Paleobiogeography and biodiversity of Late Maastrichtian dinosaurs: how many dinosaur species went extinct at the Cretaceous-Tertiary boundary?

2012 ◽  
Vol 183 (6) ◽  
pp. 547-559 ◽  
Author(s):  
Jean Le Loeuff
Keyword(s):  
Late Cretaceous ◽  
Fossil Record ◽  
Dinosaur Extinction ◽  
Order Of Magnitude ◽  
Species Area ◽  
The Mean ◽  
Species Area Relationship ◽  
Global Biodiversity ◽  
Chicxulub Impact ◽  
First Time

Abstract The global Late Maastrichtian non-avian dinosaur apparent biodiversity is extensively surveyed for the first time. It amounts to 104 species (including unnamed forms) in 2010. The real biodiversity being obscured by taphonomical biases and the scarcity of the continental fossil record, a species-area relationship is used to estimate it. The results show that several hundreds (between 628 and 1078) non-avian dinosaur species were alive in the Late Maastrichtian, which is almost an order of magnitude above previous estimates. Because of the complex Late Cretaceous palaeobiogeography, discussions about dinosaur extinction should be based on this estimated real global biodiversity, not on the apparent biodiversity of a single area. Given the mean duration of dinosaur genera (7.7 Ma), the presence of so many dinosaur species in the Latest Cretaceous is consistent with the termination of most lineages at the Cretaceous-Tertiary boundary (the Late Maastrichtian sub-stage is 2.8 m.y. long). The Late Maastrichtian dinosaurian biodiversity is therefore consistent with the sudden extinction of the group following the Chicxulub impact.

scholarly journals PRELIMINARY REPORT ON THE LACUSTRINE STRATA OF THE SANFRANCISCANA BASIN IN NORTHERN MINAS GERAIS, BRAZIL

2020 ◽  
pp. 1-10
Author(s):  
Jonathas S. Bittencourt ◽  
Pedro L. C. R. Vieira ◽  
Raphael M. Horta ◽  
André G. Vasconcelos ◽  
Natália C. A. Brandão ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Fossil Record ◽  
Preliminary Report ◽  
Upper Cretaceous ◽  
Minas Gerais ◽  
Fish Scales ◽  
The North ◽  
Younger Age ◽  
First Time ◽  
Pelitic Rocks

We report new data on the geology and the fossil record of the Sanfranciscana Basin in sites to the north of the traditionally explored localities within Minas Gerais. The strata in the new explored area are formed by distinct lithologies, encompassing pelitic rocks with caliche levels and metric bodies of cross-bedded sandstone towards the top, similar to the fluviolacustrine beds of the Areado Group in the southern portions of the basin. Also similar to other regions of the São Francisco Craton, the deposits of the Sanfranciscana Basin studied herein lie discordantly to the rocks of the Bambuí Basin. We preliminarily report neopterygian fish scales, little informative archosaurian bones and an association of the ostracods Ilyocypris- Fossocytheridea. This ostracod association is registered for the first time in the Cretaceous of the Sanfranciscana Basin. The ostracods have been collected from the lacustrine, vertebrate-bearing rocks cropping out in Lagoa dos Patos and Coração de Jesus. The cytherideid Fossocytheridea assigns a minimal Aptian age to its bearing rocks. Its association with Ilyocypris was also reported in Upper Cretaceous oligohaline paleoenvironments in Brazil and Argentina, indicating similar depositional conditions to the strata reported in this paper. The putative affinities of the specimens of the Sanfranciscana Basin with F. ventrotuberculata, and their association with Ilyocypris, raise the hypothesis of a younger age for some levels of that basin in northern Minas Gerais, perhaps ranging into the Late Cretaceous. Keywords: Ostracoda, Archosauria, Areado Group, Cretaceous, Gondwana

Fossil crabs (Crustacea: Decapoda) from the Late Cretaceous cárdenas Formation, east-central Mexico

1995 ◽  
Vol 69 (2) ◽  
pp. 340-350 ◽  
Author(s):  
Francisco J. Vega ◽  
Rodney M. Feldmann ◽  
Francisco Sour-Tovar
Keyword(s):  
Late Cretaceous ◽  
Fossil Record ◽  
New Genus ◽  
Gulf Coast ◽  
Central Mexico ◽  
New Genus And Species ◽  
East Central ◽  
The Family ◽  
Marine Lagoon ◽  
First Time

