Late Miocene Palaehoplophorini (Xenarthra, Glyptodontidae) from the Puerto Madryn Formation (Chubut, Argentina): diversity and biochronological implications

BARASOAIN, D.; DOZO, M.T.; GONZÁLEZ RUIZ, L.; TOMASSINI, R.; ZURITA, A.

Congreso; 4th Virtual Paleontological Congress; 2023

Paleontological Virtual Congress

The Palaehoplophorini are a poorly known tribe of glyptodonts that appeared during the Middle Miocene of Patagonia (Argentina) after a diversity decline of the Propalaehoplophorinae. Their diversity was low with respect to other glyptodont groups and includes just two well-characterized taxa from Patagonia, Palaehoplophorus meridionalis and Palaehoplophoroides rothi (Middle Miocene, ca. 12 Ma). Putative Late Miocene Palaehoplophorini, such as Palaehoplophorus antiquus and Aspidocalyptus castroi, are defined from very fragmentary materials, without relevant diagnostic characters at tribe and specific level. Additionally, contrary to previous studies, a recent revision of Late Miocene (ca. 9 Ma, Chasicoan Stage/Age) glyptodonts from central Argentina confirmed the absence of representatives of this tribe. Here, we describe several Palaehoplophorini remains coming from the upper levels of the Puerto Madryn Formation in Península Valdés (Chubut Province, Argentina) assigned to the Late Miocene (ca. 9.4 Ma). Materials include carapace osteoderms, caudal rings and tube fragments, and an associated right femur (PA-09-11/10- 11/11-11/12-11/13-01/MPEF-PV2531/2532/AC12FS/AC5FS1-4), which are assigned to Palaehoplophorini for having osteoderms bearing a double row of peripheral figures of irregular outline (inner row figures being smaller than the outer ones) and conspicuous dorsal foramina surrounding the central figure. The femur, one-third larger than that of Kelenkura castroi from the Chasicoan Stage/Age, implies a body mass exceeding 160 kg. These materials confirm the presence of Palaehoplophorini during the Late Miocene, at least in Patagonia. Further comparisons with other putative Palaehoplophorini remains from outside Patagonia (i.e., Ituzaingó Formation, Entre Ríos, Argentina) will show whether or not it is a tribe restricted to Patagonia.