Plant fossil record and survival analyses

Cascales‐Miñana, B. & Cleal, C.J. 2011: Plant fossil record and survival analyses. Lethaia, Vol. 45, pp. 71–82. Survival analysis is a classic palaeobiological method widely used on the animal fossil record. This study reports the first application of survivorship analyses on the plant fossil record from a global viewpoint and provides a new comparative approach of this methodology. The results reveal three important plant extinction events in the history of plant life at a global scale. The results also clearly suggest that the origination events are more intensive than extinction processes and that the origination moment of several lineages of vascular plants is an important factor that conditions their longevity. This study supports the general idea that vascular plants tended to be less affected by the environmental changes that caused mass extinction in other groups of organisms. □Extinction events, fossil record, survival patterns, taxonomic survivorship curves, vascular plants.     

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.     

Macroevolution: dynamics of diversity

The fossil record typically exhibits very dynamic patterns of innovation, diversification and extinction. In contrast, molecular phylogenies suggest smoother patterns of evolutionary change. Several new studies reconcile this difference and reveal more about the mechanisms behind macroevolutionary change.     

New crinoids from the Baltic region (Estonia): fossil tip‐dating phylogenetics constrains the origin and Ordovician–Silurian diversification of the Flexibilia (Echinodermata)

This study documents previously unknown taxonomic and morphological diversity among early Palaeozoic crinoids. Based on highly complete, well preserved crown material, we describe two new genera from the Ordovician and Silurian of the Baltic region (Estonia) that provide insight into two major features of the geological history of crinoids: the early evolution of the flexible clade during the Great Ordovician Biodiversification Event (GOBE), and their diversification history surrounding the end‐Ordovician mass extinction. The unexpected occurrence of a highly derived sagenocrinid, Tintinnabulicrinus estoniensis gen. et. sp. nov., from Upper Ordovician (lower Katian) rocks of the Baltic palaeocontinent provides high‐resolution temporal, taxonomic and palaeobiogeographical constraints on the origin and early evolution of the Flexibilia. The Silurian (lower Rhuddanian, Llandovery) Paerticrinus arvosus gen. et sp. nov. is the oldest known Silurian crinoid from Baltica and thus provides the earliest Baltic record of crinoids following the aftermath of the end‐Ordovician mass extinction. A Bayesian ‘fossil tip‐dating’ analysis implementing the fossilized birth–death process and a relaxed morphological clock model suggests that flexibles evolved c. 3 million years prior to their oldest fossil record, potentially involving an ancestor–descendant relationship (via ‘budding’ cladogenesis or anagenesis) with the paraphyletic cladid Cupulocrinus. The sagenocrinid subclade rapidly diverged from ‘taxocrinid’ grade crinoids during the final stages of the GOBE, culminating in maximal diversity among Ordovician crinoid faunas on a global scale. Remarkably, diversification patterns indicate little taxonomic turnover among flexibles across the Late Ordovician mass extinction. However, the elimination of closely related clades may have helped pave the way for their subsequent Silurian diversification and increased ecological role in post‐Ordovician Palaeozoic marine communities. This study highlights the significance of studies reporting faunas from undersampled palaeogeographical regions for clade‐based phylogenetic studies and improving estimates of global biodiversity through geological time.     

The ghosts of mammals past: biological and geographical patterns of global mammalian extinction across the Holocene

Although the recent historical period is usually treated as a temporal base-line for understanding patterns of mammal extinction, mammalian biodiversity loss has also taken place throughout the Late Quaternary. We explore the spatial, taxonomic and phylogenetic patterns of 241 mammal species extinctions known to have occurred during the Holocene up to the present day. To assess whether our understanding of mammalian threat processes has been affected by excluding these taxa, we incorporate extinct species data into analyses of the impact of body mass on extinction risk. We find that Holocene extinctions have been phylogenetically and spatially concentrated in specific taxa and geographical regions, which are often not congruent with those disproportionately at risk today. Large-bodied mammals have also been more extinction-prone in most geographical regions across the Holocene. Our data support the extinction filter hypothesis, whereby regional faunas from which susceptible species have already become extinct now appear less threatened; they may also suggest that different processes are responsible for driving past and present extinctions. We also find overall incompleteness and inter-regional biases in extinction data from the recent fossil record. Although direct use of fossil data in future projections of extinction risk is therefore not straightforward, insights into extinction processes from the Holocene record are still useful in understanding mammalian threat.     

