68 posts · 23,323 views
Laelaps
68 posts
Sort by Latest Post, Most Popular
View by Condensed, Full
- March 12, 2010
- 11:22 AM
- 36 views
Your Friday Dose of Weird: Two new Cambrian critters
When it comes to aliens, Hollywood really does not have much imagination. Most extraterrestrials that have appeared on the big screen look very much like us, or are at least some kind of four-to-six-limbed vertebrate, and this says more about out own vanity than anything else. It would be far more interesting, I think, to take the weird and wonderful organisms of the Cambrian as inspiration for alien life forms, and two new critters have just been added to the odd Cambrian menagerie. Read the rest of this post... | Read the comments on this post...... Read more »
Caron, J., Conway Morris, S., & Shu, D. (2010) Tentaculate Fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) Interpreted as Primitive Deuterostomes. PLoS ONE, 5(3). DOI: 10.1371/journal.pone.0009586
STEIN, M. (2010) A new arthropod from the Early Cambrian of North Greenland, with a ‘great appendage’-like antennula. Zoological Journal of the Linnean Society, 158(3), 477-500. DOI: 10.1111/j.1096-3642.2009.00562.x
- March 10, 2010
- 05:41 PM
- 34 views
Prehistoric DNA reveals the story of a Pleistocene survivor, the muskox
A muskox (Ovibos moschatus), photographed in Alaska. From Flickr user drurydrama.
Of all the mass extinctions that have occurred during earth's history, among the most hotly debated is the one which wiped out mammoths, saber-toothed cats, giant ground sloths, and the other peculiar members of the Pleistocene megafauna around 12,000 years ago. It was not the most severe mass extinction, not by a long shot, but unlike the end-Cretaceous catastrophe 65 million years ago there is no single "smoking gun" that can account for the pattern of extinction. Instead the Pleistocene mass extinction remains a very mysterious event, but by looking at the natural history of one of the event's survivors scientists have been able to get a better idea about how one of the suspected extinction triggers affected prehistoric mammals.
Today's populations of muskox (Ovibos moschatus) are remnants of the Pleistocene herds which were once spread all around the Arctic Circle. The shaggy bovids are survivors of the events which wiped out so many other large mammals, but this does not mean that they were immune to ecological changes that may have played a pivotal role in the extinction. As illustrated by a new paper in the journal PNAS, the changing climate had a major influence on muskox populations, and by looking at what happened to them it may be possible to understand the fate of some of their extinct contemporaries. Read the rest of this post... | Read the comments on this post...... Read more »
Campos, P., Willerslev, E., Sher, A., Orlando, L., Axelsson, E., Tikhonov, A., Aaris-Sorensen, K., Greenwood, A., Kahlke, R., Kosintsev, P.... (2010) Ancient DNA analyses exclude humans as the driving force behind late Pleistocene musk ox (Ovibos moschatus) population dynamics. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0907189107
- March 9, 2010
- 02:35 PM
- 54 views
Evolutionary history of early primates places human origins in context
A simplified evolutionary tree of primate relationships showing the placement of Darwinius in relationship to other groups. From Williams et al., 2010.
The study of human origins can be a paradoxical thing. We know that we evolved from ancestral apes (and, in fact, are just one peculiar kind of ape), yet we are obsessed with the features that distinguish us from our close relatives. The "big questions" in evolutionary anthropology, from why we stand upright to how our brains became so large, are all centered around distancing us from a prehistoric ape baseline. Despite our preoccupation with "human uniqueness", however, many of our traits are extremely ancient, and they can be traced back much further than the seven million years or so that hominins have existed.
As acknowledged by paleontologists Blythe Williams, Richard Kay, and Christopher Kirk (who confirmed that Darwinius was only a very distant relative of ours last week) in a new PNAS paper, "human evolution did not begin 6-8 million years ago with the phylogenetic split between the chimpanzee and human lineages." It is not as if the first hominins appeared out of nothing and began an upward march to us. Instead we know that we could hypothetically trace our lineage all the way back to the last common ancestor of all life on earth, and any point we chose to stop along that "unbroken thread" could tell us quite a bit about our history. In the case of the present review, Williams, Kay, and Kirk pick up with the origin of anthropoid primates. Read the rest of this post... | Read the comments on this post...... Read more »
Williams, B., Kay, R., & Kirk, E. (2010) New perspectives on anthropoid origins. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0908320107
- March 5, 2010
- 10:37 AM
- 51 views
Finding a home for jaguars
A jaguar (Panthera onca). From Flickr user Prosper 973.
