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It’s a Bird! It’s a Fossil Friday

Were you able to figure out what this ancient skull belonged to?

Marsh

It looks for all the world like a bird, but birds don’t have teeth, do they?

Certainly not now, but early in avian history, they did. Teeth are but one of the many pieces of evidence that connects them to theropod dinosaurs like Velociraptor and Deinonychus. This particular bird was named Hesperornis regalis, the “royal western bird”. It lived in the Late Cretaceous, at the same time as such famous dinosaurs as Tyrannosaurus rex and Triceratops and marine reptiles like mosasaurs and elasmosaurs.

Grebes and loons. Studer's Popular Ornithology: The Birds of North America  by Jacob H. Studer, with illustrations by Theodore Jasper (1878)

Grebes and loons. Studer’s Popular Ornithology: The Birds of North America. Jacob H. Studer, with illustrations by Theodore Jasper (1878)

The picture of the skull above was published by Othniel Marsh in 1880. The skeleton Marsh described and several other specimens show that Hesperornis was a diving bird, much like grebes, loons, and some rails and cormorants. Like the flightless cormorant, Hesperornis had very small wings and lacked the ability to fly. Some diving birds, like penguins, use their wings to “fly” through the water, but Hesperornis, like its modern counterparts, used their feet to propel themselves. Its feet were likely lobed, like grebes, rather than fully webbed like most aquatic birds.

Hesperornis showing jaw feathers. http://oceansofkansas.com/hesperornis.html

Hesperornis showing jaw feathers. http://oceansofkansas.com/hesperornis.html

Hesperornis was a large bird, standing close to a meter (3 feet) tall and 1.8 meters (6 feet) in length. Its beak was long and pointed, with teeth on its maxilla and all but the tip of the mandible, or lower jaw. According to work by Tobin Hieronymus, the parts of the jaws with teeth were covered in feathers, with keratin covering the toothless portions. It lived in coastal waters, diving for fish and trying to avoid the aquatic reptiles that were the apex predators of the time.

Hesperornis regalis skeleton at the Canadian Fossil Discovery Centre, Morden, MB. Wikipedia.

Hesperornis regalis skeleton at the Canadian Fossil Discovery Centre, Morden, MB. Wikipedia.

In Arkansas, Hesperornis has been reported from the Ozan Formation in Hempstead County, a series of mostly sandy, limey mudstone, typical of warm coastal marine areas. As one would expect, given Hesperornis‘s aquatic nature, all the other fossils found with it represent marine animals, including sharks, bony fish, turtles, mosasaurs, and pliosaurs. During the Late Cretaceous, when these sediments were deposited, southwest Arkansas was at the eastern edge of the Western Interior Seaway, a marine environment created by high sea levels that flooded much of the central United States.

This find represents the southernmost extent of Hesperornis’s range, which extended up into the Arctic. It was a lot warmer then, but still cold at the poles. It should be kept in mind though, that the find consists of one partial bone, the left tarsometatarsus, part of the lower leg. It is easily recognizable as avian and has been identified as Hesperornis due to its age and size, although Dr. Larry Martin stated it could be a new taxon. We will just have to wait until more fossls turn up to know for sure. Parts of the Ozan Formation are quite fossiliferous, so there is a chance that more will be found.

Fossil Friday, Going Swimmingly

No one guessed what the fossil for this week was. Take a look at the image below and see if you can figure out who this vertebra belongs to before continuing on after the image. As you may have deduced from the title of the post, it is an aquatic animal.

Picture1

This is not the lizard you're looking for. Platecarpus. Wikimedia.

This is not the lizard you’re looking for.Platecarpus. Wikimedia.

