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Laelaps
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- August 6, 2010
- 01:50 PM
- 8,112 views
Fossil Bonanza in Australian Cave Documents the Growth of a Prehistoric Marsupial
By now you have no doubt heard about the dinosaurian tempest-in-a-teacup I recently called #TriceraFAIL. To sum things up briefly - on the basis of skeletal anatomy and histology, paleontologists John Scannella and Jack Horner proposed that the horned dinosaur traditionally known as Torosaurus was actually the fully-mature growth stage of Triceratops. If further evidence [...]... Read more »
Black, K., Archer, M., Hand, S., & Godthelp, H. (2010) First comprehensive analysis of cranial ontogeny in a fossil marsupial—from a 15-million-year-old cave deposit in northern Australia. Journal of Vertebrate Paleontology, 30(4), 993-1011. DOI: 10.1080/02724634.2010.483567
- September 17, 2008
- 10:40 AM
- 2,077 views
What did Leonardo eat for lunch?
"Leonardo," the mummy dinosaur, courtesy of the HMNS.
Although it got a brief treatment in the book Horns and Beaks, many people have been waiting for more information on the exceptionally-preserved Brachylophosaurus skeleton named "Leonardo." Due to be unveiled next week at the Houston Museum of Natural Science (the date was pushed back due to Hurricane Ike; the museum and Leonardo were unharmed), the fossil provides a unique look at the soft tissues of this particular dinosaur.
Dinosaur "mummies" have been found before, dating back to the 19th century, but in many cases little more than skin impressions were preserved. Leonardo, by contrast, is so well preserved that paleontologists are getting a look at the internal anatomy of the dinosaur, and the new paper (out in Palaios) focuses on gut contents.
Within the body cavity of Leonardo there is a large amount of plant material. The question is, however, whether those plants represent gut contents or found their way into the specimen by some other route. If the body cavity was preserved intact (i.e. there were no gaping holes in it) then there could be little doubt that the plant material represents gut contents, but if the cavity was punctured other possibilities open up. The gut contents might have stayed in the body and been reworked, they could have been mixed with outside plant material, or the original contents could have been removed and then replaced. The actual soft tissue of the digestive tract would have decomposed fairly quickly after death and so the contents would not have been in their original position even if they were preserved, but the first task of the researchers was to determine whether they were dealing with gut contents or washed-in plants (or both).
A reconstruction of "Leonardo," courtesy of the HMNS.
The paleontologists were not looking at whole leaves, stems, or other plant parts, though. The preserved plant material was very fragmentary, best described as "fragile, black crumbs." These little bits were substantially different from the woody material found in some hardosaur coprolites (or fossil poo), meaning that (if the fragments were true gut contents) shortly before death Leonardo had a lunch of leaves. The fragments were consistent with what would be expected for partially-digested hadrosaur meals, of course, but it did not make identification of the plants especially easy. This became even more vexing when the researchers realized that the high amount of clay inside the body cavity most probably meant that the body cavity was breached. There was a possibility that some of this material came in from the outside.
[As is pointed out in the paper, many animals have clay or soil inside their digestive tract as a result of purposefully eating it or the material coming in with the food. In Leonardo's case, though, the sheer amount of clay showed that it was probably not intentionally swallowed. If the hadrosaur did so then it would have eaten more clay than plants!]
If there was a mix of gut contents and material from outside, however, it would be expected that there would be different characteristics between the partially digested food and the washed-in plants. Being that the material was generally uniform, the alternatives became narrowed down to either preserved gut contents or outside material. While both options were plausible, the retention of gut contents seems more likely.
A life illustration of Leonardo by Bob Bakker, courtesy of the HMNS.
Exceptional preservation is typically a result of rapid burial; the longer a carcass is left out to rot the more it will be picked apart or otherwise broken down before preservation. Given that Leonardo is perhaps the most exceptionally-preserved large dinosaur yet found, the skeleton was probably buried very quickly after death. This means that if the plant material in the body cavity came from the outside it would have had to find a way in after the body wall was breached, something that is unlikely. Indeed, the type of plant material inside the body was not found outside the body in the surrounding sediment; it is more probable that the crumbly plant fossils were actual gut contents.
