Kilmaluag Formation

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Kilmaluag Formation
Stratigraphic range: Bathonian
~167.4–166.5  Ma
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Kilmaluag Formation Lava.jpg
Sediments of the Kilmaluag Formation overlain by Paleogene lava on the Isle of Skye
Type Formation
Unit of Great Estuarine Group
Underlies Skudiburgh Formation
Overlies Duntulm Formation
ThicknessUp to 25 m (82 ft)
Lithology
Primary Calcareous mudstone, limestone
Location
Coordinates 57°12′N6°06′W / 57.2°N 6.1°W / 57.2; -6.1
Approximate paleocoordinates 46°24′N4°12′E / 46.4°N 4.2°E / 46.4; 4.2
CountryFlag of the United Kingdom.svg  UK
ExtentThroughout Inner Hebrides, including Isle of Skye, Isle of Muck, and Isle of Eigg
Type section
Named for Kilmaluag Bay in the North of Skye
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Kilmaluag Formation (the United Kingdom)
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Kilmaluag Formation (Scotland)

The Kilmaluag Formation is a Middle Jurassic geologic formation in Scotland. It was formerly known as the Ostracod Limestone for preserving an abundance of fossil freshwater/low salinity ostracods. Gastropods, bivalves, trace fossil burrows, and vertebrate fossil remains have also been recorded from the formation. Vertebrate fossils include fish, crocodylomorphs, mammals, small reptiles, amphibians, theropod and sauropod dinosaurs and pterosaurs. [1]

Contents

Geology

The Kilmaluag Formation was deposited during the Bathonian stage ~167 million years ago and is part of the Great Estuarine Group. Like other rock formations within the Great Estuarine Group, the Kilmaluag Formation is composed of a series of fine grained sandstones, silts, mudstones, and dolomitised limestones. The sediments were deposited in a freshwater influenced low salinity closed lagoonal palaeoenvironment subject to lagoon margin transgressions and regressions. During regressions, sediment abandonment ensued and is indicated by the deposition of dolomitised limestones, in which large desiccation cracks can be observed. In contrast, during transgressions, sediment influxes and increases in water depth led to the deposition of finer grained silts and muds. Occasional shoreline conditions are indicated by rippled sandstones.

The Kilmaluag Formation is divided into two facies: the clastic facies deposited in the Sea of the Hebrides basin of northern Skye, and argillaceous limestone facies present in the Inner Hebrides basin, present on the Straithaird peninsula, Isles of Eigg and Muck. [2]

Fossils

In many beds, freshwater gastropods and bivalves can be found, including Viviparus and Unio, and freshwater ostracods such as Darwinula and Theriosynoecum. [3] [2]

Many vertebrate fossils have been recorded from the argillaceous facies of Straithaird since the 1970s, when the first mammal fossil were found by Michael Waldman. He returned with fellow palaeontologist Robert Savage and named two new species from the area: the Docodont Borealestes serendipitus, and the tritylodontid, Stereognathus hebridicus [4] (although S. hebridicus is now thought to be a junior synonym to S. ooliticus [5] ). Many other fossils are found in the Kilmaluag, including members of other Mesozoic mammal groups, turtles, reptiles, and amphibians. [1] [6] Notable vertebrate fossil recent discoveries in the Kilmaluag Formation include Palaeoxonodon ooliticus [7] and Wareolestes rex. [8] A notable dinosaur find includes the tooth of a sauropod dinosaur. [9] The most recent scientifically pre-published find includes a pterosaur found in 2006. [10]

Comparisons between the Kilmaluag Formation and other British and global Middle Jurassic localities suggest that the fauna represented is globally significant, due to the scarcity of similarly aged sediments. [1] The fauna is a subset of the animals represented in the Forest Marble Formation in England, but fossils in the Kilmaliag Formation are substantially more complete.

Exposures of the Kilmaluag Formation are protected by law as SSSIs (Site of Special Scientific Interest) and under the new Scottish NCO (Nature Conservation Order), thus no public collection is permitted. Most fossils found to date are held in the collections of the National Museum of Scotland.

