"New discovery: Oldest nests and embryos discovered in South Africa" When I first read the title of the article I immediately knew what they were talking about. The article was referring to the discovery of fossil dinosaur nests and eggs belonging to the Prosauropod dinosaur Massospondylus, a plant eater that's line was among some of the first giant herbivores in the history of life on earth.
These nests weren't new to the scientific community though, the first Massospondylus eggs ever found were unearthed in 1977, and thirty years later in 2007 we finally had the technology to be able to break into them and examine the tiny embryos. The eggs and embryos date back to 190 million years ago during the Jurassic Period, making them the oldest fossil eggs on the planet. Now with more recent expeditions we have uncovered about 10 more nests filled with up to 35 eggs with embryos. We've hit paleontological gold!
The embryos house some interesting little surprises. The skulls of the juvenile Massospondylus are disproportionately large, and the neck, unlike their parents, is actually quite short. The eye socket is also very large, something seen in young animals today, and the front and back legs were of equal length, unlike adults which have short front legs and long back ones. This suggests that the juveniles were quadrupedal and grew to become bipeds.
However, what's most surprising is that the Massospondylus embryos have no teeth. This was unexpected, as the juveniles would need teeth to feed themselves to fuel the growth of their bodies. This indicates that the young were dependent of the parent for food, meaning Massospondylus exhibited parental care and fed the young after hatching, at least until their teeth grew in.
A Diagram of a juvenile and sub-adult Corythosaurus' nasal crests.
These passageways in the crest most likely helped the dinosaur with communicating.
Communication in dinosaurs has always been a troublesome concept to understand. Why? Well, nobody's heard a dinosaur in more than 65 million years! All kidding aside, nobody knows what a dinosaur sounded like and sounds don't get fossilized. However, some discoveries and papers were presented recently, and have finally given us a some good clues as to what dinosaurs sounded like. These findings have been very important since knowing what dinosaurs sounded like can give us some good clues about their behavior and tell us what they were like when they were alive.
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The Mesozoic Music of Parasaurolophus
One of the first major finds when it came to dinosaur communication came in 2007. Scientists from the Sandia National Laboratories and the New Mexico Museum of Natural History collaborated together to find out the exact noises and calls of a well recognized dinosaur, Parasaurolophus.
Parasaurolophus was a large herbivorous dinosaur that lived 75 million years ago. It was a member of the Lambeosaurids, a group of duck-billed dinosaurs that thrived at the end of the age of dinosaurs. It's most distinguisable by a elongated crest sticking out of the back of its skull, forming a banana-like structure attached to its nasal passageways. For a long time this crest was thought to be used as a snorkel while foraging underwater, since it was widely thought that these animals were water dwellers. However, the study showed otherwise.
The study used advanced computer tomography and C-T scans on a well preserved 4.5 foot long Parasaurolophus skull. They found that unlike originally thought, Parasaurolophus didn't have an opening on the top of its crest through which it could breathe. Instead, the study found that the skull was filled with complicated tubes and chambers, which showed a striking resemblance to a trombone.
After the C-T scans were made, the computer then made a digital copy of the skull and simulated air flow in a type of 3-D virtual instrument. Variations were then made to accommodate the lack of vocal chords, as it was unknown whether or not Parasaurolophus had them. I'll talk more about this later in the post.
These calls were within the low frequency range -- so low that much of the actual sound isn't picked up in our ears. However, studies of Parasaurolophus' brain case have shown that it was capable of hearing very low frequencies. This means that Parasaurolophus was using its calls to communicate with others of its species, suggesting that it was possibly a social animal and used its advanced nasal tubes for communicating complex messages with other Parasaurolophus. Thus, this discovery gave us a very good idea as to its behavior and how it lived.
In the following years, scientists continued to make more and more finds about the sounds dinosaurs made. Many were completely unexpected and downright bizarre. One of them was in 2008 when scientists at Ohio University discovered something in two armored dinosaurs: Euoplocephalus and Panoplosaurus.
A Euoplocephalus Skull
Note the complicated nasal passages.