About 75 million years ago, in what is now Montana, a subadult Brachylophosaurus died. While it was not killed or consumed by a predator, the exact cause of death is still a mystery. Either in death or shortly afterward the body of the dinosaur was quickly covered by sediment, perhaps by a flooded river. Piled beneath the mud and clay the dinosaur was beyond the reach of the large predators (except, perhaps, its tail, which may have been tugged on by some scavenger), and its body slowly started to decompose. The internal organs went first, with a breach in the body wall letting enough water and sediment in to wash the gut contents around inside the body cavity. This process preserved some aspects of the anatomy but obscured others, but tens of millions of years later the descendants of the tiny mammals that lived in the corners of the Mesozoic world would unearth Leonardo's remains. Paleontologists have only just begun to understand what the skeleton can teach us about dinosaurs, and I'm sure we will be talking about Leonardo for many years to come.
J. S. Tweet, K. Chin, D. R. Braman, N. L. Murphy (2008). Probable Gut Contents Within A Specimen Of Brachylophosaurus Canadensis (Dinosauria: Hadrosauridae) From the Upper Cretaceous Judith River Formation Of Montana PALAIOS, 23 (9), 624-635 DOI: 10.2110/palo.2007.p07-044r Read the comments on this post...... Read more »
J. S. Tweet, K. Chin, D. R. Braman, & N. L. Murphy. (2008) Probable Gut Contents Within A Specimen Of Brachylophosaurus Canadensis (Dinosauria: Hadrosauridae) From the Upper Cretaceous Judith River Formation Of Montana. PALAIOS, 23(9), 624-635. DOI: 10.2110/palo.2007.p07-044r
- April 20, 2009
- 12:02 PM
- 1,685 views
Can sexual selection account for giraffe necks?
A giraffe, photographed at the Bronx zoo.
Why do giraffes have long necks? We know that modern giraffes must have evolved gradually, but figuring out what selection pressures influenced giraffe evolution is another story altogether. One of the most popular recent explanations is that giraffes have long necks as a result of sexual selection.
The "necks for sex" hypothesis is primarily inspired by the contests between male giraffes. In these duels the males stand side by side and whack each other with their necks and ossicones ("horns"). This can be seen in the video below;
What does this behavior have to do with the evolution of long necks? According to the "necks for sex" hypothesis males with longer necks in an ancestral population of giraffes would have won more of these contests and thus been more successful at mating. It seems simple enough, but there is a problem: the selective pressure would just be on the males. Indeed, if this kind of competition between males was driving the selection for long necks we would expect to see more sexual dimorphism. Females, who don't engage in these contests, would probably have shorter necks than males. If little to no sexual dimorphism can be seen in living giraffes it is unlikely that sexual selection was the main cause for the evolution of the modern forms. To test this hypothesis G. Mitchell, S.J. van Sittert, and J.D. Skinner examined 17 male and 21 female giraffes that were killed during culling in Zimbabwe and reported their results in the Journal of Zoology.
What Mitchell and colleagues found was there were virtually no differences between males and females in terms of body size, neck length, and leg length that could be attributed to sexual selection. There was one interesting minor difference, though. The zoologists found that female giraffes had proportionally longer necks compared to foreleg length than males when the sexual selection hypothesis would predict that males would have longer necks. Both sexes also had necks that grew faster than the rest of their body, cutting down the idea that males "invested" more in their necks than females.
Simply put, the "necks for sex" hypothesis fails because there is no evidence of sexual dimorphism in giraffes that would result from male-male competition. The competitions between male giraffes are a consequence, rather than a cause, of neck elongation. Giraffe necks became elongated for some other reason.
The debate over giraffe necks illustrates the pitfalls of trying to figure out past evolutionary pressures based almost solely upon living animals (and just one living species, at that). Studies involving the benefits of having a long neck to feeding or intrasexual competition might be informative, but what giraffes do now might not tell us much about what caused their ancestors to evolve long necks. We should not confuse what an organ is used for now with what led to its origin: they are not always the same.
Strangely, a discussion of fossil evidence is almost always missing from hypotheses about the evolution of giraffe necks. Perhaps this is because we cannot observe the behavior or feeding patterns of extinct creatures, but studies of fossil giraffes could do much to inform discussions of giraffe evolution. In fact I recall seeing a fossil giraffe with a neck intermediate in length between ancestral and living forms in Don Prothero's Evolution: What the Fossils Say and Why it Matters. I do not know if a study of this animal has been formally published yet, but it could certainly be important to figuring out how giraffes evolved.
