The Akrabou Formation is a Late Cretaceous (latest Cenomanian to early/mid Turonian)-aged geological formation and Konservat-Lagerstätte in Morocco. It overlies the slightly older freshwater deposits of the Kem Kem Group, which it was once thought to be a part of. It was deposited over following the Kem Kem ecosystem's submergence by the Tethys Ocean during a marine transgression from the Cenomanian-Turonian boundary event, as part of a wider deposition of carbonate platforms across the region from the event.
Localities The Akrabou Formation has outcrops across the Anti-Atlas, but it has two especially prominent localities: Agoult and Goulmima (also known as Asfla). The Agoult locality is also commonly referred to as Gara Sbaa due to it outcropping at the hill of the same name, but this name is also used for the underlying freshwater-based deposit of the Kem Kem Group at the same locality, which may lead to nomenclatural confusion. Both localities are considered lagerstätten due to their excellently preserved fossils, but they differ in time period, paleoenvironment, and preservation of fossils.
The Agoult locality is the older of the two and appears to have been deposited around the time of the Cenomanian-Turonian boundary event, dating it to latest Cenomanian or earliest Turonian. It is a plattenkalk that contains excellently preserved two-dimensional fossils of fish, land plants, marine and terrestrial invertebrates, and some terrestrial reptiles. The presence of a significant terrestrial component indicates it was deposited in a shallow marine environment close to shore, although the deposits record the gradual deepening of the habitat as the sea level rose.
In contrast, the Goulmima locality is younger, dating to the early or mid Turonian, and appears to have been deposited in an offshore environment on the continental shelf. Fossils from this locality, which include fish and marine reptiles, are found in concretions and have a unique three-dimensional preservation akin to that of the older Santana Formation in Brazil.
In addition, several other localities are also known, some of which cross the border into Algeria, which have a rich fauna of ammonites and nautiloids.
Paleoenvironment In the basal Agoult horizons of the formation, a number of plant remains are known, which are similar to those found in southern Europe at the same time, suggesting floristic exchanges between northern Africa and southern Europe. Based on these, the paleoclimate of the ecosystem, at least earlier during its deposition, is suggested to have been a mildly dry subtropical climate akin to that of the modern western Canary Islands.
Paleobiota Most fish are documented in a species list from Amalfitano et al (2020) & Cooper et al (2023):
Vertebrates
Cartilaginous fish GenusSpeciesLocalityMaterialNotesImageAsflapristisA. cristadentisGoulmima Incomplete three-dimensional skeletons, isolated teethA ptychotrygonid sawskate.CretomantaC. sp.Goulmima Isolated teethA chondrichthyan of uncertain affinties, possibly an aquilolamnid.HaimirichiaH. amonensisAgoultPartial skeletonA haimirichiid mackerel shark.PtychodusP. maghrebianusGoulmimaDental battery, isolated teethA ptychodontid shark.PtychotrygonP. rostrispatulaGoulmimaIncomplete skeletonsA ptychotrygonid sawskate.?Rhinobatos?R. sp.GoulmimaIncomplete craniumA presumed guitarfish.SqualicoraxS. sp.GoulmimaTeethA crow shark.TingitaniusT. tenuimandibulusGoulmimaThree-dimensionally preserved incomplete skeleton of a young individualThe oldest known platyrhinid ray.
Bony fish GenusSpeciesLocalityMaterialNotesImageAcanthomorpha indet.AgoultComplete specimenA poorly-preserved acanthomorph of uncertain affinities.AgoultichthysA. chattertoniAgoultComplete specimenA macrosemiid.AgoultpycnodusA. aldrovandiiAgoultComplete specimenA pycnodont.Amioidea gen. et sp. nov. 1AgoultUndescribed amiiforms in their own family.Amioidea gen. et sp. nov. 2AnomoeodusA. sp. "A"GoulmimaIsolated jaw bones.A pycnodont.A. sp. "B"ArmigatusA. oligodentatusAgoultComplete specimensAn armigatid clupeomorph.BelonostomusB. sp.AgoultComplete specimenAn aspidorhynchid.AraripichthysA. corythophorusGoulmimaIncomplete specimens with associated skull remainsAn araripichthyiform.cf. Chanoidei indet.AgoultComplete specimenA potential chanid.CladocyclusC. sp.AgoultAn ichthyodectid.cf. Dercetiscf D. sp.AgoultComplete specimensA dercetid aulopiform.EnchodusE. sp.GoulmimaIncomplete specimens, isolated crania & teeth,An enchodontid aulopiform.ErrachidiaE. pentaspinosaAgoultComplete specimenA pharmacichthyid lamprimorph.GoulmimichthysG. arambourgiGoulmimaComplete specimen.A pachyrhizodontid crossognathiform.GrandemarinusG. gherisiensisGoulmima3 specimens known, one