Deep dive into Gallagher et al. (2025) paper on sauropod coloration

This week, a paper was published by Gallagher et al. (2025) taking a step towards tackling the question of what color neosauropods were by deducing the coloration of four diplodocid specimens from the Late Jurassic Morrison Formation of Montana. A handful of sauropod specimens have been found with skin impressions preserved, including the holotype of Haestasaurus becklesii, but until now there was no published investigation into the possible coloration of neosauropod sauropods.

For all purposes and intents, the sauropod specimen sample size subjected to analysis by Gallagher et al. is assigned by the authors to Diplodocus sp. even though Gallagher et al. note that ongoing research on the systematics of Morrison diplodocoids may lead to a change in the generic classification of the specimens found in the Mother's Day Quarry. Given the results of analysis of the melanosomes found in the skin impressions of the Mother's Day Quarry diplodocine specimens, the coloration extrapolated for these specimens was either unique to Diplodocus or widespread among diplodocines because figuring out the coloration of Barosaurus, Supersaurus, and Galeamopus is impossible due to a lack of specimens with skin impressions for those genera. In retrospect, discovery of apatosaurine specimens with skin impressions preserving melanosomes might tackle the question of how apatosaurine coloration compares with that of diplodocine diplodocids.

Microbodies of diverse morphology from a small section of stratum corneum from Diplodocus specimen CMC VP 20858 (after Gallagher et al. 2025)

The discussion by Gallagher et al. (2025) of the taphonomy of the scales of the juvenile Diplodocus specimens is quite breathtaking. Their explanation of why melanosome impressions are preserved in the integument of Diplodocus takes into account the nature of the siltstone in which the skin was preserved because epidermal scales are usually preserved as three-dimensional moulds, and the authors note that fossils from the Burgess Shale and two hadrosaur skins are preserved with clay minerals. The comments by Gallagher et al. about microbody positioning in dinosaur scales are quite interesting. When noting the difficulty in finding melanosome impressions in juvenile Diplodocus specimens, the authors express concerns about previous dinosaur scale studies reporting a lack of melanosome impressions or melanin chemical signatures in their specimens. Their recommendation that future studies on dinosaur scales investigate the possibility of their specimens being preserved similar to the juvenile Diplodocus specimens makes sense because Borealopelta is the only non-avian dinosaur taxon for which skin coloration is known (Brown et al. 2017).

Generally speaking, the paper by Gallagher et al. (2025) is a first step in deciphering the coloration of sauropod dinosaurs given that dino-artists have only historically guessed at sauropod coloration when creating illustrations of sauropod dinosaurs. By demonstrating that Diplodocus had varied coloration rivaling birds and mammals, it promises to shed new light on what the color of diplodocid scales was like.   

References:

Brown, C.M., Henderson, D.M., Vinther, J., Fletcher, I., Sistiaga, A., Herrera, J., and Summons, R.E., 2017. An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics. Current Biology 27 (16): 2514–2521.e3. doi:10.1016/j.cub.2017.06.071

Gallagher, T., Folkes, D., Pittman, M., Kaye, T. G., Storrs, G. W., and Schein, J., 2025. Fossilized melanosomes reveal colour patterning of a sauropod dinosaur. Royal Society Open Science. 12 (12) 251232. doi:10.1098/rsos.251232.