Psiloceras

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Psiloceras
Temporal range: Hettangian [1]
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Psiloceras laevis - Naturhistorisches Museum, Braunschweig, Germany - DSC05130.JPG
Psiloceras laevis
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass:† Ammonoidea
Order:† Ammonitida
Family:† Psiloceratidae
Genus:† Psiloceras
Hyatt, 1867
Species [2]
  • P. planorbis(Sowerby, 1824) (type) synonym Ammonites planorbis, A. sampsoni, P. sampsoni
  • P. becki
  • P. brevicellatum
  • P. calliphylloides
  • P. calliphyllum Neumayr, 1879 synonym Aegoceras calliphyllum
  • P. costosum
  • P. distinctum
  • P. erugatum
  • P. hagenowi
  • P. marcouxiGuex, Taylor, Rakus & Bucher, 1998
  • P. minillaensisvon Hillebrandt, 2000
  • P. naumanni
  • P. pacificumGuex, 1980
  • P. polymorphumGuex, 1980
  • P. plicatulum(Quenstedt, 1883) synonym Ammonites plicatulus
  • P. primocostatumvon Hillebrandt, 2000
  • P. psilonotum
  • P. sampsoni
  • P. spelaeGuex, Taylor, Rakus & Bucher, 1998
  • P. spelae tirolicumvon Hillebrandt & Krystyn, 2009
  • P. tenerum
  • P. tibeticumYin et al., 2007
  • P. tilmanniLange, 1925

Psiloceras is an extinct genus of ammonite. Psiloceras is among the earliest known Jurassic ammonites, and the appearance of the earliest Psiloceras species form the definition for the base of the Jurassic. Unlike most earlier ammonites, which had complex shell shapes and ornamentation, Psiloceras had a smooth shell. [3] [4]

Contents

Taxonomy

Almost all ammonites, with the sole exemption of a few members of the family Psiloceratidae, including Psiloceras were wiped out at the Triassic–Jurassic extinction event (201.3 million years ago). [3]

Most authors assume that Psiloceras descended from the Phyllocerataceae. P. spelae is probably the earliest species of Psiloceras. [5] [6]

Biostratigraphic significance

The International Commission on Stratigraphy (ICS) has assigned the First Appearance Datum of the Psiloceras spela-group as the defining biological marker for the start of the Hettangian, 201.3 ± 0.2 million years ago, the earliest stage of the Jurassic, with the Global Boundary Stratotype Section and Point (GSSP) located at Kuhjoch pass, Karwendel Mountains, Northern Calcareous Alps, Austria, which was ratified in 2010. [7] The base of the Jurassic in Britain was historically defined by the first appearance of the ammonite Psiloceras planorbis.

Distribution

Jurassic of Argentina, Austria, Canada, China, France, Germany, New Zealand, Spain, the United Kingdom, United States [2] Psiloceras fossils are commonly found at Watchet, Somerset, England. Here smooth-shelled Psiloceras planorbis (along with other species) are to be found as usually flattened fossils in the Blue Lias. [8]

Related Research Articles

The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.

The Early Jurassic Epoch is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event, 201.3 Ma, and ends at the start of the Middle Jurassic 174.1 Ma.

Aalenian First age of the Middle Jurassic

The Aalenian is a subdivision of the Middle Jurassic Epoch/Series of the geologic timescale that extends from about 174.1 Ma to about 170.3 Ma. It was preceded by the Toarcian and succeeded by the Bajocian.

The Rhaetian is the latest age of the Triassic Period or the uppermost stage of the Triassic System. It was preceded by the Norian and succeeded by the Hettangian. The base of the Rhaetian lacks a formal GSSP, though candidate sections include Steinbergkogel in Austria and Pignola-Abriola in Italy. The end of the Rhaetian is more well-defined. According to the current ICS system, the Rhaetian ended 201.3 ± 0.2 Ma.

Anisian

In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 247.2 million years ago until 242 million years ago. The Anisian Age succeeds the Olenekian Age and precedes the Ladinian Age.

Carnian First age of the Late Triassic epoch

The Carnian is the lowermost stage of the Upper Triassic Series. It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by the Norian. Its boundaries are not characterized by major extinctions or biotic turnovers, but a climatic event occurred during the Carnian and seems to be associated with important extinctions or biotic radiations.

The Hettangian is the earliest age and lowest stage of the Jurassic Period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma. The Hettangian follows the Rhaetian and is followed by the Sinemurian.

Sinemurian Second age of the Early Jurassic

In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma. The Sinemurian is preceded by the Hettangian and is followed by the Pliensbachian.

The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between 237 Ma and 201.3 Ma. It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. The corresponding series of rock beds is known as the Upper Triassic. The Late Triassic is divided into the Carnian, Norian and Rhaetian Ages.

Ladinian Age in the Middle Triassic

The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between 242 Ma and ~237 Ma. The Ladinian was preceded by the Anisian and succeeded by the Carnian.

The Norian is a division of the Triassic Period. It has the rank of an age (geochronology) or stage (chronostratigraphy). The Norian lasted from ~227 to 208.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.