Vertebrate paleobiota

Amphibians

Amphibians
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
cf. Anoualerpeton cf A. priscumPair of articulated premaxilla [11] Albanerpetontid
Marmorerpeton M. wakeiCladach a'GhlinneSeveral partial skeletons [12] Salamander
Caudata [6] IndeterminateCladach a'GhlinneReferred to as "Kirtlington 'Salamander A'"

Turtles

Turtles
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Eileanchelys [13] E. waldmaniCladach a'GhlinnePartial skull and association of 5-6 individuals with skull and shell material.A mesochelyidian
Testudines [6] IndeterminateCladach a'Ghlinne

Lepidosauromorphs

Lepidosauromorphs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Balnealacerta B. silvestris"right dentary, partial right maxilla and a partial right prefrontal"Squamate
Bellairsia B. gracilis"dentary and parts of other bones scattered on a slab"Stem-squamate
Bellairsia skull diagram.png
Marmoretta [14] M. oxoniensisCladach a'GhlinnePartial associated skeletonStem-lepidosauromorph
Marmoretta.svg
cf. Paramacellodus [6] IndeterminateCladach a'GhlinneSquamate
Parviraptor [6] IndeterminateCladach a'GhlinneSquamate
IndeterminateCladach a'GhlinneDistinct from other taxa known from the British Bathonian, new gen et sp indet.

Choristoderes

Choristoderes
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Cteniogenys [6] IndeterminateCladach a'GhlinnePartial skull

Dinosaurs

Fossilised dinosaur footprints in a Kilmaluag Formation rock from the Isle of Skye The world's smallest dinosaur footprint, the Hunterian Museum, Glasgow..JPG
Fossilised dinosaur footprints in a Kilmaluag Formation rock from the Isle of Skye
Dinosaurs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Eusauropoda [9] IndeterminateCladach a'GhlinneTooth

Pterosaurs

Pterosaurs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Ceoptera [15] C. evansaeCladach a'GhlinneA partial skeleton

Mammaliamorphs

Mammaliamorphs
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
Borealestes [16] B. serendipitusCladach a'GhlinneToothed jaw fragments, referred partial skeleton [17] Docodont
Borealestes.jpg
B. cuillinensisCladach a'GhlinnePartial skeleton
Krusatodon [6] IndeterminateCladach a'GhlinneMolar
Palaeoxonodon [7] P. ooliticusCladach a'GhlinneThree partial left dentaries [18] Amphitheriid
Palaeoxonodon.jpg
Stereognathus S. ooliticus [5] Cladach a'GhlinnePartial toothed jaw, isolated teeth Tritylodont
Wareolestes [8] W. rexPartial left dentary Morganucodont

See also

Related Research Articles

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The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 161.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations containing land animal fossils include the Forest Marble Formation in England, the Kilmaluag Formation in Scotland, the Calcaire de Caen of France, the Daohugou Beds in China, the Itat Formation in Russia, the Tiouraren Formation of Niger, and the Isalo III Formation of western Madagascar.

<i>Karaurus</i> Extinct genus of amphibians

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<span class="mw-page-title-main">Goniopholididae</span> Extinct family of reptiles

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<span class="mw-page-title-main">Amphitheriidae</span> Extinct family of mammals

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Eileanchelys is an extinct genus of primitive turtle from the Middle Jurassic (Bathonian) period some 164 million years ago of Britain. Only one species is recorded, Eileanchelys waldmani. It is the best-represented turtle from the Middle Jurassic, because of the amount of specimens that can be assigned to it. The turtle is also one of the oldest turtles ever found to be aquatic, and might represent a milestone in turtle evolution.

<i>Anoualerpeton</i> Extinct genus of amphibians

Anoualerpeton is an extinct genus of lissamphibian in the family Albanerpetontidae. It is the oldest and most primitive albanerpetontid known. Fossils have been found of two different species, Anoualerpeton priscus from the Middle Jurassic (Bathonian) aged Forest Marble and Kilmaluag formations of England and Scotland, and Anoualerpeton unicus from Late Jurassic-Early Cretaceous (Tithonian-Berriasian) Ksar Metlili Formation of Morocco. A. unicus is the only named albanerpetontid from Gondwana.

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<span class="mw-page-title-main">Karauridae</span> Extinct family of amphibians

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<i>Marmoretta</i> Extinct genus of reptiles

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<i>Stereognathus</i> Extinct genus of mammaliamorphs

Stereognathus is an extinct genus of tritylodontid cynodonts from the Middle Jurassic of the United Kingdom. There is a single named species: S. ooliticus, named after the Great Oolite deposits of England. A second species, S. hebridicus, was named after the Hebrides in Scotland, where it was found; it was synonymized with S. ooliticus in 2017.

<i>Allkaruen</i> Genus of breviquartossan pterosaur from the Jurassic period

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<i>Borealestes</i> Extinct genus of mammaliaforms

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Wareolestes rex is a mammaliaform from the Middle Jurassic (Bathonian) rocks of England and Scotland. It was originally known from isolated teeth from England, before a more complete jaw with teeth was found in the Kilmaluag Formation of Skye, Scotland.

<i>Palaeoxonodon</i> Extinct genus of mammals

Palaeoxonodon is an extinct genus of cladotherian mammal from the Middle Jurassic of England and Scotland.