Twenty-four nearly complete carapace samples were collected at three different localities of the Maastrichtian (Late Cretaceous) Cárdenas Formation in San Luis Potosí, east-central Mexico. The material has been assigned to five families: the Callianassidae, Dakoticancridae, Carcineretidae, ?Majidae, and Retroplumidae. Two genera of callianassid shrimp are described, Cheramus for the first time in the fossil record. Dakoticancer australis Rathbun is reported as the most abundant crustacean element; one new genus and species of carcineretid crab, Branchiocarcinus cornatus, is erected, and a single, fragmentary specimen is questionably referred to the Majidae. The three localities reflect paleoenvironmental differences, exhibited by different lithologies, within marginal marine, lagoon environments. The record of dakoticancrid crabs in the Cardenas Formation extends the paleobiogeographic range of the family and the genus Dakoticancer. Carcineretid crabs, although not abundant, seem to have been a persistent element of crustacean assemblages in clastic environments during the Late Cretaceous of the ancestral Gulf Coast of Mexico.

scholarly journals Breakup of a long-period comet as the origin of the dinosaur extinction

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Amir Siraj ◽  
Abraham Loeb
Keyword(s):  
Impact Crater ◽  
Main Belt ◽  
Long Period ◽  
Dinosaur Extinction ◽  
Chicxulub Impact Crater ◽  
Order Of Magnitude ◽  
Mass Extinction Event ◽  
Chicxulub Impact ◽  
The Impact ◽  
Impact Events

AbstractThe origin of the Chicxulub impactor, which is attributed as the cause of the K/T mass extinction event, is an unsolved puzzle. The background impact rates of main-belt asteroids and long-period comets have been previously dismissed as being too low to explain the Chicxulub impact event. Here, we show that a fraction of long-period comets are tidally disrupted after passing close to the Sun, each producing a collection of smaller fragments that cross the orbit of Earth. This population could increase the impact rate of long-period comets capable of producing Chicxulub impact events by an order of magnitude. This new rate would be consistent with the age of the Chicxulub impact crater, thereby providing a satisfactory explanation for the origin of the impactor. Our hypothesis explains the composition of the largest confirmed impact crater in Earth’s history as well as the largest one within the last million years. It predicts a larger proportion of impactors with carbonaceous chondritic compositions than would be expected from meteorite falls of main-belt asteroids.

scholarly journals A new genus and species of enantiornithine bird from the Early Cretaceous of Brazil

2015 ◽  
Vol 45 (2) ◽  
pp. 161-171 ◽  
Author(s):  
Ismar de Souza Carvalho ◽  
Fernando E. Novas ◽  
Federico L. Agnolín ◽  
Marcelo P. Isasi ◽  
Francisco I. Freitas ◽  
...  
Keyword(s):  
South America ◽  
Early Cretaceous ◽  
Late Cretaceous ◽  
Fossil Record ◽  
New Genus ◽  
The Body ◽  
New Genus And Species ◽  
First Time

<p>The fossil record of birds in Gondwana is almost restricted to the Late Cretaceous. Herein we describe a new fossil from the Araripe Basin, <italic>Cratoavis cearensis</italic> nov. gen et sp., composed of an articulated skeleton with feathers attached to the wings and surrounding the body. The present discovery considerably extends the temporal record of the Enantiornithes birds at South America to the Early Cretaceous. For the first time, an almost complete and articulated skeleton of an Early Cretaceous bird from South America is documented.</p>

Paleocene isocrinids (Echinodermata: Crinoidea) from the Kauru Formation, South Island, New Zealand

1994 ◽  
Vol 68 (1) ◽  
pp. 135-141 ◽  
Author(s):  
Jeffrey D. Stilwell ◽  
R. Ewan Fordyce ◽  
Peter J. Rolfe
Keyword(s):  
New Zealand ◽  
Storm Surge ◽  
Late Cretaceous ◽  
Fossil Record ◽  
High Energy ◽  
Coarse Grained ◽  
Local Equivalent ◽  
Energy Environment ◽  
First Time

