Sabinal Formation

The Sabinal Formation is a Late Jurassic and Early Cretaceous-aged geological formation in Oaxaca, Mexico. It preserves a highly diverse marine fauna.^[1][2]

Sabinal Formation
Stratigraphic range: Kimmeridgian to Valanginian PreꞒ Ꞓ O S D C P T J K Pg N
Type	sedimentary
Unit of	Tlaxiaco Basin
Underlies	Tlaxiaco Formation
Overlies	Consuelo Group, Tecocoyuncan Group
Lithology
Primary	Shale
Other	Mudstone, wackestone, marl
Location
Coordinates	17.3°N 97.7°W / 17.3; -97.7
Approximate paleocoordinates	11.6°N 49.7°W / 11.6; -49.7
Region	Oaxaca
Country	Mexico
Sabinal Formation (Mexico)

It was initially thought to only encompass the Late Jurassic (Kimmeridgian & Tithonian), but more recent studies have redefined it to cover the earliest Cretaceous (Berriasian & Valanginian) as well. It is part of the Tlaxiaco Basin, a prominent structural basin in southern Mexico that accumulated both continental and marine sediments between the Early Jurassic and the Paleogene.^[2] The most prolific site of the formation is the Kimmeridgian-aged Llano Yosobe site near Tlaxiaco.^[1]

Vertebrate paleobiota

Cartilaginous fish

Cartilaginous fish of the Sabinal Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Planohybodus	P. sp.	Yosobé	Kimmeridgian	Teeth	A hybodont.[1]

Ray-finned fish

Ray-finned fish of the Sabinal Formation'
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Belonostomus	B. ornatus	Cerro de la Virgen	Berriasian		An aspidorhynchid.[3][4]
Gyrodus	G. sp.	Yosobé	Kimmeridgian	Teeth, partial skeleton	A pycnodont. The most abundant vertebrate fossil in the formation.[1]
Nhanulepisosteus	N. mexicanus	Yosobé	Kimmeridgian	Partial cranium	A gar, the earliest known from the fossil record.[5]
Otomitla	O. mexicana	Cerro de la Virgen	Berriasian		An ichthyodectiform.[4]
	O. speciosa
Pleuropholidae indet.		Yosobé	Kimmeridgian	Trunk with scales	A pleuropholid.[1]
Pleuropholis	P. cisnerosorum	Yosobé	Kimmeridgian	Partial skull	A pleuropholid.[6]
?Thrissops	T. sp.	Cerro de la Virgen	Berriasian		An ichthyodectiform.[4]
Vinctifer	V. ferrusquiai	Yosobé	Kimmeridgian	Parts of head and trunk	An aspidorhynchid.[7]

Reptiles

Crocodylomorphs

Crocodylomorphs of the Sabinal Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Maledictosuchus	M. nuyivijanan	Yosobé	Kimmeridgian	Nearly complete cranium, jaws, and some vertebrae	A metriorhynchid thalattosuchian. First record of this genus outside Europe.[8]
Torvoneustes	T. mexicanus (=Plesiosaurus mexicanus, Cricosaurus mexicanus)	Unknown, but most likely Yosobé	Kimmeridgian	Parts of cranium and jaws	A metriorhynchid thalattosuchian. First record of this genus outside Europe.[9]

Turtles

Turtles of the Sabinal Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Notoemys	N. tlaxiacoensis	Yosobé	Kimmeridgian	Nearly complete carapace with plastron	A stem-group sideneck turtle.[10][11]

Plesiosaurs

Plesiosaurs of the Sabinal Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Liopleurodon	L. sp.	Yosobé	Kimmeridgian	Partial jaw with teeth	A pliosaur. First record of this genus outside Europe.[12]
Pliosauridae indet.		Yosobé	Kimmeridgian	Vertebrae and ribs	An indeterminate pliosaur. Remains appear to have been scavenged by Planohybodus.[12]

Ichthyosauria

Ichthyosaurs of the Sabinal Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Ophthalmosauridae indet.		Yosobé	Kimmeridgian	Vertebrae	An ophthalmosaurid ichthyosaur.