Sunday, June 6, 2021

Tlatolophus: Beast of the Week

 This week let's celebrate a newly described dinosaur.  Check out Tlatolophus galorum

Watercolor life reconstruction of Tlatolophus by Christopher DiPiazza.

Tlatolophus was a hadrosaurid ("duck-billed") dinosaur that lived in what is now Coahuila, Mexico, during the Late Cretaceous, about 73 million years ago.  It was a massive animal, measuring about 39 feet (12 meters) from beak to tail and would have eaten plants when alive.  The genus name translates to "word crest" because this dinosaur's bony head crest resembles the Aztec glyph meant to represent speech. 

Aztec word glyph which coincidentally resembles Tlatolophus' crest, just rotated. Originally from Codex Barbonicus. Image taken from Mexicolore.co.uk.

Like many large dinosaur fossils, Tlatolophus is known from incomplete remains.  That being said, the parts that were unearthed give important information about this dinosaur.  Most amazing is the fact that almost the whole skull was intact, including the elaborate crest.  (It's frustrating when a new hadrosaurid, family of dinosaurs known for having diverse crests, is discovered with no head, leaving us completely in the dark as to what it would have really looked like.)  Tlatolophus' crest was shaped like a sideways teardrop, sweeping back, behind the animals head and flaring out at the end.  The crest was hollow and connected to the animal's nasal cavity, suggesting it may have aided in producing some sort of sound in life.  

Photograph of Tlatolophus' beautifully complete skull, featured in the recent paper cited below.

Like all hadrosaurids, Tlatolophus had a beak in the front of its snout which would have had a keratin sheath growing over it in life.  This beak would have evolved for clipping off mouthfuls of vegetation which would then be shredded by the many tiny, tightly packed, teeth in the back of the mouth.  Tlatolophus also likely would have been able to walk on all fours, or on its hind legs depending on what suited it best.  It is thought that hadrosaurids most comfortably walked on all fours, but would rear up to reach higher plants while feeding, or to run faster as bipeds to escape predators.

Tlatolophus also had a long tail, proportionally longer than what is typically seen in other hadrosaurids, which made up about half the animal's total body length.  It is a total mystery why this specific hadrosaurid evolved such a long tail.  Maybe it had something to do with courtship display?  Maybe it was evolved to hit rival adults for dominance?  Long tails are also effective weapons against predators that may try to attack from behind.  A strong impact from a tail like that would surely knock a similarly-sized tyrannosaurid over, giving Tlatolophus time to escape.  We may never know for sure, however.  

It is interesting to note that paleontologists deducted, based on features of the skull, that Tlatolophus was closely related to another, more famous, hadrosaurid that also sported a striking crest, Parasaurolophus.  What's interesting is that Tlatolophus is even more closely related to Parasaurolophus, which is found in Canada and the United States, more than the hadrosaurid that it coexisted with in Mexico, called Velafrons.  It just goes to show how much different populations of closely related dinosaurs were moving around and settling in different areas over the millions of years they reigned.  

That is all for this week!  As always feel free to comment below!

References

Ramírez-Velasco, Á. A.; Aguilar, F. J.; Hernández-Rivera, R.; Gudiño Maussán, J. L.; Rodriguez, M. L.; Alvarado-Ortega, J. (2021). "Tlatolophus galorum, gen. et sp. nov., a parasaurolophini dinosaur from the upper Campanian of the Cerro del Pueblo Formation, Coahuila, northern Mexico". Cretaceous Research. in press: Article 104884.

Monday, April 19, 2021

Astrodon: Beast of the Week

 Today we will be checking out a dinosaur with historical significance, Astrodon johnstoni!

Astrodon was a plant-eating sauropod dinosaur that roamed what is now the eastern part of the United States, during the early Cretaceous period, about 112 million years ago.  Adults would have measured between 50 to 60 feet (15 to 18 meters) long from snout to tail.  The genus name translates to "star tooth" and the species name honors Christopher Johnson, the dentist and professor who studied the first known fossils of this dinosaur back in the 1800s.  

Watercolor life reconstruction of Astrodon johnstoni by Christopher DiPiazza

Astrodon was one of the first fossil dinosaurs to be discovered and named in North America.  It was initially known from a few teeth discovered and studied in Maryland, where Professor Christopher Johnson, at the Baltimore Dental College, noticed they had a star-shaped pattern in the cross section, and thus Astrodon earned its genus name.  Over the years more fossils from Astrodon would be discovered in the eastern half of the United States, including many bones from juvenile individuals.  

Original Astrodon tooth currently at the Yale Peabody Museum.  Photo courtesy of Kenneth Carpenter.

By comparing its bones to other sauropods, it is currently thought Astrodon was a kind of macronarian, which is a clade of sauropod dinosaurs that had boxy skulls with large nasal cavities. In fact, the term, macronarian, translates to "big nose" based on this common feature.  Another example of a macronarian sauropod is the larger and very famous, Brachiosaurus.  

Juvenile Astrodon bones on display at the Maryland Science Center.

Astrodon had somewhat shorter vertebra in its neck when compared to some of its relatives, like Brachiosaurus.  Based on the fact that most sauropod dinosaurs had about the same number of neck vertebrae, it could be assumed that Astrodon's neck would have been proportionally shorter.  

Astrodon's teeth were spoon-shaped and therefore ideal for scraping leaves off of branches and clipping softer foliage.  Like all sauropods, Astrodon wouldn't have had any teeth in the back of its mouth for chewing.  Rather it would have swallowed plant material whole and possibly ingested small rocks, called gastroliths, to aid in mechanical digestion within the stomach.  

When alive, Astrodon would have shared its environment with other plant-eating dinosaurs, like Tenontosaurus and its larger sauropod relative, Sauroposeidon.  Meat-eating dinosaurs from the same area include Deinonychus, which may have hunted young Astrodon, and the giant Acrocanthosaurus, which very likely would have been able to hunt adults.

