El Doctor Formation

The El Doctor Formation is a geologic formation in Mexico. It preserves fossils dating back to the Albian and Cenomanian stages of the Cretaceous period.^[1] Ammonite fossils show that age of Late Albian is more likely.^[2]

El Doctor Formation
Stratigraphic range: Albian-Cenomanian ~112–95 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Sub-units	La Negra Member
Lithology
Primary	Lime mudstone
Location
Coordinates	20.8°N 99.3°W / 20.8; -99.3
Approximate paleocoordinates	18.9°N 64.5°W / 18.9; -64.5
Region	Hidalgo
Country	Mexico
El Doctor Formation (Mexico) Show map of Mexico El Doctor Formation (Hidalgo) Show map of Hidalgo

Description

The light grey micritic limestone sequence with intercalated black chert lenses was deposited in an open marine basin with a hypersaline and/or poorly oxygenated bottom.^[1]

Fossil content

The formation has provided the following fossils:^{[1][3][4][5][2]}

Fish

• Squalicorax falcatus
• Ptychodus decurrens
• Rajiformes^[6]
• Enchodus zimapanensis^[7]
• Xeneichthys yanesi
• Heckelichthys preopercularis
• Motlayoichthys sergioi
• Nunaneichthys mexicanus
• Ichthyotringa mexicana
• Muhichthys cordobai
• Dalgoichthys tropicalis
• Handuichthys interopercularis
• Pseudomonocentris microspinosus
• Araripichthys sp.
• Vinctifer sp.
• Pachyrhizodus sp.
• cf. Tselfatia
• Pycnodontiformes
• Cladocyclidae
• Elopiformes
• Gonorhynchiformes
• Mawsoniidae^[8]

Arthropods

• Aeger hidalguensis
• Polzia eldoctorensis^[9]
• Victoriacaris muhiensis^[9]
• Palinurus sp.

Ammonites

• Mortoniceras sp.
• Hamites aff. renzi
• Beudanticeras sp.

Echinoderms

• Echinoidea
• Crinoidea

See also

• List of fossiliferous stratigraphic units in Mexico
  • Sierra Madre Formation