Prehistoric Flora & Fauna


Saturday, March 11, 2017

The early mammals of the late cretaceous were small burrowing creatures, not unlike today’s mice, others growing to a size comparable to modern domestic cats

The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago (Mya) to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era. The Cretaceous Period is usually abbreviated K, for its German translation Kreide (chalk).

Cretaceous Earth

The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, while dinosaurs continued to dominate on land. During this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a large mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs and large marine reptiles died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction which lies between the Mesozoic and Cenozoic eras.

Research history

The Cretaceous as a separate period was first defined by Belgian geologist Jean d’Omalius d’Halloy in 1822, using strata in the Paris Basin and named for the extensive beds of chalk (calcium carbonate deposited by the shells of marine invertebrates, principally coccoliths), found in the upper Cretaceous of Western Europe. The name Cretaceous was derived from Latin creta, meaning chalk.

A timeline of the last 600 million years, showing major events in evolution.

Stratigraphic subdivisions

The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series. In older literature the Cretaceous is sometimes divided into three series: Neocomian (lower/early), Gallic (middle) and Senonian (upper/late). A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide. In many parts of the world, alternative local subdivisions are still in use.

As with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact age of the system’s base is uncertain by a few million years. No great extinction or burst of diversity separates the Cretaceous from the Jurassic. However, the top of the system is sharply defined, being placed at an iridium-rich layer found worldwide that is believed to be associated with the Chicxulub impact crater, with its boundaries circumscribing parts of the Yucatán Peninsula and into the Gulf of Mexico. This layer has been dated at 66.043 Ma.

A 140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a stratigraphic study of Vaca Muerta Formation in Neuquén Basin, Argentina. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a “first step” toward formally changing the age in the International Union of Geological Sciences.

From youngest to oldest, the subdivisions of the Cretaceous period are:

Late Cretaceous

Maastrichtian – (66-72.1 MYA)

Campanian – (72.1-83.6 MYA)

Santonian – (83.6-86.3 MYA)

Coniacian – (86.3-89.8 MYA)

Turonian – (89.8-93.9 MYA)

Cenomanian – (93.9-100.5 MYA)

Early Cretaceous

Albian – (100.5-113.0 MYA)

Aptian – (113.0-125.0 MYA)

Barremian – (125.0-129.4 MYA)

Hauterivian – (129.4-132.9 MYA)

Valanginian – (132.9-139.8 MYA)

Berriasian – (139.8-145.0 MYA)

Rock formations

The high sea level and warm climate of the Cretaceous meant large areas of the continents were covered by warm, shallow seas, providing habitat for many marine organisms. The Cretaceous was named for the extensive chalk deposits of this age in Europe, but in many parts of the world, the deposits from the Cretaceous are of marine limestone, a rock type that is formed under warm, shallow marine circumstances. Due to the high sea level there was extensive space for such sedimentation. Because of the relatively young age and great thickness of the system, Cretaceous rocks are evident in many areas worldwide.

Chalk is a rock type characteristic for (but not restricted to) the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, a type of algae that prospered in the Cretaceous seas.

In northwestern Europe, chalk deposits from the Upper Cretaceous are characteristic for the Chalk Group, which forms the white cliffs of Dover on the south coast of England and similar cliffs on the French Normandian coast. The group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of loose sediments in many places. The group also has other limestones and arenites. Among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus.

In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls. Because the Alpine mountain chains did not yet exist in the Cretaceous, these deposits formed on the southern edge of the European continental shelf, at the margin of the Tethys Ocean.

Stagnation of deep sea currents in middle Cretaceous times caused anoxic conditions in the sea water leaving the deposited organic matter undecomposed. Half the worlds petroleum reserves were laid down at this time in the anoxic conditions of what would become the Persian Gulf and Gulf of Mexico. In many places around the world, dark anoxic shales were formed during this interval. These shales are an important source rock for oil and gas, for example in the subsurface of the North Sea.

During the Cretaceous, the late-Paleozoic-to-early-Mesozoic supercontinent of Pangaea completed its tectonic breakup into the present-day continents, although their positions were substantially different at the time. As the Atlantic Ocean widened, the convergent-margin mountain building (orogenies) that had begun during the Jurassic continued in the North American Cordillera, as the Nevadan orogeny was followed by the Sevier and Laramide orogenies.

Though Gondwana was still intact in the beginning of the Cretaceous, it broke up as South America, Antarctica and Australia rifted away from Africa (though India and Madagascar remained attached to each other); thus, the South Atlantic and Indian Oceans were newly formed. Such active rifting lifted great undersea mountain chains along the welts, raising eustatic sea levels worldwide. To the north of Africa the Tethys Sea continued to narrow. Broad shallow seas advanced across central North America (the Western Interior Seaway) and Europe, then receded late in the period, leaving thick marine deposits sandwiched between coal beds. At the peak of the Cretaceous transgression, one-third of Earth’s present land area was submerged.


The cooling trend of last epoch of the Jurassic continued into the first age of the Cretaceous. There is evidence that snowfalls were common in the higher latitudes and the tropics became wetter than during the Triassic and Jurassic. Glaciation was however restricted to high-latitude mountains, though seasonal snow may have existed farther from the poles. Rafting by ice of stones into marine environments occurred during much of the Cretaceous but evidence of deposition directly from glaciers is limited to the Early Cretaceous of the Eromanga Basin in southern Australia.

