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The Chondrichthyes assemblages from the Røsnæs Clay - Knudshoved Member (Early Eocene) compared to the Fur Formation and the Ølst Formation, from the Isle of Mors in Denmark

HENRIK MADSEN

A new found Chondrichthyes assemblages from the Eocene Røsnæs Clay Formation (Middle Ypresian) on the Isle of Mors in Denmark yielded teeth of ? different genera/species from bulk sampling. The fauna is dominated by deepwater genera like Centrophorus, Isistius, Echinorhinus, Lamniform, Pristiophorus and Hexanchiformes. All the shark teeth are reported for the first time from the Early Middle Ypresian, Røsnæs Clay Formation, – Knudshoved Member.

The record of Centrophorus aff. granulosus extends the origin of the Centrophorus granulosus group back to the Middle Ypresian. Previous the oldest known was found in the Lillebælt Clay Formation, bed L2 at Trelde Næs. (Carlsen & Cuny 2014).

The record of Megascyliorhinus cooperi extends the origin of the Megascyliorhinus cooperi group back to the Middle Ypresian. Previous the oldest known was found in the London Clay Formation, division B1 at Tankerton. (Rayner et al. 2009).

The record of Xiphodolamia ensis extends the origin of the Xiphodolamia ensis group in the North Sea Basin, back to the Middle Ypresian. Previous the oldest known was found in the London Clay Formation, division D at Sheppey. (Rayner et al. 2009).

The record of Orthechinorhinus pfeili extends the origin of the Orthechinorhinus pfeili group back to the Middle Ypresian. Previous the oldest known was found in Saint-Geours-d'Auribat – Ypresian/Lutetien border. (Adnet 2006).

The fauna suggests deposition in a deep-water environment in subtropical waters on the middle or outer continental shelf at water depth from 600 to 1000 m (Schmitz et al. 1996).

Keywords: Denmark, Røsnæs Clay Formation, Eocene, Chondrichthyes, fossil teeth.

Henrik Madsen [henrik.madsen@museummors.dk], Fossil- og Molermuseet, Museum Mors,

Skarrehagevej 8, 7900 Nykøbing Mors, Denmark.

The aim of this paper is to make a list on the chondrichthyes fossil teeth from the Røsnæs Clay Formation – Knudshoved Member (Heilmann-Clausen 1982), on the Isle of Mors, Denmark, and compare the assemblage with the Fur Formation which is underlying the Røsnæs Clay Formation – Knudshoved Member. Furthermore the special unformal Sundbylayer, rich in elasmobranch fossil teeth deposited between the Stolleklint Clay and the Fur Formation are used to compare the fauna before the Fur Formation and Røsnæs Clay Formation – Knudshoved Member. This fauna, although well known by palaeontologists in Denmark, has never been described in the scientific literature. Moreover, the composition of the fauna gives information on the climate and depositional environment. The screen-washed bulk material from the layers, bonebed G1 and bonebed G2 of the Røsnæs Clay Formation – Knudshoved Member, and the provenance of this material is therefore precisely known, dating from the Middle Ypresian, Eatonicysta ursulae dinoflagellate Zone (Heilmann-Clausen 1988) . The locality at Grønbjerg Klint and the material are new to science.

In the Fur Formation the assemblage of the elasmobranch only consist of 7 or 8 different genera/species, determined by David Ward on a visit to The Fossil- and Moclaymuseum. The assemblage of the chondrichthyes in the Sundbylayer consist of 31 different genera, determined by David Ward, Gilles Cuny and Agnethe Carlsen. The assemblage of the chondrichthyes in the Røsnæs Clay Formation – Knudshoved Member, consist of 29 different genera/species, determined by the author and David Ward.



Fig. 1. The places were the different
types of clay in this articel are found.
1: Sundby Klint, 2: Hanklit, 3: Salgerhøj Klint, 4: Grønbjerg Klint. 5: Knudeklint.

