Peter the T. rex Scientific Report

Systematic Paleontology

THEROPODA Marsh, 1881
TETANURAE Gauthier, 1986
Tyrannosaurus rex Osborn, 1905

MATERIAL: The specimen was collected in Niobrara County, Wyoming, USA in the Lance Formation (Maastrichtian).

DESCRIPTION: The bones have well-preserved periosteal surfaces, are black in color from permineralization, preserving osteological details such as muscle scars and trace fossils on many of the bones. There is crushing, breakage, and lesions or tooth markings on some elements. Bony elements from the pelvic region were recovered, including both ilia, both ischia and both pubic shafts. The hindlimb bones found comprise both femora; the right one is nearly complete while the left is missing both proximal and distal ends of the bone. There is a nearly complete right tibia, and a mid-shaft section of the left tibia; there are both fibulae, one with the proximal end, the other a section of the shaft. Also collected was the right astragalas and several metatarsal. Cervical, dorsal, sacral and caudal vertebrae are represented. The bone density, or bulk, of this specimen represents approximately 47% of a Tyrannosaurus rex (See Appendix for a list of osteological elements). Elements are near the size range of other adult T. rex specimens, indicating that ‘Peter’ is close to adult size.

DIAGNOSIS: The specimen is referred to Tyrannosaurus rex based on the following characters: femoral, tibia, ilium with a vertical lateral ridge and metatarsal IV (plus see new characters described by Loewen et al., 2013). This referral is also confirmed by size comparison to adult T. rex.



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