A very gentle temperature gradient from the equator to the poles meant weaker global winds, which drive the ocean currents, resulted in less upwelling and more stagnant oceans than today. This is evidenced by widespread black shale deposition and frequent anoxic events. Sediment cores show that tropical sea surface temperatures may have briefly been as warm as 42 °C (108 °F), 17 °C (31 °F) warmer than at present, and that they averaged around 37 °C (99 °F). Meanwhile, deep ocean temperatures were as much as 15 to 20 °C (27 to 36 °F) warmer than today’s.


Flowering plants (angiosperms) spread during this period, although they did not become predominant until the Campanian Age near the end of the period. Their evolution was aided by the appearance of bees; in fact angiosperms and insects are a good example of coevolution. The first representatives of many leafy trees, including figs, planes and magnolias, appeared in the Cretaceous. At the same time, some earlier Mesozoic gymnosperms continued to thrive; pehuéns (monkey puzzle trees, Araucaria) and other conifers being notably plentiful and widespread. Some fern orders such as Gleicheniales appeared as early in the fossil record as the Cretaceous, and achieved an early broad distribution. Gymnosperm taxa like Bennettitales and hirmerellan conifers died out before the end of the period.

Terrestrial fauna

On land, mammals were generally small sized, but a very relevant component of the fauna, with cimolodont multituberculates outnumbering dinosaurs in some sites. Neither true marsupials nor placentals existed until the very end, but a variety of non-marsupial metatherians and non-placental eutherians had already began to diversify greatly, ranging as carnivores (Deltatheroida), aquatic foragers (Stagodontidae) and herbivores (Schowalteria, Zhelestidae). Various “archaic” groups like eutriconodonts were common in the Early Cretaceous, but by the Late Cretaceous northern mammalian faunas were dominated by multituberculates and therians, with dryolestoids dominating South America.

The apex predators were archosaurian reptiles, especially dinosaurs, which were at their most diverse stage. Pterosaurs were common in the early and middle Cretaceous, but as the Cretaceous proceeded they declined for poorly understood reasons (once thought to be due to competition with early birds, but now it is understood avian adaptive radiation is not consistent with pterosaur decline), and by the end of the period only two highly specialized families remained.

Insects diversified during the Cretaceous, and the oldest known ants, termites and some lepidopterans, akin to butterflies and moths, appeared. Aphids, grasshoppers and gall wasps appeared.

Marine fauna

In the seas, rays, modern sharks and teleosts became common. Marine reptiles included ichthyosaurs in the early and mid-Cretaceous (becoming extinct during the late Cretaceous Cenomanian-Turonian anoxic event), plesiosaurs throughout the entire period, and mosasaurs appearing in the Late Cretaceous.

Baculites, an ammonite genus with a straight shell, flourished in the seas along with reef-building rudist clams. The Hesperornithiformes were flightless, marine diving birds that swam like grebes. Globotruncanid Foraminifera and echinoderms such as sea urchins and starfish (sea stars) thrived. The first radiation of the diatoms (generally siliceous shelled, rather than calcareous) in the oceans occurred during the Cretaceous; freshwater diatoms did not appear until the Miocene. The Cretaceous was also an important interval in the evolution of bioerosion, the production of borings and scrapings in rocks, hardgrounds and shells.

End-Cretaceous extinction event

The impact of a large body with the Earth may have been the punctuation mark at the end of a progressive decline in biodiversity during the Maastrichtian Age of the Cretaceous Period. The result was the extinction of three-quarters of Earth’s plant and animal species. The impact created the sharp break known as K–Pg boundary (formerly known as the K–T boundary). Earth’s biodiversity required substantial time to recover from this event, despite the probable existence of an abundance of vacant ecological niches.

Despite the severity of K-Pg extinction event, there was significant variability in the rate of extinction between and within different clades. Species which depended on photosynthesis declined or became extinct as atmospheric particles blocked solar energy. As is the case today, photosynthesizing organisms, such as phytoplankton and land plants, formed the primary part of the food chain in the late Cretaceous, and all else that depended on them suffered as well. Herbivorous animals, which depended on plants and plankton as their food, died out as their food sources became scarce; consequently, the top predators such as Tyrannosaurus rex also perished. Yet only three major groups of tetrapods disappeared completely; the non-avian dinosaurs, the plesiosaurs and the pterosaurs. The other Cretaceous groups that did not survive into the Cenozoic era, the ichthyosaurs and last remaining temnospondyls and non-mammalian cynodonts were already extinct millions of years before the event occurred.

Coccolithophorids and molluscs, including ammonites, rudists, freshwater snails and mussels, as well as organisms whose food chain included these shell builders, became extinct or suffered heavy losses. For example, it is thought that ammonites were the principal food of mosasaurs, a group of giant marine reptiles that became extinct at the boundary.

Omnivores, insectivores and carrion-eaters survived the extinction event, perhaps because of the increased availability of their food sources. At the end of the Cretaceous there seem to have been no purely herbivorous or carnivorous mammals. Mammals and birds which survived the extinction fed on insects, larvae, worms and snails, which in turn fed on dead plant and animal matter. Scientists theorise that these organisms survived the collapse of plant-based food chains because they fed on detritus.