References

Carpenter, Kenneth; Tidwell, Virginia (2005). "Reassessment of the Early Cretaceous sauropod Astrodon johnstoni Leidy 1865 (Titanosauriformes)". In Kenneth Carpenter; Virginia Tidswell (eds.). Thunder Lizards: The Sauropodomorph Dinosaurs Indiana University Press. 

d'Emic, Michael D. (2013). "Revision of the sauropod dinosaurs of the Lower Cretaceous Trinity Group, southern USA, with the description of a new genus". Journal of Systematic Palaeontology11 (6): 707–726.

P. Larkin. 1910. The occurrence of a sauropod dinosaur in the Trinity Cretaceous of Oklahoma. Journal of Geology 17:93–98

Saturday, March 27, 2021

Deinonychus: Beast of the Week

Today we will be looking at a well-loved, and extremely important dinosaur.  Check out Deinonychus antirrhopusDeinonychus was a meat-eating dinosaur that lived in what is now the United States, including Wyoming, Montana, Oklahoma, and even parts of the East coast, including Maryland, during the Early Cretaceous Period, between 115 and 108 million years ago.  It was relatively small, measuring about eleven feet long from snout to tail. (about half of that length consisting of tail)  The name, Deinonychus, translates to "Terrible Claw" in reference to the second digit on each of its feet, which possessed an enlarged, crescent-shaped talon, which was retractable, like a switchblade.

Prey's eye view of Deinonychus antirrhopus life reconstruction by Christopher DiPiazza.

Starting in the 1800s, when the first dinosaur was seriously recognized by science, the image of dinosaurs was that of hulking, oafish lizard-like creatures.  That all changed when the bones of Deinonychus were unearthed in the 1960s, however.  It was the first dinosaur that really made paleontologists stop and reassess their views on the way dinosaurs lived by showing signs of being a fast-moving, light-weight creatures that shared more characteristics with birds than with other reptiles.  Since then, many more bird-like dinosaurs have been discovered, of course.  Most people now, especially younger dinosaur lovers, would see small, bird-like dinosaurs as a commodity in their books and toy collections, but one shouldn't forget that Deinonychus was society's first taste of this concept.

Deinonychus skeletal mount on display at the American Museum of Natural History in New York.

When alive, despite its size, Deinonychus possessed weapons which would have made it a formidable predator.  The most obvious were the feet, each possessing a second digit with an almost five inch long "killer claw" which could be held above the ground when not in use to prevent wear, and swung forward for stabbing, when attacking.  Each of the hands was equipped with three long fingers, each tipped with a hook-shaped claw, as well.  Inside the mouth, Deinonychus had many small, blade like teeth, which were serrated.  The jaws of this dinosaur were designed for slicing off bite-sized pieces of meat.  Deinonychus' tail was long (took up about half of its total body length) and had small bony rods running down its length.  We call these structures ossified tendons, which are present in a lot of different kinds of dinosaurs.  They would have made the tail stiff, like a fishing pole, and would have helped the dinosaur make sharper turns while running.  Although only bones have ever been found, it is likely Deinonychus was covered in feathers just like a bird, based on more well-preserved remains of other dinosaurs which were extremely closely related to it and predated it, like Velociraptor and Microraptor

Deinonychus food diagram

There are a few ideas as to exactly how Deinonychus hunted.  The first, and most well-known is that Deinonychus hunted in groups to kill larger prey.  The idea is that these predators could have used their powerful hind legs to jump onto larger dinosaurs and clung on using their front claws and used tails for balance.  Then they would have used their deadly claws on their feet to bicycle kick into their prey's body, essentially disemboweling it until it collapsed.  This pack-hunting idea is supported by an amazing discovery of the larger plant-eating dinosaur, Tenontosaurus, with Deinonychus teeth marks on its bones.  One could argue that there is a strong chance the Tenontosaurus was already dead and that the Deinonychus were merely scavenging it, but bones from Deinonychus were found nearby as well, which many suggest supports the narrative that smaller meat-eaters attacked it, and in self defense the larger plant-eater managed to kill some in self-defense before it died.  It's a cool idea, and has been recreated in art countless times, (Seriously, poor Tenontosaurus' whole identity has been reduced to "Deinonychus food" in most books and other media.) but still really can't be totally proven.  Some who oppose this idea argue that perhaps the Deinonychus were not pack hunters, were all drawn to the plant-eater's dead body, and killed a few of each other as they fought over the meat, which is equally plausible.

The second idea of Deinonychus' hunting behavior delves into its killer claw more deeply.  Believe it or not, many modern birds also actually have an enlarged second digit talon on their feet.  The ones that do, like most hawks and eagles, use this claw to pin down smaller prey (alive or dead) to stabilize it as they tear bite-size chunks of meat off with their sharp beaks.  It is very possible that dinosaurs like Deinonychus could have hunted mostly smaller prey as well, like smaller dinosaurs, baby dinosaurs, and mammals, and used their talons for the same purpose. The video below I took at my job of our Eurasian Hawk demonstrating this technique on a dead mouse.  



Eggs that are believed to have belonged to Deinonychus have also been discovered.  It all started when the rocks from which a Deinonychus skeleton was extracted were examined more closely.  It was discovered that they contained dinosaur eggshells.  The next question was whether or not the Deinonychus was eating the eggs, which could have belonged to another dinosaur, or if it the eggs were its own and it was protecting them.  Soon after, tiny bones, called gastralia, were discovered with the eggshells.  Gastralia, or belly ribs, as they are sometimes called, are found on the underside of a dinosaur's torso.  This suggested that the Deinonychus' chest and belly were in contact with the eggs, and it very well may have been incubating them, much like parent birds do today.  Not only does this support the idea that Deinonychus was guarding its own eggs, it also suggests that Deinonychus was endothermic! ("warm-blooded")  Think about it.  Only an animal that produces its own body heat would brood eggs to keep them warm.  Ectothermic ("cold-blooded") animals, like lizards and crocodiles, rely on the sun, decomposing nesting material, or other outside sources of warmth to incubate their eggs. (There are exceptions, like some pythons who incubate their eggs, creating warmth with muscle friction, but this is an exception, not a norm.)  What a great find!

