WFS

Why Did Mammals Survive the ‘K/T Extinction’?

September 1st, 2012

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Picture a dinosaur. Huge, menacing creatures, they ruled the Earth for nearly 200 million years, striking fear with every ground-shaking stride. Yet these great beasts were no match for a 6-mile wide meteor that struck near modern-day Mexico 65 million years ago, incinerating everything in its path. This catastrophic impact — called the Cretaceous-Tertiary or K/T extinction event — spelled doom for the dinosaurs and many other species. Some animals, however, including many small mammals, managed to survive.

How did they do it?

“They were better at escaping the heat,” said Russ Graham, senior research associate in geosciences at Penn State. “It was the huge amount of thermal heat released by the meteor strike that was the main cause of the K/T extinction.”

K T Extinction boundary

He said underground burrows and aquatic environments protected small mammals from the brief but drastic rise in temperature. In contrast, the larger dinosaurs would have been completely exposed, and vast numbers would have been instantly burned to death.

K T Extinction boundary

After several days of searing heat, the earth’s surface temperature returned to bearable levels, and the mammals emerged from their burrows, but it was a barren wasteland they encountered, one that presented yet another set of daunting conditions to be overcome, Graham said. It was their diet which enabled these mammals to survive in habitats nearly devoid of plant life.

“Even if large herbivorous dinosaurs had managed to survive the initial meteor strike, they would have had nothing to eat,” he said, “because most of the earth’s above-ground plant material had been destroyed.”

Mammals, in contrast, could eat insects and aquatic plants, which were relatively abundant after the meteor strike. As the remaining dinosaurs died off, mammals began to flourish. Although representatives from other classes of animals also survived the K/T extinction — crocodiles, for instance, had the saving ability to take to water — mammals were clearly the main beneficiaries and they have since spread to nearly every corner of the planet.

Comparative cranial morphology of Recent and fossil turtles

August 31st, 2012

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Comparative descriptions of the cranial morphology in living and extinct turtles are presented in this paper. Descriptions are arranged by bone rather than by taxon and attempt to document the types and degrees of differences in cranial structures within the Testudines, emphasizing features of systematic interest. Developmental information is also included. 273 figures supplement the text. About half of these figures show detailed internal morphology and include comparative series showing horizontal and sagittal sections, and oblique views of ear regions for each of the living families of turtles as well as for those extinct families where this information is available. Additional figures, some of which are taken from the literature, show disarticulated elements, inner ear regions, arterial and nerve foramina and canals, and basicranial morphology. The other half of the figures are dorsal, lateral, and ventral views (also occipital views in many cases) of the skull in nearly all living genera of turtles and many extinct genera. The higher category classification used is that developed by Gaffney (1975d) and no taxonomic novelties are announced. A section of text provides a brief literature revew of chelonian systematics and cranial morphology and a listing (by family) of useful turtle skull illustrations from the literature. A revised glossary of anatomical terms and an index are included”–P. 69.

Source: Authors (Gaffney, Eugene S.) Bulletin of the AMNH: V.164, Article 2

BIRDS LIVED ALONGSIDE DINOSAURS

August 31st, 2012

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An enormous prehistoric bird, which might have resembled a very big ostrich, lived alongside dinosaurs around 83 million years ago, according to new research.

The bird, called Samrukia nessovi after the mythical Kazakh Phoenix, lived in what is now Kazakhstan. It is described in the latest Royal Society Biology Letters.

ancient birds

The discovery confirms “that big birds were living alongside Cretaceous non-avian dinosaurs,” lead author Darren Naish said. “In fact, these big birds fit into the idea that the Cretaceous wasn’t ‘a non-avian dinosaurs-only theme park.’ Sure, non-avian dinosaurs were important and big in ecological terms, but there was at least some space for other land animals.”

Naish is an honorary research associate in the School of Earth & Environmental Sciences at the University of Portsmouth. He and his team made the discovery after analyzing the fossil for Samrukia, which previously had been modified by someone to resemble an oviraptorosaur (a type of feathered dinosaur).

All that’s left of this big bird is its toothless lower jaw. The structure and characteristics of the jaw are associated with birds and not non-avian dinosaurs, the researchers believe.

They conclude that the skull of the bird during its lifetime would have been about a foot long. If flightless, it could have stood close to 10 feet tall. If it flew, its wingspan is likely to have exceeded 13 feet.

