Sunday, November 27, 2016

Tarbosaurus: Beast of the Week

This week we will be checking out a huge tyrannosaurid.  Enter Tarbosaurus bataarTarbosaurus was a large meat-eating dinosaur that lived in what is now Mongolia and China during the late Cretaceous Period, about 70 million years ago.  The largest known individuals infer that they could have been just a little smaller than the largest known Tyrannosaurus, at about 39 feet long from snout to tail.  The genus name translates to "Alarming Lizard".  When alive, Tarbosaurus would have shared its habitat with (and maybe hunted) fellow theropods, Deinocheirus and Therizinosaurus, as well as the hadrosaur, Saurolophus.

Tarbosaurus and young...and lunch life (except lunch...lunch is dead) reconstruction by me.

Tarbosaurus was an extremely large tyrannosaurid, second largest known, right behind Tyrannosaurus.  These two genus are very similar in appearance at first glance, but key differences are present.  In fact, the two may not be as closely related to each other as they each might be to other kinds of tyrannosaurids that are known.  Starting at the head, Tarbosaurus had a laterally slim head.  It's eye sockets were primarily facing sideways, so it wouldn't have had much depth perception.  Thanks to scans of the inside of Tarbosaurus' skull, and looking at the shape of the brain case, scientists can infer that Tarbosaurus would have had a great sense of smell and hearing, but it was lacking in the sight department.  It likely would have hunted relying on its sense of smell mostly, unlike T. rex, which had more forward-facing eyes.  Tarbosaurus' teeth were sharp and curved for crushing and tearing flesh and bone, but weren't as proportionally large.  The actual jaws were less flexible than those of most other tyrannosaurids.  It possessed two extremely short arms with two fingers on each hand.  The arms of Tarbosaurus are proportionally the tiniest out of all tyrannosaurids. (Yes, they were even smaller than T. rex's.)  When examined more closely, it was discovered that the arms of Tarbosaurus commonly endured stress factors, meaning they likely weren't completely useless in life.  Some have suggested they aided in taking down prey but personally I feel they may have had some role when it came to mating.  We may never know!

Tarbosaurus skeletal mount on display at the Cosmacaixa Museum in Barcelona, Spain.

There are a relatively large number of Tarbosaurus specimens on the fossil record.  Among these are small juveniles.  Thanks to these individuals, we know that Tarbosaurus was proportionally leggier when it was little, bulking up as it aged.  The teeth were also more blade-like, and less robust when they were young.  Tarbosaurus probably filled different ecological niches as it aged, preying on smaller, faster prey when it was younger, and moving on to bigger game as it matured.  In fact, thanks to bite marks on bones, we can be fairly certain that an adult Tarbosaurus was eating at least Deinocheirus, the giant, flat-billed, ornithomimid.

Juvenile Tarbosaurus skull

Lastly, we have actually found clues as to what Tarbosaurus' skin was like...well at least parts of it.  A large individual had a small patch of skin (sadly we don't know exactly where because it was messed with by fossil poachers) that shows small, round scales.  These scales are each only about two millimeters wide in diameter.  In addition, a Tarbosaurus footprint was discovered, that showed evidence of being scaly as well.  Because of this evidence, many folks tend to argue that Tarbosaurus and its close relatives wouldn't have had feathers in life.  This is flawed, however, since even modern birds possess similar textures on their own feet.  Plus, other fossilized non-avian dinosaurs have been unearthed with evidence of both scales and feathers on other parts of their bodies than the feet.

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

References

Currie, Philip J.; Badamgarav, Demchig; Koppelhus, Eva B. (2003). "The First Late Cretaceous Footprints from the Locality in the Gobi of Mongolia". Ichnos. 10: 1–12.

Hurum, Jørn H.; Sabath, Karol (2003). "Giant theropod dinosaurs from Asia and North America: Skulls of Tarbosaurus bataar and Tyrannosaurus rex compared" (PDF). Acta Palaeontologica Polonica. 48 (2): 161–190.

Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331-336.

Saveliev, Sergei V.; Alifanov, Vladimir R. (2005). "A new study of the brain of the predatory dinosaur Tarbosaurus bataar (Theropoda, Tyrannosauridae)". Paleontological Journal. 41 (3): 281–289.

Tsuihiji, Takanobu; Watabe, Mahito; Tsogtbaatar, Khishigjav; Tsubamoto, Takehisa; Barsbold, Rinchen; Suzuki, Shigeru; Lee, Andrew H.; Ridgely, Ryan C.; Kawahara, Yasuhiro; Witmer, Lawrence M. (2011-05-01). "Cranial Osteology of a Juvenile Specimen of Tarbosaurus bataar (Theropoda, Tyrannosauridae) from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia". Journal of Vertebrate Paleontology. 31 (3): 497–517.

Friday, November 25, 2016

Dinosaurs Among Us at the American Museum of Natural History

It's the day after Thanksgiving.  Many people cooked and ate a dinosaur last night.  This is nothing new.  I've been saying it for years.  Yet many people are still blindsided by the fact that birds are, in fact, literal dinosaurs.  (I just graded my tenth grade's vertebrate evolution quizzes...trust me.)  Finally, however, there is something that is available to ANYONE who happens to find themselves in New York City (at least until January) that not only educates, but shows proof of this amazing connection between modern birds around us and the most influential animals we never knew.  Let's go check out the American Museum of Natural History's best (I'm biased.) temporary exhibit, called Dinosaurs Among Us.

I had the privilege of being taken in as an explainer for this exhibit during the spring and summer of this year before I had to move out of New York.  When I first stepped in for the training walkthrough, the amount of sheer information was almost overwhelming, even for a museum.  Essentially this exhibit has a two main messages.  The first is to explain, on a broader sense, by using dinosaurs as the model, how evolution works.  The second is to bring home the fact that birds are dinosaurs, by the use of many awesome physical pieces of evidence, some of which have never been on public display before.

One of the life-sze Microraptor models hanging from the ceiling.  They have been painted glossy black-blue in accordance with the preserved melanosomes in their fossilized feathers.

