[1][2] The Santa Cruz Formation is known for its abundance of vertebrate fossils, including South American native ungulates (astrapotheres, litopterns, notoungulates),[3] as well as rodents, xenarthrans (armadillos, sloths, anteaters), and metatherians.

The environment of the Estancia La Costa Member is thought to have been relatively warm and humid, but likely became somewhat cooler and drier towards the end of the sequence.

[5] The base of the formation is defined by a marine regression event transitioning from the marine environment of the underlying Monte Léon Formation, which formed when large areas of Patagonia were submerged as a part of the Patagoniense Transgression.

I. brevifrons I. dentatum I. interruptum I. robustum I. rodens I. supernum P. australe P. praerutilum P. sp.

A. inversus E. ingens E. litoralis E. titans H. elongatus H. indifferens H. angustipalatus H. platycephalus H. ponderosus H. rectangularis P. filholi X. latirostris P. giganteus P. nanus P. pumilus P. strepens P. deleo P. lagena P. oenophorus P. robustus P. incisivus P. minus P. proximus S. tessellatum M. patagonicum M. gallegosense M. tehuelchum P. minutus P. intermedius P. lemoinei P. pascuali S. obusta A. minutissmus A. constans A. gracilis A. messor "E".