In stream communities, few groups of animals became extinct. Stream communities rely less on food from living plants and more on detritus that washes in from land. This particular ecological niche buffered them from extinction. Similar, but more complex patterns have been found in the oceans. Extinction was more severe among animals living in the water column, than among animals living on or in the sea floor. Animals in the water column are almost entirely dependent on primary production from living phytoplankton, while animals living on or in the ocean floor feed on detritus or can switch to detritus feeding.

The largest air-breathing survivors of the event, crocodilians and champsosaurs, were semi-aquatic and had access to detritus. Modern crocodilians can live as scavengers and can survive for months without food and go into hibernation when conditions are unfavourable, and their young are small, grow slowly, and feed largely on invertebrates and dead organisms or fragments of organisms for their first few years. These characteristics have been linked to crocodilian survival at the end of the Cretaceous.

Source: Wikipedia,


Began: 142 million years ago

Ended: Cretaceous-Tertiary mass extinction
65 million years ago


Saturday, March 11, 2017

Jurassic Landscape by Zdeněk Burian

The Jurassic is a geologic period and system that spans 56.3 million years from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era, also known as the Age of Reptiles. The start of the period is marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian/Toarcian event in the Early Jurassic, and the Tithonian event at the end; however, neither event ranks among the “Big Five” mass extinctions.

The Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, and many of the arid deserts of the Triassic were replaced by lush rainforests.

On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates.

The world, Late Jurassic, 150 Ma, Global Paleogeographic Views of Earth History, NAU

The Jurassic period is divided into the Early Jurassic, Middle, and Late Jurassic epochs. The Jurassic System, in stratigraphy, is divided into the Lower Jurassic, Middle, and Upper Jurassic series of rock formations, also known as LiasDogger and Malm in Europe. The separation of the term Jurassic into three sections goes back to Leopold von Buch. The faunal stages from youngest to oldest are:

Upper/Late Jurassic  
Tithonian (152.1 ± 4 – 145 ± 4 Mya)
Kimmeridgian (157.3 ± 4 – 152.1 ± 4 Mya)
Oxfordian (163.5 ± 4 – 157.3 ± 4 Mya)
Middle Jurassic  
Callovian (166.1 ± 4 – 163.5 ± 4 Mya)
Bathonian (168.3 ± 3.5 – 166.1 ± 4 Mya)
Bajocian (170.3 ± 3 – 168.3 ± 3.5 Mya)
Aalenian (174.1 ± 2 – 170.3 ± 3 Mya)
Lower/Early Jurassic  
Toarcian (182.7 ± 1.5 – 174.1 ± 2 Mya)
Pliensbachian (190.8 ± 1.5 – 182.7 ± 1.5 Mya)
Sinemurian (199.3 ± 1 – 190.8 ± 1.5 Mya)
Hettangian (201.3 ± 0.6 – 199.3 ± 1 Mya)

Triassic-Jurassic Mass Extinction

Saturday, March 11, 2017

The Triassic–Jurassic extinction event marks the boundary between the Triassic and Jurassic periods, 201.3 million years ago, and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas, a whole class (conodonts) and 34% of marine genera disappeared. On land, all archosaurs other than crocodylomorphs (Sphenosuchia and Crocodyliformes) and Avemetatarsalia (pterosaurs and dinosaurs), some remaining therapsids, and many of the large amphibians became extinct.

At least half of the species now known to have been living on Earth at that time became extinct. This event vacated terrestrial ecological niches, allowing the dinosaurs to assume the dominant roles in the Jurassic period. This event happened in less than 10,000 years and occurred just before Pangaea started to break apart. In the area of Tübingen (Germany), a Triassic-Jurassic bonebed can be found, which is characteristic for this boundary.

There are several different hypotheses on what caused this particular mass extinction at the end of the Triassic Period. Since the third major mass extinction actually is thought to have occurred in several small waves of extinctions, it is entirely possible that all of these hypotheses, along with others that may not be as popular or thought of as of yet, could have caused the overall mass extinction event.

There is evidence for all of the causes proposed.

One possible explanation for this catastrophic mass extinction event is unusually high levels of volcanic activity. It is known that large numbers of flood basalts around the Central America region occurred around the time of the Triasssic-Jurassic mass extinction event.


These enormous volcano eruptions are thought to have expelled huge amounts of greenhouse gases like sulfur dioxide or carbon dioxide that would quickly and devastatingly increase the global climate. Other scientists believe it would have aerosols expelled from these volcanic eruptions that would actually do the opposite of the greenhouse gases and end up cooling the climate significantly.

Other scientists believe it was more of a gradual climate change issue that spanned the majority of the 18 million year time span attributed to the end of the Triassic mass extinction. This would have led to changing sea levels and even possibly a change in the acidity within the oceans that would have affected species living there.

End of the Triassic period
Start of the Jurassic period


Saturday, March 11, 2017

Triassic landscape

The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period 252.17 million years ago (Mya), to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events.

The Triassic began in the wake of the Permian–Triassic extinction event, which left the earth’s biosphere impoverished; it would take well into the middle of this period for life to recover its former diversity. Therapsids and archosaurs were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic but did not become dominant until the succeeding Jurassic Period.

Mystriosuchus, a phytosaur specialised to an primarily aquatic lifestyle. By Julio Lacerda

The first true mammals, themselves a specialized subgroup of Therapsids, also evolved during this period, as well as the first flying vertebrates, the pterosaurs, who like the dinosaurs were a specialized subgroup of archosaurs. The vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south.

