Opisthocoelicaudia

Opisthocoelicaudia
Skeletal reconstruction of Opisthocoelicaudia skarzynskii . However, the neck and head have not been handed down in fossil form.
Temporal occurrence
Upper Cretaceous (late Campanium to early Maastrichtian )
76.4 to 69.9 million years
Locations
Mongolia ( Nemegt formation )
Systematics
Dinosaur (dinosauria) Lizard dinosaur (Saurischia) Sauropodomorpha Sauropods (Sauropoda) Titanosaurs (Titanosauria) Opisthocoelicaudia
Scientific name
Opisthocoelicaudia
Borsuk-Białynicka , 1977
Art
Opisthocoelicaudia skarzynskii

Opisthocoelicaudia is a genus of sauropod dinosaur from the Titanosauria group . Fossil remains of this genus come from the Upper Cretaceous (late Campanium to early Maastrichtian ) of Mongolia ( Nemegt formation ).

So far, a well-preserved skeleton, partly found in an anatomical network, is known, which only lacks the neck and skull - thus Opisthocoelicaudia is one of the most completely fossilized Titanosauria. The genus was originally thought to be a representative of the Camarasauridae , but is now considered a very derived (advanced) representative of the Saltasauridae within the Titanosauria. Sometimes Opisthocoelicaudia is combined with the related Alamosaurus within a group called Opisthocoelicaudiinae . The only species is Opisthocoelicaudia skarzynskii .

features

Opisthocoelicaudia , like all sauropods, was a four-legged herbivore with a barrel-shaped body and a long neck and tail. It was a relatively small sauropod - Paul (1997) estimates the almost completely preserved specimen at a length of 11.3 meters and a weight of 8.4 tons. A recent study by Packard and colleagues (2009) meanwhile assumes a weight of 13 tons.

There is no fossil record of the skull and neck - however, a reconstruction of the nuchal ligament (ligamentum nuchae) suggests a neck of medium length that was carried horizontally or slightly inclined. The tail was relatively short with around 35 caudal vertebrae, like the related Alamosaurus . As with other derived titanosauria, additional mechanical connecting elements of the vertebrae ( hyposphene-hypantrum connections ) were missing , which led to a more flexible spine, while an additional sixth sacral vertebra strengthened the pelvic region. The spine was straight. While traditional reconstructions are based on a roughly horizontally aligned back, Daniela Schwarz and colleagues (2007) show that the back actually sloped backwards. The shoulder blade (scapula) with an angle of about 55 to 60 ° to the horizontal was aligned much steeper than previously assumed, which led to a higher shoulder region. The vertebrae of the anterior half of the tail were strongly opisthocoel, that is, they were convex on the anterior side and concave on the posterior side. This feature gives Opisthocoelicaudia its name and distinguishes the genus from all other Titanosauria, which were mostly characterized by strongly procoele (concave on the front and convex on the rear) anterior caudal vertebrae. Another unique ( autapomorphic ) feature was the forked spinous processes of the presacral (located in front of the sacrum) vertebrae.

The ischial (ischium) was relatively short as in many other titanosaur and made at opisthocoelicaudia only 2/3 of the length of the pubic bone (pubis) out. In contrast to other Titanosauria, the pubic and ischial bones were fused together. The columnar legs, like other Titanosauria, were robust and relatively short. The front legs of the specimen found were 1.87 meters high, measured from the highest point of the humerus, and made up about two thirds of the length of the hind legs, which were reconstructed at a height of 2.64 meters. As with other Titanosauria, the legs were slightly bent outwards, and were not exactly perpendicular under the body, as with other sauropods.