One year ago this week Macho B was euthanized. He had been captured in mid-February of 2009, the only known jaguar living inside the United States, but after he was caught and fitted with a radio collar his health quickly deteriorated. When he nearly stopped moving he was recaptured, taken to the Phoenix zoo, and put to sleep when it was discovered that he was suffering from irreparable kidney failure.
At first it seemed as if his capture was a lucky accident, but a later investigation by the Fish and Wildlife Service found that the snare had been intentionally laid (without proper notification) in an area Macho B was known to have frequented. This may have hastened his death. At the time of his capture Macho B was at least 14, pretty old for jaguar, and it is possible that the stress of his capture is what triggered his decline. Since the necropsy on his body was incomplete, however, we can never know for sure.
But Macho B was probably not the last jaguar to cross the border from Mexico into the United States. At the same time that the report on Macho B's death was making the news it was discovered that another jaguar had been spotted just 30 miles to the south of the US border. There may no longer be any resident jaguars inside the United States, but big cats along the borderlands continue to cross the nation's southern boundary. As two recent studies illustrate, however, this northern population is only part of a network of jaguars conservationists are trying to hold together. Read the rest of this post... | Read the comments on this post...... Read more »
Rabinowitz, A., & Zeller, K. (2010) A range-wide model of landscape connectivity and conservation for the jaguar, Panthera onca. Biological Conservation. DOI: 10.1016/j.biocon.2010.01.002
ROSAS-ROSAS, O., & VALDEZ, R. (2010) The Role of Landowners in Jaguar Conservation in Sonora, Mexico. Conservation Biology. DOI: 10.1111/j.1523-1739.2009.01441.x
- March 3, 2010
- 08:16 AM
- 55 views
New Study Confirms That "Ida" is Not Our Great-Great-Great-Great-Etc. Grandmother
The exceptionally preserved skeleton of Darwinius, known popularly as "Ida." From PLoS One.
Almost ten months ago an international team of researchers introduced the world to an exquisitely-preserved primate from the 47 million year old oil shales of Messel, Germany. Dubbed Darwinius masillae, and nicknamed "Ida" and "The Link", the fossil was touted as one of our earliest primate ancestors in a massive media campaign worthy of a Hollywood blockbuster. Yet the trouble was that there was no solid evidence that Darwinius was one of our ancestors. Despite the marketing blitz promoting the fossil the team of scientists who described it did not provide sufficient evidence that the lemur-like primate was anywhere close to our ancestry, and it would take the description of a related fossil primate several months later to put "Ida" in her place. Darwinius was not one of our ancient progenitors, as had been proclaimed, but instead belonged to an extinct branch of early primates which were more closely related to living lemurs and lorises.
Now another team of early primate experts has published a new analysis of the famous fossil. Writing in the Journal of Human Evolution paleontologists Blythe Williams, Richard Kay, Christopher Kirk, and Callum Ross have independently confirmed that the original description of Darwinius which appeared in the journal PLoS One was deeply flawed. Understanding why, however, requires a bit of background. Read the rest of this post... | Read the comments on this post...... Read more »
Williams, B., Kay, R., Christopher Kirk, E., & Ross, C. (2010) Darwinius masillae is a strepsirrhine—a reply to Franzen et al. (2009). Journal of Human Evolution. DOI: 10.1016/j.jhevol.2010.01.003
- March 1, 2010
- 11:42 AM
- 59 views
Uncovering the "Chimpanzee Stone Age"
An adult chimpanzee in Bossou, Guinea uses hammer and anvil stones to crack nuts as younger individuals look on. From Haslam et al., 2009.
Before 1859 the idea that humans lived alongside the mammoths, ground sloths, and saber-toothed cats of the not-too-distant past was almost heretical. Not only was there no irrefutable evidence that our species stretched so far back in time, but the very notion that we could have survived alongside such imposing Pleistocene mammals strained credulity. Contrary to what might be immediately expected, however, it was not Darwin's famous abstract On the Origin of Species that changed appraisals of human prehistory. Instead it was a collection of stone tools found mingled among the bones of extinct mammals found in deposits on either side of the English Channel.
