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Laelaps
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- May 20, 2010
- 09:39 AM
- 1,084 views
Tiny treasures - 100 million year old mammal hairs trapped in amber
Mammal hairs preserved in amber specimen ARC2-A1-3. a - First fragment; b - Line drawing of first fragment; c - Second fragment; d - Line drawing of second fragment; e - Close-up of second fragment to show the cuticular surface.
About 100 million years ago, in a coastal forest located in what is today southwestern France, a small mammal skittered up the trunk of a conifer tree. As it did so it lost a few of its hairs, and this minor event would have been entirely unremarkable if two of those hairs had not settled in some tree sap and, in the course of time, become entombed in a piece of amber which has only recently been discovered. As described by scientists Rumain Vullo, Vincent Girard, Dany Azar, and Didier Neraudeau, this rare specimen gives us a clear look at what the hair of mammals was like during the time when dinosaurs were the dominant vertebrates on land.
Exceptionally-preserved fossil mammals with intact soft tissue remnants have been found before, such as a specimen of the 125 million year old cousin of placental mammals Eomaia, but fur trapped in amber provides a higher level of resolution - it is the original biological material. Likewise, even though hairs trapped in amber have previously been discovered, much of it has come from the past 65 million years, so even though we have every reason to assume that all mammals had hair since the time of their origin during the Mesozoic we don't know very much about what that hair was like. The new specimen from France, specimen ARC2-A1-3, helps to fill this hole in our understanding. Read the rest of this post... | Read the comments on this post...... Read more »
Vullo, R., Girard, V., Azar, D., & Néraudeau, D. (2010) Mammalian hairs in Early Cretaceous amber. Naturwissenschaften. DOI: 10.1007/s00114-010-0677-8
- May 18, 2010
- 08:40 AM
- 1,285 views
The majestic Megatherium
A restoration of Megatherium from H.N. Hutchinson's Extinct Monsters.
For over a century and a half dinosaurs have been the unofficial symbols and ambassadors of paleontology, but this was not always so. It was fossil mammals, not dinosaurs, which enthralled the public during the turn of the 19th century, and arguably the most famous was the enormous ground sloth Megatherium. It was more than just a natural curiosity. The bones of the "great beast" represented a world which flourished and disappeared in the not-so-distant past, but, as illustrated by Christine Argot in a review of its history, illustrations of what Megatherium looked like have been in flux since the time of its discovery.
No doubt humans have been finding the remains of giant ground sloths for quite some time, but the story of Megatherium as we know it began in 1788. It was in that year that Manuel Torres discovered the nearly complete skeleton of an immense, strange animal on the banks of the river Luján about 65 kilometers west of Buenos Aires in northern Argentina. The following year it was shipped to the Cabinet of Natural History in Madrid, Spain where it was assembled and illustrated by Juan Bautista Bru, and it was on the basis of these illustrations that the French anatomist Georges Cuvier was able to determine what this spectacular animal was. He gave it the name Megatherium americanum, and appraised it as an extinct, peculiar creature most similar of the small arboreal sloths which still clung the branches of South American rainforests. As Cuvier did not accept the idea of evolution there could be no genetic connection between the ancient monster and the living sloths, but the similarity between the two could not be denied. Read the rest of this post... | Read the comments on this post...... Read more »
Christine Argot. (2008) Changing Views in Paleontology: The Story of a Giant (Megatherium, Xenarthra). Mammalian Evolutionary Morphology A Tribute to Frederick S. Szalay . DOI: 10.1007/978-1-4020-6997-0_3
- May 17, 2010
- 11:40 AM
- 867 views
Shark mystery solved - how thresher sharks use their tails
The tail of a thresher shark (Alopias vulpinus). From Wikipedia.
Thanks to sensational documentaries and summer blockbusters, we are all familiar with the anatomy of a shark attack. The victim, unaware that they are in peril, is struck from below and behind with such speed and violence that, if they are not actually killed during the first strike, they soon find themselves a few pounds lighter in the middle of a billowing red cloud. The trouble is that this stereotyped scenario does not hold for all sharks, particularly one peculiar group of deepwater sharks which has long puzzled naturalists.