The forefoot consisted only of the five vertically standing and semicircular arranged metacarpal bones - as in all Titanosauria carpal bones (carpalia) were missing. Finger limbs, which were often present as extremely reduced residues in other Titanosauria, were completely absent in Opisthocoelicaudia . The ankle bone (astragalus) of the ankle joint was greatly reduced, as in other Titanosauria; the heel bone (calcaneus) appears to be completely absent in Opisthocoelicaudia . In contrast to the hand skeleton, the foot skeleton had the well-developed toes and claws typical of sauropods. The phalangeal formula (indicates the number of phalanges on each toe) is 2-2-2-1-0. To date, only two more complete foot skeletons of titanosaurs have been discovered, but they show a different phalangeal formula.

Osteoderms (skin bone plates) could be detected in 10 of the 40 known titanosaur genera . Since no osteoderms were found in Opisthocoelicaudia despite a completely preserved skeleton, researchers consider it likely that this genus actually did not have any osteoderms. Other titanosaurs without osteoderms known from relatively complete skeletal finds are Alamosaurus , Epachthosaurus and Phuwiangosaurus . This shows that osteoderms were acquired independently several times in the evolution of the Titanosauria.

Fossil record, history of discovery and naming

Ömnö-Gobi-Aimag, the Mongolian aimag (province) where all Opisthocoelicaudia fossils were discovered.

The type specimen (specimen number ZPAL MgD-I / 48) is a cranial (postcranial) skeleton with only the cervical vertebra missing. The site, Altan Ula IV , is located in Aimag Ömnö-Gobi in southern Mongolia and is part of the Nemegt Formation , the youngest of the three geological formations of the Nemegt Basin . Altan Ula IV is famous for a large number of different vertebrate fossils - among the finds are, in addition to the Opisthocoelicaudia skeleton, for example the troodontid Borogovia and the ankylosaur Tarchia . The skeleton belonged to an old individual. The majority of the vertebrae found has been preserved as a series in the anatomical network, which consists of 8 vertebrae, 6 sacral vertebrae and 34 caudal vertebrae. 3 other, poorly preserved vertebrae were found isolated from the series and probably belonged to the transition area between the cervical and back spine. The remaining parts of the skeleton were slightly displaced from the original anatomical structure.

In addition to this skeleton, a scapula with raven bone (coracoid) has also been described (specimen number ZPAL MgD-I / 25c) that belonged to a young individual, as can be seen from the not yet fused seam between these two bones. Researchers around Philip Currie also mention a fragmentary tail (specimen number MPD 100/406), which can also be attributed to Opisthocoelicaudia . This find comes from the Nemegt site, from which the Nemegtosaurus skull comes from.

The type specimen was discovered by geologist Ryszard Gradziński between June 10 and 23, 1965 during a Polish-Mongolian expedition. The transport of the Opisthocoelicaudia skeleton out of the very rough terrain posed major technical problems for the expedition team: The skeleton was embedded in hard sandstone and had to be transported in blocks with the help of sledges over a distance of 580 meters to the next place accessible by vehicles. The blocks, consisting of fossil bones and surrounding rock, weighed a total of about 12 tons. On July 9th, the packing of the skeleton began in 35 boxes, some weighing over a ton, which were then transported to Dalandsadgad . Currently the skeleton is in the collection of the Institute of Geology of the Mongolian Academy of Sciences in Ulaanbaatar .

The genus was first scientifically described in 1977 by Magdalena Borsuk-Białynicka . The name alludes to the special structure of the caudal vertebrae ( ancient Greek opisthe - "back", koilos - "hollow", and Latin cauda - "tail"). The second part of the species name, skarzynskii , honors Wojciech Skarżyński, the taxidermist of the skeleton.

Taphonomy

The type specimen shows bite marks, especially on the pelvis and on the right thigh bone, which shows that carnivores have eaten on the carcass of the animal. The head and neck of the otherwise fully preserved skeleton are missing, suggesting that the carnivores may have carried these body parts away. The skeleton was found lying on its back. It is significant that the left leg and rib bones were found on the right side of the body, while conversely the right leg and rib bones were found on the left side of the body. The carcass was probably only transported for a short time from a flood event and then buried by sediment before the soft tissue was completely decomposed. This is indicated by the mostly only weakly displaced bones from their original anatomical position.