When you first walk in you are greeted by life-sized life reconstructions of several of the keynote dinosaurs featured in the exhibit.  Most important is probably Citipati, due to the sheer amount of fossil material that has been found, and the fact that the American Museum of Natural History does a lot of field work in Mongolia, where this dinosaur was native to, and therefore has access to a lot of its fossils.  The largest and most dramatic model, however, is definitely Yutyrannus.  To my knowledge, a life-sized life reconstruction of this monster has never been made before this, and it looks great. Many of the life reconstructions actually feature real bird feathers, as well.

My first interaction with the Yutyrannus was a bit rocky.  We're cool now, though.

One key connection between birds and other dinosaurs is the act of nest building.  This exhibit features several spectacular fossils of nests and eggs that were laid by dinosaurs millions of years ago.  The manner in which these eggs were laid actually gives us clues as to just how closely related a species dinosaur mother was to her modern relatives.

Life-size replica of a Gigantoraptor nest on display in Dinosaurs Among Us.  Yes, you're allowed to stand in it.
One very interesting way to tell is whether or not the eggs in a dinosaur's nest were laid in pairs.  Check out this replica of a Gigantoraptor's nest above.  See how the eggs are spaced in twos?  That means that the mother of these eggs had two functioning ovaries, and was producing an egg from each of them.  This is in contrast to nests like...


This, laid by a troodontid, called Byronosaurus.  The eggs aren't arranged in pairs.  This looks more similar to a clutch of eggs laid by a modern bird.  This is because modern birds only have one functional ovary, and therefore only lay one egg at a time, resulting in this arrangement.  (Fun fact: They have two ovaries as an embryo, but lose one as they develop.  This tells us that they evolved from dinosaur ancestors with two.) We used to think this was an adaptation for lightness so they could fly...but here are some non-avian dinosaurs that didn't fly...and went extinct that way.

Telling you just how close a particular non-avian dinosaur is related to modern birds is a constant theme throughout this exhibit.  In fact, under each specimen, there is a tiny infograph, modeled after a barometer, with the needle pointing somewhere between the earliest ancestral dinosaur and modern birds.

Dino-Bird-o-meters are all over this exhibit.  In this case, it is telling us that Yutyrannus, a tyrannosauroid, is more closely related to modern birds than it is to many other kinds of dinosaurs.

After eggs and nests the exhibit looks at the actual anatomy of different dinosaurs, especially the bones.  As with single ovaries, hollow bones was another feature we used to think birds evolved specifically for flight.  Since then we have learned that this was also not the case.  Large dinosaurs, like Allosaurus, demonstrated here, and even gigantic sauropods, had hollow bones.  We now think this was a sign of having a more efficient one-way respiratory system that birds retain today.  When a bird breathes air into its lungs, it doesn't simply get exhaled out the same way it went in.  It goes into more chambers throughout the body, including ones connected to hollow cavities in the bones.  Birds today use it to help them fly better, most likely, but prehistoric dinosaurs probably used it for other reasons, like getting oxygen throughout their huge bodies more efficiently.  We have also found similar respiratory systems in modern crocodilians and even some kinds of lizards so...yea definitely not a specific flight adaptation.

This is a broken piece of an Allosaurus leg bone,displayed next to the bone of a modern bird.  The hollow inside has since been fossilized with a different mineral from the actual bone.

Having fused clavicles, or a wishbone, was another feature previously thought to be exclusive to birds...until it started popping up in the fossil record in dinosaurs like Velociraptor.  This exhibit has an awesome articulated Velociraptor specimen on display with the wishbone clearly visible.

Beautifully articulated Velociraptor specimen.  You can see the shallow v-shaped clavicle at the base of the neck.

My favorite specimen in this exhibit would be the Tyrannosaurus wishbone, however.  That's right, T. rex had a wishbone, just like that turkey you ate.  To drive the point home even harder, it is displayed in a case surrounded by the wishbones of various modern birds.

T. rex wishbone.  My favorite piece in the exhibit.

Finally the exhibit goes from internal anatomy, like bones, to external anatomy, like skin and feathers. A myriad of specimens showcasing visible preserved feathers on fossilized bodies is showcased here from the curious quill-like structures of Tianyulong...

Tianyulong cast on display, complete with bristles on the back.

To the extremely feathered, Confuciusornis, in all its plumed glory.

Confuciusornis.  Just one of many feathered specimens on display at Dinosaurs Among Us.

At the end of this exhibit, a common question we receive from guests is "So what defines a bird?" This is a great question.  Yes, birds are dinosuars...but not all dinosaurs were necessarily birds, of course.  It's like saying a Ferrari is a car, but the car I drove to New Jersey to see my family today sure as heck wasn't one!  So what they are really asking is where in the fossil record do we draw the line between birds and non-avian dinosaurs?  What combination of features can we confidently say that all birds must have to be considered a bird?


Archaeopteryx fossil.  For a long time this was the only feathered fossil known to science.  Because of that, Archaeopteryx was referred to as the "first bird" when in reality the line between "bird" and "other dinosaurs" is too blurred determine where one stops and the other begins.

The answer to this is as frustrating as it is beautiful; We don't know!  And to put it bluntly...we shouldn't really care.  Nature has nothing to do with which label we put on which organism.  They evolve to survive and the process just is what it is.  Labeling something a bird based on an anatomical milestone just can't flow with what actually happens.  The amazing side of this seemingly frustrating coin is that this means that the fossil record for non-avian dinosaurs to birds is rich with plenty of specimens to learn from for years to come.  This is in harsh contrast to as little as a few decades ago when all we had to work with as far as feathered, birdlike dinosaurs were concerned, was good old Archaeopteryx, once considered "the first bird" and now just one of many feathered, birdlike dinosaurs.

If you have an interest in paleontology, birds, or nature in general PLEASE visit this exhibit if you have not already.  The American Museum of Natural History has been a prominent part of my life since I was born.  I've seen lots of fantastic temporary exhibits come and go.  That being said, this exhibit blew me away.  I purposely didn't write about and include photos of everything in there.  In fact, I only showed you a smaller portion of what this exhibit has to offer to further encourage you to go out and see it in person for yourself.   


