Marine mammals (Cetacea and Sirenia) from the middle and late Eocene of Jordan

2020 ◽  
Vol 298 (2) ◽  
pp. 121-136
Author(s):  
Iyad S. Zalmout ◽  
Hakam A. Mustafa ◽  
Ahmad A. Smadi ◽  
Jammal A. Nazzal ◽  
Philip D. Gingerich
Keyword(s):  
Marine Mammals ◽  
Middle Eocene ◽  
Late Eocene ◽  
Postcranial Remains

Marine mammals including archaeocete Cetacea and dugongid Sirenia are reported from two Eocene localities in Jordan. The first locality, Jebal eth Thuleithuwat, is Lutetian or Bartonian middle Eocene in age. Jebal eth Thuleithuwat has yielded the astragalus and other skeletal elements of a protocetid archaeocete, possible fragments of basilosaurid teeth, and the virtually complete rib of a dugongid (all gen. et sp. indet.). The second locality, Qa' Faydat ad Dahikiya is Priabonian late Eocene in age. Qa' Faydat ad Dahikiya has yielded teeth or postcranial remains of four basilosaurid archaeocetes (Stromerius nidensis, Dorudon atrox, Masracetus markgrafi, and Basilosaurus isis) and postcranial remains of a dugongid (Eotheroides sp).

scholarly journals Geographic contingency, not species sorting, dominates macroevolutionary dynamics in an extinct clade of neogastropods (Volutospina; Volutidae)

Paleobiology ◽  
2021 ◽  
pp. 1-15
Author(s):  
Dana S. Friend ◽  
Brendan M. Anderson ◽  
Warren D. Allmon
Keyword(s):  
Middle Eocene ◽  
Ecological Factors ◽  
Geographic Range ◽  
Late Eocene ◽  
Range Size ◽  
Species Sorting ◽  
Extinction Rates ◽  
Geographic Range Size ◽  
Speciation Rates ◽  
Planktotrophic Larvae

Abstract Rates of speciation and extinction are often linked to many ecological factors, traits (emergent and nonemergent) such as environmental tolerance, body size, feeding type, and geographic range. Marine gastropods in particular have been used to examine the role of larval dispersal in speciation. However, relatively few studies have been conducted placing larval modes in species-level phylogenetic context. Those that have, have not incorporated fossil data, while landmark macroevolutionary studies on fossil clades have not considered both phylogenetic context and net speciation (speciation–extinction) rates. This study utilizes Eocene volutid Volutospina species from the U.S. Gulf Coastal Plain and the Hampshire Basin, U.K., to explore the relationships among larval mode, geographic range, and duration. Based on the phylogeny of these Volutospina, we calculated speciation and extinction rates in order to compare the macroevolutionary effects of larval mode. Species with planktotrophic larvae had a median duration of 9.7 Myr, which compared significantly to 4.7 Myr for those with non-planktotrophic larvae. Larval mode did not significantly factor into geographic-range size, but U.S. and U.K. species do differ, indicating a locality-specific component to maximum geographic-range size. Non-planktotrophs (NPTs)were absent among the Volutospina species during the Paleocene–early Eocene. The relative proportions of NPTs increased in the early middle Eocene, and the late Eocene was characterized by disappearance of planktotrophs (PTs). The pattern of observed lineage diversity shows an increasing preponderance of NPTs; however, this is clearly driven by a dramatic extinction of PTs, rather than higher NPT speciation rates during the late Eocene. This study adds nuance to paleontology's understanding of the macroevolutionary consequences of larval mode.

scholarly journals Impact of mid Eocene greenhouse warming on America’s southernmost floras

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Damián A. Fernández ◽  
Luis Palazzesi ◽  
M. Sol González Estebenet ◽  
M. Cristina Tellería ◽  
Viviana D. Barreda
Keyword(s):  
Middle Eocene ◽  
Pollen Grains ◽  
Late Eocene ◽  
Significant Rise ◽  
Spores And Pollen ◽  
Deep Time ◽  
Nonparametric Estimators ◽  
Southern Patagonia ◽  
Marine Realm ◽  
High Diversity

