Live Fast, Die Young: Evolutionary Outcomes of an Asteroid Impact

Figure 1: (A) "Dryophyllum" subfalcatum, (B) unknown nonmonocot,
(C) "Ficus" planicostata, (D) "Populus" nebrascensis

A new semester has started and with it an influx of new students into the lab has begun. Busy has become my middle name. So when I was looking around for a paper to write about I wanted something different and cool. Not exactly hard to find in science. The asteroid known as 2012 DA14 will narrowly miss Earth this Friday, the closest known asteroid flyby on record. And by close we’re talking within the orbits of many communications satellites. This got me thinking about and looking for recent papers about asteroids. It didn't take me long to come by an interesting new paper about the dino-killing Chicxulub bolide impact.

As of now, it is widely accepted that an epic asteroid collision ended the 135 million year reign of the dinosaurs. The Cretaceous-Paleogene boundary (KPB) extinction event is marked by the Chicxulub (CHEEK-sheh-loob) impact on the Yucatán Peninsula in Mexico. This asteroid or comet is estimated to have been about 6 miles (10 km), releasing as much energy as 100 trillion tons of TNT that caused a crater more can 110 miles (180 km) across! This impact coincides with a mass extinction event that includes the dinosaurs. Dramatic climate swings caused by the dust kicked up into the atmosphere were likely the culprit behind many of these extinctions. Before we go further, take a second to think about what you know about this extinction event. You probably think of the mass die-off of the dinosaurs and the subsequent rise of the mammals, right? But, as I have in the past, I’ll now pose a question: What about the plants?

A new paper published yesterday in PLOS Biology asks just that question. We know that in temperate North America the Chicxulub impact resulted in the extinction of over 50 percent of the plant species. From an evolutionary and ecological stand-point, that’s a lot of competitors that were taken out of the game. However, the environment was dramatically altered as well, changing to a cold and dark “impact winter.” Combined, these factors created a unique selection scenario for certain ecological strategies. The new paper takes a close look at the functional traits associated with these strategies.

The researchers measured fossil leaf assemblages spanning a 2.2 million year interval across the KPB, assessing four differing selection scenarios for functional traits. First, wrap your head around the concept of “functional traits.” These are characteristics that define species in terms of their ecological roles. In the case of leaves, these include leaf mass per area (LMA; Do you make a big, expensive leaf or a light, cheap one?) and leaf minor vein density (VD; Do you have more veins to transport lots of water?), among many others. Because leaves are the food producers, these traits are linked to plant growth and fitness. Next, you can relate these traits to the “leaf economic spectrum” (LES) that contrasts species with inexpensive short-lived leaves with fast returns on carbon and nutrients (deciduous, angiosperm, broadleaf) to costly long-lived leaves with slow returns (coniferous, gymnosperm, evergreen). The former is typically selected for in a less resource variable environment and vice versa. From this, you can get a more global perspective on changes in species composition.

The researchers measured LMA and VD for fossil leaf assemblages spanning the KPB. To do this they digitally photographed specimens that could be measured and confidently reconstructed. Then they used Photoshop to digitally separate the leaf from its rock matrix. For LMA they used ImageJ to calculate leaf area and petiole width, and then ran these numbers through empirical scaling functions (a.k.a. equations). For VD, they used a MATLAB line-counting program to isolate the veins and then manually counted the number of vein-line intersections, computing the mean distance between veins  as the sum of all line counts divided by the sum of all distances (a.k.a. a slightly less complicated equation). They ran a few scenarios to account for site and region plant specificity as well.

They found LMA to decrease and VD to increase across this time period. Even changes just these two traits reflect large physiological and biological shifts in plant functioning over a relatively short period of time. According to their data, the Chicxulub impact led to the selective extinction of species with slow strategies. This caused a directional selection away from evergreen species along with a stabilizing selection of deciduous angiosperms. The authors pose a few hypotheses in their discussion that are worth mentioning. The higher observed VD in angiosperms, and their ensuing selection, could have been driven by declining atmospheric carbon dioxide (CO2), which selects for higher hydraulic capacity. This CO2 hypothesis would, of course, not really hold water (no pun intended) for nonangiosperms and shade species, but the authors suggest that the observed increase in VD is more likely to be a direct consequence of the impact selecting for specific leaf economic strategies rather than ongoing-longer term climate change.

In this case, slow and steady did not win the race.


  Blonder B, Royer DL, Johnson KR, Miller I, & Enquist BJ (2014). Plant Ecological Strategies Shift Across the Cretaceous-Paleogene Boundary. PLoS biology, 12 (9) PMID: 25225914




(image via above citation)

Dinosaurs, Diversity, Distribution, and the LBG

For some reason I am in the mood to read a biogeography paper. I didn’t really have a particular topic in mind when I started looking, just a few journals I occasionally peruse. Then I came across a paper about palaeodiversity and the distribution of dinosaurs. I like dinosaurs and I like biogeography. So this must be a win-win. I haven’t visited the idea of dinosaur community structure and distribution since my Dino Eco post back in 2010. That paper concluded that the entire Western Interior of North America may have once been populated by a single dinosaur community with low beta diversity. Today’s paper looks at dinosaur diversity on a global scale. Last month, authors Philip Mannion et al. published a paper in Global Ecology and Biogeography that used the dinosaur fossil record to examine spatial patterns in terrestrial biodiversity.

To really get into this paper we’ll have to first explore the latitudinal biodiversity gradient (LBG). The LBG is essentially a biodiversity pattern in which species richness (a simple count of species) is highest in the tropics and declines polewards. It is a well-recognized pattern with causes that are a little less clear and that are still strongly debated. The two strongest hypotheses are that climate is the prime driver that influences biodiversity directly or via increased productivity in the tropics (warm areas are more hospitable and produce more food) or that the global distribution of area where the greater land area supports more species (the more land you have the more species will fit on it). The fossil record offers a deep time perspective that may help figure out the causes of the LBG we see today. The authors of this study chose a group of animals that was widespread, ecologically diverse, well studied, belonged to a long-lived clade, and had a fossil record that was adequate for the application of sampling standardization techniques. This gave them dinosaurs of Mesozoic terrestrial ecosystems for 160 million years, from the Late Triassic to the terminal Cretaceous (230-65.5 Ma).