Thresher sharks, represented by three species within the genus Alopias which ran between 10 and 20 feet long, possess the classic shark body plan, but there is one feature that immediately stands out when you look at them - their ludicrously elongated tails. What could such an appendage be used for? Does it help them in propulsion, or do they use their tails as a whip to stun fish before consuming them? This latter hypothesis has been popular for years, especially since threshers are often hauled up on deep-water longlines by their tails (rather than by their mouths, like other sharks), but the only confirmation that this was correct came from anecdotal accounts. Thanks to some underwater cameras, however, scientists S.A. Aalbers, D. Bernal, and C.A. Sepulveda were able to test what has long been assumed about thresher feeding behavior, and their results have just been published in the Journal of Fish Biology. Read the rest of this post... | Read the comments on this post...... Read more »
Aalbers, S., Bernal, D., & Sepulveda, C. (2010) The functional role of the caudal fin in the feeding ecology of the common thresher shark Alopias vulpinus. Journal of Fish Biology, 76(7), 1863-1868. DOI: 10.1111/j.1095-8649.2010.02616.x
- May 13, 2010
- 03:14 PM
- 1,041 views
Cambrian survivors - weird critters which (temporarily) cheated extinction
Components of the newly-described Fezouata fauna. a, Demosponge Pirania auraeum b, Choiid demosponge c, Annelid worm d, Organism showing possible similarities to halkieriids e, Possible armoured lobopod f, Thelxiope-like arthropod g, Marrellomorph arthropod, probably belonging to the genus Furca h, Skaniid arthropod i, Spinose arthropod appendage
apparatus consisting of six overlapping elements. From Van Roy et al, 2010.
When the Cambrian period comes up in conversation, it is usually in reference to the evolutionary "explosion" which occurred around 530 million years ago. Animal fossils from before that time are typically small or are only traces, but in the latter half of the period (spanning ~488 to 542 million years ago) there is a dramatic increase in the diversity and disparity of organisms. The "small shelly fauna" of earlier times is replaced by a riot of organisms interacting with each other in complex ecosystems - it is one of the most dramatic changes seen in the entire fossil record. What is often forgotten, however, is that many of these weird critters disappeared by the end of the Cambrian in an extinction which appears to have swept away much of what had so recently (from a geological perspective) evolved.
That seemed like the best explanation, anyway, but there was one problem. We know of the existence of many strange Cambrian creatures because they have been recovered from sites of exceptional preservation which fossilized them with soft parts intact. Such sites are virtually unknown from the time right after the Cambrian, during the early days of the Ordovician period (~488-432 million years ago), making it difficult to know precisely when some of the extinct lineages disappeared. Now, as luck would have it, such an Ordovician site has been found in Morocco, and among the exceptionally-preserved fossils within it are creatures thought to have vanished millions of years before. Read the rest of this post... | Read the comments on this post...... Read more »
Van Roy, P., Orr, P., Botting, J., Muir, L., Vinther, J., Lefebvre, B., Hariri, K., & Briggs, D. (2010) Ordovician faunas of Burgess Shale type. Nature, 465(7295), 215-218. DOI: 10.1038/nature09038
- May 12, 2010
- 03:12 PM
- 1,457 views
What is it? - 37 million year old fossil primate puzzles paleontologists
In the Fayum desert of northern Egypt, not too far from the banks of the Nile, the vestiges of ancient forests are preserved in the sand-covered strata. The fossils are ghosts of a vanished oasis in which prehistoric cousins of modern elephants wallowed in lush wetlands and a host of ancient primates scrambled through the trees, and despite being known as one of the world's best fossil sites for over a century paleontologists are continuing to discovery new species from the desert rock. The trouble is that not all these new species are easily classified.
