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Temporal range: Early-Late Cretaceous, Albian–Cenomanian
Sonorasaurus thompsoni.jpg
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropoda
Family: Brachiosauridae
Genus: Sonorasaurus
Ratkevich, 1998
S. thompsoni
Binomial name
Sonorasaurus thompsoni
Ratkevich, 1998

Sonorasaurus is a genus of brachiosaurid dinosaur from the Early to Late Cretaceous (Albian to Cenomanian stages, around 112 to 93  million years ago). It was a herbivorous sauropod whose fossils have been found in southern Arizona in the United States. Its name, which means "Sonora lizard", comes from the Sonoran Desert where its fossils were first found. The type species is S. thompsoni, described by Ratkevich in 1998.

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

Brachiosauridae family of reptiles (fossil)

The Brachiosauridae are a family or clade of herbivorous, quadrupedal sauropod dinosaurs. Brachiosaurids had long necks that enabled them to access the leaves of tall trees that other sauropods would have been unable to reach. In addition, they possessed thick spoon-shaped teeth which helped them to consume tough plants more efficiently than other sauropods. They have also been characterized by a few unique traits or synapomorphies; dorsal vertebrae with 'rod-like' transverse processes and an ischium with an abbreviated pubic peduncle.

Dinosaur Superorder of reptiles (fossil)

Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago; their dominance continued through the Jurassic and Cretaceous periods. Reverse genetic engineering and the fossil record both demonstrate that birds are modern feathered dinosaurs, having evolved from earlier theropods during the late Jurassic Period. As such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event 66 million years ago. Dinosaurs can therefore be divided into avian dinosaurs, or birds; and non-avian dinosaurs, which are all dinosaurs other than birds. This article deals primarily with non-avian dinosaurs.



Fossilized remains were discovered by geology student Richard Thompson, in November 1994, in the Chihuahua Desert region of the Sonoran Desert in southern Arizona. Thompson had investigated a previously almost unexplored region, where fossils proved to be plentiful and directly accessible on the surface. A relatively complete sauropod skeleton was weathering out on a rock wall. He informed paleontologist Ronald Paul Ratkevich of the Arizona-Sonora Desert Museum, Tucson of the find. Ratkevich assembled a team of volunteers and began securing the bones in the spring of 1995; excavations would only end in 1999. He assumed the fossils represented a sauropod but was no expert on that taxon. The curator of geology of the museum, David W. Thayer, thought it might be a therizinosaur, mistaking a tail chevron bone for the long hand claw typical of that group. In 1995, Ratkevich and Tayer first reported the find, already using the name "Sonorasaurus" but informally, so that it remained a nomen nudum . [1]

Sonoran Desert North American desert

The Sonoran Desert is a North American desert which covers large parts of the Southwestern United States in Arizona and California and of Northwestern Mexico in Sonora, Baja California, and Baja California Sur. It is the hottest desert in Mexico. It has an area of 260,000 square kilometers (100,000 sq mi). The western portion of the United States–Mexico border passes through the Sonoran Desert.

The Arizona-Sonora Desert Museum is a 98-acre zoo, aquarium, botanical garden, natural history museum, publisher, and art gallery founded in 1952. Located just west of Tucson, Arizona, it features two miles (3.2 km) of walking paths traversing 21 acres of desert landscape. It is one of the most visited attractions in Southern Arizona.

In taxonomy, a nomen nudum is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be a scientific name, but fails to be one because it has not been published with an adequate description. This makes it a "bare" or "naked" name, one which cannot be accepted as it stands. A largely equivalent but much less frequently used term is nomen tantum.

Both men now asked dinosaur expert Edwin Harris Colbert to identify the animal. Colbert, having seen only pictures, suggested it might be a member of the Hadrosauridae. Ratkevich and Thayer then visited the displays in the American Museum of Natural History, concluding their find was rather dissimilar to the hadrosaurid skeletons shown there, so that it must represent a species new to science. Ratkevich considered naming it "Chihuahuasaurus" but ultimately shied away from the comical contrast between the gigantic sauropod and the minute dog breed. In 1996, a subsequent article tried to fit the bones found, in a diagram of the hadrosaurid Kritosaurus . This attempt largely failed, with an ilium being mistaken for a shoulder blade. Again, the name "Sonorasaurus" was used but still invalidly. [2]

Hadrosauridae family of reptiles (fossil)

Hadrosaurids, or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The family, which includes ornithopods such as Edmontosaurus and Parasaurolophus, was a common group of herbivores during the Late Cretaceous Period in what is now Asia, Europe, Antarctica, South America, and North America. Hadrosaurids are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had a similar body layout.