Mitchell, G., van Sittert, S., & Skinner, J. (2009). Sexual selection is not the origin of long necks in giraffes Journal of Zoology DOI: 10.1111/j.1469-7998.2009.00573.x Read the comments on this post...... Read more »
Mitchell, G., van Sittert, S., & Skinner, J. (2009) Sexual selection is not the origin of long necks in giraffes. Journal of Zoology. DOI: 10.1111/j.1469-7998.2009.00573.x
- April 22, 2009
- 10:11 PM
- 1,637 views
Puijila darwini: A Significant Seal
Of all the evolutionary transitions that have ever taken place few have received as much attention as the origin of whales. (See here, here, here, here,and here for a few of my posts on the subject.) The story of how terrestrial hoofed mammals gave rise to the exclusively aquatic leviathans has been highlighted in headlines over and over again, but other marine mammals have not received the same amount of public attention. In the case of pinnipeds (seals, sea lions, and walruses) this may be at least partially due to the fact that their origins have been difficult to tease out.
It has long been known that seals and sea lions are carnivoran mammals closely related to weasels or bears, but just how pinnipeds first became adapted to a semi-aquatic life has been more difficult to figure out. This is largely due to the fact that their fossil trail stopped rather abruptly. The 24-22 million year old Enaliarctos, the oldest pinniped well-represented by fossils, was already a sea-lion like creature that swam in the sea. Surely there had to be even older fossils connecting it to its progenitors, but for years the trail was cold.
The skull of Puijila from the underside (a) and left side (b). From the Nature paper.
The gap between Enaliarctos and its forebears did not represent a real void in nature. Instead it pointed to a gap in our knowledge. That gap has now been partially filled with the announcement in the journal Nature of Puijila darwini, an early Miocene seal that represents a more terrestrial stage of pinniped evolution.
Bear in mind, however, that Puijila was probably not ancestral to Enaliarctos or living pinnipeds. Given that evolution is a branching process it can be extremely difficult to tell whether you are dealing with, as T.H. Huxley put it, "fathers" and "sons" (linear types) or "uncles" and "nephews" (intercalary types). Puijila appears to be one of the latter, a side branch that preserved some of the tell-tale traits than can inform us about pinniped evolutionary transitions. Indeed, the significance of Puijila is that it is representative of a stage of pinniped evolution that scientists could only hypothesize about previously. It is the fossil confirmation of the idea that seals did evolved from fully terrestrial ancestors.
The restored skeleton of Puijila. From the Nature paper.
Puijila was found on Devon Island, a chilly island well inside the Arctic Circle in Nunavut, Canada. About 21 million years ago there was a freshwater lake there where rabbits, rhinoceros, antelope, and other creatures sometimes came to drink.Puijila also lived in and around the lake. It was about three feet long with a long tail and feet that, while webbed, could certainly not be called flippers. Indeed Puijila was very similar in many respects to the extant river otters of North America, yet it differed in some important ways. It had upper arms and shoulders, for instance, that were slightly more expanded and robust than the same bones in otters. These differences would have provided more area for muscle attachment, and this could mean that Puijila was propelling itself with its webbed front and hind feet (possibly with an emphasis on the front feet).
So how does Puijila relate to other mammals? Given that it lived just prior to Enaliarctos and a radiation of marine pinnipeds it is probably more of a "persistent type" of early pinniped than an actual ancestor of creatures like Enaliarctos. Still, the phylogenetic analysis grouped it with Enaliarctos and another pinniped called Potamotherium. From what is known of these genera and the locations in which they have been found the authors of the paper suggest that pinnipeds may have originated by about 33 million years ago somewhere in the Arctic.
If the authors of the paper are correct the transition of pinnipeds to an aquatic mode of life would have started with Puijila-like mammals that lived in freshwater. Eventually, though, these amphibious mammals would have extend their range to the sea shore where they would have been further adapted to life in the water into forms more like Enaliarctos. Whether this hypothesis is correct, however, will rest on further studies of the fossil evidence.
