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 Tyrannosaurus.  Dryptosaurus 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.

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!