Yes, the element iron
is incorporated into the teeth of the multituberculate, Barpatodon (Fig. 1, Rãdulescu and Samson 1986; Smith and Codrea 2015), and other members of the gnawing clade, Glires to make them even stronger than ordinary enamel. That’s what gives those teeth that rusty appearance.
Figure 1. Barpatodon diagram from Smith and Codrea 2015 colorized here.
Barbatodon transylvanicus (Rãdulescu and Samson 1986; Late Cretaceous) is a small multituberculate preserving iron in its incisors as in several living rodents. Originally considered close to Taeniolabis, here it nests with Catopsbaatar. The premolars have been molarized. The ‘sliding jaw joint’ does not slide much.
Figure 2. Catopsbaatar greatly enlarged.
References
Rãdulescu R and Samson P 1986. Précisions sur les affinités des Multituberculés du Crétacé supérieur de Roumaine. C R Acad Sci II: Mec-Phys, Chim, Sci Terre, Sci Univ 303p, p. 1825-1830.
Smith T and Codrea V 2015. Red Iron-Pigmented Tooth Enamel in a Multituberculate Mammal from the Late Cretaceous Transylvanian “Hateg Island”. PLoS ONE 10(7): e0132550. https://doi.org/10.1371/journal.pone.0132550
The Pterosaur Heresies 