Puijila is also important to illustrating the contingent nature of evolution. Even though it is extremely otter-like it did not swim like an otter. It primarily used its limbs to swim and, it probably did not incorporate up-and-down motions of its spinal column like transitional whales (i.e. Rodhocetus) did, either. If Puijila really does represent an important transitional stage in pinniped evolution, then, they way it swam can tell us much about why pinnipeds swim by using their limbs while other marine mammals exhibit different types of locomotion. The past is the key to the present.
I truly hope that Puijila gets the public attention it deserves. It is a wonderful, nearly-complete transitional form that answers some of our evolutionary questions while raising new ones. I hope it will inspire vertebrate paleontologists to look into pinniped origins with renewed vigor, and perhaps in a few decades we can talk about transitional pinnipeds with as much excitement as that with which we discuss transitional cetaceans.
Links: The official Puijila website.
Not Exactly Rocket Science: Puijila, the walking seal.
Rybczynski, N., Dawson, M., & Tedford, R. (2009). A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia Nature, 458 (7241), 1021-1024 DOI: 10.1038/nature07985 Read the comments on this post...... Read more »
Rybczynski, N., Dawson, M., & Tedford, R. (2009) A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia. Nature, 458(7241), 1021-1024. DOI: 10.1038/nature07985
- May 22, 2009
- 10:31 AM
- 1,622 views
Getting to know "Ida"
The exceptionally preserved skeleton of Darwinius, known popularly as "Ida." From PLoS One.
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It has been three days now since an international team of paleontologists promised to deliver the change we need change everything, but when I woke up this morning I was pleased to find that things had still not gone "Bizarro World" around here. There is still a lot going on with Darwinius (better known as "Ida"), though, and while I am sure we will still be talking about her for some time to come I wanted to take a moment to step back and answer a few questions that keep cropping up about this spectacular fossil.
As I attempted to follow the frenzy over this fossil primate I noticed that many people did not understand how scientists knew Ida was a female and that she was not yet fully mature. How can you tell such a thing from a fossil? It is not like they come with a birth certificate. True enough, but there are tell-tale characteristics the paleontologists who studied Ida used to come to these conclusions.
Read the rest of this post... | Read the comments on this post...... Read more »
Franzen, J., Gingerich, P., Habersetzer, J., Hurum, J., von Koenigswald, W., & Smith, B. (2009) Complete Primate Skeleton from the Middle Eocene of Messel in Germany: Morphology and Paleobiology. PLoS ONE, 4(5). DOI: 10.1371/journal.pone.0005723
- March 27, 2008
- 06:03 PM
- 1,621 views
A new Paleocene marine crocodile, Guarinisuchus munizi
The skull and mandible of Guarinisuchus.
After the end-Cretaceous extinction, an "empty" world was left to fill up. The non-avian dinosaurs were gone, as were the mosasaurs, ammonites, pterosaurs, and other creatures. Indeed, in marine environments the large Mesozoic predators were eliminated in the extinction event, allowing sharks and crocodiles to evolve and diversify now that they were no longer any mosasaurs patrolling the waters. One such crocodylian that moved into open ecological space was Guarinisuchus munizi, just described in the Proceedings of the R... Read more »
José Barbosa, Alexander Wilhelm Kellner, & Maria Somália Viana. (2008) New dyrosaurid crocodylomorph and evidences for faunal turnover at the K–P transition in Brazil. Proceedings of the Royal Society B: Biological Sciences, -1(-1), -1--1. DOI: 10.1098/rspb.2008.0110
- July 14, 2008
- 12:03 PM
- 1,606 views
A new species of Velociraptor
The type skull of Velociraptor mongoliensis. From Osborn, et al. 1924.
By the summer of 1993 Velociraptor had become a household name. Although Deinonychus had long been my fleet-footed favorite the olive-green "clever girls" of Speilberg's film soon outshone all of their relatives and gave Tyrannosaurus a run for it's money.* Velocriaptor is hardly a new dinosaur, however. It was discovered during the famous expeditions to Mongolia made by the AMNH in the 1920's, the team setting out to find the "birthplace" of all mammals and coming back with loads of new di... Read more »
Pascal Godefroit, Philip Currie, Li Hong, Shang Yong, & Dong Zhi-Ming. (2008) A New Species Of Velociraptor (Dinosauria: Dromaeosauridae) From the Upper Cretaceous Of Northern China. Journal of Vertebrate Paleontology, 28(2), 432. DOI: 10.1671/0272-4634(2008)28[432:ANSOVD]2.0.CO;2
- January 28, 2008
- 11:03 PM
- 1,604 views
Eurasian Pleistocene Extinctions & Ecological "Overkill"
The skeleton of an Irish Elk (Megaloceros giganteus) at the AMNH.
