Dicraeosauridae is a family of diplodocoid sauropods who are the sister group to Diplodocidae. Dicraesaurids are a part of the Flagellicaudata, along with Diplodocidae. Dicraeosauridae includes genera such as Amargasaurus, Suuwassea, Dicraeosaurus, and Brachytrachelopan. Specimens of this family have been found in North America, Africa, and South America. Their temporal range is from the Early or Middle Jurassic to the Early Cretaceous. Few dicraeosaurids survived into the Cretaceous, the youngest of which was Amargasaurus.
The group was first described by German paleontologist Werner Janensch in 1914 with the discovery of Dicraeosaurus in Tanzania. Dicraeosauridae are distinct from other sauropods because of their relatively short neck size and small body size.
The clade is monophyletic and well-supported phylogenetically with thirteen unambiguous synapomorphies uniting it. They diverged from Diplodocidae in the Mid-Jurassic, as evidenced by the diversity of dicraeosaurids in both South America and East Africa when Gondwana was still united by land. However, there is some disagreement among paleontologists on the phylogenetic placement of Suuwassea, the only genera of the Dicraeosauridae to be found in North America. It has been characterized as a basal dicraeosaurid by some and a member of the Diplodocidae by others. The placement of Suuwassea within Dicraeosauridae or Diplodocidae has substantial biogeographic implications for the evolution of Dicraeosauridae.
Dicraeosaurids are a part of Diplodocoidea and are the sister group to Diploidocidae. In the past two decades, the known diversity of the group has doubled. However, the classification of Suuwassea as a dicraeosaurid is not universally agreed upon. Some phylogenetic analyses have found Suuwassea to be a basal diplodocoid instead of a dicraeosaurid. One 2015 analysis has even found Dyslocosaurus as a member of Dicraeosauridae. A 2016 reappraisal of Amargatitanis has placed it into the Dicraeosauridae, as well. In 2018 a new genus, Pilmatueia, was described.
Dicraeosaurids are differentiated from their sister group, diplodocids, and from most sauropods by their relatively small body size and short necks. Dicraeosaurids are advanced sauropods within the monophyletic clade Neosauropoda, which is generally characterized by gigantism. The relatively small body size of dicraeosaurids make them an important outlier relative to other taxa in Neosauropoda.
There have been several different proposed phylogenies of Dicraeosauridae and the intra-group cladistics are not resolved. Suuwassea is variably positioned as either a basal dicraeosaurid or a basal diplodocoid. The most recently published phylogeny by Tschopp et al. (2015) is as follows:
Tschopp includes Dyslocosaurus and Dystrophaeus as dicraeosaurids, two groups traditionally not considered to be part of Dicraeosauridae. The specimens of Dystrophaeus viamelae are highly fragmentary, with only a few bones available for study including an ulna, partial scapula, partial dorsal vertebrae, a distal radius, and some metacarpals. Dyslocosaurus polyonychius also has extremely limited fossil evidence that only includes appendicular elements, and the position of it in Tschopp's phylogeny is therefore considered "preliminary".
Several studies, however, do not include even Suuwassea in Dicraeosauridae, like Sereno et al. (2007); and JD Harris (2006). Other studies, however, do include Suuwassea as a basal dicraeosaurid, including Whitlock (2010) and Salgado et al. (2006).
As sauropods, dicraeosaurids are obligate herbivores. Due to their relatively small necks and skull shape, it has been deduced that dicraeosaurids and diplodocids primarily browsed close to the ground or at mid height. Among the dicraeosurids, only Dicraeosaurus has well-preserved dentition. This makes it difficult for paleontologists to make definitive statements about Dicraeosauridae feeding behavior compared to diplodocid feeding behavior. However, compared to its known relatives, Dicraeosaurus is unique in that it has an equal number of teeth in the upper and lower jaw, though teeth in the lower jaw are replaced more slowly.
Dicraeosaurids are characterized by their relatively small body size, short necks, and long neural spines. They are 10–13 meters in body length. They share thirteen unambiguous synapomorphies including dorsal vertebrae without pleurocoels, the presence of a ventrally directed prong on the squamosal, and a subtriangular-shaped dentary symphysis.
Dicraeosaurid specimens have been found in three continents - Africa, South America, and North America. The distribution of species is primarily Gondwonan, with the exception of the North American Suuwassea. The presence of Suuwassea in North America is unique among dicraeosaurids, therefore making the proper taxonomic classification of Suuwassea essential. The group likely first diverged from the diplodocids in the middle Jurassic in North America and subsequently dispersed into Gondwana, with the most diversity in East Africa and South America. Amargasaurus was the latest surviving dicraeosaurid genus, living into the Early Cretaceous period.
