Paleogene Pseudoglyptodont Xenarthrans from Central Chile and Argentine Patagonia

Decoupling the spread of grasslands from the evolution of grazer-type herbivores in South America

“…Third, volcanic ash deposited in tropical and temperate forests can lead to extreme tooth wear in animals (primates) feeding on dust-covered plants 32 . In a predominantly closed environment with frequent, distal ash deposition primarily affecting understory plants 33 , we suggest that feeding height or other types of niche partitioning (for example, according to plant toughness, affecting chewing effort 34 ) might lead to differential selective pressure for hypsodonty among herbivores, including marsupials 35 , rodents (post-Eocene) 36 and xenarthrans 37 . Unlike in younger strata 38 , Gran Barranca has yielded almost no cranial and post-cranial material that would allow refined reconstruction of functional morphology, and tooth wear data for members of lineages actively evolving hypsodonty in southern South America are not yet available; thus, this hypothesis remains untested.…”

Reinterpretation of a Middle Eocene Record of Tardigrada (Pilosa, Xenarthra, Mammalia) from La Meseta Formation, Seymour Island, West Antarctica

“…10, but its preservation is too poor for definitive identification. Microanatomical conditions in the teeth of Pseudoglyptodon, regarded by some authorities as a close relative of tardigradans (McKenna et al, 2006), are unknown; there are certainly no macroanatomical resemblances to the Seymour tooth.…”

“…As recently relimited by McKenna and Bell (1997) and McKenna et al (2006), Tardigrada (sloths) includes the most recent common ancestor of Bradypus and Choloepus plus all of its descendants. It is thus an avowedly crown-group construction.…”

New Paleogene Notohippids and Leontiniids (Toxodontia; Notoungulata; Mammalia) from the Early Oligocene Tinguiririca Fauna of the Andean Main Range, Central Chile

“…The Tinguirirican is currently regarded as temporally interposed between the Mustersan (late Eocene) and Deseadan (late Oligocene-early Miocene) intervals of the classical SALMA sequence, given that the Divisaderan, originally considered to precede the Tinguirirican, has recently been shown to be invalid as it represented a mixed assemblage of demonstrably older (mainly Casamayoran) and younger (Deseadan to Santacrucian) taxa (Cerdeño et al, 2008;López, 2008López, , 2010López and Manassero, 2008). Following a preliminary accounting (Wyss et al, 1994), various components of the Tinguiririca Fauna have been described in detail elsewhere, including its marsupials (Flynn and Wyss, 1999), interatheriids (Hitz et al, 2000(Hitz et al, , 2006, archaeohyracids Reguero et al, 2003), tardigrades (McKenna et al, 2006), dasypodids (Carlini et al, 2009), rodents (Bertrand et al, 2012), and notostylopids and basal toxodontians (Bradham et al, 2015). Here we build on this documentation, describing the fauna's diverse but sparsely represented notohippids and leontiniids.…”