The discovery of stone tools from places like Brixham Cave in England and France's Somme Valley confirmed that industry was a very old human enterprise, and so some scholars naturally felt quite comfortable in giving out species the honorary title of "Man the Toolmaker." The ability of our species to make and use tools clearly separated us from all other organisms, at least until it was discovered that chimpanzees, too, made and used tools. More than that, studies since the 1960's have confirmed that different populations of chimpanzees have distinctive tool cultures affected by the contingencies of their surroundings, and a recent study published two years ago in PNAS illustrates that these cultures of tool use among non-human primates stretch back at least 4,300 years. Read the rest of this post... | Read the comments on this post...... Read more »
Mercader, J., Barton, H., Gillespie, J., Harris, J., Kuhn, S., Tyler, R., & Boesch, C. (2007) 4,300-Year-old chimpanzee sites and the origins of percussive stone technology. Proceedings of the National Academy of Sciences, 104(9), 3043-3048. DOI: 10.1073/pnas.0607909104
- February 27, 2010
- 11:08 AM
- 59 views
"You just call out my name...": Friendships in Male and Female Baboons
Male (right) and female (left, with infant) friends in a population of Chacma baboons. (From Palombit, 2009).
Among other things, friends are people you count on to come to your aid when you need help. If you were at a bar and a stranger started acting aggressively towards you, for example, you would expect your friends to rush over to help you rather than just stand there, mojito in hand. Contrary to our feelings of human exceptionalism, however, ours is not the only species of primate to create and maintain friendships.
For years primatologists have been puzzling over "friendship" in baboons. Across baboon species lactating females keep up close social relationships with unrelated adult males. The females are not reproductively available, and by devoting much of their attention to these females the males significantly reduce their opportunities to mate with other females, so why are these males so concerned with mothers and infants? What is the function of this behavior?
Several hypotheses have been forwarded. Perhaps friendship is a defense against infanticide, a way to reduce harassment of mothers and their infants by other group members, or a way for mothers to get their infants to bond with particular males so that they will continue to reap social benefits (such as food sharing and support during fights) as they mature. Of these, however, friendship as an anti-infanticide mechanism appears to be best-supported, especially since infanticide is a major cause of mortality among infant Chacma baboons. Baboon social groups are centered around female families that stick together, but males often move from one group to another. As a result immigrant males occasionally supplant the group's dominant male, and when this happens among Chacma baboons the new alpha picks off the group's infants one-by-one (hence the group's females come back into estrus sooner). In such situations a friendship between a male and female baboon can make the difference between life and death for her offspring.
That male friends provide such protection was confirmed through playback experiments in the field. When the distress calls of female Chacma baboons with infants were played in the vicinity of their friends the males reacted strongly to the sound by trying to find where that female was and determine if she was in danger. The control subjects, males of similar social rank but were not friends, glanced up when the sound was played but quickly went back to whatever they were doing. These results reaffirmed that at least part of the role of male friendship was to offer protection to mothers with infants.
Yet the threat of infanticide varies among baboon species even as friendships remain a common phenomenon. In olive baboons, for example, infanticide by an immigrant male is a rare event rather than the norm, and primatologists A. Lemasson, Ryne Palombit, R. Jubin took this as an opportunity to see if friendships in this species involved protection from harassment or some other social benefit. If male friends provide protection for mothers and infants then they would react strongly to distress calls, just like the Chacma baboons, but if the function of friendship is to provide infants with social benefits later in life it would be predicted that males would not be as concerned upon hearing the female's screams. To test this idea the scientists arranged a second playback experiment published in Behavioral Ecology and Sociobiology. Read the rest of this post... | Read the comments on this post...... Read more »
Lemasson, A., Palombit, R., & Jubin, R. (2007) Friendships between males and lactating females in a free-ranging group of olive baboons (Papio hamadryas anubis): evidence from playback experiments. Behavioral Ecology and Sociobiology, 62(6), 1027-1035. DOI: 10.1007/s00265-007-0530-z
- February 24, 2010
- 06:16 PM
- 59 views
"Horned" crocodile may have preyed upon prehistoric humans
A Cuban crocodile (Crocodylus rhombifer), photographed at the National Zoo.
No one knew what happened to William Olson. At about three in the afternoon on April 13, 1966 he had been swimming with his friends from the Peace Corps in the part of the Baro river that ran through Gambela, Ethiopia when he suddenly disappeared. The last person to remember seeing him was hunter Karl Luthy. One moment Olson was standing in the river, pressing his body against the current, and the next he was gone.
