American Interchange Research Articles

Importación de penicilina y estreptomicina desde los Estados Unidos de Norteamérica entro los años 1946 y 1950 y su transporte mediante los buques de la Compañia Trasatlántica española

After the achievement of the industrial production of penicillin in the United States of America in 1944, there was a massive worldwide export of this drug. This note describes unknown data associated with the arrival of antibiotics in our country. The analysis of the bibliographic collection of the shipping company Pérez y Cía has allowed us to analyze in detail the importance of the Compañía Trasatlántica Española ships in importing penicillin and streptomycin from the US between 1946 and 1950. During the years 1946 to 1948, more than twenty pharmaceutical companies, both Spanish and North American, imported small quantities of these antibiotics. However, in the period between 1949 and 1950, the Spanish pharmaceutical company Pan-Química S.L. and the North American Interchange Commercial Corporation, a subsidiary of the Banco Exterior de España, cooperated to supply the country with large quantities of antibiotics, before the start-up of the two main national companies producing antibiotics, the Compañía Española de Penicilina y Antibióticos (CEPA) and Antibióticos S.A. in 1951.

Biophysical and Biocultural Upheavals in Mesoamerica, a Conservation Perspective: Mountains, Maize-Milpa, and Globalization

Three upheavals shaped southern Mexico to Panama (SMP) biodiversity: 1. The Great American Interchange that allowed migrations between the Neotropical and the Nearctic biogeographic realms; 2. human colonization with the generation of Mesoamerican cultures; and 3. the Spaniards’ arrival and globalization.Tectonic events generated a narrow piece of land with steep topography and high environmental heterogeneity, demanding high levels of local adaptation. Habitat size is usually restricted and reduced by frequent disturbances. Topography imposes few options for individuals forced to displace. Thus, extinction risks should be unusually high. Humans initiated an ongoing defaunation process and introduced the maize and the milpa, an itinerant maize-based slash-and-burn polyculture, which depends on revegetation to re-establish soil fertility. Also, the milpa is a most important pre-Hispanic legacy, a biocultural and landrace reservoir actively affecting landscape configuration, succession, soil development, and the genetic architecture of the species. Unprecedented human epidemics and soil, biodiversity, and culture erosion followed behind the Spanish aftermath and the subsequent globalization. > 63 million people and ≈100 ethnic groups inhabit SMP in 2020, which, with the biota, share the same problems of climate change, disturbance, and acculturation. SMP has been the scenario of severe climate change, fastest and deadliest extinction events (amphibians), a most spectacular exotic-species invasion (Africanized honeybees), and accelerated deforestation, defaunation, and acculturation. Biocultural conflicts between native and non-native people are globalization byproducts and sources of habitat destruction and species decline. Bottom-up initiatives are likely the best option for conservation in indigenous areas, whereas honest (i.e., with truly conservation intentions) top-down initiatives are helpful if the affected people are considered subjects (no objects) of conservation plans. We suggest some unique areas requiring conservation attention and analyzed current conservation initiatives. Not a single initiative is best suited for all conservation needs in SMP. Protection of all successional stages is critical for resilience and revegetation. Conservation of the milpa system (crop fields and subsequent fallows) is an optimal option for minimizing tradeoffs between conservation and people needs and safeguarding traditional culture and local landraces but is limited to areas with indigenous people and may not work for species with large home ranges.

“What a beautiful world. But is it the world we live in?”

Abstract The present two-phased study set out to identify simplified and non-simplified sources of input popular among learners of English as a foreign language (EFL) and to compare and contrast the manifestations of impoliteness strategies and responses to them in such resources. First, a rather comprehensive survey conducted among 250 adult EFL learners revealed that English TV series and movies of comedy and crime genres were the most popular non-simplified sources of input, while the popular simplified sources were American English File and Interchange ELT textbooks. Then, the results of our in-depth qualitative-quantitative, comparative, macro- and micro-analysis (adopting a variety of stringent incivility frameworks) indicated there were noticeable quantitative and/or qualitative differences in (re-)presenting face-threatening acts between the two sources. Generally, while EFL learners are not judiciously familiarized with various impoliteness strategies and their responses in the textbooks, they are almost bombarded with them through their favourite media. Underlining the inherent instructional and motivational impact of both language input sources and the possible detrimental bearing of underrepresentation and/or overrepresentation of impoliteness for the learners’ pragmatic competence, the study concludes with a discussion of our findings’ implications for stake-holders including language learners and education specialists.