Systematics

At first, Opisthocoelicaudia was considered a representative of the Camarasauridae , another group of sauropods that should include Camarasaurus and Euhelopus , but is no longer recognized today. This assignment was based primarily on the fork-shaped, low spinous processes of the vertebrae. The first describer Borsuk-Białynicka assigned Opisthocoelicaudia to the Euhelopodinae , which at that time was managed as a subfamily within the Camarasauridae family. Coombs and Molnar (1981) meanwhile classified the genus within the Camarasaurinae , another subfamily of the Camarasauridae. It was not until 1993 that Salgado and Coria were able to show that it was actually a titanosaur: Opisthocoelicaudia and other derived titanosauria showed numerous common features ( synapomorphies ), including a sixth sacral vertebra, opisthocoele dorsal vertebrae, missing phalanges, a shortened ischium, Missing hyposphene-hypantrum connections of the vertebral arches or a crescent-shaped sternum (sternum). Salgado and Coria (1993) assigned Opisthocoelicaudia to the Titanosauridae, a name that was frequently used in the past, but which is considered invalid by many researchers today. Instead, the name Lithostrotia is sometimes used, which describes the same group that is also occupied by the name Titanosauridae.

Almost all phylogenetic analyzes come to the conclusion that Opisthocoelicaudia is closely related to the North American genus Alamosaurus . Both genera are mostly regarded as close relatives of Saltasaurus and Neuquensaurus - the latter genera are also grouped together as Saltasaurinae . Some researchers see Alamosaurus and Opisthocoelicaudia as a monophyletic group called Opisthocoelicaudiinae and opposed to Saltasaurinae. Other researchers classify both genera as outgroups of the Saltasaurinae, considering the Opisthocoelicaudiinae as paraphyletic . The grouping Saltasaurinae + Opisthocoelicaudia + Alamosaurus is also known as Saltasauridae . In contrast to most other previous analyzes, Curry Rogers (2005) comes to the conclusion that Alamosaurus and Opisthocoelicaudia were only distantly related to the Saltasaurinae. Upchurch and colleagues (2004) meanwhile do not see Alamosaurus and Opisthocoelicaudia as close relatives - while they classify Alamosaurus as sister taxons of Pellegrinisaurus outside the Saltasauridae , they classify Opisthocoelicaudia within the Saltasauridae.

Two cladogram examples follow - with monophyletic Opisthocoelicaudiinae (Wilson 2002, left) and with paraphyletic Opisthocoelicaudiinae (Calvo and Gonzáles-Riga 2003, right):

Saltasauridae    Opisthocoelicaudiinae   Opisthocoelicaudia     Alamosaurus  Saltasaurinae   Neuquensaurus     Saltasaurus

Opisthocoelicaudia     Alamosaurus  Saltasaurinae   Neuquensaurus     Saltasaurus

Synonymy with Nemegtosaurus

Another sauropod of the Nemegt formation is Nemegtosaurus , which is only known from a skull find. From opisthocoelicaudia only the rest of the skeleton, meanwhile, is known, which excludes direct anatomical comparisons. Various researchers suspect that both genera are one and the same species ( synonymy ). According to the International Rules for Zoological Nomenclature (ICZN), the name assigned first - in this case Nemegtosaurus - would be valid in such a case ; the name Opisthocoelicaudia would then be invalid.

Borsuk-Białynicka considers a synonymy in their first description to be unlikely, since they saw both genera as representatives of different groups. So she classified Opisthocoelicaudia as Camarasauriden, while she attributed Nemegtosaurus to the Dicraeosauridae in accordance with the research opinion of the time. She also argued that multiple sauropod species in the same place at the same time were not uncommon, as demonstrated by other fossil sites such as the Morrison Formation with more than five sauropod species living at the same time.