Luthy could not be sure, but he was almost certain that Olson had been taken by a Nile crocodile. He and the people who lived in the nearby village had warned the young travelers that swimming in the river was dangerous, especially since a child and a woman had been recently devoured by a crocodile there, but the American visitors did not care. Luthy's fears were confirmed about a half hour after attack. Just at the edge of sight the crocodile appeared with Olson's body in its jaws, but rather than go after the animal right away Luthy decided to wait until morning. Rushing to kill the reptile would do no good. Olson was already dead, and if Luthy attempted to shoot to crocodile while it was still in the river both the animal and Olson's body might be lost. Instead he decided to leave the predator be until morning when it came out of the water to bask in the sun.
The crocodile did just as Luthy predicted. It hauled itself out onto the riverbank at about seven the next morning, and after a few attempts Luthy and his client were able to kill it. When they opened it up there could be no doubt that the thirteen-foot long crocodile was the one that had killed Olson. What was left of the young man was placed in a cardboard box.
Such tragic events remind us that we are not separate from or above nature. Much like our hominin forebears we can still be prey, and crocodiles are among the animals that have long considered us to be on the menu. Fragmentary remains of fossil hominins from the famous locality Olduvai Gorge, especially, show tell-tale signs that crocodiles consumed the bodies of our ancient relatives, and new fossils from the 1.8 million year old rocks there have identified one of the possible culprits. Read the rest of this post... | Read the comments on this post...... Read more »
Brochu, C., Njau, J., Blumenschine, R., & Densmore, L. (2010) A New Horned Crocodile from the Plio-Pleistocene Hominid Sites at Olduvai Gorge, Tanzania. PLoS ONE, 5(2). DOI: 10.1371/journal.pone.0009333
- February 22, 2010
- 07:49 AM
- 55 views
Ancient shark was a shell-crushing giant
An outline of the upper jaw of Ptychodus mortoni showing the position of the new fragment, and a comparison of the size of the shark next to an adult human. (From Shimada et al., 2010)
The study of prehistoric sharks is no easy task. Specialists in other branches of vertebrate paleontology at least have the reasonable hope of discovering complete skeletons of their subjects; except in instances of exceptional preservation the scientists who study sharks typically only have teeth and a few vertebrae to work with. Still, you can tell a lot about a shark by its teeth, and a new study published in Cretaceous Research suggests that one peculiar form was a shell-crushing giant.
Thanks to Jaws, "Shark Week", and other sensationalist films the word "shark" most immediately conjures up images of streamlined predators with triangular, razor-sharp teeth. For much of the public the great white shark (Carcharodon carcharias) is the epitome of "sharkiness", but there is a much wider variety of shark types. The largest fish in the sea, the whale shark (Rhincodon typus) is a filter feeder with teeth smaller than your fingernails, while the much smaller Port Jackson shark (Heterodontus portusjacksoni) has differentiated teeth adapted for crushing mollusks. And, just like today, there was a diversity of shark types in the past. One of the most enigmatic was the Late Cretaceous form Ptychodus mortoni. Read the rest of this post... | Read the comments on this post...... Read more »
Shimada, K., Everhart, M., Decker, R., & Decker, P. (2010) A new skeletal remain of the durophagous shark, Ptychodus mortoni, from the Upper Cretaceous of North America: an indication of gigantic body size. Cretaceous Research, 31(2), 249-254. DOI: 10.1016/j.cretres.2009.11.005
- February 15, 2010
- 11:12 AM
- 64 views
Broken teeth tell of tough times for Smilodon
A reconstruction of Smilodon, photographed at the American Museum of Natural History.
When it comes to animals, encyclopedias often present us with generalized descriptions. Where a creature lives, what color it is, what it eats, and other tidbits of information are listed to distinguish one species from another, but what is lost is an appreciation of variation. Be they genetic, anatomical, or behavioral, variations are grist for natural selection's mill, and if you study any species in detail it becomes apparent that individuals differ considerably over space and through time.
This was true of extinct animals just as it is true of living ones. When paleontologists Wendy Binder and Blaire Van Valkenburgh looked at the wear and breakage of dire wolf teeth from the famous La Brea tar pits site in Los Angeles, for example, they found that the specimens from 15,000 years ago damaged or broke their teeth three times as much as specimens from 12,000 years ago. For some unknown reason, it appeared that the older population damaged their teeth by chewing on bones more frequently than the younger population.