That is all for this week!  As always feel free to comment below or on our facebook page!

References

Fowler, D. W.; Freedman, E. A.; Scannella, J. B.; Kambic, R. E. (2011). Farke, Andrew Allen, ed. "The Predatory Ecology of Deinonychus and the Origin of Flapping in Birds". PLoS ONE 6 (12): e28964. doi:10.1371/journal.pone.0028964. PMC 3237572. PMID 22194962.

Makovicky, P.J.; Grellet-Tinner, G. (2000). "Association between a specimen of Deinonychus antirrhopus and theropod eggshell". In Bravo, A.M. and T. Reyes. First international symposium on dinosaur eggs and babies,Isona i Conca Dellà Catalonia, Spain, 23–26 September 1999. pp. 123–128.

Maxwell, W. D.; Ostrom, J.H. (1995). "Taphonomy and paleobiological implications of TenontosaurusDeinonychus associations". Journal of Vertebrate Paleontology 15 (4): 707–712. doi:10.1080/02724634.1995.10011256.

Ostrom, John Harold (1970). "Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana". Bulletin of the Peabody Museum of Natural History 35: 1–234.

Ostrom, J. H. (1969). "Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana". Peabody Museum of Natural History Bulletin 30: 1–165.

Ostrom, J.H. (1976). "On a new specimen of the Lower Cretaceous theropod dinosaur Deinonychus antirrhopus". Breviora 439: 1–21.

Turner, Alan H.; Makovicky, Peter J.; Norell, Mark A. (2007). "Feather quill knobs in the dinosaur Velociraptor". Science 317 (5845): 1721. doi:10.1126/science.1145076. PMID 17885130.

Xu, X.; Zhou, Z.; Wang, X.; Kuang, X.; Zhang, F. & Du, X. (2003). "Four-winged dinosaurs from China". Nature 421 (6921): 335–340. doi:10.1038/nature01342. PMID 12540892.

Saturday, February 27, 2021

megalodon: Beast of the Week

This week we're revisiting a VERY popular prehistoric beast that despite its mainstream presence, probably isn't as well understood as lots of people think.  Let's make way for *dunDUn...dunDUN...dundundundundundun...* everyone's favorite giant shark, Otodus megalodon!

Life reconstruction in watercolors of Otodus megalodon by Christopher DiPiazza.

Otodus megalodon (commonly just referred to as its species name, megalodon)  was a gigantic shark that measured over 16 meters (52 feet) long from snout to tail, living from 23 million to as recent as 3.6 million years ago in the Miocene and the Pliocene epochs.  So while this beast never actually was alive at the same time as non-avian dinosaurs, it was around at the same time as primates that were ancestors of modern humans!  (Unless those primates frequently went swimming in the open ocean they would have had nothing to worry about from megalodon, however.) The genus name, Otodus, translates to "ear tooth" because of the shape of the teeth in some members of this genus.  The species name, megalodon, translates to "big tooth" because...look at it.  

As far back as the 1600s, people were finding gigantic triangular fossils and thought they were fossilized tongues from dragons.  Danish scientist, Nicolas Stenos, finally found out they were actually teeth from a gigantic prehistoric shark (just as impressive as a dragon if you ask me).  Since then, megalodon teeth have been discovered on every continent except Antarctica.  Where I currently live in Maryland, there's a site only a bit over an hour's drive from me, in fact, where the public can find their very own megalodon teeth to take home with them.

Nicolas Steno's illustration of megalodon from the 1600s.

 Like all sharks, most of megalodon's skeleton was made of cartilage (same material that is in our noses and ears) instead of bone.  That being said only fossils of its teeth, jaws, and some vertebra have ever been discovered.  Judging by the size of these fossils, however, which includes individual teeth that are almost 18cm (over 7 inches) long, the largest specimens of this shark were estimated to have been almost 16 meters (52 feet) long from nose to tail.  To put it into perspective that's the same size as a modern Humpback Whale.  Even though not much of this shark's actual anatomy is truly known, the teeth themselves are are actually quite common (since sharks tend to shed and replace them a lot).  However, since the teeth and other known elements of this shark are similar in appearance to that of modern Great White Sharks (Carcharodon carcarias) it is possible megalodon could have looked similar to them in life...just a lot bigger.  This being said, megalodon wasn't as closely related to Great Whites as most people think.  In fact, megalodon used to be considered the same genus as Great Whites, Carcharodon, but has since been placed into the genus of extinct sharks, Otodus, instead.  Paleontologists found out that the similarities between megalodon and Great White teeth are likely a result of convergent evolution, not an actual close relationship, and that Great Whites are more closely related to the seemingly different Mako Shark than they are to megalodon.  Great Whites and megalodon appear to have shared a common ancestor much farther back during the Cretaceous period.

Reconstructed mount of megalodon jaws on display at the Baltimore Aquarium in Maryland, USA.

So what was a shark as large as megalodon eating?  Fossil evidence in the form of numerous fossilized whale bones with chew and bite marks on them suggest it was a whale-eater.  It was also likely going after pinnepeds(seals), large fish, and turtles.  Basically megalodon was an opportunistic predator, going after any animal it could overpower, and for an almost 16 meter long shark... that's basically everybody.  This is in part thanks to this shark's incredible biting ability.  It is estimated that an adult megalodon had a bite force between 108,5000 and 182,200 newtons! (24,400 and 41,000lbf)  On top of that power, megalodon's teeth were serrated on the edges, like steak knives, so if it shook its head from side to side after biting, it would have been able to completely slice through fat, muscle, and even bones of large whales.  It is possible megalodon wasn't completely care-free, however, even as an adult.  The similarly sized, and equally monstrous toothed whale, Livyatan lived at the same time and place as megalodon.  These two marine heavyweights were likely competitors and may have also hunted each other depending on which individual was larger than the other in each interaction. 

