Monday, June 3, 2019

Dakosaurus: Beast of the Week

You may know that we have reviewed a Godzilla dinosaur on here before.  This week we will be looking at yet another prehistoric beast with connections to the "King of the Monsters."  Check out Dakosaurus andiniensis!

Dakosaurus andiniensis lived in the oceans that once covered what is now Argentina during the Late Jurassic to the Early Cretaceous, between 145 and 140 million years ago.  Dakosaurus was a meat-eater in life, and measured about fifteen feet long from snout to tail.  The genus name, Dakosaurus, translates to "biter lizard/reptile" in reference to the creature's formidable teeth.  There are actually a few species within the Dakosaurus genus, but I want to focus specifically on the species, Dakosaurus andiniensis.  

Dakosaurus andiniensis by Christopher DiPiazza.

Dakosaurus was an extinct genus of crocodilian that belonged to the family called Metriorhynchidae.  Metriorhynchids were prehistoric crocodiles that were specially adapted to living in the ocean during the middle Jurassic through the early Cretaceous periods.  Their limbs were like flippers and their flattened tails even independently evolved flukes like those of sharks, dolphins, and their fellow reptiles, the ichthyosaurs and mosasaurs.

Fossilized skull of Dakosaurus andiniensis.  It looks mean!

Dakosaurus andiniensis had a uniquely short snout compared to the other species within its genus, giving it a particularly menacing look, to the scientists who studied it.  It is because of this unusually short, and boxy face, that this species of Dakosaurus was nicknamed "Godzilla" among the scientists who worked with it.

Dakosaurus' teeth were unique in that they were both laterally compressed and serrated.  This is a feature more commonly seen in certain kinds of meat-eating dinosaurs.  In fact, when the isolated teeth of Dakosaurus were first discovered, they were initially believed to have been from a Megalosaurus, not a crocodile.  The skull of Dakosaurus had openings towards the back, called fenestrae, that would have anchored powerful jaw muscles in life.  This, combined with the fact that its teeth were deeply rooted within the jaws, means that Dakosaurus would have been able to bite down with extreme force.  It is likely that an adult Dakosaurus would have been a top predator and was able to hunt most other animals it shared its habitat with, including other marine reptiles. 

Nobody is exactly sure how Dakosaurus would have reproduced.  There is specific fossil evidence that other prehistoric marine reptiles, like mosasaurs and ichthyosaurs, gave birth to live young in the water.   Dakosaurus' group, the crocodilians, however, only lay eggs in nests, however.  In fact, even broadening this group to all of archosauria, which includes crocodilians, in addition to dinosaurs and several other reptile groups, all we know of is egg-laying so far.  Going off this information alone, using closest relatives as a reference, Dakosaurus would have needed to haul out on land to lay its eggs.  However, a study looking at the anatomy of a more completely known metriorhynchid showed that the anatomy of the pelvis was more similar to that of other kinds of marine reptiles that we know gave birth to live young.  Despite that all known archosaurs lay eggs, it wouldn't be unheard of for one group of marine crocodilians to have evolved live birth, since we already can confirm it has happened multiple independent times in other groups of marine reptiles.

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

References

Gasparini Z, Pol D, Spalletti LA. 2006. An unusual marine crocodyliform from the Jurassic-Cretaceous boundary of Patagonia. Science 311: 70-73.

Herrera, Y.; Fernandez, M.S.; Lamas, S.G.; Campos, L.; Talevi, M.; Gasparini, Z. (2017). "Morphology of the sacral region and reproductive strategies of Metriorhynchidae: a counter-inductive approach"Earth and Environmental Science Transactions of the Royal Society of Edinburgh: 1–9. 

Vignaud P, Gasparini ZB. 1996. New Dakosaurus (Crocodylomorpha, Thalattosuchia) from the Upper Jurassic of Argentina. Comptes Rendus de l'Académie des Sciences, Paris, 2 322: 245-250.

Sunday, April 28, 2019

Dryptosaurus: Beast of the Week

This week we will be looking at another extremely important, yet sadly underrepresented dinosaur.  It is also a dinosaur that is native to my home state and in some ways the unofficial mascot of this website. (It's featured on the banner above.)  Check out Dryptosaurus aquilunguis!

