Date on Master's Thesis/Doctoral Dissertation

5-2022

Document Type

Master's Thesis

Degree Name

M.S.

Department

Oral Biology

Degree Program

Oral Biology, MS

Committee Chair

Rougier, Guillermo W.

Committee Co-Chair (if applicable)

Davis, Brian M.

Committee Member

Scarfe, William C.

Committee Member

Santaella, Gustavo M.

Author's Keywords

Mammal; evolution; fossil; morphology; teeth

Abstract

Meridiolestids are a diverse and distinct clade of Cretaceous–Miocene South American dryolestoid mammals ranging in size from small shrew-sized insectivores to large dog- sized omnivores. Cronopio dentiacutus from the Cenomanian La Buitrera locality, Rio Negro Province, Argentina (Candeleros Fm.) is the oldest and best known of them, represented by skull material and associated jaws. A juvenile skull as attributed to Cronopio dentiacutus, based on tooth size and morphology, was collected from the type locality. The specimen includes the skull and both articulated lower jaws. The fossil is poorly ossified and partially flattened; CT scanning reveals most of the dentition in place and few floating teeth. The juvenile proportions, poor ossification, and absolute lack of wear suggests that the specimen is still immature and likely not weaned. The developmental sequence does not conform to known therian patterns, and it is uncertain if it is generally viable as primitive for mammals.

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