Aalenian

Aalenian
174.1 ± 1.0 – 170.3 ± 1.4 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
The Aalenian GSSP in Spain
Chronology
Key events in the Jurassic This box: -200 — – -195 — – -190 — – -185 — – -180 — – -175 — – -170 — – -165 — – -160 — – -155 — – -150 — – -145 — – M e s o z o i c T J u r a s s i c K L T E a r l y M i d d l e L a t e E K Rhaetian Hettangian Sinemurian Pliensbachian Toarcian Aalenian Bajocian Bathonian Callovian Oxfordian Kimmeridgian Tithonian Berriasian how to approximate the timescale of key Jurassic events. Vertical axis: millions of years ago.
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	FAD of Ammonites Leioceras opalinum and Leioceras lineatum
Lower boundary GSSP	Fuentelsaz, Spain 41°10′15″N 1°50′00″W / 41.1708°N 1.8333°W
GSSP ratified	2000[1]
Upper boundary definition	FAD of the Ammonites Hyperlioceras mundum, Hyperlioceras furcatum, Braunsina aspera, and Braunsina elegantula
Upper boundary GSSP	Cabo Mondego, Portugal 40°11′57″N 8°54′15″W / 40.1992°N 8.9042°W
GSSP ratified	1996[2]

The Aalenian ( /ɑːˈliːniən/) 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.^[3]

Stratigraphic definitions

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 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.^[4] 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:

• zone of Graphoceras concavum
• zone of Brasilia bradfordensis
• zone of Ludwigia murchisonae
• zone of Leioceras opalinum

Palaeontology

†Ammonitids

†Ammonitids of the Aalenian
Taxa	Presence	Location	Description	Images
Abbasites Abbasites platystomus	Confirmed.[5]		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.
Ancolioceras	Confirmed.[5]
Asthenoceras	Confirmed.[5]
Bradfordia	Confirmed.[5]
Brasilia	Confirmed.[5]
Bredyia	Confirmed.[5]
Canavarella	Confirmed.[5]
Constileioceras	Confirmed.[5]
Cylioceras	Confirmed.[5]
Euaptetoceras	Confirmed.[5]
Eudmetoceras	Confirmed.[5]
Euhoploceras	Confirmed.[5]
Fontannesia	Confirmed.[5]
Graphoceras	Confirmed.[5]
Haplopleuroceras	Confirmed.[5]
Hyperlioceras	Confirmed.[5]
Leioceras	Confirmed.[5]
Ludwigia	Confirmed.[5]
Malladaites	Confirmed.[5]
Padragosiceras	Confirmed.[5]
Parammatoceras	Confirmed.[5]
Planammatoceras	Confirmed.[5]
Praestrigites	Confirmed.[5]
Pseudammatoceras	Confirmed.[5]
Puchenquia	Confirmed.[5]
Reynesella	Confirmed.[5]
Sonninia	Confirmed.[5]
Spinammatoceras	Confirmed.[5]
Staufenia	Confirmed.[5]
Stephanoceras	Confirmed.[5]
Trilobiticeras	Confirmed.[5]
Tugurites	Confirmed.[5]

†Belemnites

Belemnites of the Aalenian
Taxa	Presence	Location	Description	Images
Belemnopsis	Confirmed.[5]			Belemnites.
Holcobelus	Confirmed.[5]
Homaloteuthis	Confirmed.[5]
Megateuthis Megateuthis gigantea	Confirmed.[5]		This Eurasian species was the largest known Belemnite and could grow to lengths of up to 10 feet (3.0 m).
Paramegateuthis	Confirmed.[5]
Rhabdobelus	Confirmed.[5]
Sachsibelus	Confirmed.[5]

Bony fish

Ichthyosaurs

†Thalattosuchians

Dinosaurs

Sauropods

Theropods

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.

References

Notes

Literature

• 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 links

• GeoWhen Database - Aalenian
• Lower Jurassic timescale, at the website of the subcommission for stratigraphic information of the ICS
• Stratigraphic chart of the Upper and Lower Jurassic, at the website of Norges Network of offshore records of geology and stratigraphy