Close relationship of Plasmodium sequences detected from South American pampas deer (Ozotoceros bezoarticus) to Plasmodium spp. in North American white-tailed deer.

We report, for the first time, the presence of ungulate malaria parasites in South America. We conducted PCR-based surveys of blood samples of multiple deer species and water buffalo from Brazil and detected Plasmodium sequences from pampas deer (Ozotoceros bezoarticus) samples. Phylogenic analysis revealed that the obtained sequences are closely related to the Plasmodium odocoilei clade 2 sequence from North American white-tailed deer (Odocoileus virginianus). Nucleotide differences suggest that malaria parasites in South American pampas deer and North American P. odocoilei clade 2 branched more recently than the Great American Interchange.

Diversity of limno-terrestrial tardigrades of the Americas in relation to the Great American Biotic Interchange hypothesis (GABI)

Zoogeographical studies on Tardigrada are limited by the extent of our knowledge on tardigrade taxonomy and faunistics. In this paper we analyse the relationships between the tardigrade fauna of North, Central and South America (Nearctic and Neotropical regions) and provide the first test of whether the tardigrade fauna of the Americas has undergone the great American interchange. Our analyses were based on 384 tardigrade species records obtained for 1702 localities in North, South and Central America. We found that (1) some tardigrade species are distributed, as predicted by the Great American Biotic Interchange (GABI) hypothesis, on both sides of the Panama Isthmus; (2) the Central American tardigrade fauna is specific and different from both the South and the North American faunas, although it is closer to the tropical areas of South America; (3) either the tardigrade fauna of South and North America appear to be more similar to each other than to that of Central America, or there is a Nearctic–Neotropic division of the faunas; and (4) endemism in Central America suggests a more complex biogeographical process than predicted by the connection of two continents.

Macroecological evidence for competitive regional-scale interactions between the two major clades of mammal carnivores (Feliformia and Caniformia).

Geographical gradients in species diversity are often explained by environmental factors such as climate and productivity. Biotic interactions play a key role in evolutionary diversification and may therefore also affect diversity patterns, but this has rarely been assessed. Here, we investigate whether negative competitive interactions shape the diversity patterns of the two major mammalian clades of carnivores, the suborders Caniformia (dogs and allies) and Feliformia (cats and allies) within the order Carnivora. We specifically test for a negative effect of feliform species richness on caniform species richness by a natural experiment, The Great American Interchange, which due to biogeographic lineage history and climate patterns caused tropical South America to be colonized by most caniform families, but only one feliform family. To this end we used regression modelling to investigate feliform and caniform richness patterns and their determinants with emphasis on contrasting the Old and New World tropics. We find that feliform richness is elevated in the Old World Tropics, while caniform richness is elevated in the New World Tropics. Models based on environmental variables alone underpredict caniform richness and overpredict feliform richness in the New World and vice versa in the Old World. We further show that models including feliform richness as a predictor for caniform species richness significantly improve predictions at the continental scale, albeit not at finer scales. Our results are consistent with a negative effect of feliforms on regional-scale caniform diversification within the tropics, probably indicating that niche space occupancy by the one clade constrains diversification in the other in the build-up of regional faunas, while negative interactions at smaller scales may be unimportant due to niche differentiation within the regional faunas.

Molecular Evidence of Demographic Expansion of the Chagas Disease Vector Triatoma dimidiata (Hemiptera, Reduviidae, Triatominae) in Colombia

Background Triatoma dimidiata is one of the most significant vectors of Chagas disease in Central America and Colombia, and, as in most species, its pattern of genetic variation within and among populations is strongly affected by its phylogeographic history. A putative origin from Central America has been proposed for Colombian populations, and high genetic differentiation among three biographically different population groups has recently been evidenced. Analyses based on putatively neutral markers provide data from which past events, such as population expansions and colonization, can be inferred. We analyzed the genealogies of the nicotinamide adenine dinucleotide dehydrogenase 4 (ND4) and the cytochrome oxidase subunit 1-mitochondrial genes, as well as partial nuclear ITS-2 DNA sequences obtained across most of the eco-geographical range in Colombia, to assess the population structure and demographic factors that may explain the geographical distribution of T. dimidiata in this country.ResultsThe population structure results support a significant association between genetic divergence and the eco-geographical location of population groups, suggesting that clear signals of demographic expansion can explain the geographical distribution of haplotypes of population groups. Additionally, empirical date estimation of the event suggests that the population's expansion can be placed after the emergence of the Panama Isthmus, and that it was possibly followed by a population fragmentation process, perhaps resulting from local adaptation accomplished by orographic factors such as geographical isolation.ConclusionInferences about the historical population processes in Colombian T. dimidiata populations are generally in accordance with population expansions that may have been accomplished by two important biotic and orographic events such as the Great American Interchange and the uplift of the eastern range of the Andes mountains in central Colombia.

