Aridal Formation

The Aridal Formation in the Sahara Desert of southwestern Morocco is a fossil formation with rocks dating to the Lutetian - Priabonian (47.8 - 33.9 million years ago), preserving a middle Eocene shallow coastal environment.^[1]

Aridal Formation
Stratigraphic range: Middle Eocene, Lutetian–Priabonian
Chrysocetus fouadassii cast
Type	Geological formation
Lithology
Other	sandstone, marl
Location
Country	Morocco

The formation represents the world's richest Bartonian archaic whale assemblage, including protocetids and basilosaurids.^[2]

Paleobiota

Birds

Includes the earliest occurrence of the genus Pelagornis, extending its fossil record back by at least 10 million years.^[2]

Taxa	Rock Unit	Age	Image
Pelagornis sp.	Gueran	Bartonian
Pelagornithidae indet.	El Breij Unit II	Bartonian

Mammals

Alongside a rich assemblage of archaic whale taxa including two additional unnamed protocetid species,^[3] there are also possible remains of the earliest occurrence of Barytherium.^[4]

Taxa	Rock Unit	Age	Image
Pappocetus lugardi	Gueran,[3] Sabkha of Lebreij	Bartonian
Eocetus schweinfurthi	Gueran,[3] El Breij Unit II, El Breij Unit III	Bartonian
Chrysocetus fouadassii	Gueran[3]	Bartonian
Platyosphys aithai	Gueran[3]	Bartonian
? Barytherium sp.	Gueran[4]	Bartonian

Reptiles

There are at least three indeterminate species of turtles: two marine cryptodires, a cheloniid, a dermochelyid, and a possible littoral pleurodire. Two species of longirostrine crocodylians are present, including a gavialoid similar to Eogavialis africanum (which is typically known from younger strata), and one too fragmentary to identify beyond being a crocodyliform.^[2]

Taxa	Rock Unit	Age	Image
Pterosphenus schweinfurthi	Gueran	Bartonian
Palaeophis africanus	El Breij, Unit I	Lutetian
Palaeophiidae indet.	Sabkha of Lebreij	Bartonian
Cordichelys antiqua	El Breij, Unit I	Lutetian
Cheloniidae indet.	Gueran	Bartonian
Dermochelyidae indet.	Gueran	Bartonian
Pleurodira indet.	Gueran	Bartonian
Gavialoidea indet.	Gueran	Bartonian
Crocodyliformes indet.	Gueran	Bartonian
Crocodylia indet.	El Breij Unit I, Sabkha of Lebreij	Lutetian Bartonian

Cartilaginous Fish

Taxa	Rock Unit	Age	Image
Galeocerdo eaglesomei	Gueran	Bartonian
Pristis lathami	Gueran	Bartonian
Propristis schweinfurthi	Gueran	Bartonian
Macrorhizodus praecursor	Gueran	Bartonian
Hemipristis curvatus	Gueran	Bartonian
Carcharias koerti	Gueran	Bartonian
Otodus cf. sokolowi	Gueran	Bartonian
Tethylamna cf. twiggsensis	Gueran	Bartonian
Carcharhinus sp.	Gueran	Bartonian
Abdounia sp.	Gueran	Bartonian
Physogaleus sp.	Gueran	Bartonian

Bony Fish

Taxa	Rock Unit	Age	Image
Cylindracanthus sp.	Gueran, El Breij Unit I	Bartonian, Lutetian