Papuacedrus (Cupressaceae) in Eocene Patagonia: A new fossil link to Australasian rainforests

The 51.9 Ma Laguna del Hunco (LH) and 47.5 Ma Río Pichileufú (RP) floras from Patagonia, Argentina are unusually rich, angiosperm-dominated assemblages with living relatives in the low-latitude West Pacific, neotropics, and temperate southern latitudes. The diverse gymnosperms in these floras are important for Gondwanan biogeographic history and paleoclimatic interpretations. "Libocedrus" prechilensis Berry 1938 (Cupressaceae), previously known only from the holotype (RP), a vegetative branch, is revised here based on new material from both localities, including a seed cone attached to a shoot with cuticle (LH). Characters of these fossils are diagnostic of monotypic Papuacedrus (highlands of New Guinea and Moluccas). Living P. papuana is most abundant in cloud forests receiving up to 4 m rainfall annually, whereas Austrocedrus (Libocedrus) chilensis, the basis of comparison when the fossil species was named, inhabits dry, cold steppe margins to mediterranean climates in southern South America. We establish Papuacedrus prechilensis comb. nov., which simultaneously invalidates a southern South American connection for the fossil floras and reveals a link to West Pacific montane rainforests. Combined evidence indicates a biome similar to extant subtropical, or tropical montane, rainforests that persisted for at least 4.4 Myr, linking elevated floral richness to abundant rainfall.     

Eocene plant diversity at Laguna del Hunco and Río Pichileufú, Patagonia, Argentina

The origins of South America's exceptional plant diversity are poorly known from the fossil record. We report on unbiased quantitative collections of fossil floras from Laguna del Hunco (LH) and Río Pichileufú (RP) in Patagonia, Argentina. These sites represent a frost-free humid biome in South American middle latitudes of the globally warm Eocene. At LH, from 4,303 identified specimens, we recognize 186 species of plant organs and 152 species of leaves. Adjusted for sample size, the LH flora is more diverse than comparable Eocene floras known from other continents. The RP flora shares several taxa with LH and appears to be as rich, although sampling is preliminary. The two floras were previously considered coeval. However, (40)Ar/(39)Ar dating of three ash-fall tuff beds in close stratigraphic association with the RP flora indicates an age of 47.46+/-0.05 Ma, 4.5 million years younger than LH, for which one tuff is reanalyzed here as 51.91+/-0.22 Ma. Thus, diverse floral associations in Patagonia evolved by the Eocene, possibly in response to global warming, and were persistent and areally extensive. This suggests extraordinary richness at low latitudes via the latitudinal diversity gradient, corroborated by published palynological data from the Eocene of Colombia.     

The first Gondwanan Euphorbiaceae fossils reset the biogeographic history of the Macaranga-Mallotus clade

Premise

The spurge family Euphorbiaceae is prominent in tropical rainforests worldwide, particularly in Asia. There is little consensus on the biogeographic origins of the family or its principal lineages. No confirmed spurge macrofossils have come from Gondwana.

Methods

We describe the first Gondwanan macrofossils of Euphorbiaceae, represented by two infructescences and associated peltate leaves from the early Eocene (52 Myr ago [Ma]) Laguna del Hunco site in Chubut, Argentina.

Results

The infructescences are panicles bearing tiny, pedicellate, spineless capsular fruits with two locules, two axile lenticular seeds, and two unbranched, plumose stigmas. The fossils' character combination only occurs today in some species of the Macaranga-Mallotus clade (MMC; Euphorbiaceae), a widespread Old-World understory group often thought to have tropical Asian origins. The associated leaves are consistent with extant Macaranga.

Conclusions

The new fossils are the oldest known for the MMC, demonstrating its Gondwanan history and marking its divergence by at least 52 Ma. This discovery makes an Asian origin of the MMC unlikely because immense oceanic distances separated Asia and South America 52 Ma. The only other MMC reproductive fossils so far known are also from the southern hemisphere (early Miocene, southern New Zealand), far from the Asian tropics. The MMC, along with many other Gondwanan survivors, most likely entered Asia during the Neogene Sahul-Sunda collision. Our discovery adds to a substantial series of well-dated, well-preserved fossils from one undersampled region, Patagonia, that have changed our understanding of plant biogeographic history.     