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

Stratesaurus is an extinct genus of small-bodied rhomaleosaurid plesiosaur known from the Early Jurassic period of the United Kingdom. It contains a single species, S. taylori.

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

Eoplesiosaurus is an extinct genus of basal plesiosauroid known from the Early Jurassic period of the United Kingdom. It contains a single species, E. antiquior.

Waterloo Bay

Waterloo Bay is an area of foreshore in Larne on the east coast of County Antrim, Northern Ireland. It is of particular interest to geologists because it provides a clear, complete and accessible example of the sequences from Upper Triassic to Lower Jurassic, when the rock types changed from land to marine.

The Gabbs Formation is a geologic formation in Nevada. It preserves fossils dating back to the Late Triassic and Early Jurassic periods, and is one of the few formations in the United States known to include the Triassic-Jurassic boundary. In 2007, an exposure of the Gabbs Formation at New York Canyon was proposed a candidate GSSP for the Hettangian stage, the first stage of the Jurassic. However, the New York Canyon section was ultimately not selected as Hettangian GSSP, which instead went to the Kuhjoch section of Austria in 2010.

The Kendlbach Formation is a Late Triassic to Early Jurassic (Hettangian) geological formation in Austria and Italy. It contains the Global Boundary Stratotype Section and Point (GSSP) for the Hettangian stage at the Kuhjoch section in the Karwendel Mountains of Austria.

The Oberrhaet Formation, also known as the Oberrhaet Limestone, is a Late Triassic (Rhaetian-age) geological formation in Austria. It is a unit of massive dark grey bioclastic limestones, found within the Northern Calcareous Alps. The Oberrhaet Limestone was originally a series of reefs which developed on the northwest edge of the Eiberg Basin, a narrow marine waterway extending along the northwestern tip of the Neotethys Ocean. The center of the Eiberg Basin is nowadays preserved as the Eiberg Member of the Kössen Formation, which was deposited southeast of the Oberrhaet Limestone and interfingers with it in many areas. The Oberrhaet Limestone was very similar to the Dachstein Limestone, which represented carbonate platforms and reefs on the southeast edge of the Eiberg Basin. The most prominent components of the reefs were giant frond-like colonies of Retiophyllia, a scleractinian coral.

<i>Dracoraptor</i> Genus of reptiles (fossil)

Dracoraptor is a genus of coelophysoid dinosaur that lived during the Hettangian stage of the Early Jurassic Period of what is now Wales dated at 201.3 ± 0.2 million years old.

<i>Oncodella</i> Extinct genus of jawless fishes

Oncodella is an extinct genus of Late Triassic conodont. The genus was given the type species Oncodella idiodentica by Mosher (1968), on the basis of fossils from the Late Triassic of Austria. However, Mosher (1969) later revised the species name to Oncodella paucidentata, since identical fossils from the same area were previously given the name Hindeodella paucidentata by Mostler (1967).

Paleontology of Wales is paleontological research occurring in Wales.

References

  1. ↑ Sepkoski, Jack (2002). "Sepkoski's Online Genus Database" . Retrieved 2014-05-28.{{cite journal}}: Cite journal requires |journal= (help)
  2. 1 2 Paleobiology Database - Psiloceras. 2014-05-29.
  3. 1 2 "Psiloceras pacificum". New Mexico Museum of Natural History and Science. Spring 2008. Archived from the original on 10 May 2015. Retrieved 5 August 2013.
  4. ↑ Howarth, Michael K. (2013). "Chapter 4: Psiloceratoidea, Eodoceratoidea, Hildoceratoidea.". In Selden, Paul A. (ed.). Treatise Online, Part L (Revised) Mollusca 4, vol. 3B, Triassic and Jurassic Ammonoidea. Lawrence, Kansas: Paleontological Institute, University of Kansas. doi:10.17161/to.v0i0.4441.
  5. ↑ Hillebrandt, von, A. "Paleobiogeography and Relationship of South American Hettangian (Lower Jurassic) ammonites" (PDF). Institut für Angewandte Geowissenschaften II. Retrieved 4 August 2013.
  6. ↑ Hillebrandt, von, A.; Krystyn, L. (2009). "On the oldest Jurassic ammonites of Europe (Northern Calcareous Alps, Austria) and their global significance" (PDF). N. Jb. Geol. Paläont. Abh. 253 (2–3): 163–195. doi:10.1127/0077-7749/2009/0253-0163. Archived from the original (PDF) on 2013-12-09.
  7. ↑ Hillebrandt, A.v.; Krystyn, L.; Kürschner, W.M.; Bonis, N.R.; Ruhl, M.; Richoz, S.; Schobben, M. A. N.; Urlichs, M.; Bown, P.R.; Kment, K.; McRoberts, C.A. (2013-09-01). "The Global Stratotype Sections and Point (GSSP) for the base of the Jurassic System at Kuhjoch (Karwendel Mountains, Northern Calcareous Alps, Tyrol, Austria)". Episodes. 36 (3): 162–198. doi: 10.18814/epiiugs/2013/v36i3/001 . ISSN   0705-3797.
  8. ↑ Davies, G. M. (1964). The Dorset Coast. London: Adam and Charles Black.


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