Mannion and his colleagues decided to use genera as the taxonomic unit of analysis for their study as the species scale can be inconsistent in its taxonomic treatment and the family scale tends to have arbitrary content (some families comprise a single genus while others are diverse). They then assembled a comprehensive dataset of Mesozoic dinosaur genera (738), including birds. Using the Paleobiology Database, they compiled stratigraphic ranges and modern geographic coordinates for occurrences, converting modern day coordinates to paleolatitudes using software called PointTracker (uses palaeogographical reconstructions of continental drift to transform present-day coordinates to past ones). They used a number of different methods to account for sampling biases in the fossil record, and they analyzed the data in seven time slices representing epochs and then the entire Jurassic and cretaceous periods as bins.

The authors found that dinosaurs did not conform to the modern LBG. Dinosaur diversity was found to be highest at temperate latitudes rather than tropic. This result was consistent across the different time slices suggesting that the pattern was not controlled by climate fluctuations; in fact, it is possible that the Mesozoic climate gradient was much weaker than it is today. Rather, or because of this weakness, the driver of this diversity was likely the result of greater land area in these latitudinal belts. These larger land areas may also have facilitated the gigantism attained by many dinosaur species.

Figure 3 Residual dinosaur diversity (thick solid lines) after controlling for numbers of dinosaur-bearing collections (DBCs) and formations (DBFs), plotted against non-marine area (NM area) and palaeogeographical reconstructions (using Mollweide projections) for the Late Triassic (bottom), Jurassic (middle) and Cretaceous (top). From Mannion et al. (2012)

Unfortunately, these results suggest modern diversity patterns cannot be extrapolated into deep time. Guess we'll have to look somewhere else. However, it does add support to the hypothesis that land area is the primary control on the terrestrial LBG during times of weakened climatic gradient. And that, on its own, is a really interesting conclusion. The contrary, modern vs. past result also indicates that there may have been some kind of shift that took place during the middle Cenozoic that gave rise to the diversity patterns that we see today. I think I see a future study!


Philip D. Mannion, Roger B. J. Benson, Paul Upchurch, Richard J. Butler, Matthew T. Carrano, & Paul M. Barrett7 (2012). A temperate palaeodiversity peak in Mesozoic dinosaurs and evidence for Late Cretaceous geographical partitioning. Global Ecology and Biogeography, 21 (9), 898-908 DOI: 10.1111/j.1466-8238.2011.00735.x

Also, check out this guest post by article author Philip Mannion over at Dave Hone's Archosaur Musings blog: "Guest Post: Dinosaurs and the latitudinal biodiversity gradient"


(top image titled Dinosaur Diversity by Elliot Merton III found on Dinosaur Central)

Dinosaur Farts: Climate Driver or Just Gas?

Hmmm, how do you begin a serious discussion about dinosaur farts? Maybe I should call it flatulence? How about methane emissions from sauropod posteriors? To be honest, it hasn't ever been something I've thought about before. A correspondence paper, published this month in Current Biology,on this topic caught my attention, and it caught the attention of several news outlets. Makes sense, I suppose. As one article put it, "It sounds like perfect journalist bait." Obviously perfect blogger bait as well. So I wanted to take a closer look at this paper and see what it's really talking about.

The paper, by researchers David Wilkinson, Euan Nisbet and Graeme Ruxton, concerns the methane produced by sauropod dinosaurs and if it helped to drive Mesozoic climate warmth. You'll remember our talk about sauropods from the Antarctic Sauraopod: No Longer a Cold Case post from January. These were often really really big creatures with a high level of diversity and large geographic range. It has even been suggested that they may have been a keystone species in many Jurassic and Cretaceous ecosystems.

But let's first start of with a modern comparison, probably one with which you are familiar: Livestock. Ruminant animals (cows, sheep, buffalo, and goats) have a unique digestive system that can convert otherwise unusable plant material into food. This digestive system, produces methane, a potent greenhouse gas that can affect climate directly through its interaction with long-wave infrared energy and indirectly through atmospheric oxidation reactions that produce carbon dioxide. A paper published in the Journal of Animal Science in 1995 estimates that ruminant livestock can produce 250-500 L (66-132 gallons [US, liquid]) of methane per day. The U.S. EPA estimates this to contribute about 80 million metric tons of methane annually. Ruminant livestock are one of the largest methane sources in the world. If you look specifically at cattle (as the J. Anim. Sci article does), they typically emit six percent of their ingested energy as methane. In the U.S. (which as about 100 million cattle) this accounts for about 5.5 million metric tons of methane per year. That's 20 percent of the country's methane emissions! I bring up this comparison because it is directly compared to sauropod emissions in this paper.

Now, dinosaurs, particularly sauropods, are a lot bigger than cows. But in terms of abundance, they were probably less numerous, with only a few tens of individuals per square kilometer. The digestive biology of these animals has, for a long time, stumped paleontologists. Sauropods have small teeth that are shaped for gripping and clipping plants, but not really for chewing or mashing those plants. How these plants were broken down is a bit of a mystery. There have been several hypotheses from small, swallowed stones called gastroliths to microorganism-assisted fermentation. The latter, as Wilkinson, Nisbet and Ruxton point out, could be the methane producing mechanism in these animals. However, it is unlikely that these dinosaurs had an endothermic, mammalian-style metabolism. And very unlikely that they were ruminant herbivores. So the authors did some calculations for these dinosaurs based on modern non-ruminant herbivores where methane (litres per day) = 0.18 (body mass in kg)^0.97. This means that for a 20,000 kg sauropod (about a medium sized Apatosaurus louise or "Brontosaurus"), the methane emission would be 2,675 liters per day from one animal. This scales up to 6.9 tonnes/km² of methane per year and a global methane production of 520 Tg (520 million tonnes) annually. Their estimation is similar to the amount of methane humans are currently pumping into the atmosphere each year rather than cows specifically.

OK. So what do we take away from this? Many news outlets have seized onto this and made pretty outrageous claims ("Dinosaurs may have farted themselves to extinction"....uhh, wow). The fact is that we don't know for sure.We don't know what the digestive systems of these animals was like. We don't even know if they produced methane at all. These estimates were derived from a modern animal model based on the methane output of rabbits and guinea pigs fed a hay-only diet. They might make me hand back my degrees if I called that a really great animal corollary. But, as one article put it, "If you know about croc fart research, please chime in." Then there is the issue of sauropod abundance. The estimations of population size were derived from the fossil record of the Morrison Formation, a 150 million year old sedimentary rock sequence in the western U.S. and Canada. Is this Formation an accurate slice of a prehistoric ecosystem? While we are on the topic of ecosystem, you should also consider the Mesozoic era which had slightly shorter days, more land area, and a warm, moist climate that supported greater primary productivity. How does this factor in?

