A Relative from the Tianyuan Cave: Humans Living 40,000 Years Ago Likely Related to Many Present-Day Asians and Native Americans
Jan. 21, 2013 — Ancient DNA has revealed that humans living some 40,000 years ago in the area near Beijing were likely related to many present-day Asians and Native Americans.
An international team of researchers including Svante Pääbo and Qiaomei Fu of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, sequenced nuclear and mitochondrial DNA that had been extracted from the leg of an early modern human from Tianyuan Cave near Beijing, China. Analyses of this individual’s DNA showed that the Tianyuan human shared a common origin with the ancestors of many present-day Asians and Native Americans. In addition, the researchers found that the proportion of Neanderthal and Denisovan-DNA in this early modern human is not higher than in people living in this region nowadays.
Humans with morphology similar to present-day humans appear in the fossil record across Eurasia between 40,000 and 50,000 years ago. The genetic relationships between these early modern humans and present-day human populations had not yet been established. Qiaomei Fu, Matthias Meyer and colleagues of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, extracted nuclear and mitochondrial DNA from a 40,000 year old leg bone found in 2003 at the Tianyuan Cave site located outside Beijing. For their study the researchers were using new techniques that can identify ancient genetic material from an archaeological find even when large quantities of DNA from soil bacteria are present.
The researchers then reconstructed a genetic profile of the leg’s owner. “This individual lived during an important evolutionary transition when early modern humans, who shared certain features with earlier forms such as Neanderthals, were replacing Neanderthals and Denisovans, who later became extinct,” says Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology, who led the study.
The genetic profile reveals that this early modern human was related to the ancestors of many present-day Asians and Native Americans but had already diverged genetically from the ancestors of present-day Europeans. In addition, the Tianyuan individual did not carry a larger proportion of Neanderthal or Denisovan DNA than present-day people in the region. “More analyses of additional early modern humans across Eurasia will further refine our understanding of when and how modern humans spread across Europe and Asia,” says Svante Pääbo.
Parts of the work were carried out in a new laboratory jointly run by the Max Planck Society and the Chinese Academy of Sciences in Beijing.
Earliest Sea Cow Ancestors Originated in Africa, Lived in Fresh Water
Jan. 16, 2013 — A new fossil discovered in Tunisia represents the oldest known ancestor of modern-day sea cows, supporting the African origins of these marine mammals. The find is described in research published January 16 in the open access journal PLOS ONE by Julien Benoit and colleagues from the University of Science and Technology in Montpellier, France.
Some fossils of sea cow ancestors have been found in Jamaica, but the Tunisian fossil is more primitive and pre-dates these, revealing an older ancestor for sea cows that emerged at the same time as other modern mammals. Unlike whales and dolphins, the evolutionary origins of the sea cow family have been obscure.
They share an ancestor with elephants, and it is thought that their oldest relatives were terrestrial animals that gradually adapted to an aquatic life. The last common ancestor of the two species may have lived in freshwater swamps well before the time that the new species described in this study lived.
Though this specimen may not have been the common link between modern day sea cows and elephants, the authors’ analyses suggest that this new species lived in fresh water, not sea waters.
Australia’s Stampeding Dinosaurs Take a Dip: Largely Tracks of Swimming Rather Than Running Animals
Jan. 8, 2013 — Queensland paleontologists have discovered that the world’s only recorded dinosaur stampede is largely made up of the tracks of swimming rather than running animals.
The University of Queensland’s (UQ) PhD candidate Anthony Romilio led the study of thousands of small dinosaur tracks at Lark Quarry Conservation Park, central-western Queensland.
Mr Romilio says the 95-98 million-year-old tracks are preserved in thin beds of siltstone and sandstone deposited in a shallow river when the area was part of a vast, forested floodplain.
“Many of the tracks are nothing more than elongated grooves, and probably formed when the claws of swimming dinosaurs scratched the river bottom,” Romilio said.
“Some of the more unusual tracks include ‘tippy-toe’ traces — this is where fully buoyed dinosaurs made deep, near vertical scratch marks with their toes as they propelled themselves through the water.
“It’s difficult to see how tracks such as these could have been made by running or walking animals.
“If that was the case we would expect to see a much flatter impression of the foot preserved in the sediment.”
Mr Romilio said that similar looking swim traces made by different sized dinosaurs also indicated fluctuations in the depth of the water.
“The smallest swim traces indicate a minimum water depth of about 14 cm, while much larger ones indicate depths of more than 40 cm,” Mr Romilio said.
