Macronaria

Macronaria is a clade of the "suborder" (more likely an unranked clade than a suborder)[4] Sauropodomorpha. Macronarians are named after the large diameter of the nasal opening of their skull, known as the external naris, which exceeded the size of the orbit, the skull opening where the eye is located (hence macro- meaning large, and –naria meaning nose). Fossil evidence suggests that macronarian dinosaurs lived from the Late Jurassic (Kimmeridgian) through the Late Cretaceous (Maastrichtian). Macronarians have been found globally, including discoveries in Argentina, the United States, Portugal, China, and Tanzania. Like other sauropods, they are known to have inhabited primarily terrestrial areas, and little evidence exists to suggest that they spent much time in coastal environments. Macronarians are diagnosed through their distinct characters on their skulls, as well as appendicular and vertebral characters. Macronaria is composed of several subclades and families notably including Camarasauridae and Titanosauriformes, among several others. Titanosauriforms are particularly well known for being some of the largest terrestrial animals to ever exist.

Macronaria was described by Wilson and Sereno who proposed the new subdivisions among the clade Neosauropoda. Previously, this clade was thought to have Brachiosaurus and Camarasauridae forming one sister group, and Titanosauroidea and Diplodocoidea forming another. This proposed shift with Macronaria placed Diplodocoidea as an outgroup to the new clade Macronaria, under which all other neosauropods would fall.

Macronaria
Temporal range: Late JurassicLate Cretaceous, 174–66 Ma
Macronaria scrubbed enh
Several macronarian sauropods
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Clade: Neosauropoda
Clade: Macronaria
Wilson & Sereno, 1998
Clades and subclades

Anatomy

Several synapomorphies, characteristics passed down from ancestral species, exist for Macronaria. The following list includes some of the distinguishing characteristics that are diagnostic for Macronaria:[5][6][7]

  • The long axis of the distal ischial shaft lie on the same plane
  • Middle and posterior neural spines have distal ends that extend out transversely
  • Posterior neural spines extend at the tip forming a triangular process upwards.
  • The anterior chevrons of the tail have open proximal articulation
  • Robust, spatulate (spoon-like), and broad-crowned teeth
  • Crests formed by large protruding nasal
  • Elongate metacarpals
  • Forelimbs are relatively long in comparison to the hind limbs (most clearly demonstrated by Brachiosaurs)

Paleobiology

Posture, body size, and locomotion

The posture of macronarians is characterized by a novel ‘wide-gauged’ locomotor style, particularly in titanosaurs. While sauropods are known to be the giants of the dinosaurs, macronarians were not exclusively large-bodied. Macronarians show divergence in the evolution of body size with some members both increasing and decreasing in size from the primitive condition. For example, despite all being in the titanosaur clade, Argentinosaurus reached enormous sizes (~50 tons), while Saltasaurus and Magyarosaurus reached only 1.5-3 metric tons, which is fairly small for sauropods. While some macronarians represent some of the largest terrestrial vertebrates ever known, other macronarians experienced a steady size decrease over time.[7]

Biogeography

Sauropods, widely speaking, have been associated with both coastal and inland environments. It is believed that macronarians such as titanosaurs were strictly terrestrial and associated with inland environments such as lacustrine systems.[8][9] These findings are based on ‘wide-gauged’ trackways produced by titanosaurs which are strongly correlated with terrestrial sediments. It is also believed that macronarians have Gondwanan origins. Camarasaurus is among the most commonly found dinosaur from the Late Jurassic deposits of the Morrison Formation in the US. Unlike Camarasaurus, Titanosaurs were most commonly found in the Southern Hemisphere with the exception of Alamosaurus which was found in North America. There is strong geologic evidence that a land bridge between South and North America existed at the end of the Cretaceous allowing for dispersal of organisms between the two landmasses. Cretaceous sauropods are thought to have moved northward from South America, thus explaining the high density of South American sauropods, and the sole appearance of Alamosaurus in the Western Interior.[10]

Diet

It is well established that all sauropods, including macronarians, were obligate herbivores. Unlike their sister group, the diplodocids, which were thought to feed on low-lying plants, camarasaurids and other macronarians likely had strongly upward-oriented necks for browsing trees and taller plants.[11] Each tooth family in Camarasaurus is thought to have had a maximum of three replacement teeth and tooth formation took about 315 days. The replacement rate is thought to be one tooth every 62 days – this is about the same level or higher than non-sauropod herbivores, though it is lower than the replacement rates of the sister taxa, Diplodocus.[11] It is thought that this may be related to the fact that the low-browsing taxa ingested more grit and thus needed to replace teeth more, while Camarasaurus and other macronarians fed on mid to upper canopy plants where exogenous grit is almost non-existent. Given the large body size of these neosauropod herbivores, it is thought that this type of niche partitioning, characterized by different species taking advantage of different resources, was necessary for coexistence.

