Tyrannosaurus Growth Exhibit at the Natural History Museum of Los Angeles

Sculpting a caudal vertebra.

The Natural History Museum of Los Angeles is approximately a year away from unveiling Dinosaur Mysteries, a modern exhibition with new content, discoveries, and nearly 300 Mesozoic specimens. The exhibit will include many new and some refurbished fossil mounts which a team of paleontological preparators at the NHMLA have diligently and skillfully cleaned, conserved, and restored for museum exhibition, and scientific study. This is a rare opportunity for anyone working in a museum to take part of especially if it means working on the King of all dinosaurs, Tyrannosaurus rex.

One of the more notable specimens to be exhibited is Thomas, a sub adult Tyrannosaurus rex, which died 66 million years ago in Montana. The center piece of the exhibit is a tableau featuring three rexes of varied ages to illustrate how these animals grew, and possibly suggest a pack or family unit which might have cooperated in hunting prey, or securing carrion.  The three mounts will appear to be investigating an Edmontosaurus carcass, (a Hadrosaur or duck billed dinosaur), a likely food source during the Cretaceous.

Thomas is estimated to be an adolescent perhaps 13 to 16 years old when it died. On the other extreme, the baby is thought to be about 2 year old when it died, making it very fleet footed but quite vulnerable to predation. The intermediate of the two is a juvenile animal measuring about 20 feet long but would have less than half the mass of a full adult.

The difficulty of reconstructing a baby dinosaur lies directly with the sparseness of quality specimens in the fossil record. Although research suggests that there are several anatomical, and proportional differences between a baby and adult dinosaurs, there is no known complete baby Tyrannosaurus rex to base this reconstruction on, so this is only a speculation, but a very educated guess as to what the animal might have looked like.

The baby T. rex specimen known as LACM 2841, is very incomplete, and no post-cranial elements were ever found with the remains. This priceless fragment was originally collected by Harley Garbani in the 1960's, and is estimated to have been about 60 lbs and 10 feet long. In order to extrapolate information from the fossil record accurately the artist worked closely with the museum's Dinosaur Institute Director Luis Chiappe, a Vertebrate Paleontologist specializing in theropod and avian evolution.

LACM 2841  painted cast of the maxillary area of the skull.

Articulated left scapula and arm.

One significant trait that seems to be common in dinosaurs and many other animals living and extinct, is a gracile bone structure having softer processes, and trochanters with larger fenestra, particularly in regards to the orbits. For a young T. rex, the bones would be much lighter, and unfused as seen in sub adult animals today including humans. This is also evident in the specimen Thomas, especially in the skull which was completely disarticulated when it was being collected between 2004 to 2004. It was noted that on several vertebrae of Thomas that some of the centrums were dislocated from their corresponding neural spines at least partially if not altogether.


To reconstruct the baby T. rex Doyle used adult skeletal reference from several specimens and determined how much needed to change to suite the anatomy for a baby dinosaur. Using photo manipulation software and some digital painting, the artist was able to create an illustration for what he would use as a starting point when sculpting began. Doyle was charged with reconstructing all the post cranial elements, while Phil Fraley Productions would concentrate on completing the skull and metal armature that holds the whole specimen in position.

Doyle working on the right tibia, amongst his carvings.

The post cranial sculpt was executed in one pass (without molds in most cases) in dense carving foam, sealed in polyurethane resin and detailed with pnuematic tools and epoxy for finalizing a texture, and structural reinforcement. The process took about 4 or 5 months, which included a research and development period, a pre-production phase in which the 2 dimensional rendering was produced for reference and printed to scale, and lastly when the bones were sculpted one by one and then shipped to Phil Fraley Production for armature building. 

The baby T. rex in its cautious approach towards the Hadrosaur carcass to 
be displayed center to all three mounts.

While Phil Fraley Productions continued their work on mounting and painting the baby rex, Doyle moved on to his next project: a sculpted reconstruction of a Juvenile Edmontosaurus skull, based on another specimen collected by Harley Garbani.  This sculpt will be attached to the very complete skeleton which was beautifully preserved in the round and well articulated.

 

The Tyrannosaur trio, in the soon to be Dinosaur Hall at the Natural History Museum of Los Angeles.  The largest mount is Thomas, the smallest the reconstructed baby, and the medium sized rex to the left is a juvenile previously classified as Albertosaurus, and Nanotyrannus, but now believed to be a 6-7 year old Tryannosaurus rex.