But dire wolves are not the only carnivores to be found in the ancient death trap. The saber-toothed cat Smilodon fatalis is represented by numerous specimens, as well, and after their dire wolf study Binder and Van Valkenburgh turned their attention to the most famous of American sabertooths. The result of that study, published in the Journal of Vertebrate Paleontology, suggests that, like the wolves, the cats at Rancho La Brea changed their eating habits over time. Read the rest of this post... | Read the comments on this post...... Read more »
Wendy J. Binder; Blaire Van Valkenburgh. (2010) A comparison of tooth wear and breakage in Rancho La Brea Sabertooth Cats and dire wolves across time. Journal of Verterbrate Paleontology, 30(1), 255-161. info:/10.1080/02724630903413016
- February 3, 2010
- 11:13 AM
- 106 views
New study names a Titanoboa menu item
A restoration of Titanoboa (foreground) and Cerrejonisuchus improcerus (background, left) in their natural setting. (By Jason Bourque, image from Wikipedia.)
When I was growing up I used to spend hours poring over the Time/Life series of nature books in my little library, absolutely enthralled by images of strange creatures from all over the world, but one photograph was particularly arresting. A grainy black-and-white double-page spread showed an anaconda that had wrapped its crushing coils around a caiman and a tree, slowly squeezing the life out of the crocodylian. Without any frame of reference for size it was easy to envision the two animals as giants, but that was just my b-movie fueled imagination running wild. Even though both anacondas and caimans are large reptiles they do not achieve the monstrous proportions seen in late night creature features.
As discovered by scientists last year, however, in the wake of the mass extinction that wiped out the non-avian dinosaurs a cousin of living anacondas grew to prodigious size. Named Titanoboa, this 60 million year old snake was at least 40 feet long and lived in an ancient swamp in what is now Colombia. That same habitat was also inhabited by plenty of potential prey, from fish to turtles, and one of the larger potential menu items has just been described by paleontologists Alexander Hastings, Jonathan Bloch, Edwin Cadena, and Carlos Jaramillo in the latest Journal of Vertebrate Paleontology. Read the rest of this post... | Read the comments on this post...... Read more »
Alexander K. Hastings; Jonathan I. Bloch; Edwin A. Cadena; Carlos A. Jaramillo. (2010) A new small short-snouted dyrosaurid (Crocodylomorpha, Mesoeucrocodylia) from the Paleocene of northeastern Colombia. Journal of Verterbrate Paleontology, 30(1), 139-162. info:/10.1080/02724630903409204
- February 2, 2010
- 11:03 AM
- 93 views
The Fearsome Short-Faced Bear Gets a Makeover
A grizzly bear (the black dot in the middle of the photo) walking near the treeline in Yellowstone's Hayden Valley.
The quiet of my evening wildlife watching was suddenly broken by a thick Boston accent. "Oh my gawd! Look! It's a grizz! That's the last animal I needed to see! It's a grizz!"
He was right. Lumbering across the valley was a big dark shape that could only be a bear. It was not very close, being little more than a dot moving along the distant treeline, but through the zoom lens of my camera it was just possible to make out the hump that distinguishes black bears from grizzly bears. It was the closest I would get to Yellowstone's largest predator during my visit to the national park (at least that I know of), but in the not-too-distant past an even larger cousin of the grizzly roamed much of North America.
Three visions of the short-faced bear: Arctodus as a predator, a scavenger, and an herbivore. By Oscar San-Isidro, from Figueirido et al., 2010
Arctodus simus, the short-faced bear, was part of the recently-lost Pleistocene megafauna which disappeared from this continent around 11,000 years ago. The first human inhabitants of this continent undoubtedly encountered it from time to time, and the prospect of meeting a bear which stood five feet at the shoulder is a chilling one. It was the epitome of the big, bad bear, but just how bad was it? As argued by paleontologists Borja Figueirido, Juan Perez-Claros, Vanessa Torregrosa, Alberto Martin-Serra, and Paul Palmqvist, the popular image of the short-faced bear as a hypercarnivorous superpredator may have obscured the reality of the beast. Read the rest of this post... | Read the comments on this post...... Read more »
Figueirido, Borja, Pérez-Claros, Juan A., Torregrosa, Vanessa, Martín-Serra, Alberto and Palmqvist,, & Paul. (2010) Demythologizing Arctodus simus, the 'Short-Faced' long-legged and predaceous bear that never was. Journal of Verterbrate Paleontology, 30(1), 262-275. info:/10.1080/02724630903416027
- January 28, 2010
- 04:18 PM
- 122 views
Evo. Anthro. Study Suggests You Might Be Running Wrong
"The Barefoot Professor", a behind-the-scenes look at the new Nature paper.
