More DNA support for a Cetacea/Hippopotamidae clade: the blood-clotting protein gene gamma-fibrinogen

Recent phylogenetic analyses of DNA sequences suggest that cetaceans (whales) and hippopotamid artiodactyls (hippos) are extant sister taxa. Consequently, the shared aquatic specializations of these taxa may be synapomorphies. This molecular view is contradicted by paleontological data that overwhelmingly support a monophyletic Artiodactyla (even-toed ungulates) and a close relationship between Cetacea and extinct mesonychian ungulates. According to the fossil evidence, molecular, behavioral, and anatomical resemblances between hippos and whales are interpreted as convergences or primitive retentions. In this report, competing interpretations of whale origins are tested through phylogenetic analyses of the blood-clotting protein gene gamma- fibrinogen from cetaceans, artiodactyls, perissodactyls (odd-toed ungulates), and carnivores (cats, dogs, and kin). In combination with published DNA sequences, the gamma-fibrinogen data unambiguously support a hippo/whale clade and are inconsistent with the paleontological perspective. If the phylogeny favored by fossil evidence is accepted, the convergence at the DNA level between Cetacea and Hippopotamidae is remarkable in its distribution across three genetic loci: gamma-fibrinogen, the linked milk casein genes, and mitochondrial cytochrome b.      

Phylogenetic Relationships of Extinct Cetartiodactyls: Results of Simultaneous Analyses of Molecular, Morphological, and Stratigraphic Data

Although some recent morphological and molecular studies agree that Cetacea is closely related to Hippopotamidae, there is little consensus on the phylogeny within Cetartiodactyla. We addressed this problem by conducting two analyses: (1) a simultaneous cladistic analysis of intrinsic data (morphology and molecules) and (2) a stratocladistic analysis, which included morphological, molecular, and stratigraphic data. Unlike previous simultaneous analyses, we had the opportunity to include data from the recently described hindlimbs of protocetid and pakicetid cetaceans. Our intrinsic dataset includes 73 taxa scored for 8,229 informative characters, of which 208 are morphological and 8,021 molecular. Both analyses supported the exclusion of Mesonychia from Cetartiodactyla and a close phylogenetic relationship between Hippopotamidae and Cetacea. Many polytomies in the strict consensus of the most parsimonious trees for the intrinsic dataset can be attributed to differing positions for Raoellidae, which in some trees is the sister-group to Cetacea. Pruning Raoellidae and 18 other taxa from all most parsimonious produced a fully resolved agreement subtree, which indicates that the Old World taxa Cebochoerus and Mixtotherium are successive stem taxa to Whippomorpha (i.e., Cetacea + Hippopotamidae). The main result of adding stratigraphic information to the intrinsic dataset was that we found fewer most parsimonious trees, which in most respects were congruent with a subset of the shortest trees for the intrinsic dataset. Our stratocladistic analysis supports species of Diacodexis as the most basal cetartiodactyls, a clade of suiform cetartiodactyls, a monophyletic Tylopoda that includes Protoceratidae, and a monophyletic Carnivora. We were unable to identify any pre-Miocene stem taxa to Hippopotamidae, thus its ghost lineage is still 39 million years long. The relatively low Bremer support for many nodes in our trees indicates that our phylogenetic hypotheses should be subjected to further testing.     

Systematics and evolution of the Pan‐Alcidae (Aves,Charadriiformes)

Puffins, auks and their allies in the wing‐propelled diving seabird clade Pan‐Alcidae (Charadriiformes) have been proposed to be key pelagic indicators of faunal shifts in Northern Hemisphere oceans. However, most previous phylogenetic analyses of the clade have focused only on the 23 extant alcid species. Here we undertake a combined phylogenetic analysis of all previously published molecular sequence data (～ 12 kb) and morphological data (n = 353 characters) with dense species level sampling that also includes 28 extinct taxa. We present a new estimate of the patterns of diversification in the clade based on divergence time estimates that include a previously vetted set of twelve fossil calibrations. The resultant time trees are also used in the evaluation of previously hypothesized paleoclimatic drivers of pan‐alcid evolution. Our divergence dating results estimate the split of Alcidae from its sister taxon Stercorariidae during the late Eocene (～ 35 Ma), an evolutionary hypothesis for clade origination that agrees with the fossil record and that does not require the inference of extensive ghost lineages. The extant dovekie Alle alle is identified as the sole extant member of a clade including four extinct Miocene species. Furthermore, whereas an Uria + Alle clade has been previously recovered from molecular analyses, the extinct diversity of closely related Miocepphus species yields morphological support for this clade. Our results suggest that extant alcid diversity is a function of Miocene diversification and differential extinction at the Pliocene–Pleistocene boundary. The relative timing of the Middle Miocene climatic optimum and the Pliocene–Pleistocene climatic transition and major diversification and extinction events in Pan‐Alcidae, respectively, are consistent with a potential link between major paleoclimatic events and pan‐alcid cladogenesis.     