American Museum of Natural History Natural history museum in New York City

The American Museum of Natural History, located on the Upper West Side of Manhattan, New York City, is one of the largest natural history museums in the world. Located in Theodore Roosevelt Park across the street from Central Park, the museum complex comprises 28 interconnected buildings housing 45 permanent exhibition halls, in addition to a planetarium and a library. The museum collections contain over 33 million specimens of plants, animals, fossils, minerals, rocks, meteorites, human remains, and human cultural artifacts, of which only a small fraction can be displayed at any given time, and occupies more than 2 million square feet. The museum has a full-time scientific staff of 225, sponsors over 120 special field expeditions each year, and averages about five million visits annually.

<i>Kritosaurus</i> genus of reptiles (fossil)

Kritosaurus is an incompletely known genus of hadrosaurid (duck-billed) dinosaur. It lived about 74.5-66 million years ago, in the Late Cretaceous of North America. The name means "separated lizard", but is often mistranslated as "noble lizard" in reference to the presumed "Roman nose".

Sonorasaurus was finally formally described in 1998 by Ratkevich, who identified it as a brachiosaurid sauropod. Dating of the specimen found it to be the earliest known brachiosaurid to have lived in the 'middle' Cretaceous Period of North America. [3] On April 10, 2018, Sonorasaurus was declared the state dinosaur of Arizona. [4]

The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago (mya) to the beginning of the Paleogene Period 66 mya. It is the last period of the Mesozoic Era, and the longest period of the Phanerozoic Eon. The Cretaceous Period is usually abbreviated K, for its German translation Kreide.

North America Continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere

North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It is also considered by some to be a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.


The holotype of Sonorasaurus, ASDM 500, is an incomplete skeleton consisting of various postcranial elements, many of which are fragmentary. A complete dorsal rib from the same horizon, ASDM 807, may also be referrable to S. thompsoni. [3] Sonorasaurus is estimated to have been about 15  meters long (49  ft) and 8.2 meters (27 feet) tall, about one third of the size of Brachiosaurus .[ citation needed ]

Metre SI unit of length

The metre or meter is the base unit of length in the International System of Units (SI). The SI unit symbol is m. The metre is defined as the length of the path travelled by light in a vacuum in 1/299 792 458 of a second.

<i>Brachiosaurus</i> genus of reptiles (fossil)

Brachiosaurus is a genus of sauropod dinosaur that lived in North America during the Late Jurassic, about 154–153 million years ago. It was first described by American paleontologist Elmer S. Riggs in 1903 from fossils found in the Colorado River valley in western Colorado, United States. Riggs named the dinosaur Brachiosaurus altithorax; the generic name is Greek for "arm lizard", in reference to its proportionately long arms, and the specific name means "deep chest". Brachiosaurus is estimated to have been between 18 and 21 meters long; weight estimates range from 28.3 to 58 metric tons. It had a disproportionately long neck, small skull, and large overall size, all of which are typical for sauropods. Atypically, Brachiosaurus had longer forelimbs than hindlimbs, which resulted in a steeply inclined trunk, and a proportionally shorter tail.


Ratkevich initially identified Sonorasaurus as a brachiosaurid. [3] However phylogenetic studies in the following years failed to find a consensus, with some finding it to lie within Brachiosauridae [5] and others outside of it. [6] In no analysis was the recovered phylogenetic position of Sonorasaurus strongly supported until D'Emic et al. (2016), which found Sonorasaurus to fall confidently within the Brachiosauridae. However the authors noted that additional data was still required to firmly establish its lower-level affinities. [7]

Related Research Articles

<i>Hadrosaurus</i> genus of hadrosaurid dinosaur (fossil)

Hadrosaurus is a valid genus of hadrosaurid dinosaur that lived in North America during the Late Cretaceous Period.

<i>Sauroposeidon</i> genus of reptiles (fossil)

Sauroposeidon is a genus of sauropod dinosaur known from several incomplete specimens including a bone bed and fossilized trackways that have been found in the American states of Oklahoma, Wyoming, and Texas. The fossils were found in rocks dating from near the end of the Early Cretaceous, a time when sauropod diversity in North America had greatly diminished. It was the last known North American sauropod prior to an absence of the group on the continent of roughly 40 million years that ended with the appearance of Alamosaurus during the Maastrichtian.

