The debate over whether theropod dinosaurs were feathered, scaly or perhaps a combination of both continues. In contrast, the integumentary covering of sauropod dinosaurs has largely remained uncertain due to the very limited fossil evidence. However, at one remarkable location in Montana, patches of fossilised Diplodocus skin have been preserved and an analysis indicates that these long-necked dinosaurs were most likely covered in scales, but surprisingly their skin scales were not uniform. A range of scale shapes are indicated, all of them relatively small, but ovoid, rectangular, polygonal, domed scales and irregular (globular) scales have been identified.

A Research Paper

In a scientific paper published in the on-line, open-access journal PeerJ (April 2021), written by Tess Gallagher (currently a Masters student at Bristol University), in collaboration with colleagues from, what was known at the time as the Bighorn Basin Paleontological Institute, descriptions were provided of some patches of skin associated with juvenile Diplodocus fossils.

The fossil material comes from a single location known as the Mother’s Day Quarry, located in the Bighorn Basin, (Montana). The site was originally discovered in the 1990s and the Upper Jurassic deposits have yielded over two thousand Diplodocus fossil bones. Surprisingly, given the concentration of sauropod material found, very few other fossils have been discovered in this quarry. To date, some theropod teeth (allosaurid) are known plus one potential theropod footprint, preserved in association with the skin and a single invertebrate specimen.

It has been suggested that a herd of young Diplodocus dinosaurs died from lack of water at a dried up watering hole. Their bodies remained on the surface for some time and became desiccated. A flash flood occurred and swept the corpses downstream and these accumulated bodies were rapidly buried.

The dinosaur skin, having been bleached and dried out on the surface, once rapidly buried has an increased chance of becoming fossilised. Recently published research (October 2022), from Drumheller et al suggests that “mummified” skin might be more common in the fossil record than previously thought.

To read Everything Dinosaur’s blog post about this phenomenon: Dinosaur Mummies an Alternative Fossil Pathway.

Fossilised Diplodocus Skin

Although only a small portion of skin has been identified to date and the scientists remain uncertain as to which part of the body the skin patches covered, analysis has revealed a remarkably diverse quantity of scales. The team conclude that considering how diverse the scale shapes are in such a small area of skin, it is possible that these distinct scale shapes may represent a transition on the body from one region to another, perhaps from the abdomen to the dorsal side, or abdomen to the shoulder.

At least six different types of Diplodocus scale have been identified, suggesting that the skin of these sauropod dinosaurs was complex. In addition, a further study presented at the recent annual meeting of the Society of Vertebrate Paleontology in Canada, provided a fresh perspective on the specialised skin of these sauropods.

Analysis of the scales using a high-powered microscope revealed that they had unusually large pores. It has been proposed that these large pores helped increase the surface area of this huge dinosaur. The greater the surface area of the skin the more assistance it would have been in helping to keep Diplodocus cool. Elephants have wrinkled skin, this increases the skin’s surface area which helps to minimise the impact of the “square-cube law” in relation to overheating.

“Square-cube” Law

The larger the volume of an animal, the smaller the overall surface area of the skin in contact with the air and this makes dissipating heat difficult for large animals. Just as elephants help to resolve issues with overheating with their wrinkled skin, the large pores associated with the Diplodocus skin had a similar effect.

The scientific paper: “Evidence of integumentary scale diversity in the late Jurassic Sauropod Diplodocus sp. from the Mother’s Day Quarry, Montana” by Tess Gallagher, Jason Poole and Jason P. Schein published in PeerJ.

A recent study published in the academic journal “Scientific Reports” refutes the idea that some long-necked herbivores had supersonic sauropod tails. The controversial idea that some dinosaurs could lash their tails like a whip creating a supersonic crack as the tail travelled faster than the speed of sound has been refuted in newly published research. Instead, the researchers suggest that the tail of diplodocids such as Apatosaurus, Brontosaurus and Diplodocus could still play a role in defence, producing a painful blow to deter an attacker. It is also suggested that these long, whip-like tails could have been used in intraspecific combat.

Picture credit: Everything Dinosaur

Supersonic Sauropod Tails

A sauropod clade, the Flagellicaudata are characterised by their extremely long tails. This clade includes the Diplodocidae family and the closely related Dicraeosauridae. Although complete fossil sauropod tails are extremely rare, palaeontologists have a good idea of the anatomy of a typical diplodocid tail. It consisted of approximately eighty caudal vertebrae, that gradually decrease in size and morphological complexity towards the tail tip. There are approximately ten larger posterior vertebrae, followed by forty or so intermediate bones with finally around thirty progressively smaller rod-like caudal vertebrae.

Earlier studies had suggested that the tail could be whipped, and the tip would travel so fast (in excess of 500 metres per second), this action would break the sound barrier and produce a loud sound. This speedy tail would cause a significant injury should it come into contact with another dinosaur.

However, this new study used three-dimensional models and computer analysis to assess the stress on the bones, ligaments and soft tissues. They concluded that the maximum tip velocity generated would be around thirty metres a second, nowhere near the 330 metres per second required to break the sound barrier.

The picture (above) shows the recently introduced Eofauna Scientific Research Diplodocus carnegii replica. When shown in lateral view, the extremely long tail can be seen.

To view the range of models and figures in the Eofauna series: Eofauna Scientific Research Models.

An Effective Weapon

Whilst the researchers conclude that the effect of friction on the musculature and aerodynamic drag would prevent the tail tip from reaching a speed capable of breaking the sound barrier, the pressure applied by the terminal section would not be enough to break bones or lacerate dinosaur skin, but it could still deliver a painful blow.

In summary, the scientists suggest that sauropod tail use remains speculative, these tails could have been used in intraspecific combat, or perhaps as a weapon against predators. Similarly, the use of the tail as a tactile element to retain herd cohesion is equally plausible.

The scientific paper: “Multibody analysis and soft tissue strength refute supersonic dinosaur tail” by Simone Conti, Emanuel Tschopp, Octávio Mateus, Andrea Zanoni, Pierangelo Masarati and Giuseppe Sala published in Scientific Reports.