Paleogene Squamates from the Northern neotropics: Ecological Implications and Biogeographic Histories. (original) (raw)

A 60-million-year Cenozoic history of western Amazonian ecosystems in Contamana, eastern Peru

We provide a synopsis of ~ 60 million years of life history in Neotropical lowlands, based on a comprehensive sur- vey of the Cenozoic deposits along the Quebrada Cachiyacu near Contamana in Peruvian Amazonia. The 34 fossil- bearing localities identified have yielded a diversity of fossil remains, including vertebrates, mollusks, arthropods, plant fossils, and microorganisms, ranging from the early Paleocene to the late Miocene–?Pliocene (N20 succes- sive levels). This Cenozoic series includes the base of the Huchpayacu Formation (Fm.; early Paleocene; lacus- trine/fluvial environments; charophyte-dominated assemblage), the Pozo Fm. (middle + ?late Eocene; marine then freshwater environments; most diversified biomes), and complete sections for the Chambira Fm. (late Oligocene–late early Miocene; freshwater environments; vertebrate-dominated faunas), the Pebas Fm. (late early to early late Miocene; freshwater environments with an increasing marine influence; excellent fossil re- cord), and Ipururo Fm. (late Miocene–?Pliocene; fully fluvial environments; virtually no fossils preserved). At least 485 fossil species are recognized in the Contamana area (~250 ‘plants’, ~212 animals, and 23 foraminifera). Based on taxonomic lists from each stratigraphic interval, high-level taxonomic diversity remained fairly constant throughout the middle Eocene–Miocene interval (8-12 classes), ordinal diversity fluctuated to a greater degree, and family/species diversity generally declined, with a drastic drop in the early Miocene. The Paleocene–?Pliocene fossil assemblages from Contamana attest at least to four biogeographic histories inherited from (i) Mesozoic Gondwanan times, (ii) the Panamerican realm prior to (iii) the time of South America’s Cenozoic “splendid isolation”, and (iv) Neotropical ecosystems in the Americas. No direct evidence of any North American terrestrial immigrant has yet been recognized in the Miocene record at Contamana.

The first Late Eocene continental faunal assemblage from tropical North America

Journal of South American Earth Sciences, 2015

To date, the terrestrial faunal record of the North American late Eocene has been recovered from its subtropical and temperate regions. We report the first late Eocene continental faunal assemblage from tropical North America, in southern Mexico. Fossil specimens were collected from mudstones that crop out in the Municipality of Santiago Yolom ecatl, in northwestern Oaxaca. Previously published KeAr ages of 32.9 ± 0.9 and 35.7 ± 1.0 Ma in overlain nearby volcanic rocks and biostratigraphy of these new localities suggests a Chadronian mammal age for this new local fauna. The assemblage is composed by two turtle taxa, Rhineura, two caniform taxa, a sciurid, a jimomyid rodent, a geomyine rodent, Gregorymys, Leptochoerus, Perchoerus probus, Merycoidodon, a protoceratid, Poebrotherium, Nanotragulus, Miohippus assinoboiensis, a chalicotherid, a tapiroid, cf. Amynodontopsis, Trigonias and the hymenopteran ichnofossils Celliforma curvata and Fictovichnus sciuttoi. The records of these taxa in northwestern Oaxaca greatly expand southerly their former geographic distribution in North America. The records of the geomorph rodents and Nanotragulus extend their former known biochronological range to the late Eocene. The hymenopteran ichnofossils in the localities suggest the presence of a bare soil after periodic waterlogging, under a sub-humid to sub-arid climate. This new local fauna represents the first glimpse of Eocene vertebrate and invertebrate terrestrial life from tropical North America.

Insights into the Neotropics Prior to the Great American Biotic Interchange: new evidence of mammalian predators from the Miocene of Northern Colombia

A new species of Sparassodonta (Mammalia, Metatheria), Lycopsis padillai, sp. nov., is described on the basis of a partial left maxilla with M1–M4 and fragments of lacrimal and jugal. The material comes from the early to early middle Miocene Castilletes Formation, La Guajira Peninsula, Colombia. This specimen represents the northernmost record of a fossil metatherian in South America and integrates a highly diverse vertebrate association, recently discovered in the north of Colombia. The La Guajira specimen is referred to the genus Lycopsis, as supported by the results of our phylogenetic analysis. This analysis also demonstrates that species of Lycopsis (L. torresi, L. longirostrus, L. viverensis, and L. padillai) constitute a monophyletic group and are placed as the basal taxon of Borhyaenoidea. Lycopsis padillai is a large-sized sparassodont with a body mass of about 22 kg. The presence of Lycopsis from La Guajira extends the geographical distribution of the genus to the entire S...