Dryptosaurus was a meat-eating dinosaur that lived in what is now New Jersey, on the East coast of the United States during the Late Cretaceous Period, 67 million years ago.  From snout to tail it measured about twenty five feet long.  The genus name, Dryptosaurus, translates to "Tearing Lizard/Reptile" and the species name, aquilunguis, translates to "Eagle Claw" in reference to this dinosaur's huge, curved claws, which it possessed on its hands.  Dryptosaurus was a tyrannosauroid, closely related to Eotyrannus, from England, Guanlong, from China, and to a lesser extent, Tyrannosaurus rex, from Western North America.

Dryptosaurus life reconstruction by Christopher DiPiazza.

 Dryptosaurus was one of the first prehistoric dinosaurs to be recognized by science in the United States.  Discovered only eight years after America's first discovered dinosaur, Hadrosaurus, which was also a resident of what is now New Jersey.  It was originally given the genus name, Laelaps, which is the name of a dog from Greek mythology that always succeeded in catching its prey.  Despite being a really cool name, it was soon realized that the genus name, Laelaps was already assigned to...a mite, and thus the dinosaur was changed to Dryptosaurus instead.

Dryptosaurus skeletal mounts on display at the New Jersey State Museum.

Dryptosaurus is interesting because it was a more basal kind of tyrannosauroid, like Guanlong and Eotyrannus, yet it lived much later, during the very end of the Mesozoic, at the same time as the more specialized short-armed, two fingered, tyrannosaurids, like TyrannosaurusDryptosaurus was sort of a relic of it's time, exhibiting adaptations of predators from long before.  Other than it's three-fingered hands already discussed, Dryptosaurus also possessed lighter, blade-like teeth which are in contrast to the more robust teeth of its relatives like Tyrannosaurus.  These ancestral features could have had something to do with the fact that when alive, Dryptosaurus lived isolated from the western dinosaurs of the late Cretaceous, like Tyrannosaurus and Triceratops, by a shallow sea running longitudinally down most of the center of what is now the United States, called the Western Interior Seaway.  Since it wasn't in competition with its western relatives due to geographic isolation, it may have retained its the more generalist adaptations of its ancestors. 

Dryptosaurus stands out among tyrannosauroids because its claws, especially the ones on the first digit of each hand, were the longest in proportion to the rest of the body.  It's arms were also not quite so long when compared to more basal tyrannosauroids, but still were certainly longer than those of more specialized tyrannosaurids, like Tyrannosaurus.  Despite the fact that it is only known from bones, Dryptosaurus likely had feathers.  We can assume this thanks to fossilized feathers on other tyrannosauroids, namely Yutyrannus and Dilong.

Baby Dryptosaurus (based on bones of other kinds of baby theropods) investigates a horseshoe crab.  Sea creatures may have been familiar cohabitants to Dryptosaurus.

Not much is known about Dryptosaurus' environment since the east coast of the United states has lots of human development, and therefore is more difficult to excavate for fossils now.  However, there are known fossils of duck-billed dinosaurs, armored dinosaurs, and crocodilians from the same area.  Since its environment was coastal, Dryptosaurus also may have taken advantage of aquatic animals as food like beached fish and other marine creatures, or perhaps turtles coming to shore to lay eggs. 

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

References

Brusatte, S. L. and Benson, R. B. J. and Norell, M. A. (2011) The Anatomy of Dryptosaurus aquilunguis (Dinosauria: Theropoda) and a Review of its Tyrannosauroid Affinities. American Museum Novitates, 3717 . pp. 1-53. ISSN 0003-0082

Cope, E.D. (1866). "Discovery of a gigantic dinosaur in the Cretaceous of New Jersey." Proceedings of the Academy of Natural Sciences of Philadelphia, 18: 275-279.

Monday, April 22, 2019

Toads on the Road: Sharing our Earth with Wildlife

For the past four years, whether it be New York or Philadelphia, I have been living in major cities.  Initially big cities don't seem like ideal places to see wildlife, but if you know where and how to look, amazing creatures can be found.  Since putting a birdfeeder behind my Philadelphia row home, where I thought I would only ever attract non-native House Sparrows and Pigeons, I noticed a myriad native bird species visiting my yard over just a few days.  Birds of prey, like Red-Tailed hawks hunt squirrels among tall buildings, migratory visitors, like Snowy Owls can be seen resting on telephone poles and other human-made structures before continuing their long journeys along North America, Brown Snakes emerging from hibernation from under my neighbor's wooden front steps, and if you stay diligent at night, you can see the careful raccoon or opossum making rounds through the busy urban neighborhood as they forage for meals.