Euoplocephaulus (Skull is Pictured right) was an ankylosaurid dinosaur that lived about 72 million years ago. It was a heavily armored quadrupedal herbivore with a thick club at the end of its tail. Euoplocephaulus is probably most famous for the fact that it has a mix of thick armor, spikes, a powerful tail club, and most surprisingly, armored eyelids, making it one of the most well protected animals ever to have lived. Euoplocephaulus is arguably one of the most well documented ankylosaur. We've got a large number of partial and complete skulls and skeletons of it and almost every piece of its anatomy is known.
Panoplosaurus lived in the same time and place as Euoplocephaulus, but it didn't seem to be as heavily armored. It was a member of the nodosaurids, close relatives of the Ankylosaurids which have longer tails, legs, and skulls than the ankylosaurids, but don't have as thick armor or the clubed tail. However, unlike Euoplocephaulus, it has long spikes on its shoulders that could also have been useful for defense, and the skull from the only known specimen also shows that it had thick armor plating over its cheeks as well.
The study was started to try and map the complex airways and channels within multiple dinosaurs' skulls and brain cases, from nasal channels to air sacs. However, while examining these two dinosaurs, they found something unexpected. According to the C-T scans, Euoplocehalus' and Panoplosaurus' nasal passages took a long, twisting, looping course through the snout from the nostril all the way to the back of the throat. It was already known that the nasal passageways were well developed and elongated, as it was thought smell was one of their primary senses, but these complex looping chambers were completely unknown.
Since there was an area with large blood vessels surrounding the passageways, the scientists thought it might have something to do with heat exchange. This structure could warm up air that comes into the body, and thus warm up the animal. But more examinations showed these passageways were also oddly similar to Parasaurolophus' nasal chambers, and thus could have also been used as a method of communication.
As the study progressed, they mapped both animals' brain cases and found that the inner ear was fine- tuned to hear low frequencies. This was the same pattern as seen in Parasaurolophus -- long complex nasal chambers and good low frequency hearing -- suggesting again that these dinosaurs used their nasal chambers for communicating.
Euoplocephalus and Panoplosaurus got almost no attention, despite being the most interesting part of the article. Even I didn't hear about the discovery until recently. I hope that this discovery will become more widespread and known in the future.
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What about Vocal Cords?
Mammals have vocal cords. Crocodiles have them as well, but what about dinosaurs? Many people might find this to be a silly question, but actually, most animal groups don't have vocalization structures. Only a select few types of animals are able to communicate vocally with a Larynx (the scientific term for vocal cords). Were dinosaurs able to as well? Let's see.
Modern day crocodilians, as I said before, have vocal cords. Dinosaurs' closest living reptilian relatives are crocodiles, so we should expect them to have it as well. However, it is impossible to find out exactly when the larynx in crocodilians appeared, as it shows no sign of itself on fossils. The latest a larynx could have appeared is during the early Cretaceous, when the ancestors of modern day crocodiles, alligators, and gharials first appeared, known as the Isisfordia. So crocs can't help us here, nor should they.
You see, crocodiles do have a larynx which they use to communicate vocally with low roars, but birds, the decedents of Dinosaurs, don't. Birds instead have a Syrinx (Pictured left), the avian version of vocal cords, which is located farther down near the base of the trachea, and is arguably more advanced. It is a structure that evolved completely independently from the larynx, so the ancestor of both birds and crocodiles, and the ancestor of the archosaurs, had no vocalization organ. Dinosaurs, being part of the bird side of the archosaur family and their immediate ancestors, would have likely had a syrinx instead.
However, their is a twist to this idea. The avian syrinx, unlike the Larynx, leaves evidence of its presence on animal bones, and should be seen in dinosaur anatomy. A major factor for the syrinx in birds to operate is a structure called the clavicular air sac. Located in the chest cavity of birds, it is an organ that allows the syrinx to function, but when looking at Dinosaur anatomy, they seem to lack one. There is no evidence of a syrinx or a clavicular air sac in dinosaurs (with the exception of the Allosauroid Aerosteon, which likely evolved its clavicular air sac independently from birds and developed it for another purpose). The earliest signs of such a structure are seen in the primitive ornithothoracine birds, which means all dinosaurs likely couldn't vocalize. Therefore, noises such as grunts, bellows, chirps, shrieks, and roars were impossible for most dinosaurs.
