Natalia Zimicz

• Dr
• Researcher at National University of Salta

Ceratophryid frogs inhabit the lowlands of South America and exhibit greater diversity in the semiarid Gran Chaco. The presence of Ceratophryidae dates back to the late Miocene on the eastern slopes of the Andes in Argentina. Herein, we describe the remains of Ceratophrys from late Miocene of Palo Pintado Formation (Salta, Argentina). Fragmentary b...

We report herein a new genus and species of Pyrotheria, Berracotherium koimeterion, from the Quebrada de Los Colorados Formation (middle Eocene-early Oligocene), Salta Province (Argentina). Up to this contribution, pyrotheres had only been known from northwestern Argentina by a single fragmentary tusk referred to Propyrotherium from the Geste Forma...

New remain of a SANU from the lower levels of the Lumbrera Formation is described. It consists of a left dentary fragment with a m3 preserving a partially broken trigonid and a complete talonid. Kyraodus churcalensis gen. et. sp nov. is characterised by the following combination of features: brachydont and bunodont molar; talonid larger than trigon...

Recently, the basal beds of the lower section of the Lumbrera Formation have been referred to the early Eocene (Ypresian) based on the identification of a succession of hyperthermal events globally dated between 52 and 55 Ma. Nevertheless, this section have also been referred to the middle Eocene (Lutetian) based on the ‘evolutionary stage’ of its...

In the Eocene deposits of Northwestern Argentina, the order Cingulata was recognized in the sedimentary levels of the upper and lower sections of the Lumbrera (Salta Province), Geste (Catamarca and Salta provinces), Quebrada de Los Colorados (Salta Province), and Casa Grande (Jujuy Province) formations. The traditional biochronological scheme assoc...

In the last few years, the Quebrada de Los Colorados Formation has become an important middle Eocene fossiliferous unit in Northwestern Argentina. In this unit, the South American native ungulates were until now only represented by the order Notoungulata, including one family of Typotheria and three of Toxodontia. In this contribution, we present a...

In the last few years, the Quebrada de Los Colorados Formation has become an important middle Eocene fossiliferous unit in Northwestern Argentina. In this unit, the South American native ungulates were until now only represented by the order Notoungulata, including one family of Typotheria and three of Toxodontia. In this contribution, we present a...

With two recognized species, the extinct (late Eocene) Groeberia is periodically at the centre of systematic disputes. On the basis of its best-preserved specimen, we describe in detail the dental and functional morphology of the masticatory apparatus of Groeberia minoprioi. A review of its dental anatomy indicates that Groeberia has a tribosphenic...

The Quebrada de Los Colorados Formation (Los Cardones National Park, Salta Province, north-western Argentina), is an Eocene–Oligocene unit well represented in the Calchaqu�ı Valley area. Here we describe a new metatherian association recorded from the base of this formation, inferred as middle Eocene. Represented taxa are: Sparassodonta, family ind...

We summarize the configuration of plates, geographical barriers, and possible dispersal events during the Late Cretaceous–Cenozoic between North and South America, the Caribbean, Antarctica, and Australia. The arrival of metatherians in South America was a Late Cretaceous event, and probably a Maastrichtian one. There are few doubts that the first...

The early Paleocene diversity of metatherians in Tiupampan faunas of South America and the pre-Tiupampan Paleocene polydolopimorphian Cocatherium speak in favor of an earliest Paleocene or Late Cretaceous dispersal of metatherians from North America. No Late Cretaceous metatherian or eutherian mammals have been recovered to date in South America, b...

South American living metatherians are relatively inconspicuous and comprise ca. 10 % of the region’s mammal species richness. Most of them are small-sized (<150 g), with long tails and grasping hands and feet, and resemble one another in their general appearance. Individuals are solitary, nocturnal or crepuscular, and most of them are arboreal or...

With less than 3 g of estimated body mass, the early Eocene Minusculodelphis minimus Paula Couto (Mammalia, Metatheria, Jaskhadelphyidae) is one of the smallest mammals, living or extinct. It has alternatively been regarded as a didelphid or a derorhynchid Bameridelphian,^ or even as an eometatherian marsupial. Here, we describe a new species of Mi...

With more than 100 species, living South American marsupials (Mammalia, Metatheria) give only a glimpse of the much higher taxonomic and ecological diversity acquired by metatherians throughout the Cenozoic Era. The term Metatheria designs a taxon within Mammalia that includes not only Marsupialia but also all therian mammals more related to Marsup...

Diversity, dietary, and body mass analyses suggest that the early Eocene represents the major radiation event in South America metatherian evolutionary history. During this period, representatives of all orders typical of the Paleogene reached their greatest diversity (i.e., “basal ameridelphians”; Polydolopimorphia Polydolopiformes, and Bonaparthe...

The Metatheria include not only marsupials but all therians more related to Marsupialia than to the Eutheria. Marsupialia is considered as a metatherian crown group including all extant marsupials, their common ancestor and all of their descendants. “Ameridelphia” is not a natural group. Australidelphia includes the Microbiotheria and all Australas...

In order to understand the timing of metatherian radiations, adaptations, and extinctions, it is important to review the variety of strongly interrelated contexts that defined them. (1) During the Cenozoic Era, global climates shifted from Greenhouse to Icehouse conditions; this major change was quite obvious by the Eocene–Oligocene boundary (ca. 3...

This book summarizes major aspects of the evolution of South American metatherians, including their epistemologic, phylogenetic, biogeographic, faunal, tectonic, paleoclimatic, and metabolic contexts. A brief overview of the evolution of each major South American lineage ("Ameridelphia", Sparassodonta, Didelphimorphia, Paucituberculata, Microbiothe...

