Diplodocoidea
Skeletal reconstruction of Apatosaurus in the Carnegie Museum in Pittsburgh.
North America, South America, Europe, Africa
The Diplodocoidea are a group of sauropod dinosaurs, which includes the families Diplodocidae, Dicraeosauridae and Rebbachisauridae. They appeared for the first time on the Upper Jurassic, where they reached the greatest biodiversity. While the Diplodocidae extinct in the Jurassic - Cretaceous boundary, survived the Dicraeosauridae to the Lower Cretaceous. The Rebbachisauridae, the last family of Diplodocoidea, on the other hand first appears in the Lower Cretaceous and was up in the early Late Cretaceous ( Coniacian ) represented.
Younger tooth finds from the Campanian and Maastrichtian of the Bauru Group in Brazil point out, however, that representatives of the Diplodocoidea could have survived until the late Cretaceous. The Diplodocoidea are recorded from North America, South America, Europe and Africa.
Features
The Diplodocoidea distinguished from other sauropods in particular in the structure of the skull and spine. The pine -shaped when viewed from above, an approximately rectangular teeth. The teeth were limited to the anterior region of the jaw. Most of these features were pronounced in Rebbachisauriden in which all teeth arranged in a frontal straight row of teeth, which was oriented perpendicularly to the longitudinal axis of the jaw. This feature of the Rebbachisauriden is unique among all dinosaurs. For the Diplodocoidea characteristic also were the narrow tooth crowns: Sun showed more primitive sauropods broad, overlapping crowns.
The Diplodocidae and Dicraeosauridae characterized by bifurcated spinous processes of the cervical and dorsal vertebrae. This bifurcated spinous processes are at the Dicraeosauriden Amargasaurus and Dicraeosaurus about four times as high as the corresponding vertebral body. This feature could have the training elastic ligaments allows that ran within the bifurcations along the spine. The Diplodocidae was also marked by a greatly elongated tail, which was composed of 80 vertebrae - almost twice as many as in some primitive sauropod. The rear about 30 caudal vertebrae were also two-sided convex and extended. This specialized tail ( " whip tail" ) could have had a direct defense function, but have also served as the generation of noise. Observations of extended, two-sided convex caudal vertebrae in Dicraeosauriden and Rebbachisauriden could show that these groups have had a whip-like tail. This hypothesis, however, can be confirmed or refuted only by further fossil finds.
Systematics and Definition
System
The Diplodocoidea together with the Macronaria the group Neosauropoda. The Macronaria contain Brachiosauridae, Camarasaurus and the Titanosauria. The Neosauropoda close all derived ( advanced ) with a sauropod.
The systematics within the Diplodocoidea is well known and relatively uncontroversial - problem is only the systematic position of Haplocanthosaurus. Within the Diplodocoidea three families are distinguished: The more original Rebbachisauridae and Dicraeosauridae and Diplodocidae. The Diplodocidae and Dicraeosauridae are often summarized as Flagellicaudata. Various original genres such Amphicoelias and Suuwassea are indeed classified within the Diplodocoidea, but made outside the three families.
It follows a recent cladogram example ( simplified from Harris and Dodson, 2004):
Suuwassea
Dicraeosaurus
Amargasaurus
Apatosaurus
Research History and Definition
Othniel Charles Marsh in 1884 named the family Diplodocidae with the single genus Diplodocus. The name Diplodocoidea by Paul Upchurch (1995 ) first used. Nevertheless, Marsh is awarded coining the name Diplodocoidea since, according to the International Rules for Zoological Nomenclature includes automatically with possible subfamilies ( - inae ) and superfamilies ( - oidea ) ( ICZN ) pattern of a family ( ending- idae ).
Upchurch (1995 ) ranked the Diplodocoidea first three families: the Diplodocidae that Dicraeosauridae and Nemegtosauridae. The Nemegtosauridae, consisting of the genera Nemegtosaurus and Quaesitosaurus, was known only by skull discoveries that have distinct similarities with the typical skull shape of Diplodocoidea. Today, however, these genera are considered to be representative of the Titanosauria; the similarities in skull shape are attributed to convergent evolution. Today the Diplodocoidea as originating line based taxon ( stem- based definition) be defined that includes all taxa that were more closely related to Diplodocus than Saltasaurus.
Genus list
Genera with safer assignment to Diplodocoidea
- Amargasaurus
- Amazonsaurus
- Amphicoelias
- Apatosaurus
- Barosaurus
- Brachytrachelopan
- Cathartes aura
- Dicraeosaurus
- Dinheirosaurus
- Diplodocus (including Seismosaurus )
- Dyslocosaurus
- Kaatedocus
- Limaysaurus
- Nigersaurus
- Rayososaurus
- Rebbachisaurus
- Supersaurus
- Suuwassea
- Tornieria
- Zapalasaurus
Genera with controversial assignment to Diplodocoidea
- Cetiosauriscus
- Eobrontosaurus
- Losillasaurus
- Haplocanthosaurus