So why did such a powerful predator go extinct? We may never know for sure but lots of experts feel it may have been a drastic change in environmental temperature that led to its demise.  During megalodon's time on earth, geological activity led to a decrease in global temperature which diminished tropical waters a large shark would thrive in.  A shark like megalodon likely didn't have the adaptations to deal with cooler temperatures, especially at such a large size.  Many modern sharks give birth in shallower, warmer waters, called nurseries.  If megalodon did the same but on a larger scale, there is a chance this climate change event could have eliminated whatever specific places it was using to reproduce, thus also leading to its extinction.  

Lastly I feel it is important to note that despite what you may hear on certain television shows, megalodon is most certainly gone forever.  It's definitely not still out there in the deepest parts of the ocean hiding somewhere.  We know this prehistoric predator was hunting whales in life.  Whales often hang out near the ocean's surface.  We'd see a megalodon by this point if any were still alive.  I'm not sure where the idea of this beast as a cryptid came from, but it's most definitely not based on anything credible.  


Works Cited

Augilera, Orangel A.; García, Luis; Cozzuol, Mario A. (2008). "Giant-toothed white sharks and cetacean trophic interaction from the Pliocene Caribbean Paraguaná Formation". Paläontologische Zeitschrift82 (2): 204–208. 

Bruner, J. C. (Sept.-Oct. 1997). "The Megatooth shark, Carcharodon megalodon: Rough toothed, huge toothed". Mundo Marino Revista Internacional de Vida (non-refereed) (Marina) 5: 6–11

Collareta, A.; Lambert, O.; Landini, W.; Di Celma, C.; Malinverno, E.; Varas-Malca, R.; Urbina, M.; Bianucci, G. (2017). "Did the giant extinct shark Carcharocles megalodontarget small prey? Bite marks on marine mammal remains from the late Miocene of Peru". Palaeogeography, Palaeoclimatology, Palaeoecology469: 84–91. 

Haven, Kendall (1997). 100 Greatest Science Discoveries of All Time. Libraries Unlimited. pp. 25–26. ISBN 1-59158-265-2.

Pimiento, Catalina; Dana J. Ehret, Bruce J. MacFadden, and Gordon Hubbell (May 10, 2010). Stepanova, Anna. ed. "Ancient Nursery Area for the Extinct Giant Shark Megalodon from the Miocene of Panama"

Wroe, S.; Huber, D. R.; Lowry, M.; McHenry, C.; Moreno, K.; Clausen, P.; Ferrara, T. L.; Cunningham, E.; Dean, M. N.; Summers, A. P. (2008). "Three-dimensional computer analysis of white shark jaw mechanics: how hard can a great white bite?"Journal of Zoology276 (4): 336–342. 

Tuesday, January 26, 2021

Tyrannosaurus: Beast of the Week

This week we will be looking at the most famous dinosaur of all time.  Make way for Tyrannosaurus rexTyrannosaurus lived during the Late Cretaceous Period, between 68 and 66 million years ago in what is now Western North America, including Colorado, Wyoming, Montana, South Dakota, Utah, Texas, and parts of Southern Canada.  The genus and species name, Tyrannosaurus rex, translates to "Tyrant Lizard King".  The biggest adult specimen on the fossil record of a Tyrannosaurus measured about forty two feet long from snout to tail, making it the largest known meat-eater from its environment.

Watercolor reconstruction by Christopher DiPiazza of a Tyrannosaurus barfing up some nice predigested meat for its babies.  Yup, those are tiny feathers.  Given the most recent findings confirming Tyrannosaurus had fine scales, these feathers are sparse enough to have still been a possibility.  Also note how the proportions of the babies are leggier and over all more gracile than the adult.

Tyrannosaurus is the most well-known and loved dinosaur of all time.  This is because for a very long time it was by far the largest meat-eating dinosaur known to science.  In more recent history several other meat-eating dinosaurs have been discovered that rival or even surpass the tyrant king in length, but Tyrannosaurus is currently still widely accepted as the most robust.

The head of Tyrannosaurus is iconic, and easily distinguishable from those of other dinosaurs.  Its general shape is somewhat rectangular, and its face, especially near the rear of the jaw, is wider than what you would see in other dinosaurs. Being wider in the back of the jaws suggests that part of the skull could withstand more force, and there were likely powerful biting muscles attached there in life.  Tyrannosaurus would have had strong eyesight, complete with good depth perception, as well as an extremely good sense of smell.  Its nose would have had one of the most acute senses of smell of any animal, alive or extinct, known.  Scientists can tell this by looking at the negative space inside of the skull, where the brain used to be, getting an accurate shape of the brain.  Thanks to this, it can be observed that the parts of the brain associated with sight and smell were proportionally large and well-developed.

Cast of the inside of a Tyrannosaurus' braincase on display at the Sydney Museum.  The large part on the far left side is the olfactory bulbs, the part associated with sense of smell.

The teeth of Tyrannosaurus were larger than those of any other dinosaur (some were a foot long!) and totally unique in form.  Most every other kind of meat-eating dinosaur tooth was either flattened and blade-like, for slicing meat, or pointed, and cone-shaped, for holding on.  The teeth of Tyrannosaurus, however, were not only curved and serrated, but also really thick. (comparable to the shape of bananas actually...pointy, serrated bananas.)  This suggests that Tyrannosaurus teeth were adept at simply puncturing through whatever they bit into, including bone.  Scientists estimate, thanks to computer simulations of the skull of Tyrannosaurus, that it could bite down with over 12 thousand pounds of pressure per square inch, making it the owner of the strongest jaws of any known land animal.  Fossilized dung associated with T. rex even has tiny bits of crushed bone in it, proving this dinosaur had no problem crunching up and eating some bone as it ate.   This makes sense when you consider the animals Tyrannosaurus was coexisting with and feeding on.  As the result of one of the most extreme evolutionary arms races in natural history, dinosaurs like Triceratops and Ankylosaurus, both of which coexisted with Tyrannosaurus, were more-or-less the largest and most heavily-armored forms of each of their families.  Tyrannosaurus, in turn, was the largest and most powerful of its family, the tyrannosaurids.  In fact, there is direct evidence of Tyrannosaurus having fed on dinosaurs like Triceratops, despite the solid-bone frill, thanks to Tyrannosaurus teeth found embedded in Triceratops bones.  Theres even more evidence of Tyrannosaurus pursuing and feeding on the duck-billed dinosaur, Edmontosaurus, including a healed bite wound.  This proves that the plant-eater escaped a Tyrannosaurus attack, implying the tyrant could have been both a scavenger and an active predator.  