This fossil is a really nice dorsal vertebra of a giant marine reptile. Most of the ones usually found in Arkansas are mosasaurs, but this one is different. It lived at the same time as the mosasaurs, placing it in the Late Cretaceous Period. As with all other Late Cretaceous fossils in Arkansas, it was found in the southwest corner. Specifically, it was found near Saratoga, Arkansas in Howard County by local resident Matt Smith. Interestingly, the very same spot has also turned up several nice mosasaur fossils, so it was a popular place in the Cretaceous seas. It shouldn’t be too surprising though, as it was a nearshore environment in a tropical climate much like the Bahamas today, so there would have been lots of good eating for hungry marine predators.

Elasmosaurus

Elasmosaurus

Ok, enough of the teasing. The vertebra we have here is that of a plesiosaur known as Elasmosaurus. These are classic marine reptiles that most people are familiar with to some degree. They have sometimes been described as looking like a snake that swallowed a sea turtle because of the relatively wide bodies with oar-like flippers and a very long neck. They are thought to have spent much of their time slowly cruising the seaways, using their long necks to catch fish unawares. some people have even suggestd that they floated at the surface of the water with their head out of the water, so that fish could not see it, allowing them to plunge their head down into the water and catch fish from above. That is pure speculation though. Right now there is no way to really test such hypotheses, so feeding methods remain in the realm of speculation until such time as someone figures out a way to test it adequately. At the moment, biomechanical tests indicate that either method would have been possible.

Mosasaur vertebrae. Note the rounded left end.

Mosasaur vertebrae. Note the rounded left end.

So if you find a vertebra like this, how do you tell whether it is a mosasaur or plesiosaur vertebra? They can both be large, although the one pictured here is the largest one I have ever seen found in Arkansas. The best way to tell is to look at the ends of the centrum, otherwise known as the body of the vertebra. Most of the time, that is all that is preserved, as all the processes that stick out have been broken off, like we see in this one. Plesiosaur vertebra have flat, possibly even slightly concave, or indented ends. Mosasaurs, on the other hand, have what is known as procoelous vertebrae, which have one end convex, a bit more rounded off. These differences make mosasaur vertebrae look more like over-sized lizard or croc vertebrae, whereas plesiosaur vertebebrae look more like the disc-like vertebrae seen in fish. This may mean that plesiosaurs were more adapted for aquatic life than mosasaurs. Both were clearly fully aquatic, what with neithr one of them having legs of any sort, but plesiosaurs appear to have been aquatic for longer, giving their spine to more fully adapt.

cope-70

Indeed, when we look at the age of the rocks their fossils have been found, mosasaurs are restricted to the late Cretaceous, whereas the plesiosaurs first appeared all the way back in the Triassic (another successful prediction based on evolutionary theory). This means plesiosaurs had well over 100 million years advance on the mosasaurs. It didn’t really help them in the end though. About the time mosasaurs appeared, plesiosaurs were declining. Mosasaurs evolved and spread quickly, becoming the dominant marine predator of the Latest Cretaceous. Does this mean that mosasaurs outcompeted the plesiosaurs? Not necessarily. It has not yet been sufficiently determined whether or not mosasaurs simply filled a niche left open by the plesiosaur decline or competitively excluded them. there is also the argument to be made that they would not have competed at all. The body shapes of mosasaurs and plesiosaurs are quite different, indicating they filled different niches in the marine realm, so they weren’t going after the same food sources. Therefore, there is no particular reason we know of that they could not have existed alongside each other without adversely affecting each other.

 

elasmosaursize

Nessie-montage-Tetrapod-Zoology-600-px-tiny-July-2013

Nessie picture collection by Darren Naish, Tetrapod Zoology, July, 2013.