Sunday, November 6, 2016

Gorgonops: Beast of the Week

This week we will be checking out a prehistoric beast with an even beastlier name!  Let's look at Gorgonops!  Gorgonops was a creature that lived in what is now Southern Africa during the late Permian era, between 260 and 254 million years ago.  It was a synapsid, which means it belonged to the same group as mammals, yet it also shared characteristics with animals we consider reptiles. Because of this, Gorgonops and its close relatives are also informally referred to as "mammal-like reptiles".  The much more famous, Dimetrodon, is an earlier example of a synapsid that is also a "mammal-like reptile"s.  The largest Gorgonops measured about six feet long from snout to tail and would have eaten meat when alive.  Within the genus, there are a few species of Gorgonops recognized by science.  Gorgonops torvus was the first to be discovered and is probably the most well-understood because multiple specimens of it have been found.  Gorgonops whaitsi was larger than G. torvus and had a more robust snout.

Gorgonops whaitsi life reconstruction by Christopher DiPiazza.

Gorgonops' genus name translates to "gorgon face" in reference to the gorgon, a monster from Greek mythology that resembled a woman with snakes for hair.  According to the legend, looking directly at a gorgon's face would turn a person to stone.  (Medusa was the most famous gorgon.)  In contrast to this, Gorgonops possessed extremely long, sharp teeth in the front of it's mouth, which gave its skull a particularly menacing look.  Because of this, it was named in honor of the mythical creature.  It is unlikely that looking at an actual Gorgonops would turn anyone to stone, however, and snakes wouldn't evolve for tens of millions of years after Gorgonops' time.

Kinda like that...but not.

The first Gorgonops was discovered and named during the 1800s by a man named Richard Owen. (Somewhat Unrelated Fun Fact: Mr. Owen also coined the term "dinosaur")  Since then, several other kinds of related animals from the same family have been unearthed.  Since Gorgonops was the first, the name of this family is known as gorgonopsidae.

Gorgonops whaitsi skull from the American Museum of Natural History

Gorgonops is most well-known for its teeth, which, like I said earlier, were proportionally long, sharp, and curved.  They were similar in appearance to the canines on some carnivorous mammals, and because of their sheer length they are often compared to saber-tooth cats, despite the fact that gorgonopsids and cats aren't actually directly related beyond both being synapsids.  In addition to the two, downward-facing saber teeth, Gorgonops also possessed shorter teeth for nipping in the front of its face and shorter, broader teeth just behind the sabers, probably for cutting.  It is likely that Gorgonops delivered a killing bite to prey with the long teeth, puncturing vital areas, like the neck.  Then it would use other teeth to actually strip the meat off the carcass.  It is also very possible the long teeth had a role to play within the species, possibly for display.  This possibility would hinge on whether or not the teeth of gorgonpsids were visible or covered in some kind of soft tissue in life.

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

References

Gebauer, E.V.I. (2007). Phylogeny and evolution of the Gorgonopsia with a special reference to the skull and skeleton of GPIT/RE/7113 ('Aelurognathus?' parringtoni) (PDF) (Ph.D. thesis). Tübingen: Eberhard-Karls Universität Tübingen. pp. 1–316.

Jacobs, L. L., Winkler, D. A., Newman, K. D., Gomani, E. M. & Deino, A., 2005, Therapsids from the Permian Chiweta Beds and the age of the Karoo Supergroup in Malawi. Palaeontologia Electronica. Vol. 8, #1, pp. 28A: 21-23

Sunday, October 16, 2016

Megaraptor: Prehistoric Beast of the Week

Lets check out the impressive, yet mysterious predatory dinosaur, Megaraptor namunhuaiquii!  This dinosaur lived in what is now Argentina during the Cretaceous Period, roughly 90 million years ago.  Even though only parts of its skeleton have been found, Megaraptor is estimated to have been a little under thirty feet long from snout to tail. 

My Megaraptor namunhuaiquii life reconstruction.  If it was an allosauroid, it may have had feathers like I have shown.  On the other hand if it was, indeed, a tyrannosauroid, it almost certainly had feathers like I have shown.  So feathers was the safer choice with this one.

Megaraptor started out only being known from very scant remains, and has gradually become closer to being more completely known over the years since its discovery.  Initially only one of its gigantic sickle-shaped claws was discovered.  Upon seeing this, most scientists assumed it was the second toe claw of a dromaeosaur, much like Velociraptor or Deinonychus, just a heck of a lot bigger.  In fact, it would have been the biggest dromaeosaur known if that was the case, so it was named Megaraptor which translates to "Giant Thief/Hunter".  The claw, itself, was just under a foot long! 

Years later a few more bits and pieces were found from this dinosaur including some of the arm and hand.  In addition, a dinosaur, named Australovenator, was discovered, which bore striking similarities to the known parts of Megaraptor.  Because of this, it was determined that the monster claw did not belong on the foot but on the first digit of the hand which is what Australovenator had.  Megaraptor wasn't a dromaeosaur at all. Instead, it may have been from the same group of theropods that includes Allosaurus. Even amongst other large theropods, many of which had enlarged first claws on their hands, like Baryonyx (name actually translates to "heavy claw"), the claw of Megaraptor was proportionally the largest. 

One of Megaraptor's hand claws.  If it were to give you a wedgie, you'd die.

But there's more!  In 2014 even more material from Megaraptor was discovered.  A juvenile specimen preserved even more bones, including part of the skull.  We now know that at least as juveniles, Megaraptor would have had very long, low snouts, with proportionally small teeth.  The teeth themselves curved towards the back of the mouth.  It is because of the teeth that some paleontologists propose Megaraptor wasn't an allosauroid either, but rather a kind of tyrannosauroid, similar to Eotyrannus or Dryptosaurus. (which also possessed huge hand claws)

Section of the upper jaw of a juvenile Megaraptor.  Image from Porfiri et al. 2014.

So which is it?  What was Megaraptor!?  The definite answer to that is...we don't know.  We have some choices!  But we don't know anything for sure for now.  And that's okay!  This happens a lot in paleontology.  In some ways it is the unsolved mysteries and multiple possible truths and different ideas put forth by different individuals that make this field so much fun. 

That's all for this week!  As always feel free to comment below or on the facebook page

References

Benson, R.B.J., Carrano, M.T., Brusatte, S.L., 2010. A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic. Naturwissenschaften 97, 71-78.