The rest of Tyrannosaurus' body was interesting too.  It is well-known for its proportionally small arms, which are actually about the same length as adult human arms!  Despite being the butt of many jokes, Tyrannosaurus' arms were actually quite strong.   Paleontologists estimate, by closely studying the arm bones and predicting the amount of muscle that would have attached to them in life, that each one of Tyrannosaurus' arms could lift over four hundred pounds of weight!  The function of the tiny arms, which were tipped with two functional fingers and claws, is still a mystery.  Some paleontologists guess that they would have helped the dinosaur get up from a resting position.  It is also possible that they could have aided in holding on while Tyrannosaurus mated. (But then again, both sexes appear to have had the same arms so do with that information what you like.). I've also heard some paleontologists suggest the arms were adaptations for carrying food to safer areas away from a kill, or maybe they even carried nesting material with them? 

Tyrannosaurus rex skeletal mount on display at the American Museum of Natural History in New York.  This mount was the first ever erected of T. rex, and actually is made up of bones from two individuals, Frankenstein style!

The legs and tail of Tyrannosaurus also had to be extremely powerful.  They would need to be in order to balance out how robust the front end of the animal was.  Because it was so massive, Tyrannosaurus likely wasn't a very fast runner as a mature adult, probably not even being able to break twenty miles per hour at top speed, but at the same time most of the large dinosaurs it would have hunted were running about that same speed or slower, anyway.  At top speed, because of its immense weight, Tyrannosaurus likely always would have had one foot on the ground, so it would have been more of a really scary power walk than a true run.  

Interestingly enough, it is the feet of Tyrannosaurus that holds the answer to where Tyrannosaurus' group, the tyrannosaurids, fall on the dinosaur family tree.  The feet of all dinosaurs each contain three bones, called metatarsals.  (Humans have five metatarsals in each foot.)  Most large theropod dinosaurs, like Allosaurus, for instance, have all three metatarsals roughly the same length, neatly positioned next to each other in the foot.  In the more bird-like theropods (including birds), called the coelurosaurs, the middle metatarsal of each foot is a little shorter than the surrounding two, forming an upside down V shape when looking at the skeleton.  Well, Tyrannosaurus feet show this same shortened middle metatarsal.  At first this may seem odd that the gigantic Tyrannosaurus is more closely related to dinosaurs, like Archaeopteryx and parakeets, than to other giant carnivores, like Allosaurus or Spinosaurus, but remember that Tyrannosaurus' older relatives are smaller and smaller the farther back in time you go.  Check out Eotyrannus or Guanlong for examples.  So even though Tyrannosaurus was a particularly gigantic dinosaur, it was more of an exception among the many more gracile tyrannosauroids that it was most closely related to.

Tyrannosaurus skeleton foot.  Notice the upside down V formed by the shorter middle foot bone.

Paleontologists have been unearthing and studying specimens of what are believed to have been from juvenile Tyrannosaurus within recent years.  What is interesting about these specimens is that they don't look like just smaller versions of the adult Tyrannosaurus.  Their legs are longer proportionally, suggesting they were fast runners at that age. They also had different teeth, which were flatter and more blade-like than the giant banana-teeth of the adults.  The number of teeth in their jaws is even different.  This tells us that Tyrannosaurus may have been filling a different predatory ecological niche as a juvenile than as a mature adult.  Perhaps the younger Tyranosaurus were better at chasing down and eating more fast moving prey like Ornithomimus or Pachycephalosaurus and then graduated to hunting more heavily armored, but slower Triceratops and Edmontosaurus, when they were bigger and stronger?  

Juvenile Tyrannosaurus skeleton nicknamed "Jane" on display at the Burpee Museum of Natural History in Illinois.  Note how the skull is not as robust as an adult's and how the legs are proportionally much longer.

Several small patches of skin from T.rex and some of its closest relatives have been found.  The largest of these is about the size of a playing card and is from the bottom of the tail.  The others are from the neck and the hips.  All of these skin patches show small pebbly scales.  And when I say small, I mean each scale is about a millimeter in diameter, comparable to the texture of a basketball.  That being said, keep in mind Tyrannosaurus was a coelurosaur, the same group of theropods that includes modern birds.  In fact, coelurosaurs are known on the fossil record to possess feathers pretty much across the board.  At least one example of every major branch of this group of dinosaurs has been found with them, including Tyrannosaurus' branch, called the tyrannosauroids.  So did Tyrannosaurus have feathers too?  Well, since these scales are so small and close together, it doesn't appear that there would have been room for feathers to have been growing from between them in life.  So if Tyrannosaurus did have feathers, they were either very sparse, or concentrated to parts of the body where these skin patches were not.  There are some who insist Tyrannosaurus and its closest relatives in the tyrannosaurid group (not to be confused with the slightly broader group they were nestled in where there is proof of feathers, the tyrannosaurOIDs), more likely didn't have feathers at all. However, this claim would make them an evolutionary anomaly, considering the rest of its known family tree had them. 

Photographs and diagrams showcasing the known scales of Tyrannosaurus from Bell's 2017 paper.  To give you an idea as to how small these patches are, the black scale bars for the top two images is 5 centimeters. (neck and hips)  The scale bars for the bottom images (tail) are 10 centimeters.