Discussions of mass extinctions nearly always give rise to heated debates as to the mechanism(s) behind the disappearance of so many taxa in a short amount of time, and one of the most active debates still surrounds the extinction of Pleistocene megafauna. All over the world the extinction of large animals appears to be correlated with the movements of our own species, Homo sapiens, into new territories. Disease and climate change have their own parts to play, the "Overkill Hypothesis" is perhaps... Read more »
D PUSHKINA. (2008) Human influence on distribution and extinctions of the late Pleistocene Eurasian megafauna. Journal of Human Evolution. DOI: 10.1016/j.jhevol.2007.09.024
- March 17, 2008
- 04:09 PM
- 1,600 views
Megalosaurus, we hardly knew ye
The lower jaw of Megalosaurus, presently the only fossil that can accurately be attributed to this enigmatic genus.
Although it was one of the first dinosaurs to be scientifically described during the early 19th century, the theropod Megalosaurus remains one of the most enigmatic (and problematic) large dinosaurs known. Even though an entire family, the Megalosauridae (established by Huxley in 1869), bears the name of this famous dinosaur, the group has come to be seen as a taxonomic wastebasket with no real meaning. Indeed, a new paper in the journal Palaeonto... Read more »
ROGER BENSON, PAUL M BARRETT, H PHILIP POWELL, & DAVID B NORMAN. (2008) THE TAXONOMIC STATUS OF MEGALOSAURUS BUCKLANDII (DINOSAURIA, THEROPODA) FROM THE MIDDLE JURASSIC OF OXFORDSHIRE, UK. Palaeontology, 51(2), 419-424. DOI: 10.1111/j.1475-4983.2008.00751.x
- March 1, 2010
- 11:42 AM
- 1,589 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
- June 8, 2009
- 01:21 PM
- 1,573 views
Why intelligent design fails
Is intelligent design science, or not? Think carefully before you answer. The modern intelligent design (ID) movement is motivated by theological concerns and trades in on religious authority to meet its aims, but stripped of this background, can ID be relegated to the "junk science" bin? While the answer to this latter question is "Yes", in a new paper ("The science question in intelligent design") Sahotra Sarkar argues that proclaiming ID to be non-science without careful consideration does little good. Read the rest of this post... | Read the comments on this post...... Read more »
Sarkar, S. (2009) The science question in intelligent design. Synthese. DOI: 10.1007/s11229-009-9540-x
- June 3, 2009
- 08:43 AM
- 1,572 views
Meet Anoiapithecus, the flat-faced ape
The face of Anoiapithecus. From Moya-Sola et al. (2009).
One of the most controversial aspects of the whole Darwinius kerfuffle has been the primate's proposed status as "the ancestor of us all." The fossil, named "Ida", has been popularly touted as the "missing link" connecting us to all other mammals, but how can we really know if Darwinius fits this role? The truth is that we can't, and it is nearly impossible to parse direct ancestor-descendant relationships among fossil vertebrates, especially when we're talking about a fossil that lived over 40 million years before the first hominins evolved.
Indeed, the frenzy over Ida has just been made all the more unfortunate by the announcement of a fossil primate in the journal PNAS that is much, much more closely related to us. Called Anoipithecus brevirostris, this short-faced ape was recently discovered in 11.9 million-year-old (Middle Miocene) strata in Spain. It doesn't have a book, a flashy website, or a prime-time TV slot, but it could have some very interesting implications for the origins of our ape ancestors. Read the rest of this post... | Read the comments on this post...... Read more »
Moya-Sola, S., Alba, D., Almecija, S., Casanovas-Vilar, I., Kohler, M., De Esteban-Trivigno, S., Robles, J., Galindo, J., & Fortuny, J. (2009) A unique Middle Miocene European hominoid and the origins of the great ape and human clade. Proceedings of the National Academy of Sciences. DOI: 10.1073/pnas.0811730106
- April 30, 2008
- 10:06 AM
- 1,566 views
Robust australopithecines and masticatory overkill
The skull of Paranthropus boisei (AKA "Zinj," "Dear Boy," "Nutcracker Man," etc.). From Ungar et al. 2008.