In the meantime, both genera are classified within the Titanosauria, which is why Wilson (2005), for example, notes that a synonymy cannot be ruled out. Currie and colleagues (2003) consider a synonymy to be very likely and report on a fragmentary tail that can be attributed to Opisthocoelicaudia and that comes from the same site as the Nemegtosaurus skull. However, further findings are needed to finally clarify the question.

Paleoecology

The opisthocoelicaudia -Fossilien originate from the Nemegt formation , a geologic formation , which in the Gobi in southern Mongolia open is. Although its age has never been dated radiometrically , the fossil fauna indicates that it was deposited during the Maastrichtian period (between 72 and 66 million years ago) . Large river beds and remains of soil ( paleo soils ) indicate a relatively humid climate, which contrasts with the semi-arid climate under which the underlying layers, the Barun-Goyot Formation and the Djadochta Formation , were deposited. However, caliches - concretions made from precipitated calcium carbonate - indicate periodic droughts.

The Nemegt Formation is a significant fossil deposit and contains one of the richest and most diverse dinosaur faunas known. Opisthocoelicaudia shared the habitat with turtles, crocodiles like Shamosuchus and birds like Gurilynia , Judinornis and Teviornis . Mammalian fossils are very rarely found. Dinosaurs from the ornithischia group were represented by the ankylosaur Tarchia , the pachycephalosaurs Homalocephale and Prenocephale and the hadrosaurids Saurolophus and Barsboldia . The numerous small theropod the formation close troodontids as borogovia , Tochisaurus and Zanabazar , Oviraptorosaurier as elmisaurus , nemegtomaia and rinchenia , Ornithomimosaurier as anserimimus , Gallimimus and Deinocheirus , Therizinosauroideen as Therizinosaurus and the Dromaeosauriden adasaurus and Tyrannosauroideen bagaraatan and Alioramus with one. The top predator of the fauna - and possibly the predator of Opisthocoelicaudia - was the tyrannosaurid Tarbosaurus . In addition to Opisthocoelicaudia , a second sauropod species is represented with Nemegtosaurus .

Paleobiology

Support function of the tail

Borsuk-Białynicka suspected that the tail, as a kind of third leg, could have allowed it to stand up on the hind legs, for example when searching for food. She argued that the tail was more flexible than other sauropods thanks to the opisthocoel caudal vertebrae. Features on the pelvic bones, such as a deepened hip joint socket (acetabulum) with a thickened rim, would also support this theory. Some more recent studies interpret other features, such as the tail, which is severely shortened with only about 35 caudal vertebrae, as possible indications of a supporting function of the tail in Opisthocoelicaudia and other Saltasaurids.

Footprints

Fossil footprints are very rarely found in the Nemegt Formation. Various footprints, mainly from hadrosaurids , were uncovered at the Nemegt site - including at least two footsteps that were made by the hind foot of a sauropod. Currie and colleagues (2003) assign these traces to the genus Opisthocoelicaudia , which is justified by the very similar morphology of the tread seals and the foot skeleton of the Opisthocoelicaudia type specimen. It is possible that the stamps actually come from a different, related genus. In the opinion of these researchers, however, this is unlikely, since they regard Nemegtosaurus and Opisthocoelicaudia as synonyms and consequently only postulate a single sauropod species in the Nemegt fauna.

Both step seals are three-dimensional casts of the actual, no longer preserved impressions. The best-preserved sauropod step-seal measures 63 centimeters in diameter and probably belonged to an animal slightly larger than the Opisthocoelicaudia type specimen. Although the lower (ventral) surface is hardly preserved, the vertical, lateral surfaces are very well preserved: They even show a skin impression showing the non-overlapping scales with an average diameter of 14 millimeters. The trace generator wore two to three claws on each hind foot, with the toes standing almost vertically ( digitigrade ). The foot of the tracker was probably a little longer than it was wide.