Stability of cladistic relationships between Cetacea and higher-level artiodactyl taxa

Over the past 10 years, the phylogenetic relationships among higher-level artiodactyl taxa have been examined with multiple data sets. Many of these data sets suggest that Artiodactyla (even-toed ungulates) is paraphyletic and that Cetacea (whales) represents a highly derived "artiodactyl" subgroup. In this report, phylogenetic relationships between Cetacea and artiodactyls are tested with a combination of 15 published data sets plus new DNA sequence data from two nuclear loci, interphotoreceptor retinoid-binding protein (IRBP) and von Willebrand factor (vWF). The addition of the IRBP and vWF character sets disrupts none of the relationships supported by recent cladistic analyses of the other 15 data sets. Simultaneous analyses support three critical clades: (Cetacea + Hippopotamidae), (Cetacea + Hippopotamidae + Ruminantia), and (Cetacea + Hippopotamidae + Ruminantia + Suina). Perturbations of the combined matrix show that the above clades are stable to a variety of disturbances. A chronicle of phylogenetic results over the past 3 years suggests that cladistic relationships between Cetacea and artiodactyls have been stable to increased taxonomic sampling and to the addition of more than 1,400 informative characters from 15 data sets.     

Scolecophidia (Serpentes) of the Late Oligocene and Early Miocene,North America,and a fossil history overview

An abundant fossil record of the snake clade Scolecophidia exists in Europe; however, the minute snake is noticeably absent in reports about the North American Paleogene and Neogene. Presented here are four localities from Florida, USA, that contain scolecophidian remains older than the Pleistocene: Thomas Farm (late Early Miocene, Hemingfordian Land Mammal Age, LMA), Live Oak (Oligocene-Miocene transition, latest Arikareean LMA), White Springs 3B (late Arikareean LMA), and Brooksville 2 (Late Oligocene, middle Arikareean LMA). These remains extend their known existence by about 26 m.y. and are now the oldest reported scolecophidian remains in North America. Molecular evidence on extant scolecophidians concludes that these tiny snakes have a Gondwanan origin. Interestingly, the oldest record of a scolecophidian is from Europe (Belgium) and dates back to the middle Paleocene (MP 1–5). The earliest African record of the snake clade comes from the Paleocene-Eocene boundary in Morocco. The clade is apparently absent from Europe and Middle East deposits dating from the latest Eocene through to the latest Oligocene (MP 19–30) and to the Early Miocene (MN 4). A portion of this time is known as the booid ‘Dark Period’ which represents an apparent response to global aridization and cooling. Scolecophidians appear to re-emerge into the southern Eurasian record in the Early Miocene (MN 4) and become widely dispersed throughout Europe and Middle East. The fossil record of these minute snakes is largely absent in southern Asia and South America. It is possible that the current lack of a decent fossil scolecophidian record outside of Europe and Middle East is due mainly to a bias in the methodology to recover fossils; wet sieving sediments through < 1.0 mm mesh is needed to recover the minuscule vertebrae.     