Amargasaurus (; "La Amarga lizard") is a genus of sauropod dinosaur from the Early Cretaceous epoch (129.4–122.46 mya) of what is now Argentina. The only known skeleton was discovered in 1984 and is virtually complete, including a fragmentary skull, making Amargasaurus one of the best-known sauropods of its epoch. Amargasaurus was first described in 1991 and contains a single known species, Amargasaurus cazaui. It was a large animal, but small for a sauropod, reaching 9 to 10 meters (30 to 33 feet) in length. Most distinctively, it sported two parallel rows of tall spines down its neck and back, taller than in any other known sauropod. In life, these spines most likely could have stuck out of the body as solitary structures that supported a keratinous sheath. An alternate hypothesis, now less favored, postulates that they could have formed a scaffold supporting a skin sail. They might have been used for display, combat, or defense.
Amargasaurus was discovered in sedimentary rocks of the La Amarga Formation, which dates back to the Barremian and late Aptian stages of the Early Cretaceous. A herbivore, it shared its environment with at least three other sauropod genera, which might have exploited different food sources in order to reduce competition. Amargasaurus probably fed at mid-height, as shown by the orientation of its inner ear and the articulation of its neck vertebrae, which suggest a habitual position of the snout 80 centimeters (31 inches) above the ground and a maximum height of 2.7 meters (8.9 feet). Within the Sauropoda, Amargasaurus is classified as a member of the family Dicraeosauridae, which differs from other sauropods in showing shorter necks and smaller body sizes.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.Bajadasaurus
Bajadasaurus is a genus of sauropod dinosaur from the Early Cretaceous epoch (late Berriasian to Valanginian stages) of northern Patagonia, Argentina. It was first described in 2019 based on a single specimen found in 2010 that includes a largely complete skull and parts of the neck. The only species is Bajadasaurus pronuspinax. The genus is classified as a member of the Dicraeosauridae, a group of comparatively small and short-necked sauropods that lived from the Early or Middle Jurassic to the end of the Early Cretaceous.
Bajadasaurus sported bifurcated, extremely elongated neural spines extending from the neck vertebrae. Similar elongated spines are known from the closely related and more completely known Amargasaurus. Various possible functions have been proposed for these spines in Amargasaurus, with the 2019 description of Bajadasaurus suggesting that they could have served as passive defense against predators in both genera. The skull was gracile and equipped with around 44 teeth that were pencil-shaped and restricted to the front of the jaws. The eye openings of Bajadasaurus were exposed in top view of the skull, possibly allowing the animal to look forwards while feeding. Bajadasaurus was discovered in sedimentary rocks of the Bajada Colorada Formation, and its environment resembled a braided river system. It shared its environment with other dinosaurs including the sauropod Leinkupal and different theropods.Brachytrachelopan
Brachytrachelopan is a short-necked sauropod dinosaur from the Late Jurassic (Oxfordian to Tithonian) of Argentina. The holotype and only known specimen (Museo Paleontológico Egidio Feruglio MPEF-PV 1716) was collected from an erosional exposure of fluvial sandstone within the Cañadón Calcáreo Formation on a hill approximately 25 kilometres (16 mi) north-northeast of Cerro Cóndor, Chubut Province, in west-central Argentina, South America. Though very incomplete, the skeletal elements recovered were found in articulation and include eight cervical, twelve dorsal, and three sacral vertebrae, as well as proximal portions of the posterior cervical ribs and all the dorsal ribs, the distal end of the left femur, the proximal end of the left tibia, and the right ilium. Much of the specimen was probably lost to erosion many years before its discovery. The type species is Brachytrachelopan mesai. The specific name honours Daniel Mesa, a local shepherd who discovered the specimen while searching for lost sheep. The genus name translates as "short-necked Pan", Pan being the god of the shepherds.Daxiatitan
Daxiatitan is a genus of titanosaur dinosaur from the Lower Cretaceous of Lanzhou Basin, Gansu Province, northwestern China. It is known from fossils including several neck vertebrae, a shoulder blade, and a thigh bone.It was a very large dinosaur, estimated at 23–30 meters (75–98 feet). Like both Euhelopus and Huanghetitan, it had an enormously long neck.Dicraeosaurus