It was at one point believed that polished pebbles occasionally found with sauropod skeletons were gastroliths. Gastroliths are stones intentionally swallowed to aid with digestion (as is seen in a variety of modern birds). However, more recent taphonomic and sedimentological evidence suggests that sauropods did not use stones for digestion due to the general rarity of finding gastric mill-like stones with sauropod remains, and low relative mass of the stones to the size of sauropod bodies. When gastrolith-like rocks are found with sauropods, it may be that they were accidentally ingested, or intentionally ingested for mineral uptake.[12]

Phylogeny

Macronaria is nested within Neosauropoda and is sister to Diplodocoidea. These groups split around the mid- to late-Jurassic and end at the K-T boundary. In the less than 100 Myr that they lived, macronarians developed at least 216 synapomorphies and autapomorphies.[13] Despite the fact that macronarians are named after cranial openings, they are described by more appendicular synapomorphies. The species that survived late into the Cretaceous were characterized by stocky, wide-gauged posture, most notably the highly derived saltasaurines. Also under Macronaria are Camarasaurus, Brachiosaurus, and Titanosauria. Camarasauromorpha is the most basal group of Macronaria.

The cladogram below follows José Luis Barco Rodríguez (2010).[14]

Macronaria 

Camarasauridae

Laurasiformes 

Galvesaurus

Phuwiangosaurus

Aragosaurus

Tastavinsaurus Tastavinsaurus BW

Venenosaurus

Titanosauriformes 

Brachiosaurus Brachiosaurus DB flipped

Euhelopus EuhelopusDB2.jpg

Titanosauria Wintonotitan

The cladogram below follows José L. Carballido, Oliver W. M. Rauhut, Diego Pol and Leonardo Salgado (2011).[15]

Camarasauromorpha 

Camarasaurus

Europasaurus

Galvesaurus

Tehuelchesaurus Tehuelchesaurus benetezii

Janenschia

Tastavinsaurus Tastavinsaurus BW

Euhelopus EuhelopusDB2.jpg

Chubutisaurus

Wintonotitan

Titanosauriformes 

Brachiosauridae Brachiosaurus DB flipped

Phuwiangosaurus

Titanosauria Wintonotitan

Simplified cladogram of Macronaria after D'Emic (2012).[11]

Macronaria 

Camarasauridae

Tehuelchesaurus Tehuelchesaurus benetezii

Titanosauriformes 

Brachiosauridae Brachiosaurus DB flipped

Somphospondyli 

Euhelopodidae EuhelopusDB2.jpg

Chubutisaurus

Titanosauria Wintonotitan

For alternative cladograms see also Mateus et al. (2011),[16] Mannion et al. (2013).[17]