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Seiffert, E., Simons, E., Boyer, D., Perry, J., Ryan, T., & Sallam, H. (2010) A fossil primate of uncertain affinities from the earliest late Eocene of Egypt. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.1001393107
- May 11, 2010
- 03:57 PM
- 914 views
Off the prehistoric coast of Panama, a mega-toothed shark nursery
The jaws of C. megalodon as restored by Bashford Dean for the AMNH in 1909. Image from the American Museum Journal.
My early elementary reading school choices often got me into trouble. Every week I would pass over the recommended, grade-appropriate sections for the few shelves containing the books about dinosaurs, sharks, and alligators - if it was big and hard sharp teeth, I wanted to learn about it. The school librarian was not too pleased with this, even calling my parents in on one occasion to insist that I read something fit for younger children, but I just could not get enough of theropods, crocodylians, and enormous sharks.
Given my love for "cold-blooded killers" (as so many titles described them) it was not very long before I learned about "Megalodon" (formally known as Carcharocles megalodon), an immense shark which disappeared just a million-and-a-half years before human bathers began to wade into the shallows. Perhaps, some books hinted, the giant sharks still lurked in some unknown ocean recess, and a photograph of an array of American Museum of Natural History scientists inside the restored jaws of the shark drove home the point that it could have made of meal of just about anything it wanted. It was one of the most fascinating and terrifying images I had ever seen.
But the AMNH jaws were a bit out of proportion. As directed by Bashford Dean, the famous jaws were reconstructed by assuming that the teeth of the extinct shark would have had the same proportions to the jaw as in the living great white shark (Carcharodon carcharias), yielding a maw that would have fit a shark 100 feet long or more. As scientists learned more about the giant fish, though, they realized that this method had overinflated the size of the shark, with present estimates placing it at the more modest (but still gargantuan) 60 feet +. Despite the large size of C. megalodon, however, the young of this shark would still have been vulnerable to other seagoing predators of their time, and according to a new study published in PLoS One the "mega-toothed shark" may have protected its young by delivering them in nurseries. Read the rest of this post... | Read the comments on this post...... Read more »
Pimiento, C., Ehret, D., MacFadden, B., & Hubbell, G. (2010) Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama. PLoS ONE, 5(5). DOI: 10.1371/journal.pone.0010552
- May 10, 2010
- 07:57 PM
- 1,204 views
'Megatheria' muzzles provide clues to giant ground sloth diets
The skeleton of Megatherium, as figured in William Buckland's Geology and Mineralogy Considered With Reference to Natural Theology.
There is something fantastically weird about giant ground sloths. Creatures from a not-too-distant past, close enough in time that their hair and hide is sometimes found in circumstances of exceptional preservation, these creatures have no living equivalent. Their arboreal cousins still live in the tropics of the western hemisphere, but they can hardly be considered proxies for the ground sloths of the Pleistocene.
The most famous of these ancient beasts was Megatherium, an exceptionally large ground sloth which has been fascinating paleontologists and the public for over 200 years, but what is less well known by members of the public is that there were many kinds of ground sloth. Megatherium was not a lone aberration but a part of a highly successful family, one of the few types of weird South American mammal that flourished in North America when the two continents came into contact a few million years ago. Not all of them were the same. While some made their living grazing in open habitats others preferred to browse among most forested environs, and a recent study published in the Journal of Morphology provides a way to tell which kind of lifestyle particular sloths might have had. Read the rest of this post... | Read the comments on this post...... Read more »
Bargo, M., Toledo, N., & Vizcaíno, S. (2006) Muzzle of South American Pleistocene ground sloths (Xenarthra, Tardigrada). Journal of Morphology, 267(2), 248-263. DOI: 10.1002/jmor.10399
- May 6, 2010
- 03:41 PM
- 1,102 views
A moment frozen in time - fossil fish trace solves paleontological puzzle
One of the fossil fish I found in the Green River Formation of Wyoming.