Geological setting

In a distance of 7 km from Sundby Klint to Grønbjerg Klint on the Isle of Mors, it is possible to find shark teeth in these tree Geological Formations: Ølst Formation, Fur Formation, Røsnæs Clay Formation. The time span is around 2 ma. Age 55,8 – 53,7 ma.

Here the shark assemblage is compared in a small area in the North Sea basin were the fossils were deposited, at a time when the area went through some huge changes in climate and environment. The Paleocene-Eocene Thermal Maximum Kennett & Stott (1991) began approximately 55,8 million years before present (Röhl et al. 2007) and lasted about 170,000 years. The PETM involved more than 5oC of warming. The Eocene Thermal Maximum 2 was another period of global warming that occurred approximately 53.7 million years before present and represents the second largest of the major Eocene hyperthermals.


Fig. 2. Paleomaps modified from Bonde 1972 and Ziegler 1990.
1: Ølst Formation, 2: Fur Formation, 3: Røsnæs Clay Formation.

Ølst-Formation

The shark teeth from the Ølst-Formation are rarely found in the shale, over the volcanic ash layer -33, but the far most specimens and species is from the unofficial layer Sundby-layer, that overlies the Stolleklint Clay - Age 56,0 -55,8 ma.

Fur-Formation

The shark teeth from the Fur-Formation are rarely found in the 60 meter thick diatomite called Mo-Clay. Single shark teeth are found throughout the whole formation. The striated cement stone from the level with volcanic ash layer -24 to -28, which is the lower part of the Fur Formation, have yield most shark teeth. Age 55,8-54.0 ma.

Røsnæs Clay Formation

The shark teeth from the Røsnæs Clay Formation at Grønbjerg Klint are from the Knudshoved Member, which is the oldest part bellow bed R1 (King 2016). Knudshoved Member overlies the Fur Formation, but on this locality the author has observed arround 6 meters of unknown layers, that expands the Fur Formation. On top of these new layers, redbrown Røsnæs Clay is visible. - Age 54.0-53,7 ma.


Fig. 3. Modified from Stokke et. al. 2020.

Grønbjerg Klint is a coast cliff in Northern Jutland on the Isle of Mors, near the small village of Flade (Fig. 1). During the Eocene, the Danish area was covered by the North Sea and clays and marls were deposited. When the Røsnæs Clay, Knudshoved Member was deposited, in a period where the English Channel was open, and the warm Atlantic Ocean made the sea level higher than when the Stolleklint Clay and Mo-clay sediments were deposited. The fine-grained clays of the Røsnæs Clay Formation and the Moclay are exposed in outcrops on the N-coast of Mors. Small outcrops of Stolleklint Clay and Holmehus Clay with the Paleocene-Eocene boundery have been observed on the beach at Sundby Klint. The Røsnæs Clay, Knudshoved Member, is only known from two other localities – Salgerhøj Klint, Mors (Håkansson & Sjørring 1982) and Knudeklint on the Isle of Fur (Heilmann-Clausen, C, Nielsen, O. B. and Gersner, P 1985).

In 2016 a geological mapping of the mo-clay deposit in an area north of Erslev with a view to assessing whether the area can be laid out as a raw material interest area in Region North Jutland's Mineral Resources Plan 2016. The mapping area is located approx. 1 km north of Erslev and borders southwest up to Øster Jølby. Here you can see what has been proposed as the eocene Røsnæs Ler over mo-clay in the northern part of the mapping area. This interpretation is based on a distinct green color of the lower moraine clay in borehole 37.1572.

Stratigraphy

The Røsnæs Clay Formation has been extensively logged by Heilmann-Clausen et al. (1985) and it is formally divided into seven lithological units named from the base, R1 to R6. Knudshoved Member (Heilmann-Clausen 1982) is restricted to the western Limfjord area.