AbstractA major climate shift took place about 40 Myr ago—the Middle Eocene Climatic Optimum or MECO—triggered by a significant rise of atmospheric CO2 concentrations. The biotic response to this MECO is well documented in the marine realm, but poorly explored in adjacent landmasses. Here, we quantify the response of the floras from America’s southernmost latitudes based on the analysis of terrestrially derived spores and pollen grains from the mid-late Eocene (~46–34 Myr) of southern Patagonia. Robust nonparametric estimators indicate that floras in southern Patagonia were in average ~40% more diverse during the MECO than pre-MECO and post-MECO intervals. The high atmospheric CO2 and increasing temperatures may have favored the combination of neotropical migrants with Gondwanan species, explaining in part the high diversity that we observed during the MECO. Our reconstructed biota reflects a greenhouse world and offers a climatic and ecological deep time scenario of an ice-free sub-Antarctic realm.

Falcatifolium (Podocarpaceae) macrofossils from paleogene sediments in south-eastern Australia: a reassessment

1998 ◽  
Vol 11 (6) ◽  
pp. 711 ◽  
Author(s):  
Robert S. Hill ◽  
Leonie J. Scriven
Keyword(s):  
Leaf Morphology ◽  
Middle Eocene ◽  
Late Eocene ◽  
South Eastern ◽  
Early Oligocene ◽  
Extant Species ◽  
Eastern Australia ◽  
South Eastern Australia

A re-investigation of macrofossils previously referred to the extantpodocarpaceous genus Falcatifolium Laubenfels shows thatno records can be sustained. Falcatifolium australisD.R.Greenwood from Middle Eocene sediments in Victoria bears littleresemblance to extant species in the genus and is transferred to the newfossil genus Sigmaphyllum R.S.Hill & L.J.Scriven.Specimens from Early Oligocene sediments in Tasmania previously assigned toFalcatifolium are described as a second species ofSigmaphyllum, S. tasmanensisR.S.Hill & L.J.Scriven, and specimens from mid to late Eocene sediments inTasmania previously assigned to Falcatifolium do notbelong to that genus, although their true generic affinities are uncertain.Dispersed cuticle specimens from Late Eocene–Oligocene sediments inSouth Australia referred to Falcatifolium are notreliable records of the genus and require further investigation. However,Dacrycarpus eocenica D.R.Greenwood, from Middle Eocenesediments in Victoria is transferred to Falcatifolium,and is similar to the extant species F. angustumLaubenfels, which has a leaf morphology unusual for the genus.Falcatifolium eocenica (D.R.Greenwood) R.S.Hill & L.J.Scriven is the only reliable record of the genus in the Australian fossilrecord to date.

Late Paleogene paleotopographic evolution of the northern Cordilleran orogenic front: Implications for demise of the orogen

2021 ◽  
Author(s):  
Majie Fan ◽  
Kurt N. Constenius ◽  
Rachel F. Phillips ◽  
David L. Dettman
Keyword(s):  
Initial Phase ◽  
Middle Eocene ◽  
High Elevation ◽  
Late Eocene ◽  
Crustal Extension ◽  
Late Oligocene ◽  
Slab Rollback ◽  
Basin Floor ◽  
Climate Cooling ◽  
High Range

