Chilcatay Formation

Chilcatay Formation
Stratigraphic range: Early Miocene (Burdigalian) [1] ~19.2–18.0  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Pisco Basin
Underlies	Pisco Formation
Overlies	Otuma Formation
Lithology
Primary	Sandstone, siltstone
Location
Country	Peru

The Chilcatay Formation is a geologic formation located in Peru. The formation was deposited in the Pisco Basin, during the Early Miocene, roughly from 19.2 to 18.0 Ma. Fossil remains of baleen whales, sharks, and rays have been found in the formation. ^{[2] [3]}

Paleobiota of the Chilcatay Formation

Mammals

Dolphins

Taxa	Species	Material	Description	Images	Notes
Huaridelphis	H. raimondii		A squalodelphinid river dolphin
Incacetus	I. broggii		A kentriodontid dolphin
cf. Kentriodon	cf. K. sp.		A kentriodontid dolphin
Macrosqualodelphis	M. ukupachai		A squalodelphinid river dolphin
Notocetus	N. vanbenedeni		A squalodelphinid river dolphin
Squalodelphinidae	Gen. et. sp. indet.		A river dolphin

Whales

Taxa	Species	Material	Description	Images	Notes
Amphidelphis	A. bakersfieldensis	A cranium			[4]
Cetotheriidae	Gen. et. sp. indet.
Chaeomysticeti	Gen. et. sp. indet.	A partial skull (CTZ 02)	A baleen whale; either a late-diverging stem mysticete or an early-branching crown mysticete
		A badly damaged dentary (ZM 98)	A baleen whale; crownward of Eomysticetidae
		A skull (ZM 152)	A crown-group baleen whale, possibly a basal plicogulan
Chilcacetus	C. cavirhinus		A toothed whale
	C. ullujayensis
Eurhinodelphinidae	Gen. et. sp. indet.		A toothed whale
Inticetus	I. vertizi		A toothed whale
Mysticeti	Gen. et. sp. indet.		A baleen whale
Odontoceti	Gen. et. sp. indet.		A toothed whale
Physeteroidea	Gen. et. sp. indet.		A sperm whale

Seals

Taxa	Species	Material	Description	Images	Notes
Pinnipedia	Gen. et. sp. indet.		A seal

Birds

Penguins

Taxa	Species	Material	Description	Images	Notes
Palaeospheniscus	P. sp.		A early penguin

Reptiles

Turtles

Taxa	Species	Material	Description	Images	Notes
Testudines	Gen. et. sp. indet.		A turtle

Crocodilians

Taxa	Species	Material	Description	Images	Notes
Sacacosuchus	S. cordovai		A gavialid crocodilian

Cartilaginous fish

Rays

Taxa	Species	Material	Description	Images	Notes
cf. Anoxypristis	cf. A. sp.	A rostral spine	A sawfish
Dasyatidae	Gen. et. sp. indet.	Dermal denticles	A whiptail stingray
Myliobatoidea	Gen. et. sp. indet.	Teeth	A stingray; several of the teeth compare favorably with Myliobatis eagle rays

Sharks

Taxa	Species	Material	Description	Images	Notes
Alopias	A. superciliosus	Teeth	The bigeye thresher
	A. cf. vulpinus	Teeth	Tentatively assigned to the common thresher
Anotodus	A. agassizii	Teeth	A thresher shark
Carcharhinus	C. brachyurus	Teeth	The copper shark
	C. dicelmai [5]
	C. cf. leucas	A tooth	Tentatively assigned to the bull shark
Carcharias	C. sp.	Teeth	A sand tiger shark
Carcharodon	C. subauriculatus		A white shark
Cosmopolitodus	C. hastalis	Teeth	White sharks
	C. plicatilis	Teeth
Galeocerdo	G. aduncus	Teeth	A tiger shark
Hemipristis	H. serra	Teeth	A weasel shark
Isurus	I. oxyrinchus	Teeth	The shortfin mako shark
Megalolamna	M. paradoxodon	A tooth	A megatoothed shark
Megachasma	M. cf. applegatei	Teeth	A megamouth shark
Negaprion	N. brevirostris	Teeth	The lemon shark
Otodus	O. chubutensis	Teeth	A megatoothed shark; sometimes placed in separate genus Carcharocles
Parotodus	P. benedenii	Teeth	A possible megatoothed shark
Physogaleus	P. contortus	Teeth	A ground shark
Sphyrna	S. zygaena	Teeth	The smooth hammerhead
Squatina	S. sp.	Teeth	An angel shark

References

1. Bosio, Giulia; Malinverno, Elisa; Villa, Igor Maria; Di Celma, Claudio; Gariboldi, Karen; Gioncada, Anna; Barberini, Valentina; Urbina, Mario; Bianucci, Giovanni (2020-03-25). "Tephrochronology and chronostratigraphy of the Miocene Chilcatay and Pisco formations (East Pisco Basin, Peru)" . Newsletters on Stratigraphy. 53 (2): 213–247. Bibcode:2020NewSt..53..213B. doi:10.1127/nos/2019/0525. ISSN   0078-0421.
2. Nobile, Francesco; Lambert, Olivier; Bianucci, Giovanni; Amson, Eli; Bosselaers, Mark; Bosio, Giulia; Pellegrino, Luca; Malinverno, Elisa; Di Celma, Claudio; Urbina, Mario; Collareta, Alberto (2025-03-13). "Surviving a Dark Age: The Oldest Baleen-Bearing Whales (Cetacea: Chaeomysticeti) of Pacific South America (Lower Miocene, Peru)". Life. 15 (3): 452. doi: 10.3390/life15030452 . ISSN   2075-1729. PMC   11944254 . PMID   40141799.
3. Landini, Walter; Collareta, Alberto; Di Celma, Claudio; Malinverno, Elisa; Urbina, Mario; Bianucci, Giovanni (2019-04-01). "The early Miocene elasmobranch assemblage from Zamaca (Chilcatay Formation, Peru)" . Journal of South American Earth Sciences. 91: 352–371. Bibcode:2019JSAES..91..352L. doi:10.1016/j.jsames.2018.08.004. ISSN   0895-9811.
4. Lambert, O.; de Muizon, C.; Bennion, R. F.; Urbina, M.; Bianucci, G. (2025). "New data on archaic homodont odontocetes from the Early Miocene of Peru reveal a second species of Chilcacetus Lambert, Muizon & Bianucci, 2015 and a Southern Hemisphere record for a northeastern Pacific species". Geodiversitas. 47 (9): 369–408. doi:10.5252/geodiversitas2025v47a9.
5. Collareta, A.; Kindlimann, R.; Baglioni, A.; Landini, W.; Sarti, G.; Altamirano, A.; Urbina, M.; Bianucci, G. (2022). "Dental Morphology, Palaeoecology and Palaeobiogeographic Significance of a New Species of Requiem Shark (Genus Carcharhinus) from the Lower Miocene of Peru (East Pisco Basin, Chilcatay Formation)". Journal of Marine Science and Engineering. 10 (10). 1466. doi: 10.3390/jmse10101466 . hdl: 11568/1160771 .