The early Eocene birds of the Messel fossil site: a 48 million‐year‐old bird community adds a temporal perspective to the evolution of tropical avifaunas

Birds play an important role in studies addressing the diversity and species richness of tropical ecosystems, but because of the poor avian fossil record in all extant tropical regions, a temporal perspective is mainly provided by divergence dates derived from calibrated molecular analyses. Tropical ecosystems were, however, widespread in the Northern Hemisphere during the early Cenozoic, and the early Eocene German fossil site Messel in particular has yielded a rich avian fossil record. The Messel avifauna is characterized by a considerable number of flightless birds, as well as a high diversity of aerial insectivores and the absence of large arboreal birds. With about 70 currently known species in 42 named genus‐level and at least 39 family‐level taxa, it approaches extant tropical biotas in terms of species richness and taxonomic diversity. With regard to its taxonomic composition and presumed ecological characteristics, the Messel avifauna is more similar to the Neotropics, Madagascar, and New Guinea than to tropical forests in continental Africa and Asia. Because the former regions were geographically isolated during most of the Cenozoic, their characteristics may be due to the absence of biotic factors, especially those related to the diversification of placental mammals, which impacted tropical avifaunas in Africa and Asia. The crown groups of most avian taxa that already existed in early Eocene forests are species‐poor. This does not support the hypothesis that the antiquity of tropical ecosystems is key to the diversity of tropical avifaunas, and suggests that high diversification rates may be of greater significance.     

Fossil calibrations and molecular divergence time estimates in centrarchid fishes (Teleostei: Centrarchidae)

Molecular clock methods allow biologists to estimate divergence times, which in turn play an important role in comparative studies of many evolutionary processes. It is well known that molecular age estimates can be biased by heterogeneity in rates of molecular evolution, but less attention has been paid to the issue of potentially erroneous fossil calibrations. In this study we estimate the timing of diversification in Centrarchidae, an endemic major lineage of the diverse North American freshwater fish fauna, through a new approach to fossil calibration and molecular evolutionary model selection. Given a completely resolved multi-gene molecular phylogeny and a set of multiple fossil-inferred age estimates, we tested for potentially erroneous fossil calibrations using a recently developed fossil cross-validation. We also used fossil information to guide the selection of the optimal molecular evolutionary model with a new fossil jackknife method in a fossil-based model cross-validation. The centrarchid phylogeny resulted from a mixed-model Bayesian strategy that included 14 separate data partitions sampled from three mtDNA and four nuclear genes. Ten of the 31 interspecific nodes in the centrarchid phylogeny were assigned a minimal age estimate from the centrarchid fossil record. Our analyses identified four fossil dates that were inconsistent with the other fossils, and we removed them from the molecular dating analysis. Using fossil-based model cross-validation to determine the optimal smoothing value in penalized likelihood analysis, and six mutually consistent fossil calibrations, the age of the most recent common ancestor of Centrarchidae was 33.59 million years ago (mya). Penalized likelihood analyses of individual data partitions all converged on a very similar age estimate for this node, indicating that rate heterogeneity among data partitions is not confounding our analyses. These results place the origin of the centrarchid radiation at a time of major faunal turnover as the fossil record indicates that the most diverse lineages of the North American freshwater fish fauna originated at the Eocene-Oligocene boundary, approximately 34 mya. This time coincided with major global climate change from warm to cool temperatures and a signature of elevated lineage extinction and origination in the fossil record across the tree of life. Our analyses demonstrate the utility of fossil cross-validation to critically assess individual fossil calibration points, providing the ability to discriminate between consistent and inconsistent fossil age estimates that are used for calibrating molecular phylogenies.     

