Tyrannosaurus rex

[johnny rex]

(05-20-2020, 08:35 PM)DinoFan83 Wrote: Here is some scaling I have done of all adult Tyrannosaurus specimens I could find data on (adult meaning 15 years or older) to get an idea of average size. This is based on femur length, so I will extrapolate femur lengths for specimens that do not preserve femurs. All bone measurements are either from Larson et al. 2008 or the Theropod Database.

Larson et al. 2008 (Tyrannosaurus Rex, the Tyrant King) has a very helpful table of Tyrannosaurus bone measurements (link). All the listed measurements for Tyrannosaurus are from adult specimens, as per the Theropod Database (Note, however, that some of the specimen measurements differ from what is given. Specifically, CM 9380's femur is 126.5 cm as per Hutchinson et al. 2011's mount scan, MOR 1125's femur is 107 cm as per Schweitzer et al. 2016, RTMP 81.6.1's femur is 115 cm as per the Theropod Database, and Sue's femur is 132.5 cm as per the Theropod Database, so I will be using those respective figures for them). I will also be including femur length figures for some specimens not listed in the table, namely Scotty (133 cm), Dynamosaurus (132 cm), and DMNH 2827 (111 cm), all as per the Theropod Database.

The average of specimens known from femora:

Adding all the measurements up results in a total femur length average of about 120.6 centimeters, out of a sample of 19 (22932/19). However, there are some specimens that do not preserve femora or have no reported femur length, and I will calculate a potential femur length for them based on other specimens.

Estimates for specimens that do not preserve femora:

The specimens whose femoral length I will be estimating based on other specimens are MOR 008, LACM 23844, AMNH 5027, BHI 4182, UCMP 118742, BHI 4960, 'Tristan', BHI 6231, and 'Trix'. What specimen I am using as a base will be noted for each.

MOR 008 has a maxilla and dentary 72 and 88 centimeters respectively, compared to the 86.1 and 101 cm maxilla and dentary in Sue. The average disparity between these is 1.169375 percent, so based on Sue's 132.5 cm femur, MOR 008 would have a 113.3 cm femur.

LACM 23844 has a 92 cm dentary vs 101 cm in Sue, which results in an approximately 120.7 cm femur.

AMNH 5027 is very similar in size to CM 9380 and their ilia are the same length. Its femur was likely around 126.5 cm, as CM 9380's was.

BHI 4182's dentary is 91 cm vs 101 cm in Sue, which is an approximately 119.4 cm femur.

UCMP 118742's maxilla is 96.4 percent the size of Sue's when averaging all measurements from the Theropod Database, which is an approximately 127.7 cm femur.

BHI 4960's ilium is 127.5 cm vs 155 cm in BHI 3033, which is approximately a 107.8 cm femur.

Tristan is stated to be 12 meters long by the Museum fur Naturkunde, vs 12.3 meters for Sue, which is a 129.4 cm femur.

BHI 6231 has a 36 cm humerus vs 39 cm in Sue, which is a 122.3 cm femur.

Trix is stated to be in between Sue and Stan in size (therefore 11.79 m), which is a 127 cm femur.

Adding these up results in a mean of about 108.8 cm, in a sample of 9 (10941/9).

Overall Average:

Adding up all known and extrapolated femur lengths and then dividing them by the sample size (22932 plus 10941, divided by 28) results in a mean femur length of about 120.5 cm. This is approximately 6 tonnes scaling down from CM 9380, which is about 7 tonnes with a 126.5 cm femur.

Therefore, based on this, the average adult Tyrannosaurus based on known specimens is about 6 tonnes. This is also coherent with Greg Paul's mass estimates in the 2010 and 2016 Princeton Field Guide to Dinosaurs.

The femur length and circumference of MOR 1125 a.k.a B-rex (the specimen where the medullary bone were discovered) are varied depending on different sources. The original source (Schweitzer and Horner) give the femur length and circumference at 107 cm and 43 cm respectively, while Larson give larger measurements which is dubious. Reply