English: Modes of baleen preservation. Examples of baleen preservation in mysticete skeletons from various localities and horizons of the Pisco Formation. A, B) Field photograph (A) and corresponding line drawing (B) of the partial skull and mandible of CCM1, skeleton of Balaenopteroidea indet. from P1 diatomaceous silts exposed at Cerro Colorado, preserved in dorsal disposition and within a carbonate concretion (note that the figured specimen is part of a rolled boulder). The right baleen rack is preserved between the vomer and the right mandible. C, D) Field photograph (C) and corresponding line drawing (D) of the right baleen rack of CBA3, skeleton of Piscobalaena nana from P2 diatomaceous silts exposed at Cerro Ballena, preserved in ventral disposition in absence of any external concretion entombing the bones. E) Close-up of the preserved baleen of CLB1, skeleton of Balaenopteridae indet. from P2 sands exposed at Cerro la Bruja, preserved in ventral disposition and within a carbonate concretion. The right baleen rack is preserved between the right maxilla and mandible. F, G) Field photograph (F) and corresponding line drawing (G) of the right baleen rack of CCM113, skeleton of Cetotheriidae indet. from P1 silts exposed at Cerro Colorado, preserved in ventral disposition and within a carbonate concretion. H, I, J) Field photographs (H, J) and corresponding line drawing (G) of CBN1, skeleton of Mysticeti indet. from P2 diatomites exposed at Cerro Blanco North, preserved in ventral disposition in absence of any external concretion entombing the bones. Panel A after Gioncada et al. 2016.