further reading

• Magdalena Borsuk-Białynicka: A new camarasaurid sauropod Opisthocoelicaudia skarzynskii gen. N., Sp. n. from the Upper Cretaceous of Mongolia. In: Palaeontologia Polonica. No. 37, 1977, ISSN  0078-8562 , pp. 5-64, digital version (PDF; 5.62 MB) .
• Philip J. Currie , Demchig Badamgarav, Eva B. Koppelhus: The First Late Cretaceous Footprints from the Nemegt Locality in the Gobi of Mongolia. In: Ichnos. Vol. 10, No. 1, 2003, ISSN  1042-0940 , pp. 1-12, doi : 10.1080 / 10420940390235071 .
• Zofia Kielan-Jaworowska, Naydin Dovchin: Narrative of the Polish-Mongolian Expeditions 1963-1965. In: Palaeontologia Polonica. No. 19, 1969, pp. 7-30, digitized version (PDF; 2.53 MB) .
• Leonardo Salgado , Rodolfo A. Coria : Consideraciones sobre las relaciones filogeneticas de Opisthocoelicaudia skarynskii (Sauropoda) del Cretácico superior de Mongolia. In: X Jornadas Argentinas de Paleontologia de Vertebrados. 1993, (In English: Considerations on the phylogenetic relationships of Opisthocoelicaudia skarzynskii (Sauropoda) from the Upper Cretaceous of Mongolia. Abstract , translated by Jeffrey Wilson in Doc format).
• Daniela Schwarz, Eberhard Frey , Christian A. Meyer: Novel Reconstruction of the Orientation of the Pectoral Girdle in Sauropods. In: The Anatomical Record . Vol. 290, No. 1, 2007, ISSN  1932-8486 , pp. 32-47, doi : 10.1002 / ar.20405 .