Most people are familiar with them due to the much discussed “Loch Ness Monster”, which has often been said to be a supposed plesiosaur that has somehow survived for 70 million years. Of course, that idea doesn’t make a lot of sense for several reasons. It is highly unlikely that plesiosaurs could have lived for so long without leaving any trace of a fossil record. It does happen occasionally though. The coelacanth is a famous example of that, for a long time having a good 65 million year gap in their fossil record. They were thought to have gone extinct along with the dinosaurs until living specimens were caught. We know more about them now and their fossil record is no longer quite as limited as it once was, but it still has wide gaps in the fossil record. But more serious problems for Nessie arise from the fact that plesiosaurs were large, air-breathing marine reptiles. Coelacanths went unnoticed because they moved to the bottom of the sea, an option not available to plesiosaurs, which were limited to surface waters, and relatively shallow waters at that. That means they lived in exactly the sort of marine environments most visited by humans. That makes it hard for them to hide from people today and puts their bones in prime spots in the past to fossilize. Then of course, there is the problem that Loch Ness is a freshwater lake and plesiosaurs were adapted for saltwater. Not to say a species couldn’t have adapted for freshwater, but it does make it less likely. Finally, there would have to be enough plesiosaurs big enough to support a breeding population and there is simply no way they could all hide within the confines of a lake, especially since they have to live at the surface much of the time.

baskingsharkdecompBut what about the supposed bodies that have been found of plesiosaurs? They have all been identified as decomposing backing sharks. Basking sharks are one of the largest sharks known today. they are pretty harmless though, as they are filter feeders, much like the whale shark. When their bodies decompose, the jaws typically fall off pretty quickly. So what has been identified as the head of a “plesiosaur” was actually just the remaining portions of the cartilaginous skull without the large jaws. If you look at the picture of the asking shark here, there isn’t much left after you remove the jaws.

baskingsharkCetorhinus_maximus_by_greg_skomal

Next week is Labor Day on Monday, so I will likely not post a new fossil next week. I will post something next week, just not a mystery fossil. But there will definitely be one the following week, so please come back to see the next fossil and see if you can guess what it is before Friday. In the meantime, enjoy your vacation.




Taphonomy Tuesday

Slide1Taphonomy Tuesday? What the heck is taphonomy, you ask? Taphonomy is the study of burial processes and all the changes that take place betwixt death and being collected as a fossil. One might also include the effect of sexiness in what fossils get studied and forgotten about, way more people are interested in tyrannosaurs than fossil mosquitos, for instance. Change comes to all things and paleoaerie is no exception. You may have noticed that the answer to Monday’s mystery fossil did not get posted on the blog last week, although it was posted on the Facebook page. That will be rectified today. But first, a couple of pieces of news.

Mystery Monday and Fossil Friday will be suspended for the summer so I can work on other aspects of the website. I would like to make some different posts and add more to the site. however, for those of you who are primarily interested in the fossils, they will return along with school, teachers, and homework, although hopefully a bit more fun than either doing or, even worse, grading homework (trust me, having been both a student and teacher, grading is almost always more painful than doing the assignments). In the meantime, you can look forward to more varied posts, the addition of a couple of things, such as a techno page for recommended apps and multimedia and an Amazon store in which you can peruse recommended items (and in a small way support the work of paleoaerie, which while free to you, is not to me). So I hope you will stick with me through these Darwinian changes and avoid the pitchforks and torches (ed. note: in keeping with the medieval theme of the picture, I thought about saying burning faggots, but so few people these days know that in olden times, faggot simply meant a bundle of sticks, language too evolves).

modlogoThe other big news is that I have started a collaboration with the Museum of Discovery in Little Rock to host a celebration of National Fossil Day in October. I am really looking forward to it and, between me and the museum educators at the MoD, we have a lot of ideas for things to do. I hope everyone can come out and enjoy the festivities and learn about fossils in Arkansas and beyond firsthand.

Platecarpus_skull

Platecarpus skull fossil at Plano West Senior High Photo Credit:Wesley Kirpach. Wikimedia Commons.

Now, for that fossil…Did any of you recognize this as the skull of a mosaaur, specifically that of Platecarpus? To picture a mosasaur, imagine a komodo dragon, replace the feet with flippers, and compress the tail so it is taller than it is wide (aka laterally compressed) so it looks more fish-like than lizard-like, and you have a pretty good view of a mosasaur. There is a reason for that. Komodo dragons are part of a group of lizard called monitor lizards, which are thought to be close relatives of mosasaurs and so are likely an excellent model for what the ancestral animal of mosasaurs looked like before they became aquatic.

