Date on Master's Thesis/Doctoral Dissertation


Document Type

Master's Thesis

Degree Name



Anatomical Sciences and Neurobiology

Degree Program

Anatomical Sciences and Neurobiology, MS

Committee Chair

Rougier, Guillermo W.

Committee Co-Chair (if applicable)

Davis, Brian M.

Committee Member

Davis, Brian M.

Committee Member

Hoffmann, Simone

Committee Member

Santaella, Gustavo

Author's Keywords

mammalian evolution; comparative morphology; dryolestoids; Mesozoic mammals; Patagonia; Argentina


Dryolestoids are extinct cladotherians mammals from the Jurassic and Cretaceous periods. I describe a collection of dryolestoid specimens from the Late Cretaceous localities of Cerro Tortuga (Allen Formation), Anfiteatro 1, and Shining (both La Colonia Formation) from Patagonia, Argentina. Using comparative morphology, I identify a new species of meridiolestidan dryolestoid based on eleven specimens across both formations. The new species’ recovery from La Colonia Formation represents the first dryolestoid connection between the two approximately contemporaneous formations. The species’ morphology may represent an ecological shift within Meridiolestida from insectivory to herbivory, showing a transition in characters between the plesiomorphic sharp-toothed meridiolestidans and the more derived and bunodont mesungulatoids. Other specimens from Allen Formation are referred to previously described taxa, namely Mesungulatum and Groebertherium. New material fills in unknown positions in meridiolestid dentitions and suggests that genus Groebertherium—previously regarded as a dryolestid taxon—is in fact closer to Meridiolestida.