The big bird is now the second known large avian from the dinosaur era. The first to be identified wasGargantuavis philoinos, which lived in southern France around 70 million years ago. It too may have been flightless and ostrich-like.

“So we can now be really confident that Mesozoic terrestrial birds weren’t all thrush-sized or crow-sized animals,” Naish said. “Giant size definitely evolved in these animals, and giant forms were living in at least two distinct regions. This fits into a larger, emerging picture: Mesozoic birds were ecologically diverse, with lots of overlap between them and modern groups.”

During its day, Samrukia existed in an ecosystem that included armored dinosaurs, duckbilled dinosaurs, and tyrannosaurs — along with other predatory dinos. Smaller birds are also known from this site, called the Bostobynskaya Formation. Sharks, turtles and salamanders from the bird’s time period have also been found in the region.

At present, the site is dry and hot. It’s dominated by semi-desert or scrub. Back in the dinosaur era, it was more of a floodplain environment, with a flat plain crisscrossed by big, meandering rivers. Fossil wood suggests forests were nearby.

It remains unclear what the big bird hunted, but the researchers could not find any evidence for obvious specialization, such as dedication to plant consumption or aquatic prey. They therefore suspect it was a generalist, per many modern birds today.

The bird probably also spent a lot of time running or flying away from the numerous meat-eating dinosaurs from the area.

Such distinctions were obviously important to the animals at the time, but paleontologists now must tease apart birds from non-avian dinosaurs. In the case of this latest discovery, a fossil attributed to a dinosaur was determined to be a bird. Recently, however, the supposed “world’s oldest known bird,” Archaeopteryx, was found to be a non-avian dinosaur. Naish and his team agree with that assessment.

Lawrence Witmer, a professor of anatomy and paleontology at Ohio University, told Discovery News, “We scientists use the cumbersome and seemingly pedantic ‘non-avian dinosaurs’ (term), but back about 150 million years ago, all these groups were extremely similar. They all kind of looked like feathered dino-birds.”

As Naish points out, though, the new findings about Samrukia demonstrate that modern birds “weren’t as distinct from extinct groups of Mesozoic birds as people used to think.”

Admiring today’s birds therefore provides a hint about what avian diversity looked like millions of years ago, when non-avian dinosaurs were still alive and may have been feasting on these early birds.

WFS Dinosaur Diary : Sinocalliopteryx

August 30th, 2012

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Sinocalliopteryx (meaning ‘Chinese beautiful feather’) is a genus of carnivorous ciomsognathid theropod dinisaurs from the lower Cretaceous Yixian Formation if China (Jianshangou Beds, dating to 124.6 Ma).

Sinocalliopteryx

While similar to the related Huaxiagnathus, Sinocalliopteryx were larger, and at 2.37 meters (7.78 ft) in length, includes the largest known compsognathid specimen.

Sinocalliopteryx was a bipedal predator. The preserved length of the holotype specimen is 237 centimetres. Its weight was estimated by Gregory S. Paul in 2010 at twenty kilogrammes. Sinocalliopteryx is distinguished from Huaxiagnathus, as well as other compsognathids, by its relatively long hands in relation to its arms. The arms and hindlimbs were also longer overall than in other compsognathids, a feature possibly related to its size.

Sinocalliopteryx had an elongated head with a pointed snout, showing a convex upper profile. There were four teeth in the premaxilla which were small but exceptionally had denticles on their front edges. Only six, larger, teeth were present in the maxilla. The jugal was a strongly built element with a high-rising front branch that formed part of the lower front edge of the eye socket. The lower jaw lacked an opening in its outer side.

The vertebral column consisted of eleven cervical, twelve dorsal, five sacral and at least forty-nine caudal vertebrae. The point of the tail is missing. In the tail, the spines and chevrons strongly inclined to the back. The gastralia had very short lateral segments.

The arm had a short humerus and also the lower arm was short and elegant with an ulna showing only a weakly developed olecranon process on its back upper end. The hand was very elongated though, as long as the ulna and upper arm combined. The second metacarpal was expanded at the top at the side of the first metacarpal, making the entire metacarpus more compact. The second claw was elongated, as long as the thumb claw. The third metacarpal was rather short and carried a thin, third, finger.

In the pelvis there was a little notch in the front edge of the ilium. The relatively long shaft of the ischium curved downwards. The hindlimb was elongated, largely because of a long lower leg, having 90% of the length of the thighbone. The foot was also long, especially in the metatarsus.

