Digging on the Net: Birds of Paradise

A few weeks ago, I found myself walking down my driveway after a long day of school. I turned to my left and saw the mail had come in, so I decided to grab it and save my parents some trouble. However, I noticed I got a new edition of National Geographic magazine in the mail, and one of the sections listed on the cover said something about the Birds of Paradise, scientifically known as the Paradisaeidae, and are best known for their spectacular and diverse plumage in males. I entered my house, dropped all my things on the way up to my room, and quickly indulged into the world of these spectacular and diverse birds.

It turned out that after 8 years of looking and studying Birds of Paradise, photographer Tim Laman and Cornell University ornithologist Ed Scholes were able to be able to document and photograph every living member of the family, including the never-before photographed and rarely ever witnessed Buff-Tailed Sicklebill. Their discoveries and footage include never-before seen views of these animals, and completely unexpected realizations about their mating behaviors. I wasn't going to make a post about this, but a recent National Geographic Live! interview has given me a good chance to show you all just how spectacular these creatures are:

I know there's been a lot of bird-related things on this blog recently, but expect it, since birds are the living representatives of Dinosaurs, and in my opinion, we should be basing Dinosaur behavior off them. In my opinion, if a bird practices some type of behavior, then Dinosaurs probably would've done similar, of not the same behavior. And yes, that includes the possibility that male T-rex were dancing around, clearing areas on forest floors in order to make them seem sexier to females of their species.

Yes, I know, I'm working on the Neosuchian post. I'm just stuck on this one part and currently looking for the information to refresh my memory on it. It'll be within the month, but expect some shorter posts in the meantime.

Happy Thanksgiving

Two male Wild Turkeys performing their characteristic "strutting" behavior.

For this quick post, I'd like to say Happy Thanksgiving to all my American followers here, and talk briefly about one of America's National emblems, the Wild Turkey (Meleagris gallopavo). Often taken for granted by us humans, and often described as very dumb birds, Wild Turkeys are greatly misunderstood animals, which encourages me to devote a few paragraphs here to discussing them on what should be considered their own national holiday.

The Turkey is the largest living member of the Galliformes, or gamebirds, a group of about 290 species of mostly terrestrial birds that have compact bodies, small heads, short beaks, and high-wing loadings. Galliforme young are precocial, which means that they are able to walk within hours of birth, and in the case of Megapodes (large gamebirds from Australia and surrounding areas of land) their young are superprecocial, and are able to fly within their first day out of the egg.

Gamebirds as a whole are a very successful group; they've colonized every continent except Antarctica, and are found everywhere from tropical rain forests to frozen tundra. They are well known for often showing extreme forms of sexual dimorphism, and males are often larger than females and have almost excessive amounts of display plumage, which reaches its most extreme in peacocks and some pheasants. In some species of gamebird, males have an enlarged spur on their hind feet that can be used in both territorial battles, and as a defense against predators. (I think that a similar function might have encouraged the evolution of enlarged claws in dromeosaurids, iguanodontians, and prosauropods, although I doubt sauropods used their thumb claws in this way, since they seem more likely to have been used in foraging, according to recent studies.)


Male Turkey displaying coloration of 
his head and waddles

Turkeys in particular are very interesting gamebirds if you've seen them before. I've seen them myself on a few occasions, and they look and act like very proud animals. The males even have a behavior called "strutting" where they walk around displaying to both females and other males while dragging their wings, puffing up their tail and chest feathers, and pulling in their head. During this behavior, males have been known to change the color of their head based on how they're feeling, similar to what cassowaries and chameleons do, with blue heads signaling excitement, and red heads signaling aggression. They can also engorge the skin and waddles around their head with blood, causing them to swell up almost to the point where the eyes and beak are concealed.

The bare, blood-filled skin and thick body feathers in males doesn't come without consequences. Some studies has shown that overheating is a problem at times, and males will often rest in the shade for hours at a time, and have been known to pant on hot days like dogs and crocodiles do. Females, with less body plumage and more plumage on the head when compared to males, don't have as much of a problem, and are free to forage for food most of the day without resting. The diet of a Turkey includes grain, leaves (including conifer needles), nuts, seeds, berries, roots and insects. They have also been observed eating small vertebrates, including frogs, lizards, and even snakes.


Female Turkey with Chicks

As with almost all gamebirds, males play no role in parental care, and are polygamous, mating with multiple females in a season. The female is thus left entirely responsible for taking care of the offspring, which can sometimes be up to 14 juveniles. The eggs are layed about one day apart in a shallow dirt impression, and they all hatch after about 28 days and leave the nest within their first 24 hours. The female will then watch over the young for the next 8-10 months until they are large enough to take care of themselves. If confronted by a predator, turkeys prefer to run rather than fly, using their long, athletic legs to escape danger, although if forced to they have been known to be quite agile fliers, and will sometimes roost in trees to sleep in relative safety.

Native Americans have long relied on turkeys, and they were considered a vital food source for many eastern tribes. During the first Thanksgiving, the governor of Plymouth sent out four men to catch turkeys for the big feast, and came back with enough turkeys to last them a week. However, turkeys weren't the only animals being served. Deer, geese, ducks, swans, passenger pigeon, fish, eels, shellfish, mussels, clams, and lobster were also on the menu. After the first Thanksgiving, British trading ships brought the animals back to Europe as food. They were forced to travel through Constantinople in Turkey before reaching other countries. People then associated the birds with that nation, which is where their name comes from.