Humans that had to escape from saber-toothed cats, giant hyenas, and charging mammoths did not wear Nike or Adidas sneakers. They ran barefoot, but don't feel too bad that they did not have good running shoes to help them. As suggested by a team of researchers led by Daniel Lieberman in the latest issue of Nature, habitually shoeless runners have a unique step that may be better for our feet than even the most expensive, cushioned running shoe. Read the rest of this post... | Read the comments on this post...... Read more »
Lieberman, D., Venkadesan, M., Werbel, W., Daoud, A., D’Andrea, S., Davis, I., Mang’Eni, R., & Pitsiladis, Y. (2010) Foot strike patterns and collision forces in habitually barefoot versus shod runners. Nature, 463(7280), 531-535. DOI: 10.1038/nature08723
- January 20, 2010
- 05:47 PM
- 138 views
Surf's up!: How rafting lemurs colonized Madagascar
A ring-tailed lemur (Lemur catta), photographed at the Bronx Zoo.
Who doesn't love lemurs? The strepsirrhine primates, or wet-nosed cousins of ours, are favorite documentary subjects and extremely popular zoo attractions. And, in one of those bits of zoological trivia that everyone knows, lemurs only live on the island of Madagascar off Africa's southeastern coast. The question is how they got there.
Documenting the paths of animals during geological history is not an easy task. In the days before scientists understood plate tectonics, land bridges, now sunk beneath the ocean, were often used to explain the dispersal of organisms. While some land bridges did exist in the past, like the one that allowed mammoths to cross from modern-day Russia to North America, they were not nearly as widespread as had once been thought. Instead many scientists began to think about how organisms might float their way to new places by becoming accidental passengers on bits of vegetative detritus. As articulated by paleontologist G.G. Simpson, this was a kind of "sweepstakes" in which creatures would be cast out to sea on floating mats of plant matter and of those wayward animals a few might be washed up in a new habitat able to support them. From these few survivors of tropical storms entirely new ecologies could become established.
The trouble with this was that the currents surrounding Madagascar circulate in a way that would make it very difficult for any raft to make it to the island. Maybe the unique island fauna could be attributed to a land bridge, after all. Neither option seemed entirely satisfactory, but, in a paper just published in Nature, scientists Jason Ali and Matthew Huber took another look at the sweepstakes hypothesis. As it turns out, the currents surrounding Madagascar might have been more of a help than a hindrance in transporting rafting animals to the island. Read the rest of this post... | Read the comments on this post...... Read more »
Ali, J., & Huber, M. (2010) Mammalian biodiversity on Madagascar controlled by ocean currents. Nature. DOI: 10.1038/nature08706
- January 19, 2010
- 05:20 PM
- 134 views
An Ancient, "Hidden" Elephant Gets a New Name
The restored lower jaw of Arcanotherium (formerly Numidotherium savagei). (From Delmer, 2009)
Unlike the folks at this past weekend's ScienceOnline 2010 meeting, fossils don't come with nametags. The identification of preserved bits of ancient life relies upon careful comparison with what is already known, a task made all the more difficult for vertebrate paleontologists by the fragmentary nature of many of their subjects. Scraps of bone given one name could turn out to be parts of another partial skeleton given another name, or other bits of bone attributed one name could turn out to be something entirely new. Reexaminations and revisions are ongoing, and one effort to rearrange a petrified puzzle led to the origin of a new elephant from an old one.
Since the beginning of the 20th century the place to took for the early relatives of elephants has been northern Africa. There, in the Fayum desert of Egypt and in Dor El Talha, Libya, numerous proboscideans (the group to which elephants belong) have been discovered. At first it seemed that the fossils could be organized in a step-by-step fashion, documenting a linear march of elephant evolution, but continued discoveries have presented scientists with a diversity of strange early elephants quite different from the paltry collection of living species. Among this early radiation was Numidotherium, a medium-sized genus known from a nearly-complete skeleton. Read the rest of this post... | Read the comments on this post...... Read more »
Delmer, C. (2009) Reassessment of the generic attribution of Numidotherium savagei and the homologies of lower incisors in proboscideans. Acta Palaeontologica Polonica. DOI: 10.4202/app.2007.0036
- January 12, 2010
- 01:25 PM
- 160 views
Did the "Marsupial Lion" Climb Trees?
Restoration of the skull of Thylacoleo. From The Ancient Life History of the Earth.