Eastern Garter Snake (Thamnophis sirtalis) I found in Philadelphia.  It became docile after a few seconds after I caught it.  Never tried to bite.  (That being said don't touch wild snakes you don't know.  Sometimes they do bite.)

Once you broaden your horizons, you will find that cities have amazing public parks dedicated to preserving wild spaces to enjoy.  I'd never imagine seeing the striking Northern Shoveler, or the tiny, doll-faced, Saw-Whet Owl in a city like Philadelphia.  On my morning commute from Philadelphia to Camden, New Jersey, I have had a Bald Eagle soar over my car and on many occasions seen flocks of wild turkey strutting though the local graveyard.

Northern Shoveler (Spatula clypeata) I photographed (by putting my phone camera behind binoculars...which explains the grainy quality) at John Heins Wildlife Refuge in Philadelphia.

It's no surprise that, since they have lived here long before we have, many species of wild animal have adapted to city life.  Some even thrive in it.  However, there are others that still struggle and are in constant danger due to human development.  Amphibians, like frogs and salamanders, are extra sensitive to any sort of pollution, due to their absorbent skin, and during the spring, find themselves in mortal danger as they try to cross busy roads in an attempt to get to water so they can reproduce.  The amphibians have been making this journey every year for countless generations, long before the roads were built.  Luckily there are places like the Schuylkill Center for Environmental Education, in Philadelphia, that make a effort to ensure the journeys of local amphibians are as safe as possible. 

Every Spring thousands of American Toads (Anaxyrus americanus) and Pickerel Frogs (Lithobates palustris) emerge from their hibernation in the green spots of Philadelphia and make the relatively long, and strenuous journey to the Roxborough Reservoir where they can lay and fertilize their eggs.  Every year at this time, on nights that are warm and wet, the Scchuylkill Environmental Center gathers volunteers though their website and facebook page to come together and block off the road with the most amphibian activity and aid the tiny creatures as they embark on their journeys.  I was fortunate enough to take part in this a few times this year and it was an amazing experience.

One of the biggest human threats to amphibians is roads.  Unlike deer and other larger mammals (which still get killed by cars regularly) amphibians aren't even noticed when crossing the road by drivers, so most people can't even stop or slow down to save them.  

About ninety percent of the amphibians crossing in this place are American Toads.  American Toads come in all shades of brown, some being a beautiful reddish-orange and others being almost black, with rough bumps on their skin.  They have proportionally shorter legs and can only hop in short bursts.  For protection, they have a pair of poison glands at the base of the head that is toxic if ingested by most predators.  It is important to note that all toads are technically frogs, being part of the anura (frog) order, but not all frogs are necessarily toads.  Also there are lots of other anurids that are commonly called toads but are in separate families from American Toads and their kin, the family called bufonidae.  American Toads and other members of bufonidae typically only go into the water to breed, and prefer to spend the rest of their time on land, hiding under logs and rocks during the day.

American Toads have bumpy, dry skin, can only hop short distances, and like many members of bufonidae, have a pair of poison-filled glands at the base of their heads.

Pickerel Frogs are the other amphibian we see in this area.  They are typically green or light brown in color with dark brown square-shaped spots.  They have a pair of lighter-colored lines down their backs, and they can hop extremely far in one bound.  They have moist skin, webbed feet, and prefer to spend a lot of their time in the water.  When threatened, they can secrete an irritating substance from their skin that deters most predators from eating them.  They are very similar in appearance to Leopard Frogs (Lithobates pipiens), a close relative that overlaps with them in a lot of their range, but Pickerel Frogs have spots that are arranged in neat rows on their backs, while Leopard Frog spots are more randomly arranged.

Pickerel Frog.  Notice the large, dark spots in two rows down the back.  This is the easiest way to differentiate them from closely related Leopard Frogs, which have more randomly arranged spots.

There are certainly a wide variety of other amphibians out and about this time of year in the area, but this specific body of water seems to be the breeding spot for only these two species as far as I can tell.  Once the sun sets, and it becomes dark, on wet warm nights, the ground almost alive with toads.  At certain points I need to be careful not to accidentally step on them, they are so dense.  We gently place any toads or frogs found crossing the road in buckets, and transport them to the other side of the road, away from the danger of cars, to continue their journeys.