References

  1. ^ P. Upchurch, P. M. Barrett, and P. Dodson. 2004. Sauropoda. In D. B. Weishampel, H. Osmolska, and P. Dodson (eds.), The Dinosauria (2nd edition). University of California Press, Berkeley 259-322
  2. ^ Paul M. Barrett, Roger B.J. Benson and Paul Upchurch (2010). "Dinosaurs of Dorset: Part II, the sauropod dinosaurs (Saurischia, Sauropoda) with additional comments on the theropods". Proceedings of the Dorset Natural History and Archaeological Society. 131: 113–126.
  3. ^ P. D. Mannion. 2010. A revision of the sauropod dinosaur genus 'Bothriospondylus' with a redescription of the type material of the Middle Jurassic form 'B. madagascariensis. Palaeontology 53(2):277-296
  4. ^ Weishampel, D.B., Dodson, P., and Osmólska, H. (eds.). (2004). The Dinosauria. 2nd edition. University of California Press, Berkeley. 833 pp.
  5. ^ Wilson, Jeffrey A.; Sereno, Paul C. (1998-06-15). "Early Evolution and Higher-Level Phylogeny of Sauropod Dinosaurs". Journal of Vertebrate Paleontology. 18 (sup002): 1–79. doi:10.1080/02724634.1998.10011115. ISSN 0272-4634.
  6. ^ Upchurch, Paul (1995-09-29). "The Evolutionary History of Sauropod Dinosaurs". Philosophical Transactions of the Royal Society of London B: Biological Sciences. 349 (1330): 365–390. doi:10.1098/rstb.1995.0125. ISSN 0962-8436.
  7. ^ a b Carrano, Matthew T. (2005). The sauropods: evolution and paleobiology. University of California Press, Berkeley. pp. 229–249.
  8. ^ Butler, Richard J.; Barrett, Paul M. (2008-11-01). "Palaeoenvironmental controls on the distribution of Cretaceous herbivorous dinosaurs". Naturwissenschaften. 95 (11): 1027–1032. doi:10.1007/s00114-008-0417-5. ISSN 0028-1042. PMID 18581087.
  9. ^ Mannion, Philip D.; Upchurch, Paul (2010). "A quantitative analysis of environmental associations in sauropod dinosaurs" (PDF). Paleobiology. 36 (2): 253–282. doi:10.1666/08085.1.
  10. ^ Farlow, James Orville (1989). Paleobiology of the Dinosaurs. Geological Society of America. ISBN 9780813722382.
  11. ^ a b c D'emic, Michael D. (2012-11-01). "The early evolution of titanosauriform sauropod dinosaurs". Zoological Journal of the Linnean Society. 166 (3): 624–671. doi:10.1111/j.1096-3642.2012.00853.x. ISSN 0024-4082.
  12. ^ Wings, Oliver; Sander, P. Martin (2007-03-07). "No gastric mill in sauropod dinosaurs: new evidence from analysis of gastrolith mass and function in ostriches". Proceedings of the Royal Society of London B: Biological Sciences. 274 (1610): 635–640. doi:10.1098/rspb.2006.3763. ISSN 0962-8452. PMC 2197205. PMID 17254987.
  13. ^ Wilson, Jeffrey A. (2002-10-01). "Sauropod dinosaur phylogeny: critique and cladistic analysis". Zoological Journal of the Linnean Society. 136 (2): 215–275. doi:10.1046/j.1096-3642.2002.00029.x. ISSN 0024-4082.
  14. ^ José Luis Barco Rodríguez (2010). "Implicaciones filogenéticas y paleobiogeográficas del saurópodo Galvesaurus herreroi Barco, Canudo, Cuenca-Bescós y Ruiz-Omeñaca 2005".
  15. ^ José L. Carballido; Oliver W. M. Rauhut; Diego Pol; Leonardo Salgado (2011). "Osteology and phylogenetic relationships of Tehuelchesaurus benitezii (Dinosauria, Sauropoda) from the Upper Jurassic of Patagonia". Zoological Journal of the Linnean Society. 163 (2): 605–662. doi:10.1111/j.1096-3642.2011.00723.x.
  16. ^ Mateus, O., Jacobs, L. L., Schulp, A. S., Polcyn, M. J., Tavares, T. S., Buta Neto, A., ... & Antunes, M. T. (2011). Angolatitan adamastor, a new sauropod dinosaur and the first record from Angola. Anais da Academia Brasileira de Ciências, 83(1), 221-233.
  17. ^ Mannion, P. D., Upchurch, P., Barnes, R. N., & Mateus, O. (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(1), 98-206.
Abrosaurus

Abrosaurus (; 'delicate lizard' from the Greek αβρος meaning 'delicate' or 'dainty' and σαυρος meaning 'lizard') is a genus of macronarian sauropod dinosaur from the Middle Jurassic Period of what is now Asia, one of many dinosaurs found at the Dashanpu Quarry in the Sichuan Province of China. Like most sauropods, Abrosaurus was a quadrupedal herbivore but it was rather small for a sauropod, not much more than 30 feet (9 m) long. Its head was boxy and topped with a tall bony arch containing the nostrils.

The generic name meaning 'delicate lizard', refers to the nature of the skull, with large openings separated by thin bony struts. The only named species is now known as A. dongpoi, and is named after eleventh-century Chinese poet Su Shi, also known as Su Dongpo, who was born in Sichuan.

The naming of Abrosaurus has been a long and convuluted process. Abrosaurus was discovered in 1984 and was first described in the 1986 Ph.D. thesis of Chinese paleontologist Ouyang Hui, with the specific name "A. gigantorhinus". However, this does not meet ICZN standards of publication, so the species "Abrosaurus gigantorhinus" counts only as a nomen nudum, although it has been used incorrectly in at least one paper (Zhang & Chen, 1996). Ouyang formally described this species in 1989 under the specific epithet A. dongpoensis, but in biological nomenclature, the Latin suffix -ensis is correctly used only to honor localities and the name has since been revised to include the more correct -i suffix, which is used to honor male individuals (Peng & Shu, 1999). Abrosaurus dongpoi is now the accepted name for this taxon.