Ultimately, the paper doesn't say that dinosaurs farted themselves to extinction. It doesn't mention dinosaur extinction at all. What it actually says is that "methane was probably important in Mesozoic greenhouse warming" and that their "calculations suggest that sauropod dinosaurs could potentially have played a significant role in influencing climate through their methane emissions." That's it. Dinosaurs may have farted. And big dinosaurs may have farted bigger.

Read the correspondence paper for yourself here:

Wilkinson, D., Nisbet, E., & Ruxton, G. (2012). Could methane produced by sauropod dinosaurs have helped drive Mesozoic climate warmth? Current Biology, 22 (9) DOI: 10.1016/j.cub.2012.03.042

More information about modern ruminant livestock emissions can be found at:
U.S. EPA site on ruminant livestock
Johnson, K.A. and D.E. Johnson (1995) Methane emissions from cattle. Journal of Animal Science: 73(8), 2483-2492.

And a couple of good articles about this paper:
Smithsonian's Dinosaur Tracking blog's post "Media Blows Hot Air About Dinosaur Flatulence"
Pharyngula's post "The reports of dinosaurs dying of farts are greatly exaggerated"

(image from the American Museum of Natural History)

A Beautiful Feathered Tyrant

photo credit: Brian Choo

The tyrannosaurids belong to a group of carnivorous dinosaurs called theropods within the Saurischia ("reptile-hipped") dinosaurs. The Tyrannosauroidea was one of the longest-lived theropod subgroups, extending from the Middle Jurassic to the Upper Cretaceous. They are characterized by massive skulls with short but deep jaws containing large sharp teeth, elongate hindlimbs, small eyes, and highly reduced forelimbs. The Tyrannosauridae taxon includes such creatures as Albertosaurus, Gorgosaurus, Daspletosaurus, Tarbosaurus, and of course Tyrannosaurus rex. These were the dominant large carnivores during the Late Cretaceous in North America and Asia, with T. rex being the last and largest of the terrestrial carnivores. Their fossils are actually relatively common in North America, particularly their teeth. Smaller members of this dinosaur subgroup (adults with a body mass less than 1,000kg) have recently been reported from the Lower Cretaceous of China. These relatively small tyrannosaurs range from about 1.4m to about 10m in body length, and they vary in their morphology with some resembling highly specialized Tyrannosauridae and others resembling coelurosaurs (theropods more closely related to birds than carnosaurs, such as Velociraptor). This variation in earlier species suggests that there may have been some significant radiation in this group.

A new paper in the journal Nature reports the discovery of a new feathered tyrannosauroid from the Lower Cretaceous. Three nearly complete skeletons representing two distinct ontogenetic stages were found in the Yixian Formation of Liaoning Province of China. The new species has been named Yutyrannus huali. Examination of bone characteristics and phylogenetic analyses place this new dinosaur among basal (not derived) tyrannosauroids yet close to Tyrannosauridae. In particular, the pneumatic midline crest of the cranium has homologous structures to Late Cretaceous tyrannosauroids while also having features that occur consistently in basal tyrannosaurids. Other cranial features (such as a large, deep skull) and a posteriorly tapering main body are similar to derived species, and the shoulder girdle, forelimbs, and hindlimbs are similar to basal species.

Figure 3: A simplified cladogram showing the systematic position of Y. huali among the Tyrannosauroidea

Finding three specimens at two distinct ontogenetic (or developmental) stages also allowed the researchers to look for morphological changes with increasing maturity. They found that as Y. huali matured it's skull and premaxilla changed significantly. These changes could be due to individual genetic variation or sexual dimorphism. The overall growth pattern of Y. huali differed from that of derived tyrannosaurids, with Y. huali showing negative allometry (relationship of size to shape) rather than the positive allometry and near isometry seen in tyrannosaurids.

Interestingly, filamentous integumentary structures (a.k.a. feathers) were found in all three of the Y. huali specimens. At this point you may be thinking: Feathers? In a fossil? And you'd be correct. The preservation of feathers isn't found all that often in dinosaur species, either because they had no feathers or because the feathers did not preserve. In these new specimens, the feather preservation is patchy (not uncommon even in species known to have a lot of plummage) but undoubtedly there. The feathers ran parallel to each other down the spine at a 30° angle with the long axis of the tail. These dorsal feathers were at least 15cm long and densely packed. Additional feathers were found extending from the dorsal side of the neck and near the humerus. These neck feathers were longer, measuring more than 20cm. The distribution of these feathers suggests that Y. huali may have been extensively feathered in life. However, the patchy nature of the preservation of the feathers may also indicate that the distribution of the feathers on the body may have been restricted and function as display structures as they do in some other theropod groups.

In terms of evolution, feathers and hair are often developed as insulators. It has been observed that some large mammals have become almost hairless because they have a low surface-to-volume ratio that allows them to retain body heat even though they have no hair. It has been suggested that the very large Late Cretaceous tyrannosaurs lack extensive feathering for similar reasons. There is fossil evidence for patches of scaly skin and no evidence for the presence of feathers in these gigantic tyrannosaurs. However, Y. huali is an earlier specimen. The authors speculate that the discovery of Y. huali "indicates that at least one gigantic dinosaur had an extensive insulative coat of feathers, showing in turn that drastic reduction of the plumage was not an inevitable consequence of very large body size. If Late Cretaceous tyrannosaurids such as Tyrannosaurus rex were similar to Y. huali in this respect, both basal and derived tyrannosauroid dinosuars would differ from mammals in lacking a tendency to lose their integumentary covering as result of gigantism." Alternatively, if scales were the dominant characteristics of the Late Cretaceous tyrannosaurs (who lived in a warm climate) then the presence of feathers in Y. huali could have been an adaptation to a cold environment.

Xu, X., Wang, K., Zhang, K., Ma, Q., Xing, L., Sullivan, C., Hu, D., Cheng, S., & Wang, S. (2012). A gigantic feathered dinosaur from the Lower Cretaceous of China Nature, 484 (7392), 92-95 DOI: 10.1038/nature10906

Nature article "Researchers Unearth Largest Feathered Dinosaur"

There is also a Nature Podcast of this story that aired on April 5, 2012 and it includes an interview with the study's author

(first image from the Nature story linked above)

Antarctic Sauropods: No Longer a Cold Case

Credit: Charles R. Knight; (inset) Cerda/Naturwissenschaften

Saurischia  is one of the two orders of dinosaurs. The name translates to "lizard-hipped," meaning that the pelvis of these animals consists of three elements: the ilium, ischium, and pubis. The orientation of the pubis, in particular, is such that it points downward and forward at an angle to the ischium.. The saurischian dinosaurs are then divided into two major groups: Sauropoda (large herbivores) and Theropoda (bipedal carnivores). Sauropoda is the second most diverse group of dinosaurs with more than 150 valid recognized species. This group of dinos also includes the largest terrestrial vertebrates to have ever existed, with the smallest growing to 20 feet long. Typically, the animals in this group had very long necks and tails, relatively small skulls and brains, and thick, pillar-like legs. They were a long-lived group, evolutionarily speaking, spanning 100+ million years, appearing in the Late Triassic and becoming widespread during the Mesozoic. They fed on various plant species of the time, either aquatic or terrestrial, and were very likely gregarious, forming herds. To this day, sauropods are some of the most recognizable dinosaurs there are. They are an extremely widespread group and have been found on every continental landmass except Antarctica. Until now.