Web links

Commons : Opisthocoelicaudia  - collection of images, videos and audio files

Individual evidence

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. 212, online .
2. ^ Gregory S. Paul: Reproductive behavior and rates. In: Philip Currie, Kevin Padian (Eds.): Encyclopedia of Dinosaurs. Academic Press, San Diego CA et al. 1997, ISBN 0-12-226810-5 , pp. 630-637.
3. ^ Gary C. Packard, Thomas J. Boardman, Geoffrey F. Birchard: Allometric equations for predicting body mass of dinosaurs. In: Journal of Zoology. Vol. 279, No. 1, 2009, ISSN  0952-8369 , pp. 102-110, doi : 10.1111 / j.1469-7998.2009.00594.x .
4. ↑ ^{a b} Kristina Curry Rogers: Titanosauria: A Phylogenetic Overview. In: Kristina Curry A. Rogers, Jeffrey A. Wilson (Eds.): The Sauropods. Evolution and Paleobiology. University of California Press, Berkeley CA et al. 2005, ISBN 0-520-24623-3 , pp. 50-103, doi : 10.1525 / california / 9780520246232.003.0003 .
5. ↑ Sebastián Apesteguía: Evolution of the Hyposphene-Hypantrum Complex within Sauropoda. In: Virginia Tidwell, Kenneth Carpenter (Eds.): Thunder-lizards. The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34542-1 , pp. 248-267.
6. ^ Daniela Schwarz, Eberhard Frey, Christian A. Meyer: Novel Reconstruction of the Orientation of the Pectoral Girdle in Sauropods. In: The Anatomical Record. Vol. 290, No. 1, 2007, ISSN  1932-8486 , pp. 32-47, doi : 10.1002 / ar.20405 .
7. ^ ^{A b} Leonardo Salgado , Rodolfo A. Coria : Consideraciones sobre las relaciones filogeneticas de Opisthocoelicaudia skarynskii (Sauropoda) del Cretácico superior de Mongolia. In: X Jornadas Argentinas de Paleontologia de Vertebrados. 1993, (In English: Considerations on the phylogenetic relationships of Opisthocoelicaudia skarzynskii (Sauropoda) from the Upper Cretaceous of Mongolia. Abstract , translated by Jeffrey Wilson in Doc format).
8. ↑ ^{a b} Jeffrey A. Wilson: Sauropod dinosaur phylogeny: critique and cladistic analysis. In: Zoological Journal of the Linnean Society. Vol. 136, No. 2, 2002, ISSN  0024-4082 , pp. 215-275, doi : 10.1046 / j.1096-3642.2002.00029.x .
9. ↑ ^{a b c d e f g h i j k} Magdalena Borsuk-Białynicka: A new camarasaurid sauropod Opisthocoelicaudia skarzynskii gen. N., Sp. n. from the Upper Cretaceous of Mongolia. In: Palaeontologia Polonica. No. 37, 1977, ISSN  0078-8562 , pp. 5-64, digital version (PDF; 5.62 MB) .
10. ^ ^{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. 259-324.
11. ^ Matthew T. Carrano: The Evolution of Sauropod Locomotion: morphological diversity of a secondarily quadrupedal radiation. In: Kristina Curry A. Rogers, Jeffrey A. Wilson: The Sauropods. Evolution and Paleobiology. University of California Press, Berkeley, Cal. et al. 2005, ISBN 0-520-24623-3 , pp. 229-251.
12. ↑ Jeffrey A. Wilson, Matthew T. Carrano: Titanosaurs and the Origin of "Wide-Gauge" Trackways: A Biomechanical and Systematic Perspective on Sauropod Locomotion. In: Paleobiology. Vol. 25, No. 2, 1999, ISSN  0094-8373 , pp. 252-267.
13. ↑ Sebastián Apesteguía: Evolution of the Titanosaur Metacarpus. In: Virginia Tidwell, Kenneth Carpenter (Eds.): Thunder-lizards. The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34542-1 , pp. 321-346.
14. ↑ Bernardo J. González Riga, Jorge Orlando Calvo , Juan Porfiri: An articulated titanosaur from Patagonia (Argentina): New evidence of neosauropod pedal evolution. In: Palaeoworld. Vol. 17, No. 1, 2008, ISSN  1871-174X , pp. 33-40, doi : 10.1016 / j.palwor.2007.08.003 .
15. ↑ Michael D. D'Emic, Jeffrey A. Wilson, Sankar Chatterjee : The titanosaur (Dinosauria: Sauropoda) osteoderm record: review and first definitive specimen from India. In: Journal of Vertebrate Paleontology. Vol. 29, No. 1, 2009, pp. 165-177, doi : 10.1671 / 039.029.0131 .
16. ↑ Halszka Osmólska: Borogovia gracilicrus gen. Et sp. n., a new troodontid dinosaur from the Late Cretaceous of Mongolia. In: Acta Palaeontologica Polonica. Vol. 32, No. 1/2, ISSN  0567-7920 , 1987, pp. 133-150, online .