Abrosaurus was originally described as a camarasaurid sauropod, and while it may not turn out to be a member of that particular family, further research has indicated that it is a basal member of Macronaria, much like Camarasaurus itself. However, the remains of Abrosaurus have not been fully described, making its exact placement in the sauropod family tree difficult to determine (Upchurch et al., 2004).

The holotype, or original specimen, of Abrosaurus is a fossil skull which is nearly complete and very well preserved. A fragmentary skull and a skeleton have also been referred to this taxon but published description is lacking (Zhang & Chen, 1996). All of the material comes from the famous Dashanpu Quarry near Zigong in China, and is housed in the dinosaur museum there. Abrosaurus and at least 4 other species of sauropod are known from the Lower Shaximiao Formation (also called Xiashaximiao) at Dashanpu. These sediments are dated from the Bathonian to Callovian stages of the Middle Jurassic Period, or about 168 to 161 million years ago.

Aeolosaurini

Aeolosaurini is an extinct clade of titanosaurian dinosaurs known from the late Cretaceous period of Argentina and Brazil. Thomas Holtz (2011) assigned Adamantisaurus, Aeolosaurus, Gondwanatitan, Muyelensaurus, Panamericansaurus, Pitekunsaurus and Rinconsaurus to Aeolosauridae. Rodrigo M. Santucci and Antonio C. de Arruda-Campos (2011) in their cladistic analysis found Aeolosaurus, Gondwanatitan, Maxakalisaurus, Panamericansaurus and Rinconsaurus to be aeolosaurids.

Amargatitanis

Amargatitanis (meaning "Amarga giant") is a genus of dicraeosaurid sauropod dinosaur (a type of large, long-necked quadrupedal herbivorous dinosaur) from the Barremian-age (Lower Cretaceous) La Amarga Formation of Neuquén, Argentina.

Baotianmansaurus

Baotianmansaurus is a genus of titanosaur sauropod dinosaur. Its fossils have been found in Upper Cretaceous rocks in Henan, China, within the Gaogou Formation. The type species is B. henanensis, described in 2009. The holotype is 41H III-0200. Remains of the fossils were vertebrae, ribs and scapula fragments. It was probably a close relative of Opisthocoelicaudia and Dongyangosaurus in Saltasauridae.

Bellusaurus

Bellusaurus (meaning "Beautiful lizard", from Vulgar Latin bellus 'beautiful' (masculine form) and Ancient Greek sauros 'lizard') was a small short-necked sauropod dinosaur from the Middle Jurassic which measured about 4.8 metres (16 ft) long. Its fossils were found in Shishugou Formation rocks in the northeastern Junggar Basin in China.

Camarasauridae

Camarasauridae (meaning "chambered lizards") is a family of neosauropod dinosaurs within the clade Macronaria, the sister group to Titanosauriformes. Among sauropods, camarasaurids are small to medium-sized, with relatively short necks. They are visually identifiable by a short skull with large nares, and broad, spatulate teeth filling a thick jaw. Based on cervical vertebrae and cervical rib biomechanics, camarasaurids most likely moved their necks in a vertical, rather than horizontal, sweeping motion, in contrast to most diplodocids. Cladistically, they are defined to be all sauropods more closely related to Camarasaurus supremus than to Saltasaurus loricatus.

Dongyangosaurus

Dongyangosaurus is a genus of saltasaurid sauropod dinosaur from the early Late Cretaceous. The only species is Dongyangosaurus sinensis, from which only a single fragmentary skeleton is known, coming from the Zhejiang province of eastern China. It was described and named by Lü Junchang and colleagues Like other sauropods, Dongyangosaurus would have been a large quadrupedal herbivore.

Flagellicaudata

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

Gobititan

Gobititan is a genus of herbivorous sauropod dinosaur from the Barremian faunal stage of the Early Cretaceous, approximately 129-125 million years ago. The name of this genus, is derived from the Gobi desert region and the Titans of Greek mythology, which is a reference to its large body size. The specific name shenzhouensis, is derived from "Shenzhou", an ancient name for China.