Because the amphibians were so numerous, we would collect and release them in buckets.  I labeled the less common Pickerel Frogs so you compare the differences between them and toads more easily.

We also record every individual animal we see on a data sheet.  We even tally the dead individuals (unlucky enough to be killed by cars earlier) in their own separate column.  This data helps the Schuylkill Center maintain an idea of how many toads and frogs are in the area, what percentage of them are surviving, and what percentage of them are being killed by cars.  One of the nights I was there the team saved over three hundred toads.  My friend and I alone saved sixty four of those toads, nine frogs, and saw ten of either species that were killed by cars.

Despite saving so many toads, this is still a scene we saw too often.  Because the toads are so dense in that area, even with a team of over twenty people blocking off the most active street and helping them cross safely, every time a car does pass through a nearby street, there is a strong chance it will kill at least one or two individuals.  Most of the carcasses we found were alive only minutes earlier.  After tallying, we moved the carcass off the road, so A) it wont get re-tallied by someone else, and B) other animals that would scavenge them can do so off the road, and avoid becoming roadkill, themselves.

If we're lucky, we get to see some toads exhibiting an interesting courtship behavior, called amplexus.  Amplexus is when the smaller male toad grasps the larger female from behind with his arms and holds on as she continues her journey.  They're not mating when they do this on land.  The male is simply getting a ride to the pond and ensuring he have a mating partner when they finally reach the water.  Once in the water, the female will lay her eggs and the male will be right there to fertilize them as they come out.  We found several pairs of toads in amplexus hopping across the road that night.

Early in the night we found a pair of toads in amplexus.  The smaller male is on top, riding his female partner to the water.  When they arrive they'll each already have partners for mating.

Many frogs are sexually dimorphic, which means the males and females look different from each other.  In the case of both American Toads and Pickerel Frogs, the Females are larger than the males.  This is partially due to the amplexus I just mentioned, since the female needs to be large and strong enough to carry her partner, and sometimes multiple partners on her back and as she travels to the water to lay eggs.  Another way to tell the difference between male and female frogs, is the males are much more vocal, being the ones to emit calls at night to attract females and compete with other males.  When we were briefly handling the toads to them cross the road, the males would often call in reaction to being touched.  This is a reflex they exhibit when they feel any sort of presence on their backs, since when breeding many males will mistakenly grab another male.  The first male will make this call to alert him of his error and to get off so they can both go back to finding a female.

As always, it doesn't need to be Earth Day for you to actively help wildlife and the wild places they live.  No matter where you are, there are nature centers, parks, and zoos always willing to accept volunteers to help preserve the precious biodiversity we share.  What do you do to help preserve wildlife where you live?  Share below!

Sunday, March 24, 2019

Hadrosaurus: Beast of the week

Today we honor a very special dinosaur.  A dinosaur that not only has roots in New Jersey, but holds significance to American paleontology as a whole.  Enter Hadrosaurus foulkiiHadrosaurus was a plant-eating dinosaur that lived in what is now New Jersey, USA, during the Late Cretaceous about 79 million years ago.  It is known from the majority of a skeleton, minus the skull (bummer), and would have been about twenty five feet long from beak to tail.  Since it was the first of its kind to be discovered, Hadrosaurus' name is used as the family name, hadrosauridae, for the entire group of duckbill-dinosaurs, like Anatotitan, Maiasaura, Parasaurolophus, and Tsintaosaurus.  Its genus name translates to "Bulky Lizard" and the species name is in honor of William Parker Foulke, who took part in its discovery.

Life reconstruction of Hadrosaurus foulkii by Christopher DiPiazza.

Hadrosaurus is a very important dinosaur not just because it was found in New Jersey, but because it was actually the first scientifically recognized dinosaur ever dug up in all of the United States!  This dinosaur's bones were found in what is now Haddonfield, New Jersey, in 1838.  The man who discovered the first of its bones actually used them as decorations on his house until they were noticed by William Parker Foulke.  Foulke was intrigued by these bones and ended up digging out more of them from where the original specimens were unearthed.  Paleontologist, Joseph Leidy, correctly identified the bones as belonging to a dinosaur because of their similarity to those of Iguanodon, which had been discovered during the 1820s in England.

Known skeleton of Hadrosaurus foulkii on display at the Academy of Natural Sciences in Philadelphia, PA.