The global climate during the Triassic was mostly hot and dry, with deserts spanning much of Pangaea’s interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic-Jurassic extinction event, that wiped out many groups and allowed dinosaurs to assume dominance in the Jurassic.

The Triassic was named in 1834 by Friedrich von Alberti, after the three distinct rock layers (tri meaning “three”) that are found throughout Germany and northwestern Europe—red beds, capped by marine limestone, followed by a series of terrestrial mud- and sandstones—called the “Trias”.

Began: Permian mass extinction
248 million years ago

Ended: Triassic-Jurassic mass extinction
205 million years ago

Whale Evolution

Sunday, March 5, 2017

An artist's impression of Professor Hans Thewissen's walking whale, Amulocetus natans.

The evolution of whales

The first thing to notice on this evogram is that hippos are the closest living relatives of whales, but they are not the ancestors of whales. In fact, none of the individual animals on the evogram is the direct ancestor of any other, as far as we know. That’s why each of them gets its own branch on the family tree.

Evogram of whale evolution

Hippos are large and aquatic, like whales, but the two groups evolved those features separately from each other. We know this because the ancient relatives of hippos called anthracotheres (not shown here) were not large or aquatic. Nor were the ancient relatives of whales that you see pictured on this tree — such as Pakicetus. Hippos likely evolved from a group of anthracotheres about 15 million years ago, the first whales evolved over 50 million years ago, and the ancestor of both these groups was terrestrial.

These first whales, such as Pakicetus, were typical land animals. They had long skulls and large carnivorous teeth. From the outside, they don’t look much like whales at all. However, their skulls — particularly in the ear region, which is surrounded by a bony wall — strongly resemble those of living whales and are unlike those of any other mammal. Often, seemingly minor features provide critical evidence to link animals that are highly specialized for their lifestyles (such as whales) with their less extreme-looking relatives.

Compared to other early whales, like Indohyus and PakicetusAmbulocetus looks like it lived a more aquatic lifestyle. Its legs are shorter, and its hands and feet are enlarged like paddles. Its tail is longer and more muscular, too. The hypothesis that Ambulocetus lived an aquatic life is also supported by evidence from stratigraphy — Ambulocetus‘s fossils were recovered from sediments that probably comprised an ancient estuary — and from the isotopes of oxygen in its bones. Animals are what they eat and drink, and saltwater and freshwater have different ratios of oxygen isotopes. This means that we can learn about what sort of water an animal drank by studying the isotopes that were incorporated into its bones and teeth as it grew. The isotopes show that Ambulocetus likely drank both saltwater and freshwater, which fits perfectly with the idea that these animals lived in estuaries or bays between freshwater and the open ocean.

Whales that evolved after Ambulocetus (Kutchicetus, etc.) show even higher levels of saltwater oxygen isotopes, indicating that they lived in nearshore marine habitats and were able to drink saltwater as today’s whales can. These animals evolved nostrils positioned further and further back along the snout. This trend has continued into living whales, which have a “blowhole” (nostrils) located on top of the head above the eyes.

These more aquatic whales showed other changes that also suggest they are closely related to today’s whales. For example, the pelvis had evolved to be much reduced in size and separate from the backbone. This may reflect the increased use of the whole vertebral column, including the back and tail, in locomotion. If you watch films of dolphins and other whales swimming, you’ll notice that their tailfins aren’t vertical like those of fishes, but horizontal. To swim, they move their tails up and down, rather than back and forth as fishes do. This is because whales evolved from walking land mammals whose backbones did not naturally bend side to side, but up and down. You can easily see this if you watch a dog running. Its vertebral column undulates up and down in waves as it moves forward. Whales do the same thing as they swim, showing their ancient terrestrial heritage.

As whales began to swim by undulating the whole body, other changes in the skeleton allowed their limbs to be used more for steering than for paddling. Because the sequence of these whales’ tail vertebrae matches those of living dolphins and whales, it suggests that early whales, like Dorudon and Basilosaurus, did have tailfins. Such skeletal changes that accommodate an aquatic lifestyle are especially pronounced in basilosaurids, such as Dorudon. These ancient whales evolved over 40 million years ago. Their elbow joints were able to lock, allowing the forelimb to serve as a better control surface and resist the oncoming flow of water as the animal propelled itself forward. The hindlimbs of these animals were almost nonexistent. They were so tiny that many scientists think they served no effective function and may have even been internal to the body wall. Occasionally, we discover a living whale with the vestiges of tiny hindlimbs inside its body wall.

This vestigial hindlimb is evidence of basilosaurids’ terrestrial heritage. The picture below on the left shows the central ankle bones (called astragali) of three artiodactyls, and you can see they have double pulley joints and hooked processes pointing up toward the leg-bones. Below on the right is a photo of the hind foot of a basilosaurid. You can see that it has a complete ankle and several toe bones, even though it can’t walk. The basilosaurid astragalus still has a pulley and a hooked knob pointing up towards the leg bones as in artiodactyls, while other bones in the ankle and foot are fused. From the ear bones to the ankle bones, whales belong with the hippos and other artiodactyls.