Like many other theropods of the Yixian Formation, Sinocalliopteryx was preserved with “protofeathers,” simple filamentous integument (hairlike structures covering the skin), very similar to that found in Sinosauropteryx. The integument of Sinocalliopteryx differ in length across the body, with the longest protofeathers covering the hips, base of the tail, and back of the thighs. These longest protofeathers measured up to ten centimeters (4 in) in length. Interestingly, protofeathers were also found on the metatarsus (upper part of the foot). While these were not nearly as long or modern as the corresponding feathers of “four-winged” dinosaurs such as Microraptor and Pedopenna, they do indicate that foot-feathers or similar structures first arose in dinosaurs much more basal or “primitive” than previously known.

Discovery and Naming:

The type species Sinocalliopteryx gigas was named and described in 2007 by Ji Shu’an, Ji Qiang, Lü Junchang and Yuan Chongxi. The generic name is derived from Sinae, Latin for the Chinese and Greek καλός, kalos, “beautiful”, and πτέρυξ, pteryx, “feather”. The large size of this “giant compsognathid” lent Sinocalliopteryx its specific name, gigas, meaning ‘giant’.The holotype, JMP-V-05-8-01, was discovered at Hengdaozi, in Sihetun, in Liaoning Province,

holotype

from the Jianshangou Beds of the Yixian Formation dating from the Barremian–Aptian, about 125 million years old. It consists of a nearly complete skeleton with skull, compressed on a single plate, of an adult individual. Extensive remains of protofeathers have been preserved.

fossil specimen Sinocalliopteryx

Sinocalliopteryx was by its describers assigned to the Compsognathidae.

This cladogram shows the position of Sinocalliopteryx in the Compsognathidae according to a study by Cristiano dal Dasso e.a. in 2011:

Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
clade:	Dinosauria
clade:	Theropoda
Family:	†Compsognathidae
Genus:	†Sinocalliopteryx Ji et al., 2007
Species:	†S. gigas

The large size of Sinocalliopteryx compared to its relatives is also notable, and may indicate a trend towards large size among compsognathids (a group well known for their small size compared to other, giant theropod dinosaurs), similar to the trends towards larger sizes in other dinosaurian lineages.

The well-preserved skeleton of Sinocalliopteryx contained the partial leg of a Sinornithosaurus within the abdominal cavity, comprising a complete lower leg and foot with toes and claws in their natural, articulated position. While the leg part, about one foot long, is very large in relation to the abdominal cavity, it is clearly situated within it, lying between the ribs. Ji and colleagues in 2007 suggested that this could indicate it preyed upon the smaller, bird-like dinosaur. This discovery indicated that Sinocalliopteryx may have been an agile, active, “fierce” predator, especially since other compsognathids have been found with (presumably fast-moving) lizards and small mammals in their abdominal cavities.

In addition to the dromaeosaurid leg, four irregularly-shaped stones with a diameter between fifteen and twenty millimetres were found in the abdomen, with no similar stones present in any other portions of the skeleton or embedded in the surrounding rock. The authors interpreted these as gastroliths (gizzard stones) similar to those found with Nqwebasaurus and Baryonyx. Other theropods, such as Caudipteryx and a Mongolian ornithomimid, were also found with gastoliths, though in those cases the stones were much more numerous and smaller in size. Ji and colleagues speculated that, since the later two dinosaurs were probably primarily herbivores, the number and size of gastroliths may correspond with diet; that is, herbivores ingested many small stones, while carnivores ingested only a few larger stones to aid in digestion.

Ref: Wikipedia Article

Researchers discover fossils inside T. Rex ancestor

August 30th, 2012

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A rare dino-fossil has led researchers at the University of Alberta to a discovery they say may forever change the way the Cretaceous period is looked at.

After unearthing two well preserved fossils from China’s Liaoning province, researchers have been able to get a more clear grasp of the eating habits of Sinocalliopteryx, a feathered, flightless, dinosaur they say is an ancestor of the Tyrannosaurus Rex.

“This shows that some dinosaurs, like modern day animals, may have been specialized to hunt certain types of prey,” grad student Scott Persons said.

His team found remains of primitive birds and a Sinornithosaurus, part of the raptor family, inside two fossilized Sinocalliopteryx.

“This tells us about the very interesting habitat from China at the time, it was a wooded environment and in this environment there were lots of animals climbing around in the trees.”