A new Oligocene Calocedrus from South China and its implications for transpacific floristic exchanges

? Premise of the Study: Calocedrus is among the genera with a typical eastern Asian-western North American disjunct distribution today. The origin of its modern distribution pattern can be better understood by examining its fossil record. ? Methods: The present article reports for the first time a new fossil species of this genus based on compressed material from the Oligocene Ningming Formation of Guangxi, South China, in its present major distribution area in eastern Asia. ? Key Results: Calocedrus huashanensis sp. nov. is most similar to the two extant eastern Asian species, C. macrolepis and C. formosana, in gross morphology of foliage shoots and bears a close resemblance to the latter in cuticle structure. It shows a general similarity to the North American fossil representatives of the genus in alternately branched foliage shoots but is clearly different from the European Paleogene species characterized by oppositely branched leafy shoots. ? Conclusions: This discovery provides new evidence for the floristic exchange of this genus between eastern Asia and North America before the Oligocene (most likely in the Eocene), presumably via the Bering land bridge. The flattened leafy shoots and dimorphic leaves with thin cuticle, open stomatal pits, and shallowly sunken guard cells of the present fossils suggest a rather humid climate during the Oligocene in the Ningming area, South China.     

Dispersal,vicariance, and the Late Cretaceous to early tertiary land mammal biogeography from South America to Australia

A review of paleontological, phyletic, geophysical, and climatic evidence leads to a new scenario of land mammal dispersal among South America, Antarctica, and Australia in the Late Cretaceous to early Tertiary epochs. New fossil land vertebrate material has been recovered from all three continents in recent years. As regards Gondwana, the present evidence suggests that monotreme mammals and ratite birds are of Mesozoic origin, based on both geochronological and phyletic grounds. The occurrence of monotremes in the early Paleocene (ca. 62 Ma) faunas of Patagonia and of ratites in late Eocene (ca. 41-37 m.y.) faunas of Seymour Island (Antarctic Peninsula) probably is an artifact of a much older and widespread Gondwana distribution prior to the Late Cretaceous Epoch. Except for South American microbiotheres being australidelphians, marsupial faunas of South America and Australia still are fundamentally disjunct. New material from Seymour Island (Microbiotheriidae) indicates the presence there of a derived taxon that resides in a group that is the sister taxon of most Australian marsupials. There is no compelling evidence that dispersal between Antarctica and Australia was as recent as ca. 41 Ma or later. In fact, the derived marsupial and placental land mammal fauna of Seymour Island shows its greatest affinity with Patagonian forms of Casamayoran age (ca. 51–54 m.y.). This suggests an earlier dispersal of more plesiomorphic marsupials from Patagonia to Australia via Antarctica, and vicariant disjunction subsequently. This is consistent with geophysical evidence that the South Tasman Rise was submerged by 64 Ma and with geological evidence that a shallow water marine barrier was present from then onward. The scenario above is consistent with molecular evidence suggesting that australidelphian bandicoots, dasyurids, and diprotodontians were distinct and present in Australia at least as early as the 63-Ma-old australidelphian microbiotheres and the ancient but not basal australidelphian,Andinodelphys, in the Tiupampa Fauna of Bolivia. Land mammal dispersal to Australia typically has been considered to be at a low level of probability (e.g., by sweepstakes dispersal). This study suggests that the marsupial colonizers of Australia included already recognizable members of the Peramelina, Dasyuromorphia, and Diprotodontia, at least, and entered via a filter route rather than by a sweepstakes dispersal.To whom correspondence should be addressed.     

First fossil Calopterygoidea (Odonata: Zygoptera) from Southeastern Asia: A new genus and species from the Paleogene of China

Sinocalopteryx shangyongensis nov. gen., nov. sp., the first fossil calopterygoid from eastern Asia, is described from the earliest Eocene of Southwest China. Although the new genus has the principle synapomorphies of Calopterygoidea, it possesses a unique structure (possible reversal) in the pattern of vein RP1/2.     