Human evolution at the Matuyama‐Brunhes boundary

The cranial morphology of fossil hominids between the end of the Early Pleistocene and the beginning of the Middle Pleistocene provides crucial evidence to understand the distribution in time and space of the genus Homo. This evidence is critical for evaluating the competing models regarding diversity within our genus. The debate focuses on two alternative hypotheses, one basically anagenetic and the other cladogenetic. The first suggests that morphological change is so diffused, slow, and steady that it is meaningless to apply species names to segments of a single lineage. The second is that the morphological variation observed in the fossil record can best be described as a number of distinct species that are not connected in a linear ancestor‐descendant sequence. Today much more fossil evidence is available than was in the past to test these alternative hypotheses, as well as intermediate variants. Special attention must be paid to Africa because this is the most probable continental homeland for both the origin of the genus Homo (around 2.5–2 Ma), 1 as well as the site, two million or so years later, of the emergence of the species H. sapiens. 2 However, the African fossil record is very poorly represented between 1 Ma and 600 ka. Europe furnishes recent discoveries in this time range around the Matuyama‐Brunhes chron boundary (780,000 years ago), a period for which, at present, we have no noteworthy fossil evidence in Africa or the Levant. Two penecontemporaneous sources of European fossil evidence, the Ceprano calvaria (Italy) 3 and the TD6 fossil assemblage of Atapuerca (Spain) 4 are thus of great interest for testing hypotheses about human evolution in the fundamental time span bracketed between the late Early and the Middle Pleistocene. This paper is based on a phenetic approach to cranial variation aimed at reviewing the Early‐to‐Middle Pleistocene trajectories of human evolution. The focus of the paper is on neither the origin nor the end of the story of the genus Homo, but rather its chronological and phylogenetic core. Elucidation of the evolutionary events that happened around 780 ka during the transition from the Early to Middle Pleistocene is one of the new frontiers for human paleontology, and is critical for understanding the processes that ultimately led to the origin of H. sapiens.     

Phylogenomic analyses and improved resolution of Cetartiodactyla

The remarkable antiquity, diversity, and significance in the ecology and evolution of Cetartiodactyla have inspired numerous attempts to resolve their phylogenetic relationships. However, previous analyses based on limited samples of nuclear genes or mitochondrial DNA sequences have generated results that were either inconsistent with one another, weakly supported, or highly sensitive to analytical conditions. Here, we present strongly supported results based upon over 1.4 Mb of an aligned DNA sequence matrix from 110 single-copy nuclear protein-coding genes of 21 Cetartiodactyla species, which represent major Cetartiodactyla lineages, and three species of Perissodactyla and Carnivora as outgroups. Phylogenetic analysis of this newly developed genomic sequence data using a codon-based model and recently developed models of the rate autocorrelation resolved the phylogenetic relationships of the major cetartiodactylan lineages and of those lineages with a high degree of confidence. Cetacea was found to nest within Artiodactyla as the sister group of Hippopotamidae, and Tylopoda was corroborated as the sole base clade of Cetartiodactyla. Within Cetacea, the monophyletic status of Odontoceti relative to Mysticeti, the basal position of Physeteroidea in Odontoceti, the non-monophyly of the river dolphins, and the sister relationship between Delphinidae and Monodontidae + Phocoenidae were strongly supported. In particular, the groups of Tursiops (bottlenose dolphins) and Stenella (spotted dolphins) were validated as unnatural groups. Additionally, a very narrow time frame of ∼3 My (million years) was found for the rapid diversification of delphinids in the late Miocene, which made it difficult to resolve the phylogenetic relationships within the Delphinidae, especially for previous studies with limited data sets. The present study provides a statistically well-supported phylogenetic framework of Cetartiodactyla, which represents an important step toward ending some of the often-heated, century-long debate on their evolution.     

Impact of increased character sampling on the phylogeny of Cetartiodactyla (Mammalia): combined analysis including fossils