Ever since the discovery of the hominds we call Paranthropus robustus in 1938 and Paranthropus boisei in 1959, the dietary habits of these "robust australopithecines" have been controversial. With skulls that seem to have more in common with gorillas than with Homo habilis, another hominid more closely related to us that lived during the same time, it has long been thought that Paranthropus was a dietary specialist. The saggital crest, large and thickly-en... Read more »
Peter Ungar, Frederick E Grine, Mark F Teaford, & Michael Petraglia. (2008) Dental Microwear and Diet of the Plio-Pleistocene Hominin Paranthropus boisei. PLoS ONE, 3(4). DOI: 10.1371/journal.pone.0002044
- June 11, 2008
- 12:02 PM
- 1,564 views
Wandering Megaraptor
When I wrote about the new sauropod Futalognkosaurus dukei last October, I noted that the authors of the paper describing the animal also included a brief summary of the other animals found nearby. Remains of crocodiles, fish, and pterosaurs provided some clues as to the paleoecology of the area about 90 million years ago, but one of the big surprises was a big honkin' claw from Megaraptor. At first the remains of Megaraptor were thought to represent a coelurosaur, but the complete hand has shown that it is probably either a spinosaurid or carcharodontosaurid. A recent study of the... Read more »
Nathan Smith, Peter J Makovicky, Federico L Agnolin, Martín D Ezcurra, Diego F Pais, & Steven W Salisbury. (2008) A Megaraptor-like theropod (Dinosauria: Tetanurae) in Australia: support for faunal exchange across eastern and western Gondwana in the Mid-Cretaceous. Proceedings of the Royal Society B: Biological Sciences, -1(-1), -1--1. DOI: 10.1098/rspb.2008.0504
- April 10, 2009
- 10:38 AM
- 1,554 views
Another cool Cambrian critter
An artist's restoration of Hurdia. From the Science paper.
It is not easy working on Cambrian fossils. The petrified treasures are found in only a few places in the world, and even though many exhibit exquisite preservation they come from a time when life on earth would have looked very unfamiliar. One such creature, Anomalocaris, was a three foot long invertebrate that swam by undulating a series of lobes on either side of its body. In front of its mouth were two spiked tendrils that may have helped situate prey items to be processed by its conveyor belt of crushing plates that was its mouth. There is nothing quite like it alive today.
Indeed, Anomalocaris was so unusual that it was misidentified multiple times. Parts of it were taken as representing jellyfish, crustaceans, or other strange Cambrian creatures. Now we known differently, but similar problems still affect other Cambrian fossils. In the book Wonderful Life the late paleontologist Stephen Jay Gould wrote that "Three genera (Hurdia, Tuzoia, and Carnarvonia) are bivalved arthropod carapaces with no soft parts preserved; they cannot be properly allocated to any arthropod subgroup, and remain unclassified today." Twenty years later Tuzoia remains a mystery and I can only imagine that the name of Carnarvonia has changed as that genus name is also used for a flowering plant, but in the journal Science a team a researchers has just revealed a new identity for Hurdia.
Admittedly I am a little late to the game on this one (see what others have had to say at Ediacaran, The Dragon's Tales, and Deep Sea News), but it is hard to resist talking about such a strange creature. It has a story as complex as, and entwined with, that of Anomalocaris.
As Allison Daley and colleagues note, Hurdia has had a complex history. Parts of it were identified as belonging to jellyfish and various hard-shelled invertebrates, but during the major revisions that occurred during the 1980's these parts were assigned to two particular genera: Anomalocaris and Laggania. This placed the pieces of Hurdia in the right ballpark, but it was not until the 1990's that Desmond Collins saw that Hurdia deserved its own genus designation. A reinvestigation of the material relating to all three genera has supported this conclusion and given us an image of a creature even stranger than Anomalocaris.