17. ^ Teresa Maryańska: Remains of armored dinosaurs from the uppermost Cretaceous in Nemegt Basin, Gobi Desert. In: Palaeontologia Polonica. No. 21, 1970, pp. 23-32, digitized version (PDF; 1.24 MB) .
18. ↑ ^{a b c d e f} Philip J. Currie , Demchig Badamgarav, Eva B. Koppelhus: The First Late Cretaceous Footprints from the Nemegt Locality in the Gobi of Mongolia. In: Ichnos. Vol. 10, No. 1, 2003, ISSN  1042-0940 , pp. 1-12, doi : 10.1080 / 10420940390235071 .
19. ^ ^{A b} Zofia Kielan-Jaworowska, Naydin Dovchin: Narrative of the Polish-Mongolian Expeditions 1963–1965. In: Palaeontologia Polonica. No. 19, 1969, pp. 7-30, digitized version (PDF; 2.53 MB) .
20. ^ Teresa Maryańska: Sauropods from Mongolia and the former Soviet Union. In: Michael J. Benton , Mikhail A. Shishkin, David M. Unwin, Evgenii N. Kurochkin (eds.): The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press, Cambridge et al. 2000, ISBN 0-521-55476-4 , pp. 456-461.
21. ^ Ryszard Gradziński: Sedimentation of Dinosaur-bearing Upper Cretaceous Deposits of the Nemegt Basin, Gobi Desert. In: Palaeontologia Polonica. No. 21, 1969, pp. 147-229, digitized version (PDF; 5.97 MB) .
22. ↑ Paul Sereno: Camarasauridae. (No longer available online.) In: Taxon Search. Archived from the original on August 13, 2014 ; Retrieved August 29, 2014 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  
23. ^ Walter P. Coombs, Ralph E. Molnar: Sauropoda (Reptilia, Saurischia) from the Cretaceous of Queensland. In: Memoirs of the Queensland Museum. Vol. 20, No. 2, 1981, ISSN  0079-8835 , pp. 351-373.
24. ↑ Jeffrey A. Wilson: An Overview of Titanosaur Evolution and Phylogeny. In: Fidel Torcida Fernández-Baldor, Pedro Huerta Hurtado (eds.): Actas de las III Jornadas Internacionales sobre Paleontología de Dinosaurios y Su Entorno. = Proceedings of the 3rd International Symposium about Paleontology of Dinosaurs and their Environment Paleontología de dinosaurios y su entorno. Salas de los Infantes (Burgos, España), 16 al 18 de septiembre de 2004. Colectivo arqueológico-paleontológico de Salas, Salas de los Infantes (Burgos, España) 2006, ISBN 84-8181-227-7 , pp. 169-190 .
25. ↑ Jorge O. Calvo, Bernardo J. González Riga: Rinconsaurus caudamirus gen. Et sp nov., A new titanosaurid (Dinosauria, Sauropoda) from the Late Cretaceous of Patagonia, Argentina. In: Revista Geológica de Chile. Vol. 30, No. 2, 2003, ISSN  0378-6617 , pp. 333-353, doi : 10.4067 / S0716-02082003000200011 .
26. ↑ Jeffrey A. Wilson: Redescription of the Mongolian Sauropod Nemegtosaurus mongoliensis Nowinski (Dinosauria: Saurischia) and comments on Late Cretaceous Sauropod diversity. In: Journal of Systematic Palaeontology. Vol. 3, No. 3, 2005, ISSN  1477-2019 , pp. 283-318, doi : 10.1017 / S1477201905001628 .
27. ↑ ^{a b} Tomasz Jerzykiewicz, Dale A. Russell : Late Mesozoic stratigraphy and vertebrates of the Gobi Basin. In: Cretaceous Research. Vol. 12, No. 4, 1991, ISSN  0195-6671 , pp. 345-377, doi : 10.1016 / 0195-6671 (91) 90015-5 .
28. Jump up ↑ Jørn H. Hurum, Karol Sabath: Giant theropod dinosaurs from Asia and North America: Skulls of Tarbosaurus bataar and Tyrannosaurus rex compared. In: Acta Palaeontologica Polonica. Vol. 78, No. 2, 2003, pp. 161-190, online .
29. ↑ David B. Weishampel, Paul M. Barrett, Rodolfo Coria, Jean Le Loeuff, Xing Xu , Xijin Zhao , Ashok Sahni, Elizabeth Gomani, Christopher R. Noto: Dinosaur distribution. 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. 517-683, here pp. 517-606.
30. ↑ Jeffrey A. Wilson: Overview of Sauropod Phylogeny and Evolution. Kristina Curry Rogers, Jeffrey A. Wilson (Eds.): The Sauropods. Evolution and Paleobiology. University of California Press, Berkeley CA et al. a 2005, ISBN 0-520-24623-3 , pp. 15-49, digitized version (PDF; 384.37 KB) .

This article was added to the list of excellent articles on March 5, 2011 in this version .