Aalenian

System/
Period
Series/
Epoch
Stage/
Age
Age (Ma)
Cretaceous Lower/
Early
Berriasian younger
Jurassic Upper/
Late
Tithonian ~145.0 152.1
Kimmeridgian 152.1 157.3
Oxfordian 157.3 163.5
Middle Callovian 163.5 166.1
Bathonian 166.1 168.3
Bajocian 168.3 170.3
Aalenian 170.3 174.1
Lower/
Early
Toarcian 174.1 182.7
Pliensbachian 182.7 190.8
Sinemurian 190.8 199.3
Hettangian 199.3 201.3
Triassic Upper/
Late
Rhaetian older
Subdivision of the Jurassic system
according to the ICS, as of 2020.[1]

The Aalenian ( /ɑːˈlniən/) 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 (million years ago). It was preceded by the Toarcian and succeeded by the Bajocian.[2]

Stratigraphic definitionsEdit

The Aalenian takes its name from the town of Aalen, some 70 km east of Stuttgart in Germany. The town lies at the northeastern end of the Swabian Jura. The name Aalenian was introduced in scientific literature by Swiss geologist Karl Mayer-Eymar in 1864.

 
The Aalenian GSSP in Spain

The base of the Aalenian is defined as the place in the stratigraphic column where the ammonite genus Leioceras first appears. The global reference profile (GSSP) is located 500 meters north of the village of Fuentelsaz in the Spanish province of Guadalajara.[3] The top of the Aalenian (the base of the Bajocian) is at the first appearance of ammonite genus Hyperlioceras.

In the Tethys domain, the Aalenian contains four ammonite biozones:

PalaeontologyEdit

†AmmonitidsEdit

Ammonitids of the Aalenian
Taxa Presence Location Description Images
Confirmed.[4] The only known species in this Alaskan genus. Abbasites is believed to be ancestral to the ammonite family Otoitidae.
 
Life restorations of two different ammonite genera.
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]

†BelemnitesEdit

Belemnites of the Aalenian
Taxa Presence Location Description Images
Confirmed.[4]
 
Belemnites.
Confirmed.[4]
Confirmed.[4]
Confirmed.[4] This Eurasian species was the largest known Belemnite and could grow to lengths of up to 10 feet (3.0 m).
Confirmed.[4]
Confirmed.[4]
Confirmed.[4]

Bony fishEdit

Bony fish of the Albian
Taxa Presence Location Description Images
Pliensbachian-Aalenian Europe (France, Belgium, Luxembourg, United Kingdom, Germany, Italy) and North America (Canada) A saurichthyiid actinopterygian.

IchthyosaursEdit

Ichthyosaurs of the Toarcian
Taxa Presence Location Description Images
Europe

†ThalattosuchiansEdit

Thalattosuchia of the Aalenian
Taxa Presence Location Description Images
Switzerland; Morocco; England; France; Germany

DinosaursEdit

SauropodsEdit

Sauropods of the Aalenian
Taxa Presence Location Description Images

"Bothriospondylus" madagascariensis

possibly a new genus

TheropodsEdit

Theropods of the Aalenian
Taxa Presence Location Description Images

Asfaltovenator

Toarcian-Bajocian Cañadón Asfalto Basin, Patagonia, Argentina A large basal carnosaur. The unique combination of characteristics seen in Asfaltovenator may indicate megalosauroids and allosauroids shared a common ancestor not shared with Coelurosauria.

Condorraptor

Aalenian-Bajocian Cañadón Asfalto Basin, Patagonia, Argentina It was among the earliest large South American theropods.
 
Condorraptor.

Magnosaurus

Aalenian-Bajocian Dorset, England Magnosaurus was one of the first megalosaurids to evolve.
 
Magnosaurus.

Shidaisaurus

Early Aalenian Chuanjie Formation, Yunnan, China A genus of early medium sized metriacanthosaurine allosauroid, estimated from around 6 to over 7 meters long and from 700 up to 950 kilograms in mass.

ReferencesEdit

NotesEdit

  1. ^ http://www.stratigraphy.org/index.php/ics-chart-timescale
  2. ^ See Gradstein et al. (2004) for a detailed version of the geologic timescale
  3. ^ Cresta et al. (2001)
  4. ^ 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 Sepkoski (2002)

LiteratureEdit

  • Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.
  • Cresta, S.; Goy, A.; Ureta, S.; Arias, C.; Barrón, E.; Bernad, J.; Canales, M.L.; García-Joral, F.; García-Romero, E.; Gialanella, P.R.; Gómez, J.J.; González, J.A.; Herrero, C.; Martínez, G.; Osete, M.L.; Perilli, N. & Villalaín, J.J.; 2001: The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic), Episodes 24(3): pp 166–175.
  • Mayer-Eymar, K.; 1864: Tableau synchronistique des terrains jurassiques. 1 Tabelle, Zürich. (in French)
  • Sepkoski, J.; 2002: A compendium of fossil marine animal genera (entry on cephalopoda), Bulletins of American Paleontology 364, p 560.

External linksEdit