At Grønbjerg Klint the Knudshoved Member layers is different than the layers on Knudeklinten or R1 in the rest of Denmark. The stratigraphy of the Knudshoved Member is illustrated by Heilmann-Clausen et al. 1985. At Grønbjerg Klint 4 meter is more or less exposed in a landslide west of the mo-clay cliff. It is also overlaying the moclay with 36 cm red-brown clay on top of the Grønbjerg Klint. The Knudshoved Member at Grønbjerg Klint, is red-brown, green, gray and grey-green, glauconitic fine-grained waxy clay, with light yellow and grey burrows preserved as small calcareous concretions.


Fig. 4. The landslide area at Grønbjerg Klint.


Fig. 5. The aurthor Henrik Madsen with the G2 layer at Grønbjerg Klint.

In the two measured profiles in the big landslide profile A, is 1,5 meter high and 15 meter in length. Furthermore a excavated ditch presents 2,4 meter green and brown clay below the glauconitic layer (G 1). In a slide a few meters behind and above this profile, the glauconitic layer G 2 is visible. Profile B is a 3,3 meter high and 10 meter wide profile, with the two glauconitic rich layers present (G 1 and G 2). At Grønbjerg Klint the Røsnæs Clay Formation, Knudshoved Member is overlain by up to two meters glacial sand and pebbels.


Fig. 6. Drawing of the layers at Grønbjerg. In total, the thickness of the clay is over 484 cm.

Nanoplankton sample
The nanoplankton sample 1 contains these dinoflagellates cysts: Spiniferites sp. and Deflandrea sp. which do not refer to any zone.

The nanoplankton sample 2 contains these dinoflagellates cysts: Wetzeliella sp., Eatonicysta ursulae, Deflandrea phosphoritica, Hystrichokolpoma cinctum, Thalassiphora pelagica, Areoligera cf. senonensis. These specimens are all characteristic for the Eatonicysta ursulae Zone (Heilmann-Clausen 1988). This zone is in the upper part of the Knudshoved Member and in R1, in the Røsnæs Clay Formation.

The NP sample also contains these dinoflagellates cysts: Areosphaeridium dictyoplokus, Cordosphaeridium cantharellus, Homotryblium plectilum/floripes, Glaphyrocysta semitecta, Phthanoperidinium comatum, Enneadocysta arcuata. The present of these specimens is strange because they occur later in the Eocene. They are known from the Lutetian Lillebælt Clay Formation. It is probably unlikely that it is Lillebælt Clay Formation, but more likely that the range of these specimens extends in to the Røsnæs Clay Formation.

The nanoplankton sample 3 contains this dinoflagellate cysts: Deflandrea oebisfeldensis. The sample belong to Zone 7 according to Heilmann-Clausen work (1985).
The sampling work was done by Karen Dybkjær at The Geological Survey of Denmark and Greenland (GEUS).


Material and methods

The present paper is based on one collection. The examined part of the collection consists of a total of more than 6000 teeth. The majority of the teeth are from Lamniformes. Of the total number of teeth, ?% are identified to genus or species, ?% are identified only to family or order, and the remaining ?% of the teeth are so damaged that identification was not attempted. The precise stratigraphic origin of these teeth is from layer bed G1 and bed G2. (GPS coordinates: 56°54'05.6"N 8°47'55.2"E. in October 2020, but will in time slide towards the Limfjord). The bulk material was collected in 2020 and a total of approximately 1100 kg of clay has been processed. 850 kg from bed G1 and 250 kg from bed G2. The clay was dried, dissolved in water three times and screen washed through two different mesh sizes, where the coarse sieve has 2.0 mm meshes, and the smallest one has 0.5 mm. The 250 kg from G2 was reduced to 2,0 kg. The reduced material contain a lot of glauconite, some pyrite, grains of sand and borrows of chalk. The residues were searched for sharkteeth by HM using a binocular microscope (Euromex). About ?? % of the teeth are identified to genus or species. All illustrated fossils are housed in the Natural History Museum of Denmark in Copenhagen under the catalogue numbers, DK xxxx. Teeth larger than 5 mm have been photographed with a Nikon D7000. Smaller teeth have been photographed with a binocular microscope. Besides the shark teeth, the bulk samples contained a large amount of teeth and bones of bony fish. They are not the subject of this work.