complete.A gar.GhrisichthysG. bardackiGoulmimaIsolated craniumAn ichthyodectid.HomalopagusH. multispinosusAgoultComplete specimenA pharmacichthyid lamprimorph.IchthyodectesI. sp.GoulmimaComplete specimen, isolated craniaAn ichthyodectid.KradimusK. asflaensisGoulmimaComplete specimen.A pachyrhizodontid crossognathiform.LusitanichthysL. africanusAgoultComplete specimenA clupavid otophysan.MaghrebichthysM. nelsoniAgoultComplete specimenA pycnosteroidid beardfish.NeomesturusN. asflaensisGoulmimaIsolated jaw bones.A pycnodont.NursalliaN. fenestrataGoulmimaA pycnodontOsmeroidesO. rherisGoulmimaIsolated craniaAn osmeroidid albuliform.ParanursalliaP. caviniGoulmimaIsolated jaw bones.A pycnodont.PleuropholisP. danielaeAgoultComplete specimenThe last known pleuropholid.PolazzodusP. sp.GoulmimaIsolated jaw bones.A pycnodont.RhynchodercetisR. sp.AgoultComplete specimens.A dercetid aulopiform.SaurorhamphusS. sp.AgoultComplete specimens.A eurypholid aulopiform.SorbinichthysS. africanusAgoultComplete specimen.A sorbinichthyid clupeomorph.Teleostei indet.AgoultComplete specimenAn indeterminate teleost.ThorectichthysT. marocensisAgoultComplete specimens.A paraclupeid clupeomorph.T. rhadinus
Reptiles GenusSpeciesLocalityMaterialNotesImageBrachaucheniusB. lucasiGoulmimaPartial mandibleA pliosaur, the first record of this species outside North America.LibonectesL. morgani (=L. atlasense)GoulmimaArticulated skull and post-cranial skeleton.An elasmosaurid plesiosaur, the first record of this species outside North America.ManemergusM. anguirostrisGoulmimaPartially complete skeletonA polycotylid plesiosaur.Protostegidae indet.GoulmimaCarapace, skullIndeterminate protostegid turtles.TethysaurusT. nopcsaiGoulmimaHundreds of specimens of different age classes, some nearly completeA tethysaurine mosasaur.ThililuaT. longicollisGoulmimaComplete skull, lower jaw, and articulated vertebraeA polycotylid plesiosaur.Polycotylidae indet.GoulmimaSkull with mandibleAn indeterminate polycotylid plesiosaur.Squamata indet.AgoultComplete specimenA small indeterminate terrestrial lizard, specimen now lost.
Mollusks Based on Kennedy et al (2008) & Meister et al (2017): GenusSpeciesLocalityMaterialNotesImageAngulithesA. mermetiDouira, Goulmima & TazzougertShellsA hercoglossid nautiloid.ChoffaticerasC. segneGoulmimaA pseudotissotid ammonite.C. sinaiticumEutrephocerasE. sp.Douira & TaouzA nautilid nautiloid.FagesiaF. peroniGoulmimaA vasoceratid ammonite.F. cf. tevesthensisHoplitoidesH. mirabilisGoulmimaA hoplitid ammonite.H. gr. wortmanniMammitesM. nodosoidesGoulmimaAn acanthoceratid ammonite.NannovascocerasN. intermediumGoulmimaA vasoceratid ammonite.NeolobitesN. vibrayeanusAgoult, Tazzougert, Taouz, Tizi MomradAn engonoceratid ammonite.NeoptychitesN. cephalotusGoulmimaA vasoceratid ammonite.N. aff. hottingeriGoulmimaRomaniceras (Yubariceras)R. (Y.) reymentiGoulmimaAn acanthoceratid ammonite.ThomasitesT. rollandiGoulmimaA vasoceratid ammonite.WrightocerasW. munieriGoulmimaA pseudotissotid ammonite.
Arthropods Partially based on Garassino, Angeli & Pasini (2014): GenusSpeciesLocalityMaterialNotesAfroapseudesA. cretacicusAgoultA tanaidacean crustacean.AmazighopsisA. cretaceaAn astacidean crustacean.CorazzatocarcinusC. cf. hadjoulaeA necrocarcinid crab.CretagalatheaC. exiguaA munidid squat lobster.CretapenaeusC. berberusA penaeid prawn.GalatheaG. saharianaA galatheid squat lobster.?GlypheaG. garaasbaensisA glypheid crustacean.MesolimulusM. tafraoutensisTwo complete specimensA horseshoe crab.?Isoptera indet.Complete specimenA potential termite.MarocarcinusM. pasiniiA marocarcinid crab.MuelleristhesM. africanusComplete specimenA porcelain crab.Palinuridae indet.Complete specimenA spiny lobster.PhagophytichnusP. ekowskiiTrace fossilFeeding traces on a leaf.Polyphaga indet.Complete specimenA polyphagan beetle.TelamonocarcinusT. cf. gambalatusA dorippid crab.TroponomaT. constrictaTrace fossilTrail made by a leafminer.UnusuropodeU. castroiComplete specimenA sphaeromatid isopod, first record of this species outside Brazil.
Plants Based primarily on Krassilov & Bacchia (2013): GenusSpeciesLocalityMaterialNotesImageAbietitesA. (Tritaenia) cf. linkiiAgoultNeedlesA conifer.BarykoviaB. cf. tschuckotikaLeafA potentially fagalean angiosperm.CocculophyllumC. cf. fucinerveLeafA climbing angiosperm.ConiopterisC. cf. Dicksonia mamiyaiLeaflet.A fern.DryophyllumD. cf. subcretaceumLeafA potentially fagalean angiosperm.FrenelopsisF. cf. teixeiraeShootA cheirolepidiacean conifer.GarasbahiaG. flexuosaBranching shoot with leaves.A cabombacean angiosperm.PseudotorelliaP. cf. ensiformisLeafA ginkgoalean.SulcatocladusS. cf. robustusShootA conifer.WelwitschiophyllumW. sp.LeafA possible welsitschialean.
References