In 1868, a skeletal mount of Hadrosaurus was erected at the Philadelphia Academy of Natural Sciences, making it the first dinosaur skeleton to be mounted in the world.  Since the skull was never found, a skull was sculpted based somewhat on modern iguanas, since dinosaurs were thought to be more closely related to lizards during that time, given the little information that was known.  It was also, however, posed standing on its hind legs which was previously unheard of for reptiles, let alone dinosaurs.  We now know that Hadrosaurus would have definitely been able to stand and walk on its hind limbs and despite the fact that a skull was never actually found, it almost certainly had a broad, flattened beak of some sort like the rest of its hadrosaur kin.

Photograph of the original Hadrosaurus skeletal mount.  Note the lizard-like skull.

Exactly how the beak and the shape Hadrosaurus' skull would have looked is somewhat of a mystery, but according to the most recent studies done on the hadrosaurid family, Hadrosaurus appears to be one of the more basal of the "true duck-billed" dinosaurs, called the hadrosaurines.  This means that it was less related to the lambeosaurine hadrosaurs, which are known for having elaborate crests, like Parasaurolophus, and was closer to the more broad-billed hadrosaurs, like Edmontosaurus.  The dinosaurs most closely related Hadrosaurus within this group have slightly downturned snouts, like that of Maiasaura, which lived a few million years after Hadrosaurus, so Hadrosaurus' skull may have looked similar.

Hadrosaurus skeletal mount on display at the Academy of Natural Sciences.  Skull is a cast of a relative, Maiasaura.

When the subject of paleontology comes up in a casual conversation (because when you hang out with dorks like me it does a lot) most envision people digging in deserts out west in states like Utah, New Mexico, or the Dakotas.  While this is true in a lot of cases, ground zero for American dinosaur fossil sites is actually in a wooded area in little old New Jersey.  Because of this, New Jersey was the first state to give itself an official state fossil, Hadrosaurus.  This means that we have two state dinosaurs, because our state bird, the Goldfinch, is a dinosaur...because birds are dinosaurs.

A dinosaur.

References

Gallagher, W.B. (2005). "Recent mosasaur discoveries from New Jersey and Delaware, USA: stratigraphy, taphonomy and implications for mosasaur extinction." Netherlands Journal of Geosciences, 84(3): 241.

Prieto-Márquez, A. (2011). "Revised diagnoses of Hadrosaurus foulkii Leidy, 1858 (the type genus and species of Hadrosauridae Cope, 1869) and Claosaurus agilis Marsh, 1872 (Dinosauria: Ornithopoda) from the Late Cretaceous of North America". Zootaxa 2765: 61–68.

Prieto-Marquez, A., Weishampel, D.B. and Horner, J.R. (2006). "The dinosaur Hadrosaurus foulkii, from the Campanian of the East Coast of North America, with a reevaluation of the genus." Acta Palaeontologica Polonica, 51(1): 77–98.

Xing, Hai, et al. “Supplementary Cranial Description of the Types of Edmontosaurus Regalis (Ornithischia: Hadrosauridae), with Comments on the Phylogenetics and Biogeography of Hadrosaurinae.” Plos One, vol. 12, no. 4, 2017, doi:10.1371/journal.pone.0175253.

Friday, March 22, 2019

Prehistoric New Jersey: Woodbury Formation

I am proud to have been born and raised in New Jersey.  Not because our bagels are the best, or because our pizza is just as good as New York's (it's true). I never really listened to Sinatra that much nor did I ever watch more than a few episodes of The Sopranos.  I'm proud to be from New Jersey because it is the site of the first scientifically-recognized fossil dinosaur.  Furthermore, New Jersey was the first state to adopt that dinosaur, Hadrosaurus foulkii, as its official state fossil.  As a dinosaur-crazed kid, of course I knew all the staples, like Tyrannosaurus and Triceratops, but Hadrosaurus and Dryptosaurus (second fossil dinosaur found in New Jersey), were also part of my off the cuff repertoire.

All this being said, it wasn't until recently that I finally made the pilgrimage to the site where Hadrosaurus was found.  I don't really have a good excuse why it didn't happen earlier.  I suppose it was one of those situations where I kept putting it off because I knew it was always going to be there.  Regardless, today, we are going to recap the site and what it has to offer for anyone who chooses to visit.