Platecarpus. Wikimedia.

Platecarpus. Wikimedia.

Platecarpus was a carnivorous marine reptile that swam in the Cretaceous seas. While dinosaurs like Tyrannosaurus rex and Triceratops roamed the land, Platecarpus and its relatives patrolled the oceans. This is one of the most common mosasaurs, so much of what we know about them comes from fossil of this genus. It was smaller than many of the other mosasaurs. Some, like Kronosaurus, could reach up to 17 meters, but Platecarpus only averaged around 4-7 meters. Its name means “flat wrist,” alluding to the flippers, although it hardly distinguishes them from other mosasaurs in this regard. What did make them stand out from the other mosasaurs was a relatively shorter snout with eyes that faced more forward, so it probably had better stereoscopic vision, that is, it had better depth perception than most others of its kind. This may be why it had a shorter snout, to prevent the snout from blocking its field of view. Like other mosasaurs, Platecarpus had two rows of teeth on its palatine bones, forming the roof of its mouth. This arrangement actually isn’t all that unusual in lizards and snakes, it is really common in fish. The teeth (all of them, not just the palatal teeth) were pointed and conical, although not as sharp as some of its kin, indicating it went after small, soft prey, like small fish and soft invertebrates like squid or perhaps even jellyfish. They could have gone after larger prey like crocodilians do, but unlike crocodilians which have a strong skull capable of withstanding the forces of ripping a prey item apart, Platecarpus had a much weaker skull which would likely not have stood up to the stresses of the crocodilian death roll (this is when they grab a limb and spin until the limb is ripped off, the moral of the story is of course, never dance with a gator). The overall shape of Platecarpus is stockier than most mosasaurs. This would have had the effect of decreasing surface area relative to body weight, which could have increased its metabolism by holding in heat better.

KUVP1001. Mike Everhart. www.oceansofkansas.com

KUVP1001. Mike Everhart. http://www.oceansofkansas.com

One of the things that makes Platecarpus as a genus so interesting is the fossils that have been found with soft tissue preservation. In one, along with parts of the skin, parts of the trachea (windpipe) were preserved. Originally, they were interpreted as part of a dorsal fin, thus all the early pictures of mosasaurs with fins along their backs. However, it was quickly discovered what the traces really were. To his credit, Williston, the scientist who had reported in 1899 the traces as a dorsal fins was the one who published another short paper three years later saying he had made a mistake and the fossil really showed the cartilaginous rings found in trachea. The tracheal rings have also been interpreted as showing the branching point between the two lungs, which is important because it answered a question about their origins. Every researcher agrees that mosasaurs are lepidosaurs, the group including lizards and snakes, but what wasn’t known was whether or not mosasaurs were derived from aquatic lizards or from snakes. The discovery of a trachea showing two lungs confirms the origin within lizards (snakes only have one lung). It may still be that snakes evolved from mosasaurs, but that is not very likely.

The other piece of soft tissue that has been found is the outline of the tail showing a lobe on the tail forming a very shark-like tail. Until this time, many people had thought the mosasaur swam with an eel-like motion, but the tail and the deep caudal fins indicate a much faster shark-like swimming motion. This in turn has caused people to reevaluate the view they were slow ambush predators, supporting a more active predatory forager. Whether or not other mosasaurs had this fin is currently unclear, so there may have been specializations within this group not seen in the larger mosasaur family. Another such example is the discovery of what has been interpreted as thicker eardrums, which may have allowed them to dive to deeper depths.

Tail fluke preserved around skeleton. Credit: (top) Photograph (by Johan Lindgren), (centre) sketch indicating the bones and skin structures preserved (by Johan Lindgren), and (bottom) life reconstruction (by Stefan Sølberg) of Prognathodon sp.