I had my doubts about whether we were going to reach the quarry. The Toyota Yaris my wife and I had rented for our excursion through Utah and Wyoming was not designed to handle the rough dirt roads which wound their way through the grassy hills of the Equality State, but eventually the outcrop of grey-and-yellow rocks came into view. It was part of the famous Green River Formation, an approximately 42-53 million year old slice of earth's history known to be rich in fish fossils.
It did not take long to start finding what we were after. Almost immediately after we started splitting the shale left over in the quarry's spoil pile we began to find the rust-colored skeletons of small fish which had long ago settled to the bottom of an Eocene lake (though, to be honest, that afternoon's activities yielded far more fossil fish feces than fish). These quarries are so chock-full of these fossils, in fact, that fish quarried from them can be found at just about every gas station store in the area, yet despite the familiarity people have with this formation it still holds many secrets. In 2008, for example, scientists announced the discovery of a new fossil bat Onychonycteris finneyi from the Green River Formation, and a paper published this week in the journal PLoS One reports on another exceptional find from this formation. Read the rest of this post... | Read the comments on this post...... Read more »
Martin, A., Vazquez-Prokopec, G., & Page, M. (2010) First Known Feeding Trace of the Eocene Bottom-Dwelling Fish Notogoneus osculus and Its Paleontological Significance. PLoS ONE, 5(5). DOI: 10.1371/journal.pone.0010420
- May 5, 2010
- 08:22 PM
- 1,024 views
Eavesdropping lions zero-in on African wild dog calls
African wild dogs (Lycaon pictus), photographed at the Bronx Zoo.
African wild dogs (Lycaon pictus) don't have it easy. Their taste for large mammalian prey puts them in competition with lions and spotted hyenas for both prey and living space, meaning that wild dogs regularly have their kills stolen or are even killed by other predators. In fact, the dogs may even be unintentionally attracting the attention of these other hunters.
Like other social carnivores, African wild dogs communicate with each other through body language and olfactory cues, but they also employ a variety of high-pitched vocalizations. Despite their social benefits, however, the chirps and twitterings of these canids also come with costs. Eavesdroppers can use the information gained through what they overhear to their own advantage, and this can be especially dangerous in the case of lions. They kill wild dogs if they can catch them, and by vocalizing wild dogs run the risk of calling attention to their dens, their kills, or even themselves.
That lions do hone in on African wild dog calls is supported by a recent paper by scientists Hugh Webster, John McNutt, and Karen McComb published in the journal Ethology. Over the course of several years the team ran a series of playback experiments in Botswana's Okavango Delta in which African wild dog calls ("twitters") were played in the vicinity of lions and spotted hyenas (as well as bird calls similar to the wild dog vocalizations as a control and spotted hyena whoops to see if there was a difference in reactions). In all the researchers observed the reactions of 51 lions from a minimum of six prides and 11 spotted hyenas from three clans, with one month between each experiment. Read the rest of this post... | Read the comments on this post...... Read more »
Webster, H., McNutt, J., & McComb, K. (2010) Eavesdropping and Risk Assessment Between Lions, Spotted Hyenas and African Wild Dogs. Ethology, 116(3), 233-239. DOI: 10.1111/j.1439-0310.2009.01729.x
- May 4, 2010
- 12:35 PM
- 1,121 views
Where are all the males? - ancient DNA raises questions about extinct moa populations
The skeletons of female (larger, background) and male (smaller, foreground) Dinornis robustus, with a pigeon skeleton for comparison. From Allentoft et al 2010.
A little more than 700 years ago, multiple species of the gigantic, flightless birds called moas were still running around New Zealand. They ranged over almost the entirety of the North and South Islands, from the coast to the mountain forests, but when the Maori people arrived in the late 13th century the birds were quickly driven to extinction. Within a few hundred years they were entirely wiped out (along with the immense Haast's eagle, which fed on the moas), but fortunately for scientists these birds left behind vast accumulations of bones.