“Unless the water level fluctuated, it’s hard to envisage how the different sized swim traces could have been preserved on the one surface.
“Some of the larger tracks are much more consistent with walking animals, and we suspect these dinosaurs were wading through the shallow water.”
Mr Romilio said the swimming dinosaur tracks at Lark Quarry belonged to small, two-legged herbivorous dinosaurs known as ornithopods.
“These were not large dinosaurs,” Mr Romilio said.
“Some of the smaller ones were no larger than chickens, while some of the wading animals were as big as emus.”
The researchers interpreted the large spacing among many consecutive tracks to indicate that the dinosaurs were moving downstream, perhaps using the current of the river to assist their movements.
Given the likely fluctuations in water depth, the researchers assume the tracks were formed over several days, maybe even weeks.
Previous research had identified two types of small dinosaur tracks at Lark Quarry: long-toed tracks (called Skartopus) and short-toed tracks (called Wintonopus).
The UQ scientists found that just like you ‘shouldn’t judge a book by its cover’, you also ‘shouldn’t judge a track by its outline’.
“3D profiles of ‘Skartopus’ tracks reveal that they were made by a short-toed trackmaker dragging its toes through the sediment, thereby elongating the tracks,” explained Romilio.
“In this context, they are best interpreted as a just another variant of Wintonopus.”
Romilio’s supervisor and coauthor of the new paper, Dr Steve Salisbury, added that, “3D analysis of the Lark Quarry tracks has allowed us to greatly refine our understanding of what this site represents.
“It is also allowing us to learn more about how these dinosaurs moved and behaved in different environments,” Dr Salisbury said.
For the past 30 years, the tracks at Lark Quarry have be known as the world’s only record of a ‘dinosaur stampede’.
Previous research by Romilio and Salisbury in 2011 also showed the larger tracks at Lark Quarry were probably made by a herbivorous dinosaur similar to Muttaburrasaurus, and not a large theropod, as had previously been proposed.
“Taken together, these findings strongly suggest Lark Quarry does not represent a ‘dinosaur stampede’,” Romilio said.
“A better analogy for the site is probably a river crossing.”
Dr Salisbury said regardless of how it was interpreted, these findings took nothing away from the importance of the site.
“Lark Quarry is, and will always remain, one of Australia’s most important dinosaur tracksites,” Dr Salisbury said.
The new study was published in the January 2013 issue of Journal of Vertebrate Paleontology.
Giant Fossil Predator Provides Insights Into the Rise of Modern Marine Ecosystem Structures
Jan. 7, 2013 — An international team of scientists has described a fossil marine predator measuring 8.6 meters in length (about 28 feet) recovered from the Nevada desert in 2010 as representing the first top predator in marine food chains feeding on prey similar to its own size.
A paper with their description will appear the week of Jan. 7, 2013 in the early electronic issue of Proceedings of the National Academy of Sciences.
Scientists who studied the fossil include lead author Dr. Nadia Fröbisch and Prof. Jörg Fröbisch (both at Museum für Naturkunde Leibniz-Institut für Evolutions- und Biodiversitätsforschung), Prof. P. Martin Sander (Steinmann Institute of Geology, Mineralogy, and Paleontology, Division of Paleontology, University of Bonn), Prof. Lars Schmitz (W. M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, Claremont, California) and Dr. Olivier Rieppel (The Field Museum, Chicago, Illinois).
The 244-million-year-old fossil, named Thalattoarchon saurophagis (lizard-eating sovereign of the sea) is an early representative of the ichthyosaurs, a group of marine reptiles that lived at the same time as dinosaurs and roamed the oceans for 160 million years. It had a massive skull and jaws armed with large teeth with cutting edges used to seize and slice through other marine reptiles in the Triassic seas. Because it was a meta-predator, capable of feeding on animals with bodies similar in size to its own, Thalattoarchon was comparable to modern orca whales.
Remarkably, only eight million years prior to the appearance of Thalattoarchon, a severe extinction at the end of the Permian period killed as many as 80 to 96 percent of species in the Earth’s oceans. The rise of a predator such as Thalattoarchon documents the fast recovery and evolution of a modern ecosystem structure after the extinction.
“Everyday we learn more about the biodiversity of our planet including living and fossil species and their ecosystems” Dr. Fröbisch said. “The new find characterizes the establishment of a new and more advanced level of ecosystem structure. Findings like Thalattoarchon help us to understand the dynamics of our evolving planet and ultimately the impact humans have on today’s environment.”
