Fur Formation

The Fur Formation is a marine geological formation of Ypresian age which crops out in the Limfjord region of northern Denmark from Silstrup via Mors and Fur to Ertebølle, and can be seen in many cliffs and quarries in the area. The Diatomite Cliffs is on the Danish list of tentative candidates for World Heritage and may become a World Heritage site. Fossils found in the Fur Formation are primarily housed at the Fossil and Mo-clay Museum on Mors Island, the Fur Museum on Fur Island, and the Natural History Museum of Denmark in Copenhagen.

Geology

The Fur Formation is a unit of diatomitic sediment approximately 60 meters thick consisting of diatoms and clay minerals with up to 180 layers of volcanic ash. In Danish literature the formation has informally been referred to as the moler. The diatomite comprises 2/3 opal tests of diatoms and 1/3 clay, interbedded with layers of volcanic ash and a few limestone horizons, and has exceptionally complete fossil preservation.
It is known for its abundant fossil fish, insects, reptiles, birds and plants. The Fur Formation was deposited just above the Palaeocene-Eocene boundary, about 55 million years ago, and its tropical or sub-tropical flora indicate that the climate after the Paleocene-Eocene Thermal Maximum was moderately warm.
Glacial activity has moved and folded all exposed moler in a complicated pattern which permits very precise mapping of glacial movement at the end of the last ice age, and has, due to the ash layers, created an extraordinary pedagogical case for studying tectonics.

Members

The Fur Formation is divided into two members:
The lower Knudeklint Member was named for a location on the island of Fur. The upper Silstrup Member was named for a location in Thy. The stratigraphy exposed at Knudeklint constitutes the unit that containing the Paleocene/Eocene boundary informally named Stolleklint Clay, which grades up into the Fur Formation.

Paleontological significance

Fossils of great diversity and unique preservation Most unusual, if not unique, diversity of life from both ocean and land with extremely good preservation of details rarely seen, therefore very reliable reconstruction of palaeobiology. By far most of the "Danekræ" fossils since 1990 have been found in the Mo-clay area.

Birds

The Fur Formation preserves the earliest diverse Paleogene bird fauna known, with over 30 species, including some near complete, some preserved in 3-D, and some excellent bird-fossils. Most are the earliest known representatives of their orders and all are terrestrial birds.

Genus	Species	Higher taxon	Notes	Images
Chascacocolius	C. oscitans?	Sandcoleidae	Only known from one wing
Eocypselus	E. vincenti	Apodiformes	Mainly known from the London Clay
Galliformes indet.	Unapplicable	Galloanserae	Known from foot imprints distinct from all other Eocene galliforms
Lithornis	L. vulturinus	Lithornithidae	First complete lithornithid specimen known
Mopsitta	M. tanta	Psittaciformes incertae sedis?	Formerly the largest fossil parrot known, however it may actually be synonymous with the ibis Rhynchaeites
Morsoravis	M. sedilis	Morsoravidae	Formerly classed as a charadriiform before being reclassified as a basal member of Psittacopasseres
Halcyornithidae indet.	Unapplicable	Eufalconimorphae	Only known from one humerus
Pellornis	P. mikkelseni	Messelornithidae	Limb specialisation indicates it was likely cursorial, redescribed from several complete skeletons which support it being a crown-gruiform
Scandiavis	S. mikkelseni	Charadriiformes?	Likely a basal member due to features of the postcrania
Septencoracias	S. morsensis	Coraciiformes	One of the earliest rollers, preserved with fish in its stomach
Septentrogon	S. madseni	Trogonidae	Earliest trogon known

Reptiles

Several fossil sea turtles are known from the Fur Formation. In one of them, a large leatherback turtle remains of soft tissue and skin pigmentation have been recovered A number of well-preserved turtle specimens have been recovered from the formation, two of which have been recognized to be a completely new species of the genus Tasbacka.
Sea snakes are also known from the formation.