The phylogenetic position of Cetacea (whales, dolphins and porpoises) is an important exemplar problem for combined data parsimony analyses because the clade is ancient and includes many well‐known and relatively complete fossil species. We combined data for 71 terminal taxa (43 extinct/28 extant) to test where Cetacea fits within Cetartiodactyla, and where various fossil hoofed mammals (e.g., ?entelodonts, “?anthracotheriids” and ?mesonychians) are positioned. We scored 635 phenotypic characters (osteology, dentition, soft tissue, behavior), approximately three times the number of characters in the last major analysis of this clade, and combined these with > 40 000 molecular characters, including new data from 10 genes. The analysis supported a topology consistent with the majority of recently published molecular studies. Cetacea was the extant sister taxon of Hippopotamidae, followed successively by Ruminantia, Suina and Camelidae. Several extinct taxa were phylogenetically unstable, upsetting resolution of the strict consensus and limiting branch support, but the positions of several key fossils were consistently resolved. The wholly extinct ?Mesonychia was more closely related to Cetacea than was any “artiodactylan.”“?Anthracotheriids” were paraphyletic, and, with the exception of one species, were more closely related to Hippopotamidae than to any other living taxon. The total evidence analysis overturned a highly nested position for Moschus supported by molecular data alone. The character partition that could be scored for the fossil taxa (osteological and dental characters) included more informative characters than most molecular partitions in our analysis, and had the fewest missing data. The osteological–dental data alone, however, did not support inclusion of cetaceans within crown “Artiodactyla.” Recently discovered ankle bones from fossil whales reinforced the monophyly of Cetartiodactyla but provided no particular evidence of derived similarities between hippopotamids and fossil cetaceans that were not shared with other “artiodactylans”. © The Willi Hennig Society 2007.     

Enamel microstructure evolution in anthracotheres (Mammalia,Cetartiodactyla) and new insights on hippopotamoid phylogeny

Investigations on enamel microstructure provided new data for the debate on hippopotamid origin. Observations indicated a diversity of patterns relevant to phylogenetic inferences. Within Hippopotamoidea, the distribution of these patterns seems to be in favour of a hippopotamid origin within the Palaeogene African anthracotheres. Enamel microcharacters therefore prove to be particularly relevant for future phylogenetic analysis of the superfamily, and have implications for our understanding of ecological transitions within hippopotamoids at the end of the Miocene. Indeed, unlike equids or bovids, which developed grass feeding thanks to their hypsodont molars, hippopotamoids may have had another way to exploit this resource. The combination of inter‐row sheets, which appeared early in the evolutionary history of the group, and the increased thickness of radial enamel could have eased the consumption of highly abrasive graminoids. © 2014 The Linnean Society of London     

Tragelaphus nakuae: evolutionary change,biochronology, and turnover in the African Plio‐Pleistocene

Fossil Bovidae constitute one of the most significant proxy records for evolutionary and palaeoecological change in Africa. Tragelaphus nakuae is a regularly encountered antelope in the East African Plio‐Pleistocene, and is a common component of hominin faunas. As previously understood, this species ranged for almost 2 million years, encompassed a large range of morphological variation, exhibited relative stasis in the face of environmental perturbations, and left no known living descendants. I here review and revise the fossil record of this tragelaphin bovid, finding that specimens older than ～2.8 Mya and previously attributed to T. nakuae or a close form are in fact referable to a distinct, but ancestral, species. This new interpretation adds these fossil tragelaphins to the body of evidence supporting major faunal turnover occurring around 2.8 Mya in concert with global climatic change. I also document morphological changes that occur through the duration of T. nakuae, particularly after 2.3 Mya. These taxonomic revisions allow for refined biochronological estimates for several East African Plio‐Pleistocene sites and specimen assemblages of uncertain age. A phylogenetic analysis suggests that the T. nakuae lineage is related to the extant bongo (Tragelaphus eurycerus), relating this living but enigmatic forest antelope to the fossil record. One resulting palaeoecological hypothesis is that the bongo's modern fragmented range represents the relicts of a much more widely distributed late Pliocene African forest belt. This study highlights the importance of specimen‐based approaches for elucidating the pattern and timing of major evolutionary events. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162 , 699–711.     

Tropical forests and the genus Homo

Tropical forests constitute some of the most diverse and complex terrestrial ecosystems on the planet. From the Miocene onward, they have acted as a backdrop to the ongoing evolution of our closest living relatives, the great apes, and provided the cradle for the emergence of early hominins, who retained arboreal physiological adaptations at least into the Late Pliocene. There also now exists growing evidence, from the Late Pleistocene onward, for tool‐assisted intensification of tropical forest occupation and resource extraction by our own species, Homo sapiens. However, between the Late Pliocene and Late Pleistocene there is an apparent gap in clear and convincing evidence for the use of tropical forests by hominins, including early members of our own genus. In discussions of Late Pliocene and Early Pleistocene hominin evolution, including the emergence and later expansion of Homo species across the globe, tropical forest adaptations tend to be eclipsed by open, savanna environments. Thus far, it is not clear whether this Early‐Middle Pleistocene lacuna in Homo‐rainforest interaction is real and representative of an adaptive shift with the emergence of our species or if it is simply reflective of preservation bias.     