Original article appeared on


Human Origin Traced to Worm Which Swam 0.5 Billion Years Ago

Sunday, December 18, 2016


Paleontologists claim to have tracked the origins of humans and other vertebrates to a worm that swam in today’s Canada. The team concluded that the extinct Pikaia gracilens is the most primitive known member of the chordate family.

Scale diagram of various Burgess Shale invertebrates, P. gracilens in yellow. Author: Matt Martyniuk (Dinoguy2)

The chordate family includes fish, amphibians, birds, reptiles and mammals – pretty much all of what we consider to be ‘evolved’ life, so tracing its origins would be quite a big deal. This is why Simon Conway Morris of the Cambridge University went to Canada to analyze fossils from the Canadian Rockies.

His findings were published in the British scientific journal Biological Reviews; he identified a notochord or rod that would become part of the backbone in vertebrates, and skeletal muscle tissue called myomeres in 114 fossil specimens of the creature, as well as a vascular system.

“The discovery of myomeres is the smoking gun that we have long been seeking,” said the study’s lead author, Simon Conway Morris of the Cambridge University. “Now with myomeres, a nerve chord, a notochord and a vascular system all identified, this study clearly places Pikaia as the planet’s most primitive chordate. “So, next time we put the family photograph on the mantle-piece, there in the background will be Pikaia.”

The first members of Pikaia were discovered in 1911, but back then the animals were dismissed as ancestors of worms or eels, and it wasn’t until 1970 that Morris suggested the five-centimeter sideways flattened animal could be our ancestor.

“In particular, it was our use of an electron microscope that allowed us to see very fine details of its anatomy,” Jean-Bernard Caron, an assistant professor of ecology and evolutionary biology at the University of Toronto and the study’s co-author, told AFP.

Finding out that all the animal diversity we see today can be traced to this simple animal puts a lot of things into perspective, and, as Caron says, it’s really humbling.

“It’s very humbling to know that swans, snakes, bears, zebras and, incredibly, humans all share a deep history with this tiny creature no longer than my thumb,” he said.


26 Strangest Prehistoric Creatures

Friday, December 16, 2016


Paleontologists, scientists and other researchers have collected enough samples over the years to form some pretty solid theories about what kinds of creatures used to roam this earth. If you’ve ever seen Jurassic Park or have been to a natural history museum, you’d know that life here used to consist of three things: huge monsters, dangerous plants and quick deaths. These 26 creatures used to roam the very ground you walk on today. You’ll be so glad they aren’t around any more…

Microraptor: Its name means “one who seizes.” It was a very small dinosaur and paleontologists have long debated the use of its four wings.

Restoration with colouration based on fossilized melanosomes by Durbed

Nyctosaurus: This ancient genus of Pterorsaur was found in the Mid-western sections of the US. The name means “naked reptile.”

Opabinia: This is one of the strangest creatures that ever lived. It had 30 flippers, 30 legs, a trunk-like nose and one lobster claw.

Scale diagram of various Burgess Shale invertebrates, Opabinia in green by Dinoguy2

Phorusrhacidae: People know this creature as the “terror bird.” It was one of the largest predatory birds that ever lived and could run at speeds up to 40mph.

Pterodaustro: Also known as the Pterosaurs, it had a wingspan of 4 feet. It’s bristle-like teeth implies it probably fed on a diet of plankton and small crustaceans.

Quetzalcoatlus: This was the largest pterosaur in the sky, as big is a common African giraffe. Its wingspan was 30 whole feet.

Sharovipteryx: Ths gliding reptile, found in Central Asia, was about one foot long. It would feed on insects and wasn’t capable of powered flight, it would just glide.

Life reconstruction of Sharovipteryx mirabilis by Dmitry Bogdanov

Stethacanthus: A type of extinct prehistoric shark, they would grow up to 6 feet long with a strange looking back growth on males.

Tanystropheus: Its name means “long necked one” and the prehistoric reptile was easily over 20 feet long.

Therizinosauridae: Or “reaper lizard,” may have been found in Mongolia, China, and the United States. Because they had long necks, pot bellies, four-toed feet, and beaky mouth, scientists weren’t sure if their parts belonged to one creature or several.

Archaeopteryx: The “first bird” supposedly existed during the Jurassic period, discovered in Germany in 1861.

Exhibit – Archaeopteryx Diorama. Photo by NationalDinosaurMuseum

Deinocheirus: There are only a handful of fossil remains of this creature, including two forelimbs and some vertebrae. Its name means “terrible hands.”

Deinotherium: The “hoe tusker” resembled a modern day elephant and were discovered at major hominid extinction sites at Lake Turkana in Kenya.

Dimorphodon: This flying creature had two distinct types of teeth in its jaw. It had great eyesight and huge claws for hunting.

Dunkleosteus: Or “Dunkle’s bone,” was one of the largest armored jaw fishes that ever existed. It was one of the fiercest predators in the ocean. It could be up to 10 meters long and weighed 3.6 tons.

Dunkleosteus by NTamura on Deviantart

Elasmosaurus: This creature could be up to 46 feet in length (with most of its length in its neck). Its neck was 4x larger than a giraffe’s.

Epidendrosaurus: This was the first reptile to be closer ro a bird than a dinosaur. It was about 6 inches long, with clawed hands on its arms/wings.

Epidexipteryx: These small, feathered dinosaurs were found in the Inner Mongolia region of China. Their large display feathers were the earliest known representation of ornamental feathers in the fossil record.