Cuticle Micromorphology of Pinus krempfii Lecomte (Pinaceae) and Additional Species from Southeast Asia

Cuticle micromorphology of the unusual Vietnamese pine, Pinus krempfii Lecomte, and three additional endemic southeast Asian species of Pinus L. (Pinaceae) is characterized for the first time. Taxa studied include (1) P. krempfii, typically placed in its own subgenus Ducampopinus (Chevalier) Ferré ex Little & Critchfield; (2) the endemic Vietnamese species Pinus dalatensis Ferré and (3) the southeast Asian species Pinus kwantungensis Chun ex Tsiang, both of subgenus Strobus; and (4) the widespread Asian species Pinus kesiya Royle ex Gordon of subgenus Pinus. The current and previous studies demonstrate that the genus Pinus and its subgenera are delimited by unique combinations of cuticular characters, although some of these characters may occur individually in other conifers. Cuticular micromorphology supports taxonomic assignment of P. krempfii to subgenus Strobus rather than to its own subgenus, a result that is also indicated by other anatomical studies and recent molecular studies. Sectional affinities of P. krempfii are usually with Parrya, subsection Krempfianae. An alternative classification of P. krempfii with subsection Gerardianae can be supported by micromorphological characters including broad cuticular bridges between stomata, details of the intercellular flanges of the epidermal cells, and usually an amphistomatic stomatal distribution. Features of other Asian species studied are consistent with their taxonomic assignments. The study demonstrates the utility of cuticle micromorphology to taxonomic delimitation within the family Pinaceae.     

Fossil calibration of molecular divergence infers a moderate mutation rate and recent radiations for pinus

Silent mutation rate estimates for Pinus vary 50-fold, ranging from angiosperm-like to among the slowest reported for plants. These differences either reflect extraordinary genomic processes or inconsistent fossil calibration, and they have important consequences for population and biogeographical inferences. Here we estimate mutation rates from 4 Pinus species that represent the major lineages using 11 nuclear and 4 chloroplast loci. Calibration was tested at the divergence of Pinus subgenera with the oldest leaf fossil from subg. Strobus (Eocene; 45 MYA) or a recently published subg. Strobus wood fossil (Cretaceous; 85 MYA). These calibrations place the origin of Pinus 190-102 MYA and give absolute silent rate estimates of 0.70-1.31x10(-9) and 0.22-0.42x10(-9).site-1.year-1 for the nuclear and chloroplast genomes, respectively. These rates are approximately 4- to 20-fold slower than angiosperms, but unlike many previous estimates, they are more consistent with the high per-generation deleterious mutation rates observed in pines. Chronograms from nuclear and chloroplast genomes show that the divergence of subgenera accounts for about half of the time since Pinus diverged from Picea, with subsequent radiations occurring more recently. By extending the sampling to encompass the phylogenetic diversity of Pinus, we predict that most extant subsections diverged during the Miocene. Moreover, subsect. Australes, Ponderosae, and Contortae, containing over 50 extant species, radiated within a 5 Myr time span starting as recently as 18 MYA. An Eocene divergence of pine subgenera (using leaf fossils) does not conflict with fossil-based estimates of the Pinus-Picea split, but a Cretaceous divergence using wood fossils accommodates Oligocene fossils that may represent modern subsections. Because homoplasy and polarity of character states have not been tested for fossil pine assignments, the choice of fossil and calibration node represents a significant source of uncertainty. Based on several lines of evidence (including agreement with ages inferred using calibrations outside of Pinus), we conclude that the 85 MYA calibration at the divergence of pine subgenera provides a reasonable lower bound and that further refinements in age and mutation rate estimates will require a synthetic examination of pine fossil history.     

‘Fish’ (Actinopterygii and Elasmobranchii) diversification patterns through deep time

Actinopterygii (ray‐finned fishes) and Elasmobranchii (sharks, skates and rays) represent more than half of today's vertebrate taxic diversity (approximately 33000 species) and form the largest component of vertebrate diversity in extant aquatic ecosystems. Yet, patterns of ‘fish’ evolutionary history remain insufficiently understood and previous studies generally treated each group independently mainly because of their contrasting fossil record composition and corresponding sampling strategies. Because direct reading of palaeodiversity curves is affected by several biases affecting the fossil record, analytical approaches are needed to correct for these biases. In this review, we propose a comprehensive analysis based on comparison of large data sets related to competing phylogenies (including all Recent and fossil taxa) and the fossil record for both groups during the Mesozoic–Cainozoic interval. This approach provides information on the ‘fish’ fossil record quality and on the corrected ‘fish’ deep‐time phylogenetic palaeodiversity signals, with special emphasis on diversification events. Because taxonomic information is preserved after analytical treatment, identified palaeodiversity events are considered both quantitatively and qualitatively and put within corresponding palaeoenvironmental and biological settings. Results indicate a better fossil record quality for elasmobranchs due to their microfossil‐like fossil distribution and their very low diversity in freshwater systems, whereas freshwater actinopterygians are diverse in this realm with lower preservation potential. Several important diversification events are identified at familial and generic levels for elasmobranchs, and marine and freshwater actinopterygians, namely in the Early–Middle Jurassic (elasmobranchs), Late Jurassic (actinopterygians), Early Cretaceous (elasmobranchs, freshwater actinopterygians), Cenomanian (all groups) and the Paleocene–Eocene interval (all groups), the latter two representing the two most exceptional radiations among vertebrates. For each of these events along with the Cretaceous‐Paleogene extinction, we provide an in‐depth review of the taxa involved and factors that may have influenced the diversity patterns observed. Among these, palaeotemperatures, sea‐levels, ocean circulation and productivity as well as continent fragmentation and environment heterogeneity (reef environments) are parameters that largely impacted on ‘fish’ evolutionary history, along with other biotic constraints.     