Thylacoleo was one strange mammal. A close relative of living koalas, kangaroos, and wombats, the largest species of Thylacoleo were lion-sized carnivores that stalked the Australian continent between 2 million and 45 thousand years ago. Despite its popular nickname "marsupial lion", however, Thylacoleo was quite different from any feline predator. Even though its long forelimbs were tipped with retractable claws its skull more closely resembled that of a koala, with curved incisors set in front of a pair of cleaver-like shearing teeth. This resemblance caused some naturalists to believe that Thylacoleo was just another herbivore, but more recent studies have confirmed that it most certainly was a carnivore.
But what kind of predator was Thylacoleo? Some have proposed that it hunted down prey and then dragged it into the trees, as a leopard does, while others have argued that it was more lion-like in habit. The entire argument hinges upon whether Thylacoleo could climb trees or not, which in turn rests on our understanding of the predator's anatomy. The details of the skeleton of Thylacoleo, particularly its hands and feet, can provide paleontologists with clues as to what it was capable of. Unfortunately scientists have had to cope with an incomplete understanding of the hind feet of Thylacoleo for years, but a recent discovery from an Australian cave has brought new information to the discussion. As reported by paleontologists Roderick Wells, Peter Murray, and Steven Bourne in the latest issue of the Journal of Vertebrate Paleontology a complete hind foot of Thylacoleo has finally been found. Read the rest of this post... | Read the comments on this post...... Read more »
Wells, R., Murray, P., & Bourne, S. (2009) Pedal Morphology of the Marsupial Lion (Diprotodontia: Thylacoleonidae) from the Pleistocene of Australia . Journal of Vertebrate Paleontology, 29(4), 1335-1340. DOI: 10.1671/039.029.0424
- January 8, 2010
- 09:42 AM
- 175 views
An itty-bitty armored mammal
A comparison between the complete skull of a Glyptodon and the skull fragments of a fetal specimen. (From Zurita et al, 2009)
Early in 2009 a team of paleontologists led by Philip Gingerich announced the discovery of a baby archaeocete (early whale) embedded inside the skeleton of an adult of the same species. Since these fossils represented a new species of fossil whale to boot the story was immediately picked up by news outlets, but less well-publicized was another discovery made later the same year. In the pages of Comptes Rendus Palevol paleontologists Alfredo Zurita, Angel Mino-Boilinia, Esteban Soibelzon, Gustavo Scillato-Yane, German Gasparini, and Freddy Paredes-Ríos described an unborn specimen of a very different kind of mammal; an armored relative of living armadillos called Glyptodon. Read the rest of this post... | Read the comments on this post...... Read more »
Zurita, A., Miño-Boilini, A., Soibelzon, E., Scillato-Yané, G., Gasparini, G., & Paredes-Ríos, F. (2009) First record and description of an exceptional unborn specimen of Cingulata Glyptodontidae: Glyptodon Owen (Xenarthra). Comptes Rendus Palevol, 8(6), 573-578. DOI: 10.1016/j.crpv.2009.04.003
- January 6, 2010
- 05:10 PM
- 154 views
Ancient Tracks Question Ideas About Tetrapod Origins
Tiktaalik is practically a household name. Since its description in 2006 the flat-headed "fishapod" has appeared in books, on t-shirts, and has even starred in its own music video. Hailed as a "missing link", Tiktaalik has become a poster child fossil for evolution, but it is hardly the first such creature to be given this honor. Read the rest of this post... | Read the comments on this post...... Read more »
Niedźwiedzki, G., Szrek, P., Narkiewicz, K., Narkiewicz, M., & Ahlberg, P. (2010) Tetrapod trackways from the early Middle Devonian period of Poland. Nature, 463(7277), 43-48. DOI: 10.1038/nature08623
- January 5, 2010
- 10:06 AM
- 186 views
Early "Baleen Whale" Was a Tooth-Bearing Mud-Grubber
A restoration of Mammalodon by Brian Choo (published in Fitzgerald, 2009).
In the introduction to his 1883 lecture on whales, the English anatomist William Henry Flower said;
Few natural groups present so many remarkable, very obvious, and easily appreciated illustrations of several of the most important general laws which appear to have determined the structure of animal bodies, as that selected for my lecture this evening. We shall find the effects of the two opposing forces--that of heredity or conformation to ancestral characters, and that of adaptation to changed environment, whether brought about by the method of natural selection or otherwise--distinctly written in almost every part of their structure. Scarcely anywhere in the animal kingdom do we see so many cases of the persistence of rudimentary and apparently useless organs, those marvellous and suggestive phenomena which at one time seemed hopeless enigmas, causing despair to those who tried to unravel their meaning, looked upon as mere will-of-the-wisps, but now eagerly welcomed as beacons of true light, casting illuminating beams upon the dark and otherwise impenetrable paths through which the organism has travelled on its way to reach the goal of its present condition of existence.
