Paleontology: A monster put in its place
An analysis of the fossil known as the Minden Monster has enabled paleontologists to assign the largest predatory dinosaur ever found in Germany to a previously unknown genus, among a group that underwent rapid diversification in the Middle Jurassic.
This huge dinosaur dates to about 163 million years ago, in the Middle Jurassic. And it is not only the first carnivorous dinosaur from this period to be unearthed in Germany, it is also the largest ever found in the country: Based on the remains so far recovered, the specimen is estimated to have been between 8 and 10 meters in length. In comparison with other carnivorous dinosaurs, the animal was very sturdily built, weighed more than 2 tons — and was probably not fully grown when it died. Now Oliver Rauhut, a paleontologist in the Department of Earth and Environmental Sciences at LMU (who is also affiliated with the Bavarian State Collection for Paleontology and Geology in Munich), together with Tom Hübner and Klaus-Peter Lanser of the LWL Museum of Natural History in Münster, have undertaken a detailed study of the fossil material, and concluded that the specimen represents a previously unknown genus and species to which they have given the name Wiehenvenator albati.
Dinosaur archipelago
The first fossilized bones and teeth were discovered in 1999 during a routine surface survey in an abandoned quarry in the Wiehengebirge, a range of low hills south of Minden. Although the fossil clearly represents a terrestrial form, the remains were embedded in marine sediments. It is however known that, in the Middle Jurassic, large areas of what is now Central Europe lay below sea level, and the shallow waters of this sea were dotted with islands. These islands appear to have been the home of a broad spectrum of carnivorous dinosaurs, some of which reached very large sizes, Rauhut explains.
“Moreover, most of them belonged to the group known as the megalosaurids.” Wiehenvenator albati was a megalosaur and other representatives of the group have been found in France and England. In fact, the megalosaurids are the earliest large carnivorous dinosaurs we know of.
The remains of W. albati that have so far been discovered do not constitute a complete skeleton. The material is, however, very well preserved, and anatomical details can be clearly discerned which unequivocally prove that this individual not only represents a new species, but a new genus. Some of the teeth that have been found are as big as bananas, and have a recurved shape, pointing backwards into the pharynx. Like Allosaurus and the much younger Tyrannosaurus rex, W. albati was bipedal, standing on its hindlegs, while its forelimbs were much reduced in length.
A phylogenetic analysis of the morphology of the specimen revealed that Wiehenvenator can be assigned to a group of dinosaurs that underwent a rapid adaptive radiation during the Middle Jurassic, giving rise to a diverse array of species in a relatively short time. “Practically all the major groups of predatory dinosaurs originated during this period, including the tyrannosaurs — which, however, only gave rise to their really gigantic representatives some 80 million years later — and the first direct ancestors of the birds,” says Rauhut. This huge burst of speciation was probably made possible by the preceding extinction of a large proportion of the more primitive forms of predatory dinosaurs at the end of Lower Jurassic, which may in turn have been precipitated by a change in the climate due to widespread volcanic activity.
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The above post is reprinted from materials provided by Ludwig-Maximilians-Universitaet Muenchen (LMU). Note: Content may be edited for style and length.
Fossil pollen ‘sneeze’ caught by research team
Like capturing a sneeze, researchers including a University of Guelph scientist have recorded the only known example of prehistoric pollen caught in explosive mid-discharge from a fossil flower.
The team describes this “freeze-frame” fossilized pollen release — preserved in amber more than 20 million years ago — in a paper describing a new genus of fossil nettle plants.
The researchers captured on camera pollen explosions.
The paper is co-authored by Peter Kevan, emeritus professor in the School of Environmental Sciences. It appears in the journal Botany alongside another paper by a second team that also includes the U of G researcher.
That second paper looks at a modern-day plant relative in Latin America that is surprising researchers with its use of explosive pollen release, a fair-weather dispersal method seemingly ill-suited to its home in humid tropical rainforests.
In their fossil paper, Kevan and his co-authors describe a new genus (Ekrixanthera, meaning “explosive anther”) containing two new species of extinct plants related to modern-day nettles.
These fossil plants were preserved during the mid-Tertiary period, said Kevan. By then, dinosaurs were long-extinct and non-human mammals roamed Earth.
The samples came from the Dominican Republic and Mexico.
One Mexican sample has preserved pollen grains caught in mid-discharge from the male plant’s anther.
This pollen burst normally takes less than one-tenth of a second, said Kevan. “It’s remarkable that it was captured. It’s like catching a sneeze.”
He was asked to help identify the plants by lead author George Poinar Jr., an expert on amber fossils at Oregon State University.
