Saltasauridae

Skeletal reconstruction of Opisthocoelicaudia

• North America
• South America
• Asia

The Saltasauridae are a group of sauropod dinosaurs within the Titanosauria. It includes the abgeleitetsten ( advanced ) Titanosaurier and existed in the late Cretaceous to the Cretaceous-Tertiary mass extinction about 66 million years ago.

The internal classification of Titanosauria is highly controversial. So the name Saltasauridae is not used by all researchers, and the number of associated species varies depending on the author. Often the Saltasauridae be divided into two subgroups: the Saltasaurinae which includes very diminutive forms from South America as Saltasaurus, Neuquensaurus, Rocasaurus and Bonatitan, as well as the Opisthocoelicaudiinae, which includes Opisthocoelicaudia and Alamosaurus.

This article deals with the taxon Saltasauridae from kladistischer view - for features and biology of these animals Main article: Titanosauria.

Definitions and Nomenclature

The taxon Saltasauridae was erected in 1980 by José Bonaparte and Jaime Eduardo Powell. The group is defined as a node-based taxon (node- based definition ) that the last common ancestor of Opisthocoelicaudia and Saltasaurus and all descendants of that ancestor with includes ( Wilson and Upchurch, 2003; Sereno, 1998). Almost all studies indicate unanimously that Saltasaurus was together with the closely related Neuquensaurus the abgeleitetste Titanosauria. As a next of kin of these are also referred to as Saltasaurinae grouping Opisthocoelicaudia and Alamosaurus apply. Whether Opisthocoelicaudia and Alamosaurus however, form a monophyletic group ( Opisthocoelicaudiinae ), as proposed for example by Sereno (1998) and Wilson ( 2002), is controversial.

The Saltasaurinae was put forward by Powell ( 1992). It is defined as all Saltasauriden that are more closely related to Saltasaurus loricatus than Opisthocoelicaudia skarzynskii ( Wilson and Upchurch, 2003). The Opisthocoelicaudiinae, erected by John McIntosh ( 1990), on the other hand is defined as all Saltasauriden that are more closely related to Opisthocoelicaudia skarzynskii than Saltasaurus loricatus ( Wilson and Upchurch, 2003).

Since the relationships within the Titanosauria are very controversial, varying the number of the Saltasauridae assigned genres in various studies. Wilson ( 2002) assigns the Saltasauridae the Opisthocoelicaudiinae consisting of Opisthocoelicaudia and Alamosaurus, as well as the Saltasaurine consisting of Saltasaurus and Neuquensaurus to. Often the Saltasaurinae also Rocasaurus and Bonatitan be attributed. According to an analysis by Hock zero and colleagues ( 2009), the genera Diamantinasaurus and Lirainosaurus could be representative of the Saltasauridae. A careful classification by Upchurch and colleagues ( 2004) assigns the group to only the genera Saltasaurus, Neuquensaurus and Opisthocoelicaudia while Alamosaurus and Rocasaurus be performed outside the group. These authors do not go on a subdivision into subgroups Saltasaurinae and Opisthocoelicaudiinae. In contrast to most other analyzes comes Curry Rogers (2005 ) found that Opisthocoelicaudia and Saltasaurus are related to each other only removed. Since the Saltasauridae according to its definition must include both of these genera, the last common ancestor of both species but according to the analysis assumes a much more basal position in the family tree, Rogers assigns Saltasauridae much of the Titanosauria - genres, including, for example Malawisaurus and Argentinosaurus.

Some studies use alternative names for the same group. For example, used Upchurch (1998 ) the name Titanosauridae to denote the grouping Alamosaurus, Opisthocoelicaudia and Saltasaurus. The name Titanosauridae is traditionally used to refer to a group of advanced Titanosauria. However, many researchers do not recognize that name, since it is based as a ranking based on taxon Titanosaurus as nominotypischem taxon which is frequently dismissed as invalid due to lack of diagnostic features. Even the name Eutitanosauria could be a synonym of Saltasauridae. Some researchers use alternative definitions and refer to the same group, which is referred to by other researchers as Saltasauridae than Saltasaurinae (eg Curry Rogers and Forster, 2001).

General characteristics and synapomorphies

Saltasauriden were small to medium sized sauropods. The limited to South America Saltasaurinae is characterized by a generally very small body size with lengths 12 to 15 meters and includes some of the smallest known sauropod with a. While Saltasaurus skin bony plates ( osteoderms ) were detected, these were absent probably at Opisthocoelicaudia and Alamosaurus. Saltasauriden are characterized by relatively short tails of only 35 caudal vertebrae, as well as slightly bent outward limbs. These features are already with less derived titanosaurs, but were most pronounced in the Saltasauridae as abgeleitetste Sauropodengruppe.

According to Upchurch and colleagues ( 2004) allows the Group to accurately define the following characteristics of other groups ( synapomorphies ): So is the upper arm bone (humerus ) a rounded crest on the upper ( proximal ) end. The posterior dorsal vertebrae show parapophyses that lie directly below the diapophyses. The anterior ( proximal ) caudal vertebrae show ventral to ( ventral) wide and deep depressions ( fossae ). The spinous processes of the anterior caudal vertebrae are wider than tall and are composed of different lamina complicated.