A new paper in the journal Naturwissenschaften reports on a new sauropod fossil find in Antarctica. Consider your average paleontological expedition: the hiking, the fossil hunting, the hammering, the tiny little brushes. Now consider all of that in the frozen land that is Antarctica. Despite these arduous collecting conditions, there have been some important fossil finds on this continent in the last couple of decades, particularly in the James Ross Basin. If you are familiar with Antarctic geography, or just search for Google a map of it, then you'll notice that the James Ross Basin is located in the Weddell Sea, adjacent to the northern part of the Antarctic Peninsula. Yep, that's marine. However, there are exposed areas on James Ross, Vega, Snow Hill, Seymour, and Cockburn islands that expose shallow marine shelf deposits of the Upper Cretaceous and Paleogene sedimentary sequence and the fossils buried within it. This is where the new bone was located.

Figure 2 *

The new sauropod fossil is from the tailbone of a sauropod exhibiting common characteristics of advanced titanosauriform sauropods (Titanosauria), particularly lithostrotian titanosaurs. Titanosauria includes over 40 known species that range in size from dwarf (size reduction through evolution) to gigantic (including some of the heaviest of the dinosaurs). These dinosaurs had small (even when compared to other sauropods), wide heads with large nostrils and spoon-like teeth. They had relatively short necks (again, in comparison to other sauropods) and long whip-like tails. Titanosaurs also had slimmer hips but a wider chest, giving them a wide-gauged stance, resulting in broader tracks. Lithostrotian titanosaurs originated during the Early Cretaceous and were the predominant group of sauropods until the mass extinction at the end of the Cretaceous. They have been found on all continents, but are particularly abundant in South America.

So how did this species get to Antarctica? The scientists have two hypotheses:

1. The presence of the titanosaur is a result of a dispersal event from South America through a paleoisthmus (a long ago land bridge) between Patagonia and the Antarctic Peninsula during the Late Cretaceous . This is a hypothesis that has already been proposed for hadrosaur dinosaurs in Antarctica.

2. Titanosaurs were already present in Antarctica during the Early Cretaceous or earlier. This hypothesis is supported by evidence of lithostrotian titanosaurs in the Albian of Australia and is consistent with studies showing many dinosaur clades spreading across Pangaea or Gondwana prior to the continental fragmentation during the Cretaceous.

Can they put a name to this new dinosaur? Not yet. They really only have 1 bone of 1 dinosaur. The important, take-home point of this paper is that a group of dinosaurs has been found on a continent for the first time. It will be interesting to see what other dinosaurs once lived on this very large continent.

Here's the paper:
Cerda, Ignacio A., Ariana Paulina Carabajal, Leonardo Salgado, Rodolfo A. Coria, Marcelo A. Reguero, Claudia P. Tambussi, Juan J. Moly. (2011) The first record of a sauropod dinosaur from Antarctica. Naturwissenschaften: 99(1), 83-87. (DOI: 10.1007/s00114-011-0869-x)

Learn more about sauropods at...
The University of California's Museam of Palentology's "The Sauropod Dinosaurs" page
Evolution & Phylogeny of Titanosauria

And more about this discovery here:
ScienceShot article "Giant Dino Lived in Antarctica"
Science Daily's article "Plant-Eating Dinosaur Discovered in Antarctica"

* Figure 2 from the paper showing the discovered sauropod fossil: "Lithostrotian gen. et sp. indet. MLP 11-II-20-1 caudal vertebra centrum, photograph (a–c) and interpretative drawing (d–f) in anterior (a, d), right lateral (b, e), and posterior (c, f) views"

(first image from ScienceShot, credit with photo, link above)

Scrat in Real Life

Have you seen the Ice Age movies? If you are like me then Scrat, the neurotic saber-toothed squirrel, is your favorite character. That poor squirrel just can't hold on to his acorn. According to a new paper published in Nature, Scrat may be closer to a real prehistoric creature than the animators realized, anatomically speaking at least.

Meet Cronopio dentiacutus. A fossil from the La Buitrera locality, Río Negro Province, Argentina was identified as a medium-sized dryolestoid, with an extremely enlongated snout and a pair of curved saber-fangs.  Dryolestoids are an extinct mammalian group belonging to the lineage that leads to modern marsupials and placentals. They thrived in South America through the Mesozoic and into the Cenozoic. This specimen was of the early Late Cretaceous (60 million years from previously known), and based on it's dental and cranial features, is unlike previously identified specimens from the Mesozoic.

Artist depiction of Cronopio dentiacutus

Unfortunately for this Scrat-like critter, there were no acorns in the Cretaceous.

The paper:
Rougier, Guillermo W., Sabastiam Apesteguia, and Leandro C. Gaetano (2011) Highly specialized mammalian skulls from the Late Cretaceous of South America. Nature: 479, 98-102. (DOI: 10.1038/nature10591)

ScienceShot Article: Meet the Saber-Toothed Squirrel

Footprints in the Sand

This story is about tracks, specifically dinosaur tracks. Footprints can be very informative, giving so much more information than just the shape of the foot. They provide information on species, body posture, locomotor ability, sociality, preferential environments, and stratigraphic and geographic faunal diversity.

As you might guess, it isn't always easy to identify fossilized dinosaur tracks. Sure, some species are easier than others like sauropods, stegosaurs, and ceratopsians. The difficulty arises in distinguishing bipedal theropods (carnivores walking on two legs) and ornithopod dinosaurs ("bird-hipped" dinos, grazers walking/running on two legs). You can see how they might look pretty similar.