“We ended up with the new genus because the flowers do not match those of any modern species,” said Kevan. “This tells us something about how old that group of plants is, and that this pollination mechanism goes back a long way.”
That form of pollen dispersal is also described in the second paper about modern-day tropical nettles. Boehmeria caudata grows from southern North America to northern Argentina.
Explosive pollen release is “something you don’t expect in the rainforest. Pollen blasted into the air is likely to get rained out.”
Most tropical plants rely instead on such creatures as insects, bats and birds rather than wind pollination, said Kevan.
In this group of nettles, the male plant disperses its pollen during short dry periods. Even during the rainy season, short sunny periods of high heat and low humidity trigger pollen release.
Drying causes parts of its stamens to shrink unevenly. Physical tension ruptures the anther to release an explosive burst of pollen.
That quick-release mechanism propels pollen into air currents and allows the male flowers to react to short-term weather conditions.
Kevan’s co-authors are students at the University of Sao Paulo led by Paula Maria Montoya-Pfeiffer. They studied Boehmeria during a pollination course taught in Brazil by Kevan in late 2014.
He and colleagues have taught that course in several Latin American countries for decades.
A rare small specimen discovered from the age of flying giants
A rare small-bodied pterosaur, a flying reptile from the Late Cretaceous period approximately 77 million years ago, is the first of its kind to have been discovered on the west coast of North America.
Pterosaurs are the earliest vertebrates known to have evolved powered flight.
The specimen is unusual as most pterosaurs from the Late Cretaceous were much larger with wingspans of between four and eleven metres (the biggest being as large as a giraffe, with a wingspan of a small plane), whereas this new specimen had a wingspan of only 1.5 metres.
The fossils of this animal are the first associated remains of a small pterosaur from this time, comprising a humerus, dorsal vertebrae (including three fused notarial vertebrae) and other fragments. They are the first to be positively identified from British Columbia, Canada and have been identified as belonging to an azhdarchoid pterosaur, a group of short-winged and toothless flying reptiles which dominated the final phase of pterosaur evolution.
Previous studies suggest that the Late Cretaceous skies were only occupied by much larger pterosaur species and birds, but this new finding, which is reported in the Royal Society journal Open Science, provides crucial information about the diversity and success of Late Cretaceous pterosaurs.
Lead author of the study Elizabeth Martin-Silverstone, a Palaeobiology PhD Student at the University of Southampton, said: “This new pterosaur is exciting because it suggests that small pterosaurs were present all the way until the end of the Cretaceous, and weren’t outcompeted by birds. The hollow bones of pterosaurs are notoriously poorly preserved, and larger animals seem to be preferentially preserved in similarly aged Late Cretaceous ecosystems of North America. This suggests that a small pterosaur would very rarely be preserved, but not necessarily that they didn’t exist.”
The fossil fragments were found on Hornby Island in British Columbia in 2009 by a collector and volunteer from the Royal British Columbia Museum, who then donated them to the Museum. At the time, it was given to Victoria Arbour, a then PhD student and dinosaur expert at the University of Alberta. Victoria, as a postdoctoral researcher at North Carolina State University and the North Carolina Museum of Natural Sciences, then contacted Elizabeth and the Royal BC Museum sent the specimen for analysis in collaboration with Dr Mark Witton, a pterosaur expert at the University of Portsmouth.
Dr Witton said: “The specimen is far from the prettiest or most complete pterosaur fossil you’ll ever see, but it’s still an exciting and significant find. It’s rare to find pterosaur fossils at all because their skeletons were lightweight and easily damaged once they died, and the small ones are the rarest of all. But luck was on our side and several bones of this animal survived the preservation process. Happily, enough of the specimen was recovered to determine the approximate age of the pterosaur at the time of its death. By examining its internal bone structure and the fusion of its vertebrae we could see that, despite its small size, the animal was almost fully grown. The specimen thus seems to be a genuinely small species, and not just a baby or juvenile of a larger pterosaur type.”
Elizabeth Martin-Silverstone added: “The absence of small juveniles of large species — which must have existed — in the fossil record is evidence of a preservational bias against small pterosaurs in the Late Cretaceous. It adds to a growing set of evidence that the Late Cretaceous period was not dominated by large or giant species, and that smaller pterosaurs may have been well represented in this time. As with other evidence of smaller pterosaurs, the fossil specimen is fragmentary and poorly preserved: researchers should check collections more carefully for misidentified or ignored pterosaur material, which may enhance our picture of pterosaur diversity and disparity at this time.”