Fossil evidence for earliest Neogene American faunal interchange: Boa (Serpentes, Boinae) from the early Miocene of Panama

ABSTRACT Isolated precloacal vertebrae from the early to middle Miocene Gaillard Cut of Panama represent the first Central American fossil record of the extant boine snake Boa and constrain dispersal of the genus into Central America from South America as no younger than approximately 19.3 Ma. Boa from the Las Cascadas fossil assemblage and the Centenario Fauna represent the oldest record of terrestrial southern vertebrate immigration into Central America, and demonstrate American interchange by the earliest Neogene. Interchange of snakes precedes contiguous terrestrial connection between Central and South America by approximately 17 Ma, necessitating dispersal across an approximately 100 km wide marine strait. The biogeographic history of snakes across the Neotropics is distinct from the mammalian record, and indicates a more complicated assembly of New World vertebrate faunas than previously recognized.

Two new genera of peccaries (Mammalia, Artiodactyla, Tayassuidae) from upper Miocene deposits of the Amazon Basin

Two new, extinct taxa of peccaries from upper Miocene deposits of the western Amazon Basin provide the first data documenting the presence of these North American mammals in South America in the Miocene. One,Sylvochoerus woodburnein. gen. n. sp., is allied morphologically toTayassu pecari, whereas the second,Waldochoerus basslerin. gen. n. sp., is more similar toPecari tajacu. Both new taxa reflect an intermediate position between middle Miocene peccaries and modernTayassuandPecari. The specimens reported here were unstudied, but when collected they were referred to living species ofTayassuandPecaribased on their general similarity to species of those two living genera, and they were dated to the Pleistocene, presumably based on a long–standing model of the Great American Faunal Interchange. The presence of peccaries in South America at approximately the same time that South American ground sloths began appearing in upper Miocene deposits of North America, and soon after the appearance of gomphotheres in South America, indicates that dispersal between the Americas was earlier and involved more taxa than previously interpreted. Molecular divergence data are consistent, in part, with a late Miocene dispersal of peccaries to South America.

Four Events of Host Switching in Aspidoderidae (Nematoda) Involve Convergent Lineages of Mammals

The Great American Interchange resulted in the mixing of faunistic groups with different origins and evolutionary trajectories that underwent rapid diversification in North and South America. As a result, groups of animals of recent arrival converged into similar habits and formed ecological guilds with some of the endemics. We present a reconstruction of the evolutionary events in Aspidoderidae, a family of nematodes that infect mammals that are part of this interchange, i.e., dasypodids, opossums, and sigmodontine, geomyid, and hystricognath rodents. By treating hosts as discrete states of character and using parsimony and Bayesian inferences to optimize these traits into the phylogeny of Aspidoderidae, we reconstructed Dasypodidae (armadillos) as the synapomorphic host for the family. In addition, 4 events of host switching were detected. One consisted of the switch from dasypodids to hystricognath rodents, and subsequently to geomyid rodents. The remaining set of events consisted of a switch from dasypodids to didelphid marsupials and then to sigmodontine rodents. The reconstruction of the ancestral distribution suggests 3 events of dispersal into the Nearctic. Two of these invasions would suggest that 2 different lineages of dasypodid parasites entered the Northern Hemisphere at different times, which is consistent with the presence of 2 lineages of armadillos in Mexico.

