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Karai Formation

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Geologic formation in India
Karai Formation
Stratigraphic range: Albian to Turonian
~105.5–89.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N
TypeGeological formation
Sub-unitsOdiyam & Kunnam Members
UnderliesUnconformity with the Kulakkalnattam formation
OverliesUttatur Group
Lithology
PrimaryMudstone
Location
Coordinates11°00′N 78°54′E / 11.0°N 78.90°E / 11.0; 78.90
RegionTamil Nadu, Cauvery basin
Country India
]

The Karai Formation is a Mesozoic (Albian to Turonian) geologic formation in India. Fossilized ichthyosaur remains and shark teeth have been reported from this formation.

Paleobiota

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Ichthyosaurs

Ichthyosaurs from the Karai Formation
Genus Species Location Material Notes Images
Ichthyosauria indet. Vertebrae. Previously known as "Platypterygius indicus".
Ichthyosaurus I. indicus A few complete and one partially complete vertebrae. Considered a nomen dubium.
Ichthyosauria indet.
  • Six adult teeth (DUGF/41-45)
  • One juvenile tooth (DUGF/46)
  • Seven partial vertebrae.
 Was tentatively assigned to P. indicus. It is similar to other species of Platypterygius. It was later noted that only one of the teeth can be assigned to Platypterygiinae.
Platypterygius P. sp. indet. An Anterior caudal vertebra. A Platypterygiine ichthyosaur.

Chondrichthyans from the Karai Formation
Genus Species Location Material Notes Images
Protosqualus P. sp. One incomplete tooth. A Squalid shark.
Gladioserratus G. magnus One lower lateral tooth. A Hexanchid shark.
?Notidanodon ?N. sp. One tooth fragment. A Hexanchid shark.
Cretalamna C. appendiculaia Twenty-five teeth. An Otodontid shark.
Dwardius D. sudindicus Over a hundred teeth. A Lamniform shark.
?Eostriatolamia ?E. sp. One upper lateral tooth and a cusp of an anterior tooth. An Odontaspidid shark.
Squalicorax S. aff. baharijensis Five complete and two fragmentary teeth. An Anacoracid shark.
Cretodus C. longiplicatus Fifteen teeth. A Lamniform shark.

Mollusk

Mollusks from the Karai Formation
Genus Species Location Material Notes Images
Acanthoceras A. rhotomagense An Acanthoceratidae Ammonite.
Calycoceras
  • C. asiaticum
  • C. naviculare
 An Acanthoceratidae Ammonite.
Pseudocalycoceras
  • P. harpax
  • sp.
 An Acanthoceratidae Ammonite.
Kunnamiceras K. tropicum An Acanthoceratidae Ammonite.
Eucalycoceras E. pentagonum An Acanthoceratidae Ammonite.
Lotzeites L. aberrans An Acanthoceratidae Ammonite.
Desmoceras
  • D. latidorsatum
  • sp.
 A Desmoceratidae Ammonite.
Sciponoceras sp. A Baculitidae Ammonite.
Phylloceras P. seresitense A Phylloceratidae Ammonite.
Holcodiscoides H. elegans A Kossmaticeratidae Ammonite.
Cymatoceras C. huxleyanum A Nautilidae.
Eutrephoceras E. justum A Nautilidae.
Pycnodonte P. vesicularis An Oyster.

References

  1. ^ https://www.researchgate.net/publication/233085546_Marine_Vertebrates_from_the_%27Middle%27_Cretaceous_Early_Cenomanian_of_South_India
  2. Fischer, Valentin; Bardet, Nathalie; Benson, Roger B. J.; Arkhangelsky, Maxim S.; Friedman, Matt (2016-03-08). "Extinction of fish-shaped marine reptiles associated with reduced evolutionary rates and global environmental volatility". Nature Communications. 7 (1): 10825. Bibcode:2016NatCo...710825F. doi:10.1038/ncomms10825. ISSN 2041-1723. PMC 4786747. PMID 26953824.
  3. Foote, Robert Bruce; Lydekker, Richard (1874). Indian Tertiary and post Tertiary Vertebrata. Calcutta: Geological Survey Office doi:10.5962/bhl.title.125505.
  4. Lydekker, R. (July 1888). "VI.—Note on the Classification of the Ichthyopterygia (with a Notice of Two New Species)". Geological Magazine. 5 (7): 309–314. Bibcode:1888GeoM....5..309L. doi:10.1017/s0016756800181968. ISSN 0016-7568.
  5. https://www.redalyc.org/pdf/505/50510405.pdf
  6. ^ Fischer, Valentin (2016-10-20). "Taxonomy ofPlatypterygius campylodonand the diversity of the last ichthyosaurs". PeerJ. 4: e2604. doi:10.7717/peerj.2604. ISSN 2167-8359. PMC 5075704. PMID 27781178.
  7. Ayyasami, K.; Elamparuthi, S.; Gowtham, B. (2016-06-01). "An ichthyosaur vertebra from the Cretaceous (Middle Cenomanian) Karai Formation, southern India". Journal of the Geological Society of India. 87 (6): 706–708. Bibcode:2016JGSI...87..706A. doi:10.1007/s12594-016-0442-5. ISSN 0974-6889.
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