The Hesseltal Formation or Blackcoloured Formation is a Late Cretaceous (late Cenomanian to early Turonian) geological formation from northern Germany. It consists of lithified marls and limestone, with a unique series of black shales deposited in anoxic conditions during the Cenomanian-Turonian boundary event.
It provides an important record of the fauna of the proto-North Sea basin. The formation's diversity of fossil fish is thought to be due to a consequence of an expanding oxygen minimum zone that caused mass mortalities among different communities of fish, including both those associated with warm surface waters and those associated with colder waters from upwelling. The anoxic conditions allowed for detailed preservation of some of these fish, including bony fish with their stomach contents preserved and even a few partial body fossils of cartilaginous fish. Fossil ammonites with preserved soft parts are also known.
The formation's deposition also documents the Plenus Cold Event, an enigmatic, brief but severe cooling event that occurred during the otherwise rapid global warming from the Cenomanian-Turonian boundary event, possibly as a consequence of changing ocean circulation.
Paleobiota Most fish are documented in Diedrich (2012) and a species list from Amalfitano et al (2020).
Bony fish GenusSpeciesLocationMaterialNotesImagesApateodusA. striatusAn ichthyotringid aulopiform.ArmigatusA. brevissimusAn ellimmichthyiform clupeomorph.AnomoeodusA. angustusA pycnodont.A. muensteriAulolepisA. typusA ctenothrissiform.ApsopelixA. anglicusA crossognathid crossognathiform.BananogmiusB. ornatusA plethodid tselfatiiform. Preserved with Clupavus in the stomach.BelonostomusB. cinctusAn aspidorhynchid.CimolichthysC. levesiensisA cimolichthyid aulopiform.ClupavusC. maroccanusA basal ostariophysian. The most common fish of the formation.CylindracanthusC. cf. minorRostral fragmentA fish of uncertain affinities.Dercetis (=Leptotrachelus)D. sp.A dercetid aulopiform.?DixonanogmiusD. sp.A plethodid.ElopopsisE. microdonA pachyrhizodontid crossognathiform.EnchodusE. lewesiensisAn enchodontid aulopiform.E. venatorHoplopteryxH. lewesiensisA trachichthyiform.IchthyodectesI. sp.An ichthyodectid.IchthyotringaI. africanaAn ichthyotringid aulopiform.NjoerdichthysN. dyckerhoffiGalgenknapp Quarry, Hohne QuarryA pycnodont.OsmeroidesO. lewesiensisAn osmeroidid elopiform.PachyrhizodusP. subulidensA pachyrhizodontid crossognathiform.P. sp.ParanursalliaP. gutturosaA pycnodont.ProtosphyraenaP. sp.A billfish-like pachycormid."Pycnodus""P." scrobiculatusA pycnodont.RhamphoichthysR. taxidiotisDIMAC QuarryA billfish-like plethodid.RharbichthysR. feroxAn aulopiform.RhynchodercetisR. sp.A dercetid aulopiform.ProtostomiasP. maroccanusA dragonfish-like teleost.TselfatiaT. formosaA plethodid.XiphactinusX. sp.An ichthyodectid.
Chondrichthyans GenusSpeciesLocationMaterialNotesImagesCantioscylliumC. decipiensA nurse shark.Carcharias C. sp.A sand shark.ChiloscylliumC. greeneiA bamboo shark.CretalamnaC. appendiculataAn otodontid shark.CretascyliorhinusC. aff. destombesiA scyliorhinid shark.CretodusC. semiplicatusA pseudoscapanorhynchid shark.CretoxyrhinaC. denticulataA cretoxyrhinid shark.C. mantelliDiprosopovenatorD. hilpertiPartial body fossilsA pseudoscyliorhinid shark (formerly Paraorthacodus sp.)?Eostriatolamia?E. subulataA sand shark.HeterodontusH. caniculatusA bullhead shark.H. polydictyosParanomotodonP. angustidensA thresher shark.ProtolamnaP. acutaA pseudoscapanorhynchid shark.P. sokoloviPseudoscyliorhinusP. schwarzhansiA pseudoscyliorhinid sharkPosadaiaP. nolfiA sand shark.PseudospinaxP. pusillusA bamboo shark.PtychodusP. decurrensArticulated specimen, teethA ptychodontid shark.P. mammilarisPolyacrodusP. polyptychusA hybodontid shark.ScapanorhynchusS. raphiodonA goblin shark.SqualicoraxS. falcatusA crow shark.Squatina (Cretascyllium)S. craneiAn angelshark.SquatirhinaS. westfalicaA ray of uncertain affinities.TuroniabatisT. ornataA ray of uncertain affinities.
Reptiles GenusSpeciesLocationMaterialNotesImagesConiasaurusC. crassidensDIMAC quarryDentary, teethA dolichosaurid squamateDolichosaurusD. longicollisDIMAC quarryDorsal vertebraA dolichosaurid squamateMosasauroidea indet.DIMAC quarryArticulated tailThe oldest articulated mosasaur remains from Europe.
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