Amygdalodon

Amygdalodon
Temporal occurrence
	Middle Jurassic ( Bajocium )
	170.3 to 168.3 million years
Locations
	Chubut , Argentina ( Cerro Carnerero Formation );
Systematics
	Dinosaur (dinosauria)
	Lizard dinosaur (Saurischia)
	Sauropods (Sauropoda)
	Eusauropoda
	Amygdalodon
Scientific name
	Amygdalodon
	Cabrera , 1947
Art
	Amygdalodon patagonicus;

Amygdalodon is a genus of dinosaurs belonging to the group of sauropods . It wasfirst scientifically described by Angel Cabrera in 1947, based on a fragmentary skeleton from the Lower or Central Jurassic of Argentina . Today it is known that the skeleton consists of the remains of at least two different individuals - so it is unclear whether all remains actually belong to the same species.

As with all sauropods, it was a large four-legged herbivore with a long neck and tail. Amygdalodon is one of the oldest known sauropods, presumably it is an original representative of the Eusauropoda . The only species is Amygdalodon patagonicus .

Research history and naming

The geologist Alejandro Piatnitzky (1936) reported on "bones of a dinosaur that reached a body length of no less than 5-7 meters" ( bones of a saurian of no less than 5-7 m long ), which he found during a petroleum exploration found in the Argentine province of Chubut . Piatnitzky recovered some of the fossils, but left most of the fossils where they were found. At the beginning of 1947, the geologist Tómas Suero, who also worked for an oil company, visited the site and recovered most of the fossils. In the same year, Suero's findings were scientifically described by the paleontologist Angel Cabrera as a new species and genus - Amygdalodon patagonicus . This name means something like "Patagonian almond tooth" ( Greek amygdale - almond , Greek odon - "tooth") and indicates the "almond-shaped" shape of the teeth. Amygdalodon was the first dinosaur to be described from the Jurassic of South America.

In 1963 Rodolfo Casamiquela published a new description of the genus. In addition to the fossils recovered by Tómas Suero, Casamiquela also attributed the fossils previously recovered by Piatnitzky from the same site to this genus. In the following years , amygdalodon received little attention in the scientific literature. Various authors questioned the validity of this genus, as the characteristics described would not allow a clear distinction to related sauropod genera. Upchurch and colleagues (2004) note that amygdalodon could possibly be considered as the noun dubium (dubious name) in future studies .

Oliver Rauhut (2003) offered an extensive revision of the genre. This researcher pointed out that the amygdalodon fossils described so far belonged to more than one individual - thus it cannot be ruled out that the fossils belong to several different species. In order to maintain the validity of amygdalodon , Rauhut chose an anterior dorsal vertebra - the skeletal element that most clearly differs from other sauropods in terms of unique features - and identified it as the lectotype , which is used to redefine the genus. Except for two further vertebrae, Rauhut consistently excludes all other fossils from the genus. Thus amygdalodon is currently only known from three vertebrae.

Geology of the place of discovery, age and find

The site is located on the eastern foothills of the Sierra de Pampa de Agnía southeast of Cerro Camerón in Chubut. It belongs to the Cerro Carnerero Formation , a rock sequence that is composed primarily of tuffs and conglomerates . The age of this formation is controversial - although most authors give a date to the Bajocian ( Middle Jurassic ), others suspect that it was deposited during the Toarcian ( Lower Jurassic ). Amygdalodon is the only dinosaur so far described from the Cerro Carnerero Formation; other documented fossils include remains of plants. The amygdalodon fossils themselves come from a layer of sandy tuff and bluish-gray mudstone. Although no data on the location of the fossils relative to one another has been published, Oliver Rauhut suspects that the fossils would have been collected on the surface because a more extensive excavation would not have been possible for geologists involved in oil exploration.

The material originally presented to Amygdalodon is very fragmentary and includes various teeth, a few vertebrae (one cervical, three dorsal, one sacrum, two caudal and various vertebral fragments), fragmentary ribs, a fragmentary right pubic bone, a fragment of the scapula and the The lower end of a tibia. Oliver Rauhut (2003) shows that these fossils belonged to more than one individual - this is most obviously shown by the relative size differences of the bones. It is possible that the individuals represented by these fossils represent different ages of the same species; however, it cannot be ruled out that they belong to different species. Thus Rauhut only attributes the three vertebrae to the genus Amygdalodon , the remaining remains are separated from the genus as Eusauropod material that cannot be further assigned. All fossils are in the La Plata Museum in La Plata, Argentina .