Hallucigenia: A relative of modern arthropods, Hallucigenia is a strange creature only 3 millimeters long. It has a bulbous round head connected to its cylindrical trunk. It was an ancestor of today’s velvet worms.

Helicoprion: Also known as “spiral saw,” this shark-like cartilaginous fish appeared in the late Carboniferous era. The only evidence of its existence was a curled-up coil of triangular teeth. Some scientists think that it was used to grind shells, while others believed it to be a weapon.

Restoration of H. bessonovi by Nobu Tamura

 Jaekelopterus: This sea scorpion was massive, at an estimated length of 2.5 meters. It was one of the largest arthropods ever discovered. It supposedly STILL exists in present day freshwater rivers and lakes in Germany.

Josephoartigasia: This capybara-like animal was the biggest rodent on the planet, weighing up to 1000kg.

Liopleurodon: This marine predator lived on a diet of fish, squid, and other sea reptiles. It was bigger than a sperm whale and its skull was nearly 1/4 of its body, filled with many smooth teeth.

Longisquama: This creature was known as the first archosaur to have been able to glide or parachute. It is known for its elongated pair of scales along its back, with the anterior ones resembling feathers.

Megalania: Otherwise known as the giant ripper lizard, it fed on a diet of mammals, snakes, other reptiles, and birds. A modern day relative would be the Komodo dragon that inhabits the Flores Islands in Indonesia.

Megalania skeletal reconstruction on Melbourne Museum steps. Photo by Cas Liber

Platybelodon (cover pic): ("flat-spear tusk") was a genus of large herbivorous mammal related to the elephant (order Proboscidea). It lived during the late Miocene Epoch in Asia and the Caucasus.


Mesozoic Era: Age of the Dinosaurs

Wednesday, December 7, 2016

The Mesozoic Era: When Dinosaurs Ruled the Earth

During the Mesozoic, or “Middle Life” Era, life diversified rapidly and giant reptiles, dinosaurs and other monstrous beasts roamed the Earth. The period, which spans from about 252 million years ago to about 66 million years ago, was also known as the age of reptiles or the age of dinosaurs.

Life Through Time: Mesozoic era


English geologist John Phillips, the first person to create the global geologic timescale, first coined the term Mesozoic in the 1800s. Phillips found ways to correlate sediments found around the world to specific time periods, said Paul Olsen, a geoscientist at the Lamont-Doherty Earth Observatory at Columbia University in New York.

The Permian-Triassic boundary, at the start of the Mesozoic, is defined relative to a particular section of sediment in Meishan, China, where a type of extinct, eel-like creature known as a conodont first appeared, according to the International Commission on Stratigraphy.

The end boundary for the Mesozoic Era, the Cretaceous-Paleogene boundary, is defined by a 20-inch (50 centimeters) thick sliver of rock in El Kef, Tunisia, which contains well-preserved fossils and traces of iridium and other elements from the asteroid impact that wiped out the dinosaurs. The Mesozoic Era is divided up into the Triassic, Jurassic, and Cretaceous periods.

New research suggests that reptiles that lived during the Dinosaur age were hard-hit. Here, the carnivorous lizard Palaeosaniwa chases a pair of young Edmontosaurus while the snake Cerberophis and the lizard Obamadon look on. Credit: Carl Buell

Life and climate

The Mesozoic Era began roughly around the time of the end-Permian extinction, which wiped out 96 percent of marine life and 70 percent of all terrestrial species on the planet. Life slowly rebounded, eventually giving way to a flourishing diversity of animals, from massive lizards to monstrous dinosaurs.

The Triassic Period, from 252 million to 200 million years ago, saw the rise of reptiles and the first dinosaurs, the Jurassic Period, from about 200 million to 145 million years ago, ushered in birds and mammals, and the Cretaceous Period, from 145 million to 66 million years ago is known for some of its iconic dinosaurs, such as Triceratops and Pteranodon.

Coniferous plants, or those that have cone-bearing seeds, already existed at the beginning of the era, but they became much more abundant during the Mesozoic. Flowering plants emerged during the late Cretaceous Period. The lush plant life during the Mesozoic Era provided plenty of food, allowing the biggest of the dinosaurs, such as the Argentinosaurus, to grow up to 80 tons, according to a 2005 study in the journal Revista del Museo Argentino de Ciencias Naturales.

Earth during the Mesozoic Era was much warmer than today, and the planet had no polar ice caps. During the Triassic Period, Pangaea still formed one massive supercontinent. Without much coastline to moderate the continent’s interior temperature, Pangaea experienced major temperature swings and was covered in large swaths of desert. Yet the region still had a belt of tropical rainforest in regions around the equator, said Brendan Murphy, an earth scientist at St. Francis Xavier University in Antigonish, Canada.


The Mesozoic Era was bookended by two great extinctions, with another smaller extinction occurring at the end of the Triassic Period, Olsen said.

Around 252 million years ago, the end-Permian extinction wiped out most life on Earth over about 60,000 years, according to a February 2014 study in the journal Proceedings of the National Academy of Sciences (PNAS). At the end of the Triassic Period, roughly 201 million years ago, most amphibious creatures and crocodile-like creatures that lived in the tropics were wiped out. About 65 million years ago, a giant asteroid blasted into Earth and formed a giant crater at Chicxulub in the Yucatan Peninsula.