The paleotopographic history of the North American Cordilleran orogen holds the key to understanding mechanisms of orogenesis and subsequent orogenic collapse. It has been suggested that the orogenic front in western Montana (USA) and Alberta (Canada) was more than 4 km high during Late Cretaceous−early Eocene contractional deformation and during the initial phase of extension in the middle Eocene; however, the late Eocene−Oligocene topographic evolution during continued extensional collapse remains poorly constrained. Here we extend the paleotopographic record in the Kishenehn Basin in northwestern Montana and southeastern British Columbia (Canada) to the late Oligocene by studying δ18O values of fossil mollusks and cement and paleosol carbonates. The molluscan taxa changed from three sympatric groups with preferred habitats ranging from tropical wet, semi-arid subtropical, and temperate during the middle and late Eocene, to mainly a single group associated with temperate environment during the Oligocene, reflecting a decline in molluscan biodiversity induced by climate cooling across the Eocene−Oligocene transition. Reconstructed δ18O values of alpine snowmelt and basinal precipitation decreased by 1.4‰ and 3.8‰, respectively, from the middle to late Eocene, reflecting climate cooling and ∼1 km surface uplift of the basin floor. The reconstructed alpine snowmelt δ18O values then increased by 2.9‰ in the Oligocene suggesting a ∼0.5 km drop in elevation of the orogenic front. Collectively, the results of our new and previously published δ18O data chronicle the paleotopographic response to the change from flat-slab subduction to slab rollback over a 45 m.y. period. These data suggest that the orogenic front was characterized by high elevation (>4 km) in the ancestral Lewis-Clark-Livingston ranges during latest Cretaceous−early Eocene (ca. 75−52 Ma) contraction. The initial phase of extension related to the Kishenehn Basin created a lowland basin with a surface elevation of only ∼1.5 km during the early middle Eocene (ca. 46−44 Ma) whereas the ranges remained >4 km high. The high range elevations were sustained for at least 12 m.y. in the middle to late Eocene concurrent with extension, while the basin floor elevation was uplifted to ∼2.5 km by the latest Eocene (ca. 36−34 Ma). Basin aggradation can explain at most half of the 1 km basin floor uplift. The remaining amount (at least 0.5 km) and sustained high range elevation suggest that range denudation and crustal extension was compensated by the isostatic and thermal effects of slab rollback and/or passage of a slab window and infusion of hot asthenosphere beneath the continent. The range elevation in the orogenic front decreased ∼0.5 km by the late Oligocene (ca. 28 Ma), associated with a decrease in rock uplift rate associated with extension. A post-Oligocene elevation drop of ∼1 km resulted in both the ranges and basin floor reaching modern topography in the Kishenehn Basin drainage, likely due to the regional effect of Neogene Basin and Range extension. This study, along with the previous investigation of the Kishenehn Basin by Fan et al. (2017), are the first studies that systematically investigate paleorelief of the orogenic belt by reconstructing paleoelevations of the mountains and the basin at the same time. The results highlight that the Cordilleran orogenic front of northern Montana and southern British Columbia sustained its high elevation edifice for at least 12 m.y. after the start of extension. We suggest that initial crustal extension did not result in orogenic demise because of concurrent thermal and isostatic uplift.

scholarly journals U–Pb dating of middle Eocene–Pliocene multiple tectonic pulses in the Alpine foreland

Solid Earth ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 2539-2551
Author(s):  
Luca Smeraglia ◽  
Nathan Looser ◽  
Olivier Fabbri ◽  
Flavien Choulet ◽  
Marcel Guillong ◽  
...  
Keyword(s):  
Middle Eocene ◽  
Regional Scale ◽  
Earthquake Hazard ◽  
Late Eocene ◽  
Passive Margin ◽  
Tectonic Activity ◽  
Thrust Belt ◽  
Fold And Thrust Belt ◽  
Earthquake Hazard Assessment ◽  
Alpine Foreland

Abstract. Foreland fold-and-thrust belts (FTBs) record long-lived tectono-sedimentary activity, from passive margin sedimentation, flexuring, and further evolution into wedge accretion ahead of an advancing orogen. Therefore, dating fault activity is fundamental for plate movement reconstruction, resource exploration, and earthquake hazard assessment. Here, we report U–Pb ages of syn-tectonic calcite mineralizations from four thrusts and three tear faults sampled at the regional scale across the Jura fold-and-thrust belt in the northwestern Alpine foreland (eastern France). Three regional tectonic phases are recognized in the middle Eocene–Pliocene interval: (1) pre-orogenic faulting at 48.4±1.5 and 44.7±2.6 Ma associated with the far-field effect of the Alpine or Pyrenean compression, (2) syn-orogenic thrusting at 11.4±1.1, 10.6±0.5, 9.7±1.4, 9.6±0.3, and 7.5±1.1 Ma associated with the formation of the Jura fold-and-thrust belt with possible in-sequence thrust propagation, and (3) syn-orogenic tear faulting at 10.5±0.4, 9.1±6.5, 5.7±4.7, and at 4.8±1.7 Ma including the reactivation of a pre-orogenic fault at 3.9±2.9 Ma. Previously unknown faulting events at 48.4±1.5 and 44.7±2.6 Ma predate the reported late Eocene age for tectonic activity onset in the Alpine foreland by ∼10 Myr. In addition, we date the previously inferred reactivation of pre-orogenic strike-slip faults as tear faults during Jura imbrication. The U–Pb ages document a minimal time frame for the evolution of the Jura FTB wedge by possible in-sequence thrust imbrication above the low-friction basal decollement consisting of evaporites.