As presented by Flower, whales were excellent examples of evolutionary change. They were mammals well-adapted to life at sea and yet they still retained anatomical quirks which testified to their origin from terrestrial creatures. (And, interestingly, Flower was one of the first naturalists to suggest that whales had evolved from artiodactyls.) Frustratingly, however, only a handful of early fossil whales were known at the time, and while there was no doubt that whales had evolved the fossil proofs of their evolution were largely missing. Naturalists could only speculate on how early whales transitioned into an aquatic lifestyle, and just as mysterious was the origin of the largest animals on earth, the baleen whales. Read the rest of this post... | Read the comments on this post...... Read more »
FITZGERALD, E. (2010) The morphology and systematics of (Cetacea: Mysticeti), a toothed mysticete from the Oligocene of Australia . Zoological Journal of the Linnean Society. DOI: 10.1111/j.1096-3642.2009.00572.x
- December 22, 2009
- 02:46 PM
- 210 views
The extended twilight of the mammoths
One of Charles R. Knight's wonderful paintings of woolly mammoths walking through the snow of ancient Europe. On display at the Field Museum in Chicago.
When did the last woolly mammoths die?
There is no easy answer to the question. In its heyday the woolly mammoth (Mammuthus primigenius) was distributed across much of the northern hemisphere, from southern Spain to the eastern United States, and the entire species did not simply lay down and die at one particular moment. Some populations (such as the "dwarf" mammoths of Wrangel Island) survived until about 4,000 years ago, but most of the populations that lived on the mainland seem to have disappeared just under 13,000 years ago as part of an extinction event that also wiped out giant ground sloths, saber-toothed cats, enormous bison, and other megafauna.
Climate change, an asteroid impact, a superdisease, and hungry hungry humans have all been considered as triggers for the Pleistocene mass extinction, and determining the pattern of extinction has been important to determining what roles (if any) these mechanisms might have played. But even this is oversimplified. The Pleistocene mass extinction was not a uniform event. Some animals survived in one place while close relatives perished in others, and so a key part of figuring out what mechanism(s) caused the extinction is finding out when certain species became extinct.
The trouble is that the first and last representatives of any species are unlikely to be preserved in the fossil record. This means that even though there are fossil remains of mammoths from Europe and Asia dated to a little less than 10,000 years ago it is still difficult to know whether they were truly the last of the mammoths, the fossil record petered out, or we just have not yet found the bones that would extend the temporal range of the mammoth nearer in time. Such are the frustrations with dealing with fossil remains. Only a tiny fraction of all the organisms that ever lived became preserved as fossils, and an even tinier fraction of those have been discovered, hence Charles Darwin's lament that the fossil record is "a history of the world imperfectly kept."
But mammoths were not just shuffling collections of teeth and bones. They were living creatures that bled, defecated, urinated, shed hair, and eventually decomposed, spreading their genetic material all over the land they occupied. This means that there is a second sort of record for the mammoths that, under the right conditions, might be able to provide us with a better idea of where they lived and when they disappeared, and an attempt to mine this rich source of fossil data has just been published in the journal PNAS. Read the rest of this post... | Read the comments on this post...... Read more »
Haile, J., Froese, D., MacPhee, R., Roberts, R., Arnold, L., Reyes, A., Rasmussen, M., Nielsen, R., Brook, B., Robinson, S.... (2009) Ancient DNA reveals late survival of mammoth and horse in interior Alaska. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0912510106
topics
join us!
Do you write about peer-reviewed research in your blog? Use ResearchBlogging.org to make it easy for your readers — and others from around the world — to find your serious posts about academic research.
If you don't have a blog, you can still use our site to learn about fascinating developments in cutting-edge research from around the world.
News
Editor's selections: corporate water abuse, vanishing audiophiles, artificial coffee smelling and 60k-year-old canteens
Editor's Selections: An asteroid killed the dinosaurs, innate immunity and obesity, and vaccinia virus in Brazil
Exploitation Nation: Cheating Microbes, Parasites, and Your Colon