Fruits of Firmiana and Craigia (Malvaceae) from the Eocene of the Central Tibetan Plateau with emphasis on biogeographic history

The fossil record evidences an old origin and diversification of Malvaceae in the Northern Hemisphere. The central Tibetan Plateau was at a low elevation with a monsoon influence during the Eocene, allowing the development of a subtropical flora containing Malvaceae. The taxonomic study of fossils from the Eocene of what is now the Tibetan Plateau is still ongoing. Malvaceae fossils from the Eocene Jianglang flora, are attributed to sub-families Tilioideae and Sterculioideae, and are compared with modern species. A new specimen of Firmiana is described based on a fruit valve with a pinnate venation, the secondary veins starting at the ventral suture and reaching the midvein, and the seeds attached at the proximal part of the ventral suture. This specimen represents the earliest known occurrence of the genus. A new occurrence of Craigia is also reported based on detached membranous valves of a fruit capsule with a prominent fusiform locular area and radiating venation. Based on the fossil record of Firmiana and its modern distribution, we infer that the genus may have originated in East Asia and subsequently diversified in South China and Southeast Asia. The new occurrence of Craigia indicates that the genus was distributed in humid areas in South, Southwest and North China during the Eocene. Both fossil records evidence the important role that the Tibetan region played in the diversification of plants in East and Southeast Asia.     

Diversification rates in the Australasian endemic grass <Emphasis Type="Italic">Austrostipa</Emphasis>: 15 million years of constant evolution

Patterns seen in other Australian flora have led to hypotheses that early Miocene shifts in climate drove rapid radiation of major taxonomic groups such as Eucalyptus. Little is known about absolute dates and rates for Australian monocots, particularly grasses. I tested this early Miocene radiation hypothesis for Australian grasses using a calibrated phylogeny of the endemic stipoid genus Austrostipa and an analysis of diversification rates. The phylogeny was developed from a Bayesian likelihood analysis of the nuclear internal transcribed spacers region, and three calibration points were set based on fossil evidence. The results indicate that the genus arose in the early Miocene and underwent a species radiation, but the rate of diversification was not rapid compared to the current rate or to those of other taxa. Following an 8 million year period of fast molecular evolution but no taxonomic radiation, diversification rates have been constant for the past 15 million years. Comparable measures such as the gamma statistic can be used across taxa to make general conclusions about evolutionary rate constancy.     

To what extent do new fossil discoveries change our understanding of clade evolution? A cautionary tale from burying beetles (Coleoptera: Nicrophorus)

Divergence time estimates derived from phylogenies are crucial to infer historical biogeography and diversification dynamics. Yet, the impact of fossil record incompleteness on macroevolutionary reconstructions remains equivocal. Here, we investigate to what extent gaps in the fossil record can impinge downstream evolutionary inferences in the beetle family Silphidae. Recent discoveries have pushed back the fossil record of this group from the Eocene into the Jurassic. We estimated the divergence times of the family using both its currently understood fossil record and the fossil record known prior to these recent discoveries. All fossil calibrations were informed with different parametric distributions to investigate the weight of priors on posterior age estimates. Based on time‐calibrated trees, we assessed the impact of fossil calibrations on the inference of ancestral ranges and diversification rate dynamics in the genus Nicrophorus. Depending upon the selected sets of fossil constraints, the age discrepancies had a major impact on the macroevolutionary inferences: the biogeographic extrapolations relative to paleogeography are markedly contrasting, and the calculated rates at which species form or go extinct (and when they varied) are strikingly different. We show that soft prior distributions do not necessarily alleviate such shortcomings therefore preventing the inference of reliable macroevolutionary patterns in groups presenting a taphonomic bias in their fossil record.     