Because the fossil record is incomplete, it’s difficult to say exactly what caused the extinctions, or even how rapidly they occurred. After all, certain species or traces of catastrophic events could be missing in the fossil record simply because the sediments may have disappeared over tens of millions of years, Olsen said.

“Nature is very efficient at getting rid of its corpses,” Olsen told Live Science.

However, there are a few prime suspects in each of the extinctions.

At the end of the Permian, the Siberian Traps underwent massive volcanic eruptions, which most geologists believe caused the world’s biggest extinction. Exactly how, however, is up for debate.

The volcanic eruptions caused a spike in carbon dioxide in the atmosphere, though the 2014 PNAS study suggests that the spike was brief. The eruptions may have increased sea surface temperatures and led to ocean acidification that choked out sea life. And another study published in March 2014 in PNAS proposed that the eruptions released huge troves of the element nickel, which fueled a feeding frenzy by nickel-munching microbes known as Methanosarcina. Those microbes may have belched out huge amounts of methane, superheating the planet.

Most scientists agree that an asteroid impact wiped out the dinosaurs at the end of the Cretaceous Period. The impact would have kicked up so much dust that it blocked the sun, halted photosynthesis, and led to such a huge disruption in the food chain that everything that wasn’t a scavenger or very small died.

But the Deccan Traps, in what is now India, were spewing massive amounts of lava both before and after the asteroid impact, and a few scientists believe these flows either directly caused or accelerated the dinosaurs’ demise.

Volcanism may also be to blame for the end-Triassic extinction. Though volcanism in general leads to global warming, after an initial volcanic eruption, huge amounts of sulfur spew into the air and cause a brief period of global cooling. Such cooling-heating cycles may have occurred hundreds of times over 500,000 years. Similar cold snaps have been tied to huge crop failures in historical times, such as in Iceland in the 1700s, Olsen said.

As a result, animals used to constant, balmy temperatures in the tropics were wiped out, while animals that were insulated with proto-feathers, such as pterosaurs, or that lived at higher latitudes and were already adapted to big temperature variations, did just fine, Olsen said.

“When you have these volcanic winters, where temperatures may have dropped even below freezing in the tropics, it was devastating,” Olsen said.


Tetrapods: Natural Antacid Helped Early Land Creatures Breathe

Wednesday, December 7, 2016

In Late Devonian vertebrate speciation, descendants of pelagic lobe-finned fish — like Eusthenopteron — exhibited a sequence of adaptations: *Panderichthys, suited to muddy shallows *Tiktaalik with limb-like fins that could take it onto land *Early tetrapods in weed-filled swamps, such as: **Acanthostega, which had feet with eight digits **Ichthyostega with limbs Descendants also included pelagic lobe-finned fish such as coelacanth species.

The earliest creatures to crawl out of the water onto land may have concocted antacids out of their own bones, a clever innovation that would’ve let the animals breathe, researchers now find.

The earliest tetrapods, or four-limbed creatures, made their first evolutionary forays onto land about 370 million years ago. Breathing air came with challenges, though. A major one was getting rid of the air’s carbon dioxide, which, when it builds up, reacts with water in the body and forms an acid.

Now, growing evidence in modern reptiles suggests that bones that grew within the skin of early tetrapods may have acted as a natural antacid by releasing their neutralizing chemicals into the bloodstream. The result would have bought the creatures time to spend on land before they had to head back to the water to rid themselves of excess carbon dioxide.

“Now we know that dermal bone can do this and it’s something we didn’t know before, that gives us a basis that maybe this is why tetrapods had this feature, which previously we didn’t have a good explanation for,” study researcher Christine Janis, a paleontologist at Brown University, told LiveScience. “It’s the discovery of this new feature of the physiology of these living animals that lets us go back [in time].”

First on land

So let’s rewind the clock: The first tetrapods evolved from fish in the Devonian period, which spanned from about 416 million years ago to 359 million years ago. These early tetrapods had broad faces, not unlike frogs, and rather immobile ribcages. That means they wouldn’t have been able to get rid of extra carbon dioxide by breathing quickly, as humans and other mammals do with their longer snouts and flexible ribcages. Nor were the tetrapods small enough to exchange carbon dioxide and oxygen via their skin, as modern amphibians do.

An illustration of what the sea creature Tiktaalik may have looked like. Known as a "fishapod," Tiktaalik bridged the gap between sea living and land living creatures, and played an important evolutionary role on our journey to becoming human. Zina Deretsky/National Science Foundation

What tetrapods did have was complex “dermal bone,” or bone that forms from connective tissue in the skin instead of from cartilage like the long bones of the arm or leg. The concept of skin bone may seem strange, but it’s very common: The human skull, for example, is a dermal bone.

Early tetrapod bone showed many pits and furrows, indicating lots of blood supply, Janis said. Her colleagues, including paper co-author and biologist Daniel Warren of Saint Louis University, had found another piece of the puzzle: In modern turtles and alligators, this dermal bone helps the reptiles tolerate carbon dioxide buildup when they’re under water, unable to breathe.

