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Moltrasio Formation

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Coordinates: 46°00′N 9°06′E / 46.0°N 9.1°E / 46.0; 9.1
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Moltrasio Formation
Stratigraphic range: Middle Sinemurian-Lower Pliensbachian
~196–188 Ma
Outcrop
TypeGeological formation
Unit ofMonte Generoso Basin
Sub-unitsOsteno Outcrop
UnderliesDomaro Formation
OverliesSedrina Limestone
Lithology
PrimaryLimestone
Location
Coordinates46°00′N 9°06′E / 46.0°N 9.1°E / 46.0; 9.1
Approximate paleocoordinates33°12′N 15°36′E / 33.2°N 15.6°E / 33.2; 15.6
RegionLombardy
Country Italy
Type section
Named forMoltrasio
Named byAntonio Stoppani[1]
Year defined1857
Moltrasio Formation is located in Italy
Moltrasio Formation
Moltrasio Formation (Italy)
Moltrasio Formation is located in Lombardy
Moltrasio Formation
Moltrasio Formation (Lombardy)

The Moltrasio Formation also known as the Lombardische Kieselkalk Formation is a geological formation in Italy. This Formation mostly developed in the Lower or Middle Sinemurian stage of the Lower Jurassic, where on the Lombardian basin tectonic activity modified the current marine and terrestrial habitats.[2] Here it developed a series of marine-related depositional settings, represented by an outcrop of 550–600 m of grey Calcarenites and Calcilutites with chert lenses and marly interbeds, that recovers the Sedrina, Moltrasio and Domaro Formations.[2] This was mostly due to the post-Triassic crisis, that was linked locally to tectonics.[3] The Moltrasio Formation is considered a continuation of the Sedrina Limestone and the Hettangian Albenza Formation, and was probably a shallow water succession, developed on the passive margin of the westernmost Southern Alps.[3][4] It is known due to the exquisite preservation observed on the Outcrop in Osteno, where several kinds of marine biota have been recovered.[5]

Fossils

Exceptional fossilization

Apart from the Eocene of Monte Bolca, the Sinemurian of Osteno is the only fossil deposit in Italy in which soft bodies are preserved. The Osteno site was discovered in 1964. It was recovered from a series of 6 metres (20 ft) package of fine laminated, gray, spongiolitic, micritic limestone.[6] Coroniceras bisulcatum allowed to date the outcrop as the Bucklandi zone, lower Sinemurian.[6] The outcrop is a good documentation of a particularly complete fauna and flora of the Lower Jurassic which is not exactly common in the Southern Alps.[6] The Osteno outcrop, part of the formation, is worldwide known due to the exceptional preservation of mostly marine biota, including rare fossilized components, helping to understand the ecosystems of the local Sinemurian margin of the Monte Generoso Basin.[7] The high local variety of fossils found is most likely due to unique conditions of preservation, where phosphatized soft tissues have not been observed in any fish or polychaetes, but they are common in crustaceans (33%) and also occur in a smaller percentage of teuthids (14%).[8] Soft part preservation through phosphatization in this deposit includes the muscles and branchia of Crustaceans, fish tissues, and the digestive tracts of coleoids, polychaetes, and nematodes. These fossils are interpreted as having been preserved in a stagnant, restricted basin with anoxic conditions likely within the sediment pore waters.[5]

Nematoida

Genus Species Material Location Notes Images

Eophasma[9][5][6]

Eophasma jurasicum

  • A complete specimen

Osteno Outcrop.[9]

A nematode, type member of the family Eophasmidae inside Desmoscolecida.[10] A rare find, since nematode fossils are absent in most Mesozoic marine rocks.[9]

Annelida

Genus Species Material Location Notes Images

Melanoraphia[11][5][6]

Melanoraphia maculata

  • A nearly complete specimen

Osteno Outcrop.[11]

A polychaete, member of the group Phyllodocemorpha with incertade sedis assignation. This polychaete was probably an open swimmer more than a subtrate dweller.[11]