<i>Acrocanthosaurus</i> Cacharodontosaurid theropod dinosaur genus from the Early Cretaceous period

Acrocanthosaurus is a genus of theropod dinosaur that existed in what is now North America during the Aptian and early Albian stages of the Early Cretaceous. Like most dinosaur genera, Acrocanthosaurus contains only a single species, A. atokensis. Its fossil remains are found mainly in the U.S. states of Oklahoma, Texas, and Wyoming, although teeth attributed to Acrocanthosaurus have been found as far east as Maryland.

Titanosauria class of reptiles

Titanosaurs were a diverse group of sauropod dinosaurs which included Saltasaurus and Isisaurus. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still thriving at the time of the extinction event at the end of the Cretaceous. The group includes the largest land animals known to have existed, such as Patagotitan—estimated at 37 m (121 ft) long with a weight of 69 tonnes —and the comparably sized Argentinosaurus and Puertasaurus from the same region. The group's name alludes to the mythological Titans of Ancient Greece, via the type genus Titanosaurus. Together with the brachiosaurids and relatives, titanosaurs make up the larger clade Titanosauriformes.

Jobaria is a genus of sauropod dinosaur that lived in what is now Niger during the middle Jurassic Period, between 164–161 million years ago.

<i>Astrodon</i> genus of reptiles (fossil)

Astrodon is a dubious genus of large herbivorous sauropod dinosaur, related to Brachiosaurus, that lived in what is now the eastern United States during the Early Cretaceous period. Its fossils have been found in the Arundel Formation, which has been dated through palynomorphs to the Albian about 112 million years ago. Adults are estimated to have been more than 9 m (30 ft) high and 15 to 18 m long.

<i>Isisaurus</i> genus of reptiles (fossil)

Isisaurus is a genus of dinosaur from the Late Cretaceous Period. Isisaurus was a sauropod, which lived in what is now India.

<i>Lusotitan</i> genus of reptiles (fossil)

Lusotitan is a genus of herbivorous brachiosaurid sauropod dinosaur from the Late Jurassic Period of Portugal.

<i>Europasaurus</i> genus of reptiles (fossil)

Europasaurus is a basal macronarian sauropod, a form of quadrupedal herbivorous dinosaur. It lived during the Late Jurassic of northern Germany, and has been identified as an example of insular dwarfism resulting from the isolation of a sauropod population on an island within the Lower Saxony basin.

<i>Qiaowanlong</i> genus of reptiles (fossil)

Qiaowanlong is a genus of sauropod dinosaur. Fossils belonging to the genus were found in 2007 from the Yujinzi Basin of Gansu, China, and were described in 2009 in the Proceedings of the Royal Society B. The remains come from a geological formation called the Xinminpu Group, dating to the Early Cretaceous about 100 Ma. The only known specimen consists of articulated cervical (neck) vertebrae and a right pelvic girdle, as well as several unidentified bone fragments. Qiaowanlong was initially reported as the first brachiosaurid to have been found from China. However, later analysis found that it was more closely related to titanosauriformes like Euhelopus and Erketu. It is estimated to have had a length of around 12 metres (39 ft) and would have weighed around 6 tonnes. The type species is Q. kangxii.


Laurasiformes is an extinct clade of sauropod dinosaurs from the late Early Cretaceous of Europe, North and South America. It was defined in 2009 by the Spanish paleontologist Rafael Royo-Torres as a clade containing sauropods more closely related to Tastavinsaurus than to Saltasaurus. Genera purported to form part of this clade include Aragosaurus, Galvesaurus, Phuwiangosaurus, Venenosaurus, Cedarosaurus, Tehuelchesaurus, Sonorasaurus and Tastavinsaurus.

Paleontology in Arizona

Paleontology in Arizona refers to paleontological research occurring within or conducted by people from the U.S. state of Arizona. The fossil record of Arizona dates to the Precambrian. During the Precambrian, Arizona was home to a shallow sea which was home to jellyfish and stromatolite-forming bacteria. This sea was still in place during the Cambrian period of the Paleozoic era and was home to brachiopods and trilobites, but it withdrew during the Ordovician and Silurian. The sea returned during the Devonian and was home to brachiopods, corals, and fishes. Sea levels began to rise and fall during the Carboniferous, leaving most of the state a richly vegetated coastal plain during the low spells. During the Permian, Arizona was richly vegetated but was submerged by seawater late in the period.