Integration of palaeontological, historical, and geographical data on the extinction of koa-finches

Identifying the root causes of extinction or endangerment requires long chronological records that begin before a population started to decline and extend until its extinction or functional extinction. We present a case study of the koa‐finches, genus Rhodacanthis, an extinct group of Hawaiian honeycreepers that was specialized to feed on green pods and seeds of the koa tree or other leguminous plants. Six island populations of koa‐finches are known; four in the Holocene fossil record and two that survived until the 1890s. We document the palaeoecological context of the fossils and identify constraints on the age span of the specimen record for each population using stratigraphic contexts, associated radiometric determinations, and museum specimen data. We estimate the potential geographical range of koa‐finches at the time of human arrival using two methods: assessment of their historical and palaeo‐habitats, and geographical information system mapping of the pre‐human distribution of the koa plant (Acacia koa) and its sister species, the koai‘a plant (Acacia koaia). After integrating the foregoing data with chronological records and distributional maps of the potential forcing agents of extinction, we conclude that at least two extinctions of island populations were due to ecological change in the lowlands in the prehistorical and perhaps the early historical periods. In the same time frame, the koa‐finch populations on Hawai‘i Island became rare and restricted to upland refugia, making them vulnerable to the upland forest harvesting and degradation that was accelerating in the 1890s. Neither climatic variation nor mosquito‐vectored diseases are likely to have caused the observed extinctions. This study illustrates an approach that can be applied to many other extinct and endangered island species to better understand the causes of high extinction rates in the human era.     

High speciation rate at temperate latitudes explains unusual diversity gradients in a clade of ectomycorrhizal fungi

Understanding the patterns of biodiversity through time and space is a challenging task. However, phylogeny‐based macroevolutionary models allow us to account and measure many of the processes responsible for diversity buildup, namely speciation and extinction. The general latitudinal diversity gradient (LDG) is a well‐recognized pattern describing a decline in species richness from the equator polewards. Recent macroecological studies in ectomycorrhizal (EM) fungi have shown that their LDG is shifted, peaking at temperate rather than tropical latitudes. Here we investigate this phenomenon from a macroevolutionary perspective, focusing on a well‐sampled group of edible EM mushrooms from the genus Amanita—the Caesar's mushrooms, which follow similar diversity patterns. Our approach consisted in applying a suite of models including (1) nontrait‐dependent time‐varying diversification (Bayesian analysis of macroevolutionary mixtures [BAMM]), (2) continuous trait‐dependent diversification (quantitative‐state speciation and extinction [QuaSSE]), and (3) diversity‐dependent diversification. In short, results give strong support for high speciation rates at temperate latitudes (BAMM and QuaSSE). We also find some evidence for different diversity‐dependence thresholds in “temperate” and “tropical” subclades, and little differences in diversity due to extinction. We conclude that our analyses on the Caesar's mushrooms give further evidence of a temperate‐peaking LDG in EM fungi, highlighting the importance and the implications of macroevolutionary processes in explaining diversity gradients in microorganisms.     