Molecular phylogeny of the New World bloodfeeding leeches of the genus Haementeria and reconsideration of the biannulate genus Oligobdella

The phylogenetic relationships of species of the New World bloodfeeding genus Haementeria were investigated for the first time. The analysis included five molecular markers. The mitochondrial COI, 12S and ND1 as well as the nuclear 28S and ITS. The evolutionary history of the group was investigated through Maximum Parsimony and Bayesian Inference. Both phylogenetic methods resulted in highly congruent hypotheses. The correlation between the phylogeny and morphological traits such as eyespot number, annulation, Lang’s organs, salivary glands, bacteriomes and reproductive organs is discussed. Restricted to Haementeria are Lang’s organs, spherical bacteriomes and ovaries forming an anterior ring around the ventral nerve cord. In addition, Oligobdella brasilensis was formally transferred to Haementeria, providing additional arguments for the disposal of the genus Oligobdella. Haementeria gracilis is shown to be just a junior synonym of Haementeria depressa as suggested by previous authors. Finally, the geographical distribution of species of Haementeria was compared with that of other non-leech and leech taxa. Multiple events of South–North American interchange were proposed to explain the current geographical distribution of the species of Haementeria.

The evolution of South American endemic canids: a history of rapid diversification and morphological parallelism

The origin of endemic South American canid fauna has been traditionally linked with the rise of the Isthmus of Panama, suggesting that diversification of the dog fauna on this continent occurred very rapidly. Nevertheless, despite its obvious biogeographic appeal, the tempo of Canid evolution in South America has never been studied thoroughly. This issue can be suitably tackled with the inference of a molecular timescale. In this study, using a relaxed molecular clock method, we estimated that the most recent common ancestor of South American canids lived around 4 Ma, whereas all other splits within the clade occurred after the rise of the Panamanian land bridge. We suggest that the early diversification of the ancestors of the two main lineages of South American canids may have occurred in North America, before the Great American Interchange. Moreover, a concatenated morphological and molecular analysis put some extinct canid species well within the South American radiation, and shows that the dental adaptations to hypercarnivory evolved only once in the South American clade.

Amazonian magnetostratigraphy: Dating the first pulse of the Great American Faunal Interchange

Abstract The chronostratigraphy of the youngest Neogene deposits of the Amazon Basin, which comprise the Madre de Dios Formation in eastern Peru, remains unresolved. Although 40 Ar/ 39 Ar dates on two volcanic ashes from this formation in Peru provide critical baseline data points, stratigraphic correlations among scattered riverine outcrops in adjacent drainage basins remain problematic. To refine the chronostratigraphy of the Madre de Dios Formation, we report here the magnetostratigraphy of an outcrop on the Madre de Dios River in southeastern Peru. A total of 18 polarity zones was obtained in the ∼65-m-thick Cerro Colorado section, which we correlate to magnetozones Chrons C4Ar to C2An (9.5–3.0 Ma) based on the prior 40 Ar/ 39 Ar dates. These results confirm the late Miocene age of a gomphothere recovered from the Ipururo Formation, which underlies the late Miocene Ucayali Unconformity at the base of the Cerro Colorado outcrop. The results also support earlier interpretations of a late Miocene age for other fossils of North American mammals recovered from basal conglomeratic deposits of the Madre de Dios Formation immediately above the Ucayali Unconformity. These mammals include other gomphotheres, peccaries, and tapirs, and their presence in South America in the late Miocene is recognized as part of the first pulse of the Great American Faunal Interchange.

Molecular Phylogenetics of a Clade of Lowland Tanagers: Implications for Avian Participation in the Great American Interchange

ABSTRACT. The importance of the formation of the Panamanian land bridge for mammalian diversification in the New World is well documented; however, studies investigating the role of this land bridge in avian diversification have only recently been reported. We used mitochondrial DNA data to reconstruct the phylogeny of a group of lowland tanagers (Thraupidae) that contains species distributed in both Central America and South America. Phylogenetic analyses identified a clade that includes all 26 species in the genera Tachyphonus, Ramphocelus, Eucometis, Lanio, Trichothraupis, Coryphospingus, and Rhodospingus. Three of these species (Rhodospingus cruentus, Coryphospingus cucullatus, and C. pileatus) have traditionally been classified with the finches (Emberizidae); here, we show that they are tanagers. The genus Tachyphonus is polyphyletic, with some species more closely related to species in the genus Ramphocelus than they are to other Tachyphonus. The ancestor of the entire clade was distributed in South...

