Allosaurus- My Favorite Dinosaur (May 2018 Monthly Fossil)

this month's fossil is Allosaurus one of my favorite dinosaurs all right I got something really special today for this month's fossil [Music] so I got a really cool fossil for this month's fossil this is Allosaurus this is a arm of an Allosaurus and one of my most favorite dinosaurs and this was a specimen that was collected about 20 years ago and prepared by an elder who was a paleontologist at Dinosaur National Monument and described by dam curry in a paper that came out in 2001 and this is a hand and wrist of an Allosaurus so over here we have this bone here is the humerus there's the upper arm bone and we have the ulna and the radius we have two little bones in the wrist this is the radial and semi lunate and then we have the three metacarpals the make-ups or the palm of the hand and then we have the phalanges that come out here the big claw is missing on this hand we just have the second phalanges but we have the other two claws up here so there have been two other phalanges in a big claw over here this might have been part of that cloth but this gives us a really cool picture of what's going on in the wrist now dinosaurs are related to birds and one of the neat things about this wrist is it's sort of a transitional fossil between what you see in birds and what you see in earlier dinosaurs so we have these two bones this one here that's next to the radius is the radio and it acts as a pulley for a tendon that would allow the hand to move sort of back and forth in this direction now this is an important movement for birds in folding their wings and the and the radio in this Allosaurus provides this really nice pulley tennis system to allow that back-and-forth movement if you ever look at bird wings that's a very important lever point we're the folding of the wing as it folds out and back now what Allosaurus has with the semi loony is it doesn't look like a Halfmoon which is what it looks like in birds but it looks like it has this double saddle shape and so there's articulation this direction articulation this wear direction where the bones come together and this allowed two directions of movement both the movement in the folding of the wing but also gripping so the ability to grip prey and so with that articulation there allosaurus key grip prey with these really strong claws and hand but it also could fold its wing or its arm its hand down like you see in modern birds and so this would have shifted down and you can kind of see that along there now another thing I as looking at this specimen is to see if we see any bumps along the ulna Velociraptor is thought to have feathers because of bumps that are found along the ventral surface of the the ulna and I don't see any bumps so though there is some looks like there's some a little bit of scars on it but I don't see any real clear indications of bumps that we've come down here indicating that this arm went might have had some feathers coming down from it like you see in Velociraptor so we don't see any of that but we do see this very interest in the wrist it's very similar to what we see in birds so this cast is made out plaster which means it's kind of fragile and it's kind of heavy and I want to use this for educational purposes to take to school groups where it might get might get handled quite a bit so instead of taking this plaster cast I'm gonna make a resin cast from this so I'll cover this in latex and make a mold and then a mother mold and plaster over that and then we're gonna pour in resin so we can get a nice statcast they'll be much lighter more resistant to transportation and we're and kids handling it and touching it and so so that's what I'm going to work on yeah [Music] all right so we've let our cast dry for a few days and it's changed color it's now kind of an orangish color and it's a we're able to peel it up so very carefully I'm gonna peel this and see if it works all right so we got our rubber mold here very exciting all right so now we have our floppy rubber mold but because it's so sloppy we're going to make a mother mold of this I'm just gonna kind of set it back on this so that we can then make our mother lode mold over this all right to make the mother lode the first thing we're gonna do is we're gonna add some saran wrap for add a couple layers here all right yeah I put some cardboard down because this will be messy clean up a little easier and I'm gonna put on some gloves since I know I need this plaster sticking to my my fur and all of our sleeves and I got some cheesecloth here they can put over this kind of like if you ever broken a bone and had to have a cast made we're doing kind of the same thing he's kindly it on here and we want to do is form a nice hard mother mold that will help to hold that floppy latex mold in place when we make the cast all right so what I've done here is I flipped over the mold and the mother mold so we're looking at the bottom which will now be our top and so now the trick is going to be to pour the resin that will make the cast into the mold and I've been very careful to try to make this as level as possible so hopefully it will be thick enough and they got this great box here too to work with definitely gonna do this batches so this wrist joint in Allosaurus allowed it to do two motions one is it was able to grip or grab things in this sort of motion which would be very useful if you're a predator and trying to pounce on prey and grab a hold of it and eat a prey item now the other motion is a bit unusual and that is is that it was able to do a motion that of course humans can't do but that is to take the hand and move it in this joint so that my pinkie would come and touch my my wrist down here so this motion this angled motion is really interesting because it wouldn't necessarily serve any purpose in capturing prey and to be a carnivorous dinosaur but did have a function that is really interesting and was probably a precursor to the development of wings that you see him and later in birds and I brought my really awesome t-shirt to illustrate the evolution from dinosaurs to birds but this wrist motion that had a precursor to flight in for development of the wings and that has to do with that motion coming out and providing a broader surface for the brooding of eggs we're going to show you why the Allosaurus might have turned its arm that way it has to do with brooding eggs this is my chicken and by keeping the arms folded in their tucks the arms away but it also keeps the arms out and this helps eggs the eggs today no eggs today but that's what are the reasons why having the arms hold up like that would be beneficial thanks for attack the rooster is there man he is pissed off today so by being able to bring your arms down like this it provided a greater surface area to all kind of warm the eggs on a nesting on a nest with the mother nesting and so by bringing those hens down this create a wonderful sort of dome over the nest of eggs to keep it nice and warm and that was what the real purpose of that joint was was for a ability to bend the arm down and provide that dome-like area now possibly Allosaurus was feathered or not we don't have any direct evidence of feathers in Allosaurus but there is a good possibility that there would have been feathers coming off of those those arms like you see in Velociraptor and other later theropods and that would have provided a nice warm surface for those incubating eggs

Channel: Benjamin Burger

Views: 2,795

Rating: 4.972414 out of 5

Keywords: Allosaurus, Dinosaur, Dinosaurs, Jurassic, Wrist, Anatomy, Fossil, Cast making, Mould Making, Makers, Paleontology, Geology, Fossils, Reconsturctions

Id: s6gRc_wIcZ0

Length: 13min 53sec (833 seconds)

Published: Wed May 30 2018