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[dinosaur] South America Cenozoic: Argyrolagus as bipedal marsupial + sparassodont Patene + Cayaoa

Ben Creisler

Some recent non-dino Cenozoic of South America papers that may be of interest to some:

MarÃa Alejandra Abello & Adriana Magdalena Candela (June 2019)
Paleobiology of Argyrolagus (Marsupialia, Argyrolagidae): an astonishing case of bipedalism among South American mammals.
Journal of Mammalian Evolution (advance online publication)
DOI: https://doi.org/10.1007/s10914-019-09470-z

Argyrolagus constitutes, both for its craniodental and postcranial anatomy, one of the most notably specialized South American Neogene metatherians. Differentiating it from any other South American mammal, bipedal jumping has been proposed for Argyrolagus, even though this hypothesis was not supported by morphofunctional studies. Here, we describe the postcranium of A. scaglai (from the Pliocene of Argentina), perform a functional analysis, and interpret it against a varied background of locomotor adaptations of extant mammals. The configuration of joints, the degree of development and location of muscular insertions were mainly analyzed, and functional indices were evaluated. This study indicates that Argyrolagus had stabilized glenohumeral and humeroulnar joints, a great development of the arm retractors, flexors-extensors of the digits, pronator, and supinator muscles, low restrictive humeroradial joint, powerful extensor muscles of the hip, knee, and ankle, good development of the iliac muscle, and restrictive hind limb joints. Joint configurations are interpreted to be optimal to resist the impacts during jumping, avoiding dislocation, compatible with digging activity. A compromise between the capacities to dig and manipulate objects is inferred. It is concluded that Argyrolagus had bipedal jumping locomotion as well as good capacity to dig, constituting an astonishing case of convergence with the small bipedal rodents and small Australian macropodids. We suggest that bipedal jumping in Miocene and Pliocene argyrolagids should not be necessarily related to a particular arid environment. Finally, we evaluate the importance of postcranial features to understand the phylogenetic relationships of Argyrolagidae in a comprehensive phylogeny of Metatheria.


Caio C. Rangel, Leonardo M. Carneiro, Lilian Paglarelli Bergqvist, Edison V. Oliveira, Francisco J. Goin & MarÃa J. Babot (2019)
Diversity, affinities and adaptations of the basal sparassodont Patene Simpson, 1935 (Mammalia, Metatheria).
Ameghiniana (advance online publication)

Sparassodonts were the main mammalian predators during most of Cenozoic in South America. The lower Eocene Itaboraà Basin/Formation includes the second oldest fossil records of this group in South America: Patene and cf. Nemolestes. Patene is by far the most abundant sparassodont from this formation, with more than 30 specimens referable to a single taxon, Patene simpsoni. Some specimens recovered from the Quebrada de Los Colorados Formation (formerly Lumbrera Formation â middle Eocene) in Northwestern Argentina have been also referred to P. simpsoni. In order to test the affinities of Patene and the taxonomy of the Argentinean specimens, we performed a review of the genus. Specimens of Patene from Northwestern Argentina show significant differences from the specimen from Brazil, including: smaller size; a larger paraconid more developed; and a smaller metaconid, entoconid and hypoconid. As a result, the specimens from the Quebrada de Los Colorados Formation are assigned to a new species, Patene coloradensis. The results of our phylogenetic analysis recover Patene as a basal sparassodont and support previous hypotheses that exclude Patene from the "Hathliacynidae". The results also supported the hypothesis that Allqokirus australis and Mayulestes ferox from the Tiupampa Basin (El Molino Formation, lower Paleocene -- Tiupampan SALMA), Bolivia, are the oldest known representatives of the Sparassodonta. The results also supported the monophyly of the Pucadelphyida with the inclusion of the Jaskhadelphyidae and closely related taxa in this group in addition to the Pucadelphyidae and Sparassodonta. The late Cretaceous North American Varalphadon was not recovered as a representative of the Sparassodonta in our phylogenetic analysis. Based on our results and the current fossil record, the Sparassodonta should be considered an endemic South American lineage.


Free pdf:

Esperanza CerdeÃoÂÂ(2018)
Updated synthesis of South American Mesotheriidae (Notoungulata) with emphasis on west-central Argentina.
Revue de PalÃobiologie 37 (2): 421-431

Doctor Claude GuÃrin dedicated many years of his research to fossil rhinoceroses, but also to some of the interesting mammals that evolved in South America. This is why I contribute to this volume in his memory with a synthesis on one of the families that are known as South American Native Ungulates. The order Notoungulata was the most diverse and abundant of these native ungulates throughout the Cenozoic, and is mainly gathered in two suborders, Toxodontia and Typotheria, which in turn include up to 11-12 families, not all presently considered as monophyletic groups. The family Mesotheriidae includes the largest-sized typotheres and is recorded from Early Oligocene to Early Pleistocene. Mesotheriids are mainly known from Argentina, but are also present in Chile, Bolivia, and Peru.
The record of Argentinean mesotheriids has increased in recent years, both from Paleogene and Neogene levels, and some emphasis is made in the new records from west-central areas such as Mendoza Province. The systematics of mesotheriids is far from being well resolved. Recent studies have evidenced a marked change in tooth morphology, size, and proportions along the ontogeny within mesotheriines, which have led to questioning some assumed diagnostic features. Research in progress on new findings from several localities in Mendoza could help elucidate some taxonomic issues, especially among Miocene taxa.


Ricardo S. De Mendoza & Claudia P. Tambussi (2019)
Cayaoa bruneti (Aves: Anseriformes) from the early Miocene of Patagonia, Argentina: new materials and revised diagnosis.
Ameghiniana Â(advance online publication)

We restudy the holotype specimen and all the alleged fossil material assigned to Cayaoa bruneti from the Early Miocene marine deposits of the Gaiman Formation, Patagonia, Argentina. Cayaoa bruneti is phylogenetically placed close to the Erismaturinae (="Oxyurinae") that gathers diver birds. It was considered a flightless foot-propelled diving duck and represents the earliest example of flight loss in Anatidae. We carried out a comparative and morphometric descriptive study of different species of anseriforms with special attention to divers, to evaluate what is the expected intraspecific size variation within anatids to make an assignment of materials with a greater degree of certainty. Our results allow us to state that one coracoid, five humeri, two carpometacarpi, twelve femora, eight tibiotarsi, and eight tarsometatarsi can be assigned to the species. Consequently, it was possible to make a deeper description and amend the original diagnosis.

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