Tracing the Origin and Diversification of Dipodoidea (Order: Rodentia): Evidence from Fossil Record and Molecular Phylogeny

Dipodoidea are a diverse rodent group whose earliest known record is from the Middle Eocene. The evolution and diversification of this superfamily have been documented by fossils and comparative morphology, but have not yet been studied from the perspective of molecular phylogeny. This study is the first attempt to reconstruct an extensive phylogeny of Dipodidae and estimate divergence times based on a nuclear gene coding for interphotoreceptor retinoid-binding protein. We found that there is a wide measure of agreement with the fossil record. Each of the three ecological groups of the extant Dipodoidea (sicistines, zapodines, and jerboas) has its distinctive distribution; the distribution patterns have been shaped by the dispersal events. The key events of paleogeographic distribution coincided with major paleoenvironmental events in the Cenozoic. The first important diversification phase occurred during the period from the Oligocene to Early Miocene, when global climate underwent major changes beginning with the Eocene/Oligocene boundary. The second adaptive radiation occurred within jerboas and was associated with the expansion of open habitat starting with the late Middle Miocene. The diversification of jerboas can be correlated with habitat changes in response to global and regional climatic events.     

Not so ancient: the extant crown group of Nothofagus represents a post-Gondwanan radiation

This study uses a molecular-dating approach to test hypotheses about the biogeography of Nothofagus. The molecular modelling suggests that the present-day subgenera and species date from a radiation that most likely commenced between 55 and 40 Myr ago. This rules out the possibility of a reconciled all-vicariance hypothesis for the biogeography of extant Nothofagus. However, the molecular dates for divergences between Australasian and South American taxa are consistent with the rifting of Australia and South America from Antarctica. The molecular dates further suggest a dispersal of subgenera Lophozonia and Fuscospora between Australia and New Zealand after the onset of the Antarctic Circumpolar Current and west wind drift. It appears likely that the New Caledonian lineage of subgenus Brassospora diverged from the New Guinean lineage elsewhere, prior to colonizing New Caledonia.The molecular approach strongly supports fossil-based estimates that Nothofagus diverged from the rest of Fagales more than 84 Myr ago. However, the mid-Cenozoic estimate for the diversification of the four extant subgenera conflicts with the palynological interpretation because pollen fossils, attributed to all four extant subgenera, were widespread across the Weddellian province of Gondwana about 71 Myr ago. The discrepancy between the pollen and molecular dates exists even when confidence intervals from several sources of error are taken into account. In contrast, the molecular age estimates are consistent with macrofossil dates. The incongruence between pollen fossils and molecular dates could be resolved if the early pollen types represent extinct lineages, with similar types later evolving independently in the extant lineages.     

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.     

Fossil records of subsection Pinus (genus Pinus,Pinaceae) from the Cenozoic in Japan

Extant pines of subsection Pinus (section Pinus, genus Pinus, Pinaceae) are predominantly distributed in Eastern Asia. However, the extent of diversification in the section has yet to be fully clarified. We reviewed fossil records of subsection Pinus from Japan and collected permineralized materials, in which anatomical details are preserved for better understanding of the diversification. Our results suggest that this subsection appeared in Japan no earlier than the Middle Eocene, with extant species (i.e., Pinus densiflora and Pinus thunbergii) appearing around the beginning of the Pleistocene. Pinus fujiii (Early Miocene to Early Pleistocene) is inferred to have a close affinity to P. thunbergii based on the medial arrangement of its leaf resin canals. Additionally, P. fujiii has a similar cone morphology to those of extant species living in China, bridging the morphological gap between P. thunbergii and Chinese relatives of P. thunbergii as inferred by molecular phylogenetic analyses. Our results also suggest that taxonomic revisions of Pinus miocenica and Pinus oligolepis are required among the Japanese fossil species reported to date.     