Bone breathing

Tetrapods would have the opposite problem, Janis realized: They’d be able to release carbon dioxide through their skin while in the water, since their skin was more permeable than an alligator’s tough hide. But out on land, they’d need another means of release. It seemed very possible that tetrapods could have used their complex dermal bones as a storage unit for calcium and other acid-neutralizing minerals, releasing them as needed when body acid levels got too high, Janis said.

To test the idea, the researchers analyzed the skeletons of tetrapods. As you might expect, the tetrapods known by the skeletons to spend more time out of the water had the most complex dermal bones. The evolutionary history of the animal supports the hypothesis, as well.

“When [the dermal bone] gets lost, it gets lost in the lineage leading to modern reptiles when they start getting more mobile ribs,” Janis said.

She and her colleagues reported their work Tuesday (April 24) in the journal Proceedings of the Royal Society B.

End of the early tetrapods

While the evidence is consistent with Janis’ theory, there’s no proof yet that tetrapods really used their bones in this way. The next step, Janis said, will be to look for chemical or other clues in modern reptiles who use their bones as antacid. If any telltale signs are established, researchers can then hunt for the same signals in ancient tetrapods.

The terrestrial tetrapods studied by Janis and her colleagues went extinct during the Permian period 299 million to 251 million years ago. It was a changing world, Janis said, and atmospheric carbon dioxide was increasing. It’s possible that tetrapods’ bone-dependent breathing wasn’t as effective in this new atmosphere.

“Who knows?” Janis asked. “I think the point to make is that this was probably a perfectly good way to live for awhile — millions of years — but in the end, there were things that had figured out better ways of how to get rid of carbon dioxide.”



Wednesday, December 7, 2016

Trilobites - Ehmania sp. by Onikaizer

Trilobites are distant relatives of lobsters, spiders and insects that died off more than 250 million years ago, before the dinosaurs even came into existence. They prowled the seas for roughly 270 million years, longer than the Age of Dinosaurs, and new species of trilobites are unearthed every year, making them the single most diverse class of extinct life known.

Tiny Orgy: Billions of Beasts Fossilized in Act of ‘Naked’ Sex

Orgies of sometimes billions of trilobites have been discovered, ones captured in a torrent of mud right after these extinct creatures ditched their hard shells to get up close and personal.

These findings, which will be presented March 20 at the Geological Society of America regional meeting in Pittsburgh, help show how social these ancient beasts were.

A group of trilobites fossilized after being trapped in mud in what is now western New York. Credit: Carlton Brett

A key problem when it comes to investigating any extinct creature is deducing how it might have once behaved. Now scientists are unearthing mass graves of trilobites, revealing details regarding how they acted in groups.

Mating madness

Trilobites, like other arthropods, shed their hard exoskeletons from time to time in order to grow larger. They appeared to have gathered in large groups for safety in numbers when they molted their armor, just like modern crabs and lobsters.

Moreover, trilobites seem to have used these gatherings as opportunities to mate, just like many of their distant living relatives do. Preserved together are large groups of similar-sized and therefore similarly aged trilobites, separated by species; they may have reproduced essentially “naked” after molting.

“It’s an orgy,” said researcher Carlton Brett, an invertebrate paleontologist and sedimentary geologist at the University of Cincinnati.

The first hints that Brett and his then-graduate student Stephen Speyer had that such orgies took place were actually discovered about two decades ago in 385-million-year-old rocks in New York. Since then, a lot of new material has come into light that strengthened those claims — in 390-million-year-old rocks in Germany, 400-million-year-old sites in Morocco, 450-million-year-old groups near Cincinnati, and up to 470-million-year-old areas holding remains of trilobite orgies in Oklahoma.

“The fact that you can find this in many different places and ages among many different species of trilobites suggests that this behavior might have been pretty general to the entire group, and that it likely began fairly early on in the evolution of trilobites,” Brett told LiveScience.

“There were different groups segregated by species at these sites, yet they all seemed to be molting in synchrony — this is something we see today in modern marine animals as well,” Brett said. “They may have spawned in response to some external trigger from the environment, such as a new moon tide in a particular season of the year.”

Head to tail

Graduate student Adrian Kin of Jagiellonian University in Krakow, Poland, also recently discovered long chains of more than a dozen trilobites arranged head to tail in 360-million-year-old rocks in the Holy Cross Mountains of Poland. This seems to be evidence of another behavior seen in their living relatives — migration.

“The recent discovery of rows of more than a dozen specimens provides the oldest evidence of migratory queues similar to those seen in modern crustaceans,” Brett said.

A chain of trilobites preserved in Poland’s Holy Cross Mountains. Credit: Adrian Kin

“These trilobites were blind, eyeless,” Brett added. “They lived in relatively deep and probably no-light zones. They were probably relying on their tactile senses to literally keep in touch with each other as they migrated.”

These cases of mass burials may have occurred when runoff from hurricanes propelled tons of mud over the trilobites. These catastrophic deposits smothered the creatures so rapidly that they were delicately preserved in the last positions they held when they were alive, essentially recording snapshots of their behavior much the way ancient Roman life was recorded at Pompeii by volcanic ash.

“We find trilobite beds that we can trace across distances of 80 miles (130 kilometers), all the effect of a single event,” Brett said. “The numbers of individuals caught in those must easily be in the billions. These were probably extraordinarily rare events in terms of human scales, but on the grand scale of geological time, you can have a number of these extraordinarily bad days that record these amazing glimpses into what the lives of ancient organisms were like.”