“This discovery is a good example of how we study the past in order to illuminate the future,” said Dr. Rieppel of The Field Museum.
The ichthyosaur was recovered from what is today a remote mountain range in central Nevada. Most of the animal was preserved, including the skull (except the front of the snout), parts of the fins, and the complete vertebral column up to the tip of the tail. Supported by a grant from the National Geographic Society’s Committee for Research and Exploration, the team of paleontologists took three weeks to unearth the ichthyosaur and prepare it for its transport by helicopter and truck out of the field.
New Study Sheds Light On Dinosaur Size
Dec. 19, 2012 — Dinosaurs were not only the largest animals to roam the Earth — they also had a greater number of larger species compared to all other back-boned animals — scientists suggest in a new paper published in the journal PLOS ONE.
The researchers, from Queen Mary, University of London, compared the size of the femur bone of 329 different dinosaur species from fossil records. The length and weight of the femur bone is a recognised method in palaeontology for estimating a dinosaur’s body mass.
They found that dinosaurs follow the opposite pattern of body size distribution as seen in other vertebrate species. For example, within living mammals there tends to be few larger species, such as elephants, compared to smaller animals, such as mice, which have many species. The evidence from fossil records implies that in contrast there were many species of larger dinosaurs and few small species.
Dr David Hone from Queen Mary’s School of Biological and Chemical Sciences, explains: “What is remarkable is that this tendency to have more species at a bigger size seemed to evolve quite early on in dinosaurian evolution around the Late Triassic period, 225 million years ago, raising questions about why they got to be so big.
“Our evidence supports the hypothesis that young dinosaurs occupied a different ecological niche to their parents so they weren’t in competition for the same sources of food as they ate smaller plants or preyed on smaller size animals. In fact, we see modern crocodiles following this pattern — baby crocodiles start by feeding off insects and tadpoles before graduating onto fish and then larger mammals.”
Dr Eoin Gorman, also from Queen Mary’s School of Biological and Chemical Sciences added: “There is growing evidence that dinosaurs produced a large number of offspring, which were immediately vulnerable to predation due to their smaller size. It was beneficial for the herbivores to grow to large size as rapidly as possible to escape this threat, but the carnivores had sufficient resources to live optimally at smaller sizes.
“These differences are reflected in our analyses and also offer an explanation why other groups do not follow a similar pattern. Several modern-day vertebrate groups are almost entirely carnivorous, while many of the herbivores are warm-blooded, which limits their size.”
New Dinosaur: First Freshwater Mosasaur Discovered
Dec. 19, 2012 — A new mosasaur species discovered in Hungary is the first known example of this group of scaled reptiles to have lived in freshwater river environments similar to modern freshwater dolphins.
The research is published Dec. 19 in the open-access journal PLOS ONE by Laszlo Makadi from the Hungarian Natural History Museum, Hungary and colleagues from the University of Alberta, Canada and MTA-ELTE Lendület Dinosaur Research Group, Hungary.
The species lived about 84 million years ago, the largest specimens reached about 20 feet in length, and belongs to a family called ‘mosasaurs’, conventionally thought of as gigantic finned marine lizards, similar and perhaps even related to present day monitor lizards. The researchers discovered several fossils of the new species, ranging from small juveniles to large adults that suggest that this species had limbs like a terrestrial lizard, a flattened, crocodile-like skull, and a tail unlike other known members of the mosasaur family.
The fossils were recovered from an open-pit mine in the Bakony Hills of Western Hungary, which were once flood-plains. According to the study, this is the first known mosasaur that lived in freshwater, and only the second specimen of a mosasaur to have been found in rocks that were not once deposited in the ocean. Makadi says, “The evidence we provide here makes it clear that similar to some lineages of cetaceans, mosasaurs quickly adapted to a variety of aquatic environments, with some groups re- invading available niches in freshwater habitats. The size of Pannoniasaurus makes it the largest known predator in the waters of this paleo-environment.”
Even in the modern world, scaly reptiles in the aquatic world are extremely rare. Only a few species live in the water, and even fewer, like marine iguanas and sea kraits, live in the oceans. The new species described here probably adapted to freshwater environments similarly to river dolphins, such as those now inhabiting the Amazon, Ganges and Yangtze rivers.
Paleo-Ocean Chemistry: New Data Challenge Old Views About Evolution of Early Life
Dec. 23, 2012 — A research team led by biogeochemists at the University of California, Riverside has tested a popular hypothesis in paleo-ocean chemistry, and proved it false.