Palaeophis
Eosphargis brenieri
Cheloniidae and pan-Cheloniidae
Glarichelys
''Tasbacka''
Fish

Large teleostean fauna, oceanic, possibly including earliest truly deepwater fish, a 'whale-fish'; earliest members of many living families and Tertiary diversity preserved as complete skeletons; some rare and sensational large and complete specimens.
The following taxa are known:

Genus	Species	Location	Member	Notes	Images
?Analectis	?A. sp.		Fur	A turkmenid lampriform.
?Antigonia	?A. sp.		Fur	A boarfish.
Archaeozeus	A. skamolensis		Fur	An archaeozeid zeiform.
?Arius	?A. sp.		Fur	A sea catfish.
Atheriniformes indet.			Fur	An atheriniform.
Aulostomoidea indet.			Fur	An aulostomoid.
Brychaetoides	B. greenwoodi		Fur	A bonytongue.
cf. Brychaetus	B. sp.		Stolle Klint	A bonytongue.
Butyrumichthys	B. henricii		Fur	A medusafish.
Euzaphlegidae indet.			Fur	A euzaphlegid.
Exellia	E. sp.		Fur	An exelliid percomorph.
Furichthys	F. fieldsoei		Fur	A bonytongue.
Heterosteoglossum	H. foreyi		Fur, Stolle Klint	A bonytongue.
Holosteus	H. sp.		Fur	A barracudina.
Megalopidae indet.			Fur	A tarpon.
Mene	M. sp.		Fur	A moonfish.
Moclaybalistes	M. danekrus		Fur	A moclaybalistid tetraodontiform.
Muraenidae indet.			Fur	A moray eel.
Osteoglossiformes indet.			Fur	A small-sized osteoglossiform.
Palaeocentrotus	P. boeggildi		Fur	A palaeocentrotid lampriform.
Palaeorhynchidae indet.			Fur	A billfish.
?Percopsiformes indet.			Fur	A potential percopsiform.
Polyspinatus	P. fluere		Fur	A beardfish.
Protozeus	P. kuehnei		Fur	A protozeid zeiform.
Rhamphosus	R. sp.		Fur	A syngnathiform.
Rhinocephalus	R. sp.		Fur	A hake.
?Rondeletia	?R. sp.		Fur	A whalefish, possibly a redmouth whalefish.
?Salmonidae indet.			Fur	A potential salmonid.
?Sardinella	?S. sp.		Fur	A clupeid.
?Scorpaeniformes indet.			Fur	A potential scorpaeniform.
Surlykus	S. longigracilis		Fur	An argentiniform, the most common fish in the Mo-Clay.
?Vomeropsis	?V. sp.		Fur	A carangid.
Xosteoglossid	X. rebeccae		Stolle Klint	A bonytongue.

Insects

Huge fauna from land, over 200 species, many are oldest of their families; many with colour spots and eye lenses, some extraordinary preservation with stridulation apparatus in grasshoppers, and apparently migratory moth mass mortality.

Genus	Species	Higher taxon	Notes	Images
Apachyus	A. madseni	Apachyidae	First fossil apachyid
Cephalallus	C. vitalii	Spondylidinae	First longhorn beetle from the formation
Cryptocheilus	C. leleji	Pepsini	Earliest pompillid wasp known
Danoberotha	D. verkleijorum	Berothidae	First berothid from the formation
Danochrysa	D. madseni	Chrysopidae
Danolestes	D. moelleri	Lestoidea	A member of Lestoidea of uncertain affinities.
Danomantispa	D. frandseni	Mantispidae	Intermediate between Drepanicinae and Mantispinae
Eodysagrion	E. mikkelseni	Dysagrionidae	Member of its own subfamily, Eodysagrioninae
Eosassula	E. szwedoi	Nogodinidae	One of the few nogodinid fossils
Furagrion	F. jutlandicus	Zygoptera	Bears all wing venation characters of cephalozygopterans, but has a head similar to zygopterans
Furochrysa	F. alisae	Chrysopidae	Distinguished by a long crossvein
Mesypochrysa	M. nielseni	Chrysopidae	Latest record of the Mesozoic genus Mesypochrysa	-
Pachycondyla	P. rebekkae	Ponerinae	One of the earliest fossil ants in an extant genus at the time of description
Palaeopsychops	P. quadratus	Polystoechotidae	Bears stripes along its crossveins
Parabaissaeshna	P. ejerslevense	Aeshnidae	Resembles the Mesozoic Baissaeshna
Pseudotettigonia	P. amoena	Tettigoniidae	Preserves a complete stridulatory organ, with the structure of the organ suggesting that it was able to hear low ultrasound
Primorilestes	P. madseni	Dysagrionidae
Protheristria	P. roldae	Mantispidae	In the same subfamily as the other mantisfly known from the formation, but otherwise unrelated
Rhantus	R. villumi	Dytiscidae	Oldest species in the genus
Stephenbrooksia	S. multifurcata	Chrysopidae	Bears unusual hind wing venation
Stolleagrion	S. foghnielseni	Cephalozygoptera	First odonate known from the early Ypresian
Triachrysa	T. rusti	Chrysopidae	Has three series of crossveins in its wings, alongside several unrelated genera