Calcare di Sogno

The Calcare di Sogno ("Sogno Limestone"; also known as the Sogno Formation) is a geological formation in Italy, dated to roughly between 183-181 million years ago and covering the Toarcian stages of the Jurassic Period in the Mesozoic Era.[1] Thallatosuchian remains are known from the formation.

Calcare di Sogno
Stratigraphic range: Toarcian
~183–181 Ma
↓
TypeGeological formation
UnderliesFormazione delle Radiolariti
OverliesCalcare di Domaro, Calcare di Morbio, Unnamed limestones[note 1]
ThicknessTypically 120–140 m (390–460 ft)
East and west 70–100 m (230–330 ft)
Lithology
PrimaryMarl, marly limestone & abundance of clay
Secondary: Alternation of marly limestones and marls, presence of graded Chalcudites
OtherLimestones with nodules of flint & subordinate marls
Location
Coordinates45.8°N 9.3°E / 45.8; 9.3
Approximate paleocoordinates33.4°N 18.9°E / 33.4; 18.9
RegionLecco Province
Country Italy
Type section
Named forSogno
Named byGaetani & Poliani
Calcare di Sogno (Italy)
Calcare di Sogno (Lombardy)

Description

The formation is characterized by a disposition of regional deposition equivalent to the German Posidonia Shale, with a benthonic setting and deposition trends, mostly populated by marine fauna.[2] The environment of the formation was related to a marginal marine deposit, with probably epicontinetal deposition from near land environments, being connected to the central European seas of the Toarcian.[3][4][5]

Fossil content

Flora

Several plant leaves and fragments of wood wheren´t identified.[6]

Genus Species Stratigraphic position Material Notes Images

Ginkgo[6]
  • Ginkgo digitata
  • Mount Brughetto
  • Mount Cornizzolo

Leaves

Affinities with the Ginkgoaceae. Arboreal plants related to the modern Ginkgo species.

Pagiophyllum[6]
  • Pagiophyllum kurri
  • Pagiophyllum rotzoanum
  • Mount Brughetto
  • Mount Cornizzolo

Leaves

Affinities with the Araucariaceae. Arbustive to arboreal plants with several leaf morphotypes, probably from nearshore environments.

Molluscs
GenusSpeciesStratigraphic positionMaterialNotesImages
Hildaites[1][2] Hildaites sp.
  • Mount Brughetto
  • Mount Cornizzolo

Especimens

A Hildoceratidae ammonite

Cornaptychus[1][2]

Cornaptychus lythensis
  • Mount Brughetto
  • Mount Cornizzolo

Especimens

An indeterminate ammonite. Some of the specimens found are very fragmentary, making its identification complex.[2]

Dactylioceras[1][2]

Dactylioceras polymorphus
  • Mount Brughetto
  • Mount Cornizzolo

Especimens

Type member Dactylioceratinae family of Ammonites. A common mediterranean genera, found on deposits along all europe.

Mesodactylites[1][2]
  • Mesodactylites sapphicus
  • Mesodactylites sp.
  • Mount Brughetto
  • Mount Cornizzolo

Especimens

A Nodicoeloceratinae ammonite

Harpoceras[1][2]

Harpoceras sp.
  • Mount Brughetto
  • Mount Cornizzolo

Especimens

Type reprensentative genus of the Harpoceratinae ammonite family

Collina[1][2]

Collina gemma
  • Mount Brughetto
  • Mount Cornizzolo

Especimens

A Dactylioceratidae ammonite. Present and abundant on the Mediterranean Toarcian realm.

Arthropods
Genus Species Stratigraphic position Material Notes Images

Proeryon[1][7]

Proeryon hartmanni
  • Mount Brughetto
  • Mount Cornizzolo

Various specimens

A Erymidae Decapodan Crustacean common on the mediterranean rocks. Frequent presence of Burrows Thalassinoides with fossilised specimens nearby. A complete Seafloor section was fossilized.

Gabaleryon[8]

Gabaleryon garassinoi
  • Mount Brughetto
  • Mount Cornizzolo

Various specimens

A Coleiidae Decapodan. Was confussed with Proeryon hartmanni specimens.

?Antrimpos[8]

?Antrimpos sp.
  • Mount Cornizzolo

Single specimen

A Penaeidae Decapodan.

?Etallonia[8]

?Etallonia sp.
  • Mount Cornizzolo

Single specimen

An Axiidae Decapodan.

Archaeopalinurus[7]

Archaeopalinurus cfr. A. levis
  • Mount Brughetto
  • Mount Cornizzolo

Various specimens

A Palinuroidean Decapodan.

Uncina[9]

Uncina alpina
  • Mount Brughetto
  • Mount Cornizzolo

Various Specimens

An Astacidean Decapodan of the family Uncinidae. A large decapodan, with sizes up to 40 cm.