CAESALPINIA SUBGENUS MEZONEURON (LEGUMINOSAE,CAESALPINIOIDEAE) FROM THE TERTIARY OF NORTH AMERICA

Legume fruits from the Eocene of Tennessee and Wyoming and the Miocene of Idaho are described and assigned to Caesalpinia subgenus Mezoneuron (Caesalpinioideae), an extant Paleotropical taxon that does not occur in North or South America today. Morphological and anatomical details of the fruits are used in evaluating their systematic relationships. The features of the fossil fruits are accommodated only within this extant subgenus. These fossils represent the only reliable known occurrence of C. subgenus Mezoneuron in the paleobotanical record. These fossils suggest that subgenus Mezoneuron was distinct from subgenus Caesalpinia by the Middle Eocene. Further, they document the widespread occurrence of this currently Paleotropical group for at least 30 million years in North America.     

Phylogenetic Patterns of Geographical and Ecological Diversification in the Subgenus Drosophila

Colonisation of new geographic regions and/or of new ecological resources can result in rapid species diversification into the new ecological niches available. Members of the subgenus Drosophila are distributed across the globe and show a large diversity of ecological niches. Furthermore, taxonomic classification of Drosophila includes the rank radiation, which refers to closely related species groups. Nevertheless, it has never been tested if these taxonomic radiations correspond to evolutionary radiations. Here we present a study of the patterns of diversification of Drosophila to test for increased diversification rates in relation to the geographic and ecological diversification processes. For this, we have estimated and dated a phylogeny of 218 species belonging to the major species groups of the subgenus. The obtained phylogenies are largely consistent with previous studies and indicate that the major groups appeared during the Oligocene/Miocene transition or early Miocene, characterized by a trend of climate warming with brief periods of glaciation. Ancestral reconstruction of geographic ranges and ecological resource use suggest at least two dispersals to the Neotropics from the ancestral Asiatic tropical disribution, and several transitions to specialized ecological resource use (mycophagous and cactophilic). Colonisation of new geographic regions and/or of new ecological resources can result in rapid species diversification into the new ecological niches available. However, diversification analyses show no significant support for adaptive radiations as a result of geographic dispersal or ecological resource shift. Also, cactophily has not resulted in an increase in the diversification rate of the repleta and related groups. It is thus concluded that the taxonomic radiations do not correspond to adaptive radiations.     

Terpenoids as chemosystematic markers in selected fossil and extant species of pine (Pinus, Pinaceae)

The compositions of terpenoids from the seed cones and resins of selected fossil and modern species of pine ( Pinus , Pinaceae) were analysed using gas chromatography-mass spectrometry (GC-MS) to study the preservation of chemosystematic markers (biomarkers) in fossil conifers. Diterpenoids of the abietane, pimarane, isopimarane, and labdane types are the major components in the solvent extracts of all fossil and extant pines. Mono- and sesquiterpenoids of the bornane and cadalane classes and two phytosterols were also identified. The terpenoid patterns of the fossil species largely match the terpenoids observed in modern pines. The characteristic features of the fossil and extant Pinus species are abietane-, pimarane-, and isopimarane-type diterpenoids with a high abundance of abietic acids. Several biomolecules were preserved unaltered in the Eocene and Oligocene pine cones. In addition to the biomolecules, the fossil pines contain a series of degradation products (geomolecules) that were generated from their biological precursors before and after burial. The generation of the geomolecules is governed by various oxidative and reductive processes, such as microbial degradation and clay catalysis. In conclusion, the comparative analysis of solvent-extractable biomarkers in fossil and related extant species is a valuable tool for (palaeo)chemosystematic studies of conifers.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 154 , 129–140.     

The influence of body size and net diversification rate on molecular evolution during the radiation of animal phyla

Background  

Molecular clock dates, which place the origin of animal phyla deep in the Precambrian, have been used to reject the hypothesis of a rapid evolutionary radiation of animal phyla supported by the fossil record. One possible explanation of the discrepancy is the potential for fast substitution rates early in the metazoan radiation. However, concerted rate variation, occurring simultaneously in multiple lineages, cannot be detected by "clock tests", and so another way to explore such variation is to look for correlated changes between rates and other biological factors. Here we investigate two possible causes of fast early rates: change in average body size or diversification rate of deep metazoan lineages.     