Crustacea

Genus Species Material Location Notes Images

Aeger[12][13][5][6]

  • Aeger foesteri
  • Aeger muensteri
  • Aeger robustus
  • Aeger rostrospinatus
  • Aeger elongatus
  • Aeger macropus
  • Multiple specimens, complete and incomplete

Osteno Outcrop.[13]

A decapod, type member of the family Aegeridae. This genus is the most abundant local crustacean, and was a shrimp-like creature that was probably necrophagous.[13]

Coleia[12][14][5][15][16][6]

  • Coleia vialiii
  • Coleia medilerranea
  • Coleia cf. antiqua
  • Coleia pinnnai
  • Coleia popeyei
  • Multiple complete specimens

Osteno Outcrop.[13]

A decapod, type member of the family Coleiidae. Probably a bottom dweller predatory crustacean.[14]

Pseudoglyphea[12][14][5][16][6]

  • Pseudoglyphea amylochelis
  • Multiple complete specimens

Osteno Outcrop.[13]

A decapod, member of the family Litogastroidae. Probably a bottom dweller predatory crustacean.[14]

Mecochirus[12][17][14][5][16][6]

  • Mecochirus germari
  • Multiple complete specimens

Osteno Outcrop.[13]

A decapod, member of the family Mecochiridae. Rather rare compared to other local crustacean genera.

Palaeastacus[12][17][14][16][18]

  • Palaeastacus meyeri
  • Multiple complete specimens

Osteno Outcrop.[13]

A decapod, member of the family Erymidae. The species was originally included in the genus Eryma as E. meyeri, although the specimens reveal morphological characters diagnostic of Palaeastacus.[18]

Eryma[12][17][14][16][18][19]

  • Eryma sinemuriana
  • Multiple complete specimens

Osteno Outcrop.[13]

A decapod, type member of the family Erymidae. The species was originally identified as Pustulina sinemuriana.[18]

Xiphosurida

Genus Species Material Location Notes Images

Ostenolimulus[20]

  • Ostenolimulus latus
  • A nearly complete specimen

Osteno Outcrop.[20]

A horseshoe crab, member of the family Limulidae. This genus represents the oldest Jurassic limulid and only the second xiphosuran known from Italy.[20] Also indicates that this family were a diverse and widespread clade during the Jurassic.[20]

Thylacocephala

Genus Species Material Location Notes Images

Ostenocaris[21][5][6][22]

Ostenocaris cypriformis

  • Multiple specimens, complete and incomplete

Osteno Outcrop.[21]

A thylacocephalan, type member of the family Ostenocarididae inside Conchyliocarida.[23] Originally Interpreted as a bizarre Cirriped.[24] Ostenocaris is the most common fossil of the formation, and the main identified thylacocephalan from the formation. In the first interpretations, the genus was shown as a filter-feeding organism, which used the cephalic sac as a burrowing organ to ensure adhesion to the substrate.[24] Based on the presence of Coprolites associated to the genus, with abundant masses of alimentary residues (hooks of cephalopods, vertebrates, remains of Crustacea) in the stomach of these organisms, Ostenocaris cypriformis was probably a necrophagous organism, and the cephalic sac can be tentatively interpreted as being a burrowing organ employed during the search for food, or as an organ of locomotion with intrinsic motility.[25]

Cephalopoda

Genus Species Material Location Notes Images

Arietites[5][6]

  • Arietites bucklandi
  • Shells

Osteno outcrop.[5][6]

An ammonitidan, type member of the family Arietitidae inside Psiloceratoidea. The main ammonite identified locally.

Coroniceras[5][16][6]

  • Coroniceras bisulcatum
  • Shells

Osteno outcrop.[5][6]

An ammonitidan, member of the family Arietitidae inside Psiloceratoidea. It was less common than other ammonites, although index for some locations.

Oxynoticeras[5][6]

  • Oxynoticeras oxynotum
  • Shells

Osteno outcrop.[5][6]

An ammonitidan, type member of the family Oxynoticeratidae inside Ammonitida. It was not the most abundant ammonite, but was rather common.