A revision of the fossil Canidae (Mammalia) of north‐western Africa

Abstract: The fossil record of the Canidae in North‐western Africa begins near the Miocene–Pliocene boundary with a form close to Nyctereutes, a genus best known in the late Pliocene of Ahl al Oughlam. This site yields two other canids. Vulpes hassani sp. nov. is a small fox, probably ancestral to the modern V. rueppelli, recorded from the Middle Pleistocene onwards. Lupulella paralius sp. nov. is a primitive jackal that probably belongs to the clade of modern African jackals. In the middle Pleistocene, the most common canid is Lupulella mohibi sp. nov., remarkable by its Nyctereutes‐like dentition and primitive skull‐features. These are all endemic forms, but V. vulpes and C. aureus, of northern origin, appear in the course of the middle Pleistocene. Lycaon has a sparse record in the middle and late Pleistocene.     

Major Radiations in the Evolution of Caviid Rodents: Reconciling Fossils,Ghost Lineages,and Relaxed Molecular Clocks

Background

Caviidae is a diverse group of caviomorph rodents that is broadly distributed in South America and is divided into three highly divergent extant lineages: Caviinae (cavies), Dolichotinae (maras), and Hydrochoerinae (capybaras). The fossil record of Caviidae is only abundant and diverse since the late Miocene. Caviids belongs to Cavioidea sensu stricto (Cavioidea s.s.) that also includes a diverse assemblage of extinct taxa recorded from the late Oligocene to the middle Miocene of South America (“eocardiids”).

Results

A phylogenetic analysis combining morphological and molecular data is presented here, evaluating the time of diversification of selected nodes based on the calibration of phylogenetic trees with fossil taxa and the use of relaxed molecular clocks. This analysis reveals three major phases of diversification in the evolutionary history of Cavioidea s.s. The first two phases involve two successive radiations of extinct lineages that occurred during the late Oligocene and the early Miocene. The third phase consists of the diversification of Caviidae. The initial split of caviids is dated as middle Miocene by the fossil record. This date falls within the 95% higher probability distribution estimated by the relaxed Bayesian molecular clock, although the mean age estimate ages are 3.5 to 7 Myr older. The initial split of caviids is followed by an obscure period of poor fossil record (refered here as the Mayoan gap) and then by the appearance of highly differentiated modern lineages of caviids, which evidentially occurred at the late Miocene as indicated by both the fossil record and molecular clock estimates.

Conclusions

The integrated approach used here allowed us identifying the agreements and discrepancies of the fossil record and molecular clock estimates on the timing of the major events in cavioid evolution, revealing evolutionary patterns that would not have been possible to gather using only molecular or paleontological data alone.     