scholarly journals Expansion and diversification of high-latitude radiolarian assemblages in the late Eocene linked to a cooling event in the Southwest Pacific

2015 ◽  
Vol 11 (4) ◽  
pp. 2977-3018 ◽  
Author(s):  
K. M. Pascher ◽  
C. J. Hollis ◽  
S. M. Bohaty ◽  
G. Cortese ◽  
R. M. McKay
Keyword(s):  
Oxygen Isotope ◽  
High Latitude ◽  
Large Scale ◽  
Middle Eocene ◽  
Late Eocene ◽  
Climate History ◽  
Southwest Pacific ◽  
Early Oligocene ◽  
Radiolarian Assemblages

Abstract. The Eocene was characterised by "greenhouse" climate conditions that were gradually terminated by a long-term cooling trend through the middle and late Eocene. This long-term trend was determined by several large-scale climate perturbations that culminated in a shift to "ice-house" climates at the Eocene–Oligocene Transition. Geochemical and micropaleontological proxies suggest that tropical-to-subtropical sea-surface temperatures persisted into the late Eocene in the high-latitude Southwest Pacific Ocean. Here, we present radiolarian microfossil assemblage and foraminiferal oxygen and carbon stable isotope data from Deep Sea Drilling Project (DSDP) Sites 277, 280, 281 and 283 from the middle Eocene to early Oligocene (~ 40–33 Ma) to identify oceanographic changes in the Southwest Pacific across this major transition in Earth's climate history. The Middle Eocene Climatic Optimum at ~ 40 Ma is characterised by a negative shift in foraminiferal oxygen isotope values and a radiolarian assemblage consisting of about 5 % of low latitude taxa Amphicraspedum prolixum group and Amphymenium murrayanum. In the early late Eocene at ~ 37 Ma, a positive oxygen isotope shift can be correlated to the Priabonian Oxygen Isotope Maximum (PrOM) event – a short-lived cooling event recognized throughout the Southern Ocean. Radiolarian abundance, diversity, and preservation increase during the middle of this event at Site 277 at the same time as diatoms. The PrOM and latest Eocene radiolarian assemblages are characterised by abundant high-latitude taxa. These high-latitude taxa also increase in abundance during the late Eocene and early Oligocene at DSDP Sites 280, 281 and 283 and are associated with very high diatom abundance. We therefore infer a~northward expansion of high-latitude radiolarian taxa onto the Campbell Plateau towards the end of the late Eocene. In the early Oligocene (~ 33 Ma) there is an overall decrease in radiolarian abundance and diversity at Site 277, and diatoms are absent. These data indicate that, once the Tasman Gateway was fully open in the early Oligocene, a frontal system similar to the present day was established, with nutrient-depleted subantarctic waters bathing the area around DSDP Site 277, resulting in a more oligotrophic siliceous plankton assemblage.

scholarly journals The middle to late Eocene greenhouse climate modelled using the CESM 1.0.5

2020 ◽  
Vol 16 (6) ◽  
pp. 2573-2597
Author(s):  
Michiel Baatsen ◽  
Anna S. von der Heydt ◽  
Matthew Huber ◽  
Michael A. Kliphuis ◽  
Peter K. Bijl ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Radiative Forcing ◽  
Middle Eocene ◽  
Late Eocene ◽  
Collective Effects ◽  
Polar Regions ◽  
Radiative Balance ◽  
Industrial Carbon ◽  
Greenhouse Climate ◽  
Modelling Studies