The fossil record indicates that eukaryotes — single-celled and multicellular organisms with more complex cellular structures compared to prokaryotes, such as bacteria — show limited morphological and functional diversity before 800-600 million years ago. Many researchers attribute the delayed diversification and proliferation of eukaryotes, which culminated in the appearance of complex animals about 600 million years ago, to very low levels of the trace metal zinc in seawater.
As it is for humans, zinc is essential for a wide range of basic cellular processes. Zinc-binding proteins, primarily located in the cell nucleus, are involved in the regulation of gene transcription.
Eukaryotes have increasingly incorporated zinc-binding structures during the last third of their evolutionary history and still employ both early- and late-evolving zinc-binding protein structures. Zinc is, therefore, of particular importance to eukaryotic organisms. And so it is not a stretch to blame the 1-2-billion-year delay in the diversification of eukaryotes on low bioavailability of this trace metal.
But after analyzing marine black shale samples from North America, Africa, Australia, Asia and Europe, ranging in age from 2.7 billion years to 580 million years old, the researchers found that the shales reflect high seawater zinc availability and that zinc concentrations during the Proterozoic (2.5 billion to 542 million years ago) were similar to modern concentrations. Zinc, the researchers posit, was never biolimiting.
Study results appear online Dec. 23 in Nature Geoscience.
“We argue that the concentration of zinc in ancient marine black shales is directly related to the concentrations of zinc in seawater and show that zinc is abundant in these rocks throughout Earth’s history,” said Clint Scott, the first author of the research paper and a former UC Riverside graduate student. “We found no evidence for zinc biolimitation in seawater.”
Scott, now a research geologist with the U.S. Geological Survey, explained that the connection between zinc limitation and the evolution of eukaryotes was based largely on the hypothesis that Proterozoic oceans were broadly sulfidic. Under broadly sulfidic conditions, zinc should have been scarce because it would have rapidly precipitated in the oceans, he explained.
“However, a 2011 research paper in Nature also published by our group at UCR demonstrated that Proterozoic oceans were more likely broadly ferruginous — that is, low in oxygen and iron-rich — and that sulfidic conditions were more restricted than previously thought,” said Scott, who performed the research in the lab of Timothy Lyons, a professor of biogeochemistry and the principal investigator of the research project.
The research team argues that ferruginous deep oceans, combined with large hydrothermal fluxes of zinc via volcanic activity on the seafloor, maintained high levels of dissolved zinc throughout the oceans and provided a relatively stable marine reservoir of the trace metal over the past 2.7 billion years.
“The key challenge in understanding the early evolution of life is recognizing the environmental conditions under which that life first appeared and diversified,” Lyons said. “We have taken a very direct approach that specifically tracks the availability of essential micronutrients, and, to our surprise, zinc supplies in ancient seawater were much higher and less variable than previously imagined.
“We can imagine for the first time,” he quipped, “that zinc supplements were not on the shopping lists of our early eukaryotic ancestors, and so we better find another reason to explain the mysterious delay in their rise in the ocean.”
Scott, who graduated with a doctoral degree in geological sciences from UCR in 2009, and Lyons were joined in the study by Noah J. Planavsky, a former UCR graduate student in Lyons’ lab; Chris L. Dupont at the J. Craig Venter Institute, La Jolla, Calif.; Brian Kendall and Ariel D. Anbar at Arizona State University; Benjamin C. Gill at Virginia Polytechnic Institute and State University and also a former member of the Lyons lab; Leslie J. Robbins and Kurt O. Konhauser at the University of Alberta, Canada; Kathryn F. Husband and Simon W. Poulton at the University of Leeds, United Kingdom; Gail L. Arnold at the Max Planck Institute for Marine Microbiology, Germany; Boswell A. Wing at McGill University, Canada; and Andrey Bekker at the University of Manitoba, Canada.
The idea for the study was a direct consequence of the 2011 Nature paper by Planavsky, Scott, Lyons and others that challenged the hypothesis of broadly sulfidic oceans.
The international collaboration received funding for the study from numerous sources. In the U.S., funding came from the National Science Foundation, the NASA Astrobiology Institute and the Agouron Institute.
Researchers Find First Evidence of Ice Age Wolves in Nevada
Dec. 13, 2012 — A University of Nevada, Las Vegas research team recently unearthed fossil remains from an extinct wolf species in a wash northwest of Las Vegas, revealing the first evidence that the Ice Age mammal once lived in Nevada.
