Meristodonoides

Meristodonoides Temporal range: Aptian–Maastrichtian PreꞒ Ꞓ O S D C P T J K Pg N Possible Late Jurassic records [1]
Teeth of Meristodonoides sp. from the Late Cretaceous of Russia
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	† Hybodontiformes
Family:	† Hybodontidae
Genus:	† Meristodonoides Underwood & Cumbaa, 2010
Type species
†Hybodus rajkovichi Case, 2001
Species
See text

Meristodonoides is an extinct genus of hybodont known from the mid-late Cretaceous, with potential records dating back to the Jurassic. It is one of a number of hybodont genera composed of species formerly assigned to Hybodus . ^[2]

The genus is primarily known from remains from the Cretaceous of North America and Europe, spanning from the Aptian/Albian to Maastrichtian, making it one of the last surviving hybodont genera, though records of the genus likely extend as far back as the Late Jurassic, based on an undescribed skeleton from the Tithonian of England, and fragmentary teeth from the Kimmeridgian of Poland, England and Switzerland. ^[3]

Taxonomy

The type species is M. rajkovichi, which was originally a species in the genus Hybodus. The species, along with other Hybodus species such as H. butleri and H. montanensis, was reassigned to Meristodonoides by Charlie J. Underwood and Stephen L. Cumbaa in 2010. ^{[2] [4]}

Species

• M. butleri(Thurmond, 1971) - Aptian/Albian of Texas ^[3]
• M. montanensis(Case, 1978) - Campanian of Montana and Wyoming, with similar remains from the Santonian of New Mexico ^{[3] [5]}
• M. novojerseyensis(Case & Cappetta, 2004 ^[6] ) - Campanian of North Carolina, ^[7] Maastrichtian of New Jersey ^[3]
• M. rajkovichi(Case, 2001) (type species) - Cenomanian of Minnesota ^[3]
• M. multiplicatusCicimurri et al., 2014 - Santonian-Campanian of Mississippi ^[3]
• Other remains of the genus are known from the Coniacian of England, the Aptian-Albian of France, ^[8] and the Campanian of British Columbia, Canada, ^[9] European Russia ^[10] and France. ^[11]

Ecology

The morphology of the teeth suggests an adaptation to tearing prey, with a specialization for restraining fast-swimming prey such as small fish and squid. ^{[3] [12]} Fossils from the Western Interior Seaway suggest that it preferred nearshore marine environments, being absent from deeper-water areas, with it likely also being able to tolerate brackish and freshwater conditions. ^[4] In the Gulf Coastal Plain, Meristodonoides teeth are largely found in estuarine deposits. The restriction of Meristodonoides to nearshore habitats, combined with its late occurrence, fits the overall decline in niches occupied by hybodonts throughout the Cretaceous, likely due to them being outcompeted by lamniform sharks in open marine habitats. ^[12] However, some Meristonoides teeth have also been recovered from deep-water deposits representing open marine environments, such as the Northumberland Formation in Canada. ^[9]

References

1. Stumpf, S.; Meng, S.; Kriwet, J. (2022). "Diversity Patterns of Late Jurassic Chondrichthyans: New Insights from a Historically Collected Hybodontiform Tooth Assemblage from Poland". Diversity. 14 (2). 85. Bibcode:2022Diver..14...85S. doi: 10.3390/d14020085 .
2. Underwood, Charlie J.; Cumbaa, Stephen L. (2010). "Chondrichthyans from a Cenomanian (Late Cretaceous) bonebed, Saskatchewan, Canada". Palaeontology. 53 (4): 903–944. Bibcode:2010Palgy..53..903U. doi: 10.1111/j.1475-4983.2010.00969.x .
3. Stumpf, Sebastian; Meng, Stefan; Kriwet, Jürgen (2022-01-26). "Diversity Patterns of Late Jurassic Chondrichthyans: New Insights from a Historically Collected Hybodontiform Tooth Assemblage from Poland". Diversity. 14 (2): 85. Bibcode:2022Diver..14...85S. doi: 10.3390/d14020085 . ISSN   1424-2818.
4. Occurrence of the Hybodont Shark Genus Meristodonoides (Chondrichthyes; Hybodontiformes) in the Cretaceous of Kansas, Michael J. Everhart
5. "Selachians from the Upper Cretaceous (Santonian) Hosta Tongue of the Point Lookout Sandstone, central New Mexico". New Mexico Museum of Natural History & Science. 2011.
6. Case, G.R.; Cappetta, H. Additions to the elasmobranch fauna from the late Cretaceous of New Jersey (lower Navesink Formation, early Maastrichtian). Palaeovertebrata2004, 33, 1–16
7. Case, Gerald R.; Cook, Todd D.; Kightlinger, Taylor (2019-07-31). "A description of a middle Campanian euselachian assemblage from the Bladen Formation of North Carolina, USA". Vertebrate Anatomy Morphology Palaeontology. 7: 69–82. doi: 10.18435/vamp29345 . ISSN   2292-1389.
8. Guinot, Guillaume; Underwood, Charlie J.; Cappetta, Henri; Ward, David J. (August 2013). "Sharks (Elasmobranchii: Euselachii) from the Late Cretaceous of France and the UK" . Journal of Systematic Palaeontology. 11 (6): 589–671. Bibcode:2013JSPal..11..589G. doi:10.1080/14772019.2013.767286. ISSN   1477-2019. S2CID   84892884.
9. Cappetta, Henri; Morrison, Kurt; Adnet, Sylvain (2021-08-03). "A shark fauna from the Campanian of Hornby Island, British Columbia, Canada: an insight into the diversity of Cretaceous deep-water assemblages" . Historical Biology. 33 (8): 1121–1182. Bibcode:2021HBio...33.1121C. doi:10.1080/08912963.2019.1681421. ISSN   0891-2963.
10. Jambura, Patrick L.; Solonin, Sergey V.; Cooper, Samuel L.A.; Mychko, Eduard V.; Arkhangelsky, Maxim S.; Türtscher, Julia; Amadori, Manuel; Stumpf, Sebastian; Vodorezov, Alexey V.; Kriwet, Jürgen (March 2024). "Fossil marine vertebrates (Chondrichthyes, Actinopterygii, Reptilia) from the Upper Cretaceous of Akkermanovka (Orenburg Oblast, Southern Urals, Russia)". Cretaceous Research. 155: 105779. Bibcode:2024CrRes.15505779J. doi: 10.1016/j.cretres.2023.105779 . PMC   7615991 . PMID   38799703.
11. Valentin, Xavier; Vullo, Romain; Cuny, Gilles; Jansen, Olivier; Garcia, Géraldine (January 2026). "Hybodont shark remains from Campanian (Upper Cretaceous) continental deposits of southern France" . Cretaceous Research. 177: 106205. doi:10.1016/j.cretres.2025.106205.
12. Comans, Chelsea M.; Smart, Sandi M.; Kast, Emma R.; Lu, YueHan; Lüdecke, Tina; Leichliter, Jennifer N.; Sigman, Daniel M.; Ikejiri, Takehito; Martínez-García, Alfredo (2024). "Enameloid-bound δ15N reveals large trophic separation among Late Cretaceous sharks in the northern Gulf of Mexico" . Geobiology. 22 (1): e12585. Bibcode:2024Gbio...22E2585C. doi: 10.1111/gbi.12585 . ISSN   1472-4669. PMID   38385603.