Angulaticeras[5][16][6]

  • Angulaticeras sp.
  • Shells

Osteno outcrop.[5][6]

An ammonitidan, member of the family Schlotheimiidae inside Psiloceratoidea. It was not the most abundant ammonite, but was rather common.

Ectocentrites[5][16][6]

  • Ectocentrites sp.
  • Shells

Osteno outcrop.[5][6]

An ammonitidan, member of the family Lytoceratidae inside Lytoceratina. It was not the most abundant ammonite, but was rather common.

Ostenoteuthis[5][26][27][16][6]

  • Ostenoteuthis siroi
  • A complete specimen with soft tissue

Osteno outcrop.[5][6]

A coleoid, type member of the family Ostenoteuthidae. A unique group of coeloids, only found at this location. Coleoids with ten arms each bearing pairs of hooks, Ostenoteuthis measure between 18 and 30 cm length.[27]

Uncinoteuthis[27][6]

  • Uncinoteuthis cuvieri
  • A complete specimen with soft tissue

Osteno outcrop.[5][6]

A coleoid, member of the family Ostenoteuthidae. A unique group of coeloids, only found at this location.[27]

Echinoderms

Genus Species Material Location Notes Images

Palaeocoma[16][6]

  • Palaeocoma milleri
  • Multiple specimens

Mount Campo dei Fiori.[6]

An ophiuridan, member of the family Ophiodermatidae inside Ophiodermatina. Extant tropical species like Ophioderma are benthic predators and scavengers that show the same short spines seen in Palaeocoma.[6]

Hemichordata

Genus Species Material Location Notes Images

Megaderaion[28]

Megaderaion sinemuriense

  • A nearly complete specimen with soft tissue

Osteno Outcrop.[28]

An acorn worm, member of the family Harrimaniidae inside Enteropneusta. It was a large sized member of its family. This genus probably lived linked to sand bottoms, where it made burrows to hide and find food.[28]

Chondrichthyes

Genus Species Material Location Notes Images

Ostenoselache[16][6]

Ostenoselache stenosoma

  • Multiple specimens

Osteno Outcrop.[16]

An euselachiian, type member of the family Ostenoselachidae inside Elasmobranchii. A unique genus of shark, only found in the Osteno Formation. With an elongated eel-shaped morphology, the specimens found measure at least 240 mm in length, with a neurocranium with a long, complex rostrum.[16] It has been suggested it was an animal able to produce electric shocks, probably to kill prey.[16]

Squaloraja[29][16]

Squaloraja polyspondyla

  • Multiple specimens

Osteno Outcrop.[16]

A chimaerid, type member of the family Squalorajidae inside Squalorajoidei. This genus belongs to a lineage of ray-like chimaeras.

Myriacanthidae[29]

Myriacanthidae indet

  • Multiple specimens

Osteno Outcrop.[16]

A chimaerid, member of the family Myriacanthidae inside Chimaeriformes.

Hybodontiformes[29]

Hybodontiformes indet

  • Multiple specimens

Osteno Outcrop.[16]

A shark, member of the family Hybodontiformes.

Palaeospinax[30][16]

Palaeospinax pinnai

  • Multiple specimens

Osteno Outcrop.[16]

A Shark, type member of the family Palaeospinacidae inside Synechodontiformes. Open water swimmer.

Actinopterygii

Genus Species Material Location Notes Images

Cosmolepis[16][31][6]

Cosmolepis ornatus

  • Multiple specimens

Osteno Outcrop.[31]

A primitive actinopterygiian, member of the order Palaeonisciformes. A late surviving representative of the family.

Pteroniscus[16][31][6]

Pteroniscus sp.

  • Multiple specimens

Osteno Outcrop.[31]

A primitive actinopterygiian, member of the order Palaeonisciformes. A complicated genus, whose modern status is rather dubious.

Peripeltopleurus[16][31][6]

Peripeltopleurus sp.