The metapodial, or foot bone, was uncovered late last year by UNLV geologist Josh Bonde during a survey of the Upper Las Vegas Wash. They have now confirmed that the bone comes from a dire wolf.
The discovery site is near the proposed Tule Springs Fossil Beds National Monument, a fossil-rich area known for its diversity and abundance of Ice Age animal remains. Scientists estimate the fossil to be 10,000 to 15,000 years old during the Late Pleistocene period.
“Dire wolves are known to have lived in almost all of North America south of Canada, but their historical presence in Nevada has been absent until now,” said Bonde, a UNLV geology professor. He was a Ph.D. student at the university when he discovered the bone.
“The Tule Springs area has turned up many species, but it’s exciting to fill in another part of the map for this animal and reveal a bit more about the Ice Age ecosystem in Southern Nevada.”
The dire wolf, a larger relative of the gray wolf, was present in much of North and South America for more than a million years. Scientists theorize that competition from other wolf species and a possible food scarcity led to its extinction roughly 10,000 years ago.
Foot bones of the extinct dire wolf are difficult to distinguish from those of the gray wolf. Researchers conclude bone is likely from a dire wolf because of the abundance of dire wolf fossils―and scarcity of gray wolf fossils―in similar-aged excavation sites throughout the Southwest.
Fossil remains of dire wolves are abundant in the La Brea tar pits and have been found in other Southwestern states. Many of the same species of Ice Age animals found at La Brea have also been recovered in the Las Vegas Valley, including Columbian mammoths, camels, horses, bison, and ground sloths.
“This discovery helps flesh out Southern Nevada’s Pleistocene ecosystem and shows that there are still important discoveries to be made in the Upper Las Vegas Wash,” said UNLV geology professor Steve Rowland, a collaborator with Bonde on the study of local Ice Age fossils. “To understand why certain species became extinct and others did not, we need to learn as much as possible about predatory habits and which species were especially sensitive to changes in the environment.”
The announcement comes on the heels of a recent discovery in the same wash of a saber-tooth cat by researchers from the San Bernardino County Museum. Like dire wolves, saber-tooth cats were Pleistocene predators that had been conspicuously absent from the Southern Nevada fossil record.
According to Rowland, Tule Springs was a spring-fed, swampy area during periods of the Late Pleistocene, an ideal spot for plant-eating animals and their carnivorous predators.
The recent discoveries come exactly 50 years after scientists conducted a ‘big dig’ at Tule Springs, revealing the site to be rich with Ice Age fossils.
“Tule Springs likely had the highest density of large animals in the area during the Late Pleistocene, and the marshy environment was very good for preserving at least some of the bones and teeth of animals that died there,” said Rowland.
“In the 50 years since the ‘big dig,’ the scientists have confirmed that humans interacted with Ice Age animals. We now have a new list of questions about life and death in the Pleistocene, and a new tool kit of research techniques to help us get the answers.”
The identity of the find was confirmed by Xiaoming Wang of the Los Angeles County Museum of Natural History, an expert on extinct species of the dog family. Bonde has been surveying the Tule Springs area since 2007, and he and a group of UNLV undergraduate studentss are prospecting for more fossils.
The center of the original ‘big dig’ is on the same parcel of land where Bonde discovered the wolf fossil.
The dire wolf bone, in addition to other bones collected by UNLV researchers, are cataloged, studied, and stored at UNLV.
Rare Fossil Related to Crabs, Lobsters, Shrimp: Exceptionally Well Preserved, Including Shell and Soft Parts
Dec. 12, 2012 — An international team of researchers have made an extremely rare discovery of a species of animal — related to crabs, lobsters and shrimps — that is new to science.
Scientists from the universities of Leicester, Oxford, Imperial and Yale have announced their discovery of a new and scientifically important fossil species of ostracod in the journal Proceedings of The Royal Society B. The research was funded by the Natural Environment Research Council.
The discovered species, which is up to 10 millimetres long, is special because it is exceptionally well preserved, complete with not only the shell but also the soft parts — its body, limbs, eyes, gills and alimentary system. Such discoveries are extremely rare in the fossil record.
The discovery of the tiny shelled arthropod was made in 425 million year old rocks in Herefordshire, Welsh Borderland. The rocks at the site date to the Silurian period of geological time, when southern Britain was a sea area on a small continent situated in warm, southerly subtropical latitudes. The ostracods and associated marine animals living there were covered by a fall of volcanic ash that preserved them frozen in time.