The Great American Interchange in birds: a phylogenetic perspective with the genus Trogon

The 'Great American Interchange' (GAI) is recognized as having had a dramatic effect on biodiversity throughout the Neotropics. However, investigation of patterns in Neotropical avian biodiversity has generally been focused on South American taxa in the Amazon Basin, leaving the contribution of Central American taxa under-studied. More rigorous studies of lineages distributed across the entire Neotropics are needed to uncover phylogeographical patterns throughout the area, offering insights into mechanisms that contribute to overall Neotropical biodiversity. Here we use mitochondrial DNA sequence data and intensive geographical sampling from the widespread Neotropical avian genus Trogon to investigate the role of the GAI in shaping its phylogeographical history. Our results show that genetic diversity in Trogon exceeds the perceived biodiversity, and that the GAI resulted in lineage diversification within the genus. Despite greater diversity in South America, a Central American centre of origin with multiple and independent dispersals into South America is indicated. These dispersals were followed by the evolution of divergent lineages associated with the Andes Mountains and other South American geographical features. According to our phylogenetic reconstructions, several species, which were originally defined by morphological characters, are nonmonophyletic. In sum, our results elucidate the evolutionary history of Trogon, reveal patterns obscured by extant biodiversity, and serve as a biogeographical model to consider in future studies.

Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange

Research Article| February 01, 2007 Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange Bruce J. MacFadden; Bruce J. MacFadden 1Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA Search for other works by this author on: GSW Google Scholar Joann Labs-Hochstein; Joann Labs-Hochstein 1Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA Search for other works by this author on: GSW Google Scholar Richard C. Hulbert, Jr; Richard C. Hulbert, Jr 1Florida Museum of Natural History, University of Florida, Gainesville, Florida 32611, USA Search for other works by this author on: GSW Google Scholar Jon A. Baskin Jon A. Baskin 2Department of Biology, Texas A & M University, MSC 158, Kingsville, Texas 78363, USA Search for other works by this author on: GSW Google Scholar Geology (2007) 35 (2): 123–126. https://doi.org/10.1130/G23186A.1 Article history received: 11 Jul 2006 rev-recd: 12 Sep 2006 accepted: 16 Sep 2006 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Bruce J. MacFadden, Joann Labs-Hochstein, Richard C. Hulbert, Jon A. Baskin; Revised age of the late Neogene terror bird (Titanis) in North America during the Great American Interchange. Geology 2007;; 35 (2): 123–126. doi: https://doi.org/10.1130/G23186A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The giant flightless terror bird Titanis walleri is known from Florida and Texas during the late Neogene. The age of T. walleri is problematic because this taxon co-occurs with temporally mixed (i.e., time-averaged) faunas at two key sites. Thus, prior to this study, T. walleri from the Santa Fe River, Florida (type locality), was either as old as late Pliocene (ca. 2.2 Ma) or as young as latest Pleistocene (ca. 15 ka). Likewise, T. walleri from the Nueces River, Texas, was either early Pliocene (ca. 5 Ma) or latest Pleistocene (ca. 15 ka). In order to better resolve this age range, the rare earth element (REE) patterns of T. walleri from the Santa Fe River, Florida, were compared to two biochronologically distinctive groups (late Pliocene versus late Pleistocene) of fossil mammals from the same locality. Similarly, the REE patterns of T. walleri from Texas were compared to two groups (early Pliocene versus latest Pleistocene) of fossil mammals from the same locality. The REE patterns of T. walleri from Florida are indistinguishable from those of the co-occurring late Pliocene mammals. Likewise, the REE pattern of T. walleri from Texas is indistinguishable from those of the co-occurring early Pliocene mammals. Given these REE constraints, the revised age of T. walleri is early Pliocene in Texas (ca. 5 Ma) and late Pliocene (ca. 2.2–1.8 Ma) in Florida. As such, T. walleri is interpreted as an early immigrant during the Great American Interchange prior to the formation of the Isthmian land bridge. No evidence currently exists for Pleistocene T. walleri in North America. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Phylogeny of the Procyonidae (Mammalia: Carnivora): Molecules, morphology and the Great American Interchange