The Sinocalliopteryx is believed to be a feathered dinosaur that could grow up to 2.5 metres in length, and due to its inability to fly or climb, would have had to use stealth to stalk its flying prey.

Researchers said this is the first time one predator has been linked to the killing of multiple flying dinosaurs.

It is also the first confirmed case of a raptor being another meat-eaters meal, Persons said.

fossils

“These are beautifully preserved fossils,” Persons said.

“Underneath we can see the rib cage, and we can see these birds preserved over top of one set of ribs, and underneath another, literally inside the rib cage.”

Although the dinosaurs in question aren’t the ones that everyone is familiar with, Persons said understanding their habitat is hugely important in understanding the habitat of some of the more famous prehistoric giants.

“When people think of dinosaurs everyone likes to think of the clash of the titans, the T. Rex versus the Triceratops,” Persons said.

“These animals are the precursors to some of the more well known dinosaurs that we saw in Jurassic Park. What we have here is the ecosystem that is made up of their ancestors.”

Persons said it is impossible to tell what killed the two Sinocalliopteryx, but that shortly after they died, they were enveloped in volcanic ash, which caused the “beautiful” preservation.

“We are very lucky, both these specimens died very shortly after getting their last meal,” Persons said.

“I would argue that one of our Sinocalliopteryx, the one with the raptor, may be the best specimen that has ever been found.”

Persons and his team hope that this discovery leads to more of its kind, and to a better understanding of ancient habitats.

New theory on the origin of primates

August 29th, 2012

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A new model for primate origins is presented in Zoologica Scripta, published by the Norwegian Academy of Science and Letters and The Royal Swedish Academy of Sciences. The paper argues that the distributions of the major primate groups are correlated with Mesozoic tectonic features and that their respective ranges are congruent with each evolving locally from a widespread ancestor on the supercontinent of Pangea about 185 million years ago.

primates evolution

Michael Heads, a Research Associate of the Buffalo Museum of Science, arrived at these conclusions by incorporating, for the first time, spatial patterns of primate diversity and distribution as historical evidence for primate evolution. Models had previously been limited to interpretations of the fossil record and molecular clocks.

“According to prevailing theories, primates are supposed to have originated in a geographically small area (center of origin) from where they dispersed to other regions and continents” said Heads, who also noted that widespread misrepresentation of fossil molecular clocks estimates as maximum or actual dates of origin has led to a popular theory that primates somehow crossed the globe and even rafted across oceans to reach America and Madagascar.

In this new approach to molecular phylogenetics, vicariance, and plate tectonics, Heads shows that the distribution ranges of primates and their nearest relatives, the tree shrews and the flying lemurs, conforms to a pattern that would be expected from their having evolved from a widespread ancestor. This ancestor could have evolved into the extinct Plesiadapiformes in north America and Eurasia, the primates in central-South America, Africa, India and south East Asia, and the tree shrews and flying lemurs in South East Asia.

Divergence between strepsirrhines (lemurs and lorises) and haplorhines (tarsiers and anthropoids) is correlated with intense volcanic activity on the Lebombo Monocline in Africa about 180 million years ago. The lemurs of Madagascar diverged from their African relatives with the opening of the Mozambique Channel (160 million years ago), while New and Old World monkeys diverged with the opening of the Atlantic about 120 million years ago.

“This model avoids the confusion created by the center of origin theories and the assumption of a recent origin for major primate groups due to a misrepresentation of the fossil record and molecular clock divergence estimates” said Michael from his New Zealand office. “These models have resulted in all sorts of contradictory centers of origin and imaginary migrations for primates that are biogeographically unnecessary and incompatible with ecological evidence”.

The tectonic model also addresses the otherwise insoluble problem of dispersal theories that enable primates to cross the Atlantic to America, and the Mozambique Channel to Madagascar although they have not been able to cross 25 km from Sulawesi to Moluccan islands and from there travel to New Guinea and Australia.

Heads acknowledged that the phylogenetic relationships of some groups such as tarsiers, are controversial, but the various alternatives do not obscure the patterns of diversity and distribution identified in this study.

Biogeographic evidence for the Jurassic origin for primates, and the pre-Cretaceous origin of major primate groups considerably extends their divergence before the fossil record, but Heads notes that fossils only provide minimal dates for the existence of particular groups, and there are many examples of the fossil record being extended for tens of millions of years through new fossil discoveries.