Professor David Siveter, of the University of Leicester Department of Geology, said: “The two ostracod specimens discovered represent a genus and species new to science, named Pauline avibella. The genus is named in honour of a special person and avibella means ‘beautiful bird’, so-named because of the fancied resemblance of a prominent feature of the shell to the wing of a bird.”
“Ostracods are the most abundant fossil arthropods, occurring ubiquitously as bivalved shells in rocks of the last 490 million years, and are common in most water environments today. The find is important because it is one of only a handful preserving the fossilised soft-tissues of ostracods. Its assignment to a particular group of ostracods based on knowledge of its biology is at odds with its shell form, thus urging caution in interpreting the classification of fossil ostracods based on shell characters alone.”
“The preservation of soft-parts of animals is a very rare occurrence in the fossil record and allows unparalleled insight into the ancient biology, community structure and evolution of animals — key facts that that would otherwise be lost to science. The fossils known from the Herefordshire site show soft-part preservation and are of global importance.”
The fossils were reconstructed ‘virtually’, by using a technique that involves grinding each specimen down, layer by layer, and photographing it at each stage. Ten millimetres is relatively tiny, but at an incremental level of 20 µm (micrometres) that yields 500 slices, which can then be pieced together in a computer to provide a full, three-dimensional image of each fossil, outside and in.
Professor Siveter added: “Fossil discoveries in general help elucidate our own place in the tree of life. This discovery adds another piece of knowledge in the jigsaw of understanding the diversity and evolution of animals.”
“It is exciting to discover that a common group of fossils that we thought we knew a lot about may well have been hood-winking us as to their true identity, which we now realise because we have their beautifully fossilised soft-parts. A case of a ‘wolf in sheep’s clothing’.”
The research was undertaken together with Professor Derek Siveter and Dr Sarah Joomun (Oxford), Dr Mark Sutton (Imperial College London) and Professor Derek Briggs (Yale, USA).
Note: The genus is named in honour of Pauline Siveter, in memoriam, late wife of the lead author of the paper.
Emergence of Flowering Plants: New Light Shed On Darwin’s ‘Abominable Mystery’
Dec. 6, 2012 — Research by Indiana University paleobotanist David L. Dilcher and colleagues in Europe sheds new light on what Charles Darwin famously called “an abominable mystery”: the apparently sudden appearance and rapid spread of flowering plants in the fossil record.
Writing in the Proceedings of the National Academy of Sciences, the researchers present a scenario in which flowering plants, or angiosperms, evolved and colonized various types of aquatic environments over about 45 million years in the early to middle Cretaceous Period.
Dilcher is professor emeritus at IU Bloomington in the departments of geological science and biology, both in the College of Arts and Sciences. Co-authors of the paper, published online this week, are Clément Coiffard of the Leibniz Institute for Evolution and Biodiversity Research in Berlin and Bernard Gomez and Véronique Daviero-Gomez of the National Center for Scientific Research in Lyon, France.
The paper draws on extensive fossil data from Europe, providing a comprehensive picture of how angiosperms evolved and connecting their evolution with changes in the physical and biological environments. Dilcher, who has studied the rise and spread of flowering plants for decades, said the scenario is consistent with findings from the fossil record in North America, including his own work showing that angiosperms occupied a variety of aquatic and near-aquatic environments.
“This attention to the total picture of plant groups and the paleo-environment begins to form a pattern,” Dilcher said. “We’re able to turn the pages of time with a little more precision.”
Darwin wrote to Joseph Dalton Hooker in 1879, about 20 years after the publication of “On the Origin of Species,” that the rapid development of higher plants in recent geological times was “an abominable mystery.” The issue has long preoccupied paleobotanists, with competing theories seeking to explain how angiosperms supplanted ferns and gymnosperms in many regions of the globe.
Dilcher and his colleagues show that angiosperms successfully invaded certain environments, gradually spreading to others. They write that angiosperms migrated to new environments in three phases:
— Freshwater lake-related wetlands between 130 million and 125 million years ago — Understory floodplains between 125 million and 100 million years ago — Natural levees, back swamps and coastal swamps between 100 million and 84 million years ago
While paleobotanists once focused on collecting fossil flora and trying to make connections with present-day varieties, Dilcher and his colleagues have produced new insights into the evolutionary biology of flowering plants through close analysis of morphology and anatomy.
Dilcher added that co-evolution with insects gave angiosperms an evolutionary advantage. Insects played a vital role in cross-pollinating plants and accelerating the spread of genetic material. Plants evolved the means to “advertise themselves” with fragrances and bright colors while producing pollen and nectar that provided food for insects.