  • Multiple specimens

Osteno Outcrop.[31]

A primitive actinopterygiian, member of the family Peltopleuridae inside Neopterygii. A genus related with the Epicontinental deposition

Dapedium[16][31][6]

Dapedium sp.

  • Multiple specimens

Osteno Outcrop.[31]

A primitive actinopterygiian, type member of the family Dapediidae inside Holostei. Probably a Coral Environment wanderer.

Furo[16][31][6]

Furo sp.

  • Multiple specimens

Osteno Outcrop.[31]

A primitive actinopterygiian, type member of the family Furidae inside Ionoscopiformes. Open water swimmer, probably forming schools.

Pholidophorus[16][31][6]

Pholidophorus bechei

  • Multiple specimens

Osteno Outcrop.[31]

A primitive actinopterygiian, type member of the family Pholidophoridae inside Teleostei. Open water swimmer, probably forming schools. It is the main fish recovered on the formation.

Pholidolepis[16][31][6]

Pholidolepis sp.

  • Multiple specimens

Osteno Outcrop.[31]

A primitive Actinopterygiian, member of the family Pholidophoridae inside Teleostei. Open water swimmer, probably forming schools.

Sarcopterygii

Genus Species Material Location Notes Images

Undina[5][6]

Undina (Holophagus) cf. gulo

  • Scales

Osteno Outcrop.[31]

A Coelacanth, member of the family Latimeriidae inside Coelacanthiformes. Isolated scales of coelacanths analogous to the genus Holophagus are quite frequent on the Osteno deposits. A series of teeth can also be identified to this genus.

Plants

Genus Species Material Location Notes Images

Equisitites[32][6]

Equisitites bunburyanus

  • Stems

Osteno Outcrop.[31]

A Horsetail, member of the family Equisetaceae inside Equisetales. A freshwater-related plant, that grew as fast as modern bamboo on tropical settings.

Pachypteris[32][6]

Pachypteris cf. rhomboidalis

  • Fronds

Osteno Outcrop.[31]

A tree fern, member of the family Umkomasiaceae inside Peltaspermales. Fronds of large tree ferns, related to humid ecosystems.

Otozamites[32][6]

  • Otozamites bunburyanus
  • Otozamites sp.
  • Fronds

Osteno Outcrop.[31]

A spermatopsidan, member of the family Bennettitales inside Bennettitopsida. Cycad-like flora, common on dry settings.

Zamites[32][6]

Zamites sp.

  • Fronds

Osteno Outcrop.[31]

A spermatopsidan, member of the family Bennettitales inside Bennettitopsida. Cycad-like flora, common on dry settings.

Williamsonia[32][6]

Williamsonia sp.

  • Fronds

Osteno Outcrop.[31]

A spermatopsidan, member of the family Bennettitales inside Bennettitopsida. Cycad-like flora, common on dry settings.

Pagiophyllum[32][6]

  • Pagiophyllum sp. A
  • Pagiophyllum sp. B
  • Fronds

Osteno Outcrop.[31]

A coniferophytan, member of the family Araucariaceae inside Pinopsida.

Brachyphyllum[32][6]

  • Brachyphyllum sp. A
  • Brachyphyllum sp. B
  • Brachyphyllum sp. C
  • Fronds

Osteno Outcrop.[31]

A coniferophytan, member of the family Cheirolepidiaceae inside Pinopsida.