The The Røsnæs Clay is generally poor in fossil material, but extensive sampling in Røsnæs Clay Formation, Knudshoved Member in 2020, has revealed a variety of fossils including remains of bony fishes, sharks, rays and chimaera teeth. – Birdsbones, gastropods, bivalves, corals, ostracods, foraminiferas, seaurhcin and calcareous burrows produced by different animals are present both G1 and G2.


The fossils from sharks are mainly teeth, some dermal denticles, coprolites and few vertebrae. The morphology of the dermal denticles is very varied from one family to another and often from one genus to another within a family. Therefore one must be careful when denticle morphology is used to characterize a species. (Cappetta 2012).

Dermal denticles, coprolites and vertebrae are not used to characterize the species in this article.

Presevation of the fossils

Fig. 6 A: Cropolite from shark. B: Dermal denticle. C: Transparant tooth with fine details.


Order Lamniformes Berg 1958
Family Mitsukurinidae Jordan 1898
Genus Mitsukurina Jordan 1898 - Common name DK: Troldhajer / GB: Goblin shark
Mitsukurina sp
.


Fig. 1. Mitsukurina sp.. A, labial view; B, profile; C, lingual view; 10,0 mm high – Bed G2

Family Lamnidae Müller and Henle 1838

Genus Isurolamna Cappetta 1976 - Common name DK: Makrelhajer / GB: Macerel shark
Isurolamna inflata (Casier 1946
)


Fig. 2. Isurolamna inflata. A, labial view; B, profile; C, lingual view; 8,8 mm high – Bed G2

Family Lamnidae Müller and Henle 1838
Genus Macrorhizodus Glikman 1964b - Common name DK: Makrelhajer / GB: Macerel shark
Macrorhizodus sp


Fig. 9. Macrorhizodus sp.
A, labial view; B, profile; C, lingual view; 30,0 mm high – Bed G1
D, lingual view; E, labial view; F, profile; 20,0 mm high – Bed G1


Family Xiphodolamiidae Glickman 1964a
Genus Xiphodolamia Leidy 1877 - Common name DK: Makrelhajer / GB: Macerel shark
Xiphodolamia ensis (Casier 1946
)


Fig. 3. Xiphodolamia ensis. A, anterior tooth, labial view; 20,0mm high B, lateral tooth, lingual view; 8,0mm high – Bed G2

Family Alopiidae Bonaparte 1838
Genus Alopias Rafinesque 1810 - Common name DK: Rævehajer / GB: Thresher sharks
Alopias crochardi Ward 1978


Fig. 4. Alopias crochardi. A, labial view; B, profile; C, lingual view; 5,3 mm high – Bed G2
.

Family Alopiidae Bonaparte 1838
Genus Usakias Zhelezko & Kozlov 1999 - Common name DK: Rævehajer / GB: Thresher sharks
Usakias sp.



Fig. 5. Usakias sp. A, labial view; B, profile; C, lingual view; 10,0 mm wide – Bed G1

Family Odontaspididae Müller & Henle 1839
Genus Hypotodus Jaekel 1895 - Common name DK: Sandhajer / GB: Sand Tiger sharks
Hypotodus verticalis


Fig. 6. Hypotodus verticalis. A, labial view; B, lingual view; C, profile; 7,3 mm high – Bed G2.

Family Odontaspididae Müller & Henle
1839
Genus Brachycarcharias Cappetta & Nolf, 2005 - Common name DK: Sandhajer / GB: Sand Tiger sharks
Brachycarcharias lerichei Casier, 1946


Fig. 7. Brachycarcharias lerichei. A, labial view; B, profile; C, lingual view; 10,3 mm wide
– Bed G1

Family Odontaspididae Müller & Henle 1839
Genus Carcharias Rafinesque 1810 - Common name DK: Sandhajer / GB: Sand Tiger sharks
Carcharias sp.