Tail fluke preserved around skeleton. Credit: (top) Photograph (by Johan Lindgren), (centre) sketch indicating the bones and skin structures preserved (by Johan Lindgren), and (bottom) life reconstruction (by Stefan Sølberg) of Prognathodon sp.

The southwestern corner of Arkansas was at the edge of the Late Cretaceous Western Interior Seaway, so we have several fossils of them in places like Clark, Hempstead and Howard counties, although you can find them all over the world in the right type of rocks. You can find them in the Brownstone and Marlbrook Marl Formations. These formations are indicative of warm, shallow seas, much like the Bahamas today, which considering the locations, shouldn’t come as too much of a surprise to people. If you were taking a nice vacation on the warm Cretaceous beaches 80-85 million years ago, you might have tried fleeing into the water to avoid the dinosaurs on the beach, but you would have been no safer in the water.

I would like to thank Rachel Moore, who supplied a lot of the research involved in putting this post together.

Fossil Friday

It’s Friday, time for the answer to Monday’s mystery fossil. Were you able to identify it?

enchodusoceansofkansasThese fossils are from a fish called Enchodus, the “saber-fanged herring.” Teeth of Enchodus are commonly found in the Cretaceous-aged rocks in southwestern Arkansas, especially near Malvern and Arkadelphia in the Arkadelphia and Marlbrook Marl Formations, up into the Paleocene rocks of the Midway Group a bit farther north. In other places you can even find them in rocks of Eocene age, although you will have much better luck in the Cretaceous rocks. At this time, southern Arkansas was shallow to coastal marine. Go to the Bahamas, imagine Enchodus, mosasaurs, plesiosaurs, and plenty of sharks in the water around the islands and you would have a good picture of the landscape back then. They were abundant at the end of the Mesozoic Era and survived the asteroid impact that rang the death knell for many animals, including the non-avian dinosaurs. But they never regained their prominence as a key member of the marine ecosystem, eventually dying out completely in the Eocene sometime around 40 million years ago (the Eocene lasted from 55 to 34 million years ago).

2008-11005%20AncientSeasMural_for_NPS_1200

The fish reached sizes over 1.5 meters, which makes them on the large side, but not really big, considering there were mosasaurs in the same waters that surpassed 10 meters. Still, with fangs longer than 5 cm, they would not have been fun to tangle with. They were clearly effective predators on smaller fish and possibly soft animals like squid. At the same time, fossils have been found showing they were themselves prey for larger predators, such as sharks, the above-mentioned mosasaurs, plesiosaurs, and even flightless seabirds such as Baptornis. Baptornis was a toothed, predatory bird, but as it only reached 1 meter or so, it would have only been able to hunt young Enchodus. So like many of us today, Baptornis was always up for a good fish fry.

Hesperornis, a larger version of Baptornis, and a few Enchodus feeding on some herring-type fish. Picture by Craig Dylke.

Hesperornis, a larger version of Baptornis, and a few Enchodus feeding on some herring-type fish. Picture by Craig Dylke.

Enchodus is often called the “saber-fanged herring,” although it is unrelated to herrings. So what then was it? Herrings are what is known as forage fish, meaning they are mostly prey items of larger fish and other animals. Most of the fish called herrings are in the family Clupeidae in the groups Clupeiformes, which includes such well-known fish as sardines and anchovies. Enchodus, on the other hand, has been placed into the group Salmoniformes, which includes trout, char, and of course, salmon. When one typically thinks of trout and salmon, one doesn’t think of bait fish, they think of the fish that eat the bait fish. Thus, Enchodus would better better described as a fanged salmon (they were a bit large to call them fanged trout).

 

 

Fossil Friday

It has been a strange week, what with trying to catch up from the holidays and all. So this post will be brief. On Monday, I posted this picture of a commonly found fossil in Arkansas, provided you look in the right places. Here were the clues.exogyra

Clue 1: It’s from the Cretaceous.

