Agustinia

Agustinia /ɑːɡəˈstɪniə/ is a genus of sauropod dinosaurs from the Early Cretaceous Period of South America. It contains the single species Agustinia ligabuei, a single specimen of which was recovered from the Lohan Cura Formation of Neuquen Province in Argentina, thought to date from the late Aptian to Albian stages of the Early Cretaceous Period, between 116 and 100 million years ago.[1]

The name Agustinia honors the discoverer of the specimen, Agustin Martinelli. This dinosaur was originally named in a 1998 abstract written by famous Argentine paleontologist Jose Bonaparte.[2] The original generic name was "Augustia", which, as it turned out, was already preoccupied by a beetle (see also: Megapnosaurus, Protognathosaurus). Bonaparte changed the name to Agustinia in a full paper published in 1999.[1] There is one named species (A. ligabuei), which is named in honor of Dr. Giancarlo Ligabue, a philanthropist who provided financial support to the expedition which recovered the remains.

Agustinia
Temporal range: Early Cretaceous, 108 Ma
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Clade: Somphospondyli
Family: Agustiniidae
Bonaparte, 1999
Genus: Agustinia
Bonaparte, 1999
Type species
Agustinia ligabuei
Bonaparte, 1999

Description

Agustinia BW
A restoration of Agustinia showing spikey osteoderms, now believed to be fragments of rib and hip bones.

Only fragmentary remains are known. These include fragments of vertebrae from the back, hips, and tail regions of the spinal column. Parts of the lower hind limb were also recovered: a fibula, tibia, and five metatarsals. A femur (thigh bone) was found at the site, but was too fragmented to collect.[1][3]

Agustinia ligabuei was well known for its distinctive supposed armor plates (osteoderms), initially interpreted as a series of wide, vertical spikes and plates down the center of its back, somewhat like the unrelated Stegosaurus.[1] However, subsequent research has challenged the nature of these osteoderms.[4] Further study of the poorly preserved fossil material showed that these "plates" were in fact more likely to be fragments of ribs and hip bones.[5] This reassessment was reaffirmed subsequently by histology of the purported osteoderms, which do not match the internal structure of other titanosaurian osteoderms. The fragmentary hip bone was tentatively identified as part of the ilium.[6]

Aside from the supposed armor, very little has been described of the anatomy of Agustinia. A fibula (lower leg bone) has been recovered that is about 895 millimetres (35.2 in) long. When compared to the same bone in related dinosaurs, this indicates that Agustinia may have been about 15 metres (49 ft) long. However, the remains are incomplete and do not appear to have many distinctive characteristics which can be used to separate it from other sauropods. With the supposedly distinctive armor discredited, some authors have considered Agustinia a nomen dubium, for being based on remains not adequate to compare with related dinosaurs.[5]

Classification

Because of its supposedly unusual armor, Agustinia was originally assigned to its own family, Agustiniidae.[1] This family name has not come into wide acceptance. Agustinia is difficult to classify because of its fragmentary nature, and because it exhibits features of both diplodocoid and titanosaurian sauropods.[3] What few distinctive features do exist in the only known specimen suggests it is a member of the clade Somphospondyli, but it is not possible to determine its relationships with any more accuracy beyond that.[5]

References

  1. ^ a b c d e Bonaparte, J.F. 1999. An armoured sauropod from the Aptian of northern Patagonia, Argentina. In: Tomida, Y., Rich, T. H. & Vickers-Rich, P. (Eds.). Proceedings of the Second Gondwanan Dinosaur Symposium Tokyo: National Science Museum Monographs #15. Pp. 1–12.
  2. ^ Bonaparte, J.F. 1998. An armoured sauropod from the Aptian of northern Patagonia, Argentina. In: Tomida, Y., Rich, T. H. & Vickers-Rich, P. (Eds.). Second Symposium Gondwana Dinosaurs, 12–13 July 1998, Abstracts with Program. Tokyo: National Science Museum. Pg. 10.
  3. ^ a b Upchurch, P., Barrett, P.M., & Dodson, P. 2004. Sauropoda. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.) The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 259–322.
  4. ^ D'Emic, M. D.; Wilson, J. A. & Chaterjee, S. (2009). "The titanosaur (Dinosauria: Sauropoda) osteoderm record: review and first definitive specimen from India". Journal of Vertebrate Paleontology. 29: 165–177. doi:10.1671/039.029.0131.
  5. ^ a b c Mannion, Philip D.; Upchurch, Paul; Barnes, Rosie N.; Mateus, Octávio (2013). "Osteology of the Late Jurassic Portuguese sauropod dinosaur Lusotitan atalaiensis (Macronaria) and the evolutionary history of basal titanosauriforms". Zoological Journal of the Linnean Society. 168: 98–206. doi:10.1111/zoj.12029.
  6. ^ Bellardini, F.; Cerda, I.A. (2017). "Bone histology sheds light on the nature of the "dermal armor" of the enigmatic sauropod dinosaur Agustinia ligabuei Bonaparte, 1999". The Science of Nature. 104 (1). doi:10.1007/s00114-016-1423-7. PMID 27942797.
Apatosaurinae