Models for the diversification of life

The diversification of life through geological time a rise from presumably one species to many millions today. The diversification of marine families in the past 600 million years (Myr) appears to have followed two or three logistic curves, with equilibrium levels that lasted for up to 200 Myr. In contrast, continental organisms clearly show an exponential pattern of diversification, and although it is not clear whether the empirical diversification patterns are real or are artefacts of a poor fossil record, the latter explanation seems unlikely. Perhaps marine and continental organisms diversified in different ways, or perhaps the appearance of equilibrium patterns for marine organisms is an artefact of taxonomic structures.     

Fossil wood of <Emphasis Type="Italic">Pinus priamurensis</Emphasis> sp. nov. (Pinaceae) from the Miocene deposits of the Erkovetskii Brown Coal Field,Amur Region

New species of the pine fossil wood, Pinus priamurensis sp. nov. (Pinaceae) from the Sazanka Formation (upper Middle Miocene–Upper Miocene) of the Erkovetskii Brown Coal Field (Amur Region) is described. The new species shares some wood anatomical features with modern species of the subsection Pinus (section Pinus, subgenus Pinus). This is the first record of fossil wood of Pinus in the Amur Region.     

The oldest lamprophiid (Serpentes,Caenophidia) fossil from the late Oligocene Rukwa Rift Basin,Tanzania and the origins of African snake diversity

Extant snake faunas have their origins in the mid-Cenozoic, when colubroids replaced booid-grade snakes as the dominant species. The timing of this faunal changeover in North America and Europe based on fossils is thought to have occurred in the early Neogene, after a period of global cooling opened environments and made them suitable for more active predators. However, new fossils from the late Oligocene of Tanzania have revealed an early colubroid-dominated fauna in Africa suggesting a different pattern of faunal turnover there. Additionally, molecular divergence times suggest colubroid diversification began sometime in the Paleogene, although the exact timing and driving forces behind the diversification are not clear. Here we present the first fossil snake referred to the African clade Lamprophiinae, and the oldest fossil known of Lamprophiidae. As such, this specimen provides the only potential fossil calibration point for the African snake radiation represented by Lamprophiidae, and is the oldest snake referred to Elapoidea. A molecular clock analysis using this and other previously reported fossils as calibration points reveals colubroid diversification minimally occurred in the earliest Paleogene, although a Cretaceous origin cannot be excluded. The elapoid and colubrid lineages diverged during the period of global warming near the Paleocene-Eocene boundary, with both clades diversifying beginning in the early Eocene (proximate to the Early Eocene Climate Optimum) and continuing into the cooler Miocene. The majority of subclades diverge well before the appearance of colubroid dominance in the fossil record. These results suggest an earlier diversification of colubroids than generally previously thought, with hypothesized origins of these clades in Asia and Africa where the fossil record is relatively poorly known. Further work in these regions may provide new insights into the timing of, and environmental influences contributing to, the rise of colubroid snakes.     

Evolutionary diversification of reef corals: a comparison of the molecular and fossil records

Understanding historical patterns of diversity dynamics is of paramount importance for many evolutionary questions. The fossil record has long been the only source of information on patterns of diversification, but the molecular record, derived from time-calibrated phylogenies, is becoming an important additional resource. Both fossil and molecular approaches have shortcomings and biases. These have been well studied for fossil data but much less so for molecular data and empirical comparisons between approaches are lacking. Here, we compare the patterns of diversification derived from fossil and molecular data in scleractinian reef coral species. We also assess the robustness of molecular diversification rates to poor taxon sampling. We find that the temporal pattern of molecular diversification rates is robust to incomplete sampling when rates are calculated per interval. The major obstacle of molecular methods is that rate estimates are distorted because diversification rates can never be negative, whereas the fossil record suffers from incomplete preservation and inconsistent taxonomy. Nevertheless, the molecular pattern of diversification is comparable to the pattern we observe in the fossil record, with the timing of major diversification pulses coinciding in each dataset. For example, both agree that the end-Triassic coral extinction was a catastrophic bottleneck in scleractinian evolution.