Clue 2: It’s modern day relatives are widely considered a delicacy.

Clue 3: This is no wilting lily. This creature is big and bold. It shows how twisted it is on the outside for all the world to see. Dude, that’s heavy.

Were you able to figure it out?

So for the final reveal:  Exogyra ponderosa. Allie Valtakis was able to figure out it was a mollusc, specifically a bivalve (clam), in the Order Ostreoida, Family Gryphaeidae. While mosasaurs swam the oceans and dinosaurs walked the shores, these Late Cretaceous oysters made huge oyster beds throughout the coastal waters. Like all oysters, they were filter-feeders, collecting microscopic particles of food from the water. You can find them in south-central Arkansas within several rock units, but most particularly in the Marlbrook Marl, a limy mudstone. They are known for their large, heavy, rough bottom shell with a curled, hornlike part near the hinge. The top shell is much smaller and flatter, but still a good size, something like a cap on a coffee cup, if your coffee cup was kind of bowl-shaped. They are sometimes called Devil’s toenails, but that name usually refers to a different clam called Gryphaea, an oyster that is also in the Family Gryphaeidae, but a different subfamily. If you look under a microscope at the shell, you may notice that it is very porous, giving the Family the nickname of foam or honeycomb oysters.  Some are still alive today, such as Hyotissa hyotis, the giant honeycomb oyster

E. ponderosa was one of the earliest clams of this genus that was named, by Ferdinand Roemer in 1852, a German lawyer who gave up law to study geology in Texas, thus his title as the Father of the Geology of Texas.  You can fossils of them from Texas to New Jersey and Delaware, south through Mexico and Peru.

Until next time, as Dr. Scott The Paleontologist would say, ‘Get out there, get into nature, and make your own discoveries.”

Day 4 at SVP

http___vertpaleoDay 4 and the last day at SVP. After this, we will return to our regularly scheduled sorts of posts.Another day of talks and poster sessions, the last chance to meet friends and colleagues and discuss what you’ve heard and what people are doing. Although frankly, I think most people are tired and ready to go home by this point. Some people thrive on the highs of shared creativity and knowledge and find  the end of the meeting and going back to regular work depressing, I think the most common reaction is the feeling of being rejuvenated by the meeting, so that you can’t wait to go back and start developing the new ideas created at the meeting, the chance to put those creative juices to work before the distractions of everyday life dry them up.

A lot of people don’t like having their talks on the last day. People are going home, they are tired, their attention flags, but this meeting showed a strong turnout for the last set of talks. The symposium scheduled for today was “Patterns from the poles: biodiversity and paleoecology of high latitude fossil vertebrates,” which I, at least, found interesting and worth attending. I didn’t attend too many of the talks though, because there was also a session on the evolution of early birds, which I found even more interesting, as well as a session on mammals, which had several talks discussing how different mammal groups adapted to climate change in the past. Several talks introduced new fossils and what they contributed to our knowledge of evolution within those groups, such as a new Devonian fish from Siberia, the first pterosaur from Antarctica, a new sauropodomorph (early versions of animals that would  become sauropods, the oldest mammal from Antarctic and a new Arctic camel, new birds, seals, sirens, dolphins, and whales. All in all, good reasons to stick around.