The site is called the Woodbury Formation and is located in Central New Jersey, in a town called Haddonfield.  The town is named after Elizabeth Haddon, one of its earliest settlers.  Hadrosaurus' genus name translates to "bulky reptile" however.  I don't know if the similarity between the dinosaur's name and the town's name was a coincidence or not to be honest.

In the middle of downtown Haddonfield, an almost-life-size statue was erected in the early 2000s of Hadrosaurus.  The statue is reasonably accurate for its time, although there are a few glaring inaccuracies.  It's lacking a defined beak, which Hadrosaurus, and all members of its family would have had in life, being most notable.  I was told the artist was inspired by horse mouths when sculpting the Hadrosaurus, which explains the fleshy lip-like look.  The nostrils are a bit too far to the sides and don't really reflect where the nostril holes would have been on a real hadrosaur skull.  The overall body shape is clearly based on the actual skeleton, but also is a bit too skinny, exemplifying the "shrinkwrapped" look many dinosaur reconstructions of the 90s and early 2000s had.  We now know these kinds of dinosaurs would have been much meatier in life especially in the neck and tail regions.  Overall, however, the statue is pretty awesome.  I like the skin texture that was put into it, including the scallop-shaped ridges going down the back and the folds where the neck meets the shoulders.  I also like its sense of movement.  It's not too crazy, but it doesn't look like it's just sitting there doing nothing either.  Despite its inaccuracies, it's very lifelike.

Hadrosaurus statue in the middle of downtown Haddonfield.  A bit outdated by today's standards, it is still a decent representation of the animal.
You can tell from the proportions and even by the fingers and toes that a real hadrosaur skeleton was carefully referenced when this statue was being made.  I just wish it had an actual beak.

My next stop was only about a mile away down the road to the actual site where the Hadrosaurus bones were discovered.  When most people envision a paleontology dig site, they picture an arid desert.  America's first dinosaur, however, was discovered in a heavily forested riverbed.  Since its discovery in the 1800s, the area was taken over by suburbs, but the actual site is still there and marked at the end of a quiet dead end flanked by houses.   When you first pull up, there is a picnic table with an army of plastic dinosaur toys which I'm assuming are for the public to steal play with.  There is a large information sign with a diagram of Hadrosaurus' known skeleton, some information about its discovery, and a beautiful little plaque on a rock commemorating the area.  Then there is a steep, ivy-covered hill that leads into a shallow creek bed where the bones were found!

The site as you pull up at the end of a quiet residential culdesac.
There is a picnic table with toy dinosaurs for me kids to play with at the site.  I recognized the Brontosaurus from Tyco's 1990s Definitely Dinosaurs line, as well as "Bruton", the Iguanodon from Disney's movie from 2000, Dinosaur.  
The plaque on the rock in the middle of the site has what looks like a tiny version of the statue in the downtown area.

It's a far shot from the big scorching desert sites we are used to imagining today, but this is how dinosaur paleontology in the United States began.  I think the memorials reflect it perfectly: peaceful, quiet, modest, but nevertheless an extremely important moment in history that would forever change the way we look at our earth's past, and the animals that lived there.

Just past the plaque there is a steep hill that leads down into a creek in the forest below, where the Hadrosaurus bones were discovered in the 1800s that would spark the American Dinosaur craze that persists to this day.

If you're ever in central New Jersey, come visit Haddy's site.  It's a quiet, peaceful pilgrimage every dinosaur fan should make!

Tuesday, March 19, 2019

Metriacanthosaurus: Beast of the Week

This week we will be checking out a mysterious European meat-eater, Metriacanthosaurus parkeri!

Metriacanthosaurus was a meat-eating dinosaur that lived in what is now England, during the middle Jurassic Period, about 160 million years ago.  Unfortunately, this dinosaur is only known from scant remains, but its overall adult size would have been somewhere between twenty five and thirty feet from snout to tail, judging by the bones we do have.  The genus name translates to "Moderately-spined reptile".  This is because its back vertebra were taller than most other theropods known at the time,, but still shorter than certain dinosaurs that had extreme versions of this trait, like Acrocanthosaurus or Spinosaurus.  As it turns out, The neural arches on Metriacanthosaurus weren't really that unusually tall as more and more different kinds of theropods were unearthed. 

Life reconstruction of Metriacanthosaurus in watercolors by Christopher DiPiazza.  This is mostly speculation.