Calvo, J. O.; Porfiri, J.D.; Veralli, C.; Novas, F.E.; Poblete, F. (2004). "Phylogenetic status of Megaraptor namunhuaiquii Novas based on a new specimen from Neuquén, Patagonia, Argentina". Ameghiniana 41: 565–575.

Novas, F.E. (1998). "Megaraptor namunhuaiquii, gen. et sp. nov., a large-clawed, Late Cretaceous theropod from Patagonia". Journal of Vertebrate Paleontology 18: 4–9.

Porfiri, J. D., Novas, F. E., Calvo, J. O., Agnolín, F. L., Ezcurra, M. D. & Cerda, I. A. 2014. Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation. Cretaceous Research 51: 35-55.

Sunday, September 25, 2016

Machairoceratops: Beast of the Week

This week we will be looking at another recently discovered horned dinosaur.  Enter Machairoceratops cronusi!

Machairoceratops was a ceratopsian dinosaur, which means it was in the same group as the more famous, Triceratops.  Within this group, however, it was more closely related to Diabloceratops and NasutoceratopsMachairocearatops' name translates to "Bent Knife Horned Face".  This is in reference to the shape of the two horns that grew from the top of the dinosaur's frill.  The species name, "cronusi" is after the mythical Greek god, Cronus, who cut off his dad's testicles with a curved sword.  (Next time you think your family has drama, remember that.)  In life, Machairoceratops would have been a plant-eater.  It lived in what is now Utah, USA, during the Cretaceous period, about 77 million years ago.  From beak to tail it would have measured about twenty feet long based on the skull. (Only the skull was found.)

Two rival Machairoceratops use their horns to lock into one another as they engage in a shoving match.

Like its relatives, Machairoceratops had a beak, a frill behind its head, and horns...very unique horns.  I know I say "unique" a lot in reference to ceratopsians, but it holds true!  Especially when it comes to this genus.  The two horns on the top of the frill curve forward and downward.  Frill horns aren't unheard of ceratopsians...but this exact orientation and curvature combined with their length, is.  It also had one horn over each eye which curved slightly upwards.  Due to the fragmentary remains of the skull, we sadly don't know what kind of horn ornamentation Machairoceratops had over its snout, if any at all.

Known fossil material from Machairoceratop's skull.  Image is from the paper by Eric K. Lund, Patrick M. O’Connor, Mark A. Loewen, Zubair A. Jinnah, referenced below.

As is the case with all ceratopsians, we don't know exactly why Machairoceratops' horns and frill evolved the way they did.  But it is very likely it had something to do with interacting with other members of its species.  If ceratopsian horns and frills were purely for defense against predators, they would likely be more uniform from species to species.  But this isn't the case.  Typically, when a variety of different, but related animals have the same sort of trait that is unique in form to each species, it has to do with some sort of intraspecies communication, like sexual display.  Just look at modern songbirds and their variety of colors and calls, or ungulates and their horns/antlers as modern comparisons. When it came to Machairoceratops, I felt that the overall shape that the brow and frill horns made together looked like it might serve well for combating rivals in head-to-head pushing behavior.  The antlers of modern reindeer also form this forward-facing crescent form, and they use them similarly.  Can I prove this was exactly how Machairoceratops used its horns?  Of course not.  But it's possible and also fun to think about.

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

References

Eric K. Lund, Patrick M. O’Connor, Mark A. Loewen and Zubair A. Jinnah (2016). "A New Centrosaurine Ceratopsid, Machairoceratops cronusi gen et sp. nov., from the Upper Sand Member of the Wahweap Formation (Middle Campanian), Southern Utah". PLoS ONE. 11 (5): e0154403.

 

Sunday, September 4, 2016

Palaeosaniwa: Beast of the Week

This week we shall be checking out a prehistoric reptile whose lineage continues to this day.  Enter Palaeosaniwa canadensis.

Palaeosaniwa was a lizard that lived in what is now North America, including Alberta, Canada, and Wyoming and Montana, USA, during the Late Cretaceous Period, from 75 all the way to 66 million years ago.  Within this time there may have been multiple species within the genus, but canadensis is the most well known.  Palaeosaniwa was a relatively large lizard, capable of growing to over eleven feet long from snout to tail, judging by the remains of it that have been found.  The genus name translates to "Ancient Saniwa".  Saniwa being another, slightly younger by a few million years, but still very much prehistoric, kind of lizard.  When alive, this Palaeosaniwa would have been a meat-eater.

Palaeosaniwa getting chased by an angry Anatotitan.

Palaeosaniwa was a kind of veranoid lizard, in the same family that includes living monitors, like the Komodo Dragon, as well as the extinct marine lizards, the mosasaurs.  Like the modern Komodo Dragon, Palaeosawina had long, curved, serrated teeth which were probably adept at grabbing and tearing mouthfuls of meat off carcasses.  It likely had other adaptations in common with it's modern relative, but unfortunately venomous saliva and forked tongues have never fossilized.

Me comforting my modern varanoid friend, Bruno, the Black-Throat Monitor (Varanus albigularis ionidesi)  He would have been way too emotionally sensitive to survive the Cretaceous.

There is something to be respected about a lizard that lived for such a long span of time amongst dinosaurs.  Despite the fact that an eleven-foot lizard is nothing to scoff at, it still coexisted with some of the largest and potentially dangerous dinosaurs of all time.  Veranoids historically tend to be very adaptable.  Their strong arms and legs, each ending in five curved claws are great for climbing, digging, and running.  Their long muscular tails are an effective weapon against enemies and also allow them to be strong swimmers.  This combination of adaptations would have made this lizard a jack-of all trades, opportunistic meat-eater, a very good place to be in the long run.  Because Palaeosawina was a mid-to-small scale meat-eater, pretty much every other creature in its community probably had some sort of beef with it.  Large plant-eaters like ceratopsians and hadrosaurs likely would have seen it as a threat to their eggs and babies and may have tried to chase or even kill it on site, while large predators like tyrannosaurids and even Dakotaraptor would have likely hunted it for food in addition.  Despite this, this lizard still managed to carve a prominent niche that remains intact to this day thanks to its modern kin.  Palaeosawina would have had to be an extremely tough lizard!

