| Euhelopus | |
|---|---|
 | |
| Reconstructed skeleton in Japan | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauriformes |
| Clade: | †Somphospondyli |
| Family: | †Euhelopodidae |
| Genus: | †Euhelopus Romer, 1956 |
| Type species | |
| †Euhelopus zdanskyi (Wiman, 1929) | |
| Synonyms | |
| |
Euhelopus is agenus ofsauropoddinosaur that lived between 143 and 133 million years ago during theBerriasian andValanginian ages of theEarly Cretaceous[1] in what is nowShandong Province inChina. It was a largequadrupedalherbivore. Like sauropods such as brachiosaurids and titanosaurs,Euhelopus had longer forelimbs than hindlimbs. This discovery waspaleontologically significant because it represented the first dinosaur scientifically investigated from China: seen in 1913, rediscovered in 1922, excavated in 1923, and studied by T'an during the same year.[2] Unlike most sauropod specimens, it has a relatively complete skull.[3]Euhelopus was a long-necked sauropod similar toMamenchisaurus, but its affinities are controversial. Most studies favor a close relationship betweenEuhelopus and titanosaurs, rather than mamenchisaurids.
Since its original description,Euhelopus has often been considered a rather large sauropod. It has been thought to weigh about 15–20 tonnes (17–22 short tons) and attain an adult length of 15 metres (49 ft).[4] Later estimates have downsized this considerably. In 2016,Gregory S. Paul estimated the weight at 3.5 tonnes (3.9 short tons) and the body length at 11 metres (36 ft).[5] Bensonet al. estimated its mass at 5.9 tonnes (6.5 short tons),[6] whereas Larramendiet al. estimated it at 3.6 tonnes (4.0 short tons).[7]
Euhelopus was a relatively long-necked sauropod, with a 4-meter neck[8] composed of 17 cervical vertebrae.[a] The presacral vertebrae had a camellate pneumatic structure, made of many small pneumatic chambers, as is characteristic of titanosauriforms and some mamenchisaurids.[1][9] Pneumatic chambers even extended into the ilium,[1] as occurs in many titanosaurs.[10] The humerus was apparently nearly as long as the femur, although there is some uncertainty in this ratio, as it is not certain that the humerus and femur from which this ratio was calculated belong to the same individual, and the femur in question is incomplete.[1]
The original diagnosis by Wiman is outdated. A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some of the features in a diagnosis may be autapomorphies. Anautapomorphy is a distinctive anatomical feature that is unique to an organism or group.
According to a study byJeffrey A. Wilson andPaul Upchurch in 2009,Euhelopus can be distinguished based on, among others, these autapomorphies:[1]
The original discovery was by a Catholic priest, Father R. Mertens, in 1913. He showed some remains he had excavated to the German mining engineer Gustav Behaghel who in 1916 sent three vertebrae to the head of the Geological Survey of ChinaDing Wenjiang ("V.K. Ting"). This was probably the first occasion dinosaur bones fromChina were scientifically studied. With help of another Catholic priest, Father Alfred Kaschel, the site was rediscovered in November 1922 byJohan Gunnar Andersson andTan Xichou. In March 1923, the Austrian studentOtto Zdansky excavated two skeletons at sites about three kilometres apart and the holotype was studied by H. C. T'an, also in 1923.[2]
It was originally described and namedHelopus, meaning "Marsh Foot", by the Swedish paleontologistCarl Wiman in 1929, after the Greek ἕλος,helos, "swamp", and πούς,pous, "foot".[11] The name refers to the marshy area of the finds and totruga, Swedish swamp shoes, which according to Wiman resembled the wide feet of the animal.[11] This name however, already belonged to a bird because theCaspian tern had once been namedHelopus caspius Wagler 1832. The sauropod dinosaur was therefore renamedEuhelopus (True marsh-foot) in 1956 byAlfred Sherwood Romer.[12] There proved to be a plant genus (agrass) with the samegeneric name,Euhelopus. However, a genus in onebiological kingdom may have a name that is used as a genus name in another kingdom, soEuhelopus was allowed. Thetype species isHelopus zdanskyi. Thecombinatio nova isEuhelopus zdanskyi. Thespecific name honours Zdansky.[11]