Crinoids are reported from the New Zealand Paleocene for the first time and include rare articulated columnals and brachia with pinnules. These specimens of Metacrinus sp. (Isocrinidae) are present in basal, fossiliferous, coarse-grained, quartzose sediments of the Kauru Formation, a few centimeters above schist basement, in the Kakanui Valley, North Otago. The crinoid-bearing facies probably represents earliest onlap or a storm surge onto a wave cut platform; sedimentological and paleontological evidence indicates a moderate- to high-energy environment. The crinoids were most probably buried rapidly while alive or shortly after death. The presence of isocrinids in the Kauru Formation and younger Paleogene strata reveals that the supposed shift of some isocrinids from a shallower to a deeper environment actually occurred much later in the Paleogene, and not the Late Cretaceous as previously supposed. Associated molluscs indicate a mid to upper “Wangaloan” Stage (local), equivalent to mid Paleocene. A summary of the New Zealand crinoid fossil record is presented.

scholarly journals Hominin cranial fragments from Milner Hall, Sterkfontein, South Africa

2018 ◽  
Vol 114 (11/12) ◽  
Author(s):  
Amélie Beaudet ◽  
Jason L. Heaton ◽  
Ericka N. L’Abbé ◽  
Travis R. Pickering ◽  
Dominic Stratford
Keyword(s):  
Fossil Record ◽  
Structural Organization ◽  
Relative Proportion ◽  
Stone Tools ◽  
Quantitative Investigation ◽  
Sedimentary Deposits ◽  
Non Invasive ◽  
Fossil Hominins ◽  
The Mean ◽  
First Time

The Sterkfontein Caves site is one of the richest early hominin localities in Africa. In addition to significant fossil assemblages from Members 2 and 4 of the Sterkfontein Formation, recent excavations have revealed hominin-bearing sedimentary deposits in the lesser-known Milner Hall. We describe two hominin cranial fragments excavated from the Milner Hall in 2015 and present the results of a high-resolution microtomographic-based approach to diagnosing the anatomical and taxonomical origin of these specimens. Based on external morphology, StW 671 and StW 672 are tentatively identified as frontal and occipital fragments, respectively. Our non-invasive bi-dimensional quantitative investigation of the two cranial fragments reveals a mean cranial thickness of 8.8 mm and 5.6 mm for StW 671 and StW 672 respectively and a contribution of the diploic layer to the cumulative cranial thickness that is less than 50%. While the mean cranial thickness of StW 671 falls within the range of Homo, the relative proportion of the diploë in both StW 671 and StW 672 is lower than in Australopithecus (>60%) and extant humans (>50%). Accordingly, in terms of both cranial thickness and inner structural organization, the Milner Hall hominins combine derived and unique traits, consistent with the condition of other postcranial and dental material already described from the deposit. Moreover, our study opens interesting perspectives in terms of analysis of isolated cranial fragments, which are abundant in the hominin fossil record. Significance: The Sterkfontein Caves have widely contributed to our understanding of human evolution. Besides the well-known Members 4 and 2, where the iconic ‘Mrs Ples’ and ‘Little Foot’ have been found, in this study we suggest that the Milner Hall locality represents an additional, stratigraphically associated source of not only fossil hominins, but also Oldowan stone tools. In particular, we describe for the first time two cranial fragments, StW 671 and StW 672, identified as frontal and occipital bones, respectively. Our microtomographic-based analysis of these materials reveals some affinities with Homo combined with unique characters. In this context, our study suggests an intriguing mosaicism consistent with the description of the two fossil hominins found in the Milner Hall.

Questioning Israel's Great Biodiversity—Relative to Whom? A Comment on Roll et al., 2009

2011 ◽  
Vol 57 (3) ◽  
pp. 183-192 ◽  
Author(s):  
Yoni Gavish
Keyword(s):  
Species Richness ◽  
Linear Regression ◽  
Unit Area ◽  
Biodiversity Hotspot ◽  
Biodiversity Hotspots ◽  
Species Area ◽  
C Value ◽  
Species Area Relationship ◽  
Z Value ◽  
Global Biodiversity

Each evolutionary-independent province has its own mainland species area relationship (SPAR). When using the power law SPAR (S = cAz), separate mainland SPARs are parallel in a log-log space (similar z value), yet they differ in species density per unit area (c value). This implies that there are two main SPAR-based strategies to identify biodiversity hotspots. The first treats all mainland SPARs of all provinces as if they form one global SPAR. This is the strategy employed by Roll et al. (2009) when questioning Israel's high biodiversity. They concluded that Israel is not a global biodiversity hotspot. Their results may arise from the fact that Israel's province, the Palaearctic, is relatively poor. Therefore, countries from richer provinces, whose mainland SPAR lies above the Palaearctic SPAR, are identified as global hotspots. The second strategy is to construct different mainland SPARs for each province and identify the provincial hotspots. In this manuscript I ask whether Israel's biodiversity is high relative to other countries within its province. For six different taxa, I analyzed data for Palaearctic countries. For each taxon, I conducted a linear regression of species richness against the country's area, both log transformed. The studentized residuals were used to explore Israel's rank relative to all other Palaearctic countries. I found that Israel lies above the 95th percentile for reptiles and mammals and above the 90th percentile for birds. Therefore, within the Palaearctic province, Israel is indeed a biodiversity hotspot.