Sadly, it seems that food is one of the only things Turkeys are remembered for in history, but one famous historical figure thought highly of Turkeys. Benjamin Franklin wanted the Turkey to be the national bird of the United States rather than the Bald Eagle. He believed the Turkey to be a more noble and proud bird than the Bald Eagle, as he had witnessed Bald Eagles stealing food from other smaller birds, and basically bullying them into submission (many Raptors are known do this). Many disagreed with him, however, preferring the stronger and more powerful Bald Eagle over what they viewed as the comical turkey. I'm happy with the Bald Eagle as America's national bird, but I'm also glad that Franklin looked past the non-traditional beauty of the Turkey and saw an attractive and proud creature behind that plump body.

I wish you all a Happy Thanksgiving, and hope you will respect the animal who gave their life for your meal today. As for me, I'm a vegetarian, so I'll be staying away from these birds today and hope those that did not end up on your plates will get fed just as well as I will today. What will I eat if not Turkey, you ask? Cauliflower bisque, herb-crusted tofu with mushroom gravy, chestnut sage stuffing, cranberry sauce, green bean casserole, candied yams, and delicious pumpkin pie are all on the menu tonight. Whatever is on your menu tonight, enjoy the holiday with your family and friends! And expect a lot of posts next month, since I'm going to be off for the Holidays.

OH MY GERSH! Where's RaptorX?

 



A Common Potoo having a panic attack.



Hey everyone, bet you were all expecting a Croc post last week. Sadly I haven't been able to get on it yet, I've been busy working on some other things, some of which I'd like to tell you all about.
The first news is that I'm writing an article for a new online magazine, called AncientPlanet Online Journal. The magazine looks nice and I''m excited that some of my articles will be appearing in it. It's every two months though and I'm trying to balance out getting info for the articles, and getting my school work done. I also have a YouTube account now if anyone is interested in talking to me on there. I might also start making videos, but I'm not sure yet, as it'll make me even more busy than I am now.

As for Crocs, it might be a while before I get to writing that post. In the meantime you might want to go over to Darren Naish's blog Tetrapod Zoology. He recently wrote a few articles on Neosuchid crocodiles, and even though I know a lot about these things, I still probably can't explain them the same way an actual scientist can.

As for the meme, it's made by yours truly. The image is of a Common Potoo, which is a type of nocturnal bird from South America related to nightjars, swifts, and hummingbirds. It's an insect eater and uses its enormous mouth to gulp down moths and other insects in flight, and is famous for its amazing camouflage capabilities, being able to mimic a broken tree stump almost perfectly. It also is known for the strange call it emits, which sounds almost like a human saying "poor me, all alone." Here's some less comical images of Potoos:

Head profile of a Common Potoo. The huge mouth has tiny bristles inside which help trap any insects that get caught.

This Common Potoo was curious of the camera when this photo was taken. A Potoo's large yellow eyes are used to help them see in the dark, but give them somewhat of a bug-eyed look.

Common Potoo hiding in plain site. It might not seem wise to close its eyes when hiding from predators, but Potoos have small notches in their eyelid which allow them to see even when their eyes are closed.

Common Potoo showing its young the art of hiding. Potoos and their relatives have such good camouflage that they can fledge chicks directly on a bear tree branch, and sometimes even open ground without ever being spotted by a predator.



Dino-Eating Crocs Part 2: Success of the Notosuchia

A depiction of Baurusuchus eating a turtle. These crocodilians were taking up the roles of Dinosaurs near the end of the Cretaceous, and were proving to be deadly adversaries.

When you think of the paleoecology of the Cretaceous period, normally you think of dinosaurs filling up all the niches available, as this period was the height of their success. But this couldn't be further from the truth. During the Cretaceous, many forms of animals took up the intermediate roles between the folds of nature, and while some think these areas were ruled by mammals, that's actually not the case either. It seems that these niches were mostly filled by a group of crocodiles, known as the Notosuchia.

The Notosuchia are a well known group to scientists. We first found their bones more than a hundred years ago, but they remain mysterious and unknown to the public. Their fossils have been unearthed in South America, Africa, Europe, and even as far as East Asia. They were fully terrestrial, as shown by their un-flattened tails, level nostrils and eyes, and long legs, and ranged in size and shape from small little animals no larger than a housecat, to fairly large animals that could've given theropods a run for their livelihood. Their strange teeth and dietary preferences have made them famous in the paleontological world.

The best description of their teeth is that they're mammal-like, although they really have no close resemblance to any animal living or extinct, and were probably more competitive with mammals than dinosaurs ever were, as they occupied the same niches. Some even seem to have given up a diet of meat and evolved towards herbivory, such as Chimaerasuchus from China and Malawisuchus from Malawi. Others were opportunistic omnivores, such as Notosuchus from Brazil and Araripesuchus from all over the Southern Hemisphere. The latter's genus also lasted from 125 - 65 mya, meaning it survived for more than 60 million years, longer than most other land vertebrates from the Mesozoic and certainly longer than any dinosaur genus I know of.



Chimaerasuchus, a 6ft herbivorous croc from Early Cretaceous China.
The location where this fossil was found is the farthest
the group ever got from the Equator.

