Thomas Defler (2018)
Ancient Mammals of Gondwanan South America.
History of Terrestrial Mammals in South America pp 29-44Â
Topics in Geobiology 42. Springer, Cham
This is a synopsis of what is known of South American mammals from the Mesozoic Era, which begins (according to present information) in the Early Jurassic around 183â174 Ma when a triconodont tooth was found in Patagonia. More spectacular additions to the mammalian fauna are known for the Late Jurassic 168â161 million years ago, representing the most completely known biota from Middle to Late Jurassic for South America, comprising australosphenid mammals (relatives of the platypus) and the now extinct triconodont mammals. The Early Cretaceous became known for the increasing number of known fossils. This Cretaceous fauna was dominated in South America by dryolestid mammals, which were closely related to the modern placental mammals. During this latter part of the Mesozoic, a couple of spectacular fossils were found: Vincelestes neuquenianus and Cronopio dentiacutus, both of which are illustrated and discussed in this chapter. This ancient fauna survived the Chicxulub impact (the K/T transition) into the early part of the Paleogene but rather quickly replaced by a more modern fauna (the metatheres and primitive ungulates) that invaded from the north.
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Giovanne M. Cidade, Daniel Fortier & Annie Schmaltz Hsiou (2018)
The crocodylomorph fauna of the Cenozoic of South America and its evolutionary history: A review.
Journal of South American Earth Sciences (advance online publication)
Highlights
This paper is a review of the South American fossil crocodylomorph fauna.
The fauna is comprised mainly by Dyrosauride, Sebecidae and Caimanine during the Paleogene.
Gavialoids arrived between the Paleogene and the Neogene.
End of Miocene: geomorphological changes in the continent caused the extinction of many taxa.
Caiman, Melanosuchus, Paleosuchus and Crocodylus solely comprise the fauna from the Pliocene onwards.
Abstract
The fossil crocodylomorph fauna of the Cenozoic of South America is very rich and diverse. Historically, few publications have been dedicated to providing an overall review of this fauna, with most reviews focusing on specific areas. However, the fact that many new species, taxonomic reviews and description of new specimens have been proposed in the last decade makes a comprehensive review of the fossil crocodylomorph fauna of the South American Cenozoic necessary. The only crocodylomorph lineages to have a fossil record comprising Late Cretaceous and Cenozoic deposits in South America is the Dyrosauridae. Sebecidae or its predecessors, however, are very likely to have inhabited the continent during the Cretaceous-Paleogene transition as well; both Dyrosauridae and Sebecidae are considered here to have survived the Cretaceous-Paleogene extinction while inhabiting South America. Caimaninae (Alligatoroidea) arrived either in the late Cretaceous or in the early Paleocene coming from North America. The fossil record of Caimaninae is present, however, only from the Paleocene. By the Eocene, there are no records of Dyrosauridae in South America; this group was globally extinct after the Eocene, possibly due to the global cooling that occurred by the end of the epoch. Sebecids and caimanines solely comprised the crocodylomorph fauna of the continent until the Miocene, where there are the first records of Gavialoidea (Gryposuchinae) and a possible first dispersion of Crocodyloidea, through the tentative tomistomines Charactosuchus and Brasilosuchus. Gryposuchinae likely arrived in the continent from Africa or from Asia during the Oligocene. Charactosuchus and Brasilosuchus may have come from North America where tomistomines lived from the Oligocene to the Pliocene. Sebecids were extinct after the middle Miocene; Charactosuchus, Gryposuchinae, Purussaurus, Mourasuchus and durophagous caimanines such as Gnatusuchus were extinct after the late Miocene. These extinctions are related to changes in the drainage basins caused by elevation of the Andes mountain range. Only the extant caimanine Caiman, Melanosuchus and Paleosuchus would survive the Miocene, being enriched by Crocodylus from the Pliocene onwards, which is likely that Crocodylus arrived in the American continents from Africa. The current fossil record indicates that these four genera comprise the extant crocodylian fauna of the continent since the Pliocene. Although our knowledge on crocodylomorph fossil fauna of the South American Cenozoic has increased continuosly, especially in the last decade, much yet must be done, especially on the taxonomy and phylogeny of Brasilosuchus and Charactosuchus, fieldworks in Paleogene and Pliocene localities, and the evolution of the specialized Caimaninae morphotypes.