The discovery that Dinosaurs lacked vocalization organs definitely will disappoint Dinosaur fans young and old alike, but this doesn't necessarily mean Dinosaurs were silent animals. Just look at modern day animals that lack vocal cords, such as Komodo Dragons. They are still very loud animals that communicate through deep hisses, tooth grinding, and jaw claps. There are also a few species of birds alive today that lack a syrinx, such as California Condors, which instead communicate through hisses and other non-vocal sounds.
Tyrannosaurs, and other large theropods with an increased surface area in their mouths, could create loud, booming claps with their jaws. Hisses could also have been a major way of communicating in carnivores, and the large sizes of the throat and esophagus could deepen these hisses. Smaller carnivores, like Dromeosaurids and Ornithomimids with an elongated trachea, could also change the pitch of their hisses. Swans use a similar method thanks to their elongated trachea structure.
An elongated Trachea is also present in the long necks of Sauropods, and also could deepen and control the pitch of hisses. Their have also been some theories that suggest the tails of Diplodocids could be used to produce noises, similar to how a whip cracks as it slices through air. Personally, I also think there is a possibility that some Stegosaurids could shake the plates on their back to create a sound display.
This discovery, however, doesn't mean the elongated nasal tubes in Lambeosaurids and Ankylosaurs were not capable of creating sound. Some species of snakes are capable of using chambers in the skull and nasal passageways to lower the frequency of hisses, meaning they could still use these chambers to produce noises. Brachiosaurids also have large nasal chambers on the top of the skull. These chambers could be filled with air and used like Parasaurolophus' crest to amplify noises, somewhat like how a drum amplifies the vibrations around it. Hadrosaurs might have possessed nasal sacs that could do the same thing.
Dinosaurs could even use their environment to communicate. Modern day animals splash in water, stomp on the ground, knock on trees, and beat their wings (which could be achieved by some feathered dinosaurs) to communicate. But it seems that Dinosaurs likely used other ways to communicate rather than just noises. Like most modern birds and reptiles, dinosaurs mostly used visual displays to communicate.
Most dinosaurs have visual structures on their bodies, such as crests, horns, frills, domes, plates, spikes, sails, and feathers, all of which could be used for visual communication. It seems dinosaurs used similar methods that both reptiles and birds use today, methods they use to distinguish themselves from related species, attract mates, frighten predators, and show their age. This is likely why such structures evolved in the first place, due to pressures to communicate as they became more advanced animals.
Seems like dinosaurs couldn't roar like they are typically portrayed in popular culture and movies like Jurassic Park, but seem to have found many ways around that problem. Dinosaurs were definitely different in their approach to life than modern day large mammals, and we should expect such things. Dinosaurs aren't mammals, they're archosaurian reptiles, so we shouldn't expect them to act or behave like mammals. We should, however, expect them to behave like reptiles and birds, the animal groups that they actually belong to.
This is why I personally dislike calling Triceratops a "Mesozoic Rhino" or Velociraptor a "Cretaceous Wolf." I'll write a post about those theories in the future. Until then, please leave a comment so I know you're all listening and I'll do my best to answer.
Picture of the newly discovered Pampaphoneus biccai hunting a pareiasaur
Ok, take a Tiger, then give it the legs and tail of a Komodo Dragon, pull it's skull a bit to look like a Crocodile, and give it the saber teeth of a Homotherium. Then you'll get a good picture of the newly discovered Brazilian synapsid Pampaphoneus biccai.
Pampaphoneus was the top predator in it's environment, and likely preyed on primitive proto-turtles called pareiasaurs that have been known in the area for years. Even though it looks very reptilian in apearance, like all synapsids, Pampaphoneus was more closely related to mammals than it was to other reptiles. While it's not likely to be our direct ancesstor, it's line likely gave rise to the first true mammals. So in a way you can call it our great, great, great, great, great uncle.
Map of T-rex's sinuses and airways compared to a Human
Our first look at Tyrannosaurs to conclude whether or not they were active predators, bully-like scavengers, or opportunistic feeders starts by looking at their senses. Could the Tyrannosaurid's senses actually support an active hunter, or were their minds set for finding already dead meals? So, let's get started with this debate on the Tyrant Lizard's senses:
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Eyesight:
We know from cat scans of Tyrannosaur brain cases that their eyesight was well developed. It was about as advanced as a human’s and was supported on a head about 12-13 feet off the ground, so the animal had good eyes, and a good view. However, T-rex, unlike almost every other large theropod up to that point in time, had an increased field of binocular vision and depth perception.