There were many bizarre members of the Notosuchia, but it's interesting to note that many resemble living mammals. Armadillosuchus has probably the most prominent name of the group, resembling a living Armadillo, and having armor carapaces along its back for defense. Mariliasuchus looked profoundly like a gopher or other burrowing mammal, and has actually been found lying within possible burrows along with associated eggs. Notosuchus had fleshy lips, and might have had either a hog-like snout, or possibly even a trunk like a tapir. Some looked like cats, such as Pakasuchus, which has large eyes and a similar body form to modern felines.Their were even alien-looking animals like Yacarerani, which had a bizarre dentition that looked a lot like a rat or other rodent. All these similarities with mammals, along with the fact that they had upright legs and likely exhibited active lifestyles, has suggested to some researchers that these crocodilians were endothermic, but an examination of this idea has yet to be performed.

These animals were definitely filling up mammal niches, and it's probably due to this group, not the dinosaurs, that most mammals in the Southern Hemisphere stayed small. However, in many places that these small crocs roamed, we're now finding that herbivorous dinosaurs were absent, suggesting that they were also taking up dinosaur roles in the environment. Take South America for example, almost all kinds of hypsolophodont from the northern side of the continent were gone by the Late Cretaceous, but in their place we found these little animals scurrying around. The same is also true of Late Cretaceous Madagascar, we've yet to find one Ornithopod or Ceratopsian in the environment, their niches completely filled with crocs instead. The occurrence of Chimaerasuchus in China also roughly coincides with the disappearance of many small ornithopods in that region. However, the disappearance of Chimaerasuchus also roughly coincides with the diversification of many plant-eating theropods, possibly meaning that once these crocs left the region, theropods filled the niches that both groups had held previously.

The most competitive, and probably my favorite members of the group were the sebecosuchia, which occupied not the niches of small ornithopods and mammals, but were predators taking up the roles that small- to mid-sized theropods had. Along with the mammal-like teeth of other members of the Notosuchia, members of the sebecosuchia also evolved theropod-like teeth, and in some members like Stratiotosuchus, canine-like teeth evolved. They evolved stiff backbones and longer legs, better for actively running after prey, and resembled giant reptilian dogs. These were also the largest members of the Notosuchia, with some species reaching about 15-20ft.

I imagine these animals to be ambush predators, lying in wait along game trails, waiting for an unsuspecting dinosaur to wander by, and possibly even pursuing the animal for a short distance at high speeds until they tired. This behavior, along with their ecological niche, would've put them right at the same level as large theropods, and would've been just as dangerous to the local herbivore populations. In many fossil sites around the world, these animals seem to have even replaced theropods as the top predators as time went on.

A Stratiosuchus preying on some kind of Titanosaur.
Image by Maurílio Oliveira.

This is most strikingly the case in a formation called the Adamantina Formation, which is a layer of rock in Brazil that dates back from 90-83mya. This could be called the Lost Land of the Crocodiles, and the entire fauna is dominated by these animals, with more than 15 species present and virtually no dinosaurs or mammals represented. Instead of mid-sized theropods we see Baurusuchus, Campinasuchus, and Stratiotosuchus filling these roles; in place of ornithomimids and oviraptors, we instead have pig-like animals like Armadillosuchus and Mariliasuchus; and in place of ornithopods and mammals, we have a whole dynasty of herbivorous species present in the fossil layers. The only dinosaurs present are Sauropods, which seem to have been the only dinosaur group these animals couldn't match in ecological role. However, I've recently heard of some unidentified theropod material that's come from the formation, and a fossil Barusuchid apparently has some theropod bite marks preserved on its bones, which might indicate that these dinosaurs were present. But still, the majority of animals in the formation were Notosuchids, and it seems that they took control of this specific region. Why exactly? We may never know.

At the end of the Cretaceous, after all the major dinosaur faunas went extinct, leaving only birds and mammals to take their roles, these crocs didn't go back into the water to join their Neosuchid kin. In fact, the discovery of numerous members of the sebecidae found in Cenozoic rocks proves that these animals survived the disaster at the end of the Cretaceous, and were still as big, powerful, and competitive as ever, and ready to try and take up the roles as predators of mammals. In South America scientists have found the sebecids Sebecus, Bretesuchus, Langstonia, and Lorosuchus in the same fossil rocks as members of the Phorusrhacidae and Sparassodonta, which we believed for a long time were the only large predators on the continent. Not just that, but Bergisuchus from Germany and Eremosuchus from Algeria also shows that they survived in places outside of South America.

Seeing how the group was comprised of large, active, possibly even warm-blooded predators, how did they survive the K-T extinction event? Well, apparently one articulated Baurusuchus specimen suggests the possibility that even these large animals dug burrows, possibly in order to hibernate during tough times as seen in modern day Nile Crocodiles. This behavior could have helped them survive the extinction 65mya that wiped out the dinosaurs, and allowed them to live on through the Cenozoic. But then, why aren't they around nowadays?

There are many mysteries surrounding the extinction of the Notosuchids, however the extinction does coincide with a sharp decrease in global temperatures, known as the mid-Miocene disruption, which might have spelled doom for a group of crocs without any form of insulation to keep them warm. Still, these animals must have been magnificent to see in their glory, and it certainly proves that crocs were definitely not lying down on their lazy bellies by the water's edge during much of their evolution. They were active, powerful, and quite capable of giving even the "Terrible Lizards" a good run when they were alive.
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There we go, part one of the Crocs done, and I'll be posting part two within a few weeks, so I'll see you all then!