The article notes that increasing numbers of primatologists and paleontologists recognize that the fossil record cannot be used to impose strict limits on primate origins, and that some molecular clock estimates also predict divergence dates pre-dating the earliest fossils. These considerations indicate that there is no necessary objection to the biogeographic evidence for divergence of primates beginning in the Jurassic with the origin of all major groups being correlated with plate tectonics.

Note: from a news release issued by the Buffalo Museum of Science

Oldest Occurrence of Arthropods (Fly, Mite) Preserved in Amber

August 29th, 2012

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An international team of scientists has discovered the oldest record of arthropods — invertebrate animals that include insects, arachnids, and crustaceans — preserved in amber. The specimens, one fly and two mites found in millimeter-scale droplets of amber from northeastern Italy, are about 100 million years older than any other amber arthropod ever collected. The group’s findings, which are published August 27 in the Proceedings of the National Academy of Sciences, pave the way for a better evolutionary understanding of the most diverse group of organisms in the world.

amber

“Amber is an extremely valuable tool for paleontologists because it preserves specimens with microscopic fidelity, allowing uniquely accurate estimates of the amount of evolutionary change over millions of years,” said corresponding author David Grimaldi, a curator in the American Museum of Natural History’s Division of Invertebrate Zoology and a world authority on amber and fossil arthropods.

Globules of fossilized resin are typically called amber. Amber ranges in age from the Carboniferous (about 340 million years ago) to about 40,000 years ago, and has been produced by myriad plants, from tree ferns to flowering trees, but predominantly by conifers. Even though arthropods are more than 400 million years old, until now, the oldest record of the animals in amber dates to about 130 million years. The newly discovered arthropods break that mold with an age of 230 million years. They are the first arthropods to be found in amber from the Triassic Period.

The amber droplets, most between 2-6 millimeters long, were buried in outcrops high in the Dolomite Alps of northeastern Italy and excavated by Eugenio Ragazzi and Guido Roghi of the University of Padova. About 70,000 of the miniscule droplets were screened for inclusions — encased animal and plant material — by a team of German scientists led by Alexander Schmidt, of Georg-August University, Göttingen, resulting in the discovery of the three arthropods. The tiny arthropods were studied by Grimaldi and Evert Lindquist, an expert on gall mites at Agriculture and Agri-Food Canada in Ottawa.

Two of the specimens are new species of mites, namedTriasacarus fedelei and Ampezzoa triassica. They are the oldest fossils in an extremely specialized group called Eriophyoidea that has about 3,500 living species, all of which feed on plants and sometimes form abnormal growth called “galls.” The ancient gall mites are surprisingly similar to ones seen today.

“You would think that by going back to the Triassic you’d find a transitional form of gall mite, but no,” Grimaldi said. “Even 230 million years ago, all of the distinguishing features of this family were there — a long, segmented body; only two pairs of legs instead of the usual four found in mites; unique feather claws, and mouthparts.”

The ancient mites likely fed on the leaves of the tree that ultimately preserved them, a conifer in the extinct family Cheirolepidiaceae. Although about 97 percent of today’s gall mites feed on flowering plants, Triasacarus fedelei andAmpezzoa triassica existed prior to the appearance and rapid radiation of flowering plants. This finding reveals the evolutionary endurance of the mites.

“We now know that gall mites are very adaptable,” Grimaldi said. “When flowering plants entered the scene, these mites shifted their feeding habits, and today, only 3 percent of the species live on conifers. This shows how gall mites tracked plants in time and evolved with their hosts.”

The third amber specimen, a fly, cannot be identified because, outside of the insect’s antennae, its body parts were not well preserved. But now that the researchers have shown that amber preserved Triassic arthropods, they are eager to find more specimens.

“There was a huge change in the flora and fauna in the Triassic because it was right after one of the most profound mass extinctions in history, at the end of the Permian,” Grimaldi said. “It’s an important time to study if you want to know how life evolved.”

Ancient termite-digging fossil added to mammal family tree

August 28th, 2012

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A new look at a fossil mammal with powerful front legs for digging is clearing up questions about the origin of a group of strange and scaly modern-day creatures called pangolins.

First excavated in Mongolia in the 1970s, the fossil sat in storage for decades until researchers for the Russian Academy of Sciences rediscovered and analyzed it, reporting their results

pangolin (Manis pentadactyla)

in the Journal of Vertebrate Paleontology.