A new, in press, paper in Cretaceous Research takes a look at the Dinosaur Stampede National Monument at Lake Quarry Conservation Park in central-western Queensland, Australia. This monument contains thousands of fossilized footprints of dozens of dinosaurs from the mid-Cretaceous. Since the 1970's, the popular hypothesis regarding this area is that an Allosaurus-sized dinosaur chased a mixed herd of small-bodied dinosaurs, causing a stampede. Previous studies have identified this "predatory protagonist" as a large tridactyl (three-toed) dinosaur, a theropod (likely a Tyrannosauropus). This particular taxon has a bit of a checkered history, scientists have argued about it since the early 1920's. It has also been proposed that the tracks on the monument are attributable to a hadrosaurid ornithopod (a duck-billed dinosaur that walked on two legs).

Figure 1. The Winton Formation at Lark Quarry.

These authors applied a multivariate analysis to discriminate between theropod and ornithopod tracks in order to identify the track maker. Multivariate analysis allows you to analyze more than one statistical variable at a time and therefore you are able to test multiple dimensions while taking into account several variables. Why mention the statistical test used? Some people like statistics. No really, I mentioned it because this is the first time that multivariate analysis has been used to identify tracks on this valuable piece of biological history. To perform this analysis the researchers measured all of the tracks using published line drawings, catalogued photographs, latex peels, museum casts, and actually measured the real ones themselves. The variables for the analysis included track length and width, total digit lengths, basal digit length and width, middle digit widths, and the distance from heal to the interdigital (hypex) point.

The results showed that a majority of these measurements fell within the threshold expected for ornithopod dinosaurs. In fact, the authors conclude that of the known types of theropods from this region, none of the body fossils adequately match the measurements and analyses that they did.

So what type of ornithopod was the track maker? Well, the footprints are slightly longer than they are wide, they have symmetrical toes, have claws, and have a V-shaped central digit. Of the known large Cretaceous ornithopods, previous studies have concluded that it could be either Ambyldactylus, Caririchnium or Iguanodonipus. Of these, only the iguanodontian dinosaur, Amblydactylus, shares the distinctive features exhibited in the Lark Quarry tracks. The tracks are remarkably similar to ornithopod tracks from Canada named Amblydactylus gethingi and so the authors suggest re-naming the Lark Quarry tracks Amblydactlyus cf. A. gethingi. In all likelihood, the footprints were made by a large ornithopod standing approximately 2.5 meters tall at the hips, likely a more primitive member of the group, probably similar to Muttaburrasaurus langdoni. This species specifically because it has been found in similarly aged rocks only a few hundred kilometers from Lark Quarry. The stampede of the smaller dinosaurs also represented in these rocks was probably due to the approach of this larger dinosaur. A large herbivore spooking a group of smaller dinosaurs is not exactly as exciting as a predator chasing them down but, in this case, is more accurate.

The authors state that if this identification is correct then it removes any published evidence that a large theropod dinosaur existed in the Australian Cretaceous. However, I do recall posting an article about a new theropod discovered in Australia from 110 million years ago - which I'm pretty sure is the Cretaceous period (144 to 65 million years ago?) - so I'm not sure about this wiping out all evidence thing. Just sayin'.

This is the paper:
Romilio, Anthony and Steven W. Salisbury (2010). A reassessment of large theropod dinosaur tracks from the mid-Cretaceous (late Albian-Cenomanian) Winton Formation of Lark Quarry, central-western Queensland, Australia: A case for mistaken identity. Cretaceous Research: in press. (DOI: 10.1016/j.cretres.2010.11.003)

And here's some more reading material on the subject:
http://www.uq.edu.au/news/?article=22416
http://www.smh.com.au/world/science/giant-vegetarian-set-off-dinosaur-stampede-20101217-190qn.html
http://www.uq.edu.au/news/index.html?article=21805
http://www.uq.edu.au/dinosaurs/

Its What's For Dinner

The tyrannosaurids belong to a group of carnivorous dinosaurs called theropods within the Saurischia ("reptile-hipped") dinosaurs. They lived during the Cretaceous, 85-65 million years ago. They are characterized by massive skulls with short but deep jaws containing large sharp teeth, elongate hindlimbs, small eyes, and highly reduced forelimbs. The Tyrannosauridae taxon includes such creatures as Albertosaurus, Gorgosaurus, Daspletosaurus, Tarbosaurus, and of course Tyrannosaurus rex. These were the dominant large carnivores during the Late Cretaceous in North America and Asia. The T. rex is the last and largest of the terrestrial carnivores. Their fossils are actually relatively common in North America, particularly their teeth. These teeth, with their large banana shape, leave recongnizable markes on the bones of other dinosaurs. You would think that this would make it easy to piece together the feeding habits of these dinosaurs, but it is still difficult to even broadly classify the animal as predator, scavenger, or both. We all grew up thinking of T. rex as a mighty hunter, but the evidence against the predator hypothesis includes the animal's small eyes (most predators have large eyes to help find and follow prey), small arms (difficult to hold struggling prey with dainty little forearms), and large legs (seem fast but are actually slow). Add to it the fact that there is evidence of T. rex teeth scoring bone but not actually killing the prey, bones have healed. Scavaging, however, uses all of these traits as a plus and includes supporting evidence such as large olfactory lobes (smelling foul, dead meat well helps you find it). However, if you look at extant, large predators they are opportunists, scavanging when it is available, and if you look at animals such as birds, sharks, and snakes you will notice that little arms aren't that much of a disadvantage. See how there is some confusion?

In a study published in PLoS ONE this week, palentologists discuss a different type of T. rex feeding habit. During a study of Maastrichtian (latest age of the Late Cretaceous) dinosaurs one of the researchers found a large theropod pedal phalanx (foot/toe bones) that had tooth marks on it that were made by a large carnivorous dinosaur. Considering the geographic region (North America) and the time period, T. rex was the only large carnivore known and so a very likely candidate for inflicting the bone damage. They examined this bone as well as other dinosaur specimens. They found a total of 17 specimens bearing tooth marks made by Tyrannosaurus. The deep U- and V-shaped gouges and shallower scores resemble those found on the pelvis of a Triceratops, and closely resemble the furrowed ‘puncture and pull’ traces that have previously been attributed to T. rex. Four of the examined specimens represent Tyrannosaurus. That's right, we're talking cannabalistic Tyrannosaurus rex!

Figure 2. Tyrannosaurus rex bones bearing
 tooth marks made by Tyrannosaurus rex.

The authors argue that the marks on the bones are the result of feeding rather than fighting. They say that the traces would be difficult to inflict on a live animal, and that, in the case of one bone, the marks are the result of two or three bites. Considering that most animals probably wouldn't sit still while a Tyrannosaur repeatedly bit them, that seems likely. Additional evidence includes where the bites occurred - on the toes (tightly bound in life and not the targets during a fight) rather than the vulnerable head or flanks. Finally, there is no bone remodeling (healing) evidenced, suggesting that the animal died.