Fossil moonseeds from the Paleogene of West Gondwana (Patagonia,Argentina)

Premise of the Study

The fossil record is critical for testing biogeographic hypotheses. Menispermaceae (moonseeds) are a widespread family with a rich fossil record and alternative hypotheses related to their origin and diversification. The family is well‐represented in Cenozoic deposits of the northern hemisphere, but the record in the southern hemisphere is sparse. Filling in the southern record of moonseeds will improve our ability to evaluate alternative biogeographic hypotheses.

Methods

Fossils were collected from the Salamanca (early Paleocene, Danian) and the Huitrera (early Eocene, Ypresian) formations in Chubut Province, Argentina. We photographed them using light microscopy, epifluorescence, and scanning electron microscopy and compared the fossils with similar extant and fossil Menispermaceae using herbarium specimens and published literature.

Key Results

We describe fossil leaves and endocarps attributed to Menispermaceae from Argentinean Patagonia. The leaves are identified to the family, and the endocarps are further identified to the tribe Cissampelideae. The Salamancan endocarp is assigned to the extant genus Stephania. These fossils significantly expand the known range of Menispermaceae in South America, and they include the oldest (ca. 64 Ma) unequivocal evidence of the family worldwide.

Conclusions

Our findings highlight the importance of West Gondwana in the evolution of Menispermaceae during the Paleogene. Currently, the fossil record does not discern between a Laurasian or Gondwanan origin; however, it does demonstrate that Menispermaceae grew well outside the tropics by the early Paleocene. The endocarps’ affinity with Cissampelideae suggests that diversification of the family was well underway by the earliest Paleocene.     

Out of the Neotropics: newly discovered relictual species sheds light on the biogeographical history of spider ants (Leptomyrmex,Dolichoderinae, Formicidae)

Spider ants of the genus Leptomyrmex Mayr (Hymenoptera: Formicidae: Dolichoderinae) are conspicuous species of Australasian rainforests, with putative fossil relatives in the Neotropics and Europe. There is longstanding debate over the biogeographical history of the genus, with the Palaearctic and Neotropical regions proposed as alternate centres of origin. We propose a resolution of this debate with the recent discovery and analysis of an extant species from central Brazil, L. relictus sp.n. , which we describe from workers, males and brood. We sequence ten nuclear genes in the new species and in several Australian Leptomyrmex species, and append these data to a 54‐taxon, 10‐gene data matrix previously generated for the subfamily Dolichoderinae. We conduct phylogenetic and divergence dating analyses, and re‐evaluate the fossil record of the group. We recover Leptomyrmex relictus sp.n. as a member of the Leptomyrmex clade with high support. It is sister to the Australasian species, and the genus Leptomyrmex is, in turn, sister to a pair of Neotropical genera, Forelius and Dorymyrmex. We infer a Neotropical origin for the genus and estimate a mid‐Eocene (46 Ma, 95% CI 56 to 36 Ma) origin for the crown genus and an Oligocene origin for the Australasian clade (29 Ma, 95% CI 40 to 19 Ma). We confirm placement of the Dominican amber species ?L. neotropicus Baroni Urbani in the genus but reject a close relationship with the Palaearctic fossil taxa ?Leptomyrmula Emery and ?Usomyrma Dlussky, Radchenko & Dubovikoff, considering them incertae sedis in the subfamily (Dolichoderinae). In contrast to the mesophilic preferences of the Australasian species of Leptomyrmex, the new Brazilian species inhabits cerrado (dry savannah). Our results support a Neotropical origin for spider ants with dispersal to Australia. Rafting on west‐bound currents and/or a historical diversity imbalance between Australia and South America are proposed as alternate hypotheses to explain a pattern of biased E–W mid‐Tertiary dispersal for ants with austral distributions. This pattern is suggested by our results in conjunction with observations of other ant clades. Overall, our findings highlight the value of integrated taxonomy, critical interpretation of morphology, and a comparative phylogenetic framework when conducting palaeontological and biogeographical studies of insect species. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:6E9E6617‐6E53‐40B8‐82C7‐67F89A83C553 .     

