Here are some photos of casts of skin impressions from the Triceratops “Lane” I took at the Black Hills Institute in June 2018. Lane is a mostly complete skeleton of T. horridus (formerly BHI 6273, now at the Houston Museum of Natural Science) with extensive skin preservation rivaling the famous hadrosaur mummies.
These impressions remain unpublished to date and have only been presented in an SVP abstract (Larson et al. 2007). [see addendum]
The first photo above is of an upright display of skin from the sacrum and base of the tail. The next two photos show another cast of the same area lying on the ground, with a skin patch removed to show the underlying left ilium. These casts have the impressions in the original positions in which they were discovered. All of the scales are large, interlocking polygons, with a few have them having distinct nipple-like projections.
The two photos below are closeups of one of the “nipple” scales on the tail base. Some paleoartists have incorrectly depicted them as having large spines or bristles (see chart at bottom), but in reality they only have small nubbins. Additionally, they are distributed randomly and are not arranged in even rows. Hopefully these photos will clear up the misconceptions about their appearance.
Bell et al. (2022) briefly described the skin of Lane. They revealed that its current specimen number is HMNS PV.1506. They agreed that it is implausible for spines or bristles to have emerged from the feature scales.
“Unlike the truncated-cone or conical feature scales of Psittacosaurus and other dinosaurs, such as the abelisaurid Carnotaurus, the nipple-like structure of Triceratops, which corresponds to an elevated volcano-like prominence (~1‒3 cm in height), occupies only half of the feature scale surface, the rest of the feature scale being flat. In all of these taxa (Psittacosaurus, Carnotaurus, Triceratops), it is unlikely that the feature scale bore a spine or a “bristle”-like structure — similar to those seen on the tail of Psittacosaurus — although bristle-like projections are present on some scales in the early-branching neornithischian Kulindadromeus.”
Bell et al. also noted the lack of a pattern in the feature scales.
“The polygonal feature scales of Triceratops also do not seem to form any particular pattern but, unlike Chasmosaurus, they are more regularly spaced (~15‒20 cm) and less variable in size.”
- Bell, P.R., Hendrickx, C., Pittman, M., & Kaye, T.G. (2022). The exquisitely preserved integument of Psittacosaurus and the scaly skin of ceratopsian dinosaurs. Communications Biology, 5, Article 809. https://doi.org/10.1038/s42003-022-03749-3
- Larson, P., Larson, M., Ott, C., & Bakker, R. (2007). Skinning a Triceratops. Journal of Vertebrate Paleontology, 27(3), 104A.