Dino-Eating Crocs Part 1: Introduction to a Croc-Filled World

The notosuchid Baurusuchus, a ten-foot crocodilian which evolved a canine-like body, mammal-like teeth, and was completely terrestrial. Oh, and it was out-competing theropods in their ecological role of top predator in Cretaceous ecosystems.
 No big deal, right?

A few months ago, I was lucky enough to purchase myself the new paleontological book The Complete Dinosaur Second Edition, which I must say, has to be one of the best books about dinosaurs I've read in a long time, and I recommend it to any dinosaur enthusiast like myself. The book is made up of numerous sections and chapters on different dinosaur topics and debates, and leading experts from around the world have sent their research and findings to be presented in the book. Thomas Holtz, one of the world's leading experts on theropods, writes the entire theropod section of the book. Jack Horner, who was the first person to find dinosaur eggs in the Western Hemisphere, helps to write the section on dinosaur eggs and nests. And Darren Naish, who is an expert on fossil vertebrates (specifically birds), writes the section on both living and extinct groups of birds. I was actually very pleased with the bird section, since it's about time we got some living dinosaurs in a dinosaur book.


Ann Darrow and the fictional crocodile Foetodon from Peter Jackson's King Kong
Amazingly, there was a fossil crocodilian that resembles the latter in size and form.

Anyway, I've been spending the last few months reading this very in-depth book, reading through sections by Kristina Curry Rogers, Peter Makovicy, and Gregory S. Paul just to name a few. Finally I came across a section titled Non-Dinosaurian Vertebrates written by Nicholas C. Fraser, whom you might know from his recent book In the Shadow of the Dinosaurs (which I have yet to read). The section reviewed the many fossil vertebrates that lived alongside the dinosaurs, such as plesiosaurs, pterosaurs, mammals, and numerous other fossil groups from the Mesozoic. The section was strangely short, only about 26 pages long compared to the 40 pages some of the other paleontologists wrote (not including references). Still, I was pleased with the chapter, and it taught me many things that I didn't know about non-archosaurian reptiles from the age. So why am I bringing this up exactly? Simple, I was extremely disappointed at the crocodile section of the chapter.



The recently described Kaprosuchus (or Boar Croc) from North Africa, one of
Paul Sereno's newly discovered fossil crocs from the region. 

The section had very little content on the fossil crocodilians during the Mesozoic; less than three paragraphs are dedicated to the entire evolution of the group. And what is covered in the section is largely already known by most dino-nerds like myself, such as the already well-known super crocs of the age and the sea-going metriorhynchids. It's somewhat ironic because Fraser even states at the beginning that crocodiles were as diverse as dinosaurs and pterosaurs, yet he devotes three whole pages on the evolution and diversification of the pterosauria.

This is not meant by any means to be an attack on Fraser, as I said I absolutely loved the section. I'm just disappointed that he devoted such little space to the crocodilians when there is so much to cover, especially since fossil crocs are finally getting some much-deserved media attention for their quirkiness.


Notosuchus was a terrestrial crocodile that lived in South America during the Late Cretaceous.

You might call it the Mesozoic equivalent of a pig, with its hog-like snout and fleshy lips.

The crocodilian group as a whole, by which I mean the Metasuchia, was actually so diverse that I can't do the group justice in a single post, so this will be played out in two separate posts I'm working on. The first will be on the now-extinct, but extremely diverse group called the Notosuchids, which includes many mammal-like members that resemble everything from armadillos to house cats. In fact, they were so successful that they took over all kinds of dinosaur habitat and ruled whole regions where theropods and ornithopods once roamed. The second will be on the still living Neosuchia, which includes living crocodilians, the super-crocs of the Mesozoic, and some rather bizarre members, including some that seem almost Cetacean-like in anatomy and ecological role. They primarily avoided competition with dinosaurs and land animals, preferring an aquatic existence. However, there were certainly many exceptions to this rule.

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So the next few topics will likely be on these crocodilians. In fact, I've basically got the next few months of blogs planned out unless I get more requests. Along with crocodiles, I'm hoping to write about spinosaurid skulls, extinct giant birds, dinosaur footprints, and hopefully raptors. Also, since I happened to bring up The Complete Dinosaur Second Edition, I may do a review of it in the future. If a review would be of interest, let me know in the comments.  Until next time, stay sharp!

Ornithopod Biodiversity and Evolution

Requested by MrGorsh

Diversity of the Ornithopods

Ornithopods were a hugely successful group of herbivorous dinosaurs, ranging from a little larger than a house cat, to 50-foot giants like Shantungosaurus that rivaled sauropods in size. The key to their success was the ability to process plant matter more efficiently than other dinosaurs. While ankylosaurs and ceratopsians also possessed the ability to chew, it was only in ornithopods that advanced dental batteries and unique jaw joints evolved. This allowed them to dominate an environment filled with tough plants species that were evolving. Many people overlook ornithopods because they tend to seem less interesting than other "sexier" dinosaurs like T-rex and Triceratops, but their lifestyles, evolution, and anatomy are just as interesting as those of any other animal group. However, before I start, I will note that ornithopod evolution and classification is an extremely debatable subject, especially  since the group was historically a taxonomic wastebasket of bipedal herbivorous dinosaurs. So I'll try my best to explain the many theories surrounding their origins and evolution based on my own sources.