Anchiornis_martyniuk, wikimedia

Anchiornis_martyniuk, wikimedia

Rui Pei reported on a new specimen of Anchiornis, the first animal in which fossil evidence in the feathers was used to determine coloration. Anchiornis lived 10 million years before Archaeopteryx and there has been some debate about whether it was a true bird or still a non-avian dinosaur. Pei’s analysis of the new specimen indicated that Anchiornis was a troodontid, so not quite yet a  bird. This is another great example that the transition between birds and other dinosaurs is so well documented that the line is an arbitrary classification with no biological relevance. Speaking of feather colors, William Gearty found new ways to study the melanosomes in the feathers providing colors, finding that, in addition to color, he could tell color gradients as well. he also concluded that melanosomes stiffened the feathers, making them more resistant to wear, but also carried more bacteria, thus representing an additional resource cost for the animals (some of this work can be found online at PLOS One).. Justin Hall found that feather asymmetry, long thought to be important for flight, turned out not to have the aerodynamic significance we thought, as it didn’t really affect the ability to fly.  Ashley Heers found trade-offs in locomotor ability: the more investment in wings, the less was put into the legs, and this trade-off could change as the bird grew so that chicks may emphasize the wings or legs while the adults emphasized the other.

Cryolophosaurus, Royal Ontario Museum. Wikimedia.

Cryolophosaurus, Royal Ontario Museum. Wikimedia.

Several studies showed the difficulties inherent in paleoecology interpretation. Peter Makovicky found that the horned ceratopsids showed different growth rates between northern and southern populations, the duck-billed ornithopods did not, and the carnivorous theropod Cryolophosaurus showed different growth rates in different areas of the same body in the northern individuals, but not in the southern individuals. According to Bergman’s rule, we should expect to see animals get bigger and stockier the farther north they are found. Anthony Fiorillo found that the small troodontids followed the rule, but northern individuals of the large tyrannosaurs were only 40% the size of the southern ones. In this case, it is likely that resource supply kept the tyrannosaurs smaller. Patrick Druckenmiller reported on a diverse Arctic dinosaur fauna including toodontids, dromaeosaurs, thescelosaurs, hadrosaurs, pachycephalosaurs, and tyrannosaurs, despite mean annual temperatures near freezing. While similar to southern forms, all the species were different, indicating a discrete, provincial ecosystem. John Tarduno argued that the presence of champsosaurs (a type of early crocodylian) and turtles indicated the weather was too warm for ice to be present even during winter, but as proven by an earlier talk, we know this is incorrect (a great example of science correcting itself). He proposed volcanism forming a series of shallow, freshwater connections between North America and Asia during the latest Cretaceous allowing interchange between the continents, which will need more study to determine if that proposal is true. Judd Case found that even though modern fish fauna show a drop in diversity with lower temperatures, thisi was not the case in the Cretaceous. As the temperature in the Cretaceous dropped 8-10 C in the Antarctic oceans, the fish didn’t really change, although marine reptiles increased in diversity while the ammonite diversity dropped.

Figure from Fletcher et al. 2010, showing FEA analysis, indicating stress points near the joint.

Figure from Fletcher et al. 2010, showing FEA analysis, indicating stress points near the joint.

Rodrigo Figueiredo  presenting evidence that predators who pursue their prey (as opposed to ambush predators  attacking large prey and those that pounce on smaller prey) may not have evolved to go after herbivores, but to prey on the pounce predators themselves, much like wolves will sometimes hunt foxes and weasels. Michael Greshko presented a study finding that herbivores known as generalists (able to eat a wide variety of plants) mostly consist of different individual specialists who eat only a narrow range of foods. This is rather like why a pizza buffet needs to stock a lot of different types of pizza even though any particular customer may only eat one or two different types. Speaking of eating, Emily Rayfield gave a possible answer to why mammals reduced the number of bones in the mandible to just one, as opposed to having several bones in the lower jaw like other groups of animals. Using Finite Element Analysis, an engineering method designed to test mechanical strength of materials, found that the one bone provided a stronger bite while reducing stress. Alistair Evans used a program called GEOMAGIC to study tooth shape in early mammals and predict what tooth shape should be like to help sort out all the isolated teeth for which we have no idea what they belong to. in this way, he is making predictions of fossils that have not yet been discovered.