An almost complete skull of Australohyaena antiqua (Ameghino), from the Late Oligocene (Deseadan SALMA) of Cabeza Blanca, Chubut Province, Argentina is described and analysed. For more than a century, this species was represented by isolated teeth. The genus Australohyaena gen. nov. is proposed based on a phylogenetic reconstruction that demonstrat...

An appraisal of Paleogene floral and land mammal faunal dynamics in South America suggests that both biotic elements responded at rate and extent generally comparable to that portrayed by the global climate pattern of the interval. A major difference in the South American record is the initial as well as subsequent much greater diversity of both Ne...

The ecological interaction between small and medium sized South American metatherian carnivores, from the Miocene to Recent, has been analyzed with the objective to understand the ecological interactions between the Hathliacynidae (Sparassodonta) and some Didelphoidea (Didelphimorphia). The species richness through time for these two groups, along...

BONAPARTHERIIFORMES). The wear pattern, occlusal movement, body mass, and diversity of Bonapartherioidea families are analyzed. Hypothesis for the dietary habits and possible extinction causes are developed. Bonaparteroids are divided into three groups according to the development of Phase II in the chewing cycle. Facet 5 is not developed in Prepid...

South America was isolated from other continents during most of the Cenozoic, developing a singular mammalian fauna. In contrast to North America, Europe, Asia, and Africa, up to the late Neogene, the carnivore adaptive zone in South America was populated by crocodiles (Sebecidae), large snakes (Madtsoiidae), large birds (Phorusrhacidae), and metat...

WEAR PATTERN AND OCCLUSION IN THE MASTICATORY SYSTEM OF EXTINCT ARGYROLAGOIDEA (MARSUPIALIA, POLYDOLOPIMORPHIA, BONAPARTHERIIFORMES). The Argyrolagoidea (Mammalia, Marsupialia, Polydolopimorphia, Bonapartheriiformes) display a pattern of cusp contact that is quite different from any other group of South American metatherians during dental occlusion...

WEAR PATTERN AND OCCLUSION IN THE MASTICATORY SYSTEM OF EXTINCT ARGYROLAGOIDEA (MARSUPIALIA, POLYDOLOPIMORPHIA, BONAPARTHERIIFORMES). The Argyrolagoidea (Mammalia, Marsupialia, Polydolopimorphia, Bonapartheriiformes) display a pattern of cusp contact that is quite different from any other group of South American metatherians during dental occlusion...

We describe Thylophorops lorenzinii sp. nov. (Marsupialia, Didelphidae), the largest known didelphid opossum, living or extinct. Its type specimen comes from Late Pliocene levels at Punta San Andrés, southeastern Buenos Aires Province, Argentina. With an estimated body mass between 4.8 and 7.4 kg, it obviously surpasses that of the (up to now) larg...

We describe Thylophorops lorenzinii sp. nov. (Marsupialia, Didelphidae), the largest known didelphid opossum, living or extinct. Its type specimen comes from Late Pliocene levels at Punta San Andrés, southeastern Buenos Aires Province, Argentina. With an estimated body mass between 4.8 and 7.4 kg, it obviously surpasses that of the (up to now) larg...

FIGURE 2: Thylophorops lorenzinii sp. nov. MLP 08 - III- 10 - 1 (Holotype); detail of the erupting m 3 in lingual (A), and occlusal-lingual views (B). Scale: 2 mm.

FIGURE 4: Lower left molars of Thylophorops chapalmalensis (left, detail of specimen MPH 064), T. lorenzinii sp. nov. (centre, detail of the type specimen), and T. perplanus (right, detail of specimen MLP 97 - XI- 15 - 1). Because of the erupting stage of the m 3 of T. lorenzinii in the type specimen, the anterobasal cingulum is not visible. Scale:...

FIGURE 5: Thylophorops chapalmalensis Ameghino. A – C, detail of the rostrum and medial portion of the skull of an adult individual (MLP 64 - XI- 12 - 1) in dorsal (A), lateral (B), and ventral (C) views; D – E, detail of both mandibles of a juvenile specimen (MPH 064; D, right mandible in lingual view; E, left mandible in lingual view). In both ma...

FIGURE 1: Thylophorops lorenzinii sp. nov. MLP 08 - III- 10 - 1 (Holotype); (A), labial view of the anterior part of the skull and dentary; (B) occlusal view of the dentary; (C) lingual view of the dentary. Scale: 10 mm.

FIGURE 3: Thylophorops lorenzinii sp. nov. MLP 08 - III- 10 - 1 (Holotype); schematic drawing of the m 3 showing the cusp homologies and measurements. Abbreviations: End., entoconid; Hyd., hypoconid; Hyld., hypoconulid; Med., metaconid; Pad., paraconid; Prod., protoconid. Scale: 2 mm.

FIGURE 6: Thylophorops perplanus (Ameghino). MLP 87 - XI- 15 - 1, a juvenile specimen preserving a partial skull (A, dorsal; B, lateral, and C, ventral views) and fragments of both mandibles (D, left mandible in labial view; E, right mandible in labial view). Scale: 10 mm.

FIGURE 7: Regression plots showing the relationships between mean body mass and molar size (length and area). The red circle indicates the position of T. lorenzinii. See Table 1 for abbreviations.

We describe and comment on an isolated upper molar belonging to Woodburnodon casei gen. et sp. nov. (Mammalia, Marsupialia, Microbiotheria, Woodburnodontidae fam. nov.), from the Eocene of the La Meseta Fm (TELM 5 or Cucullaea I Member), Marambio (Seymour) Island, Antarctic Peninsula. With a body mass estimated between 900 to 1,300 g (depending on...