Early evolutionary history of the flowering plant family Annonaceae: steady diversification and boreotropical geodispersal

Aim Rain forest‐restricted plant families show disjunct distributions between the three major tropical regions: South America, Africa and Asia. Explaining these disjunctions has become an important challenge in biogeography. The pantropical plant family Annonaceae is used to test hypotheses that might explain diversification and distribution patterns in tropical biota: the museum hypothesis (low extinction leading to steady accumulation of species); and dispersal between Africa and Asia via Indian rafting versus boreotropical geodispersal. Location Tropics and boreotropics. Methods Molecular age estimates were calculated using a Bayesian approach based on 83% generic sampling representing all major lineages within the family, seven chloroplast markers and two fossil calibrations. An analysis of diversification was carried out, which included lineage‐through‐time (LTT) plots and the calculation of diversification rates for genera and major clades. Ancestral areas were reconstructed using a maximum likelihood approach that implements the dispersal–extinction–cladogenesis model. Results The LTT plots indicated a constant overall rate of diversification with low extinction rates for the family during the first 80 Ma of its existence. The highest diversification rates were inferred for several young genera such as Desmopsis, Uvariopsis and Unonopsis. A boreotropical migration route was supported over Indian rafting as the best fitting hypothesis to explain present‐day distribution patterns within the family. Main conclusions Early diversification within Annonaceae fits the hypothesis of a museum model of tropical diversification, with an overall steady increase in lineages possibly due to low extinction rates. The present‐day distribution of species within the two largest clades of Annonaceae is the result of two contrasting biogeographic histories. The ‘long‐branch clade’ has been diversifying since the beginning of the Cenozoic and underwent numerous geodispersals via the boreotropics and several more recent long‐distance dispersal events. In contrast, the ‘short‐branch clade’ dispersed once into Asia via the boreotropics during the Early Miocene and further dispersal was limited.     

Ten years in the library: new data confirm paleontological patterns

A comparison is made between compilations of times of origination and extinction of fossil marine animal families published in 1982 and 1992. As a result of ten years of library research, half of the information in the compendia has changed: families have been added and deleted, low-resolution stratigraphic data been improved, and intervals of origination and extinction have been altered. Despite these changes, apparent macroevolutionary patterns for the entire marine fauna have remained constant. Diversity curves compiled from the two data bases are very similar, with a goodness-of-fit of 99%; the principal difference is that the 1992 curve averages 13% higher than the older curve. Both numbers and percentages of origination and extinction also match well, with fits ranging from 83% to 95%. All major events of radiation and extinction are identical. Therefore, errors in large paleontological data bases and arbitrariness of included taxa are not necessarily impediments to the analysis of pattern in the fossil record, so long as the data are sufficiently numerous.     

Continental faunal exchange and the asymmetrical radiation of carnivores

Lineages arriving on islands may undergo explosive evolutionary radiations owing to the wealth of ecological opportunities. Although studies on insular taxa have improved our understanding of macroevolutionary phenomena, we know little about the macroevolutionary dynamics of continental exchanges. Here we study the evolution of eight Carnivora families that have migrated across the Northern Hemisphere to investigate if continental invasions also result in explosive diversification dynamics. We used a Bayesian approach to estimate speciation and extinction rates from a substantial dataset of fossil occurrences while accounting for the incompleteness of the fossil record. Our analyses revealed a strongly asymmetrical pattern in which North American lineages invading Eurasia underwent explosive radiations, whereas lineages invading North America maintained uniform diversification dynamics. These invasions into Eurasia were characterized by high rates of speciation and extinction. The radiation of the arriving lineages in Eurasia coincide with the decline of established lineages or phases of climate change, suggesting differences in the ecological settings between the continents may be responsible for the disparity in diversification dynamics. These results reveal long-term outcomes of biological invasions and show that the importance of explosive radiations in shaping diversity extends beyond insular systems and have significant impact at continental scales.     

Taxon age,origination, and extinction through geologic time

Changes in the taxon ages of fossil marine families that are alive and those that become extinct in each stage of the Phanerozoic reflect changes in the origination rate, differences in the extinction rate of families with different taxon ages, and mass extinction events. Extinct families are generally much younger than the population from which they were drawn. Periods dominated by higher numbers of younger families are more susceptible to larger size extinctions and greater variation in extinction size. As a result the relative size of extinction peaks must be viewed with regard to the taxon age structure of the population. Mass extinctions cause little change in the taxon age of the fauna. However, adaptive radiations cause a large drop in the average age of the families that are alive at any given time. Families must be treated as dynamic entities in macroevolutionary studies because their probabilities of extinction change over time.     