That's all for this week.  As always feel free to comment below or on the facebook page.

References

Archibald, J. David (2011). Extinction and Radiation: How the Fall of Dinosaurs Led to the Rise of Mammals. JHU Press. p. 43.

Michael Joseph Balsai, The phylogenetic position of Palaeosaniwa and the early evolution of the Platynotan (Varanoid) anguimorphs (January 1, 2001). Univ. of Pennsylvania - Electronic Dissertations. Paper AAI3031637.

Thursday, August 25, 2016

Visiting the New Jersey State Museum: Dryptosaurus gets a Mount (FINALLY)

Scroll up.  See the dinosaurs I painted for this site's banner up there?  They are Dryptosaurus and Hadrosaurus, the first two dinosaur skeletons ever recognized by modern science in the United States.  Just as important to me is the fact that they were both unearthed in New Jersey, my home state.  That being said they are both dear to my heart.  In fact, Dryptosaurus I would go so far to say is my all time favorite carnivorous dinosaur.  Sadly, despite their historical and scientific importance, both of these dinosaurs are grossly underrepresented in many aspects of paleontology culture, especially Dryptosaurus for reasons that are still a mystery to me.  Seriously, any appearance this dinosaur ever makes is a rare treat. Toy companies that make dinosaur figures especially frustrate me.  Are you reading this, Safari?  How about you, CollectA?  Seriously, give Dryptosaurus (and Hadrosaurus too while we're at it) a freaking figure already!  You can only redo Tyrannosaurus so many times!

Basically me if a Dryptosaurus toy is ever actually mass produced.

Perhaps even sadder was the fact that despite being such an important fossil discovery, Dryptosaurus never actually got a skeleton of it erected anywhere.  If anything you would only ever see its bones laid out on a flat surface someplace.  And yes, I hear some of you smug, self-proclaimed experts back there. "Dryptosaurus is too fragmentary to get a skeletal mount!" Nope.  Sorry that won't work with me.  Dinosaurs from WAY more scant remains have gotten full skeletal mounts before.

Argentinosaurus huinculensis reconstruction at Museo Municipal Carmen Funes, Plaza Huincul, Neuquén, Argentina.

It seemed that Dryptosaurus would never get a skeletal mount for people to really see and appreciate the true majesty of this amazing beast...until now!  The New Jersey State Museum in Trenton, NJ, is the first facility in history to have not just one, but TWO Dryptosaurus skeletal mounts on display in their new, as of July 2016, natural history hall!  I was able to make a trip over there recently to check them out in person.  They are nothing short of spectacular.

OMG THEY'RE SO COOL!

Now that we have seen them and are done scooping the mush back into our open skulls from having our minds utterly blown from sheer awesomeness, lets check these guys out a little more closely.  The first thing you will notice is the especially dynamic pose.  That wasn't chosen for this exhibit purely based on the fact that it looks cool.  There is history there.  Dryptosaurus was one of the dinosaurs painted by famed illustrator Charles Knight back in 1896. (Charles Knight is widely accepted as pretty much the most influential paleoartist of all time.) He depicted two Dryptosaurus fighting in this exact pose and named it "Leaping Laelaps". (Laelaps was the original name of Dryptosaurus)  This was a big deal back then since every other illustration of a dinosaur ever portrayed during that time and even for decades after were as sluggish tail-dragging cold-blooded lizard creatures.  This was extremely progressive and even seen as downright unlikely at that time.  The painting, itself, looks like it was done in the 1990s if one didn't know the context.

Charles Knight's "Leaping Laelaps" painting.  They may not look special by today's standards but at the time this sort of depiction was unheard of and still didn't catch on until almost one hundred years later.

Remember when I mentioned that Dryptosaurus was only known from fragmentary remains?  This means that the folks at the NJ State Museum had to be especially thoughtful when reconstructing the rest of the skeletons since some of the bones had to be made based on guesswork.  This is especially tricky when the skeleton in question is missing a head.  In the case of Dryptosaurus we have some of the skull including part of the jaws and some other bits...but not enough to get a definite picture.  I got into contact with some people I know from the museum, including volunteer, Wayne Callahan, assistant curator, Jason Schein, and Curator David Parris, to get some more details on these skeletons.  What I found out was that elements from a few other related, but more completely known, kinds of dinosaurs were used as references to fill in missing gaps.  Most notably was AppalachiosaurusAppalachiosaurus was another kind of tyrannosauroid that lived on the east coast of North America, and was probably the closest relative to Dryptosaurus that we know of.  Elements from the much older, basal tyrannosauroid, Dilong, and the two-fingered tyrannosaurid, Gorgosaurus, are also used.

The last thing you'd see...




In addition to the Dryptosaurus skeletons, the New Jersey State museum has plenty of other awesome additions to its natural history hall.  There is now a fossil lab right there in the public viewing area where you can see volunteers and scientists prepping real fossils behind glass.  It was there that I met Hank, another volunteer, as he was using an air scribe to chip the excess rock off of a prehistoric crocodile skull that was discovered in southern New Jersey.


Tip of the crocodile's snout
Closeup of one of the crocodile's teeth with Hank's hand for scale.

Finally I saw an old familiar face...er...skull in the form of the New Jersey Elk Moose!  If you have been following me since 2012 you might remember this fellow from a guest article my friend, Amanda, provided when she was studying prehistoric deer.  This very specimen was the one she had to get teeth measurements from.

The NJ Elk Moose on display in the new Natural History Hall at the NJ State Museum.
There is much more to explore at the New Jersey State Museum.  If you get the chance definitely stop by and pay it a visit.  The Dryptosaurus skeletons alone are worth it!

Monday, July 4, 2016

Cladoselache: Prehistoric Beast of the Week

Get your diving gear ready...and time machines too I guess.  We are about to check out another awesome prehistoric shark!  Say hello to CladoselacheCladoselache was a genus of shark that included several species, but the most well understood is called Cladoselache fyleri.  It lived during the late Devonian period, about 375 million years ago.  (much older than the first dinosaurs) It swam in oceans that once covered what is now North America, the best preserved specimens of this ancient fish being from Ohio.  Cladoselache could grow to be about six feet long from snout to tail and would have eaten meat (like all sharks) in life.  The genus name translates to "Branch Tooth Shark" due to the fact that could have multiple teeth per root.

