# Agua Nueva Formation

The Agua Nueva Formation is a geologic formation in Mexico. It preserves fossils dating back to the latest Cenomanian and Turonian stages 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." 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.
It appears to have been deposited on the upper part of a shallow continental shelf.

## 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 | Member | Material | Notes |
| Aquilolamna | A. milarcae | | Complete skeleton | A bizarre aquilolamnid shark. |
| Lamniformes indet. | | | Articulated vertebrae | An indeterminate mackerel shark, potentially a cretoxyrhinid. |
| Ptychodus | P. decurrens | Vallecillo | Teeth | A ptychodontid shark. |
| Ptychodus | P. mortoni | Vallecillo | Teeth | A ptychodontid shark. |
| Ptychodus | P. sp. | Vallecillo | Complete skeletons | A ptychodontid shark. |
| cf. Scyliorhinus | S. sp. | | Articulated vertebrae | A catshark. |

### Ray-finned fish

Based on Amalfitano et al (2020):
Ray-finned fish of the Agua Nueva Formation :
| Genus | Species | Member | Notes |
| Araripichthys | A. sp. | | An araripichthyid. |
| Belonostomus | B. sp. | | An aspidorhynchid. |
| Clupeoidei indet. | | Huehuetla | A relative of herrings. |
| Enchodus | E. sp. | Huehuetla | An enchodontid aulopiform. |
| Goulmimichthys | G. roberti | Vallecillo, Huehuetla | A pachyrhizodontid crossognathiform. |
| Hastichthys | H. sp. | Huehuetla | A dercetid aulopiform. |
| "Nursallia" | "N." tethysensis | Huehuetla | A pycnodont. |
| Pachyrhizodus | P. caninus | | A pachyrhizodontid crossognathiform. |
| Paranursallia | P. gutturosa | | A pycnodont. |
| Rhynchodercetis | R. regio | | A dercetid aulopiform. |
| Tingitanichthys | T. sp. | | A pachyrhizodontid crossognathiform. |
| Tselfatia | T. formosa | Huehuetla | A plethodid tselfatiiform. |
| Vallecillichthys | V. multivertebratum | Vallecillo | A saurodontid ichthyodectiform. |

### 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". | |

### Reptiles
#### Mosasaurs

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

#### Plesiosaurs

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

### Molluscs
#### Cephalopods

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