Venenosaurus

Venenosaurus
Temporal range: Early Cretaceous, 112 Ma
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Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Saurischia
Suborder: †Sauropodomorpha
Clade: †Neosauropoda
Clade: †Macronaria
Family: †Brachiosauridae
Genus: †Venenosaurus
Tidwell et al., 2001
Species: †V. dicrocei
Binomial name
Venenosaurus dicrocei
Tidwell et al., 2001

Venenosaurus (/vɛˌnɛnoʊˈsɔːrəs/ ve-NEN-o-SAWR-əs; Latin venenum meaning "poison" and Greek sauros meaning "lizard") was a sauropod dinosaur, named after the Poison Strip Member of the Cedar Mountain Formation in Utah, United States, where the fossils were discovered by a Denver Museum of Natural History volunteer Tony DiCroce in 1998. Venenosaurus dicrocei was first described as a new species in 2001 by Virginia Tidwell, Kenneth Carpenter, and Suzanne Meyer.[1] Venenosaurus is a relatively small (probably around 10 m (33 ft) long) titanosauriform sauropod, known from an incomplete skeleton of an adult and a juvenile. The holotype is DMNH 40932 Denver Museum of Natural History. The specimen consisted of tail vertebrae, the left scapula, right radius, left ulna, metacarpals, forefoot phalanges, right pubis, left and right ischia, metatarsals, chevrons, and ribs.

Geological and environmental context

The Venenosaurus type specimen was found in the Early Cretaceous (Aptian-Albian) Poison Strip Member of the Cedar Mountain Formation in Grand County, Utah.[2] The Denver Museum of Natural History opened a small Cedar Mountain Formation quarry in Eastern Utah.[3] This quarry has produced diverse dinosaur fossils including sauropods, theropods, and ornithopods of varying states of growth.[3] Of the sauropod remains from the quarry only one individual was fully grown.[3] Carbonate growths appear on bones in the quarry from which Venenosaurus was extracted.[2]

Anatomy

The scientists who first described V. dicrocei observed that the new species most closely resembles Cedarosaurus, while still being distinct.[1]

Limbs

The radius of Venenosaurus is more slender than the radii of Alamosaurus, Chubutisaurus, Opisthocoelicaudia, and Saltasaurus.[4] The ratio of the radius' least circumference to length produces a ratio of .33, more gracile than the radius of Camarasaurus lewisi and C. grandis. Cedarosaurus, however, has a slightly more gracile ratio of .31.[4] The team found that Brachiosaurus brancai's radius is the closest anatomical match to that of Venenosaurus.[4] The metacarpals of Venenosaurus are long and slender.[4] With the exception of the incomplete first metacarpal, all of the right metacarpals are known.[4] Metatarsal I is the shortest and most robust of the three recovered metatarsals.[5] Cedarosaurus had a more gracile ulna and radius than Venenosaurus.[6]

Pelvis

Venenosaurus shows a mixture of titanosaur and non-titanosaur ischium-to-pubis proportions.[7] Its hips most closely resemble those of Brachiosaurus.[7]

Vertebrae

The vertebrae in the middle and toward the end of the tail were short, distinguishing it from titanosaurs like Andesaurus, Malawisaurus, Aeolosaurus, Alamosaurus, and Saltasaurus.[8] The neural spines in the middle tail vertebrae are angled toward the front of the animal.[9] These vertebrae resemble those of Cedarosaurus, Aeolosaurus, and Gondwanatitan.[9] The vertebrae are located at a transitional position from anterior to posterior caudal vertebrae.[9]

Venenosaurus had unusual lateral fossae, which looked like deep depressions in the outside walls of the vertebral centra.[10] Some fossae are divided into two chambers by a ridge inside the depression.[10] In most sauropods the fossae would form pneumatic openings leading to the interior of the centrum, rather than just being a depression.[10] Less well-developed, but similar fossae are known from Cedarosaurus.[10] Fossae that similarly resemble shallow depressions are known from Saltasaurus, Alamosaurus, Aeolosaurus, Gondwanatitan, and Malawisaurus.[10] 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 of Venenosaurus.[10]

The vertebrae near the base of the tail are extremely useful for classifying sauropods.[6] Derived titanosaurs had vertebrae that were convex on the front and back.[6] Primitive sauropods had vertebrae that were either flat on both ends (amphiplaty) or concave on both (amphicoely).[11] Venenosaurus may have had a condition intermediate between the two.[11] The possession of amphiplatyan caudal centra with anteriorly facing neural spines is a unique identifier of this species.[12] Sometimes the form of central articulations change within a single individual's vertebral column.[13]

Footnotes

  1. 1 2 "Abstract," Tidwell, Carpenter, and Meyer (2001). Page 139.
  2. 1 2 "Depositional Setting," Tidwell, Carpenter, and Meyer (2001). Page 140.
  3. 1 2 3 "Introduction," Tidwell, Carpenter, and Meyer (2001). Page 140.
  4. 1 2 3 4 5 "Forelimb," Tidwell, Carpenter, and Meyer (2001). Page 148.
  5. ↑ "Pelvis," Tidwell, Carpenter, and Meyer (2001). Page 152.
  6. 1 2 3 "Discussion," Tidwell, Carpenter, and Meyer (2001). Page 157.
  7. 1 2 "Pelvis," Tidwell, Carpenter, and Meyer (2001). Page 150.
  8. ↑ "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 145.
  9. 1 2 3 "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 146.
  10. 1 2 3 4 5 6 "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 147.
  11. 1 2 "Discussion," Tidwell, Carpenter, and Meyer (2001). Page 158.
  12. ↑ "Discussion," Tidwell, Carpenter, and Meyer (2001). Page 159.
  13. ↑ "A Note on Caudal Central Articulation," Tidwell, Carpenter, and Meyer (2001). Pp. 159-160.

References

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