Life reconstruction of Cladoselache fyleri, by Christopher DiPiazza

Cladoselache was a very interesting animal due to the fact that, despite being so old, it had some characteristics about it that are still very prominent in sharks today.  At the same time it also had some features that are completely alien by living shark standards.  The mouth of this shark was at the very front of the snout, called a terminal mouth.  This is in contrast to the kinds of mouths that you see in many modern sharks, like great whites for instance, that have that long nose jutting out before their actual mouths. (which is called subterminal)  However, some sharks today also exhibit the terminal mouth, like the weirdly wonderful Frilled Shark, for instance.  Inside the mouth Cladoselache had many long pointed teeth, that could branch out from a single root.  The teeth weren't serrated, suggesting it didn't tear apart its prey, but rather would have hooked it and sucked it completely into its jaws whole.  In fact, some very well-preserved specimens of Cladoselache even show whole fish skeletons in the stomach cavity.  Thanks to these we even can tell that Cladoselache grabbed and swallowed its prey tail-first!  Cladoselache fyleri also had seven gill slits on each side of its head, which is more than most sharks today, but also not unheard of by modern shark standards either.

Cladoselache tooth.  Note the multiple points.

One feature about Cladoselache that you won't find in any modern sharks is the fact that it was almost devoid of any toothy scales, called denticles, that sharks are so well known for being covered in.  In fact, this shark was almost completely naked, scale-wise, except for a few regions around the face and on its fins.  Paleontologists still have no clue why this was.  It also had short spines in front of its two dorsal (back) fins which may have helped it cut the water as it swam.

Cladoselache fyleri fossil on display at the American Museum of Natural History in New York.

Thanks to beautifully preserves specimens of Cladoselache, we even know what the outline of its body looked like.  This is rare since shark skeletons are almost completely composed of soft cartilage, not bone, and therefore rarely fossilize.  Most other kinds of prehistoric sharks are only known from teeth.  Not the case with Cladoselache, though.  It had a long, streamlined body and its tail was an almost perfectly symmetrical crescent shape with pronounced keels on the sides for tail muscles.  When you compare this to the tails of sharks and other fish today, you will see that symmetrical shape is present in extremely fast-swimming creatures like Mako Sharks and Tuna.  It is likely Cladoselache was fast, too, using its speed to grab prey and also escape predators, like the twenty-foot long, armored fish, Dunkleosteus.

That is all for this week!  As always please comment below on the facebook page!

References

"Ancient Sharks." Ancient Sharks. Reequest Center for Shark Research N.p., n.d. Web. 04 July 2016. 

A. S. Woodward & E. J. White, The dermal tubercles of the Upper Devonian shark Cladosclache. - Annals and Magazine of Natural History 11: 367–368. - 1938.

B. Dean, Contributions to the morphology of Cladoselache (Cladodus). Journal of Morphology 9:87–114. - 1894.

Sunday, June 5, 2016

Paraceratherium: Beast of the Week

This week let's take a look at the largest land mammal of all time. (That we know of.)  Make way for Paraceratherium transouralicum!  Paraceratherium was a plant-eating mammal that lived all over what is now Eurasia during the late Paleogene Period, between 34 and 23 million years ago.  It was gigantic, towering over all other land mammals, including elephants, at up to sixteen feet tall at the shoulder (not including the long neck and head), and almost twenty five feet long. (Keep in mind this animal did NOT have a long tail.  A 25-foot long dinosaur isn't as large because of the long tail in the back takes up a lot of that length.)

Paraceratherium life reconstruction by Christopher DiPiazza

Paraceratherium has changed its name since its discovery a few times.  This is because specimens of it have all been pretty fragmentary, and therefore given names when initially discovered until it was realized they were all from the same kind of beast.  It may be more recognizable by the name, Indricotherium, which has since been lumped with Paraceratherium.  This was what it was called when it was featured on the BBC miniseries, Walking with Prehistoric Beasts. (Sequel to Walking with Dinosaurs)  Within the genus, Paraceratherium, there have been a few species named, but P. transauralicum is the most well-studied.

Paraceratherium skull on display at the American Museum of Natural History in New York

So what kind of mammal was Paraceratherium exactly?  It doesn't quite resemble any of the other large land mammals we know today.  The answer can be found when you look at its skeleton more closely.  Even though all specimens of it are mostly fragmentary, we do have good skull material.  If you look at the teeth of this animal, you will see large molars for grinding in the back, and pointed incisors in the front on both the upper and lower jaws.  This gives it away as  belonging to the order, perrisodactyla, which includes modern horses, tapirs, and rhinos.  So think of Paraceratherium as a really huge, hornless rhino.  The shape of the nasal cavity also tells us, by comparing it to skulls of its living relatives, that it likely had flexible, strong lips, or perhaps even a short trunk, like tapirs do.  Reconstructions of this animal's face seem to vary since horses, rhinos, and tapirs all have varying versions of a similar adaptation in this area.

It is likely, judging by the wear found on its teeth, that Paraceratherium was a browser, eating leaves from the tops of trees in life.  Since leaves have very little actual nutritional value as a food, animals, like Paraceratherium, need to eat large quantities in order to sustain themselves.  They also have large guts for fermenting tough-to-digest plant material, and and long digestive tracts to get as much nutrition out of the food as possible before its finally pooped out.  Because of this leafy diet (as oppose to grass which can just be sucked up with a wide mouth)

Perrisodactylids are known for their flexible lips. However, among them there is a wide variety of lips. Rhinos can have wide, or pointed lips.  Horses have rounded lips, and tapirs have short trunks.  This is all dependent on their feeding style.  My reconstruction of Paraceratherium has something between a White Rhino's wide lip and a tapir's short trunk.  This would allow Paraceratherium to select as many edible leaves as possible with less effort, something very important for large animals that rely on low-nutrition foods like leaves.  (It may have had something different. That's just my hypothesis.)

It was recently suggested that because of it's immense size, Paraceratherium would have needed an efficient way to have regulated its body temperature, especially when it came to cooling off.  Some scientists have suggested that Paraceratherium had large ears, like an elephant, where blood could be closer to the cooler outside temperatures before flowing back into the rest of the body, ultimately preventing the animal from overheating.  Many mammals from desert environments today have large ears for this reason.