Two such moa graveyards are the Pyramid Valley and Bell Hill Vineyard sites on South Island. Together they record the presence of four moa species (Dinornis robustus, Emeus crassus, Euryapteryx curtus, Pachyornis elephantopus) over the course of the 3,000 years prior to the arrival of the Maori, and these sites presented scientists with the opportunity to recover ancient DNA from a large sample of bones to investigate the population genetics of the birds, including the sex of each individual. As they collected and analyzed the genetic data, however, they found something they were not expecting. In each species and across both deposits, females, which are considerably larger and heavier than males, were significantly more common, with an average of five females for every one male out of a sample of 227. What could could account for this disparity? Read the rest of this post... | Read the comments on this post...... Read more »
Allentoft, M., Bunce, M., Scofield, R., Hale, M., & Holdaway, R. (2010) Highly skewed sex ratios and biased fossil deposition of moa: ancient DNA provides new insight on New Zealand's extinct megafauna. Quaternary Science Reviews, 29(5-6), 753-762. DOI: 10.1016/j.quascirev.2009.11.022
- May 3, 2010
- 03:31 PM
- 995 views
The horse-hunting hyenas of Srbsko Chlum-Komin Cave
Breaking down a hyena kill. Given competition with other carnivores, prehistoric hyenas (like their living counterparts) would probably have disarticulated and transported parts of horses they killed. From Diedrich 2010.
In Hollywood films, there is nothing like an assemblage of bones strewn about a cave floor to testify to the power and voraciousness of a predator. Every skeleton is a testament to the hunting prowess of the carnivore, which causes even more alarm when the person who has stumbled into the cave realizes that they have just walked into a literal dead-end.
Although amplified for dramatic effect in the movies, this cinematic convention is based upon fact. Some mammalian carnivores do create bone assemblages in caves, and through the fossil record we know that they have been doing so for millions of years. In fact, the bone-collecting habits of carnivores have proven to be a boon for paleontologists, creating assemblages which not only represent the animals which lived in the area, but also provide clues as to the interactions between predator and prey during the distant past.
One such monument is Srbsko Chlum-Komin Cave in the Czech Republic. Discovered in 1942, this Upper Pleistocene site was once a spotted hyena den, and the activities of these predators caused many of the over 3,500 large mammal bones to become preserved at the site. Over 350 elements from hyena skeletons, bone-filled coprolites (fossil feces), and tooth-marked bones identify the cave as a place where the prehistoric hyenas took parts of their prey in order to consume them in relative peace, but, as explained by paleontologist Cajus Diedrich in Quaternary International, this assemblage is not quite like the other fossil hyena dens found elsewhere in Europe. Read the rest of this post... | Read the comments on this post...... Read more »
Diedrich, C. (2010) Specialized horse killers in Europe: Foetal horse remains in the Late Pleistocene Srbsko Chlum-Komín Cave hyena den in the Bohemian Karst (Czech Republic) and actualistic comparisons to modern African spotted hyenas as zebra hunters. Quaternary International. DOI: 10.1016/j.quaint.2010.01.023
- April 29, 2010
- 04:18 PM
- 1,268 views
Newly-discovered bones answer questions about fossil primate locomotion
Utah may seem like an odd place to search for primates, but you can find them if you know where to look. Although scrubby and arid today, between 46-42 million years ago what is now the northeastern part of the state was a lush forest which was home to a variety of peculiar fossil primates. Called omomyids, these relatives of living tarsiers are primarily known from teeth and associated bits and pieces of bone, but newly discovered postcranial remains may provide paleontologists with a better idea of how some of these ancient primates moved. Read the rest of this post... | Read the comments on this post...... Read more »
Dunn, R. (2010) Additional postcranial remains of omomyid primates from the Uinta Formation, Utah and implications for the locomotor behavior of large-bodied omomyids. Journal of Human Evolution. DOI: 10.1016/j.jhevol.2010.02.010
- April 23, 2010
- 11:40 AM
- 1,096 views
The strange sex lives of bone-eating whaleworms
For at least 30 million years, bone-eating worms have been making their homes in the bodies of decomposing whales on the seabottom, but the rotting cetacean carcasses are not just food sources for the polychaetes.