The most primitive ornithopods we know of are commonly called the "hypsilophodontids." Although considered a natural group in the past, many now consider the "hypsolophodontids" an unnatural group, and some genera are actually closer relatives of iguanodonts than other "hypsolophodonts" (this is why I'm putting quotations around their name). The earliest known "hypsolophodontids" appear in the fossil record during the Late Jurassic, like Othnielosaurus and Agilisaurus, and survived all the way up till the extinction event 65 million years ago, with species like Thescelosaurus and Orodromeus present. They lived on every continent and tended to all have a similar body plan; the majority were small, with short skulls, large eyes, short beaks, long stiff tails, and long legs with proportions evolved for running at high speeds. They likely used this speed  to escape from predators, since they were without any other noticeable defense. This makes me think of them as being very skittish animals, ready to use their high speed to run at any sign of danger, like rabbits or deer today.

Some odd members of this group include the Australian polar Leaellynasaura, which had a tail close to three times it's own body length, and owner of the most vertebrae of any ornithopod outside of hadrosaurs. It's also famous for its apparently large eyes, however, this was based on the discovery of a juvenile skull; adults actually have the same sized eyes as other "hypsolophodontids." Another member I personally find very interesting is the long-snouted Thescelosaurus, made famous by Willo, a dinosaur that was first thought to have its heart preserved. While this has now been shown to instead be a sand clump, it still has a very strange skeletal anatomy. Thescelosaurus has a very long, thin snout, very unlike the short snout of other "hypsolophodonts," and leg proportions that would've hindered running speed (a long femur, a short tibia, and a short metatarsus). Nobody quite knows how Theselosaurus lived, but one theory that I've found interesting in recent months is the idea that it might have lived like modern capybara, spending time in the water for protection (as suggested by its short legs and long skull, both adaptations for aquatic life) and coming out on land at night to feed. This theory hasn't been popularized yet, and many people haven't even heard of it, but I'm open-minded and certainly find it possible after looking through its anatomy.

Numerous discoveries from North America and Australia also suggest that these animals, like rabbits and some species of kangaroos, might have been burrowers, their large, robust shoulders and hands being used to excavate tunnels, and their self-sharpening beaks being used to help carve openings in the dirt. These animals also have a small bone, called the palpebral, over the eyes that would've supported skin that could shade the eyes. A similar bone has been found in modern day birds of prey, who use the bones to help prevent glare when spotting prey. But "hypsolophodontids" were predominantly herbivorous, at most the animals might eat some insects from time to time, but certainly not in need of any predatory "sunglasses." Instead, scientists have suggested that they were used to protect the eyes while digging, by keeping rocks and dirt from damaging the delicate structures. Some hypsolophodonts also have been found with large, bony plates on the ribs. These don't seem to be very good for protection, as they were extremely thin and fragile, not suited for predatory attacks. So far nobody can agree on the function of the plates, but some have suggested that they have something to do with the respiratory system.

Despite these animal's success, they still hadn't evolved the advanced ways of processing food found in later ornithopods, and while their chewing was still better than many ornithischians, it was primitive and needed work. Ornithopod feeding got more advanced with the evolution of iguanodonts, who took the already present chewing of "hypsolophodonts" and added to it. They developed a enlarged premaxila that lacks any teeth and a deep dentary with parallel dorsal and ventral margins. These simple modifications helped with food processing so well, that they quickly started to dominate the local fauna, and evolved into much larger sizes. They seemed to have evolved during the middle of the Jurassic, as suggested by a single femur known by the name Callovosaurus (this also suggests "hypsolophodonts might have appeared earlier in the fossil record).

Callovosaurus is thought to be a dryosaurid, the most primitive type of iguanodont and looked very similar to "hypsolophodonts" in appearance, with long legs, small heads, and big eyes; in fact, they probably lived very similar to them as well. After them quickly evolved the camptosaurids, which were larger, had more elongated skulls, and were more heavily built than dryosaurids. They were also the first group where a thumb claw is seen present, which in later iguanodonts became enormous (I'll discuss this more further down). From them quickly evolved more advanced members, like Iguanodon and Dollodon, which were the most successful animals of their day. Their decendants included advanced members of the hadrosauroids, but we'll get to them later.

Some species of iguandontians, however, seem to be a bit difficult to find a good place to fit onto this tree, most notable is the famous American genus Tenontosaurus. What used to be thought of as a hypsolophodont, is now thought to be a type of basal iguanodontian in its own group, but where it fits exactly on the tree is still a matter of research. Tenontosaurus' most noticeable feature is its extremely long, deep tail, which took up 2/3 of its total body length, and a short nasal ridge that could have been used for display. It's also famous for supposedly being attacked by a pack of Deinonychus, but some recent evidence suggests otherwise. Another very primitive group of iguanodonts are the rhabdodontidae, which were a group of late-surviving iguanodonts that lived in Europe during the late Cretaceous. Scientists always had a hard time trying to pin down the rhabodonts' evolutionary relationships, as they were originally considered ceratopsians, but we seem to have a much better idea about them now. They were also, notably, some of the weirdest of ornithopods, having enormous skulls and teeth compared to their body size, and to this day we still don't know what they used them for.

