Temporal range: Early Cretaceous, 126Ma
Tidwell et al., 1999
|Species:||† C. 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.
Cedarosaurus had a more gracile ulna and radius than its relative Venenosaurus. The ratio of the radius' least circumference to its length is .31 in Cedarosaurus. Metatarsal II is more gracile in Cedarosaurus.
The related Venenosaurus had unusual lateral fossae, which looked like deep depressions in the outside walls of the vertebral centra. Some fossae are divided into two chambers by a ridge inside the depression. In most sauropods the fossae would form pneumatic openings leading to the interior of the centrum, rather than just being a depression. Less well-developed, but similar fossae are known from Cedarosaurus itself.
In 2001 Frank Sanders, Kim Manley, and Kenneth Carpenter published a study on 115 clasts discovered in association with a Cedarosaurus specimen. These clasts were the first discovery of in situ gastroliths from the Cedar Mountain Formation. The clasts were "partially matrix supported" and there were many contacts between clasts and bones and between the clasts themselves. The clasts 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. Their high surface reflectance values are consistent with other known dinosaur gastroliths. The clasts were generally of dull coloration, suggesting that color was not a major factor for the sauropod's decision making. All but three of the Cedarosaurus gastroliths were found within a .06 m volume of space. This space was located within the gut area. No other clasts were found within the quarry, which at the time had a volume of about 11 m cubed. The set of gastroliths is believed complete due to their being discovered in a single pocket deep in the quarry. The skeletal position suggests that the skeleton came to rest on its belly.
The total mass of the gastroliths was 7 kilograms, total volume 2703 ccs and the total surface area 4410 cm2. A majority, 67 of the 115 gastroliths, were less than 10 cc in volume. Individual clasts ranges from .04 cc to 270 cc in volume. The least massive clast was .1 gram and the most was 715 grams. Most of the gastroliths tended to be small. The clasts tended to be close to spherical in shape, with the largest specimens being the most irregular. 43% were oblate spheroids, 34% spheroids, 16% prolate spheroids, and 7% ellipsoidal. The largest gastroliths contributed the most to the total surface area of the set. Since some of the most irregular gastroliths are also the largest, it is unlikely that they were ingested by accident. Cedarosaurus may have found irregular clasts to be attractive potential gastroliths or was not selective about shape. Some gastroliths were so large an irregularly shaped that they may have been difficult to swallow. The gastroliths includes chert, sandstone, siltstone, and quartzite clasts. Some of the chert clasts actually contained fossils. The sandstone clasts tended to be fragile and some broke in the process of collection. 62% were chert, 31 percent were sandstone and siltstone, 7% were quartzite.
None of the gastroliths had the "soapy" texture popularly used to distinguish gastroliths from other types of clast. The researchers dismissed using a soapy texture to identify gastroliths as "unreliable." Gastroliths tended to be universally dull, although the colors represented were varied including black, dark brown, purplish red and grey-blue. Reflectance values greater than 50% are very diagnostic for identifying gastroliths. Clasts from beaches and streams tended to have reflectance values of less than 35%. Less than ten percent of beach clasts have reflectance values lying between 50 and 80%. The most reflective gastroliths were composed of chert. Some of the gastroliths couldn't be tested for reflectance due to a confounding metallic coating, which may have been hematite. Expansion and contraction of the supporting mudstone around the inflexible clasts actually left series of parallel scratches in the coating. The metallic coating "probably originated from the iron rich mudstone" surround the fossils. The sandstone gastroliths may have been rendered fragile after deposition by loss of cement caused by the external chemical environment. If the clasts had been that fragile while the animal was alive, they probably rolled and tumbled in the digestive tract. If they were more robust, they could have served as part of a ball-mill system. The high surface area to volume ratio of the largest clasts "also supports a grinding or crushing model."
- Tidwell, et al. (1999).
- "Discussion," Tidwell, Carpenter, and Meyer (2001). Page 157.
- "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 146.
- "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 147.
- "Abstract," in Sanders et al. (2001). Pg. 166.
- "Occurrence in Cedarosaurus," in Sanders et al. (2001). Pg. 169.
- "Depositional Setting," in Sanders et al. (2001). Pg. 169.
- "Table 12.2," in Sanders et al. (2001). Pg. 171.
- "Description," in Sanders et al. (2001). Pg. 172.
- "Table 12.3," in Sanders et al. (2001). Pg. 174.
- "Description," in Sanders et al. (2001). Pg. 174.
- "Description," in Sanders et al. (2001). Pg. 176.
- "Description," in Sanders et al. (2001). Pp. 176-177.
- "Description," in Sanders et al. (2001). Pg. 177.
- "Conclusion," in Sanders et al. (2001). Pg. 177.
- Sanders, F.; Manley, K.; & Carpenter, K. 2001. Gastroliths from the Lower Cretaceous sauropod *Cedarosaurus weiskopfae*. pp. 166–180. In: Tanke, Darren; Carpenter, Ken (eds.) (2001). Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J. Currie. Indiana University Press. ISBN 0-253-33907-3.
- Tidwell, V., Carpenter, K. and Brooks, W. (1999). "New sauropod from the Lower Cretaceous of Utah, USA". Oryctos 2: 21-37
- Tidwell, V., Carpenter, K. & Meyer, S. 2001. New Titanosauriform (Sauropoda) from the Poison Strip Member of the Cedar Mountain Formation (Lower Cretaceous), Utah. In: Mesozoic Vertebrate Life. D. H. Tanke & K. Carpenter (eds.). Indiana University Press, Eds. D.H. Tanke & K. Carpenter. Indiana University Press. 139-165.