That is all for this week!  As always feel free to comment below!

References

Bakker, R.T.; Williams, M.; Currie, P.J. (1988). "Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana". Hunteria 1 (5): 1–30.

Bates, K.T & Falkingham P.L. (2012). Estimating maximum bite performance in Tyrannosaurus rex using multi-body dynamics. Biological Letters.

Bell, P. R., Campione, N. E., Persons, W. S., Currie, P. J., Larson, P. L., Tanke, D. H., & Bakker, R. T. (2017). Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution. Biology Letters, 13(6), 20170092.

Carpenter, Kenneth; Smith, Matt (2001). "Forelimb Osteology and Biomechanics of Tyrannosaurus rex". In Tanke, Darren; Carpenter, Kenneth. Mesozoic vertebrate life. Bloomington: Indiana University Press. pp. 90–116.

Carr, T.D.; Williamson, T.E. (2004). "Diversity of late Maastrichtian Tyrannosauridae (Dinosauria: Theropoda) from western North America". Zoological Journal of the Linnean Society 142 (4): 479–523.

Hutchinson, J.R. (2004). "Biomechanical Modeling and Sensitivity Analysis of Bipedal Running Ability. II. Extinct Taxa" (PDF). Journal of Morphology 262 (1): 441–461.

Stevens, Kent A. (June 2006). "Binocular vision in theropod dinosaurs". Journal of Vertebrate Paleontology 26 (2): 321–330.

Meers, Mason B. (August 2003). "Maximum bite force and prey size of Tyrannosaurus rex and their relationships to the inference of feeding behavior". Historical Biology: A Journal of Paleobiology 16 (1): 1–12.

Xu, X.; Wang, K.; Zhang, K.; Ma, Q.; Xing, L.; Sullivan, C.; Hu, D.; Cheng, S.; Wang, S. et al. (2012). "A gigantic feathered dinosaur from the Lower Cretaceous of China" (PDF). Nature 484 (7392): 92–95.

Sunday, January 10, 2021

Saurosuchus: Beast of the Week

This week we will be checking out an amazing giant predator that was a neighbor to (and likely hunted) the earliest dinosaurs.  Make way for Saurosuchus galilei!

Saurosuchus was a meat-eating reptile that lived during the late Triassic period, about 231 million years ago, in what is now Argentina.  From snout to tail an adult would have measured about eighteen feet long, but some estimate this beast may have been able to grow even larger.  The genus name, Saurosuchus, translates to "Lizard Crocodile".   

Saurosuchus overpoweriing the early dinosaur, Herrerasaurus.  Watercolor reconstruction by Christopher DiPiazza.

Despite its appearance, Saurosuchus was not a dinosaur.  It was more closely related to modern crocodilians than it was to dinosaurs.  Specifically, it belonged to a group of reptiles called prestosuchidae.  Prestosuchids shared common ancestors with other pseudosuchians (broad group that includes modern crocodilians) like the poposauroids (like Shuvosaurus) and the rauisuchians (like Postosuchus). Prestosuchids were generally large land predators that usually walked on all fours and had fully erect posture with regards to their limbs, rather than a more sprawling posture, like modern lizards, or semi-sprawling, like modern crocodilians.  

Saurosuchus had a large robust skull with long, curved, serrated teeth, ideal for slashing through meat.  It had pronounced ridges on the back of its skull, implying there were large muscles attached there in life, and its neck vertebrae were relatively short and robust, which would have been an adaptation for absorbing impacts and strain in life.  This implies Saurosuchus was likely using its jaws and neck for rough activities, like overpowering struggling prey and/or forcefully dismantling carcasses as it ate.  

Saurosuchus skeletal mount on display at the Mori Arts Gallery in Japan.

Saurosuchus likely walked on all fours most of the time but probably could have reared up on its hind legs or even ran and walked short distances as a biped.  It also had rows of small bony plates, called osteoderms, running down the length of most of its body.  These may have been an adaptation for protecting the animal from bites from members of its own species, like chain mail armor, if there was any kind of intraspecies combat or cannibalism.  They also could have helped camouflage the animal better by breaking up its shape, or could have simply been for display.  (or maybe a combination of more than one of those things for all we know)

Saurosuchus was the largest and most powerful known predator from its environment, and likely could have hunted every other animal it coexisted with during its time on the planet.  Its kind would eventually go extinct and make way for more derived pseudosuchians, like the rauisuchians, and then eventually later kinds of dinosaurs, however.  

References 

Alcober, O. (2000). "Redescription of the skull of Saurosuchus galilei (Archosauria: Rauisuchidae)". Journal of Vertebrate Paleontology20 (2): 302–316.

Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades" (PDF)Bulletin of the American Museum of Natural History352: 1–292. 

Reig, O. A. (1959). "Primeros datos descriptivos sobre nuevos arcosaurios del Triásico de Ischigualasto (San Juan, Argentina)"Revista de la Asociación Geológica Argentina13(4): 257–27.

Sill, W. D. (1974). "The anatomy of Saurosuchus galilei and the relationships of the rauisuchid thecodonts"Bulletin of the Museum of Comparative Zoology146: 317–362.

Trotteyn, M.J.; Desojo, J.; Alcober, O. (2011). "Nuevo material postcraneano de Saurosuchus galilei (Archosauria: Crurotarsi) del Triásico Superior del centro-oeste de Argentina"Ameghiniana48 (1): 13–27. 

Saturday, December 19, 2020

Interview with Paleontologist: David Wilcots

David Wilcots is a geologist, paleontologist and artist living in Philadelphia where he grew up.  Mr. Wilcots is a registered professional geologist in Pennsylvania and Delaware.  He earned his Bachelor’s degree in geology at Temple University in Philadelphia, and Master’s degree in geology from Fort Hays State University in western Kansas. His master’s thesis was entitled, “Functional Morphology, Phylogeny and Paleoecology of the North American Miocene Rhinoceros, Aphelops”.  