Generally speaking Hurdia looked a lot like Anomalocaris. Being close relatives they shared a common body plan with anterior tendrils, stalked eyes, and a trash-compactor-of-doom type mouth. A major feature that made Hurdia distinct, though, was a large head shield that stuck out in front of its eyes. These shields were a little over three inches long, making up for about half the body length of the entire animal.
The systematic placement of Hurdia. From the Science paper.
Hurdia has also provided increased insight into the place of creatures like Anomalocaris among invertebrates. Together Hurdia, Anomalocaris, and Laggania belong to a group called Radiodonta, and this group is placed close to the Euarthropoda, or "true" arthropods like trilobites. This makes the members of the Radiodonta very significant to questions of arthropod origins, and the recent discovery of another Anomalocaris-relative called Schinderhannes has provided researchers with even more material to investigate. These creatures were strange enough to start with, but with each new discovery they seem get a little bit stranger.
Daley, A., Budd, G., Caron, J., Edgecombe, G., & Collins, D. (2009). The Burgess Shale Anomalocaridid Hurdia and Its Significance for Early Euarthropod Evolution Science, 323 (5921), 1597-1600 DOI: 10.1126/science.1169514 Read the comments on this post...... Read more »
Daley, A., Budd, G., Caron, J., Edgecombe, G., & Collins, D. (2009) The Burgess Shale Anomalocaridid Hurdia and Its Significance for Early Euarthropod Evolution. Science, 323(5921), 1597-1600. DOI: 10.1126/science.1169514
- October 31, 2008
- 09:29 AM
- 1,544 views
There's more than one way to catch an elephant shrew
This past February I wrote about a new giant sengi (or elephant shrew) described in the Journal of Zoology. When attempts to capture live animals failed, researchers used camera traps to get a better look at these previously undescribed creatures. A new paper in the Journal of Mammalogy has announced the discovery of another (although smaller) species of elephant shrew, but it wasn't so easy to spot.
The new species of sengi (bottom, EPI), compared with Elephantulus edwardii (EED), and E. rupestris (ERU). From Smit et al., 2008.
In the Western and Northern Cape Provinces of South Africa, there lives a small elephant shrew named Elephantulus edwardii. Previously there appeared to be the only endemic species, but the new study reports that there are in fact two species of sengi endemic to this region of South Africa. The new species has been named Elephantulus pilicaudus. The differences between it and its close relative, E. edwardii, however, are subtle.
"Species" as a popular term does not often match the scientific understanding of the concept. To the public, a species should be able to be visually distinguished from other animals, and what a non-scientist may recognize as different "species" may, in fact, be entirely different genera. To a scientist, however, the issue is much more complex, and a variety of information is required to determine whether animals that look very similar are truly distinct species or exhibit variation within one species.
Wild-captured and stuffed specimens of E. pilicaudus did show some morphological differences from the other species of sengi that live in its range (and its close relative, E. edwardii), but this alone was not enough to determine that it was a distinct species. Genetic information was also required, and researchers compared the DNA of the cytochrome-b gene from several sengi species to confirm that the new species was distinct.
It is not know how large or small the population of E. pilicaudus is. It appears to be rare, and its visual similarity to E. edwardii does not make identification easy. (A tell-tale sign of E. pilicaudus appears to be a larger tuft at the end of the tail.) The authors of the new paper report that it probably has a more restricted range than the other sengis that live in the same area, but it is unknown how prevalent it is within that range.
The announcement of a new species has something of a romantic mythology associated with it. With so much of the world explored, it would seem that the few remaining unknown species are only to be found in steaming jungles criss-crossed by lianas or in the darkest ocean trenches. Yet the truth is even more fantastic than such adventurous imagery. There are plenty of previously undescribed species virtually right under our noses, and it takes only a bit of careful attention to sniff them out.
H. A. Smit, T. J. Robinson, J. Watson, B. Jansen van Vuuren (2008). A New Species of Elephant-shrew (Afrotheria: Macroscelidea: Elephantulus) from South Africa Journal of Mammalogy, 89 (5) DOI: 10.1644/07-MAMM-A-254.1 Read the comments on this post...... Read more »
H. A. Smit, T. J. Robinson, J. Watson, & B. Jansen van Vuuren. (2008) A New Species of Elephant-shrew (Afrotheria: Macroscelidea: Elephantulus) from South Africa. Journal of Mammalogy, 89(5), 1257. DOI: 10.1644/07-MAMM-A-254.1
- April 22, 2008
- 11:06 AM
- 1,542 views
Amphibious Elephant Ancestors
Although not as aquatically-adapted as their distant ancestors, Indian elephants are certainly capable swimmers.