Fig. 8. Carcharias sp.. A, labial view; B, profile; C, lingual view; upper lateral tooth. 7,3 mm high – Bed G2

Order Carcharhiniformes Compagno, 1977
Family
Scyliorhinidae Gill 1862
Genus
Megascyliorhinus Cappetta & Ward 1977 - Common name DK: Rødhajer / GB: Cat sharks
Megascyliorhinus cooperi


Fig. 10. Megascyliorhinus cooperi. A, labial view; B, profile; C, lingual view; lateral tooth. 5,3 mm high – Bed G2.

Family
Scyliorhinidae Gill 1862
Genus
Premontreia Cappetta 1992 - Common name DK: Rødhajer / GB: Cat sharks
Premontreia sp.

Fig. 10. Premontreia sp.. A, labial view; B, lingual view; 2,8 mm high – Bed G2.

Family Carcharhinidae Jordan & Everman 1896
Genus Physogaleus Cappetta 1980a -
Common name DK: Gråhajer / GB: Sharpnose sharks
Physogaleus secundus Winkler 1876b


Fig. 11. Physogaleus secundus. A, labial view; B, lingual view; 6,0 mm high – Bed G1

Family Triakidae GRAY 1851
Genus Triakis MÜLLER & HENLE 1838 -
Common name DK: Gråhajer / GB: Hound sharks
Triakis wardi
CAPPETTA, 1976


Fig. 12. Triakis wardi. A, labial view; B, lingual view;
1,4 mm high – Bed G2

Order Hexanchiformes F. de Buen, 1926
Family Chlamydoselachidae Garman 1884
Genus Chlamydoselachus Garman 1884 -
Common name DK: Kravehajer / GB: Frilled sharks
Chlamydoselachus sp.


Fig. 13. Chlamydoselachus sp. A, labial view; B, lingual view; C, detail of small cusps on the middle tooth;
D, basal view;. 5,0 mm high – Bed G1. Chlamydoselachus cf. fiedleri. E, labial view; 3,0 mm high Bed G2

Family Hexanchidae J. E. Gray, 1851
Genus Heptranchias Rafinesque, 1810 -
Common name DK: Seks- syvgællehajer / GB: Cow sharks
Heptranchias howelli


Fig. 14. Heptranchias howelliHeptranchias howelli. A, Lower tooth, labial view; 10,0 mm wide – Bed G2.
B, Upper tooth, labial view;
5,0 mm high – Bed G2

Family Hexanchidae J. E. Gray, 1851
Genus Hexanchus Rafinesque, 1810 -
Common name DK: Seks- syvgællehajer / GB: Cow sharks
Hexanchus agassizi


Fig. 15. Hexanchus agassizi. A, Lower tooth. lingual view; 12,0 mm wide – Bed G1.
B, Upper tooth, lingual view; 5,0 mm high – Bed G2.

Family Hexanchidae J. E. Gray, 1851
Genus Notorynchus Ayres, 1855 -
Common name DK: Seks- syvgællehajer / GB: Cow sharks
Notorynchus serratissimus
Agassiz, 1843


Fig. 16. Notorynchus serratissimus. A, Lower tooth. Lingual view; 10,0 mm wide – Bed G1.
B, Upper tooth. Lingual view; 5,0 mm high – Bed G1.

Order Squaliformes Goodrich, 1909
Family Centrophoridae Bleeker, 1859
Genus Centrophorus J. P. Müller & Henle, 1837 -
Common name DK: Pighajer / GB: Spiny dogfish
Centrophorus aff. granulosus


Fig. 17. Centrophorus aff. granulosus. A, labial view; B, lingual view; 3,5 mm high – Bed G1.

Family Squalidae Bonaparte, 1834
Genus Megasqualus Herman 1982 -
Common name DK: Pighajer / GB: Spiny dogfish
Megasqualus sp.


Fig. 18. Megasqualus sp. A, labial view; B, lingual view; 4,8 mm wide – Bed G2.


Fig. 19. Isistius trituratus. A, lingual view; B, labial view. 3,0 mm high – Bed G2.