Wilcots has over 29 years experience working as an environmental geologist and has worked for several environmental/engineering consulting companies in the Philadelphia region.  Currently David is the senior geologist for Sci-Tek Consultants, Inc., an engineering and environmental consulting company in center city Philadelphia.  

Mr. Wilcots is also a volunteer paleontologist at the Academy of Natural Sciences museum in Philadelphia in its Dinosaur preparation lab. For nine days each summer David is an expedition paleontologist in Wyoming for the Burke Museum of Natural History and Culture of Seattle, Washington.

David has also been an expedition paleontologist for the: 

 • Utah Geological Survey, Salt Lake City, Utah 

• The University of Utah Museum, Salt Lake City, Utah, and the 

• American Museum of Natural History, New York, NY.

He has given presentations about fossils at schools and has presented at S.T.E.M. programs for young people.  In 2012 David was featured on the Discovery Channel Global Education Partnership DVD entitled “Life in the Age of the Dinosaurs”.  In December of 2014 David launched the website for Dinosaurs Fossils and Adventures; DinosaursFA.com which is an on-line paleontology website for ages 8 to 18. In February 2020 he was a S.T.E.M. presenter for the Franklin Institute’s Color of Science Symposium.

Question 1: What was your earliest sign of interest in paleontology that you can remember?


DW: When I was four my parents took me to the American Museum of Natural History in New York City.  I saw the dinosaurs there and was just transfixed.  It was out of this world for me. I've been excited about dinosaurs and fossils ever since.  


Question 2: Did you have anyone who served as a role model when you were younger?  Do you still have any now?


DW: I did not have anyone that served as a role model for paleontology or geology.  I had role models in my parents when it came to how to learn and talk to people and overall how to be professional.  They were both very supportive of my interests- my brother too.  I did not grow up wanting to be like a certain paleontologist who was out there, though.  In my teenage years I didn't know any geologists or paleontologists except for Louis Leakey in in National Geographic Specials.


Question 3: You are a geologist full time.  Tell us more about your work and what its all about. 


DW: I am an environmental geologist.  I work for an engineering/environmental consulting firm. (Sci-Tek Consultants, Inc.)  In my capacity at this firm I manage environmental projects, which includes environmental site assessments, soil and groundwater sampling, borehole drilling supervision, and sometimes air and rock sampling.  I sample these media for environmental quality to test for potential contamination and to report on site contidions.


Question 4: How much of your work in geology and paleontology overlap?

DW: My job as an environmental geologist does not overlap with paleontology.  However, when I'm doing paleontology, I need my knowledge and experience as an geologist to do it effectively.  Geology allows me to read the rocks and strata that I see.  


Question 5: Was there anything you did or learned as you were on your way to your current career that you feel got you to where you are?  What sort of field experience, a class, networking with the right people, or possibly something different?


DW: My interest in geology probably kicked in during my teenage years.  Going on field trips and stopping along the highway to look at rocks fueled my fire and inspiration for geology going.  I also made a point to go to a lot of museums and as I learned more, my interests in both geology and paleontology grew.  I also watched a lot of science-based TV, like National Geographic, NOVA, Wild Wild World Animals, Marlin Perkins' Wild Kingdom, Jacques Cousteau, and several other shows kept me inspired.  


Question 6: Are the fields of paleontology and geology different now than from when you started as far as you can tell?  What would your advice be to anyone trying to make a career in paleontology (or science in general)


DW: As for geology, ground-penetrating radar technology has improved. Paleontology, however, has some newer technology, like 3-dimensional printing that has really changed the field.  You can shrink giant specimens down or expand tiny specimens up.  You can also make copies of specimens.  Twenty or thirty years ago, making copies of specimens was a long and arduous process.  3D printing has made is much easier to study fossils as well as communicate and work with a team.  You can simply send a file to someone on the other side of the world and they can reproduce it.  


Question 7: What was or is your favorite project so far? (geology or paleontology)


DW: For paleontology it would be when I was working summers in southwestern Wyoming with John Alexander with the AMNH and later the Burke Museum in Seattle.  He was looking for middle Eocene age fossils. The rocks there are about 47 million years old and the faunal variety was incredible.  We found fossil primates, early carnivores that preceded dogs and cats, rodents, birds, turtles, crocodiles, rhinos, tapirs, and large herbivores like titanitheres.  This was a very interesting time in earth's history because there were archaic animals living side by side with the ancestors of the animals we have now.  There were ecosystems dominated by browsing herbivores which isn't the case now since most modern mammalian ecosystems now are dominated by grazing herbivores.  There was a myriad of condylarths, hoofed mammals whose connection to modern mammals is still unknown.  That part of North America (Wyoming) was also home to at least three kinds of primates.  The biggest one was about the size of a house cat, the medium-sized one was about the size of a squirrel, and the smallest was the size of a mouse.  The environment had to be rich enough and have a forest canopy expansive enough to support primates, which is totally unlike anything in the United States today.  


For geology my favorite experience was hiking the Grand Canyon top to bottom to top in one day.  That was just stunning. 


Question 8: Do you have a favorite destination when it comes to fossils?  Why?


DW: Southwestern Wyoming for reasons stated above.


Question 9: You work out of Philadelphia, a major city.  Most people imagine open wild places when they think of fossils and geological formations.  What do you think people should know about the deep time history behind Philly?


DW: The bedrock in Philadelphia is hard metamorphic rock thats around 500 million years old, and devoid of fossils.  On top of that bedrock is two kinds of sediments. One is about 3 million years old and the other is only about 17 thousand years old.  These may be devoid of fossils also.  So there is a huge span of time missing from Philadelphia's observable geologic history. 


Question 10: A popular image of paleontologists is that they are constantly out in the field digging up fossils, which is true sometimes.  What people don’t realize is that a lot of paleontology work is conducted in a lab as well.  In your experience how much time have you spend in the lab and in the field?  What do you prefer?