The fossil record and macroevolutionary history of the beetles

Coleoptera (beetles) is the most species-rich metazoan order, with approximately 380 000 species. To understand how they came to be such a diverse group, we compile a database of global fossil beetle occurrences to study their macroevolutionary history. Our database includes 5553 beetle occurrences from 221 fossil localities. Amber and lacustrine deposits preserve most of the beetle diversity and abundance. All four extant suborders are found in the fossil record, with 69% of all beetle families and 63% of extant beetle families preserved. Considerable focus has been placed on beetle diversification overall, however, for much of their evolutionary history it is the clade Polyphaga that is most responsible for their taxonomic richness. Polyphaga had an increase in diversification rate in the Early Cretaceous, but instead of being due to the radiation of the angiosperms, this was probably due to the first occurrences of beetle-bearing amber deposits in the record. Perhaps, most significant is that polyphagan beetles had a family-level extinction rate of zero for most of their evolutionary history, including across the Cretaceous–Palaeogene boundary. Therefore, focusing on the factors that have inhibited beetle extinction, as opposed to solely studying mechanisms that may promote speciation, should be examined as important determinants of their great diversity today.     

The fossil record of extant elasmobranchs

Sharks and their relatives (Elasmobranchii) are highly threatened with extinction due to various anthropogenic pressures. The abundant fossil record of fossil taxa has allowed the tracing of the evolutionary history of modern elasmobranchs to at least 250 MYA; nonetheless, exactly how far back the fossil record of living taxa goes has never been collectively surveyed. In this study, the authors assess the representation and extent of the fossil record of elasmobranchs currently living in our oceans by collecting their oldest records and quantifying first appearance dates at different taxonomic levels (i.e., orders, families, genera and species), ecological traits (e.g., body size, habitat and feeding mechanism) and extinction risks (i.e., threatened, not threatened and data deficient). The results of this study confirm the robust representation of higher taxonomic ranks, with all orders, most of the families and over half of the extant genera having a fossil record. Further, they reveal that 10% of the current global species diversity is represented in the geological past. Sharks are better represented and extend deeper in time than rays and skates. While the fossil record of extant genera (e.g., the six gill sharks, Hexanchus) goes as far back as c. 190 MYA, the fossil record of extant species (e.g., the sand shark, Carcharias taurus Rafinesque 1810) extends c. 66 MYA. Although no significant differences were found in the extent of the fossil record between ecological traits, it was found that the currently threatened species have a significantly older fossil record than the not threatened species. This study demonstrate that the fossil record of extant elasmobranchs extends deep into the geologic time, especially in the case of threatened sharks. As such, the elasmobranch geological history has great potential to advance the understanding of how species currently facing extinction have responded to different stressors in the past, thereby providing a deep-time perspective to conservation.     

Cyclism revisited: extinction and ‘Achilles’ Heels' keep diversification in check on macroevolutionary time scales

Mass extinctions of varying magnitude prune the continuous diversification predicted by Darwinian evolutionary processes. They are caused by events that are too rare to become adaptatively accommodated. Their effects depend not only on the nature and magnitude of the triggering event but also on the state of the biosphere at the particular time. This is most clearly shown by the existence of Golden Ages preceding all Phanerozoic mass extinctions. These coincide with greenhouse periods, in which doomed clades gave rise to heteromorphs, deviating in strange ways from established bauplans. When critically examined, the seemingly ‘decadent’ morphologies of Schindewolf's ‘typolytic stages’ turn out to have been highly functional. The paradoxical link between adaptive peaks and evolutionary failure can now be explained. Specialisation tends to increase vulnerability (1) by narrowing niches and (2) by the retention of clade-specific conservative features that happen to become fatal Achilles’ Heels for entire clades in the face of a particular perturbation. Following extinctions, the availability of open niches favoured relatively rapid diversification of more innovative clades and their rise to ecological dominance (Schindewolf's ‘typogenetic stage’). Although the long-term changes can be observed only in the fossil record, Golden Biotopes in the present biosphere show that the Darwinian process may also be promoted by ecological isolation. As a result, clade histories do resemble individual biographies, but for ecological rather than orthogenetic reasons. This insight may help us to deal with the present mass extinction caused by our own species.     