Gephi.org BON graph

Gephi.org BON graph

In addition to the software programs mentioned previously, several others were mentioned in talks this day. Most biogeography methods these days are done using phylogenetic methods to help inform how animals spread out across the globe, but Chris Sidor presented Bipartite Occurrence Networks (BON), using Gephi to visualize the patterns, which just uses locality connectedness and found that therapsids (proto-mammals, aka mammal-like repties) were pretty widespread and cosmopolitan before the Permian extinction event, but became much more provincial and limited in range afterwards. Paul Upchurch used TREEFITTER to map pterosaur biogeography, finding support for sympatry (speciation within the same region) with an origin in eastern Asia. Diego Pol used Ancestral Area Reconstruction methods to conclude that dinosaurs probably originated in South America, along with most, but not all, mammals, but crocodylamorphs originated in China. Graeme Lloyd used GEIGER to study evolutionary rates and Akinobu Watanabe used PERDA (Polymorphic Entry replacement Data Analysis, a script running in TNT, a phylogenetics analysis program) to simulate poor sampling of phylogenetic data, finding that if a trait, or character, has multiple possibilities within a single species, it seriously messes up results unless multiple individuals covering all the possibilities are included in the analysis. John Alroy found that no current method is very good for finding the first appearance of taxa, but Bayes Theorem methods, such as used in MrBayes, produce better estimates of extinction times.

Figure from Sansom and Willis 2013 showing fossilization study results.

Figure from Sansom and Willis 2013 showing fossilization study results.

The last two talks I would like to mention are from Robert Sansom and David Grossnickle. Sansom found that loss of soft tissue characteristics resulted in changes in cladograms drawn from the data for vertebrates, but not for invertebrates. In other words, if one only looked at hard parts, the evolutionary relationships changed, and more often than not, made the animal appear to be more ancestral than it really was. This occurred even if the characters were recorded as unknowns and not simply listed as absent. Grossnickle looked at morphological disparity in Mesozoic mammals, i.e. the diversity of body form. What he found was that most Mesozoic mammals were carnivorous/omnivorous, with a low level of diversity which gradually increased until the middle Cretaceous. At some point in there, they hit a botttleneck. Their diversity crashed and, while it did start going up again,never reached the previous diversity levels until after the K-T extinction event. What is interesting about this is that pretty much everything else was diversifying, while mammmals were not. Another interesting thing about this is that according to molecular data, mammals were diversifying, so the apparent diversification did not show up as morphological diversity.

This is the end of my discussion about the science presented at SVP. There were so many more talks and posters that I did not mention and i make no claim that the ones I mentioned are even the best or most important, nor are they even all the ones I attended and learned something from, but it would take me until the next meeting to discuss all of them. The point is that meetings like this are incredibly fascinating places to see what  is going on in science right now. Anyone who thinks science is a bunch of stale facts in textbooks or that scientists even pretend to have all the answers is seriously mistaken. The search for truth is asymptotic, you can get ever closer to a totally clear understanding of reality, but you will never reach it. Science is all about going over the data, tossing out ideas that don’t succeed and developing ones that do, with each step opening up new avenues of exploration.

Steven Spielberg on set of Jurassic park. Spielbergfancluc.com

Steven Spielberg on set of Jurassic park. Spielbergfancluc.com

I will end this discussion with the awards banquet held on the evening of the last day. During this banquet, we are told how much the auction collected to support the society, important news, memorials for those we lost recently, and people are recognized for their hard work and contributions to the field of vertebrate paleontology. Students are awarded their prizes and scholarships they have won, artists are awarded for best art in different categories, and people are recognized for outstanding careers that have progressed the field. This year, one of the biggest awards went not to a scientist, but to a science advocate. Perhaps because the meeting took place in Los Angeles, special recognition went to Steven Spielberg, for the money he has donated to the Jurassic Foundation and other places to support paleontology research and education and for the Jurassic Park movies, which brought paleontology to the center of the public eye and has inspired many to enter the field and make their own contributions. Officially, the meeting ended here. There was an after-hours celebration, which is always fun from what I hear, but I was beat and had a plane to catch early in the morning, so I called it a day. Until next year!