All other more primitive Tyrannosaurids didn't even come close to the forward facing eyes of T-rex. It by far had the most well developed eyesight in the entire group. However, does this good eyesight mean T-rex was an active hunter? Well, no.
Yes binocular vision is an important evolutionary advantage to securing prey nowadays, and is seen in many active predators. But many scavengers also have it. Vultures, condors, Tasmanian devils, Johnny Rooks, hyenas, and many other scavenging animals have binocular vision. Same thing is true of predators, not all have binocular vision. Nile crocodiles don't have it, yet they remain top predators in their environment, hunting almost everything in it.
So really, vision doesn't mean much in this argument. However, the fact that T-rex was evolving better eyesight than most of its predecessors seems to suggest binocular vision was getting more important down the Tyrannosaur line.
Smell:
Smell, as with eyesight, was always known to be good in Tyrannosaurids. Cat scans and casts of the braincase showed extremely large olfactory lobes, the area in the brain that processes smell in animals. Not just that, but the large nasal chamber in between the olfactory lobes and the nostrils was huge and long in many species.
On the inside of this chamber were billions of tiny sensors. The exact number of sensors is unknown, but for comparison a human has about as many sensors as would cover a postal stamp, and a bloodhound has about as many sensors as would cover a tablecloth. T-rex, having a skull as big or bigger than a bloodhound, might have had enough sensors in its nose to cover the side of a house, but it's just an educated guess.
This was one of the many reasons T-rex was thought to be a scavenger; like a turkey vulture, T-rex could sniff out dead animals from a great distance away. However, just like with eyesight, it doesn't necessarily mean anything. Many modern day predators have great smell and use it to track down their prey. The same is true for scavengers.Not all vultures have a great sense of smell.In fact, many old world vultures don't have a very well developed sense of smell at all, but instead rely mostly on eyesight to find dead animals.
Hearing:
Hearing ability in T-rex was unknown for a long time since the delicate structure of the inner ear wasn't typically well preserved in fossils or casts. But thanks to recent advances in technology, we now know T-rex had very good hearing, as was expected.
Modern day birds and crocodiles are well tuned to hear low frequency noises. Pigeons can hear coming storms from more than 30 miles away. Alligators in Florida have also been known to react to the low frequency rockets launched by NASA. Most dinosaurs had equally good hearing, and the same is seen in T-rex. In fact, T-rex has also been found to have a huge Tympanic Membrane (Ear drum), more evidence for great hearing. However, again, this doesn't mean anything.
Hearing doesn't really mean the animal is a good hunter, or a good scavenger. Either predator or scavenger might benefit from acute hearing, so is doesn't support either argument.
Overall Intelligence:
Typically, large predatory dinosaurs have the intelligence level comparable to that of a crocodile. Crocodilians are very smart animals that can think and learn from their environment very easily. Many predatory dinosaurs were the same, but T-rex and its kin were different.
Unlike almost all other large predatory dinosaurs, T-rex was descended from small predatory theropods in the Jurassic called Coelurosaurs. Coelurosaurs are known for being small, intelligent predators that hunted small game among the shadows of top predators like Allosaurus and Carcharodontosaurus. But T-rex's ancestors evolved gigantic sizes once all those large carnivores went extinct during the early stages of the late Cretaceous and the size of the Tyrannosaur’s brain remained large.
Tyrannosaurs were the smartest of all large theropods; their intelligence probably was within the very lowest levels of bird intelligence. It could probably think and make things out to a better degree than crocodiles can today. But still, as with modern crocodiles and birds within T-rex's range of intelligence, he probably still used more instinct than brainpower while hunting.
As with all the previous senses though, it doesn't mean anything. Many scavengers today are very wily and smart and a number of predators today are not particularly intelligent such as the monitor lizard. T-rex just kept the same brain size to body ratio as its ancestors. So again, intelligence doesn't really mean anything in this argument.
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Conclusion:
T-rex and its fellow Tyrannosaurs had senses that don't really support a predatory or scavenging lifestyle. They support both. A predatory animal or a scavenging animal could get along well with T-rex's very reliable senses. So its senses don’t suggest either.