Organism activity levels predict marine invertebrate survival during ancient global change extinctions

Multistressor global change, the combined influence of ocean warming, acidification, and deoxygenation, poses a serious threat to marine organisms. Experimental studies imply that organisms with higher levels of activity should be more resilient, but testing this prediction and understanding organism vulnerability at a global scale, over evolutionary timescales, and in natural ecosystems remain challenging. The fossil record, which contains multiple extinctions triggered by multistressor global change, is ideally suited for testing hypotheses at broad geographic, taxonomic, and temporal scales. Here, I assess the importance of activity level for survival of well‐skeletonized benthic marine invertebrates over a 100‐million‐year‐long interval (Permian to Jurassic periods) containing four global change extinctions, including the end‐Permian and end‐Triassic mass extinctions. More active organisms, based on a semiquantitative score incorporating feeding and motility, were significantly more likely to survive during three of the four extinction events (Guadalupian, end‐Permian, and end‐Triassic). In contrast, activity was not an important control on survival during nonextinction intervals. Both the end‐Permian and end‐Triassic mass extinctions also triggered abrupt shifts to increased dominance by more active organisms. Although mean activity gradually returned toward pre‐extinction values, the net result was a permanent ratcheting of ecosystem‐wide activity to higher levels. Selectivity patterns during ancient global change extinctions confirm the hypothesis that higher activity, a proxy for respiratory physiology, is a fundamental control on survival, although the roles of specific physiological traits (such as extracellular pCO₂ or aerobic scope) cannot be distinguished. Modern marine ecosystems are dominated by more active organisms, in part because of selectivity ratcheting during these ancient extinctions, so on average may be less vulnerable to global change stressors than ancient counterparts. However, ancient extinctions demonstrate that even active organisms can suffer major extinction when the intensity of environmental disruption is intense.     

Numerical experiments with model monophyletic and paraphyletic taxa

The problem of how accurately paraphyletic taxa versus monophyletic (i.e., holophyletic) groups (clades) capture underlying species patterns of diversity and extinction is explored with Monte Carlo simulations. Phylogenies are modeled as stochastic trees. Paraphyletic taxa are defined in an arbitrary manner by randomly choosing progenitors and clustering all descendants not belonging to other taxa. These taxa are then examined to determine which are clades, and the remaining paraphyletic groups are dissected to discover monophyletic subgroups. Comparisons of diversity patterns and extinction rates between modeled taxa and lineages indicate that paraphyletic groups can adequately capture lineage information under a variety of conditions of diversification and mass extinction. This suggests that these groups constitute more than mere "taxonomic noise" in this context. But, strictly monophyletic groups perform somewhat better, especially with regard to mass extinctions. However, when low levels of paleontologic sampling are simulated, the veracity of clades deteriorates, especially with respect to diversity, and modeled paraphyletic taxa often capture more information about underlying lineages. Thus, for studies of diversity and taxic evolution in the fossil record, traditional paleontologic genera and families need not be rejected in favor of cladistically-defined taxa.     

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.     