See also

References

  1. ^ Stoppani A. (1857). Studi geologici e paleontologici sulla Lombardia. 461 pp. Tipografia Turati, Milano
  2. ^ a b Muttoni, G., Erba, E., Kent, D. V., & Bachtadse, V. (2005). Mesozoic Alpine facies deposition as a result of past latitudinal plate motion. Nature, 434(7029), 59-63.
  3. ^ a b Jadoul, F., & Galli, M. T. (2008). The Hettangian shallow water carbonates after the Triassic-Jurassic biocalcification crisis: The Albenza Formation in the western Southern Alps. Rivista Italiana di Paleontologia e Stratigrafia, 114(3), 453-470.
  4. ^ Sarti, M., Bosellini, A., & Winterer, E. L. (1992). Basin Geometry and Architecture of a Tethyan Passive Margin, Southern Alps, Italy: Implications for Rifting Mechanisms: Chapter 13: African and Mediterranean Margins.
  5. ^ a b c d e f g h i j k l m n o p q r s t u v w Pinna, G. (1985). Exceptional preservation in the Jurassic of Osteno. Philosophical Transactions of the Royal Society of London. B, Biological Sciences, 311(1148), 171-180.
  6. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq Pinna, G. (2000). Die Fossillagerstätte im Sinemurium (Lias) von Osteno, Italien. In Europäische Fossillagerstätten (pp. 91-136). Springer, Berlin, Heidelberg.
  7. ^ Tang, C. M. (2002). Osteno: Jurassic Preservation. Exceptional Fossil Preservation: A Unique View on the Evolution of Marine Life, 251.
  8. ^ Wilby, P. R., & Briggs, D. E. (1997). Taxonomic trends in the resolution of detail preserved in fossil phosphatized soft tissues. Geobios, 30, 493-502.
  9. ^ a b c Arduini, P., Pinna, G., & Teruzzi, G. (1983). Eophasma jurassicum ngn sp., a new fossil nematode of the Sinemurian of Osteno in Lombardy. Atti della Società italiana di scienze naturali e del museo civico di storia naturale di Milano, 124(1-2), 61-64.
  10. ^ Poinar, G. O. (2011). The Evolutionary History of Nematodes: As revealed in stone, amber and mummies. Nematology Monographs and Perspectives. 9. Brill Publishers. doi:10.1163/9789047428664. ISBN 9789047428664.
  11. ^ a b c Arduini, P., Pinna, G., & TERRUZZI, G. (1982). Melanoraphia maculata ngn sp., a new fossil polychaete of the Sinemurian of Osteno in Lombardy. Atti della Società italiana di scienze naturali e del museo civico di storia naturale di Milano, 123(4), 462-468.
  12. ^ a b c d e f Pinna, G. 1967. Decouverte d’une nouvelle faune a crustaces du Sinemurien inferieur dans la region du Lac Ceresio (Lombardie, Italie). Atti Soc. It. Sci. nat. Museo Milano 106, 183—185.
  13. ^ a b c d e f g h Garassino, A., & Teruzzi, G. (1990). The genus Aeger Münster, 1839 in the Sinemurian of Osteno in Lombardy (Crustacea, Decapoda). Atti della società italiana di scienze naturali e del museo civico di storia naturale di Milano, 131(5), 105-136.
  14. ^ a b c d e f g Pinna, G. 1969. Due nuovi esemplari di Coleia vialiii Pinna, del Sinemuriano inferiore di Osteno in Lombardia (Crustacea Decapoda). Ann. Mus. St. nat. Genova 77, 626—632
  15. ^ Teruzzi, G. (1990). The genus «Coleia» Broderip, 1835 (Crustacea, Decapoda) in the Sinemurian of Osteno in Lombardy. Atti della Società italiana di Scienze naturali e del Museo Civico di Storia naturale di Milano, 131(4), 85-104.
  16. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa Duffin, C. J. (1998). Ostenoselache stenosoma ngn sp., a new neoselachian shark from the Sinemurian (Early Jurassic) of Osteno (Lombardy, Italy). Società Italiana di Scienze Naturali; Museo Civico di Storia Naturale di Milano.
