Bajadasaurus
| Bajadasaurus | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Skeletal reconstruction of Bajadasaurus |
||||||||||||
| Temporal occurrence | ||||||||||||
| Lower Cretaceous ( Berriasium to Valanginium ) | ||||||||||||
| 145 to 133.9 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Bajadasaurus | ||||||||||||
| Gallina , Apesteguía , Canale & Haluza , 2019 | ||||||||||||
| Art | ||||||||||||
|
Bajadasaurus is a genus of sauropod dinosaur from the Dicraeosauridae family. Bajadasaurus pronuspinax is the only known species of the monotypic genus and livedin South America during the Lower Cretaceous .
This group of sauropods had pronounced forked spinous processes along the spine. This family also includes Amargasaurus , which appeared around 15 million years later, and of which an almost complete skeleton was also discovered in Argentina. The time difference between Bajadasaurus and Amargasaurus supports the assumption that the development of a spiky comb took place over a long period of time.
Naming and finds
The generic name Bajadasaurus was derived from the Spanish word “ bajada ” (“downhill”) in combination with the Latinized ancient Greek word σαῦρος “ sauros ” (“lizard”, “salamander”), based on the place where it was found . The additional species “ pronuspinax ” is made up of the Latin “ pronus ” (“forward inclined”) and the Latin “ spina ” (“thorn”, “sting”, “backbone”) and refers to the long, forward curved ones Spinous processes of the cervical spine.
The approximately 140 million year old remains were found in an outcrop of the Bajada Colorada Formation ( Neuquén Basin , Patagonia , Argentina ) of the Lower Cretaceous (late Berriasian to Valanginian ) about 57 km south of the city of Picún Leufú on the national road 237 . The evidence includes a nearly complete skull, including the entire lower jaw, as well as atlas and axis vertebrae and what is believed to be the fifth cervical vertebra . The skull fragments are the best preserved evidence to date for the entire family and allow reliable conclusions to be drawn about the size and shape of a dicraeosaurid skull.
features
Build and size
Like all sauropods, the Bajadasaurus had a barrel-shaped body that is reminiscent of that of the Diplodocidae , with a long neck and a very long tail, although in contrast to that group, a tendency to shorten the neck becomes clear. Bajadasaurus was a relatively small representative of the sauropods despite its size of 3 m, a length of approx. 12 m and a weight of approx. 4,000 kg . A typical feature of the dicraeosaurids are the greatly elongated, sometimes spiky, forked spinous processes of the cervical and dorsal vertebrae, which are very distinct in Amargasaurus and take on extreme form in Bajadasaurus .
The skull resembled that of Diplodocus , that is, it was elongated, with nostrils lying high on the head and teeth limited to the front end of the snout.
Systematics
Currently (as of 2019) are six other Dicraeosauriden-types from the Middle Jurassic of China ( Lingwulong Shenqui ), the Upper Jurassic of Africa ( Dicraeosaurus ), North America ( suuwassea emiliae ) and Zentralpatagonien ( brachytrachelopan mesai ) and the Lower Cretaceous of North Patagonia ( Pilmatueia faundezi and Amargasaurus cazaui ) known. In comparison with other sauropods such as B. the Diplodociden , which were characterized by very long necks, the neck of Brachytrachelopan with 150 cm in length only reached 75% of the body length. This animal thus had the shortest neck of all known sauropods and thus reinforced the proposal in the scientific discussion of the experts to fundamentally shorten the neck length within the group of dicraeosaurids .
Bajadasaurus belongs to the Dicraeosauridae, one of three groups within the Diplodocoidea and forms the sister taxon of a clade that consists of Pilmatueia (Lower Cretaceous) and an unnamed group that includes Amargasaurus , Brachytrachelopan and Dicraeosaurus . Bajadasaurus is the third representative from the Lower Cretaceous next to Amargasaurus and Pilamatueia .
Paleobiology
Bajadasaurus , like all representatives of the sauropods, was a pure herbivore . The arrangement of the eye sockets could be an indication that this dinosaur was capable of forward-looking, possibly stereoscopic vision even when eating .
Function of the elongated spinous processes
Bajadasaurus had relatively long thin spines arranged in pairs on the neck, which were inclined forward, and some were more than a meter long. It is believed that the spines were encased in a keratin sheath to provide better mechanical stability against potential breakage, similar to the horns of modern mammals .
Although previous research concluded that the horns in Amargasaurus were probably not much longer than the bone itself, the ratios of the bone core to the keratin sheath and the material resistance studies in recent reptiles and mammals suggest that the keratin sheaths in Amargasaurus and Bajadasaurus may have knocked over could have been up to 50% longer than the bone itself to improve bone protection.
The function of the long spinous processes is controversial. It is discussed that these spines could have served to repel and deter predators . A purely defensive function, based only on the bony resistance of the neural spine, seems incompatible with the persistence of long-spiked dicraeosaurids over a period of 15 million years. The large number of sharp spines would have posed a significant risk to carnivores if attacked. However, there are also functions for thermoregulation and communication with conspecifics, e.g. B. suspected the imposing behavior .
Individual evidence
- ↑ a b c d P. A. Gallina, S. Apesteguía, JI Canale & A. Haluza: A New Long-spined Dinosaur from Patagonia sheds light on Sauropod Defense System. In: Nature: Scientific Reports , 9, 2019, Article Number 1392, doi: 10.1038 / s41598-018-37943-3 .
- ↑ L. Salgado & JF Bonaparte: Un nuevo saurópodo Dicraeosauridae, Amargasaurus cazaui gen. Et sp. nov. de la Formacion La Amarga, Neocomiano de la Provincia del Neuquen, Argentina. In: Ameghiniana , Vol. 28, Numbers 3-4, 1991, pp. 333-346, ( reading sample ).
- ^ A b D. Schwarz, E. Frey & Ch. A. Meyer: Pneumaticity and soft tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods. In: Acta Palaeontologica Polonica , Volume 52, Number 1, 2007, pp. 167-188 ( digitized version ).
- ↑ JB Bailey: Neural spine elongation in dinosaurs: sailbacks or buffalo-backs ?. In: Journal of Paleontology , Volume 71, Number 6, 1997, pp. 1124-1146, ( abstract ).