Krusatodon is a genus of extinct docodont mammaliaform from the Middle Jurassic of the United Kingdom. It is known from remains found in the Forest Marble Formation and also from the Kilmaluag Formation on the Isle of Skye, Scotland.

Dobunnodon its an extinct genus of docodont from the Middle Jurassic (Bathonian) Forest Marble Formation of England, first discovered in Oxfordshire near the village of Kirtlington. The type species, D. mussettae, was originally named as a species of Borealestes in 2003.

Michael Waldman is a British palaeontologist known for his work on fossil fish, mammals, and reptiles. He also discovered the globally important fossil site of Cladach a'Ghlinne, near Elgol on the Isle of Skye, Scotland. This site exposes the Kilmaluag Formation and provides a valuable record of Middle Jurassic ecosystems. During the 1970s he visited the site several times with fellow palaeontologist Robert Savage. The fossil turtle Eileanchelys waldmani was named after Michael in recognition of his notable contribution to palaeontology.

<i>Bellairsia</i> Extinct genus of reptiles

Bellairsia is an extinct genus of stem-squamate known from a single species, Bellairsia gracilis, from the Middle Jurassic (Bathonian) of England and Scotland. It is amongst the oldest squamates known. It was originally described in 1998 by Susan E. Evans from disarticulated individual bones, including the holotype dentary, collected from the Forest Marble Formation in Kirtlington Quarry, Oxfordshire, England. It was named in honor of British herpetologist and vertebrate anatomist Angus Bellairs. In 2022, a partial 70% complete skeleton was described from the equivalently aged Kilmaluag Formation of the Isle of Skye, Scotland. The partial skeleton had an estimated snout-vent length of around 6–7 centimetres (2.4–2.8 in). While originally considered a member of Scincomorpha, the 2022 study recovered it to be a stem-group squamate, with the phylogeny recovering it as part of a weakly supported clade also containing Huehuecuetzpalli and Oculudentavis.

Ceoptera is an extinct genus of darwinopteran pterosaur from the Middle Jurassic Kilmaluag Formation of Scotland. The genus contains a single species, C. evansae, known from a partial skeleton.It is the only pterosaur from Kilmaluag Formation. Ceoptera represents the second pterosaur named from Scotland, after Dearc in 2022.