  17. ^ a b c Garassino A . 1996. The family Erymidac Van Straelen. 1924 and the superfamily Glypheoidea Zittel, ISSS in the Sincmurian of Osteno in Lombardy (Crustacea. Decapoda). Aai soc. it. Sci.rwt. Museo civ. stor. mu. Milano. Milano.135 (11): 333-373.
  18. ^ a b c d Devillez, J., & Charbonnier, S. (2017). The genus Eryma Meyer, 1840 (Crustacea: Decapoda: Erymidae): new synonyms, systematic and stratigraphic implicationsLe genre Eryma Meyer, 1840 (Crustacea: Decapoda: Erymidae): nouveaux synonymes, implications systématique et stratigraphique. Bulletin de la Société géologique de France, 188(3).
  19. ^ Devillez, J., & Charbonnier, S. (2019). Review of the Early and Middle Jurassic erymid lobsters (Crustacea: Decapoda) Révision des Érymides (Crustacea: Decapoda) du Jurassique inférieur et moyen. Bulletin de la Société géologique de France, 190(1).
  20. ^ a b c d Lamsdell, J. C.; Teruzzi, G.; Pasini, G.; Garassino, A. (2021). "A new limulid (Chelicerata, Xiphosurida) from the Lower Jurassic (Sinemurian) of Osteno, NW Italy". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 300 (1): 1–10. doi:10.1127/njgpa/2021/0974.
  21. ^ a b Arduini, P., Pinna, G., & Teruzzi, G. (1984). Ostenocaris nom. nov. pro Ostenia. Atli del/a Societcl Iraliwzn di Sc: ienze Naturali e del Museo Civico di Storia Naturale di Milano, Miiano. l25, 1-2.
  22. ^ Arduini, P., Pinna, G., & Teruzzi, G. (1982). Il giacimento sinemuriano di Osteno in Lombardia. Palaeontology, Essential of Historical Geology. Mucchi, Modena, 495-522.
  23. ^ Pinna, G., Arduini, P., Pesarini, C. & Teruzzi, G. 1982 Thylacocephala: una nuova classe di crostacei fossili. AttiSoc. It. Sci. nat. Museo Milano 123, 469-482
  24. ^ a b ÐÐ PINNA, G., & TERUZZI, G. (1980). A new and unusual lower Jurassic cirripede from Osteno in Lombardy: Ostenia cypriformis ngn sp. (preliminary note). Atti della SocietaÁ Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, 121, 360-370.
  25. ^ Pinna, G., Arduini, P., Pesarini, C., & Teruzzi, G. (1985). Some controversial aspects of the morphology and anatomy of Ostenocaris cypriformis (Crustacea, Thylacocephala). Earth and Environmental Science Transactions of The Royal Society of Edinburgh, 76(2-3), 373-379.
  26. ^ Pinna, Ð. 1972. Rinvenimento di un raro cefalopode coleoideo nel giacimento sinemuriano di Osteno in Lombardia. Atti de la SocietaÁ Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, 113, 141±149.
  27. ^ a b c d Garassino, A., & Donovan, D. T. (2000). A new family of coleoids from the Lower Jurassic of Osteno, Northern Italy. Palaeontology, 43(6), 1019-1038.
  28. ^ a b c Arduini, P. (1981). Megaderaion sinemuriense ngn sp., a new fossil enteropneust of the Sinemurian of Osteno in Lombardy.
  29. ^ a b c Duffin, C. J. (1991). A myriacanthid holocephalan (Chondrichthyes) from the Sinemurian (Lower Jurassic) of Osteno (Lombardy, Italy). Atti della Società italiana di scienze naturali e del museo civico di storia naturale di Milano, 132(23), 293-308.
  30. ^ Duffin, C. J. (1987). ‘’Palaeospinax pinnai n. sp.’’, a new Palaeospinacid shark from the Sinemuvian (Lower Jurassic) of Osteno (Lombardy, Italy). Atti della Società italiana di scienze naturali e del museo civico di storia naturale di Milano, 128(1-2), 185-202.
  31. ^ a b c d e f g h i j k l m n o p q r s t u v DUFFIN, C.J. & PATTERSON, C. (in press): The Jurassic fishes of Osteno. Palaeocronache. Milano
  32. ^ a b c d e f g BONCI, M. C., & VANNUCCI, G. (1986). I vegetali sinemuriani di Osteno (Lombardia). Atti della Società italiana di scienze naturali e del museo civico di storia naturale di Milano, 127(1-2), 107-127.
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