The term "worm" immediately conjures up images of the red, squiggly things which crawl all over the sidewalk after it rains, but this imagery does not fit the boneworms of the genus Osedax. These worms start off life as sexless larvae, and the timing of their arrival at a whale corpse makes all the difference as to whether they will be male or female. If the larva lands on the bones of a whale first, it will grow into a large female which will digest the bone with the help of endosymbiotic bacteria which comes to live inside the worm. Once this starts to happen, the larvae which fall on the already-established females will have a different life history. They will become males and will remain tiny (0.2-1.0mm long) for the rest of their lives, accumulating in crowded harems inside the tube of the larger female and living off stored yolk from their younger days as they have no mouth or digestive tract to speak of. Read the rest of this post... | Read the comments on this post...... Read more »
VRIJENHOEK, R., JOHNSON, S., & ROUSE, G. (2008) Bone-eating females and their ‘harems’ of dwarf males are recruited from a common larval pool . Molecular Ecology, 17(20), 4535-4544. DOI: 10.1111/j.1365-294X.2008.03937.x
- April 22, 2010
- 11:28 AM
- 1,179 views
How sucker-winged bats hang on
A Madagascar sucker-footed bat (Myzopoda aurita).
In the tropical forests of Madagascar, there lives a very peculiar kind of bat. While most bats roost by hanging upside-down from cave ceilings or tree branches, the Madagascar sucker-footed bat (Myzopoda aurita) holds itself head-up thanks to a set of adhesive pads on its wings. Nor is it the only bat to do so. Thousands of miles away in the jungles of Central and South America, Spix's disk-winged bat (Thyroptera tricolor) does the same thing, but how do their sucker pads work, and why do they choose to roost in a different way from all other bats?
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RISKIN, D., & RACEY, P. (2010) How do sucker-footed bats hold on, and why do they roost head-up?. Biological Journal of the Linnean Society, 99(2), 233-240. DOI: 10.1111/j.1095-8312.2009.01362.x
- April 20, 2010
- 07:16 PM
- 1,229 views
Nine million years ago, elephants invaded South America
For much of the past 130 million years South America was an island continent, and on it organisms evolved in "splendid isolation." Mammals, especially, evolved into forms not seen anywhere else, and while some mammalian immigrants made their way to South America during the past 30 million years it was not about three million years ago, with the closing of the isthmus of Panama, that large animals from North and South America began to wander across the new landbridge and mix with the endemic faunas. This is why there were elephants in South America and giant ground sloths in North America, but a new study just published in the Journal of the South America Earth Sciences suggests that the timing of this "Great American Interchange" was a little different.
As stated by scientists Kenneth Campbell, Donald Prothero, Lidia Romero-Pittman, and Nadia Rivera, in order to properly understand earth history you need to know when events occurred, but for years the ages of recent geological deposits in the Amazon Basin have remained contentious. If paleontologists are going to understand when the earliest North American mammals arrived in South America, the ages of the deposits in Amazonia have to be ascertained. To this end they investigated the magnetostratigraphy of a site along the Madre de Dios River in Peru, a site of particular importance given a controversial fossil found there. Read the rest of this post... | Read the comments on this post...... Read more »
Campbell Jr., K., Prothero, D., Romero-Pittman, L., Hertel, F., & Rivera, N. (2010) Amazonian magnetostratigraphy: Dating the first pulse of the Great American Faunal Interchange. Journal of South American Earth Sciences, 29(3), 619-626. DOI: 10.1016/j.jsames.2009.11.007
- April 19, 2010
- 03:53 PM
- 1,070 views
How giant anteaters duke it out
Two giant anteaters fight it out. On the left, the individuals lash out at each other with their enormous claws, and on the right they posture at each other (with the dominant animal, with the upright and puffed-out tail, on the right). From Kruetz et al 2009.