The Fennec Fox, which lives in the Sahara, has extremely large ears for heat dissipation.  Larger animals like elephants use this same adaptation, and Paraceratherium may have as well.

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

References

 Antoine, P. O.; Karadenizli, L.; Saraç, G. E.; Sen, S. (2008). "A giant rhinocerotoid (Mammalia, Perissodactyla) from the Late Oligocene of north-central Anatolia (Turkey)". Zoological Journal of the Linnean Society 152 (3): 581–592. 

Martin, C.; Bentaleb, I.; Antoine, P. -O. (2011). "Pakistan mammal tooth stable isotopes show paleoclimatic and paleoenvironmental changes since the early Oligocene". Palaeogeography, Palaeoclimatology, Palaeoecology 311: 19–29.

Prothero, 2013. Rhinoceros Giants: "The Paleobiology of Indrichotheres". pp. 87–106

Wang, Y.; Deng, T. (2005). "A 25 m.y. Isotopic record of paleodiet and environmental change from fossil mammals and paleosols from the NE margin of the Tibetan Plateau". Earth and Planetary Science Letters 236: 322–338.


Monday, May 9, 2016

Aquilonifer: Beast of the Week

This week we will be looking at a tiny creature that gives us insight to how some of the earliest mothers raised their young.  Check out Aquilonifer spinosusAquilonifer was a small arthropod (same group of animals that includes insects, arachnids, and crustaceans) that lived in what is now Hertfordshire, England, during the Silurian Period, about 430 million years ago.  It measured only about a centimeter long as an adult and would have scuttled around on the ocean floor. We are unsure as to what it ate but it may have been a scavenger, sifting through the sand, and eating any tiny morsel of organic material it could find.  Judging by its mouthparts it may also have been a predator, subduing and eating smaller animals it came across.  The genus name, Aquilonifer, translates to "Kite Carrier" and the species, name spinosus, translates to "spiny".  It was also referred to as "The Kite Runner" by paleontologists who found and studied it for the fashion in which it cared for its young.

Life reconstruction by Christopher DiPiazza

This little creature was found with ten even tinier arthropod organisms attached to its body via fine threads.  At first it was hypothesized they may have been some sort of parasite, but that doesn't make much sense since all known parasites would need to be much closer to their hosts in order to survive, not floating behind it on a string.  It was then determined, upon looking at them more closely, that they were most likely offspring.  This creature would have dragged its kids around like little parasailers underwater!  Even though no animal known today does anything quite like this, many arthropods do carry their young around with them via other means.  Many spiders carry their eggs and young in a silk pouch attached to the abdomen, and mother scorpions pile their liveborn offspring onto their backs.  Considering how old and distantly related Aquilonifer is to these modern creatures, to say this was indeed a method of parenting isn't really unreasonable.  Parasites, on the other hand, tend to be pretty consistent across the board in wanting to be on or inside their hosts.

Basically this, but with less character-building experience.

Aquilonifer was also interesting in that beyond being an arthropod...scientists can't quite figure out exactly where it belongs on the family tree.  It may have been an extremely early branch of the arthropod phylum, that would eventually radiate into the forms that you see today.  When alive it may have crawled around on the ocean floor similar to a centipede does on land with its 26 legs.  It had a long pair of feelers in the front, what appear to be mandibles in the front, and ...get this....no eyes.  This isn't that crazy if you think about it.  This creature probably relied mostly on feeling in an environment where having a sense of sight wouldn't have benefited it.

High power 3D scanning of the tiny fossil allowed scientists to get a more detailed view of its anatomy.

That's it for this week!  As always feel free to comment below or on our facebook page!

References

Siveter, David J, Siveter, Derek J, Sutton, MD and Legg, D, 2016, Tiny individuals attached to a new Silurian arthropod suggest a unique mode of brood care, PNAS Online 

 Jonathan Webb, BBC News, 4 April 2016, Bizarre fossil hauled its offspring around 'like kites'

Sunday, May 1, 2016

Confuciusornis: Beast of the Week

This week we will be checking out possibly one of the most well-understood of all the prehistoric dinosaurs.  Check out Conficiusornis sanctusConfuciusornis was a prehistoric bird, that lived in what is now China, during the early Cretaceous Period, between 125 and 121 million years ago.  From beak to tail it measured about a foot and a half long, and had a wingspan of a bit over two feet wide.  When alive, Confuciusornis would have eaten meat but also probably ate plant material, possibly seeds, as well.  Its name translates to "Confucius Bird Sage", in reference to Confucius, the famous Chinese philosopher.

Confuciusornis is known from literally thousands of fossilized specimens, which is unheard of when it comes to other dinosaur fossils.  Because of this we know quite a bit about its anatomy and lifestyle.

Confucius fossil pair.  Possibly a male and female. (note the long tail feathers)

First of all, many of the Confuciusornis specimens preserved soft tissue, including feathers.  It had long, narrow primary feathers on the wings and certain individuals had a pair of extremely long, ribbon like feathers growing from their tails.  It has been suggested that Confuciusornis was sexually dimorphic, the males possessing the long ribbon feathers for display.  It is also possible that both sexes had these feathers, and certain individuals were molting (shedding old feathers) at the time of their deaths.  The presence of these feathers also didn't have any correlation with body size, so if it was sex-related, the males and females were the same size as adults.  These tail feathers are interesting in that only the tips demonstrate the classic feather structure with a central shaft, branching off into barbs on either side.

Confuciusornis possessed a large, toothless beak, like modern birds.  However, there were other prehistoric birds that lived after Confusiusornis had gone extinct that still had teeth.  This proves that Confuciusornis evolved its beak independently of those that we see in modern birds.  The beak would have been relatively powerful in life, and many scientists suggest it could have been a seed-eater.  Modern seed-eating birds, like cardinals and sparrows, have similarly shaped beaks.  However, some doubt this since no gastroliths, small rocks swallowed by animals to help digest hard food, like seeds, were ever found in any Confuciusornis specimen. (and we HAVE found them in many other dinosaur fossils) We know Confuciusornis  at least ate small fish, since the remains of one was found in the neck region of one specimen.  This could have been the crop, a pouch in the throat region of birds, used for storing food before swallowing.