What they found was a dog-size, strong-shouldered digger called Ernanodon. This mammal lived about 57 million years ago, after dinosaurs had died out and our furry ancestors had taken over. Ernanodon was known from one other fossil found in China, but that specimen is warped, and some archaeologists even thought it might be a fake.

The new discovery puts those accusations to rest, said study researcher Peter Kondrashov, an anatomist at Kirksville College of Osteopathic Medicine in Missouri.

“It’s the real deal,” Kondrashov told LiveScience.

The find also helps put the mysterious Ernanodon into the mammal family tree. Archaeologists had suspected that the animal might be related to modern-day sloths and armadillos. Instead, Kondrashov said, it is more closely tied to pangolins, which live in the tropics of Asia and Africa. Pangolins are bizarre mammals covered in scales. Like anteaters, they have a long, sticky tongue for catching termites and other insects.

Ernanodon probably did the same, Kondrashov said. Little is known about the Paleocene environment in Asia that Ernanodon called home, but similar latitudes in North America were a mixture of forest and open landscape. Ernanodon lacked adaptations for climbing and had only minimal teeth, suggesting that it was a ground-dweller that ate soft food like insects. Its strong claws and powerful shoulders would have helped it dig into anthills and termite mounds.

“It was definitely a terrestrial mammal. It doesn’t have any adaptations for climbing trees,” Kondrashov said. “It was just designed to walk on fairly flat surfaces.”

The new Ernanodon is an extremely complete skeleton, Kondrashov said, rare for Paleocene Asia.

“This is the time when all the main groups of mammals were established on the planet. This history is really well-deciphered in North America, and there’s very little known about Asia,” he said. “This helps us to understand how these early steps in the evolution of major groups of mammals occurred in Asia.”

A New species of plant-eating dinosaur ?

August 28th, 2012

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A team of paleontologists, including a University of Pennsylvania doctoral candidate, has described a new species of dinosaur based upon an incomplete skeleton found in western New Mexico. The new species,Jeyawati rugoculus, comes from rocks that preserve a swampy forest ecosystem that thrived near the shore of a vast inland sea 91 million years ago.

The dinosaur, whose name translates to mean “grinding-mouth, wrinkle-eye,” was most likely an herbivore that ate the ferns and conifer trees found as fossils in the same rock layer. A basal hadrosauroid, the find included partial skull bones, several vertebrae and fragments of the ribs.

Jeyawati rugoculus,

Jeyawati is a close relative of the duck-billed hadrosaurs, which were abundant across the Northern Hemisphere for much of the Late Cretaceous Epoch, between 80 and 65 million years ago. Jeyawati retains some primitive features of the teeth and jaws that preclude it from being a fully-fledged hadrosaur.

Jeyawati, pronounced “HEY-a-WHAT-ee,” is derived from two words in the language of the Zuni people, a Native American tribe located around the Zuni River in western New Mexico. The name is a reference to the sophisticated chewing mechanism evolved by the herbivorous lineage to which Jeyawati belongs.

The second part of the name, rugoculus, comes from the Latin words ruga and oculus and means “wrinkle eye,” describing a unique feature of the new species. One of the bones that forms the eye socket exhibits a peculiar rough or wrinkly texture on its outer side, suggesting that Jeyawati rugoculus might have sported one or more large scales above and behind its eye.

“Jeyawati apparently endured a hard life,” said Andrew T. McDonald, lead author of the study and a doctoral candidate in Penn’s Department of Earth and Environmental Sciences. “Several of the rib fragments have a swollen, rough surface, indicating that the animal suffered broken ribs at some point in its life and that those injuries healed before the animal’s death.”

Although the fossil remains were discovered in 1996, it has only now been confirmed that the species is unique.Jeyawati is a member of an assemblage of dinosaurs and other animals unknown as recently as 15 years ago.

McDonald began his classification of the find while a student at the University of Nebraska, before completing the work with Peter Dodson, professor of anatomy and paleontontology in the schools of Veterinary Medicine and Arts and Sciences at Penn.

“From looking at the more complete remains of species related to Jeyawati, we can make several assumptions,” McDonald said, “including that the creature probably walked on all fours but was also capable of rearing up on two legs.”

The bones now reside at the Arizona Museum of Natural History, where specimens of other dinosaurs uncovered in this region are also located.