References

  1. 1 2 3 Panciroli E, RBJ Benson, S Walsh, RJ Butler, TA Castro, MEH Jones, SE. Evans. 2020. Diverse vertebrate assemblage of the Kilmaluag Formation (Bathonian, Middle Jurassic) of Skye, Scotland. Earth and Environmental Transactions of the Royal Society of Edinburgh [online] 1-22
  2. 1 2 Andrews, J. E. 1985 The sedimentary facies of a late Bathonian regressive episode: the Kilmaluag and Skudiburgh Formations of the Great Estuarine Group, Inner Hebrides, Scotland. Journal of the Geological Society of London, 142, 1119-37.
  3. ↑ Barron, A. J. M., Lott, G. K. and Riding, J. B. 2012 Stratigraphical framework for the Middle Jurassic strata of Great Britain and the adjoining continental shelf. British Geological Survey Research Report, RR/11/06. British Geological Survey, Keyworth
  4. ↑ Waldman, M and Savage, R.J.G 1972 The first Jurassic mammal from Scotland. Journal of the Geological Society of London 128:119-125
  5. 1 2 Panciroli, Elsa; Walsh, Stig; Fraser, Nicholas C.; Brusatte, Stephen L.; Corfe, Ian (2017-09-03). "A reassessment of the postcanine dentition and systematics of the tritylodontid Stereognathus (Cynodontia, Tritylodontidae, Mammaliamorpha), from the Middle Jurassic of the United Kingdom". Journal of Vertebrate Paleontology. 37 (5): e1351448. Bibcode:2017JVPal..37E1448P. doi: 10.1080/02724634.2017.1351448 . hdl: 10138/230155 . ISSN   0272-4634.
  6. 1 2 3 4 5 6 7 Evans, S., Barrett, P., Hilton, J., Butler R.J., Jones, M.E.H., Liang, M-.M., Parrish, J.C., Rayfield, E.J., Sigogneau-Russell, D., and Underwood, C.J. 2005. The Middle Jurassic vertebrate assemblage of Skye, Scotland. 36-39. In P. Barrett and S. Evans (eds). Proceedings of the Ninth Symposium on Mesozoic Terrestrial Ecosystems and Biota. Natural History Museum, London.
  7. 1 2 Close, Roger A.; Davis, Brian M.; Walsh, Stig; Wolniewicz, Andrzej S.; Friedman, Matt; Benson, Roger B. J. (2015-11-13). "A lower jaw of Palaeoxonodon from the Middle Jurassic of the Isle of Skye, Scotland, sheds new light on the diversity of British stem therians". Palaeontology. 59 (1): 155–169. doi: 10.1111/pala.12218 . ISSN   0031-0239. S2CID   85925908.
  8. 1 2 Panciroli, Elsa; Benson, Roger B. J.; Walsh, Stig (2017-05-04). "The dentary of Wareolestes rex (Megazostrodontidae): a new specimen from Scotland and implications for morganucodontan tooth replacement". Papers in Palaeontology. 3 (3): 373–386. Bibcode:2017PPal....3..373P. doi:10.1002/spp2.1079. ISSN   2056-2802. S2CID   90894840.
  9. 1 2 Barrett, Paul M. (March 2006). "A sauropod dinosaur tooth from the Middle Jurassic of Skye, Scotland". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 97 (1): 25–29. doi:10.1017/S0263593300001383. ISSN   1473-7116. S2CID   129163193.
  10. ↑ Martin-Silverstone, Elizabeth; Unwin, David M.; Cuff, Andrew R.; Brown, Emily E.; Allington-Jones, Lu; Barrett, Paul M. (2022-02-16). "A new pterosaur from Skye, Scotland and the early diversification of flying reptiles". doi:10.1101/2022.02.14.480264. S2CID   246945717 . Retrieved 2023-07-01.
  11. ↑ Panciroli, Elsa; Benson, Roger B. J.; Walsh, Stig; Butler, Richard J.; Castro, Tiago Andrade; Jones, Marc E. H.; Evans, Susan E. (2020). "Diverse vertebrate assemblage of the Kilmaluag Formation (Bathonian, Middle Jurassic) of Skye, Scotland". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 111 (3): 135–156. Bibcode:2020EESTR.111..135P. doi: 10.1017/S1755691020000055 . ISSN   1755-6910.
  12. ↑ Jones, M. E. H.; Benson, R. B. J.; Skutschas, P.; Hill, L.; Panciroli, E.; Schmitt, A. D.; Walsh, S. A.; Evans, S. E. (2022). "Middle Jurassic fossils document an early stage in salamander evolution". Proceedings of the National Academy of Sciences of the United States of America. 119 (30): e2114100119. Bibcode:2022PNAS..11914100J. doi: 10.1073/pnas.2114100119 . PMC   9335269 . PMID   35858401.
  13. ↑ Anquetin, J.; Barrett, P.M.; Jones, M.E.H.; Moore-Fay, S.; Evans, S.E. (2009). "A new stem turtle from the Middle Jurassic of Scotland: new insights into the evolution and palaeoecology of basal turtles". Proceedings of the Royal Society B: Biological Sciences . 276 (1658): 879–886. doi:10.1098/rspb.2008.1429. ISSN   0962-8452. PMC   2664364 . PMID   19019789.
  14. ↑ Waldman, M.; Evans, S. E. (1994). "Lepidosauromorph reptiles from the Middle Jurassic of Skye". Zoological Journal of the Linnean Society. 112 (1–2): 135–150. doi:10.1111/j.1096-3642.1994.tb00315.x.
  15. ↑ Martin-Silverstone, Elizabeth; Unwin, David M.; Cuff, Andrew R.; Brown, Emily E.; Allington-Jones, Lu; Barrett, Paul M. (2024-02-05). "A new pterosaur from the Middle Jurassic of Skye, Scotland and the early diversification of flying reptile". Journal of Vertebrate Paleontology. doi: 10.1080/02724634.2023.2298741 . ISSN   0272-4634.
  16. ↑ WALDMAN, MICHAEL; SAVAGE, ROBERT JOSEPH GAY (March 1972). "The first Jurassic mammal from Scotland". Journal of the Geological Society. 128 (2): 119–125. Bibcode:1972JGSoc.128..119W. doi:10.1144/gsjgs.128.2.0119. ISSN   0016-7649. S2CID   128622858.
  17. ↑ Panciroli, Elsa; Schultz, Julia A.; Luo, Zhe-Xi (2018-08-31). "Morphology of the petrosal and stapes of Borealestes (Mammaliaformes, Docodonta) from the Middle Jurassic of Skye, Scotland". Papers in Palaeontology. 5: 139–156. doi: 10.1002/spp2.1233 . hdl: 20.500.11820/4c32b6c2-db3a-4e4d-8c46-cedc3245fac1 . ISSN   2056-2802.
  18. ↑ Panciroli, Elsa; Benson, Roger; Butler, Richard (2018). "New partial dentaries of amphitheriid mammalian Palaeoxonodon ooliticus from Scotland, and posterior dentary morphology in early cladotherians". Acta Palaeontologica Polonica. 63. doi: 10.4202/app.00434.2017 . ISSN   0567-7920.
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