The Procyonidae (Mammalia: Carnivora) have played a central role in resolving the controversial systematics of the giant and red pandas, but phylogenetic relationships of species within the family itself have received much less attention. Cladistic analyses of morphological characters conducted during the last two decades have resulted in topologies that group ecologically and morphologically similar taxa together. Specifically, the highly arboreal and frugivorous kinkajou ( Potos flavus) and olingos ( Bassaricyon) define one clade, whereas the more terrestrial and omnivorous coatis ( Nasua), raccoons ( Procyon), and ringtails ( Bassariscus) define another clade, with the similar-sized Nasua and Procyon joined as sister taxa in this latter group. These relationships, however, have not been tested with molecular sequence data. We examined procyonid phylogenetics based on combined data from nine nuclear and two mitochondrial gene segments totaling 6534 bp. We were able to fully resolve relationships within the family with strongly supported and congruent results from maximum parsimony, maximum likelihood, minimum evolution, and Bayesian analyses. We identified three distinct lineages within the family: a ( Nasua, Bassaricyon) clade, a ( Bassariscus, Procyon) clade, and a Potos lineage, the last of which is sister to the other two clades. These findings, which are in strong disagreement with prior fossil and morphology-based assessments of procyonid relationships, reemphasize the morphological and ecological flexibility of these taxa. In particular, morphological similarities between unrelated genera possibly reflect convergence associated with similar lifestyles and diets rather than ancestry. Furthermore, incongruence between the molecular supermatrix and a morphological character matrix comprised mostly of dental characters [Baskin, J.A., 2004. Bassariscus and Probassariscus (Mammalia, Carnivora, Procyonidae) from the early Barstovian (Middle Miocene). J. Vert. Paleo. 24, 709–720] may be due to non-independence among atomized dental characters that does not take into account the high developmental genetic correlation of these characters. Finally, molecular divergence dating analyses using a relaxed molecular clock approach suggest that intergeneric and intrageneric splits in the Procyonidae mostly occurred in the Miocene. The inferred divergence times for intrageneric splits for several genera whose ranges are bisected by the Panamanian Isthmus is significant because they suggest diversification well precedes the Great American Interchange, which has long been considered a primary underlying mechanism for procyonid evolution.

Titanis walleri: Bones of Contention

Titanis walleri, one of the largest and possibly the last surviving member of the otherwise South American Phorusrhacidae is reconsidered in light of all available data. The only verified phorusrhacid recovered in North America, Titanis was believed to exhibit a forward-extending arm with a flexible claw instead of a traditional bird wing like the other members of this extinct group. Our review of the already described and undescribed Titanis material housed at the Florida Museum of Natural History suggest that Titanis: (1) was like other phorusrhacids in sporting small, ineffectual ratite-like wings; (2) was among the tallest of the known phorusrhacids; and (3) is the last known member of its lineage. Hypotheses of its range extending into the Pleistocene of Texas are challenged, and herein Titanis is presumed to have suffered the same fate of many other Pliocene migrants of the Great American Interchange: extinction prior to the Pleistocene.

New Pleistocene vertebrate fauna from El Salvador

The discovery of an Early-Middle Pleistocene continental vertebrate fauna from El Salvador is here reported. These fossils provide information about a poorly studied geographic area that played an important role during the Great American Faunal Interchange. The fauna is dominated by numerous remains of the proboscidean Cuvieronius tropicus and probably represents the largest known concentration of this genus in America. A number of living taxa are first recorded as fossils in El Salvador, including Crocodylus acutus, previously unknown as a fossil elsewhere. Hesperotestudo crassiscutata, Glyptotherium arizonae, Palaeolama, Hemiauchenia cf. H. seymourensis and Equus conversidens, are recorded for the first time in Central America. The new locality also holds the oldest record of Mazama, and the southernmost records of Glyptotherium arizonae and Equus conversidens. At least 17 taxa are represented in the new site, constituting the richest Central American continental vertebrate locality hitherto known.

Rediscovery of Choroterpes atramentum in Costa Rica, type species of Tikuna new genus (Ephemeroptera: Leptophlebiidae: Atalophlebiinae), and its role in the "Great American Inter-change"

A new genus, Tikuna, is described based on recent collections of adults and nymphs of Choroterpes atramentum Traver from western Costa Rica. All recent collections are from streams on or near the Nicoya Complex, the oldest geological formation in Lower Central America. Tikuna belongs to a lineage of South American Atalophlebiinae (Leptophlebiidae: Ephemeroptera) whose origin is hypothesized to have been in the late Cretaceous–early Tertiary. Some implications of the distribution of Tikuna for theories on the origin of Costa Rica’s biota are discussed.