A number of my fellow ScienceBloggers have covered the "Aquatic Elephant Hypothesis" lately (see here, here, and here), and even though I'm a little late to the party I thought that I'd throw in my two cents about the significance of ancient, waterlogged pachyderms.
The idea that the ancestors of elephants (including the two living genera Loxodonta and Elephas) were aquatic at some point in the past has been circulating for a number of years now, especially ... Read more »
A Liu, E R Seiffert, & E L Simons. (2008) Stable isotope evidence for an amphibious phase in early proboscidean evolution. Proceedings of the National Academy of Sciences, 105(15), 5786-5791. DOI: 10.1073/pnas.0800884105
- April 1, 2010
- 10:27 AM
- 1,540 views
Fossil teeth tell of ancient ape diets
The partial faces of Anoiapithecus (left), Pierolapithecus (center), and Dryopithecus (right). (Images not to scale)
Our species is just one branch of a withering part of the evolutionary tree, the great apes. Along with the handful of species of chimpanzees, gorillas, and orangutans, we are all that is left of the hominids, and considering the threats our close relatives face we could very soon be the only great apes left. It has not always been this way. During the swath of prehistory ~23-5 million years ago known as the Miocene a variety of ape species inhabited forests through much of Africa, Europe, and Asia, and a new study published in the Proceedings of the Royal Society B looks at what the teeth of three fossil apes from Europe might tell us about their diets. Read the rest of this post... | Read the comments on this post...... Read more »
Alba, D., Fortuny, J., & Moya-Sola, S. (2010) Enamel thickness in the Middle Miocene great apes Anoiapithecus, Pierolapithecus and Dryopithecus. Proceedings of the Royal Society B: Biological Sciences. DOI: 10.1098/rspb.2010.0218
- February 4, 2008
- 11:04 AM
- 1,526 views
Say hello to the Grey-Faced Sengi!
The grey-faced sengi (Rhynchocyon udzungwensis). From Rovero, et al. (2008).
Several years ago, while on a visit to the Philadelphia Zoo, I first saw a creature I had never heard of before; the black and rufus sengi (Rhynchocyon petersi). The exhibit caption simply called it a giant elephant shrew, and even though I was familiar with smaller members of the Macroscelididae like the short-eared elephant shrew (Macroscelides proboscideus), I had never seen their giant relatives. This perhaps represents my own ignorance of the group known as Afrotheria, but the dis... Read more »
F Rovero, G Rathbun, A Perkin, T Jones, D Ribble, C Leonard, R Mwakisoma, & N Doggart. (2008) A new species of giant sengi or elephant-shrew (genus Rhynchocyon) highlights the exceptional biodiversity of the Udzungwa Mountains of Tanzania. Journal of Zoology, 274(2), 126-133. DOI: 10.1111/j.1469-7998.2007.00363.x
- October 16, 2009
- 11:28 AM
- 1,518 views
A Different Kind of Whale
Three restorations (top, left side, and bottom) of the skull of Andrewsiphius. From the Journal of Paleontology paper.
During the past 30 years the evolution of fully aquatic whales from terrestrial ancestors has gone from one of the most enigmatic evolutionary transitions to one of the best documented. Evidence from the fossil record, genetics, and embryology have been combined to document how early whales walked into the sea, but what often has gone unnoticed is the diversity of early whales. In a new paper published in the latest issue of The Journal of Paleontology, cetacean experts J.G.M. Thewissen and Sunil Bajpai describe new fossils from two very strange creatures that represent a unique part of early whale evolution. Read the rest of this post... | Read the comments on this post...... Read more »
Thewissen, J., & Bajpai, S. (2009) New Skeletal Material of Andrewsiphius and Kutchicetus, Two Eocene Cetaceans from India. Journal of Paleontology, 83(5), 635-663. DOI: 10.1666/08-045.1
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