Cedarosaurus

Cedarosaurus
Temporal range: Early Cretaceous, 126 Ma
↓
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Saurischia
Suborder: †Sauropodomorpha
Clade: †Neosauropoda
Clade: †Macronaria
Family: †Brachiosauridae
Genus: †Cedarosaurus
Tidwell et al., 1999
Species: †C. weiskopfae
Binomial name
Cedarosaurus weiskopfae
Tidwell et al., 1999

Cedarosaurus (meaning "Cedar lizard" - named after the Cedar Mountain Formation, in which it was discovered) was a nasal-crested macronarian dinosaur genus from the Early Cretaceous Period (Barremian). It was a sauropod which lived in what is now Utah. It was first described by Tidwell, Carpenter and Brooks in 1999.[1]

It shows similarities to the brachiosaurid Eucamerotus from the Wessex Formation of southern England, as well as to Brachiosaurus from the Morrison Formation.

Anatomy

Cedarosaurus had a more gracile ulna and radius than its relative Venenosaurus.[2] The ratio of the radius' least circumference to its length is .31 in Cedarosaurus. Metatarsal II is more gracile in Cedarosaurus.[2]

Its middle tail vertebrae's neural spines angled anteriorly when the vertebrae are aligned.[3] These vertebrae resemble those of Gondwanatitan, Venenosaurus, and Aeolosaurus.[3]

The related Venenosaurus had unusual lateral fossae, which looked like deep depressions in the outside walls of the vertebral centra.[4] Some fossae are divided into two chambers by a ridge inside the depression.[4] In most sauropods the fossae would form pneumatic openings leading to the interior of the centrum, rather than just being a depression.[4] Less well-developed, but similar fossae are known from Cedarosaurus itself.[4]

Gastroliths

In 2001 Frank Sanders, Kim Manley, and Kenneth Carpenter published a study on 115 gastroliths discovered in association with a Cedarosaurus specimen.[5] The stones were identified as gastroliths on the basis of their tight spatial distribution, partial matrix support, and an edge-on orientation indicative of their being deposited while the carcass still had soft tissue.[5] Their high surface reflectance values are consistent with other known dinosaur gastroliths.[5] Nearly all of the Cedarosaurus gastroliths were found within a .06 m volume of space in the gut region of the skeleton.[6]

The total mass of the gastroliths themselves was 7 kilograms (15 lb).[7] Most were less than 10 millilitres (0.35 imp fl oz; 0.34 US fl oz) in volume.[8] The least massive clast was .1 grams (0.0035 oz) and the most was 715 grams (25.2 oz), with most of them being toward the smaller end of that range.[8] The clasts tended to be close to spherical in shape, although the largest specimens were also the most irregular.[8] The largest gastroliths contributed the most to the total surface area of the set.[9] Some gastroliths were so large and irregularly shaped that they may have been difficult to swallow.[9] The gastroliths were mostly composed of chert, with some sandstone, siltstone, and quartzite clasts also included.[10] Some of the chert clasts actually contained fossils.[10]

Since some of the most irregular gastroliths are also the largest, it is unlikely that they were ingested by accident.[9] Cedarosaurus may have found irregular clasts to be attractive potential gastroliths or was not selective about shape.[9] The clasts were generally of dull coloration, suggesting that color was not a major factor for the sauropod's decision making.[5] The high surface area to volume ratio of the largest clasts suggests that the gastroliths may have broken down ingested plant material by grinding or crushing it[11] The sandstone clasts tended to be fragile and some broke in the process of collection.[10] The sandstone gastroliths may have been rendered fragile after deposition by loss of cement caused by the external chemical environment.[12] If the clasts had been that fragile while the animal was alive, they probably rolled and tumbled in the digestive tract.[11] If they were more robust, they could have served as part of a ball-mill system.[11]

Footnotes

  1. ↑ Tidwell, et al. (1999).
  2. 1 2 "Discussion," Tidwell, Carpenter, and Meyer (2001). Page 157.
  3. 1 2 "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 146.
  4. 1 2 3 4 "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 147.
  5. 1 2 3 4 "Abstract," in Sanders et al. (2001). Pg. 166.
  6. ↑ "Occurrence in Cedarosaurus," in Sanders et al. (2001). Pg. 169.
  7. ↑ "Table 12.2," in Sanders et al. (2001). Pg. 171.
  8. 1 2 3 "Description," in Sanders et al. (2001). Pg. 172.
  9. 1 2 3 4 "Description," in Sanders et al. (2001). Pg. 174.
  10. 1 2 3 "Description," in Sanders et al. (2001). Pg. 176.
  11. 1 2 3 "Description," in Sanders et al. (2001). Pg. 177.
  12. ↑ "Conclusion," in Sanders et al. (2001). Pg. 177.

References

This article is issued from Wikipedia - version of the 7/5/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.