Sadly, Metriacanthosaurus is only known from a partial skeleton, including part of the pelvis, some vertebra, and part of the leg.  However, this was certainly enough for paleontologists to identify it as a kind of large carnivorous dinosaur.  At the time, in the 1920s, Megalosaurus was the closest known relative so Metriacanthosaurus was lumped with it.  As years went on, and a greater variety of theropod dinosaurs was found and there were more specific anatomical characteristics to compare, Metriacanthosaurus was placed in its own family.

Drawings of Metriacanthosaurus' vertebra and hip bones from Walker's 1964 paper.

Sadly, Metriacanthosaurus' skull was never found, but based on the bones we do have of it, as of now it is considered most closely related to other large meat-eating dinosaurs within its family, called metriacanthosauridae. Most notable are two Chinese dinosaurs, called Yangchuanosaurus and Sinraptor.  If it was anything like its closest relatives, Metriacanthosaurus would have had a relatively short and deep skull, with proportionally long, backwards-curving teeth, ideal for tackling large prey, like other kinds of dinosaurs.

References

Walker, Alick D. (1964). "Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences248: 53–134. 

von Huene, F. (1923). "Carnivorous Saurischia in Europe since the Triassic". Bulletin of the Geological Society of America34: 449–458.

Naish, DarrenMartill, David M. (2007). "Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia". Quarterly Journal of the Geological Society164: 493–510.


Monday, March 11, 2019

Vaderlimulus: Beast of the Week

Today we will be looking at an invertebrate who's lineage is ancient even compared to the dinosaurs.  Let's check out Vaderlimulus tricki!

Vaderlimulus was a prehistoric horseshoe crab that lived in what is now Idaho, USA, during the early Triassic Period, about 245 million years ago. (But I should note that horseshoe crabs in general go back over 400 million years!) The specimen on the fossil record measured about four inches long, and like horseshoe crabs today, was likely a scavenger, feeding on dead organic material that sinks to the bottom of whatever watery habitat it was living in.  The genus name translates to "Vader horsehoe crab" after Darth Vader from the Star Wars franchise.  It was named this way because the unique shape of the creature's shell resembles the sides of Darth Vader's famous helmet.

Vaderlimulus tricki life reconstruction by Christopher DiPiazza.

Vaderlimulus' claim to fame is its amazingly-shaped front portion of its shell, which was extremely wide and tapered into a backwards-facing point on each side.  It's uncertain why the animal evolved this way?  Horseshoe crabs today use their wide, rounded front shells to help stabilize themselves as they trek muddy or gravelly bottoms of the brackish and salt water habitats they live in.  The wide shells make them less likely to flip over if a strong current hits them or if they bump into a rock or something too hard.  Even if they do get flipped, they can arch their backs and use their stiff tails (which are not weapons by the way) to help them flip back over.  We know Vaderlimulus lived in what was at the time a partially freshwater environment, so maybe there was a more consistent or stronger current that would have required it to be more stabilized with the wider shellgear.

Like all horseshoe crabs, Vadelimulus had two compound eyes on the top of its shell, and likely had a series of tiny, barely noticeable eyes around the perimeter of the front of its shell.  Under that first body segment, it had ten legs, armed with small pinchers for picking up tiny morsels to eat.  In the center of those legs it would have had a small mouth.  The segment following the front part housed the shingle-like gills on the ventral side, followed by the stiff tail.  Horsehoe crab tails, like stated earlier, are primarily for stabilization, and are not dangerous at all.

Specimen of Vaderlimulus tricki currenly housed at the New Mexico Museum of Natural History and Science.

Like its modern relatives, Vaderlimulus, probably walked onto land to breed.  When modern horseshoe crabs do this today, the females lay their tiny green eggs in the sand and the males fertilize them.  Males often grab hold of the back end of the females with specialized front legs that look like boxing gloves with hooks, in an effort to fertilize the eggs as soon as they are released.  Because of this, females are larger than the males so they can be strong enough to carry their smaller partners as they move around in the surf.  It also helps to have a larger body to produce as many eggs as possible.

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


References

Allan J. Lerner et al. 2017. First fossil horseshoe crab (Xiphosurida) from the Triassic of North America. Neues Jahrbuch für Geologie und Paläontologie 286 (3): 289-302; doi: 10.1127/njgpa/2017/0702