Abstract. The early and late Eocene have both been the subject of many modelling studies, but few have focused on the middle Eocene. The latter still holds many challenges for climate modellers but is also key to understanding the events leading towards the conditions needed for Antarctic glaciation at the Eocene–Oligocene transition. Here, we present the results of CMIP5-like coupled climate simulations using the Community Earth System Model (CESM) version 1. Using a new detailed 38 Ma geography reconstruction and higher model resolution compared to most previous modelling studies and sufficiently long equilibration times, these simulations will help to further understand the middle to late Eocene climate. At realistic levels of atmospheric greenhouse gases, the model is able to show overall good agreement with proxy records and capture the important aspects of a warm greenhouse climate during the Eocene. With a quadrupling of pre-industrial concentrations of both CO2 and CH4 (i.e. 1120 ppm and ∼2700 ppb, respectively, or 4 × PIC; pre-industrial carbon), sea surface temperatures correspond well to the available late middle Eocene (42–38 Ma; ∼ Bartonian) proxies. Being generally cooler, the simulated climate under 2 × PIC forcing is a good analogue for that of the late Eocene (38–34 Ma; ∼ Priabonian). Terrestrial temperature proxies, although their geographical coverage is sparse, also indicate that the results presented here are in agreement with the available information. Our simulated middle to late Eocene climate has a reduced Equator-to-pole temperature gradient and a more symmetric meridional heat distribution compared to the pre-industrial reference. The collective effects of geography, vegetation, and ice account for a global average 5–7 ∘C difference between pre-industrial and 38 Ma Eocene boundary conditions, with important contributions from cloud and water vapour feedbacks. This helps to explain Eocene warmth in general, without the need for greenhouse gas levels much higher than indicated by proxy estimates (i.e. ∼500–1200 ppm CO2) or low-latitude regions becoming unreasonably warm. High-latitude warmth supports the idea of mostly ice-free polar regions, even at 2 × PIC, with Antarctica experiencing particularly warm summers. An overall wet climate is seen in the simulated Eocene climate, which has a strongly monsoonal character. Equilibrium climate sensitivity is reduced (0.62 ∘C W−1 m2; 3.21 ∘C warming between 38 Ma 2 × PIC and 4 × PIC) compared to that of the present-day climate (0.80 ∘C W−1 m2; 3.17 ∘C per CO2 doubling). While the actual warming is similar, we see mainly a higher radiative forcing from the second PIC doubling. A more detailed analysis of energy fluxes shows that the regional radiative balance is mainly responsible for sustaining a low meridional temperature gradient in the Eocene climate, as well as the polar amplification seen towards even warmer conditions. These model results may be useful to reconsider the drivers of Eocene warmth and the Eocene–Oligocene transition (EOT) but can also be a base for more detailed comparisons to future proxy estimates.

Continental temperature seasonality from Eocene Warmhouse to Oligocene Coolhouse — A model-data comparison

2021 ◽  
Author(s):  
Agathe Toumoulin ◽  
Yannick Donnadieu ◽  
Delphine Tardif ◽  
Jean-Baptiste Ladant ◽  
Alexis Licht ◽  
...  
Keyword(s):  
Sea Level ◽  
Northern Hemisphere ◽  
Surface Albedo ◽  
Middle Eocene ◽  
Late Eocene ◽  
Strong Increase ◽  
High Latitudes ◽  
Sea Level Changes ◽  
Annual Range ◽  
Temperature Seasonality

<p>At the junction of warmhouse and coolhouse climate phases, the Eocene Oligocene Transition (EOT) is a key moment in the history of the Cenozoic climate. Yet, while it is accompanied by severe extinctions and biodiversity turnovers, terrestrial climate evolution remains poorly resolved. On lands, some fossil and geochemistry records suggest a particularly marked cooling in winter, which would have led to the development of more pronounced seasons (higher Mean Annual Range of Temperatures, MATR) in certain regions of the Northern Hemisphere. This type of climate change should have had consequences on biodiversity and an implication in some of the fauna and flora renewals described at the EOT. However, this season strengthening has been studied only superficially by model studies, and questions remain about the geographical extent of this phenomenon and the associated climatic processes. Although other components of the climate system vary seasonally (e.g., precipitation, wind), we therefore focus on the seasonality of temperatures only.</p><p>In order to better understand and describe temperature seasonality change patterns from the middle Eocene to the early Oligocene, we use the Earth System Model IPSL-CM5A2 and a set of simulations reconstructing the EOT through three major climate forcings: pCO2 decrease (1120/840 to 560 ppm), the Antarctic ice-sheet (AIS) formation, and the associated sea-level decrease (-70 m). </p><p>Our results suggest that seasonality changes across the EOT rely on the combined effects of the different tested mechanisms which result in zonal to regional climate responses. Sea-level changes associated with the earliest stage of the AIS formation may have also contributed to middle to late Eocene MATR reinforcement. We reconstruct strong and heterogeneous patterns of seasonality changes across the EOT. Broad continental areas of increased MATR reflect a strengthening of seasonality (from 4°C to > 10°C increase of the MATR) in agreement with MATR and Coldest Month Mean Temperatures (CMMT) changes indicated by a review of existing proxies. pCO2 decrease induces a zonal pattern with alternating increasing and decreasing seasonality bands. In the northern high-latitudes, it results in sea-ice and surface albedo feedback, driving a strong increase in seasonality (up to 8°C MATR increase). Conversely, the onset of the AIS is responsible for a more constant surface albedo, which leads to a strong decrease in seasonality in the southern mid- to high-latitudes (> 40°S). Finally, continental areas emerged due to the sea level lowering cause the largest increase in seasonality and explain most of the global heterogeneity in MATR changes patterns. The seasonality change patterns we reconstruct are consistent with the variability of the EOT biotic crisis intensity across the Northern Hemisphere.</p>