Morgan, Gary S.; Albury, Nancy Ann, 1955-; RÃmoli, Renato O.; Lehman, Phillip.; Rosenberger, Alfred L.; Cooke, SiobhÃn B. (2018)
The Cuban crocodile (Crocodylus rhombifer) from late Quaternary underwater cave deposits in the Dominican Republic.
American Museum Novitates 3916: 1-56
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Late Quaternary fossils representing a locally extinct population of the Cuban crocodile (Crocodylus rhombifer) are reported from two underwater caves in the Dominican Republic. A large fossil sample of C. rhombifer, from Oleg's Bat Cave near Bavaro in the southeastern Dominican Republic, consists of four nearly complete skulls, numerous isolated cranial elements and mandibles, and more than 100 postcranial bones representing most of the skeleton. These fossils were collected from a completely submerged portion of the cave at a depth of 11 m and about 100 m from the nearest entrance. A skull, mandibles, and two vertebrae of a Cuban crocodile were also found in a second cave called Ni-Rahu, northeast of Santo Domingo. We identify the fossil crocodile skulls from the Dominican Republic as Crocodylus rhombifer because they share the following characters with modern skulls of C. rhombifer from Cuba (as well as fossil skulls from Cuba, the Bahamas, and Cayman Islands): short, broad, and deep rostrum; large orbits; convex nasals along the midline (midrostral boss); prominent swelling on the lacrimals anterior and medial to the orbits; low but obvious ridges extending anteriorly from the lacrimals to the nasals and posteriorly from the lacrimals to the prefrontals and frontals, outlining a distinct diamond- or rhomboid-shaped structure; strongly concave interorbital region and cranial roof; high, narrow ridges on the internal margins of the orbits, extending from the prefrontals to the frontals and posteriorly to the postorbitals; prominent ridges along the lateral margins of the cranial roof on the postorbitals and squamosals, terminating as noticeable protuberances on the posterolateral corners of the squamosals; premaxillary/maxillary suture on the palate essentially horizontal or transverse to the long axis of the skull at the level of the first maxillary tooth; 13 teeth in the maxilla. Certain aspects of the ecology and anatomy of living Crocodylus rhombifer in Cuba, and carbon isotope data from fossil crocodile bones from both the Dominican Republic and the Bahamas, indicate that the Cuban crocodile is a terrestrially adapted predator. The fossil deposits in Oleg's Bat Cave and other underwater caves in the Dominican Republic lack freshwater vertebrates, such as fish and turtles, but contain abundant samples of hystricognath rodents, small ground sloths, and other terrestrial vertebrates, including large land tortoises, that apparently were the primary prey of the crocodiles. Bats are abundant in the fossil deposits in Oleg's Bat Cave, and may have been an additional food source. Bone collagen from a tibia of C. rhombifer from Oleg's Bat Cave yielded an AMS radiocarbon date of 6460 Â30 ryrBP (equivalent to 7320 to 7430 cal yrBP). The chronology for the local extinction of C. rhombifer in Hispaniola is currently unknown, except to document the presence of this species in the eastern Dominican Republic in the early Holocene. Radiocarbon dates and historical records confirm that Cuban crocodiles survived into the period of European colonization (post-1492) in the Bahamas and on Grand Cayman. The only species of crocodile currently found in Hispaniola, the American crocodile (C. acutus), occurs in coastal marine habitats and in two inland brackish-water lakes: Lago Enriquillo in the Dominican Republic and the nearby Etang SaumÃtre in Haiti. C. acutus has no fossil record in Hispaniola or elsewhere in the West Indies, suggesting that this species may be a very recent (late Holocene) immigrant in the Antillean region. Crocodylus rhombifer has one of the most limited geographic ranges of any living crocodylian species, known only from freshwater swamps in south-central Cuba and the Isla de Juventud (Isla de Pinos) off the southwestern coast of Cuba. Locally extinct or extirpated populations of C. rhombifer from fossil deposits in the Dominican Republic, Grand Cayman, and the Bahamas document a considerably wider distribution for this species during the Late Quaternary.
