Agua Nueva Formation

The Agua Nueva Formation is a geologic formation in Mexico. It preserves fossils dated to the latest Cenomanian and Turonian ages of the Cretaceous period. It consists "predominantly of alternating fossiliferous, organic matter-rich, laminated, dark gray limestone and non-laminated, organic matter-poor limestone in decimeter-thick beds (10 to 30 cm) with occasional centimetric beds (5 cm) of brown shale that show no apparent internal structures."^[1] The formation is noted for its qualities as a Konservat-Lagerstätte, with notable finds including the plesiosaur Mauriciosaurus, the mosasaur Yaguarasaurus and sharks Ptychodus and Aquilolamna.

Agua Nueva Formation
Stratigraphic range: Latest Cenomanian to Turonian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Formation
Lithology
Primary	Limestone
Other	Shale. bentonite, chert
Location
Country	Mexico
Extent	San Luis Potosí

It appears to have been deposited on the upper part of a shallow continental shelf.^[2]

Fossil content

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.

Cartilaginous fish

Cartilaginous fish of the Agua Nueva Formation
Genus	Species	Location	Member	Material	Notes	Images
Aquilolamna	A. milarcae			Complete skeleton	A bizarre aquilolamnid shark.[3]
Lamniformes indet.				Articulated vertebrae	An indeterminate mackerel shark, potentially a cretoxyrhinid.[4]
Ptychodus	P. decurrens		Vallecillo	Teeth	A ptychodontid shark.[5][6]
	P. mortoni			Teeth
	P. sp.			Complete skeletons
cf. Scyliorhinus	S. sp.			Articulated vertebrae	A catshark.[7]

Ray-finned fish

Based on Amalfitano et al (2020):^[8]

Ray-finned fish of the Agua Nueva Formation
Genus	Species	Location	Member	Material	Notes	Images
Araripichthys	A. sp.				An araripichthyid.[2]	Fossil specimen from an unknown location
Belonostomus	B. sp.				An aspidorhynchid.	Fossil specimen from Germany
Clupeoidei indet.			Huehuetla		A relative of herrings.[9]
Enchodus	E. sp.		Huehuetla		An enchodontid aulopiform.[9]
Goulmimichthys	G. roberti		Vallecillo, Huehuetla		A pachyrhizodontid crossognathiform.[2][9]	Fossil specimen from Colombia
Hastichthys	H. sp.		Huehuetla		A dercetid aulopiform.[9]
"Nursallia"	"N." tethysensis		Huehuetla		A pycnodont.[9]	Fossil specimen from an unknown location
Pachyrhizodus	P. caninus				A pachyrhizodontid crossognathiform.
Paranursallia	P. gutturosa				A pycnodont.	Fossil specimen from an unknown location
Rhynchodercetis	R. regio				A dercetid aulopiform.[10]	Fossil specimen from Lebanon
Tingitanichthys	T. sp.				A pachyrhizodontid crossognathiform.[9]
Tselfatia	T. formosa		Huehuetla		A plethodid tselfatiiform.[9]	Fossil specimen from an unknown location
Vallecillichthys	V. multivertebratum		Vallecillo		A saurodontid ichthyodectiform.[2][11]

Lobe-finned fish

Lobe-finned fish of the Agua Nueva Formation
Genus	Species	Location	Member	Material	Notes	Images
Latimerioidei indet.				Gular plate	A large-sized marine coelacanth, potentially Megalocoelacanthus. Originally interpreted as a cephalopod gladius and given the name "Palaeoctopus pelagicus".[12]

Reptiles

Mosasaurs

Mosasaurs of the Agua Nueva Formation
Genus	Species	Location	Member	Material	Notes	Images
Yaguarasaurus	Y. regiomontanus				A plioplatecarpine mosasaur.[13]

Plesiosaurs

Plesiosaurs of the Agua Nueva Formation
Genus	Species	Location	Member	Material	Notes	Images
Mauriciosaurus	M. fernandezi				A polycotylid plesiosaur.[14]

Molluscs

Cephalopods

Cephalopods of the Agua Nueva Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images

See also

• Earth sciences portal
• Mexico portal
• Paleontology portal

• List of fossiliferous stratigraphic units in Mexico