In the northern state of Roraima in Brazil, small plantations of the black wattle tree (Acacia mangium) serve up plenty of food to carpenter ants and other insects, and the variety of six-legged pests has attracted numerous giant anteaters. The trouble is that these immense xenarthrans don't typically get along very well.
As described in a brief report by Kolja Kreutz, Frauke Fischer, and K. Eduard Linsenmair in the journal Edentata, on December 5, 2005 Kreutz was observing a foraging anteater when the animal stopped in its tracks for a moment before bolting away. This was very unusual. When they perceive a threat, giant anteaters typically scent the air first before shuffling off, but this one just started running. Read the rest of this post... | Read the comments on this post...... Read more »
Kreutz, K., Fischer, F., & Linsenmair, K. (2009) Observations of lntraspecific Aggression in Giant Anteaters ( ) . Edentata, 6-7. DOI: 10.1896/020.010.0107
- April 15, 2010
- 01:44 PM
- 1,161 views
Fossil Shell Preserves Signs of a Prehistoric Tug-of-War
Top of the encrusted surface of a brachiopod shell, showing the "war" between an edrioasteroid (star-shaped organism at center) and a fast-growing bryozoan colony. From Sprinkle and Rodgers 2010.
Back in the early days of paleontology, when the meaning and origin of fossils was still in doubt, some naturalists believed that the shells, shark teeth, and other petrified curiosities were attempts by the rock to imitate life. Fossils were not true vestiges of history, it was believed, but instead the product of some "plastic virtue" suffused throughout the non-living Creation. As naturalists began to study fossils more closely, however, they realized that the ancient shells showed signs of growth just like their counterparts along the seashore. Fossils were not crude imitations of life. Instead they were the traces of long-deceased organisms which had been transformed, and while it is easy to take this fact for granted today there are quite a few stunning specimens which beautifully reaffirm that paleontology is the study of ancient life.
As explained by paleontologists James Sprinkle and Jeri Rodgers in the Journal of Paleontology, between about 300-315 million years ago what is now Brown County in north-central Texas was covered by a shallow bay or tidal channel. Bivalve shells, bits of trilobite, shark teeth, crinoids, and other such fossils have been found here, including a large number of brachiopods. Though they might superficially look like just another kind of mollusc, brachiopods belonged to an entirely different phylum, one that flourished during the past but has been reduced to just a handful of species today. You can tell them apart from mollusc shells because brachiopods had upper and lower shells which were hinged at the back (giving some the appearance of an oil-lamp, hence their common name "lamp shells"). Given the abundance of these fossils it is easy to simply collect them and store them away, but a closer look at one specimen in particular documented a years-long struggle between two organisms. Read the rest of this post... | Read the comments on this post...... Read more »
Sprinkle, J., & Rodgers, J. (2010) Competition between a Pennsylvanian (Late Carboniferous) Edrioasteroid and a Bryozoan for Living Space on a Brachiopod. Journal of Paleontology, 84(2), 356-359. DOI: 10.1666/09-089R.1
- April 13, 2010
- 08:40 PM
- 1,045 views
Life in the trees, not bamboo, shaped the panda's "thumb"
A red panda (Ailurus fulgens, left, photographed at the Bronx Zoo) and a giant panda (Ailuropoda melanoleuca, right, photographed at the National Zoo).
As the paleontologist Stephen Jay Gould so astutely pointed out in one of his most famous essays, the thumbs of giant pandas (Ailuropoda melanoleuca) are nothing at all like the large digits on our own hands. Their accessory "thumbs", visible on the surface as a differentiated part of the pad on the "palm" of the hand, are modified sesamoid bones derived from the wrist. They are jury-rigged bits of anatomy which cast nature as an "excellent tinkerer, not a divine artificer."