During the iguanodont's evolution, many groups evolved different ways of living, but what was most noticeable was that many iguanodonts seem to have evolved in similar ways to tyrannosaurs, with some species being extremely robust and others being very gracile in anatomy. These gracile and robust morphs, seemed to have evolved to avoid competition with each other. This is reflected in fossil finds — you will often see robust and gracile iguanodonts living side by side at the same fossil site, but it's rare to see two of the same type. One of the most gracile forms of an iguanodont yet found is the African Ouranosaurus, which is well known for its elongated vertebrae, and was likely able to run away from potential predators at very high speeds. On the opposite side of the spectrum, one of the most robust of all iguanodonts lived alongside Ouranosaurus in Africa, known as Lurdusaurus. Lurdusaurus was immensely stocky and robust, with an extremely wide hip and stomach, short arms and legs with wide toes, a short, thick tail, and powerful arms; it was the sumo-wrestler of ornithopods. Many scientists have compared it to ankylosaurs in terms of its massively wide hips and robust build, but why get this robust in the first place? Well, many scientists looking over Lurdusaurus' anatomy have suggested that it was the dinosaur equivalent of a hippo, using its huge girth to keep afloat in water.

Along with being quite possibly the most aquatic herbivorous dinosaur ever found, Lurdusaurus also has one of the largest hands of any ornithopod, equipped with one of the largest thumb spikes. The thumb spike of iguanodonts has always been thought of as a defensive weapon, and certainly they would use it if their life was at stake. However, gracile morph iguanodonts have tiny thumb spikes, not suited for protection against large predators, and wouldn't their speed be enough anyway? Not just that, but later hadrosaurs completely lost their thumb spikes, and Lurdusaurus still has one present despite the fact it would've caused stress on its bones if it reared up to use it on land. This has led many scientists to think that the thumb claw instead was used like the spurs on roosters, in territorial battles, and the enormous size of the claw and arm on Lurdusaurus suggests that these animals dealt serious damage to each other when fighting, bringing to mind, again, the modern hippo. Alternatively, some think it could have been used to break open large seeds, but then again, would you really need a thumb spike a foot long to break open a little seed?

Of course, when you think about ornithopods nowadays, you don't think of lumbering aquatic animals anymore; that's the old view. Many people instead think of the hadrosauroids, the last group of ornithopods to evolve. Hadrosauroids, during their reign, were the largest, most numerous, and most biologically successful group of ornithopods to evolve. In North America alone we have close to 60 species of hadrosauroids present in the fossil record, each with its own characteristic body shape and build. Along with that, they also just happened to have evolved the most successful way of processing food of any dinosaur. They were surely the pinnacle of the ornithichian's success.

The hadrosauroids were able to tweak the iguanodonts' feeding apparatus and make it even more efficent than it was, adding to it an elongated snout to allow a larger number of teeth in the jaws. The snout broadened at the tip, producing the characteristic duck-like shape, and allowing for a larger amount of food to be taken in. The jaw also started forming complex dental batteries so that when one tooth fell out, another immediately took its place. These newly evolved jaws were what made the hadrosaurs able to out-compete their more primitive iguanodontian ancestors, thus the majority of iguanodonts went extinct.

Hadrosauroids are separated into two groups, the hadrosaurinae (also known as saurolophinae) and the lambeosaurinae (however, there are members that seem more primitive than either group). The hadrosaurinae are characterized by their low, elongated skulls with large nasal openings and wide beaks for taking in large quantities of vegetation. Some of these dinosaurs include Edmontosaurus, who at the moment is one of the best known fossil hadrosaurs and lived alongside T-rex, Maiasaura, who is the first dinosaur in the western hemisphere for which we found eggs and could attribute a nest, Tethyshadros, a island-living hadrosaur that has some of the strangest anatomy I've seen on a dinosaur (I get headaches just thinking about this guy), and Shantungosaurus, the largest hadrosaur, largest ornithischian, and largest dinosaur outside of the sauropods. The other group, the lambeosaurinae, are characterized by shorter, taller skulls, with small nasal openings and less wide beaks for more selective feeding. They are also well known for their large nasal crests that extend high above the top of the head. Some of these species include Parasaurolophus, a rare dinosaur that lived throughout a number of localities in North America, Corythosaurus, which is one of the best known lambeosaurs, Tsintaosaurus, which is also known as the "Unicorn" dinosaur for its straight tubular crest, and finally, the recently discovered giant known as Magnapaulia, quite possibly the largest lambeosaur ever.

These animals make up the majority of the dinosaur fauna during the late Cretaceous, and have been found on every continent with the exception of Africa and Australia (although the former is probably due to lack of good sampling sites), but they were at their most diverse in North America, and for quite a while we didn't really know why. However, a study that came out a few months ago put forth a possible explanation. At the same time that we are seeing this boom in hadrosaur diversity, the Rocky Mountains were rising, and the giant inland sea that was present at the time cut the continent in half. This caused many hadrosaurs, ceratopsians, and tyrannosaurs to be isolated within valleys between mountain chains and the ocean, and would cause isolation within a population and accelerate the process of evolution, causing many different animal forms to appear, but would likely have low populations. We've connected the dots even more and found that, when the inland sea started to recede, and the Rockies started to decrease in size with more erosion, dinosaurs weren't isolated anymore. This caused the diversity of ornithopods to decrease, and instead you would have large populations of a few dinosaur types. Who knew hadrosaurs could tell us so much?