India at the cross-roads of human evolution

The Indian palaeoanthropological record, although patchy at the moment, is improving rapidly with every new find. This broad review attempts to provide an account of (a) the Late Miocene fossil apes and their gradual disappearance due to ecological shift from forest dominated to grassland dominated ecosystem around 9-8 Ma ago, (b) the Pliocene immigration/evolution of possible hominids and associated fauna, (c) the Pleistocene record of fossil hominins, associated fauna and artifacts, and (d) the Holocene time of permanent settlements and the genetic data from various human cultural groups within India. Around 13 Ma ago (late Middle Miocene) Siwalik forests saw the emergence of an orangutan-like primate Sivapithecus. By 8 Ma, this genus disappeared from the Siwalik region as its habitat started shrinking due to increased aridity influenced by global cooling and monsoon intensification. A contemporary and a close relative of Sivapithecus, Gigantopithecus (Indopithecus), the largest ape that ever-lived, made its first appearance at around 9 Ma. Other smaller primates that were pene-contemporaneous with these apes were Pliopithecus (Dendropithecus), Indraloris, Sivaladapis and Palaeotupia. The Late Pliocene and Early Pleistocene witnessed northern hemisphere glaciations, followed by the spread of arid conditions on a global scale, setting the stage for hominids to explore “Savanahastan”. With the prominent expansion of grassland environments from East Africa to China and Indonesia in the Pliocene, monkeys and baboons dispersed into the Indian subcontinent from Africa along with other mammals. Though debated, there are several claims of the presence of early hominins in this part of the world during the Late Pliocene, based primarily on the recovery of Palaeolithic tools. Fossils of our own ancestor and one of the first globe-trotters, early Homo erectus, has been documented from the Early Pleistocene of East Africa, Western Asia and Southeast Asia, thus indirectly pointing towards Indian subcontinent as a possible migration corridor between these regions. The only definite pre-Homo sapiens fossil hominin remains come from the Central Narmada Valley and are thought to be of Middle to late Pleistocene age, and the cranium has been shown to be closely linked to archaic Homo sapiens/H. heidelbergensis of Europe. Around ∼74,000 yrs ago, a super volcanic eruption in Sumatra caused the deposition of Youngest Toba Tephra, that covered large parts of the Indian peninsula. Just around this time anatomically-and-behaviorally modern humans or Homo sapiens possibly arrived into India as evidenced by the so called Middle and Upper Palaeolithic assemblages and associated symbolic evidence. The available genetic data reveals that the gene pool to which modern Indians races belong was extremely diverse and had variable mixed links with both European and Asian populations.     

Pleistocene Chinese cave hyenas and the recent Eurasian history of the spotted hyena,Crocuta crocuta

The living hyena species (spotted, brown, striped and aardwolf) are remnants of a formerly diverse group of more than 80 fossil species, which peaked in diversity in the Late Miocene (about 7–8 Ma). The fossil history indicates an African origin, and morphological and ancient DNA data have confirmed that living spotted hyenas (Crocuta crocuta) of Africa were closely related to extinct Late Pleistocene cave hyenas from Europe and Asia. The current model used to explain the origins of Eurasian cave hyena populations invokes multiple migrations out of Africa between 3.5–0.35 Ma. We used mitochondrial DNA sequences from radiocarbon‐dated Chinese Pleistocene hyena specimens to examine the origin of Asian populations, and temporally calibrate the evolutionary history of spotted hyenas. Our results support a far more recent evolutionary timescale (430–163 kya) and suggest that extinct and living spotted hyena populations originated from a widespread Eurasian population in the Late Pleistocene, which was only subsequently restricted to Africa. We developed statistical tests of the contrasting population models and their fit to the fossil record. Coalescent simulations and Bayes Factor analysis support the new radiocarbon‐calibrated timescale and Eurasian origins model. The new Eurasian biogeographic scenario proposed for the hyena emphasizes the role of the vast steppe grasslands of Eurasia in contrast to models only involving Africa. The new methodology for combining genetic and geological data to test contrasting models of population history will be useful for a wide range of taxa where ancient and historic genetic data are available.     

The oldest marine vertebrate fossil from the volcanic island of Iceland: a partial right whale skull from the high latitude Pliocene Tjörnes Formation

Extant baleen whales (Cetacea, Mysticeti) are a disparate and species‐rich group, but little is known about their fossil record in the northernmost Atlantic Ocean, a region that supports considerable extant cetacean diversity. Iceland's geographical setting, dividing North Atlantic and Arctic waters, renders it ideally situated to shed light on cetacean evolution in this region. However, as a volcanic island, Iceland exhibits very little marine sedimentary exposure, and fossil whales from Iceland older than the late Pleistocene are virtually unknown. Here, we present the first fossil whale found in situ from the Pliocene Tjörnes Formation (c. 4.5 Ma), Iceland's only substantial marine sedimentary outcrop. The specimen is diagnosed as a partial skull from a large right whale (Mysticeti, Balaenidae). This discovery highlights the Tjörnes Formation as a potentially productive fossil vertebrate locality. Additionally, this find indicates that right whales (Eubalaena) and bowhead whales (Balaena) were sympatric, with broadly overlapping latitudinal ranges in the Pliocene, in contrast to the modern latitudinal separation of their living counterparts.     