Tyrannosaurs were giant predatory theropods that lived during the very end of the age of the dinosaurs. Monstrous beasts that terrorized the landscape and killed any unfortunate herbivore they happened to come across. Huge and fast, equipped with banana sized teeth and jaws that could bring down prey with a single, bone-shattering bite; these must’ve been the top predators of their environment. Or were they?
Some scientists have questioned the idea that Tyrannosaurs were top predators, but instead quote many unnoticed features about their anatomy. Tiny useless arms not useful for hunting, bone-crushing jaws for extracting marrow, bodies that were too large and legs to thick to sustain a very fast running speed. All these traits seemed to be pointing towards T-rex and its relatives to not be predators, but something else; Scavengers.
This has been a reoccurring topic for many years now; it is one of the longest running debates in paleontology. Although much of the public and the majority paleontologists find Tyrannosaurs to likely be active predators, both sides have substantial amounts of evidence for their own cases. I can say though, when I first learned about this theory, I went mad.
I first heard about it when I watched the BBC Horizon documentary T-rex: Warrior or Wimp when I was about 6 or 7. I completely hated the idea; I knew they must be wrong; T-rex was a cold-blooded killer that could kill and eat anything it wanted. Jurassic Park and all those other scientists couldn’t have gotten it wrong, could they?
The years went by and I continued to believe T-rex and other Tyrannosaurids were powerful predators, chasing down game on a prehistoric Serengeti, and brawling with herbivores like a prehistoric version of Godzilla. However, that all changed as I continued to grow and mature. I began going back to the Scavenger Hypothesis as I continued to learn about T-rex.
As I looked the facts over and over again, I started to understand where the other scientists' reasoning was coming from. Some of the things I just assumed weren’t actually true, and my own ideas were replaced by scientific facts. I learned how T-rex’s body worked, learned about its anatomy and habits, and even learned many problems found in the Predator hypothesis as well as the Scavenger one. For a short time, even I, the little kid that couldn’t accept T-rex as being anything less than a monster, started to consider T-rex to be a scavenger.
I continued to learn about more and more theories on the monster. New evidence would continue to pop up for both sides claims, and my own mind was being pulled into different direction over what T-rex and its kin were actually like. Some scientists like Dr. Bob Bakker Considered T-rex to be a Hunter, other scientists like Dr. Jack Horner thought it to be a scavenger, and some scientists even proposed that ist was a little bit of both.
As time went on I started shift between the theories every once and a while. At the moment I’m at one of the point where I can’t find out myself, and that’s where this topic comes into play. Since I’ve had such a long history learning about T-rex and its kin, I've decided that this should be one of my first topics to look over and finally try to see what T-rex did to get a meal.
For the next few weeks, I'll be investigating deeply into Tyrannosaur anatomy to find out exactly what their feeding strategies were like, and how they sustained their bodies. What conclusions I make are entirely my opinion based on scientific facts I’ve learned about over the years. So, let's find out where T-rex and it's kin belong on the food chain, shall we?
The mother and infant Tyrannosaurus from Walking with Dinosaurs: The Live Experience
Dinosaurs: They've haunted our imaginations since we first laid eyes on their skeletons in our local museum. Creatures of tremendous size, strength, and power that once lived and breathed on a long lost Earth. So far from understanding them or their lives, yet so close that we can just reach out and touch them.
People sometimes ask me, why are people so fascinated with dinosaurs? Why are we so attracted to them? Why are we so curious about them? At first I wasn’t able to answer these questions myself. What's the reason? Why am I the Dino nerd I am? Well, to answer these questions we might need to go and see what a dinosaur is in the first place.
Dinosaurs were named by Sir Richard Owen in 1842, and roughly translate to “Terrible Lizards.” Not actually true lizards, they represent a distinct group of reptiles called Archosaurs which includes Crocodilians and kin, Pterosaurs, protodinosaurs, and modern birds. Archosaurs are arguably the most successful group of land vertebrates on the planet, ranging in size and diversity to take on a number of bizarre forms, typically taking body designs to the extreme, and benefiting from being odd.
Dinosaurs were among the most diverse and successful of this group, ranging in size and shape from small feathered predators a little over a foot long, to 100 ft. giants that make entire herds of elephants look tiny. One thing that separates them from other groups of reptiles and many other types of Archosaurs is the fact that unlike other reptiles with sprawling legs like a lizard, dinosaurs had their legs directly underneath their body in an erect form, similar to modern day mammals. This allowed them to support more massive bodies and more active lifestyles than other animals at the time. The ancestors of dinosaurs had erect legs even before the first mammals evolved the trait --they invented the leg design.