Based on the evidence of bone beds, trackways, and communal nesting sites we've uncovered, it has been interpreted that Hadrosaurs were very social animals. While some species, like Parasaurolophus, were very rare among their local fauna and probably lived in very small herds, some bone beds have been found to contain thousands of individuals, likely representing herds moving across the landscape. This means that these dinosaurs likely needed ways to communicate, and they evolved the ability to communicate advanced messages throughout their nasal cavities. Lambeosaurs evolved a series of long, looping canals throughout the crests on their head, which produced a loud, trumpet-like sound when air was forced through it. Not just that, but since not just every species, but every individual has a slightly different shape to their crest, individuals could recognize each other through their calls. Hadrosaurs, however, didn't have large cranial crest to help communicate, yet we know they lived in herds. So what some scientists think they did was use their large nasal openings to communicate by inflating and deflating skin around them, causing a honking noise similar to geese.

Hadrosaurs also are notable for being very good parents, as shown by their complex social lives, and the discovery of fossil nests that were organized in a similar way to birds. The nests themselves are actually very similar to modern day megapode birds, which are a type of bird from southeast Asia and Australia, and evidence suggests that the nests were used year after year. The nests are also perfectly spaced, exactly one hadrosaur body-length apart. The nests themselves were bowl-shaped and filled with vegetation to help incubate the eggs. Baby hadrosaurs and fossil embryos have been discovered and show that the limb bones were poorly developed, suggesting the young were nest-bound and that parents probably brought food back to the nest to feed them. Growth rates from hadrosaurs show that they reached close to 3 meters in just a year or two of growth, one of the fastest levels of growth seen in the animal kingdom.

While many of these discoveries have been made in North America, as I stated above, they were not limited to that area. Both the largest and most primitive members are actually from Asia, and it is likely that that is where they originated. Dwarf hadrosaurs are also known to be found in Europe, which was once a scattering of small islands at the time. Other fossil hadrosaurs and complete nests have been found in South America, and we've even found them as far south as Antarctica. All these fossil finds clearly show that these animals weren't just tyrannosaur chow, but they were brilliantly evolved creatures ready to do what they needed to do to survive. Too bad their reign was cut short by extinction, I would've loved to have seen them in their glory.
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So there you have it. I hope that I answered your questions, MrGorsh. If there is still anything you might be wondering please feel free to leave a comment below, and for everyone else I hope you find this topic as interesting as I do.

For my next post I really don't know what I want to write about since I have so many ideas. Maybe something either about other Mesozoic animals, or perhaps something from more recent times? If you give me some feedback, I'll make sure to address topics you want to know more about. Until then, stay sharp!

The Skulls of Sauropods and Their Behavioral Significance

A fossil replica of Camarasaurus lentus' skull.
Camarasaurus is one of the few Sauropods we have complete skulls for.

Sauropods were the most successful group of land herbivores to have ever evolved. They lived and dominated the Earth since the dinosaurs' reign began in the Triassic, straight through to the very end of the Cretaceous. They evolved into a variety of unique shapes, yet kept their ingenious body plan in check in nearly all of them. They have been found on all continents, including Antarctica, and thus some might have even braved icy climates. They were also the only land vertebrates that regularly rivaled, and in the case of Amphicoelias and (possibly) "Bruthathkayosaurus," even exceeded the maximum known size of modern day whales. However, despite their amazing sizes, shapes, and complexity, the sauropod's skull was tiny compared to the rest of the animal, barely taking up 1/200th of the total body mass, and rarely getting preserved. This has led to many problems when it comes to constructing how these animals lived, ate, and survived. Luckily, the few skulls we do have have shown that many sauropods had some unique ways of adapting to many existing problems in their native environments.

All sauropods for which we have skulls show many differences from those we've collected of their relatives/ancestors, the prosauropods. For one, the skull of prosauropods is greatly elongated, while most sauropods have skulls that were shorter. In fact, and I mentioned this in one of my other posts, the skulls of sauropods resemble the fossil hatchlings of prosauropods, suggesting that prosauropods evolved by retaining juvenile traits into adulthood (a similar theory has been put forth on how birds evolved from theropods). The openings in the sauropod's skull, known as fenastrate, are also much less organised than in prosauropods. While prosauropods had their skulls' fenestrate in line along the horizontal axis, sauropods had all the skull openings towards the top of the skull and lie in an almost "zig-zag"pattern.

Where the nostrils of sauropods were thought to have been
as opposed to where we think they are now.
Image from palaeozoologist on Deviantart.

In many sauropods, specifically the members of the macronarian branch, the snout comes far forward of the external nares, the area that holds the nostrils. For a long time it was thought that this meant sauropods had their nostrils on top of their heads for snorkeling, as they were originally thought to be water-dwellers. In recent years, however, we have proven that sauropods indeed had their nostrils present on their snouts, and that the nostril openings were lead through a shallow depression of bone along the snout. Why did sauropods have this arangement? Well a number of theories have come forth as to why. Some have suggested it was for temperature control, others think that in some members with enlarged external nares like Giraffatitan and Camarasaurus, they could have been able to inflate skin around their nares to create a display. I, however, am fond of the idea that they might have been covered by a keratinous covering and used, along with their super-sized necks, to create low-frequency calls to communicate over long distances. Elephants, the largest land animals alive today, use low-frequency sounds to communicate over vast distances, why not sauropods?