Geological Correlation Between Northern Cyprus And Southern Anatolia

2021 ◽  
Author(s):  
Yucel Yilmaz
Keyword(s):  
Carbonate Platform ◽  
Middle Eocene ◽  
Source Region ◽  
Oceanic Lithosphere ◽  
Late Eocene ◽  
Central Anatolia ◽  
Late Cenozoic ◽  
Ophiolitic Mélange ◽  
South Central ◽  
Northern Cyprus

The island of Cyprus constitutes a fragment of southern Anatolia separated from the mainland by left-oblique transtension in late Cenozoic time. However, a geological framework of offset features of the south-central Anatolia, for comparison of Cyprus with a source region within and west of the southeastern Anatolian suture zone, has not yet been developed. In this paper, I enumerate, describe, and compare a full suite of potentially correlative spatial and temporal elements exposed in both regions. Northern Cyprus and south-central Anatolia have identical tectonostratigraphic units. At the base of both belts, crop out ophiolitic mélange-accretionary complex generated during the northward subduction of the NeoTethyan Oceanic lithosphere from the Late Cretaceous until the end of middle Eocene. The nappes of the Taurus carbonate platform were thrust above this internally chaotic unit during late Eocene. They began to move as a coherent nappe pile from that time onward. An asymmetrical flysch basin was formed in front of this southward moving nappe pile during the early Miocene. The nappes were then thrust over the flysch basin fill and caused its tight folding. Cyprus separated from Anatolia in the Pleistocene-Holocene when, transtensional oblique faults with dip-slip components caused the development of the Adana and Iskenderun basins and the separation of Cyprus from Anatolia.

Crocodilian diversity in space and time: the role of climate in paleoecology and its implication for understanding K/T extinctions

Paleobiology ◽  
1998 ◽  
Vol 24 (4) ◽  
pp. 470-497 ◽  
Author(s):  
Paul J. Markwick
Keyword(s):  
Northern Hemisphere ◽  
Middle Eocene ◽  
Temporal Trends ◽  
Late Eocene ◽  
High Rate ◽  
Mass Extinctions ◽  
Crown Group ◽  
Climatic Effects ◽  
General Decline

The taxonomic diversity of crocodilians (Crocodylia) through the last 100 million years shows a general decline in the number of genera and species to the present day. But this masks a more complex pattern. This is investigated here using a comprehensive database of fossil crocodilians that provides the opportunity to examine spatial and temporal trends, the influence of sampling, and the role of climate in regulating biodiversity.Crown-group crocodilians, comprising the extant families Alligatoridae, Crocodylidae, and Gavialidae, show the following trend: an initial exponential diversification through the Late Cretaceous and Paleocene that is restricted to the Northern Hemisphere until after the K/T boundary; relatively constant diversity from the Paleocene into the middle Eocene that may be an artifact of sampling, which might mask an actual decline in numbers; low diversity during the late Eocene and Oligocene; a second exponential diversification during the Miocene and leveling off in the late Miocene and Pliocene; and a precipitous drop in the Pleistocene and Recent. The coincidence of drops in diversity with global cooling is suggestive of a causal link—during the initial glaciation of Antarctica in the Eocene and Oligocene and the Northern Hemisphere glaciation at the end of the Pliocene. However, matters are complicated in the Northern Hemisphere by the climatic effects of regional uplift.Although the global trend of diversification is unperturbed at the K/T boundary, this is largely due to the exceptionally high rate of origination in the early Paleocene. Nonetheless, the survival of such a demonstrably climate-sensitive group strongly suggests that a climatic explanation for the K/T mass extinctions, especially the demise of the dinosaurs, must be reconsidered.

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