Features and systematics

Amygdalodon reached a length of over ten meters. Oliver Rauhut (2003) described features on the vertebrae that differentiate the genus from all related genera: The lateral walls of the vertebral hole and the centropostzygapophyseal laminae (a thin bone sheet that connects the vertebral body with the posterior articular processes) break out laterally to the rear . In addition, the vertebral hole is not straight, but clearly curved.

Amygdalodon was originally classified as a member of the Cetiosauridae . This group of very original sauropods is now considered paraphyletic and thus invalid. Today amygdalodon is considered a very original representative of the Eusauropoda , a group that includes all sauropods with the exception of a few very original representatives. Belonging to the Eusauropoda is indicated by the vertebral arches of the vertebrae, which are as high or higher as the vertebral body.

Individual evidence

^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 176, online .
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Oliver WM Rauhut : Revision of Amygdalodon patagonicus Cabrera, 1947 (Dinosauria, Sauropoda). In: Messages from the Museum of Natural History in Berlin. Earth science series. Vol. 6, No. 1, 2003, ISSN 1435-1943 , pp. 173-181, doi : 10.1002 / mmng.20030060110 .
↑ Ben Creisler: Dinosauria Translation and Pronunciation Guide. Archived from the original on November 6, 2011 ; accessed on August 10, 2014 .
↑ ^a ^b ^c Angel Cabrera: Un sauropodo nuevo del Patagonia. In: Notas del Museo de La Plata. Paleontologia. Vol. 12, No. 95, 1947, ISSN 0325-2256 , pp. 1-17.
↑ Rodolfo M. Casamiquela: Consideraciones acerca de Amygdalodon Cabrera (Sauropoda, Cetiosauridae) del Jurasico Medio de la Patagonia. In: Ameghiniana . Vol. 3, No. 3, 1963, pp. 79-95.
^ John S. McIntosh: Sauropoda. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 1990, ISBN 0-520-06726-6 , pp. 345-401, here 378.
^ ^A ^b Paul Upchurch , Paul M. Barrett , Peter Dodson: Sauropoda. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 259-322, here p. 302.
^ ^A ^b Fernando E. Novas : The age of dinosaurs in South America. Indiana University Press, Bloomington IN 2009, ISBN 978-0-253-35289-7 , p. 95.

[paul_10-1] Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 176, online .

[rauhut_03-2] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Oliver WM Rauhut : Revision of Amygdalodon patagonicus Cabrera, 1947 (Dinosauria, Sauropoda). In: Messages from the Museum of Natural History in Berlin. Earth science series. Vol. 6, No. 1, 2003, ISSN 1435-1943 , pp. 173-181, doi : 10.1002 / mmng.20030060110 .

[creisler-3] Ben Creisler: Dinosauria Translation and Pronunciation Guide. Archived from the original on November 6, 2011 ; accessed on August 10, 2014 .

[cabrera_47-4] Angel Cabrera: Un sauropodo nuevo del Patagonia. In: Notas del Museo de La Plata. Paleontologia. Vol. 12, No. 95, 1947, ISSN 0325-2256 , pp. 1-17.

[casamiquela_63-5] Rodolfo M. Casamiquela: Consideraciones acerca de Amygdalodon Cabrera (Sauropoda, Cetiosauridae) del Jurasico Medio de la Patagonia. In: Ameghiniana . Vol. 3, No. 3, 1963, pp. 79-95.

[mcintosh_90-6] John S. McIntosh: Sauropoda. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 1990, ISBN 0-520-06726-6 , pp. 345-401, here 378.

[upchurch_04-7] A ^b Paul Upchurch , Paul M. Barrett , Peter Dodson: Sauropoda. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 259-322, here p. 302.

[novas_09_95-8] A ^b Fernando E. Novas : The age of dinosaurs in South America. Indiana University Press, Bloomington IN 2009, ISBN 978-0-253-35289-7 , p. 95.