Put this together and it gives more evidence to the hypothesis that Tyrannosaurus was an indiscriminate, opportunistic feeder. It didn't just go for herbivorous dinosaurs but also other Tyrannosaurs. The bone marks found in this study were probably the result of scavenging. However, you can't rule out that the Tyrannosaur killed its prey and fed on it over a long period of time.

Cannibalistic Tyrannosaurs, whew, that's a visual right? But, if you think about it, cannibalism isn't all that uncommon in nature. I mean, its been seen in bears, alligators, hyenas, etc. So it seems a good arguement for T. rex as well.

Very cool.

Read more in the paper (its free access):
Longrich Nicholas R., Horner John R, Erickson Gregory M., and Currie Philip J. (2010) Cannibalism in Tyrannosaurus rex. PLoS ONE: 5(10), e13419. (DOI: 10.1371/journal.pone.0013419)

The Bite of the Terror Bird

Figure 1. Skull of Andalgalornis steulleti (FMNH P1435).

So you're flipping through various websites and journal table of contents. You come across an article about the feeding behavior of the ancient "terror bird." I think it's pretty clear that you must stop and read it.

Andalgalornis steulleti is a member of an extinct group of large, flightless birds known as phorusrhacids. This group were predominatly a South American radiation of gruiform birds from the middle to lower Paleocene and are most closely related to extant seriemas. Phorusrhacids are called "terror birds" due to their gigantic body sizes, large skulls, and carnivorous lifestyles. The members of this group were ground predators or scavengers that were likely apex predators that dominated their environment in the absence of large carnivorous mammals. A. steulleti lived approximately 6 million years ago in Argentina, it weighed about 40kg, stood 1.4m high, and had a skull length of 370mm. This large, rigid skull was capped with a hawk-like hooked, yet curiously hollow, beak. The feeding behavior of these birds has only been speculated at up till now. This new study performed a biomechanical analysis of the skull using comparative anatomy and engineering (Finite Element Analysis [FEA]) to predict the behavior of the skull. Basically, they looked at the skull itself, compared it to other skulls, and ran it though a CT scanner for analysis.

Figure 2. Stress (Von Mises) distribution of FE models.

Now, if you look at most birds you'll notice that their skulls allow for a lot of mobility between their bones. This gives them light but strong skulls. A steulleti, on the other hand, showed rigid beams in these normally mobile areas. This gave the bird a very strong skull, particularly in the fore-aft direction. The FEA analysis worked with the 3D models created by the CT scans to simulate and compare the biomechanics of biting straight down, pulling back with the neck, and shaking the skull side to side. These are all attack and dismembering motions (lovely). One of the neat things about FEA analysis is that it gives you color images that show areas of low stress as cool-blue and high stress as white-hot (image left). The results from this analysis show that the terror bird was well adapted for driving its beak in and the pulling back. Its marks weren't so high in the shaking side to side motion. Some more comparative anatomy came in when the researchers tested bite force. They had an eagle bite down on a bite meter - bet that was fun to try to do - and they used that information to compare it to the bite of A. steulleti. Pretty close, as they are both large birds with big, hooked beaks. The results showed that the terror bird had a lower than expected bite force that was weaker than the bite of similarly sized carnivorous mammals. This weaker bite force was likely supplimented by the driving down and pulling back motion that they found with the previous test. Overall, behaviorally speaking, the bird probably located prey, stabbed it with its beak and then implimented a repeated attack-and-retreat strategy, puncturing its prey until it was eatable.

Here's the article:
Degrange, Federico J., Claudia P. Tambussi, Karen Moreno, Lawrence M. Witmer, and Stephen Wroe. (2010) Mechanical Analysis of Feeding Behavior in the Extinct 'Terror Bird' Andalgalornis steulleti (Gruiformes: Phorusrhacidae). PLoS ONE: 5(8), e11856. (DOI: 10.1371/journal.pone.0011856)

and...
http://www.sciencedaily.com/releases/2010/08/100818171916.htm

Thar She Blows!

When you hear the words "raptorial sperm whale" what do you think of? A warped Moby Dick? A SyFy original movie? The picture above? Go with Door #3.

A new paper in Nature titled "The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru" describes the discovery of one of the biggest predators to ever live - a whale eating whale. Whoa.

The newly discovered whale has been named Leviathan melvillei, a name loosely translated as 'Melville's sea monster.' The bones were discovered in Cerro Colorado in the Pisco-Ica Desert on the southern coast of Peru two years ago by paleontologists Olivier Lambert and Klaas Post and their team. The researchers were able to recover 75% of the whale's skull, including large fragments of jaws and several teeth. The huge whale (13.5-17.5 meters long) is thought to have lived and died about 12-13 million years ago and is most closely related to modern day sperm whales (Physeter macrocephalus). Today's sperm whales have small teeth (less than 26 cm), lack functional teeth in the upper jaw, and feed by suction - a morphology suited to a squiddy diet. Conversely, L. melvillei has large, interlocking teeth approximately 36 cm (15 in) long. The mouth itself is 3 meters (9 ft) long and just over 2 meters (7 ft) wide with a skull structure that suggests very powerful biting muscles. Put these traits together and you get an animal that hunts in a similar way to extant killer whales (Orcinus orca), using its teeth to capture prey and tear off flesh. Yum. L. melvillei is thought to have fed on medium-sized (7-10 m long) baleen whales and other large prey; it would have been an effective competitor with Megalodon (the giant shark of that age).

If you picture a sperm whale what do you see? Yeah, massive head and itty-bitty mouth (well, relatively at least). That big ole head is mostly forehead, a forehead that holds the "spermaceti organ." This organ is composed of a series of oil and wax reservoirs buttressed with massive partitions of connective tissue, and it's thought to help the whales dive deeply. The skull of L. melvillei exhibits a curved basin atop the snout which suggests that it also had this organ, even though it was not a specialized deep diver. So why have it? The authors suggest that the organ existed before modern sperm whales adapted to deep diving, probably for other functions such as echolocation and/or acoustic displays. Another possibility? Aggressive head-butting. Think underwater goats/rams. Wow. Well, there are records of at least two nineteenth-century whaling ships were sunk when large male whales punched holes in their sides with their foreheads, so the idea isn't too far out there. The underwater head-butting could have been used to show dominance in such situations as contests over females. Its just kinda fun to picture two huge whales swimming at each other at full speed and then crashing their heads together - imagine the wave off of that!