Dicraeosaurus (Gr. δικραιος, dikraios "bifurcated, double-headed" + Gr. σαυρος, sauros "lizard") is a genus of small diplodocoid sauropod dinosaur that lived in what is now Tanzania during the late Jurassic. It was named for the spines on the back of the neck. The first fossil was described by paleontologist Werner Janensch in 1914.Diplodocimorpha
Diplodocimorpha is a clade of extinct sauropod dinosaurs, existing from the Early Jurassic until the Late Cretaceous. The group includes three main families and some other genera, Rebbachisauridae, Dicraeosauridae and Diplodocidae, the latter two forming Flagellicaudata. The name was first used by Calvo & Salgado (1995), who defined it as "Rebbachisaurus tessonei sp. nov., Diplodocidae, and all descendants of their common ancestor." The group was not used often, and was synonymized with Diplodocoidea as the groups were often found to have the same content. In 2005, Mike P. Taylor and Darren Naish reviewed diplodocoid phylogeny and taxonomy, and realized that Diplodocimorpha could not be synonymized with Diplodocoidea. Whereas the former was defined node-based, the latter was branch-based. In 2015, Emanuel Tschopp, Octavio Mateus and Roger Benson published a specimen-based phylogeny on diplodocid interrelationships, and supported the separation of Diplodocimorpha. Haplocanthosaurus was found to be more basal than rebbachisaurids, and therefore outside Diplodocimorpha, but closer to Diplodocus than Saltasaurus, and therefore within Diplodocoidea. The below cladogram follows the findings of Tschopp et al.Diplodocoidea
Diplodocoidea is a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like Supersaurus, Diplodocus, Apatosaurus, and Amphicoelias. Most had very long necks and long, whip-like tails; however, one family (the dicraeosaurids) are the only known sauropods to have re-evolved a short neck, presumably an adaptation for feeding low to the ground. This adaptation was taken to the extreme in the highly specialized sauropod Brachytrachelopan. A study of snout shape and dental microwear in diplodocoids showed that the square snouts, large proportion of pits, and fine subparallel scratches in Apatosaurus, Diplodocus, Nigersaurus, and Rebbachisaurus suggest ground-height nonselective browsing; the narrow snouts of Dicraeosaurus, Suuwassea, and Tornieria and the coarse scratches and gouges on the teeth of Dicraeosaurus suggest mid-height selective browsing in those taxa. This taxon is also noteworthy because diplodocoid sauropods had the highest tooth replacement rates of any vertebrates, as exemplified by Nigersaurus, which had new teeth erupting every 30 days.Dyslocosaurus
Dyslocosaurus (meaning "hard-to-place lizard") is the name given in 1992 to a genus of sauropod dinosaur from the Late Jurassic Period of Wyoming, North America.
The holotype or type specimen the genus is based on, AC 663, is part of the collection of the Amherst College Museum of Natural History. It was collected by professor Frederic Brewster Loomis. However, the only available information regarding its provenance is that given on the label: "Lance Creek", a county in east Wyoming. Loomis himself thought that it stemmed from the Lance Formation, dating from the Late Cretaceous Maastrichtian.
In 1963 the specimen was brought to the attention of John Stanton McIntosh, who in 1992, together with William Coombs and Dale Russell, decided to create a new genus and species for it. The type species is Dyslocosaurus polyonychius. The genus name is derived from Greek dys, "bad, "poor", and Latin locus, "place", a reference to the paucity of data regarding the type locality of the fossil. The specific name is derived from Greek polys, "many", and onyx, "claw". The describers interpreted the remains, consisting of some limb bones, as those of a diplodocid dinosaur. From this they concluded that it in fact dated from the Late Jurassic Period, like most diplodocids. The species would then be unique in having four, or perhaps five, claws on the foot, whereas other diplodocids have only three — hence the specific name. A species similar to Dyslocosaurus would have made the tracks of the ichnospecies Brontopodus birdi from the Early Cretaceous, that also features four claws.
In 1998 Paul Sereno and Jeffrey A. Wilson gave an alternative interpretation: the specimen would come from the Lance Formation after all but be a chimera: in this case a mix up of titanosaur limb bones and theropod phalanges.
