Amygdalodon

• Chubut, Argentina ( Cerro- Carnerero Formation)

• Amygdalodon patagonicus

Amygdalodon is a genus of dinosaur from the group of sauropods. Created in 1947 described by Angel Cabrera for the first time scientifically, based on a fragmentary skeleton from the Lower or Middle Jurassic of Argentina. Today it is known that the skeleton from the remains of at least two different individuals there - so it is unclear whether all the remains actually belong to the same species.

Like all sauropods, there was a large four-legged herbivore with a long neck and tail. Amygdalodon is one of the oldest known sauropod, probably it is a representative of the original Eusauropoda. The only way is Amygdalodon patagonicus.

Research History and naming

The geologist Alejandro Piatnitzky (1936 ) reported on " bones of a dinosaur, which reached a length of not less than 5-7 meters " ( bones of a saurian of no less than 5-7 m long), which he during a petroleum exploration vorfand in the Argentine province of Chubut. Piatnitzky hid some of the fossils, but most fossils Reserve left at their locality. Beginning of 1947, visited the geologist Tomas Suero, who also worked for an oil company, the location, and hid most of the fossils. In the same year Sueros were discoveries of the paleontologist Angel Cabrera as a new genus and species scientifically described - Amygdalodon patagonicus. This name means as much as " almond Patagonian tooth" (Greek amygdale - Almond, gr odon - "tooth" ) and refers to the " almond " shape of the teeth. Amygdalodon was the first dinosaur that was described from the Jurassic of South America.

1963 published Rodolfo Casamiquela a redescription of the species. In addition to the salvaged by Tomas Suero fossils Casamiquela wrote to the previously recovered from Piatnitzky from the same reference fossils of this genus. In the aftermath Amygdalodon found in the scientific literature only little attention. Several authors questioned the validity of this genus in question, since the characteristics described would permit no clear demarcation for related sauropod genera. As remarkable Upchurch and colleagues ( 2004) that Amygdalodon in future studies could possibly be regarded as a noun dubium ( dubious name).

Oliver Rauhut (2003) offered an extensive revision of the genus. The researcher pointed out that the hitherto described Amygdalodon fossils belonged to more than one individual - thus can not be excluded that the fossils belong to several different species. In order to still maintain the integrity of Amygdalodon, Rauhut chose an anterior dorsal vertebra - the skeleton element that most clearly distinguished by unique features of other sauropods - and appointed him as Lektotypus basis of which the genus is redefined. Up to two more vertebrae Rauhut closes consistently from all other fossils of the genus. Thus Amygdalodon is currently known only by three vertebrae.

Geology of the discovery site, age and Fund

The site is located on the eastern foothills of the Sierra de Pampa de Agnia southeast of Cerro Camerón in Chubut. He belongs to the Cerro- Carnerero formation, a rock sequence, which is composed mainly of tuffs and conglomerates. The age of this formation is controversial - although most authors specify a date on the Bajocian ( Middle Jurassic ), suggest others that they came to the deposit already during the Toarciums ( Lower Jurassic ). Amygdalodon is so far the only dinosaur described from the Cerro- Carnerero lineup; other documented fossils include remains of plants with a. The Amygdalodon fossils themselves come from a layer of sandy tuff and bluish- gray mudstone. Although no data on the situation of the Fund fossils have been published relative to each other, Oliver Rauhut suggested that the fossils had been collected at the ground surface, since a more comprehensive excavation for geologists who are engaged in the oil exploration would not have been possible.

The originally Amygdalodon Asked material is very fragmentary and includes various teeth, a few vertebrae ( a neck, three back, a sacrum, two caudal vertebrae and various vertebral fragments), fragmentary ribs, a fragmentary right pubic bone, a fragment of the scapula and the lower end of the tibia with a. Oliver Rauhut (2003 ) shows that these fossils belong to more than one individual - most obviously to show this to the relative size differences of the bone. While it is possible that the individuals represented by these fossils represent different ages of the same kind; However, it can not be ruled out that they belonged to different species. Thus Rauhut writes to only the three vertebrae of the genus Amygdalodon, the rest remains to be spun off as not zuzuordnendes Eusauropoden material of the genus. All the fossils are located in the La Plata Museum in Argentina La Plata.

Characteristics and systematics

Amygdalodon reached a length of about ten meters. Oliver Rauhut (2003 ) described characteristics of the vertebrae, which delimit the genus from all related genera: To break the lateral walls of the intervertebral foramen and the Centropostzygapophyseal laminae ( a thin bone sheet, which the vertebral body to the posterior articular processes connects ) to the rear side of. In addition, the vertebral foramen is not straight but bent significantly.

Originally Amygdalodon was classified as a representative of the Cetiosauridae. This group of very original sauropods is now considered paraphyletic and hence invalid. Today Amygdalodon is considered a very original representatives of Eusauropoda, a group that includes all sauropods except for a few very original representative. Belonging to the Eusauropoda is indicated by the vertebral arches of the vertebrae, which are as high or higher than the vertebral body.