Dinosaurs that coexisted with Jeyawati include Zuniceratops, the earliest known North American horned dinosaur, and Nothronychus, a strange herbivorous beast belonging to a lineage that, until the discovery of Nothronychus, was known only from Asia.

The partial skull and other fragments of Jeyawati were discovered by paleontologist Douglas Wolfe, principal investigator of the Zuni Basin Paleontological Project. Subsequent excavation and collection was carried out for 13 years with the aid of James Kirkland, state paleontologist with the Utah Geological Survey, and volunteers from the Southwest Paleontological Society, among others.

In 2006, McDonald, then an undergraduate geology student, began a project to describe the fossil. The analysis revealed that the bones were sufficiently distinct from those of other dinosaurs to warrant the naming of a new species.

Courtesy: news release issued by the University of Pennsylvania

Fossil of “Shield”-Headed Croc Found in Morocco

August 27th, 2012

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A new prehistoric croc sporting an odd head “shield” has been found in Morocco, according to a study published .

Dubbed ShieldCroc, the animal’s head appendage was surrounded by blood vessels and covered with a sheath like those seen in frilled dinosaurs, including Triceratops.

shieldcroc

At 30 to 35 feet (9 to 11 meters) long, the river-dwelling monster would have preyed on other giant animals of the late Cretaceous, such as 13-foot-long (4-meter-long) Coelacanths. But ShieldCroc—formally Aegisuchus witmeri—likely boasted relatively weak jaws, at least compared with those of today’s crocodiles.

“It’s fairly certain that it belonged to a group of crocodyliforms—including the flat-headed crocs—that had really thin, weak jaws and weak chin joints,” said researcher Casey Holliday, a paleontologist at the University of Missouri. Crocodyliforms are part of a group known as the crocodilians, which includes modern-day alligators, caimans, and more.

“So they weren’t wrestling dinosaurs on the water’s edge. They would have been quick, snap feeders waiting for prey to come by and then grabbing it and swallowing it with large, basket-shaped mouths—something like a pelican would do,” said Holliday, who co-authored the new study in the journal PLoS ONE.

ShieldCroc’s Headpiece for Show?

A piece of ShieldCroc’s skull landed in Canada’s Royal Ontario Museum in the early 2000s, but Holliday and colleagues have only recently studied the specimen and its odd headpiece.

It’s difficult to determine what purpose the shield served when the animal lived, some 99 million years ago, Holliday noted.

But after rigorous evaluation of the fossil and studies of comparative behaviors with modern crocodilians, scientists suggest the shield may have helped ShieldCroc regulate its temperature and communicate with other ShieldCrocs.

For instance, some crocodyliforms and living crocodilians, such as the Cuban crocodile, have horns on the sides of their heads, which males use to impress females and scare away other males. “We kind of see ShieldCroc having similar behaviors and showing off the roof of its head,” Holliday said.

Despite these possible similarities with modern crocodilians, the animal appears to have been one of a kind, said Christopher Brochu, a University of Iowa paleontologist, who wasn’t involved in the study.

“There’s nothing quite like this among the birds or the crocodilians, which are the two closest living relatives of this thing.”

ShieldCroc Highlights African “Melting Pot”

ShieldCroc’s discovery in Morocco could suggest that modern crocs evolved in what’s now the Mediterranean—a theory that remains hotly debated among crocodilian experts.

But there’s no doubt the animal provides evidence of astonishing crocodyliform diversity in the Southern Hemisphere during the late Cretaceous, said Holliday, who described the new species this week at the 71st Annual Meeting of the Society of Vertebrate Paleontology in Las Vegas.

“It definitely points to … Africa [as] a melting pot of different crocodyliforms living in the same region at the same time,” Holliday said.

“One lineage, including DogCroc, BoarCroc, and others tended to be terrestrial, while another group, including SuperCroc, were big, aquatic, predatory crocs. ShieldCroc represents another group and a more modern flavor of crocs.”

Bizarre Crocodyliforms Ruled Southern Hemisphere

With the discoveries of ShieldCroc and related species, University of Iowa’s Brochu said, “We’re beginning to realize just how diverse and even bizarre the crocodilyforms were in the Southern Hemisphere,” he said.

“The group was extremely widespread, and in some places crocodyliforms may have been among the major predators and even herbivores. And in some places they really were simply bizarre.”

For instance, “in the southern Mediterranean, including North Africa, we’re seeing these animals that look nothing like any living crocodilian.”

courtesy : Brian Handwerk