Karai Formation Explained

Karai Formation
Type:	Geological formation
Age:	Albian to Turonian ~
Period:	Turonian
Prilithology:	Mudstone
Region:	Tamil Nadu, Cauvery basin
Country:	India
Coordinates:	11°N 78.9°W
Subunits:	Odiyam & Kunnam Members
Overlies:	Uttatur Group
Map:	.

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.^[1]

Paleobiota

Ichthyosaurs

Ichthyosaurs from the Karai Formation
Genus	Species	Location	Material	Notes	Images
Ichthyosauria	indet.^[2]		Vertebrae.	Previously known as "Platypterygius indicus".^[3]
Ichthyosaurus^[4]	I. indicus		A few complete and one partially complete vertebrae.	Considered a nomen dubium.^[5]
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.^[6]
Platypterygius	P. sp. indet.		An Anterior caudal vertebra.	A Platypterygiine ichthyosaur.^[7]

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.

Notes and 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 . 10.1038/ncomms10825 . 26953824 . 4786747 . 2016NatCo...710825F . 2041-1723.
3. Book: Foote . Robert Bruce . Indian Tertiary and post Tertiary Vertebrata . Lydekker . Richard . 1874 . Geological Survey Office [etc., etc.] . Calcutta. 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 . 10.1017/s0016756800181968 . 1888GeoM....5..309L . 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 . 10.7717/peerj.2604 . free . 27781178 . 5075704 . 2167-8359.
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 . en . 87 . 6 . 706–708 . 10.1007/s12594-016-0442-5 . 2016JGSI...87..706A . 0974-6889.