Surprisingly, however, these highly-modified wrist bones are not unique to the black-and-white bears. Red pandas (Ailurus fulgens), which are much more closely related to raccoons than bears, also have modified sesamoid "thumbs" which they use to manipulate bamboo. Hence, given the similar wrist anatomy and diet of these two carnivorans, it might be assumed that the false thumbs are adaptations related to bamboo-eating, but a recent analysis of a fossil relative of red pandas suggests that the peculiar structures evolved for an entirely different reason. Read the rest of this post... | Read the comments on this post...... Read more »
Salesa, M. (2006) Evidence of a false thumb in a fossil carnivore clarifies the evolution of pandas. Proceedings of the National Academy of Sciences, 103(2), 379-382. DOI: 10.1073/pnas.0504899102
- April 12, 2010
- 04:35 PM
- 1,115 views
Fossil dog may be ancestor of Africa's "painted" canids
An African wild dog (Lycaon pictus, left) compared to a spotted hyena (Crocuta crocuta, right). Both photographed at the Bronx Zoo.
It never fails. Whenever I visit a zoo's African wild dog exhibit someone inevitably asks "Are those hyenas?", and when I visit spotted hyena enclosures I often hear the question "Are those dogs?" These carnivores, known to scientists as Lycaon pictus and Crocuta crocuta (respectively), are only distant cousins, but the vague similarities shared between them often cause people to confuse one with the other.
There are a few quick and dirty ways to tell them apart. Spotted hyenas, as their name indicates, have a coat flecked with solid spots while the fur of each African wild dog carries a distinctive pattern of caramel, white, black, and dark brown. They are also shaped a little bit differently; hyenas are stockier, with relatively shorter midsections, while African wild dogs have a longer, more lanky appearance. And, if you are really an astute observer, you might notice that African wild dogs lack something your more familiar domestic dogs have; a fifth toe, or dewclaw, on the forelimb. It is thought that this loss might be an adaptation which allows African wild dogs to more efficiently run after prey over long distances, but when did this happen, and how do these canids relate to other dogs? Read the rest of this post... | Read the comments on this post...... Read more »
ADAM HARTSTONE-ROSE, LARS WERDELIN, DARRYL J. DE RUITER, LEE R. BERGER and STEVEN E. CHURCHILL. (2010) THE PLIO-PLEISTOCENE ANCESTOR OF WILD DOGS, LYCAON SEKOWEI N. SP. Journal of Paleontology, 84(2), 299-308. info:/10.1666/09-124.1
- April 8, 2010
- 11:01 AM
- 1,522 views
Close to Homo? - The announcement of Australopithecus sediba
A diagram of how the skeletons of Australopithecus sediba came to be preserved in the Malapa cave deposit. From Dirks et al, 2010.
A little less than two million years ago, in what is now South Africa, a torrential downpour washed the bodies of two humans into the deep recesses of a cave. Just how their remains came to be in the cave in the first place is a mystery. Perhaps they fell in through the gaping hole in the cave roof just as hyenas, saber-toothed cats, horses, and other animals had, but, however the humans entered the cave, their bones ultimately came to rest in a natural bowl carved into the rock. This mode of preservation would keep their remains in good condition until their discovery in 2008, and today in the journal Science a team of researchers has described them as the latest addition to our family tree, Australopithecus sediba. Read the rest of this post... | Read the comments on this post...... Read more »
Lee R. Berger, Darryl J. de Ruiter, Steven E. Churchill, Peter Schmid, Kristian J. Carlson, Paul H. G. M. Dirks, Job M. Kibii1. (2010) Australopithecus sediba: A New Species of Homo-Like Australopith from South Africa. Science, 195-204. info:/10.1126/science.1184944
Paul H. G. M. Dirks, Job M. Kibii, Brian F. Kuhn, Christine Steininger,, Steven E. Churchill, Jan D. Kramers, Robyn Pickering, Daniel L. Farber,, & Anne-Sophie Mériaux, Andy I. R. Herries, Geoffrey C. P. King, Lee R. Berger. (2010) Geological Setting and Age of Australopithecus sediba from Southern Africa. Science, 205-208. info:/10.1126/science.1184950
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