Diversity of Menispermaceae from the Paleocene and Eocene of South China

We present here the earliest known Asian fossil records of the Menispermaceae based on fossil fruits from Paleocene and Eocene localities in South China. A new genus and species, Paleoorbicarpum parvum sp. nov., and two new species of Stephania Loureiro, S. ornamenta sp. nov. and S. geniculata sp. nov., are recognized from Paleocene deposits of the Sanshui Basin, Guangdong, and a new occurrence of the widespread Eocene species Stephania auriformis (Hollick) Han & Manchester is recognized from the Maoming Basin, Guangdong. The Paleocene Stephania specimens described here represent the earliest fossil endocarp record of the Menispermaceae in eastern Asia. This discovery shows that the moonseed family had arrived in tropical and humid South China by at least the middle Paleocene, which provides important evidence for the origin and phytogeographic history of the family.     

Missing fossils, molecular clocks, and the origin of the Melastomataceae

In a recent analysis of the historical biogeography of Melastomataceae, Renner, Clausing, and Meyer (2001; American Journal of Botany 88(7): 1290-1300) rejected the hypothesis of a Gondwana origin. Using a fossil-calibrated chloroplast DNA (ndhF) phylogeny, they placed the early diversification of Melastomataceae in Laurasia at the Paleocene/Eocene boundary (ca. 55 Ma) and suggested that long-distance oceanic dispersals in the Oligocene and Miocene (34 to 5 Ma) account for its range expansion into South America, Africa, and Madagascar. Their critical assumption-that oldest northern mid-latitude melastome fossils reflect tribal ages and their geographic origins-may be erroneous, however, because of the sparse fossil record in the tropics. We show that rates of synonymous nucleotide substitutions derived by the Renner et al. (2001) model are up to three times faster than most published rates. Under a Gondwana-origin model advocated here, which includes dispersals from Africa to Southeast Asia via the "Indian ark" and emphasizes filter rather than either sweepstakes dispersal or strict vicariance, rates of nucleotide substitution fall within the range of published rates. We suggest that biogeographic reconstructions need to consider the paucity of Gondwanan fossils and that frequently overlooked interplate dispersal routes provide alternatives to vicariance, boreotropical dispersal, and long-distance oceanic dispersal as explanations for the amphi-oceanic disjunctions of many tropical rain forest plants.     

First middle Miocene sivaladapid primate from Thailand

Sivaladapids are a group of Asian adapiform primates that were previously documented from deposits dating to the middle Eocene through the late Miocene in Pakistan, India, Myanmar, Thailand, and China. The group is notable for the persistence of three genera, Sivaladapis, Indraloris and Sinoadapis, into the late Miocene. In Thailand, sivaladapids were previously documented only from late Eocene deposits of the Krabi mine. Here, we describe the first Southeast Asian Miocene sivaladapid, Siamoadapis maemohensis gen. et sp. nov. from a 13.3 to 13.1 Ma lignite layer from the Mae Moh coal mine, Thailand. It differs from other Miocene sivaladapids by its distinctly smaller size and in features of the dentition. This discovery enhances the paleoecological diversity of the middle Miocene primate fauna of Thailand, which now includes sivaladapids, a loris, tarsiids, and hominoids. In this respect, the fossil primate community from the middle Miocene of Thailand is similar in its composition to roughly contemporaneous assemblages from southern China, India, and Pakistan. However, the Thai fossils represent a distinct genus, suggesting a different biogeographic province with distinctive paleoenvironments.     

Phylogenetic relationships,biogeography and diversification of Coenonymphina butterflies (Nymphalidae: Satyrinae): intercontinental dispersal of a southern Gondwanan group?