The massive cetacean is thought to have been driven to extinction by changes in its environment, namely its prey and the effects of climate cooling. At that time baleen whales were widely diverse and then underwent a significant changes in number, diversity, and size. Changes in prey are known to impact top predators in a drastic way - no prey means a predator must adapt or go extinct. L. melvillei's surviving relatives (Physeter, pygmy and dwarf sperm whales) are deep-diving, squid-eating specialists - a very different ecological niche than L. melvillei.

Here's the article:
Lambert, Olivier et al. (2010) The giant bite of a new raptorial sperm whale from the Miocene epoch of Peru. Nature: 466, 105-108. (DOI: 10.1038/nature09067)

and here's some write-ups about it:
http://www.nature.com/news/2010/100630/full/news.2010.322.html
and
http://www.npr.org/templates/story/story.php?storyId=128213707&sc=fb&cc=fp

Horny Dino

Another new species of dinosaur has been unearthed. This one is a dinosaur from Mexico, specifically the Cerro del Pueblo Formation, the basal formation of the Difunta Group in the Parras Basin within the state of Coahuila. Mexico is not very well known dinosaurily speaking. In fact, only 4 dinosaur species from Mexico have been found and described in the scientific literature. The newly described fossil is 72 million years old and has been named Coahuilaceratops magnacuerna (Koh-WHE-lah-SARA-tops mag-NAH-KWER-na). Analysis of the skull and skeletal bones shows the individual to be an adult, and the remains of a juvenile were also found at the same site. An adult C. magnacuerna was 22 feet long, 6-7 feet tall at the shoulder, had a 6 foot long skull, and weighed 4-5 tons.

Did you catch the "ceratops" part of that name? Yep, it is one of the horned dinosaurs we all know and love. In this case the horns are up to 4 feet long, making it the largest set of horns found on a dinosaur to date. The purpose of the huge horns is unclear, but it is hypothesized that they were related to reproductive success (attracting females, fighting males). The skull also had a very thick nasal bone and a small rounded nose horn unlike horns seen in other ceratopsid dinosaurs.

I suggest going back to the Dino Eco story from April. There you will see a good picture and a description of how North America was in the Late Cretaceous Period. At this time, not much of Central America had formed and Mexico was the southern-most point of the continent. Now this area is dry and deserty, but 72 mya it is thought to have been a humid estuary much like the present-day Gulf Coast, evidenced by fossilized snails and clams. C. magnacuerna was found in an area such as this along with duck-bill dinosaur fossils, two other (less well understood) horned dinosaurs, large tyrannosaurs, and small Velociraptor-like dinosuars. So many fossils in one place suggests a massive death event associated with a large storm, such as a hurricane.

As if the wealth of bones was not enough, researchers also discovered the largest assemblage of dinosaur trackways known from Mexico. The large area that is crisscrossed with the tracks of many dinosaur species shows a diverse picture of species in this area.

Here's the story:
http://www.sciencedaily.com/releases/2010/05/100528124513.htm

Birds of a Feather

After a brief hiatus, in which I was sunburned beyond all recognition (UV rays bad), its back to the sciencey goodness. I figured I would lead off with a story about feather evolution, and if you've been reading this blog then you know that I just love a good feather evolution story. This one was reported on the ScienceNOW website.

It is generally agreed that birds evolved from small dinosaurs about 150 million years ago. As you may already know, the first birds weren't exactly the best fliers. There has been a debate on about how the feathers of these early birds/later dinos were actually used - for gliding or for more sustained flight.

Robert Nudds of the University of Manchester and Gareth Dyke of University College Dublin took a close look at a 100 million year old bird by the name of Confuciusornis. They were looking to see whether or not the feathers of this bird were strong enough to provide both lift and withstand breaking due to rapid flapping of the arms/wings.

They applied Euler-Bernoulli beam theory (or Engineer's beam theory) to this feathery conundrum. This theory is used by engineers to calculate the load bearing strength of structural beams. The thoery was tested out on the bird's primary feathers (outer edge of wing - the big ones) because they bear the most load. After taking lots of measurements of the feathers (diameters, lengths, etc) and combining it with the estimated body weight of the bird, they plugged the values into the Euler-Bernoulli equations. The conclusion: The wings would have buckled under the stress. The same analysis was performed on the older (140 mya) Archaeopteryx. It also failed.

Other scientists are not completely sold on these conclusions. They cite examples of fossils found in lake and marine sediments, saying that some flight (rather than simple gliding) took the birds to those distances. Also, fossilized feathers can be difficult to measure accurately which could affect the results of the calculations.

The story link:
http://news.sciencemag.org/sciencenow/2010/05/did-first-feathers-prevent-early.html

(image from http://www.toyen.uio.no/palmus/galleri/montre/english/161_632.htm)

Diminutive Dino

In 1895, Franz Baron Nopcsa examined a set of small sauropod dinosaur bones and concluded that they belonged to a species subjected to island dwarfism, and named it Magyarosaurus dacus. Island dwarfism (phyletic nanism) is the reduction in size of large animals that occurs when a species' gene pool is limited to a very small environment, such as an island, and the particular conditions in that environment (competition, food sources, territory, etc.). M. dacus was a titanosaurian sauropod from the Upper Cretaceous (Maastrichtian) and was about the size of a horse, which is very small when compared to other sauropod species. Since then, with the discovery of other large sauropods at the same site, it has come into question whether or not M. dacus was actually a dwarf or not.

More recently, these bones were examined for their microstructure, particularly the rebuilding that happens to bones as an animal ages. This analysis indicated that M. dacus had bone microstructure identical to that of a fully mature sauropod. The diminutive dino also had an extremely reduced growth rate but maintained the high metabolic rates typical of other sauropod species. Based on this research, they were able to show, conclusively, that M. dacus was indeed an island dwarf species. The other sauropod bones at the site were also shown to belong to a different sauropod species.

Here's the article:
Stein, K. et al. (2010) Small body size and extreme cortical bone remodeling indicate phyletic dwarfism in Magyarosaurus dacus (Sauropoda: Titanosauria). Proceedings of the National Academy of Sciences: published online. (DOI: 10.1073/pnas.1000781107)
and http://www.sciencedaily.com/releases/2010/05/100503111513.htm

Baby Feathers

It seems that quite a few stories from Nature caught my attention this week. This is another story about dinosaurs, specifically feathered dinosaurs. Not about a new species, their ecology, or their behavior, but rather about the development of feathers.