Astrophocaudia is a genus of somphospondylan sauropod known from the late Early Cretaceous of Texas, United States. Its remains were discovered in the Trinity Group. The type species is Astrophocaudia slaughteri, described in 2012 by Michael D. D’Emic while a doctoral student at the Museum of Paleontology of the University of Michigan, USA.

Paluxysuchus is an extinct genus of neosuchian crocodyliform known from the Early Cretaceous Twin Mountains Formation of north-central Texas. It contains a single species, Paluxysuchus newmani. Paluxysuchus is one of three crocodyliforms known from the Early Cretaceous of Texas, the others being Pachycheilosuchus and an unnamed species referred to as the "Glen Rose Form". Paluxysuchus has a long, flat skull that is probably transitional between the long and narrow skulls of many early neosuchians and the short and flat skulls of later neosuchians.

<i>Padillasaurus</i> Sauropod dinosaur of Colombia

Padillasaurus is an extinct genus of titanosauriform sauropod known from the Early Cretaceous Paja Formation in Colombia. It contains a single species, Padillasaurus leivaensis, known only from a single partial axial skeleton. Initially described as a brachiosaurid, it was considered to be the first South American brachiosaurid ever discovered and named. Before its discovery, the only known brachiosaurid material on the continent was very fragmentary and from the Jurassic period. However, a more recent study finds it to be a basal somphospondylan.

<i>Vouivria</i> genus of reptiles

Vouivria is a genus of herbivorous sauropod dinosaurs, belonging to the Brachiosauridae, that lived in the area of present France during the Late Jurassic. The type species is Vouivria damparisensis.

<i>Soriatitan</i> genus of sauropod dinosaur found in Spain

Soriatitan is a genus of brachiosaurid sauropod from the Early Cretaceous of Spain. It is known from one species, S. golmayensis, found in the Golmayo Formation. It lived between 138 to 130 million years ago was identified by a team of paleontologists in Spain.

Zhuchengtitan is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous of Shandong, China. It contains a single species, Z. zangjiazhuangensis, named by Mo Jinyou and colleagues in 2017 from a single humerus. Zhuchengtitan can be identified by the extreme width of the top end of its humerus, as well as the expansion of the deltopectoral crest on its humerus; both of these characteristics indicate that it was likely closely related to Opisthocoelicaudia. However, it differs from the latter by the flatter bottom articulating surface of its humerus. Zhuchengtitan lived in a floodplain environment alongside Shantungosaurus, Zhuchengtyrannus, and Sinoceratops.


  1. Thayer D.W. and Ratkevich R., 1995, "In progress dinosaur excavation in the mid-cretaceous Turney Ranch Formation, southeastern Arizona", Proceedings of the Fossils of Arizona Symposium. Bulletin No.3., Mesa Southwest Museum, Southwest Paleontological Society
  2. David W. Thayer, Ronald P. Ratkevich & Stan E. Krzyzanowski, 1996, "A new Dinosaur for the Arizona-Sonora Desert Museum Tucson, Arizona", Rocks & Minerals, 71(1): 34-38
  3. 1 2 3 Ratkevich, R. (1998). "New Cretaceous brachiosaurid dinosaur, Sonorasaurus thompsoni gen. et sp. nov, from Arizona". Journal of the Arizona-Nevada Academy of Science. 31 (1): 71–82.
  5. Royo-Torres, R. (2009). "El saurópodo de Peñarroya de Tastavins". Instituto de Estudios Turolenses-Fundación Conjunto Paleontológico de Teruel-Dinópolis: Monografías Turolenses. 6: 1–548.
  6. D’Emic, M.D. (2012). "The early evolution of titanosauriform sauropod dinosaurs". Zoological Journal of the Linnean Society. 166: 624–671.
  7. D'Emic, M.D.; Foreman, B.Z.; Jud, N.A. (2016). "Anatomy, systematics, paleoenvironment, growth, and age of the sauropod dinosaur Sonorasaurus thompsoni from the Cretaceous of Arizona, USA". Journal of Paleontology. 90 (1): 102–132. doi:10.1017/jpa.2015.67.