DW: I prefer fieldwork.  I like discovering new things and being the first to see them.  I have done lab work, like cleaning and reassembling specimens.  I've also cataloged and organized specimens.  That's all fun, but I ultimately prefer being out finding and excavating fossils.  The fever for discovery is real.  


Question 11: You also run a website aimed to educate young people about paleontology.  Can you tell us more about that?


DW: I started the website to make paleontology more accessible to young people.  Some videos are on there as well as many photos that show viewers different aspects of paleontology.  One of my main goals here is to show that paleontology more than just dinosaurs. The website also features girls and boys of all colors in an inclusive environment working in the field, so all viewers can see themselves in this context.  


Question 12: Are there any fossils you’d like to work with that you haven’t yet?


DW: YES.  Shovel-tusked elephant!  I think an elephant with four tusks, like the gompotheres or Platybellodon is so cool.  I'd also like to work with pterosaurs and giant snake, like Titanoboa.  There were probably snake fossils around when I was working in Wyoming, but their bones are so delicate, they are hardly ever found.  Given how many small and medium sized mammals were out there that could serve as prey, paired with the hot, humid climate, there HAD to be large snakes around back in the Eocene.  It's just a matter of finding one.


Question 13: Do you ever get criticized on any of your work?  How do you handle it?


DW: Talk it out. Most disagreements I've experienced have been about whether or not to take a fossil out of the ground.  Collecting fossils early in the field schedule can sometimes be favorable because it seems like a good specimen and we have the means to collect it.  However, sometimes when it's early in the field season we decide to leave it there in favor of possibly finding an even better specimen int he field.  Sometimes we ultimately decide not to collect a particular fossil because doing so will be too much work/effort, or they're just too close to a major road to safely do so.  


Question 14: A common idea is that paleontology is just a “for fun” science, with no real impact or noticeable effect that helps the world.  Do you think paleontology has a bigger part to play to than this?  How?


DW: Yes, paleontology absolutely plays a bigger part.  First of all, the world needs more paleontologists because we need to understand how life on this planet developed over geologic time.  Second, and maybe even more importantly, is that paleontology is a gateway science for really young people to get interested in other sciences.  The world needs more doctors, energy engineers, and waste management engineers.  Toddlers don't roll out of bed interested in, let alone understanding, these things, but they are interested in paleontology.  If you want more people in these important science fields, medical, and engineering fields, paleontology is the way to get it.  Paleontology teaches kids how to think scientifically, how to collect and interpret data, how to form a hypothesis and so on.  Most kids interested in paleontology don't stick with paleontology.  They usually go on to other sciences as they get older and progress in school.


Question 15: Who was the first paleontologist you met?  How was that interaction?


DW: I first met a paleontologist when I was volunteering at a museum when I was eighteen years old.  Later on as I kept my interest, however, I did meet some really incredible people in the field.  John Alexander, from the Burke Museum in Seattle, Jim Kirkland, of the Utah Geologic Survey, and Richard Zakrzewski at Fort Hayes State University in Kansas (now retired) are probably the top three when it comes to people who have inspired me.  Also Christian Sidor.  I med John Alexander and Don Prothero at the AMNH when I was measuring Miocene rhino specimens for my graduate research.  


Question 16: What is your favorite prehistoric animal?  Was it different when you were younger? 


DW: When I was a really little kid my favorite was Brontosaurus. Now my favorite dinosaur might be Kentrosaurus. (which I chose for the logo on my website). This is probably because when I was younger my dad got me a book about dinosaurs and when I opened the book and noticed on the inside cover was a world map with dinosaurs illustrated over each continent.  I remember seeing what I now know was Kentrosaurus (which wasn't labeled in this book) placed over central Africa.  I remember immediately looking through the rest of the book for this awesome spiky dinosaur, but couldn't find it!  They mentioned Stegosaurus, of course, but it didn't match the image on the inside cover.  I felt ripped off.  When it comes to prehistoric mammals, I love rhinos, saber-toothed cats, and four-tusked elephants, like Stegotetrabelodon.  

Kentrosaurus by Christopher DiPiazza

Question 17: If you could use a time machine to go back and pick only one prehistoric animal to bring back from history and observe alive and in person, which would it be and why?


DW: Quetzalcoatlus.  I want to see an animal with a 45-foot wingspan take off.  I would love to see how it does that.  If you ever watched a large heron or eagle takeoff it is not easy.  I'm so curious to see how these gigantic pterosaurs achieved the same thing.  I'd also love to see a sauropod migration.  I try to imagine a herd of 30-40 ton animals all together in a group going back to their ancestral lands.  It must have been a sight to see.  


Question 18: Back to the time machine.  This time you can go back to any place and time period and have a look at what the environment was really like.  Which one would you pick and why?


DW: I'd have to go back and look at Antarctica when it was tropical.  I'd also want to see Antarctica when it was in transition from temperate to boreal.  There must have been a whole community of miocene mammals there that dealt with snow seasonally.  We know very little of this part in earth's history.  It would have had about 20 million years worth of evolution there we have never seen any trace of.  Marsupials with thick fur?  Cold-adapted monotremes?  Who knows?  


Question 19: Which is your favorite museum?  Why?


DW: The American Museum of Natural History in New York.  It has almost everything.  If you're looking for the biggest prehistoric science buffet (literally and figuratively) this is the place to go.  I could go there every week and always learn new things.  


Question 20: What hobbies do you have?  (Don’t have to be paleo-related.)


DW: I like to do pen and pencil illustration and woodworking.  The logo of my website of Kentrosaurus I illustrated.  I like to bake and am a foodie as well.


Gritty...

Question 21: What prehistoric beast do you think shares the most in common with Gritty?


DW: Back in the pliocene or late miocene there were probably species of primates that had long hair.  I refuse to believe that the longest haired primates alive today are the record holders.  So if there was a prehistoric monkey with extra long orange hair, that would be a reminder of Gritty.