Gravisauria

Gravisauria is a clade of sauropod dinosaurs consisting of some genera, Vulcanodontidae and Eusauropoda.

Haestasaurus

Haestasaurus is a genus of herbivorous sauropod dinosaur, belonging to the Macronaria, that during the Early Cretaceous lived in the area of present-day England. The only species is Haestasaurus becklesii.

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.

Lourinhasaurus

Lourinhasaurus (meaning "Lourinhã lizard") was an herbivorous sauropod dinosaur genus dating from Late Jurassic strata of Estremadura, Portugal.

Malarguesaurus

Malarguesaurus is a genus of titanosauriform sauropod dinosaur from the Late Cretaceous of Mendoza Province, Argentina. Its fossils, consisting of tail vertebrae, chevrons, ribs, and limb bones, were found in the late Turonian-early Coniacian-age (~89 million years old) Portezuelo Formation of the Neuquén Group. The type species, described by González Riga et al. in 2008, is M. florenciae.

Neosauropoda

Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentine paleontologist José Bonaparte and currently described as Saltasaurus loricatus, Diplodocus longus, and all animals directly descended from their most recent common ancestor. The group is composed of two subgroups: Diplodocoidea and Macronaria. Arising in the early Jurassic and persisting until the Cretaceous-Paleogene extinction event, Neosauropoda contains the majority of sauropod genera, including genera such as Apatosaurus, Brachiosaurus, and Diplodocus. It also includes giants such as Argentinosaurus, Patagotitan and Sauroposeidon, and its members remain the largest land animals ever to have lived.When Bonaparte first coined the term Neosauropoda in 1986, he described the clade as comprising “end-Jurassic” sauropods. While Neosauropoda does appear to have originated at the end of the Jurassic period, it also includes members through the end of the Cretaceous. Neosauropoda is currently delineated by specific shared, derived characteristics rather than the time period in which its members lived. The group was further refined by Upchurch, Sereno, and Wilson, who have identified thirteen synapomorphies shared among neosauropods. As Neosauropoda is a subgroup of Sauropoda, all members also display basic sauropod traits such as large size, long necks, and columnar legs.

Phuwiangosaurus

Phuwiangosaurus (meaning "Phu Wiang lizard") is a genus of titanosauriform dinosaur from the Early Cretaceous (Valanginian-Hauterivian) Sao Khua Formation of Thailand. The type species, P. sirindhornae, was described by Martin, Buffetaut, and Suteethorn in 1994; it was named to honour Princess Maha Chakri Sirindhorn of Thailand, who was interested in the geology and palaeontology of Thailand.

It was a mid-sized sauropod, measuring 15–20 m in length.

Phuwiangosaurus was originally assigned to Titanosauria, but more recent studies have placed it in a more basal position within the Titanosauriformes. Phylogenetic analyses presented by D'Emic (2012), Mannion et al. (2013), and Mocho et al. (2014) resolve Phuwiangosaurus within the Euhelopodidae, alongside genera such as Euhelopus and Tangvayosaurus. Other analyses have failed to find support for such a grouping, including some finding it to be paraphyletic at the base of Somphospondyli.

Ruyangosaurus

Ruyangosaurus (Ruyang County lizard) is a genus of titanosauriform sauropod dinosaur recovered from the Early Cretaceous Haoling Formation of China. The type species is R. giganteus, described in 2009 by Lü Junchang et al. Along with Huanghetitan and Daxiatitan, Ruyangosaurus is among the largest dinosaurs discovered in Cretaceous Asia.

Somphospondyli

Somphospondylans are an extinct clade of titanosauriform sauropods that lived throughout the world from the Late Jurassic through the Cretaceous in North America, South America, Europe, Asia, Africa and Australia. The group can be defined as "the most inclusive clade that includes Saltasaurus loricatus but excludes Brachiosaurus altithorax". Features found as diagnostic of this clade by Mannion et al. (2013) include the possession of at least 15 cervical vertebrae; a bevelled radius bone end; sacral vertebrae with camellate internal texture; convex posterior articular surfaces of middle to posterior caudal vertebrae; biconvex distal caudal vertebrae; humerus anterolateral corner "squared"; among multiple others.

Tangvayosaurus

Tangvayosaurus (meaning "Tang Vay lizard") is a genus of sauropod dinosaur from the Aptian-Albian age Lower Cretaceous Grès Supérior Formation of Savannakhet, Laos. It was a basal somphospondylan, about 15 m long, and is known from the remains of two or three individuals.

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