Along with being the first animals with erect limbs, they also evolved more complex ways of living. It was originally thought that dinosaurs were ectothermic (cold-blooded) and similar to most reptiles in their metabolic rate. However, in 1968 a series of papers by Dr. Bob Bakker started citing more and more evidence for endothermy (warm-blooded) in dinosaurs, and is nowadays widely accepted in the paleontological world. A group of dinosaurs in particular, called Theropods, evolved to be active fast-moving predators, something that typically is only seen in endothermic animals.
Other evolutionary advantages soon followed, along with being endothermic and having an erect leg posture, they also evolved many other distinct features to adapt to their world. Many Ornithischians evolved the ability to chew their food, something rarely seen in reptiles, which helps with speeding up digestion. Saurischians on the other hand evolved a highly advanced method of breathing by using air sacs connected to their lungs, a method very similar to that of birds.
Dinosaurs were extremely successful even since their origins in the Triassic, they were the most successful group of land vertebrates of their time, and were far more successful than all modern-day mammals. More dinosaurs are discovered and named every few weeks, and amazingly, we’ve only discovered a little more than 2% of all the dinosaur species to ever have ever lived on this planet. But the mystery still remains: Why if they were so successful did they go extinct?
The answer to this question is very uncertain. Maybe it was increased volcanic activity, or possibly sea levels dropped dramatically, or maybe even a deadly virus was among them. At the moment the most widely accepted theory is that a meteorite smashed into the Gulf of Mexico and caused their extinction, but there is still much to debate about.
All we know for certain is that dinosaurs are gone, leaving only their descendants, the birds, to fill our skies overhead. Maybe that’s the reason why we’re so keen to learn about them. Dinosaurs were some of the most amazing and diverse creatures to ever live on our planet, and they’re gone. But of course, we should in a way be thankful, for without them disappearing, we would never have appeared on this planet. The dinosaurs reached a sad end, and as with all creatures, we will one day follow.
The fact that such powerful creatures ruled their planet for so long, it somewhat reflects upon ourselves. Dinosaurs were the kings and queens of the planet, and lived in a kingdom that was all their own, only shared by some terrestrial crocodiles. We are the same. We humans are the kings and queens of our planet right now. We live in a time of plenty and are the dominant creature on the Earth, but for how long will our kingdom last? Will we go the same way as the dinosaurs? Most likely, yes. No creature, no matter how powerful, can survive forever, and dinosaurs prove that.
That’s the reason why I think we’re so fascinated by dinosaurs. We Homo sapiens have only existed for the past few hundred thousand years, while dinosaurs have ruled the earth for a total of 165 million years, and continue to thrive today in the form of birds. But how long do humans have left? Will we continue to thrive onwards into the future, or is our time on planet Earth quickly running out? Only time will tell.
Welcome my fellow Time Travelers to the Dinosaur Archives! I'm your fellow Dinosaur nerd RaptorX and I'm here to help you explore the past and its mesmerizing splendor. Dinosaurs have been part of my life since I was little, and ever since I first learned how to read, my one true dream was to become an expert in paleontology.
Dinosaurs are fascinating creatures filled with mystery, and our ideas are almost constantly changing about them; a book published just a few months ago might have old information seeing just how fast paleontology changes. Why when I was a baby, probably less than 14 years ago, dinosaurs seemed to be scaly reptiles, now we know that many were covered in filaments that evolved to become the first true feathers.
All that one needs to do to learn about what dinosaurs were like is to use their own mind and some ingenuity. Many in-depth scientific studies start by looking at both modern animals, and by looking into our own minds to imagine a long lost world. Most recently, scientific discoveries and ideas over the last few years have changed much of what we originally thought about them. We're only just scratching the surface to understand behavior in these animals, which is what I'm particularly interested in and studying right now.
I hope you will all join me to see just how amazing these creatures were. Any questions, ideas, and theories for topics will be greatly appreciated and all comments are also welcomed. I hope you all enjoy your time on my site and are able to learn as much as you wish about these extinct creatures.