In their taxonomic revision of Diplodocidae, Tschopp et alii in 2015 noted that a pedal phalanx included in AC 663 is apparently not from the same individual as the rest of AC 663 given differences in preservation and coloration among individual bones, raising doubts on whether Dyslocosaurus had more than three claws on the feet. Although fragmentary, Dyslocosaurus was recovered as a member of Dicraeosauridae, potentially making it the second record of a dicraeosaurid from North America (the other being Suuwassea).Dystrophaeus
Dystrophaeus is the name given to an extinct genus of eusauropod dinosaur from the early Kimmeridgian stage of the Late Jurassic that existed around 154.8 Ma. Its fossils were found in the Tidwell Member of the Morrison Formation of Utah. Its estimated mass is 12 tonnes (13 short tons).The type species, D. viaemalae, was described by Edward Drinker Cope in 1877. The genus name means "coarse joint" from Greek dys, "bad", and stropheus, "joint", a reference to the pitted joint surfaces serving as an attachment for cartilage. The specific name reads as Latin viae malae, "of the bad road", a reference to the various arduous routes taken to find, reach and salvage the remains. It consists of one partial skeleton, the holotype USNM 2364, which includes a 76 centimetre long ulna, a scapula, a partial radius, and some metacarpals discovered in August 1859 by John Strong Newberry. It was found in what is possibly stratigraphic zone 1 of the Morrison, although an older Oxfordian-Callovian has also been suggested. Dystrophaeus represents one of the oldest discoveries of sauropods in America; earlier, in 1855, some teeth had been found of Astrodon.
The classification of Dystrophaeus has been rather confusing. Cope in 1877 merely concluded it was some Triassic dinosaur. Henri-Émile Sauvage in 1882 understood it was a sauropod, assigning it to the Atlantosauridae. Othniel Charles Marsh however, in 1895 stated it belonged to the Stegosauridae. Friedrich von Huene, the first to determine it was of Jurassic age, in 1904 created a special family for it, the Dystrophaeidae, which he assumed to be herbivorous theropods. Only in 1908 von Huene realised his mistake and classified it in the sauropod Cetiosauridae, refining this in 1927 to the Cardiodontinae. Alfred Romer in 1966 put it in the Brachiosauridae, in a subfamily Cetiosaurinae.
More recently, an analysis by David Gillette concluded it was a member of the Diplodocidae. Another recent review, by Tschopp and colleagues in 2015, suggest it is a member of the Dicraeosauridae. However, many researchers consider the taxon to be a nomen dubium.Eusauropoda
Eusauropoda (meaning "true sauropods") is a derived clade of sauropod dinosaurs. Eusauropods represent the node-based group that includes all descendant sauropods starting with the basal eusauropods of Shunosaurus, and possibly Barapasaurus, and Amygdalodon, but excluding Vulcanodon and Rhoetosaurus. The Eusauropoda was coined in 1995 by Paul Upchurch to create a monophyletic new taxonomic group that would include all sauropods, except for the vulcanodontids.Eusauropoda are herbivorous, quadrupedal, and have long necks. They have been found in South America, Europe, North America, Asia, Australia, and Africa. The temporal range of Eusauropoda ranges from the early Jurassic to the Latest Cretaceous periods. The most basal forms of eusauropods are not well known and because the cranial material for the Vulcanodon is not available, and the distribution of some of these shared derived traits that distinguish Eusauropoda is still completely clear.Flagellicaudata
Flagellicaudata is a clade of Dinosauria. It belongs to Sauropoda and includes two families, the Dicraeosauridae and the Diplodocidae.Gravisauria
Gravisauria is a clade of sauropod dinosaurs consisting of some genera, Vulcanodontidae and Eusauropoda.Huangshanlong
Huangshanlong is a genus of mamenchisaurid dinosaurs native to the Anhui province of China. It contains a single species, Huangshanlong anhuiensis. H. anhuiensis represents, along with Anhuilong and Wannanosaurus, one of three dinosaurs fround in Anhui province.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.Lingwulong
Lingwulong is a genus of dicraeosaurid sauropod dinosaur from the Early or Middle Jurassic Yanan Formation in Lingwu, Yinchuan, Ningxia Hui, China. The type and only species is L. shenqi, known from several partial skeletons. It is the earliest-aged neosauropod ever discovered, as well as the only definite diplodocoid from east Asia. Its exact age is uncertain, but it lived between the late Toarcian and Bajocian ages, with an midpoint estimate age of 174 Ma.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.Pilmatueia
Pilmatueia is a diplodocoid sauropod belonging to the family Dicraeosauridae that lived in Argentina during the Early Cretaceous.Suuwassea
Suuwassea (meaning "ancient thunder") is a genus of dicraeosaurid sauropod dinosaur found in the Upper Jurassic strata of the Morrison Formation, located in southern Carbon County, Montana, United States. The fossil remains were recovered in a series of expeditions during a period spanning the years 1999 and 2000, described by J.D. Harris and Peter Dodson in 2004. They consist of a disarticulated but associated partial skeleton, including partial vertebral series and limb bones.