Fish
Genus Species Stratigraphic position Material Notes Images

Pholidophorus [6][10]
  • Pholidophorus sp.

Monte Cornizzolo

Several Especimens

Type member of the family Pholidophoridae inside Pachycormiformes. A small sized fish, mostly related to marine deposits, associated with various predatory behaviours, including coeloids and Crocodrylomorphs.

Leptolepis[6][10]
  • Leptolepis coryphaenoides
  • Leptolepis sp.

Monte Cornizzolo

+100 specimens

Type member of the family Leptolepidae inside Leptolepiformes. It is the most abundant fish found on the formation.

Pachycormus[6][10]
  • Pachycormus sp.

Monte Cornizzolo

Several Especimens

The main member of the family Pachycormidae inside Pachycormiformes. Large sized fish, able to reach near 1.4 m long.

Crocodyliformes
Genus Species Location Material Notes Images

cf.Pelagosaurus[10]

cf. Pelagosaurus sp.
  • Monte Cornizzolo

Various specimens MSNM V4012, MSNM V4013.

A Thalattosuchian marine crocodrylomorph of the family Teleosauridae.The specimens found where of small size, with several characters such as opened neurocentral vertebral sutures and non sutured caudal pleurapophyses, that led to expeculate a possible juvenile or subadult status.

See also

Notes and references

Notes
  1. Bioturbed hazel-gray limestones in planar layers of about 20 cm, with concentration of gray flint and gray & reddish marls, along with calcareous marl.[1]

References
  1. CARTA GEOLOGICA D’ITALIA 1:50.000 - CATALOGO DELLE FORMAZIONE. Formazione di Sogno.SERVIZIO GEOLOGICO - CONSIGLIO NAZIONALE DELLE RICERCHE - COMMISSIONE ITALIANA DI STRATIGRAFIA: http://www.isprambiente.gov.it/files/pubblicazioni/periodicitecnici/quaderni-sgi/quad7/form5.pdf
  2. GAETANI M. & POLIANI G. (1978) - Il Toarciano ed il Giurassico medio in Albenza (Bergamo). Riv. It. Pal. Strat., 84 (2): 349-382, 5 figg., 2 tavv., Milano.
  3. GAETANI M. & ERBA E. (1990) - Il Bacino Lombardo: un sistema paleo alto/fossa in un margine continentale passivo durante il Giurassico. In: JADOUL F. & MASSIOTTA P. (Eds.): «La geologia italiana degli anni ’90 - Guida alle escursioni pre-congresso». 75° Congr. Naz. Soc. Geol. It.: Escursione A3, pp. 23, 14 figg., 1 tav., Milano
  4. DEL SERE M. (1966) - «Lagenidea» del Lias dell’Albenza (Bergamo). Riv. It. Pal. Strat., 72 (1): 147-188, 2 figg.,4 tavv., Milano.
  5. BERSEZIO R., JADOUL F. & CHINAGLIA N. (1997) - Geological map of the Norian-Jurassic succession of Southern Alps north of Bergamo: explanatory notes. Boll. Soc. Geol. It., 116 (2): 363-378, 1 carta geol., Roma
  6. A. Tintori. 1977. Toarcian fishes from the Lombardian basin. Bolletino della Società Paleontologica Italiana 16:143-152
  7. Garassino, A., & Gironi, B. (2005). Proeryon hartmanni (v. Meyer, 1835)(Crustacea, Decapoda, Eryonoidea) and Archaeopalinurus cfr. A. levis Pinna, 1974 (Crustacea, Decapoda, Palinuroidea) from the Lower Jurassic (Toarcian) of Cesana Brianza-Suello (Lecco, N Italy). Atti della Società italiana di Scienze naturali e del Museo civico di Storia naturale in Milano, 146(1), 53-68.
  8. Audo, D., Williams, M., Charbonnier, S., & Schweigert, G. (2017). Gabaleryon, a new genus of widespread early Toarcian polychelidan lobsters. Journal of Systematic Palaeontology, 15(3), 205-222.
  9. Schweigert, G., Garassino, A., Hall, R. L., Hauff, R. B. & Karasawa, H. 2003. The lobster genus Uncina Quenstedt, 1851 (Crustacea: Decapoda: Astacidea: Uncinidae) from the Lower Jurassic. Stuttgarter Beiträge zur Naturkunde, Serie B, 332, 1-43
  10. M. Delfino and C. Dal Sasso. 2006. Marine reptiles (Thalattosuchia) from the Early Jurassic of Lombardy (northern Italy). Geobios 39:346-354

Bibliography
  • Weishampel, David B.; Peter Dodson, and Halszka Osmólska (eds.). 2004. The Dinosauria, 2nd edition, 1–880. Berkeley: University of California Press. Accessed 2019-02-21. ISBN 0-520-24209-2
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