Fig. 20. Eosqualiolus aturensis. A, labial view; B, lingual view. 1,7 mm high – Bed G2.
Dalatias sp. C. labial view; 1,7 mm high – Bed G1


Fig. 21. Squaliformes sp.. A, lingual view; B, labial view. 6,5 mm high – Bed G2.
Squaliformes sp.. C, labial view; D, lingual view. 2,8 mm high – Bed G1.


Fig. 22. Echinorhinus cf. priscus. A, lingual view; B, labial view. 5,3 mm wide – Bed G1.
Echinorhinus cf. priscus. C, Lateral tooth lingual view; D, labial view. 2,2 mm wide – Bed G1.


Fig. 23. Orthechinorhinus pfeili. A, labial view; B, lingual view; 1,1 mm high – Bed G2.


Fig. 24. Orthechinorhinus sp. A, labial view; B, profile; C, lingual view; 3,0 mm wide – Bed G2.


Fig. 25. Pristiophorus cf. lanceolatus. Rostral tooth A, labial view; B, lingual view;
C, profile view; 7,0 mm high – Bed G2


Fig. 26. Orectoloboides sp. A, labial view; B, Root from above; 3,3 mm high – Bed G2.
Orectoloboiformes sp. C, labial view; D, lingual view; 2,0 mm wide – Bed G2.


Fig. 27. Palaeorhincodon wardi. A, labial view; B, lingual view; C, profile view; 1,9 mm high
– Bed G2


Fig. 28. Heterodontus sp. A, Toot seen from above ; B, labial view; 13,0 mm wide – Bed G1.


Fig. 29. Heterodontus sp. A, lingual view; B, occlusal view; C, labial view 3,0 mm wide – Bed G2.


Fig. 30. Coupatezia miretrainensis A, lingual view; B, distal view; C, labial view.
3,0 mm high – Bed G2.



Order Chimaeriformes Obruchev 1953
Family Chimaeridae Bonaparte 1831
Genus Chimaera Linnaeus 1758
Elasmodus sp. Egerton 1843



Fig.XX.




Sharks from the Ølst Formation



Fig. 31. A Physogaleus sp. 0,8 cm. B Rhizoprionodon sp. 0,6 cm. C Dalatiid 0,5 cm. D Squalus sp. 0,3 cm.
E Squatina prima 0,6 cm. F Abdounia sp. 0,6 cm. G Pachygaleus lefevrei. 0,5 cm. H Pristiophorus sp. 0,5 cm.
I Oligodalatias sp. 0,5 cm. J Synechodus hesbayensis. 0,6 cm.



Fig. 32. Striatolamia macrota, A, labial view; B, lingual view; C, profile view; 3,5 cm.
Anomotodon sp., D, lingual view; E, labial view; F, profile view; - 1,0 cm .



Fig. 33. Cretalamna sp. A, labial view;, 3,0 cm.
Brachycarcharias lerichei B, lingual view; 1,5 cm.
Paleohypotodus rutoti C, labial view; 1,0 cm.



Fig. 34. Jaekelotodus sp. A, labial view; 2,5 cm.
Isurolamna affinis 1. B, labial view;1,0 cm.
Isurolamna affinis 2. C, labial view;1,3 cm.



Fig. 35. Ikke bestemt tand. A, labial view; B, lingual view; 1,4 cm .


Sharks from the Fur Formation

Fig. 36. 13 teeth from Striatolamia striata 2,5 cm.


Fig. 37. Carcharias sp.. A, labial view; 1,5 cm. Isurolamna affinis. B, labial view; 1,2 cm.
Odontaspis winkleri. C, profile view;
1,0 cm.


Fig. 38. Sylvesterilamia terentides. A, lingual view; 2,0 cm. Hypotodus verticalis. B, labial view; 1,5 cm.


Fig.39. Palaeohypotodus rutoti. A, labial view; 2,0 cm. Odontaspididae. B, labial view; 2,0 cm..

 
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