The wings of Confuciusornis tell us that this dinosaur probably could fly, but it wouldn't have been as agile in the air as many modern birds are, especially for long periods of time.  We hypothesize this because Confuciusornis doesn't have a very large breastbone, or keel as it's called in birds, for wing muscles to attach.  Keel bones in many modern birds are proportionally huge.  Even the ones on domestic chickens and turkeys are large. (Next time you eat a rotisserie chicken check this out.  It's where the breast meat attaches to the skeleton.)  Confuciusornis also didn't have as wide of a range of motion in its shoulder joints as modern flying birds do, which would have made flapping a bit more difficult for it.  Finally, it's tail lacked the broad steering feathers found in modern birds.  The hands of Confuciusornis had three distinct fingers, tipped with curved claws, which is something else not common in modern birds.

Confuciusornis life reconstruction showing some display behavior by Christopher DiPiazza.

Lastly, scientists may have figured out what color Conficiusornis' feathers were!  Since the fossilized feathers were so well preserved, scientists were able to look at them under a powerful microscope and see the shapes of melanosomes, organelles that give color to a feather.  Even though the color, itself, wasn't visible, the shape of the organelle would reflect the pigment that would have been there in life.  By comparing these shapes to those of modern bird feather melanosomes, they were able to conclude that Confuciusornis likely had a dark gray body, black tail feathers, and possibly white primary feathers.  However, it should be noted that not ALL kinds of melanosomes necessarily preserved, so an overlapping of different kinds of these organelles may have yielded a different coloration in certain areas.

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

References

Chiappe, Luis M., Shu-An, Ji, Qiang, Ji, Norell, Mark A. (1999) "Anatomy and systematics of the Confuciusornithidae (Theropoda:Aves) from the Late Mesozoic of northeastern China" "Bulletin of the American museum of Natural History no.242 89pp.

Elzanowski, A. (2002) "Biology of basal birds and the origin of avian flight". In: Zhou Z., Zhang F. (eds) Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution, Beijing, 1–4 June 2000. Science, Beijing, pp 211–226

Wogelius, R.A., Manning, P.L., Barden, H.E., Edwards, N.P., Webb, S.M., Sellers, W.I., Taylor, K.G., Larson, P.L., Dodson, P., You H., Da-qing L., and Bergmann, U. 2011. Trace metals as biomarkers for eumelanin pigment in the fossil record. Science, 333(6049): 1622-1626.

Zhou Z. and Farlow, J.O. (2001) "Flight capability and habits of Confuciusornis". In: Gauthier and Gall (eds). New perspectives on the origin and early evolution of birds: proceedings of the international symposium in honor of John H. Ostrom. Peabody Museum of Natural History. Yale University, New Haven. pp. 237–254

Monday, April 4, 2016

Yutyrannus: Beast of the Week

This week we will be checking out a dinosaur that changed the way we think about feathers.  Enter Yutyrannus huali!

Yutyrannus was a meat-eating dinosaur that lived in what is now China during the early Cretaceous Period, about 125 million years ago.  It was large, measuring about thirty feet from snout to tail as an adult.  The genus name, Yutyrannus, translates to "Feathered Tyrant" because, as you're about to learn, it had feathers!

Yutyrannus life reconstruction by Christopher DiPiazza.

Yutyrannus belonged to the tyrannosauroid group, and was closely related to other dinosaurs like Guanlong, Eotyrannus, and Dryptosaurus.  Like them, it had characteristic curved, serrated teeth, and strong front arms, each tipped with three hooked claws.  It's later relatives would eventually develop the well-known two-fingered front limbs, best known in its slightly more distant relative, Tyrannosaurus.  Adult Yutyrannus also possessed a short horn in front of each eye and a ridge-like bony crest running down the top of its snout.  These features may have been used combat between rivals, or display within its species.  Yutyrannus had strong legs, but its foot bones were relatively short compared to those of some other theropods, suggesting it wasn't an extremely fast runner in life. It may have been better at ambushing, and then using its size and power to take down prey, rather than chasing it very far.

Yutyrannus cast mounted at the American Museum of Natural History in New York.

Yutyrannus' real claim to fame, however, is the fact that we know for a certain it had feathers.  This is due to actual visual presence of fossilized feathers found on the remains of the three specimens that are known.  Because of the placement of these feathers, which includes the bottom of the pelvis, the tail, the arms, and the ankle, it is likely that in life, it had a more even coat of plumage over most of its body.  This evidence makes Yutyrannus the largest dinosaur known to date with actual fossilized feathers.  (Other large dinosaurs, like Deinocheirus, show evidence of having had feathers by having a pygostyle, but not actual fossilized feathers found with its bones, which is what we have with Yutyrannus.)  These feathers weren't preserved well enough to tell exactly what kinds of feathers they were, but they most likely would have been somewhat shaggy in life, similar to those on modern ground birds, like emus or kiwis. 


Shaggy kiwi.  If you're even in Maryland, check these guys out at the National Zoo.

So why feathers?  This is the first question that many people ask when learning about Yutyrannus.  A better question might be "why not feathers?"  Feathers are a versatile adaptation.  They can keep an animal warm when the environment is cold, but also cool when the environment is too hot.  They also serve protection against the elements like precipitation or the sun, can help camouflage by obscuring the animal's basic body shape, and can aid with communicating to other members of the same species in a visual and/or behavioral way.  Thanks to finding Yutyrannus, we now think it is more than likely that tyrannosauroids all had feathers in some form, including T. rex.

Preserved feathers on the ankle (you can see the bones on the left) of Yutyrannus on display at the American Museum of Natural History in New York.

If you live in the New York / New Jersey area you can come see a  cast of the famous Yutyrannus fossil, as well as remains (casts and real fossils) of many other important feathered dinosaurs at the American Museum of Natural History's seasonal Dinosaurs Among Us exhibit, which closes in January, 2017.  Maybe I'll see you there!  That is all for this week.  As always feel free to leave a comment below or on the facebook page.

References

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" Nature 484 (7392): 92–95.