Paleosol and ichnofossil evidence for significant Neotropical habitat variation during the late middle Miocene (Serravallian)

Palaeogeography, Palaeoclimatology, Palaeoecology, 2017

We use paleopedology and ichnology to elucidate the habitat of the late middle Miocene fossil site of Quebrada Honda, southern Bolivia. The paleosols represent three pedotypes, Type 1 and Type 2 paleosols are interpreted as Inceptisols (Eutrudepts) and Entisols (Udifluvents), respectively, which formed on proximal and distal floodplains in a seasonal, sub-humid to humid wooded grassland-like vegetative community. Type 3 paleosols are interpreted as Inceptisols (Calciustepts) that formed in more densely vegetated wooded grassland-like vegetative communities on distal floodplains in a strongly seasonal sub-humid to semi-arid environment. The ichnofossil assemblage of Quebrada Honda includes Celliforma, Coprinisphaera, Taenidium, Fictovichnus, Planolites, Skolithos, Katarrhedrites, and root traces and represents heterogeneous communities dominated by soil arthropods and plants. The physical and geochemical properties of the paleosols, including low maturity, poor development of horizons, and the overall moderate estimates of mean annual precipitation, indicate changes in soil moisture due to seasonal precipitation and flooding and low but varying degrees of temporal stability. The diverse ichnofossil assemblage of Quebrada Honda reflects environments with greater primary productivity and temporal stability than those of nearby Cerdas, Bolivia, which are several million years older. Quebrada Honda's inferred paleoenvironments differ markedly from those of La Venta, Colombia, indicating that dissimilar habitats may partly or principally account for the vastly different faunas of these two well-sampled and contemporaneous fossil localities.

Suarez C, Forasiepi AM, Goin FJ, Jaramillo C (2015) Insights into the Neotropics prior to the Great American Biotic Interchange: new evidence of mammalian predators from the Miocene of Northern Colombia.

Journal of Vertebrate Paleontology , 2015

A new species of Sparassodonta (Mammalia, Metatheria), Lycopsis padillai, sp. nov., is described on the basis of a partial left maxilla with M1–M4 and fragments of lacrimal and jugal. The material comes from the early to early middle Miocene Castilletes Formation, La Guajira Peninsula, Colombia. This specimen represents the northernmost record of a fossil metatherian in South America and integrates a highly diverse vertebrate association, recently discovered in the north of Colombia. The La Guajira specimen is referred to the genus Lycopsis, as supported by the results of our phylogenetic analysis. This analysis also demonstrates that species of Lycopsis (L. torresi, L. longirostrus, L. viverensis, and L. padillai) constitute a monophyletic group and are placed as the basal taxon of Borhyaenoidea. Lycopsis padillai is a large-sized sparassodont with a body mass of about 22 kg. The presence of Lycopsis from La Guajira extends the geographical distribution of the genus to the entire South America, representing the sparassodont with the widest latitudinal distribution.

A new vertebrate continental assemblage from the Tortonian of Venezuela

Swiss Journal of Palaeontology, 2018

A wide variety of aquatic vertebrates from fluvio-lacustrine facies of northern South America (Colombia and Venezuela) have been used as unequivocal evidence to support hydrographic connections between western Amazonia and the Proto-Caribbean Sea during the Miocene. By the end of the Miocene, changes in the major hydrographic systems of the region produced losses of habitats and a regional faunal turnover, as has been documented in the geological record of the Urumaco region. Here, we report a new Tortonian aquatic and terrestrial vertebrate assemblage from two localities of the Caujarao Formation (El Muaco Member) in western Venezuela. The vertebrate assemblage includes a gharial (cf. Gryposuchus pachakamue), alligatorid crocodylians (Purussaurus and Alligatoridae indet.), a freshwater turtle (Chelus sp.), snakes (cf. Eunectes sp.), serrasalmids and pimelodids and thorny catfishes, a rodent (Potamarchus sp.), pampatheres (Scirrotherium sp.), sloths, as well as plant remains (coal and amber). Although the Caujarao Formation has been referred to as a fully marine environment, the new assemblage reported here suggests a freshwater input to the coastal area. Taxonomic and biogeographic affinities between the Muaco Member community and that reported from the Miocene proto-Amazonian systems are indicative of the persistence of ecological and hydrographic continuity at minimum until the end of the Miocene in at least an area of northwestern South America.