Two 125-million year old Similicaudipteryx specimens have been recovered from the Lower Cretaceous Yixian Formation of western Liaoning in China. Similicaudipteryx belongs to the group of dinosaurs known as oviraptorosaurs (egg-stealing dinosaurs). The specimens show the dinosaur species in two stages of development - early adulthood and juvenile. The adult has pennaceous or contour wing and tail feathers which resemble a quill pen and are mostly similar in size. The juvenile has longer tail than wing feathers which both have a flat, ribbon-like stem at one end and are pennaceous at the tip. This is the first time that juvenile dinosaurs have been found to have different types of feathers than adults, a transition that we do not observe in modern birds. Other scientists have suggested that the juvenile feathers may be from a moulting phase. The paper's authors explain that if this is the case you would expect the ribbon-like part of the feather to be shorter. They continue on to suggest that the juvenile's partially-pennaceous feathers may be the result of delayed gene expression, expression that is activated early in the life of modern birds.

The Nature article:
Xu Xing, Xiaoting Zheng and Hailu You (2010) Exceptional dinosaur fossils show ontogenetic development of early feathers. Nature: 464, 1338–1341. (DOI: 10.1038/nature08965)
(Full Text -- if you have access, it includes some really great photos and diagrams)

and http://www.nature.com/news/2010/100428/full/news.2010.208.html

Dino Eco

The community ecology of the dinosaur age. Scientists argue over community structure in modern settings, so imagine the difficulty in piecing together a dinosaur community.

Scientists from McGill University have used data from the Paleobiology Database to look at the diversity of dinosaur species in North America, specifically from the Maastrichtian formations from 71 to 65 Ma, just before the major dinosaur extinction event. They were interested in alpha diversity (diversity within a particular area or ecosystem) versus beta diversity (diversity between ecosystems or along environmental gradients).

People tend to think that dinosaur fossils are abundant and wide-ranging. This isn't the case; fossils are actually relatively rare and patchy in their distribution. In community ecology, particularly diversity measures, sampling can make a big difference in the results, the more you sample and the more individuals you collect the better picture of the community you get. See where I'm going with this? However, there are ecological techniques to correct for this sampling bias (rarefaction, etc). The scientists in this study corrected for sampling bias by only considering four formations in the northwestern interior that each included more than 100 dinosaur specimens. They looked at the number of unique species at each site (unique meaning found in only 1 place), compensating for the unevenness in samples between sites, and used that to estimate the number of species missing from the fossil record.

They found that the entire Western Interior of North America may have once been populated by a single dinosaur community. These data suggest that differences in species in this region were relatively low, so low as to consider it a single homogeneous fauna that ranged over an entire continent. In terms of the diversity measures, beta diversity was low, there were not multiple dinosaur faunal regions. Low beta diversity is not an unknown pattern. It is something that we can observe in various communities right now, but it is on a much smaller geographic scales. Modern environments can be very patchy allowing different species to exploit various habitat types, and so low beta diversity is seen in smaller, homogeneous habitats. It is likely that the dinosaur communities discussed in this paper experienced large, homogeneous habitats exposed to stable climates. Many were not isolated to small regions and constrained by small, isolated environments. Rather, they were able to colonate and dominate vast areas. This conclusion naturally leads to more questions involving dinosaur migration, gene flow, habitat type, etc.

Its a good start to piecing together the ecology of this era and something which can be updated as more data is collected.

Here's the PNAS article:

Vavrek, Matthew J. and Hans C.E. Larsson (2010) Low beta diversity of Maastrichtian dinosaurs of North America. PNAS: published online. (DOI: 10.1073/pnas.0913645107)

and http://www.wired.com/wiredscience/2010/04/north-american-dinosaurs-were-one-big-happy-family/
and http://www.sciencedaily.com/releases/2010/04/100421223712.htm

(second image from www.cmnh.org)

G'day New Dino

An ancestor of Tyrannosaurus rex (known as NMV P186069 for now) has been found at Dinosaur Cove in Victoria, Australia. A 110 million year old, 30 cm pubis bone was found and is distictively tyrannosaur because of its unique shape - rod shaped with two expanded ends, one of the ends flattened and the other boot shaped. The dinosaur would have been approximately 3 meters long and about 176 lbs with a large head and the small arms typical of a tyrannosaur. The large size of the T. rex is thought to have evolved later (about 40 million years later). This is the first ever evidence of tyrannosaur dinosaurs in the southern continents. The 110 million year old date of this fossil puts it somewhere in the middle of the continental breakup (from supercontinent to present day continental positions), suggesting that there may be more large predators yet to be discovered on the southern continents - the diversity of the tyrannosaur group isn't still fully understood.

Read more here: http://news.sciencemag.org/sciencenow/2010/03/scienceshot-t-rex-had-a-southern.html
and here: http://www.sciencedaily.com/releases/2010/03/100325143045.htm

(image from arizonaskiesmeteorites.com)

An exquisitus find

A brand new raptor species - of the dinosaur, not the bird, variety - has been found in the Inner Mongolia, China (insert appropriate Jurassic Park movie music here). The new dino, named Linheraptor exquisitus, was found in near-perfect condition and is an almost complete skeleton. L. exquisitus belongs to the Dromaeosauridae family of dinosaurs which is made up of theropods (such as velociraptor and T. rex) that lived during the Late Cretaceous period. It is approximately 2.5 meters long and would have weighed around 25 kilograms.

Read lots more about this discovery here: http://www.sciencedaily.com/releases/2010/03/100319085257.htm

Dinosaur-Eating Snake!

(image from nature.com)

Dun-dun-daaaaa....

A dinosaur-eating snake? No way.

I'm picturing a giant (because things were pretty giant back then) python having an epic battle with a T-rex, constricting it to its slow and agonizing death, and then unhinging its jaw to swallow the dead dino whole.

Umm...not so much.

It appears that ancient snakes attacked dinosaur nestlings as well as invaded dino nests to swallow their eggs. A feeding strategy you see in many snake species to this day. The linked article describes an analysis of a Cretaceous period dinosaur nest which appears to have the bones of a snake along with the dinosaur eggs. This suggests that the snake was feeding on or about to feed upon the nest's contents.

As with many of the greatest discoveries in science, this discovery was made from a fossil that was briefly analyzed decades ago and then put into storage only to be rediscovered. Additional information about the snake's anatomical structure as well as new predation pressures upon various dinosaur species was also detailed.

The full story can be found in Nature News: http://www.nature.com/news/2010/100302/full/news.2010.98.html
and at the New York Times: http://www.nytimes.com/2010/03/04/science/snakes.html?ref=science

Not exactly the epic battle that I had first envisioned, but still pretty neat.