Palaehoplophorus (also spelled, historically, Palaeohoplophorus) is an extinct genus of glyptodont. It lived from the Middle to the Late Miocene, and its fossilized remains were discovered in South America.
This animal, like all glyptodonts, had a thick carapace, composed of numerous osteoderm fused together, covering a large part of its body. The plates of its carapace bore a medium-sized, depressed central figure, surrounded by a wrinkled peripheral zone, divided by barely defined furrows and irregular tubercles. Large perforations opened in the furrows around the central figure and between the peripheral figures. The tail was protected by a series of mobile osteoderm rings, presenting a similar ornamentation, and by a terminal straight and cylindrical "tube", formed by contiguous, rounded osteoderms, separated by deep grooves with large perforations, similar to those of the carapace. The terminal and lateral osteoderms were almost identical to each other.
The genus Palaehoplophorus was first described in 1883 by Florentino Ameghino, based on fossil remains found in Argentina in Middle Miocene terrains. Several species have been attributed to the genus, such as Palaehoplophorus antiquus, P. disjunctus, P. meridionalis, P. pressulus, P. scalabrinii, from the Middle to the Late Miocene. Several of these species may be synonymous with each other.
Palaehoplophorus was identified as an archaic representative of the glyptodonts, notably due to the morphology of its caudal tube, with barely differentiated osteoderms, a characteristic generally considered primitive. The ornamentation of the osteoderms was however rather derived, which tends to confirm that this genus wasn't nested in a basal position of the group. Palaehoplophorus was a member of the tribe Hoplophorini, along with its relatives Hoplophorus and Plohophorus.
Modern cladistic analysis suggests that Palaehoplophorus is more closely related to other glyptodonts with caudal tubes like Doedicurus than to Glyptodon. Cladogram after Barasoain et al. 2022:[1]