Apatosaurinae is the name of a subfamily of diplodocid sauropods that existed between 157 and 150 million years ago in North America. The group includes two genera for certain, Apatosaurus and Brontosaurus, with at least five species. Atlantosaurus and Amphicoelias might also belong to this group.Below is a cladogram of apatosaurinae interrelationships based on Tschopp et al., 2015.

Argyrosauridae

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Brasilotitan

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Cetiosauridae

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Diplodocinae

Diplodocinae is an extinct subfamily of diplodocid sauropods that existed from the Late Jurassic to Early Cretaceous of North America, Europe and South America, about 161.2 to 136.4 million years ago. Genera within the subfamily include Tornieria, Supersaurus, Leinkupal, Galeamopus, Diplodocus, Kaatedocus and Barosaurus.Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015).

Eomamenchisaurus

Eomamenchisaurus (meaning "dawn Mamenchisaurus") is a genus of mamenchisaurid sauropod dinosaur from the Middle Jurassic of Yuanmou, Yunnan, China. The type species is E. yuanmouensis, described by Lü Junchang et al. in 2008.

Ferganasaurus

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Flagellicaudata

Flagellicaudata is a clade of Dinosauria. It belongs to Sauropoda and includes two families, the Dicraeosauridae and the Diplodocidae.

Gravisauria

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Huangshanlong

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Jiutaisaurus

Jiutaisaurus is a genus of sauropod dinosaur from the Quantou Formation of China. Jiutaisaurus was a sauropod which lived during the Cretaceous. The type species, Jiutaisaurus xidiensis, was described by Wu et al. in 2006, and is based on eighteen vertebrae.

Kaijutitan

Kaijutitan (meaning "Kaiju titan" after the type of Japanese movie monsters) is a genus of basal titanosaur dinosaur from the Sierra Barrosa Formation from Neuquén Province in Argentina. The type and only species is Kaijutitan maui.

Microcoelus

Microcoelus is a dubius genus of small Titanosaurian sauropod dinosaur native to Argentina. It is known from only a single dorsal vertebra. A left humerus was formerly referred to this species, but it is now considered to belong to Neuquensaurus. This species may be a synonym of the contemporary sauropod Neuquensaurus australis.It was described by British paleontologist Richard Lydekker in 1893.

Pilmatueia

Pilmatueia is a diplodocoid sauropod belonging to the family Dicraeosauridae that lived in Argentina during the Early Cretaceous.

Somphospondyli

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Tambatitanis

Tambatitanis is an extinct genus of titanosauriform dinosaur from the Early Cretaceous (probably early Albian) of Japan. It is known from a single type species, Tambatitanis amicitiae. It was probably around 14 meters long and its mass was estimated at some 4 tonnes. It was a basal titanosauriform and possibly belonged to the Euhelopodidae.

Tastavinsaurus

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Vulcanodontidae

The Early Jurassic sauropod dinosaurs Zizhongosaurus, Barapasaurus, Tazoudasaurus, and Vulcanodon may form a natural group of basal sauropods called the Vulcanodontidae. Basal vulcanodonts include some of the earliest known examples of sauropods. The family-level name Vulcanodontidae was erected by M.R. Cooper in 1984. In 1995 Hunt et al. published the opinion that the family is synonymous with the Barapasauridae. One of the key morphological features specific to the family is an unusually narrow sacrum.

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