The stratigraphy of mass extinction

Patterns of last occurrences of fossil species are often used to infer the tempo and timing of mass extinction, even though last occurrences generally precede the time of extinction. Numerical simulations with constant extinction demonstrate that last occurrences are not randomly distributed, but tend to cluster at subaerial unconformities, surfaces of forced regression, flooding surfaces and intervals of stratigraphical condensation, all of which occur in predictable stratigraphical positions. This clustering arises not only from hiatuses and non‐deposition, but also from changes in water depth. Simulations with intervals of elevated extinction cause such clusters of last occurrences to be enhanced within and below the interval of extinction, suggesting that the timing and magnitude of extinctions in these instances could be misinterpreted. With the possible exception of the end‐Cretaceous, mass extinctions in the fossil record are characterized by clusters of last occurrences at these sequence stratigraphical horizons. Although these clusters of last occurrences may represent brief pulses of elevated extinction, they are equally likely to form by stratigraphical processes during a protracted period (more than several hundred thousand years) of elevated extinction rate. Geochemical proxies of extinction causes are also affected similarly, suggesting that many local expressions of mass extinction should be re‐evaluated for the timing of extinction and its relation to environmental change. We propose three tests for distinguishing pulses of extinction from clusters of last occurrences produced by stratigraphical processes.     

First Evidence for a Massive Extinction Event Affecting Bees Close to the K-T Boundary

Bees and eudicot plants both arose in the mid-late Cretaceous, and their co-evolutionary relationships have often been assumed as an important element in the rise of flowering plants. Given the near-complete dependence of bees on eudicots we would expect that major extinction events affecting the latter would have also impacted bees. However, given the very patchy distribution of bees in the fossil record, identifying any such extinctions using fossils is very problematic. Here we use molecular phylogenetic analyses to show that one bee group, the Xylocopinae, originated in the mid-Cretaceous, coinciding with the early radiation of the eudicots. Lineage through time analyses for this bee subfamily show very early diversification, followed by a long period of seemingly no radiation and then followed by rapid diversification in each of the four constituent tribes. These patterns are consistent with both a long-fuse model of radiation and a massive extinction event close to the K-T boundary. We argue that massive extinction is much more plausible than a long fuse, given the historical biogeography of these bees and the diversity of ecological niches that they occupy. Our results suggest that events near the K-T boundary would have disrupted many plant-bee relationships, with major consequences for the subsequent evolution of eudicots and their pollinators.     

Vicariance and dispersal in southern hemisphere freshwater fish clades: a palaeontological perspective

Widespread fish clades that occur mainly or exclusively in fresh water represent a key target of biogeographical investigation due to limited potential for crossing marine barriers. Timescales for the origin and diversification of these groups are crucial tests of vicariant scenarios in which continental break‐ups shaped modern geographic distributions. Evolutionary chronologies are commonly estimated through node‐based palaeontological calibration of molecular phylogenies, but this approach ignores most of the temporal information encoded in the known fossil record of a given taxon. Here, we review the fossil record of freshwater fish clades with a distribution encompassing disjunct landmasses in the southern hemisphere. Palaeontologically derived temporal and geographic data were used to infer the plausible biogeographic processes that shaped the distribution of these clades. For seven extant clades with a relatively well‐known fossil record, we used the stratigraphic distribution of their fossils to estimate confidence intervals on their times of origin. To do this, we employed a Bayesian framework that considers non‐uniform preservation potential of freshwater fish fossils through time, as well as uncertainty in the absolute age of fossil horizons. We provide the following estimates for the origin times of these clades: Lepidosireniformes [125–95 million years ago (Ma)]; total‐group Osteoglossomorpha (207–167 Ma); Characiformes (120–95 Ma; a younger estimate of 97–75 Ma when controversial Cenomanian fossils are excluded); Galaxiidae (235–21 Ma); Cyprinodontiformes (80–67 Ma); Channidae (79–43 Ma); Percichthyidae (127–69 Ma). These dates are mostly congruent with published molecular timetree estimates, despite the use of semi‐independent data. Our reassessment of the biogeographic history of southern hemisphere freshwater fishes shows that long‐distance dispersals and regional extinctions can confound and erode pre‐existing vicariance‐driven patterns. It is probable that disjunct distributions in many extant groups result from complex biogeographic processes that took place during the Late Cretaceous and Cenozoic. Although long‐distance dispersals likely shaped the distributions of several freshwater fish clades, their exact mechanisms and their impact on broader macroevolutionary and ecological dynamics are still unclear and require further investigation.