Pliocene–Pleistocene ecological niche evolution shapes the phylogeography of a Mediterranean plant group

Estimating species ability to adapt to environmental changes is crucial to understand their past and future response to climate change. The Mediterranean Basin has experienced remarkable climatic changes since the Miocene, which have greatly influenced the evolution of the Mediterranean flora. Here, we examine the evolutionary history and biogeographic patterns of two sedge sister species (Carex, Cyperaceae) restricted to the western Mediterranean Basin, but with Pliocene fossil record in central Europe. In particular, we estimated the evolution of climatic niches through time and its influence in lineage differentiation. We carried out a dated phylogenetic–phylogeographic study based on seven DNA regions (nDNA and ptDNA) and fingerprinting data (AFLPs), and modelled ecological niches and species distributions for the Pliocene, Pleistocene and present. Phylogenetic and divergence time analyses revealed that both species form a monophyletic lineage originated in the late Pliocene–early Pleistocene. We detected clear genetic differentiation between both species with distinct genetic clusters in disjunct areas, indicating the predominant role of geographic barriers limiting gene flow. We found a remarkable shift in the climatic requirements between Pliocene and extant populations, although the niche seems to have been relatively conserved since the Pleistocene split of both species. This study highlights how an integrative approach combining different data sources and analyses, including fossils, allows solid and robust inferences about the evolutionary history of a plant group since the Pliocene.     

Timing of the evolutionary history of Corallinaceae (Corallinales,Rhodophyta)

The temporal dimension of the most recent Corallinaceae (order Corallinales) phylogeny was presented here, based on first occurrence time estimates from the fossil record. Calibration of the molecular clock of the genetic marker SSU entailed a separation of Corallinales from Hapalidiales in the Albian (Early Cretaceous ~105 mya). Neither the calibration nor the fossil record resolved the succession of appearance of the first three emerging subfamilies: Mastophoroideae, Corallinoideae, and Neogoniolithoideae. The development of the tetra/bisporangial conceptacle roofs by filaments surrounding and interspersed among the sporangial initials was an evolutionary novelty emerging at the Cretaceous–Paleogene boundary (~66 mya). This novelty was shared by the subfamilies Hydrolithoideae, Metagoniolithoideae, and Lithophylloideae, which diverged in the early Paleogene. Subclades within the Metagoniolithoideae and Lithophylloideae diversified in the late Oligocene–middle Miocene (~28–12 mya). The most common reef corallinaceans (Hydrolithon, Porolithon, Harveylithon, “Pneophyllum” conicum, and subclades within Lithophylloideae) appeared in this interval in the Indo‐Australian Archipelago.     

A Paleogeographic Overview of Tropical Fossil Sloths: Towards an Understanding of the Origin of Extant Suspensory Sloths?

Modern sloths are among the more characteristic mammals of South and Central American faunas. Recent discovery in four Paleogene, 22 Neogene, and dozens of Pleistocene fossiliferous localities in the tropics has revealed an unexpected paleobioversity constituted by some 81 fossil sloth species. Probably originating in southern South America near the Eocene/Oligocene transition, sloths were represented in the tropics during the late Oligocene by Pseudoglyptodon, Mylodontidae, and Megalonychidae. The latter occupied the West Indies between at least the late early Miocene and late Pleistocene, and two mylodontid clades, Octodontobradyinae and Urumacotheriinae, were characteristic of Amazonian localities from the Colhuehuapian and the Laventan periods, respectively, until the end of the Miocene. Megatheriinae and Nothrotheriidae appeared during the middle Miocene, colonizing the tropics and then North America, where Mylodontidae and Megalonychidae had already been present since the early late Miocene. Nothrotheriids are more abundant and diversified during the late Miocene in the tropics than in southern South America. Remains closely related to either of the modern sloths are absent from the fossil record, including those in the tropics. The characteristic suspensory posture of Bradypus and Choloepus appeared independently and likely after the Miocene epoch, and thus well after the hypothesized split suggested by molecular studies of the respective clades of these genera. Given their current widespread distribution in and reliance on the tropics, prospecting efforts for the direct fossil kin of suspensory sloths should concentrate on deposits in the Amazonian region, as this area has shown promise in producing fossil sloths.