SpecimenPMU 24705 (formerly PMU R233) forms according to Wilson & Upchurch theholotype,[1] descriptive basis, for the speciesEuhelopus zdanskyi.[3] It represents one of the skeletons found by Zdansky, named "Exemplar a" by Wiman, who did not formally assign a holotype.[11] This is the original skeleton found by Mertens.[11] Specimen PMU 24705 consists of a partial skeleton with skull and lower jaws comprising these bones: the rostral part of the left nasal; a partial right jugal; the tapered jugal process of the postorbital, partially excavated; the dorsal process of the right quadratojugal; the fragmented left pterygoid (another fragment might be the right splenial, but it is too fragile to be removed from its matrix),[3] a series of twenty-five presacral vertebrae and the left thighbone.[11]
The second skeleton, of an individual about as large as the holotype, was designated "Exemplar b" by Wiman.[11] It was by Wilson & Upchurch referred toEuhelopus. This specimen PMU 24706, formerly PMU 234, comprises nine articulated dorsalvertebrae and thesacrum, two dorsal ribs, a nearly completepelvis, and a right hindlimb lacking the fifth metatarsal and several pedal phalanges.[4]
Both specimens are housed in the collection of thePaleontological Museum of Uppsala University, inUppsala,Sweden, where the mounted skeletons are displayed since the 1930s.[1]
In 1923, Zdansky lacked the time to finish the excavation of the holotype.[11] In the autumn of 1934,C. C. Young and M. N. Bien returned to the locality and recovered a left scapulocoracoid, right coracoid and right humerus. Young described these remains, as well as the vertebrae Behagel had sent to Ting, in 1935. Young assigned all of these remains toEuhelopus zdanskyi except the incomplete right coracoid, and suggested that they probably belonged to the type specimen.[13] Yang and Bien's scapulocoracoid and humerus and Ting's vertebrae were designated "exemplar c" by Wilson & Upchurch in 2009. They were informed in 2007 that this material could no longer be located in the Chinese collections.[1]
Wiman in 1929 was uncertain about the affinities ofHelopus and placed it in a Helopodidae of its own.[11] Yang made this a Helopodinae, first within theMorosauridae, then within theBrachiosauridae. Romer in 1956 created a Euhelopodinae.[12] In 1990,John Stanton McIntosh placedEuhelopus in theCamarasauridae.[14]
The phylogenetic affinities ofEuhelopus are controversial, and it has been variously interpreted as having close affinities toMamenchisaurus-like taxa[15][9] or as being grouped together with titanosaurs in the cladeSomphospondyli.[16][1][17] The clade containingEuhelopus and its close relatives is known as Euhelopodidae, but the ambiguity overEuhelopus's affinities has caused considerable uncertainty regarding the membership of Euhelopodidae.[17] Most studies favor the somphospondyl hypothesis forEuhelopus, but the lack of research on the anatomy ofMamenchisaurus-like sauropods has inhibited a rigorous test of the relationship between them andEuhelopus.[9]
Wilson and Upchurch (2009) noted that cladistic assessments suggest thatEuhelopus belonged to a clade of sauropods, the Euhelopodidae, that originated during an interval of geographic isolation and was endemic to this geographical range in China. It is not clear if the Euhelopodidae are monophyletic.[1]Euhelopus demonstrates phylogenetic affinity to the taxonTitanosauria. Traditional claims thatEuhelopus,Omeisaurus,Mamenchisaurus andShunosaurus form the monophyletic family "Euhelopodidae" are not supported by new phylogenetic analysis.[18]The cladogram below follows José L. Carballido, Oliver W. M. Rauhut, Diego Pol and Leonardo Salgado (2011).[18]
The type material forEuhelopus was excavated at theMengyin Formation in Shandong (Shantung) Province, China. The specimens were collected by Otto Zdansky in 1923, in green/yellow sandstone and green/yellow siltstone.
The Mengyin Formation dates to theBerriasian-Valanginian.[19] It was previously regarded as having been deposited during theBarremian orAptianstages of theCretaceous period, about 129 to 113 million years ago. During the 1990s it was mistakenly thought the formation might date from theLate Jurassic.[1]