Transmembranal Action Potentials From Pregnant Uterus

1956 ◽  
Vol 187 (2) ◽  
pp. 338-340 ◽  
Author(s):  
J. Walter Woodbury ◽  
Donald M. McIntyre
Keyword(s):  
Guinea Pig ◽  
Action Potential ◽  
Guinea Pigs ◽  
Action Potentials ◽  
Resting Potential ◽  
Pregnant Uterus ◽  
Uterine Muscle ◽  
Order Of Magnitude ◽  
The Mean ◽  
First Time

For the first time overshooting action potentials of pregnant guinea pig uterus have been recorded intracellularly. Flexibly mounted ultramicroelectrodes were used. The largest action potential (AP) seen was 48 mv with an associated resting potential (RP) of 38 mv. The mean of 129 measurements of RP in four guinea pigs was 32.6 mv. The mean of 86 AP's was 21.9 mv. Although overshoot was seen only occasionally, the action potentials were always of the same order of magnitude as the resting potentials. It seems probable that the excitable mechanisms of uterine muscle though labile and variable are closely similar to those of other tissues.

scholarly journals The species-area-energy relationship in orchids

Lankesteriana ◽  
2015 ◽  
Vol 7 (1-2) ◽  
Author(s):  
Iva Schödelbauerová ◽  
Pavel Kindlmann ◽  
David Roberts
Keyword(s):  
Species Richness ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Unit Area ◽  
Relative Importance ◽  
Species Area ◽  
The Mean ◽  
Main Factors ◽  
Species Area Relationship ◽  
The Tropics

Area, energy available and latitude are the main factors influencing species richness: (1) species richness increases with area – the species-area relationship (SAR); (2) according to the species-energy rela- tionship (SER) the energy available to an assemblage (i.e. that which it can turn into biomass) at a particular spatial resolution influences the species richness; (3) there are more species per unit area in the tropics than in the temperate regions. To test the relative importance of area, energy available and latitude on species richness, we have collected data on species richness of orchids for various areas in the world and calculated the mean Normalized Difference Vegetation Index (NDVI) as a measure of energy availability in these areas. We show that area considered is always very important, and that latitude is more important than ener- gy available. 

scholarly journals Crustaceans in cold seep ecosystems: fossil record, geographic distribution, taxonomic composition, and biology

2018 ◽  
Author(s):  
Adiël A. Klompmaker ◽  
Torrey Nyborg ◽  
Jamie Brezina ◽  
Yusuke Ando
Keyword(s):  
South Dakota ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Taxonomic Composition ◽  
Cold Seep ◽  
Decapod Crustaceans ◽  
Deep Waters ◽  
Primary Literature ◽  
First Time ◽  
Squat Lobsters

Crustaceans including decapods, copepods, amphipods, cumaceans, tanaidaceans, ostracods, and isopods are major components of modern marine methane seeps, where they play a key role in structuring these hotspots of diversity in relatively deep waters. There is every reason to suspect they were common too in ancient seeps, but relatively few studies have focused on crustaceans from fossil seep deposits thus far. We hypothesize that crustaceans can be commonly found in Meso-Cenozoic seeps when many of the aforementioned groups were present and/or radiated. To this end, we review the global fossil record of crustaceans in seeps for the first time using the primary literature and newly collected specimens from the Late Cretaceous of South Dakota, USA. We find that seep crustaceans are much more common than previously known, are found on each continent, and occur more frequently starting in the Jurassic. Decapod crustaceans are represented by body fossils and traces (coprolites, repair scars in mollusks, and burrows), whereas only body fossils of ostracods and barnacles are known. Other groups are lacking. While modern seep decapods are dominated by galatheoid squat lobsters, alvinocaridid shrimps, king crabs, and true crabs, the fossil record is consisting primarily of callianassid ghost shrimps and true crabs thus far. Preservation and recognition are likely to have influenced this discrepancy. Finally, the relatively unexplored fossil record of seep crustaceans provides many opportunities for systematic and paleoecological research.

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