The origins, evolutionary history and diversification of the Australian butterfly fauna are poorly known and uncertain. Two competing hypotheses have been proposed to explain the occurrence of butterflies on this isolated continental landmass. The common view is that all Australian butterflies entered the continent relatively recently from the northern hemisphere via Southeast Asia and/or mainland New Guinea (i.e. northern dispersal origin hypothesis). The alternative view is that part or all of the Australian butterfly fauna ultimately evolved in remnant or Southern Gondwana when Australia was connected to South America through Antarctica (i.e. Southern Gondwanan origin hypothesis). However, robust phylogenies with strong support for monophyly are lacking for the majority of Australian endemic butterfly lineages, thereby precluding determination of their systematic relationships and hence their geographic origins. Here, we use molecular data to reconstruct phylogenetic relationships of the globally distributed butterfly subtribe Coenonymphina (Satyrinae: Satyrini). This group represents a major component of the butterfly fauna of the wider Australasian region, with 19 genera and 71 species endemic to the region. Dating estimates extrapolated from secondary calibration sources indicate that the subtribe arose c . 48 Ma (95% credibility interval, 52–42 Ma), and the crown group first diverged in the Eocene (c . 44 Ma, 95% credibility interval 51–37 Ma). Rapid speciation events subsequently followed around the Eocence–Oligocene boundary, resulting in a near‐hard polytomy comprising short basal branches with nodes that are difficult to resolve. Based on strongly supported phylogenetic relationships and estimates of divergence times, we conclude that the group probably had its origin in the fragment of Southern Gondwana consisting of Australia, Antarctica and South America. However, we are unable to rule out the northern dispersal scenario, particularly as Coenonymphina are closely related to a set of predominantly Asian lineages. Dispersal and extinction events following the final break‐up of Gondwana have played a pivotal role in shaping the extant distributions of the group.     

Northern Hemisphere megafossil of Dacrycarpus (Podocarpaceae) from the Miocene of South China and its evolutionary and paleoecological implications

The modern genus Dacrycarpus (Endl.) de Laub. of the family Podocarpaceae, containing nine species, is mainly distributed in tropical mountain rainforests of the southwestern Pacific region, ranging from New Zealand to low‐latitude Asia. This genus has abundant fossil records in both hemispheres, but all the known megafossils were limited to Australasia and South America. Here we report on Dacrycarpus guipingensis sp. nov. from the Miocene Erzitang Formation of Guangxi, South China. This is the first megafossil of Dacrycarpus in the Northern Hemisphere. The new species is represented by mummified dimorphic foliage, ovuliferous shoots, and a male cone with in situ pollen. It resembles the extant Dacrycarpus imbricatus (Blume) de Laub., which is common in rainforests from southern China and northern Myanmar to Fiji. This paper presents the first data on the anatomical structure of seed cone and exine ultrastructure of Dacrycarpus in situ pollen grains from a fossil material by using computed tomography scanning and ultrathin sectioning. For comparative purpose, data on the pollen morphology and ultrastructure were obtained for modern D. imbricatus for the first time. The D. guipingensis fossils strongly suggest the Miocene arrival of Dacrycarpus in Asia from the Southern Hemisphere. Based on the modern ecological niche and related fossil elements, this fossil locality was probably covered by conifer–broad‐leaved mountain rainforests during the Miocene.     

The diversification of the northern temperate woody flora – A case study of the Elm family (Ulmaceae) based on phylogenomic and paleobotanical evidence

Ulmaceae is a woody family widespread in northern temperate forests. Despite the ecological importance of this family, its phylogeny and biogeographic history are poorly understood. In this study, we reconstruct phylogenetic relationships within the family and infer spatio-temporal diversification patterns based on chloroplast genome (complete cpDNA) and nuclear ribosomal DNA sequences (nrDNA). The seven Ulmaceae genera are resolved in two main clades (temperate vs. tropical) by both cpDNA and nrDNA sequences. The temperate clade includes four genera, Hemiptelea, Zelkova, Planera, and Ulmus. The relationships among Planera and other genera are controversial because of inconsistent topologies between plastid and nuclear data. The tropical clade includes three genera ((Ampelocera, Phyllostylon), Holoptelea). Molecular dating and diversification analyses show that Ulmaceae originated in the Early Cretaceous (ca. 110–125 Ma) with the main lineages establishing from the Late Cretaceous to the early Eocene. The diversification rate slowed during the middle to the late Paleogene (ca. 23–45 Ma), followed by a rapid diversification of the East Asian temperate group in the Neogene, congruent with a global cooling event. The ancestral state optimization analysis suggests an East Asian origin of the temperate Ulmaceae clade during the Paleocene, which is consistent with the fossil record. Both phylogenomic and fossil evidence support East Asia as a center of origin and diversification for the temperate woody lineages.     

