Fielitz, Christopher (1996). "A Late Cretaceous (Turonian) Ichthyofauna from Lac des Bois,Northwest Territories, Canada, with paleobiogeographic comparisons with Turonian ichthyofaunas of the Western Interior Seaway". Canadian Journal of Earth Sciences. 33 (10): 1375–1389. doi:10.1139/e96-103. ISSN 0008-4077.
4. Lucas, Spencer G.; Sullivan, Robert M. (2006-01-01). Late Cretaceous Vertebrates from the Western Interior: Bulletin 35. New Mexico Museum of Natural History and Science.
5. "The Fossil Fishes of the English Chalk. Part III. Pages 97–128; Plates XXI–XXVI: Monographs of the Palaeontographical Society: Vol 61 , No 291 - Get Access". Monographs of the Palaeontographical Society. doi:10.1080/02693445.1907.12035529.
6. Friedman, Matt; Beckett, Hermione T.; Close, Roger A.; Johanson, Zerina (2015-11-23). "The English Chalk and London Clay: two remarkable British bony fishLagerstätten". Geological Society, London, Special Publications. 430 (1): 165–200. doi:10.1144/sp430.18. ISSN 0305-8719. Archived from the original on 2025-03-31.
7. "Huge Ichthyodectes Fish Fossil from Kansas". The Virtual Fossil Museum. Archived from the original on 26 August 2022.
8. Everhart, Michael J.; Hageman, Scott A.; Hoffman, Brian L. (2010). "Another Sternberg "Fish-within-a-Fish" Discovery: First Report of Ichthyodectes ctenodon (Teleostei; Ichthyodectiformes) with Stomach Contents". Transactions of the Kansas Academy of Science. 113 (3 &amp, 4): 197–205. doi:10.1660/062.113.0306. ISSN 0022-8443.