Search the Community
Showing results for tags 'aalenian'.
-
Leioceras comptocostosum var. subfalcatum (Chandler & Callomon 2009)
Ludwigia posted a fossil in Ammonoids
This is a variation of a relatively newly created species collected at the type locality by the first author of the following work. Literature: Chandler, R.B. & Callomon, J. 2009. The Inferior Oolite at Coombe Quarry, near Mapperton, Dorset, and a new Middle Jurassic ammonite faunal horizon, Aa-3b, Leioceras comptocostosum n.biosp. in the Scissum Zone of the Lower Aalenian. Proceedings of the Dorset Natural History and Archaeological Society. -
Leioceras comptocostosum var. subacutum (Chandler & Callomon 2009)
Ludwigia posted a fossil in Ammonoids
This is a variation of a relatively newly created species collected at the type locality by the first author of the following work. Literature: Chandler, R.B. & Callomon, J. 2009. The Inferior Oolite at Coombe Quarry, near Mapperton, Dorset, and a new Middle Jurassic ammonite faunal horizon, Aa-3b, Leioceras comptocostosum n.biosp. in the Scissum Zone of the Lower Aalenian. Proceedings of the Dorset Natural History and Archaeological Society. -
The shell is well preserved. It may be that the "injury" at the point where the phragmocone ends and the body chamber begins was caused by a predator.
-
Calcite steinkern of the phragmocone with partial shell remains.
-
The shell is preserved on this phragmocone.
-
A complete specimen with the shell preserved on one side. The transition from phragmocone to body chamber can be seen on the mold on the reverse side where the shell no longer exists.
-
Shell preservation over calcite steinkern. About 3/4 complete.
-
Calcite mold of the phragmocone with a bit of the body chamber.
-
The calcite mold of the phragmocone of another otherwise large ammonite. Named recently by Volker Dietze after the location where it was found. Literature: Dietze etal. 2014, Aalenian (Middle Jurassic) ammonites and stratigraphy of the Geisingen clay pit (SW Germany), Palaeodiversity 7: 61–127; Stuttgart
-
Steinkern of the phragmocone of an otherwise very large ammonite. Synonym: Ludwigia aff. laevigata (Buckman)
-
Calcite mold. This is only the phragmocone, so it would have been quite a large creature.
-
Most of the shell on this specimen is intact. Phragmocone.
-
Calcite mold of the phragmocone.
-
Calcite mold. This extremely variable species was newly erected in 2014 by Dietze etal. Literature: V.Dietze etal, Aalenian (Middle Jurassic) ammonites and stratigraphy of the Geisingen clay pit (SW Germany), Palaeodiversity 7: 61–127; Stuttgart 30 December 2014.
-
Calcite mold showing the suture lines of the phragmocone.
-
Calcite mold. Phragmocone and a small part of the body chamber.
-
Well preserved shell on one side; up to the end of the phragmocone on the other.
-
This specimen is pictured together with Ludwigia murchisonae. In the first photo it is to be seen on the right. Otherwise it is on the left hand side. About a half of a whorl is missing on the body chamber.
-
Not the best specimen due to the missing section of whorl, but still the best I have.
-
You can see how large it used to be by the remnant of the body chamber on the outer flank. This is the index fossil for the two sinon bank horizons in the murchsonae zone. Old German Chronostratigrahy: Dogger (Braunjura) beta
-
Almost complete with the shell partially preserved. Old German Chronostraigraphy: Dogger (Braunjura) beta 1
-
Index fossil of the bradfordensis zone. Phragmocone showing typical rib structure. The last photo shows another sample which illustrates how large these ammonites could get. The diameter is 20cm. and this is still just the phragmocone. Lithology: Geisingen-Oolith The Geisingen-Oolith is a horizon which was built and reworked over a long stretch of time at the coastal fringe of an arm of the Tethys ocean. Fauna from both the concavum and the bradfordensis zones are to be found in it. Old German Chronostratigraphy: Dogger (Braunjura) beta Literature: Dietze et al (2014): Aalenian (Middle Jurassic) ammonites and stratigraphy of the Geisingen clay pit (SW Germany). Palaeodiversity 7: 61-127
-
This is the index fossil of the concavum zone. Most of the shell is preserved, as is a small portion of the body chamber. These ammonites could reach a good size, as shown by the sample in the last 2 photos, which has a circumference of 21cm. Lithography: Geisingen-Oolith The Geisingen-Oolith is a horizon which was built and reworked over a long stretch of time at the coastal fringe of an arm of the Tethys ocean. Fauna from both the concavum and the bradfordensis zones are to be found in it. Old German Chronostratigraphy: Dogger (Braunjura) beta Literature: Dietze et al (2014): Aalenian (Middle Jurassic) ammonites and stratigraphy of the Geisingen clay pit (SW Germany). Palaeodiversity 7: 61-127
-
This is the index fossil of the murchisonae zone. This sample was disturbed either during burial or later tectonically at the point where the phragmocone meets the body chamber. The shell is completely preserved on one side showing clearly the typical ribbing. It is not quite complete, still missing about a half turn around the axes. Old German Chronostratigraphy: Dogger (Braunjura) beta Literature: Rieber,H. (1963): Ammoniten und Stratigraphie des Braunjura beta der Schwaebischen Alb, Palaeontographica Bd.122,Abt.A, Pp.1-89
-
This species has long been a subject of contention as to its lineage, but Dietze (2014), following the chronospecies/genus concept, has managed to prove to the satisfaction of most that it belongs to the subfamily of the Leioceratinae. Rieber (1963) had placed it in the subfamily Staufeniinae and had named it Staufenia opalinoides, a name which most collectors and paleontologists adopted, since his work was the most comprehensive one on the ammonite fauna of the area for many years. This almost complete specimen has most of its shell intact. The band of variation of ribbing and other sculptural factors is relatively broad, but this here is a typical sample. Biostratigraphy: Murchisonae Zone, Sinon Bank 1, haugi Subzone Old German Chronostratigraphy: Dogger (Braunjura) beta Literature: Rieber,H. (1963): Ammoniten und Stratigraphie des Braunjura beta der Schwaebischen Alb, Palaeontographica Bd.122,Abt.A, Pp.1-89 Dietze et al (2014): Aalenian (Middle Jurassic) ammonites and stratigraphy of the Geisingen clay pit (SW Germany), Palaeodiversity 7: 61–127 Horn,E. (1909): Die Harpoceraten der Murchisonae-Schichten des Donau-Rhein-Zuges, Mitteilungen der Großh. Badischen Geologischen Landesanstalt, VI. Bd.1.Heft