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William W. Hay, Robert M. DeConto, Poppe de Boer, Sascha FlÃgel, Ying Song & Andrei Stepashko (2018)
Possible solutions to several enigmas of Cretaceous climate.
International Journal of Earth Sciences (advance online publication)
The nature of the warm climates of the Cretaceous has been enigmatic since the first numerical climate models were run in the late 1970s. Quantitative simulations of the paleoclimate have consistently failed to agree with information from plant and animal fossils and climate sensitive sediments. The âcold continental interior paradoxâ (first described by DeConto et al. in Barrera E, Johnson C (eds) Evolution of the Cretaceous Ocean/climate system, vol 332. Geological Society of America Special Paper, Boulder, pp 391â406, 1999), has been an enigma, with extensive continental interiors, especially in northeast Asia, modeled as below freezing in spite of plant and other evidence to the contrary. We reconsider the paleoelevations of specific areas, particularly along the northeastern Siberian continental margin, where paleofloras indeed indicate higher temperatures than suggested by current climate models. Evidence for significant masses of ice on land during even the otherwise warmest times of the Cretaceous is solved by reinterpretation of the Î18O record of fossil plankton. The signal interpreted as an increase in ice volume on land is the same as the signal for an increase in the volume of groundwater reservoirs on land. The problem of a warm Arctic, where fossil floras indicate that they never experienced freezing conditions in winter, could not be solved by numerical simulations using higher CO2 equivalent greenhouse gas concentrations. We propose a solution by assuming that paleoelevations were less than today and that there were much more extensive wetlands (lakes, meandering rivers, swamps, bogs) on the continents than previously assumed. Usingâ~â8 Ã CO2 equivalent greenhouse gas concentrations and assuming 50â75% water surfaces providing water vapor as a supplementary greenhouse gas on the continents reduces the meridional temperature gradients. Under these conditions the equatorial to polar region temperature gradients produce conditions compatible with fossil and sedimentological evidence.
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Free pdf:Â
Naoki Irie, Noriyuki Satoh & Shigeru Kuratani (2018)
The phylum Vertebrata: a case for zoological recognition
Zoological Letters 4:32Â
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The group Vertebrata is currently placed as a subphylum in the phylum Chordata, together with two other subphyla, Cephalochordata (lancelets) and Urochordata (ascidians). The past three decades, have seen extraordinary advances in zoological taxonomy and the time is now ripe for reassessing whether the subphylum position is truly appropriate for vertebrates, particularly in light of recent advances in molecular phylogeny, comparative genomics, and evolutionary developmental biology. Four lines of current research are discussed here. First, molecular phylogeny has demonstrated that Deuterostomia comprises Ambulacraria (Echinodermata and Hemichordata) and Chordata (Cephalochordata, Urochordata, and Vertebrata), each clade being recognized as a mutually comparable phylum. Second, comparative genomic studies show that vertebrates alone have experienced two rounds of whole-genome duplication, which makes the composition of their gene family unique. Third, comparative gene-_expression_ profiling of vertebrate embryos favors an hourglass pattern of development, the most conserved stage of which is recognized as a phylotypic period characterized by the establishment of a body plan definitively associated with a phylum. This mid-embryonic conservation is supported robustly in vertebrates, but only weakly in chordates. Fourth, certain complex patterns of body plan formation (especially of the head, pharynx, and somites) are recognized throughout the vertebrates, but not in any other animal groups. For these reasons, we suggest that it is more appropriate to recognize vertebrates as an independent phylum, not as a subphylum of the phylum Chordata.