Of course when you have a skull of an animal, one of the first things many people will examine is the teeth, and sauropods aren't lacking. We find many isolated teeth in the fossil record, and different groups of sauropods evolved different tooth designs. Primitive members of the sauropoda like Mamenchisaurus had teeth shaped almost like spoons, later diplodocoids like Apatosaurus and Diplodocus had teeth shaped almost like crayons, and macronarians like Brachiosaurus and Argentinosaurus kept the spoon-shaped teeth of earlier sauropods (well, that isn't necessarily true for the whole group, but I'll get into it further down). The teeth of sauropods were also much larger than earlier prosauropods, and took up a larger portion of the jaw. Many have less than 15 tooth positions on each side of the upper and lower jaw, basal members, however, could have up to 20, and the wonderfully weird rebbachisaurids could have dental batteries of over 30 tooth positions each with up to 8 replacement teeth underneath the present tooth!

A reconstruction of the head of a Diplodocus.

These teeth can tell us exactly what these animals were eating when you examine the amount of wear present on each tooth. When examined in this way, it seems diplodocids, like Diplodocus and Apatosaurus with their pencil-shaped teeth, had evolved to feed on trees, but were very selective, and might have preferred softer plants. In fact, a recent study using computer models found that Diplodocus' skull was best built to strip leaves right from branches. This is the first time such a method has been used on an herbivorous dinosaur, and might answer many questions as to how certain herbivores processed their food.

Not all diplodocoids likely used Diplodocus' method of feeding, however, such as the rebbachisaurid Nigersaurus, with its almost duck-like snout with close to 600 teeth all aligned across the front. Nigersaurus was likely a grazer, using its long neck to shift side to side cropping up large mouth fulls of low-growing plants. Another diplodocoid, Dicraeosaurus, had a very short neck and couldn't reach high into the trees, yet its teeth and skull suggest it was doing a similar thing as Diplodocus, perhaps to bushes instead of trees.

It also seems that many macronarians like Giraffatitan and Camarasaurus were doing something different than diplodocoids.  Macronarians and primitive sauropods, as stated above, had spoon-shaped teeth, and studies suggest they were messy eaters, and likely took in large amounts of conifers and other tough vegetation in their wide mouths. They were essentially just taking huge mouth fulls of vegitation, and when you take into account that a Giraffititan's head is about five feet long and about one and a half feet wide, they could have swallowed a small child if they wanted to! Many people forget this when studying sauropod dietary needs, and make unreasonable estimates that they might have needed to feed for 24 hours straight to gain enough food to keep themselves going. In truth, because of their huge mouths, it might have taken less time for a 30 ton Brachiosaurus to feed itself than a much smaller 5 ton elephant, which needs to sacrifice time chewing and is only able to pull up small bits of food in its trunk. Many primitive sauropods were doing similar things to macronarians, except a few might have instead fed on softer vegetation as opposed to tougher forms.

It's interesting to note, however, that a group of later Cretaceous titanosaurs, called the saltasaurids, evolved heads and body designs similar to late Jurassic diplodocids. In fact, the teeth also evolved into the crayon-shape of diplodocoids as well. Diplodocoids went extinct during the mid Cretaceous, likely being victims of a small extinction event that took place, but macronarians survived, suggesting that with diplodocoids absent, they started filling in the niches left by them and evolved similar ways of feeding.

So as you can see, sauropods seem to have made a decent living during the Mesozoic. Their skulls covered a variety of different shapes and forms in order to access their different food preferences. However, out of all different types of sauropods skulls that we have preserved, one species in particular seems to stand out. Uncovered in Argentina's Banjo de la Carpa formation in 2004, Bonitasaura salgadori has one of the oddest heads of any sauropod.

Bonitasaura's weird yet wonderful skull. Wish it was a frontal view though
since the head can be most admired from that angle. 
Known elements are in gray, reconstruction in white.

Bonitasaura's skull was extremely fragmentary when discovered, and the scientists who found the specimen at first didn't realize its significance. They did notice, however, that the skull was already a little weird; it was squared off and looked very similar to Nigersaurus' duck-like mouth, despite the fact Bonitasaura was a titanosaur, not a diplodocoid. This could be another good example of convergence between diplodocids and titanosaurs. Other than that though, the skull wasn't given much attention, and it wasn't until 2010 that paleontologists Pablo Gallina and Sebastián Apesteguía found something very interesting about the animal's lower jaw. It seemed that right behind the tooth rows, a large ridge was present that seemed to, in life, posess a keratinous beak!

The term "beak," however, should be used loosely. In truth, they were just large sheaths of keratin in the jaws that may have helped with oral processing. Still, this is a major discovery that needs more exploration, for example: Was Bonitasaura the only beaked sauropod, or did other species have beaks present and we just don't have their skulls yet? Why evolve a beak in the first place? Was the beak also present on the upper jaw, or only the lower one? Does the presence of a beak suggest that oral processing was becoming more important to sauropods towards the end of the cretaceous, possibly with angiosperms becoming more common? So far we can't answer any of these questions, and it will take much more complete specimens of this species in order to even come close to answering them.

Anyway, as always, feel free to share you're opinion and ask questions. As I said before, I also take requests for topics, since I want to tell you guys about what you want to know. The next post will be the one recommended by Mr. Gorsh, so be prepared for hadrosaurs, iguanodonts, and hypsilophodonts.