| Venenosaurus | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Family: | †Brachiosauridae |
| Genus: | †Venenosaurus Tidwellet al., 2001 |
| Species: | †V. dicrocei |
| Binomial name | |
| †Venenosaurus dicrocei Tidwellet al., 2001 | |
Venenosaurus (/vɛˌnɛnoʊˈsɔːrəs/ven-EN-o-SOR-əs) is a genus ofsauropoddinosaur that lived in what is now Utah during the Early Cretaceous. Its type and only species isVenenosaurus dicrocei. Fossils ofVenenosaurus were first discovered in 1998, by Denver Museum of Natural History volunteer Anthony DiCroce, and described as a new genus and species in 2001 by Virginia Tidwell and colleagues, who named the species for DiCroce.Venenosaurus was a relatively small sauropod, and was similar toCedarosaurus, another sauropod from the Early Cretaceous of Utah.
In the spring of 1998, a team of volunteers for theDenver Museum of Natural History[a], including Anthony "Tony" DiCroce, found a fossil site in Grand County, Utah, which they named Tony's Bone Bed.[1] The bone bed was in the Poison Strip Member of theCedar Mountain Formation, and contained the remains of the iguanodontPlanicoxa, a theropod, and an adult and juvenile of a sauropod.[2] In 2001, Virginia Tidwell, Kenneth Carpenter, and Susanne Meyer described the sauropod remains as a new genus and species,Venenosaurus dicrocei. The genus name comes from the Latinveneno, "poison", in reference to the Poison Strip Member, and the species name honors DiCroce for his discovery of the fossils.[3]
Venenosaurus fossils are known from the Poison Strip Member of theCedar Mountain Formation, including theholotype, DMNS 40932, a partial skeleton of an adult individual, which consists of nine tailvertebrae, the leftscapula, rightradius, leftulna,metacarpals,forefoot phalanges, rightpubis, left and rightischia,metatarsals,chevrons, andribs.[4] A few bones of a juvenile individual are also known from the same site.[5] These specimens are housed at the Denver Museum of Nature and Science. Additional specimens ofVenenosaurus have been reported from Dalton Wells Quarry, in the Yellow Cat Member of the Cedar Mountain Formation, comprising the fragmentary remains of least three individuals.[6] However, it is not certain whether these specimens belong toVenenosaurus or its close relativeCedarosaurus.[7]
The scientists who first describedV. dicrocei observed that the new species most closely resemblesCedarosaurus, while still being distinct.[8]Venenosaurus is a relatively smalltitanosauriform sauropod, measuring 12 metres (39 ft) long and weighing 6 metric tons (6.6 short tons).[9]
Theradius ofVenenosaurus is more slender than the radii ofAlamosaurus,Chubutisaurus,Opisthocoelicaudia, andSaltasaurus.[10] The ratio of the radius' least circumference to length produces a ratio of .33, more gracile than the radius ofCamarasaurus lewisi andC. grandis.Cedarosaurus, however, has a slightly more gracile ratio of .31.[10] The team found thatBrachiosaurus brancai's radius is the closest anatomical match to that ofVenenosaurus.[10] The metacarpals ofVenenosaurus are long and slender.[10] With the exception of the incomplete first metacarpal, all of the right metacarpals are known.[10] Metatarsal I is the shortest and most robust of the three recovered metatarsals.[11]Cedarosaurus had a more gracileulna and radius thanVenenosaurus.[12]
Venenosaurus shows a mixture of titanosaur and non-titanosaurischium-to-pubis proportions.[13] Its hips most closely resemble those ofBrachiosaurus.[13]
The vertebrae in the middle and toward the end of the tail were short, distinguishing it fromtitanosaurs likeAndesaurus,Malawisaurus,Aeolosaurus,Alamosaurus, andSaltasaurus.[14] The neural spines in the middle tail vertebrae are angled toward the front of the animal.[15] These vertebrae resemble those ofCedarosaurus,Aeolosaurus, andGondwanatitan.[15] The vertebrae are located at a transitional position from anterior to posterior caudal vertebrae.[15]
Venenosaurus had unusual lateral fossae, which looked like deep depressions in the outside walls of the vertebral centra.[16] Some fossae are divided into two chambers by a ridge inside the depression.[16] In most sauropods the fossae would form pneumatic openings leading to the interior of the centrum, rather than just being a depression.[16] Less well-developed, but similar fossae are known fromCedarosaurus.[16] Fossae that similarly resemble shallow depressions are known fromSaltasaurus,Alamosaurus,Aeolosaurus,Gondwanatitan, andMalawisaurus.[16] These taxa differ, however, in that their fossae are even shallower, lack the division into chambers, and do not extend as far into the vertebral columns as those ofVenenosaurus.[16]
The vertebrae near the base of the tail are extremely useful for classifying sauropods.[12] Derived titanosaurs had vertebrae that were convex on the front and back.[12] Primitive sauropods had vertebrae that were either flat on both ends (amphiplaty) or concave on both (amphicoely).[17]Venenosaurus may have had a condition intermediate between the two.[17] The possession of amphiplatyan caudal centra with anteriorly facing neural spines is a unique identifier of this species.[18] Sometimes the form of central articulations change within a single individual's vertebral column.[19]