Cones, Seeds, and Foliage of Tetraclinis Salicornioides (Cupressaceae) from the Oligocene and Miocene of Western North America: A Geographic Extension of the European Tertiary Species

The cupressaceous genus Tetraclinis is recognized from the Oligocene and Miocene of western North America on the basis of co-occurring seed cones, seeds, and foliage branches. Morphological and anatomical comparisons with the two previously recognized European Tertiary species indicate that the North American specimens are morphologically inseparable from Tetraclinis salicornioides (Unger) Kvacek. The North American taxon is treated as a new variety, T. salicornioides (Unger) Kvacek var. praedecurrens (Knowlton) comb. et stat. nov., and is distinguished from the European representatives, T. salicornioides (Unger) Kvacek var. salicornioides, by slight anatomical differences in the leaf epidermis. Although cones and seeds of the fossil species are closely similar to those of extant Tetraclinis articulata, the foliage is more "spreading," composed of flattened segments with fused facial and lateral leaves that are apparently adaptive for a more mesic climate. The recognition of T. salicornioides in western North America along with the absence of Tetraclinis in the fossil and recent flora of eastern Asia provide evidence for communication of the species across the North Atlantic during the early or middle Tertiary.     

South American palaeobotany and the origins of neotropical rainforests

Extant neotropical rainforest biomes are characterized by a high diversity and abundance of angiosperm trees and vines, high proportions of entire-margined leaves, high proportions of large leaves (larger than 4500 mm2), high abundance of drip tips and a suite of characteristic dominant families: Sapotaceae, Lauraceae, Leguminosae (Fabaceae), Melastomataceae and Palmae (Arecaceae). Our aim is to define parameters of extant rainforests that will allow their recognition in the fossil record of South America and to evaluate all known South American plant fossil assemblages for first evidence and continued presence of those parameters. We ask when did these critical rainforest characters arise? When did vegetative parameters reach the level of abundance that we see in neotropical forests? Also, when do specific lineages become common in neotropical forests? Our review indicates that evidence of neotropical rainforest is exceedingly rare and equivocal before the Palaeocene. Even in the Palaeocene, the only evidence for tropical rainforest in South America is the appearance of moderately high pollen diversity. By contrast, North American sites provide evidence that rainforest leaf physiognomy was established early in the Palaeocene. By the Eocene in South America, several lines of evidence suggest that neotropical rainforests were diverse, physiognomically recognizable as rainforest and taxonomically allied to modern neotropical rainforests. A mismatch of evidence regarding the age of origin between sites of palaeobotanical high diversity and sites of predicted tropical climates should be reconciled with intensified collecting efforts in South America. We identify several lines of promising research that will help to coalesce previously disparate approaches to the origin, longevity and maintenance of high diversity floras of South America.     

A phylogeny of frugivorous hornbills linked to the evolution of Indian plants within Asian rainforests

Understanding the origin and radiation of modern Asian hornbills and the influential ecological roles they play as seed dispersal agents within Asian rainforests should help reveal the evolution of these roles. We constructed a dated phylogeny of hornbills using mitochondrial DNA sequences of the cytochrome b gene and discovered that all clades leading to frugivorous hornbills originated in the mid-Eocene ～48 Ma. This 'explosive' radiation coincided with a remarkable floral invasion of Asian rainforests from the Indian microcontinent. Analysis of phylogenetic data, in conjunction with palaeontological events, suggests that the invasion of distinctive flora comprised two waves, one during the mid-Eocene, when India was offshore of the Sunda Shelf, and the other late Eocene, when India collided with the Asian mainland. We propose that frugivorous vertebrates, such as hornbills, were present during the first wave and assisted rapid colonization of the Asian flora.