Lesson 1 Dino 101 2024.pdf

Lesson 1: Appearances and Anatomy Written by W. Scott Persons, Victoria Arbour, Matthew Vavrek, Philip Currie, and Eva Koppelhus Learning objective for lesson 1: Learning objective 1.1: Describe sizes of Students will learn about the dinosaurs by compari...

Lesson 1: Appearances and Anatomy Written by W. Scott Persons, Victoria Arbour, Matthew Vavrek, Philip Currie, and Eva Koppelhus Learning objective for lesson 1: Learning objective 1.1: Describe sizes of Students will learn about the dinosaurs by comparing modern organisms to dinosaurs diversity in dinosaur appearances, both bony and soft tissue structures, and will be able to Although the most well known dinosaurs tend identify major features of the major to be enormous, multi-ton animals, dinosaurs actually came in a wide variety of sizes. groups of dinosaurs. Although birds are the smallest dinosaurs that we know of, we still have many examples Welcome to Dino 101! In this course you will outside this group of living dinosaurs that were explore the anatomy, ecology, and evolution of no larger than a house cat. For example, the one of the grandest and most fascinating animal small dinosaurs Microraptor and Fruitadens groups to ever walk the earth. The study of were probably less than a metre long as adults, dinosaurs is a subdivision of the branch of and weighed less than a kilogram. One possible science known as palaeontology. Palaeontology reason people may think dinosaurs are larger is the study of all prehistoric life. A than they are is because they are often palaeontologist’s knowledge of prehistoric life “inflated” in pop culture. For example, many comes primarily from fossils. A fossil is any people know of the large, predatory preserved evidence left behind by a prehistoric Velociraptor from the Jurasic Park franchise. organism. The word fossil literally means “dug However, in reality Velociraptor was about the up”, and fossils are usually objects or structures size of a dog or a turkey, not a human. Some of found buried in ancient rock formations. the biggest dinosaurs were truly enormous Dinosaur fossils include footprints, eggshells, though. Many of the long-necked sauropod coprolites (fossil poop), and in rare instances dinosaurs were bigger than any land animal even skin and feather impressions. However, today, and the only living animals that come most dinosaur fossils are bones. Bones are close to them in size are whales. partially made of minerals, which do not decay Learning objective 1.2: Identify major as easily as flesh and other soft tissues. For this bones and bone types in dinosaur reason, bones have a much greater chance of skeletons being preserved as fossils, and a dinosaur palaeontologist needs to know a great deal Adaptations are traits that have evolved about bones. because they serve specific functions. Bones are adaptations that help animals to survive by serving four major functions. First, bones passively resist gravity and maintain an animal’s University of Alberta - PALEO 200/201 form. When you stand up straight, the bones in evolved over 500 million years ago. Animals your legs act like support columns. Your leg that lack vertebrae are called invertebrates, bones support your weight, without your and include animals like insects, spiders, snails, muscles needing to actively flex and expend squids, clams, jellyfish, and worms. Since the energy. Second, bones provide a ridged origin of animal life, there have always been framework for muscle attachment. Raise your many more species of invertebrates than right hand high over your head. When you do, vertebrates. However, vertebrates are more you can feel muscles in your shoulder flexing. numerous when it comes to species of large The bones in your shoulder girdle provide a animals, especially on land. This success is solid anchor against which your shoulder probably related to the vertebral column’s muscles can pull, and long bones in your arm ability to passively support weight and to allow it to move as single stiff unit. Third, bones anchor enlarged muscles. provide protection and can also be major components of horns and other robust Skulls and Jaws The skull is not a single bone. Rather, the skull is weapons. For example, your skull bones form a made up of many bones that are tightly locked natural helmet that protects your brain -- a together. More than any other part of the delicate organ that could be seriously damaged skeleton, a skull can give a palaeontologist great by an impact with an unexpectedly low insight into a dinosaur’s life. The upper and doorway or rogue baseball. Finally, bones store lower jaws may contain teeth and/or include a mineral reserves. Often the resources that an beak, and they are critical for interpreting what animal needs to grow and develop are plentiful a dinosaur was adapted to eat. The rear portion at one time and rare at another. During times of of the skull includes the brain case. The brain plenty, animals may store a valuable mineral case is a hollow chamber formed by multiple resource, such as calcium, by growing a new skull bones that houses the brain. There are bone deposit or by increasing the density of many small openings into the brain case. Nerves already existing bone. Later, during a time when pass through these opening and connect to the the resource is scarce, the animal may gain brain. The size and shape of a brain case can access to stored minerals by reabsorbing some indicate the size and shape of the brain that it of its bone. housed, and, therefore, can provide clues to a dinosaur’s mental capabilities. Dinosaurs belong to a group of animals known as vertebrates (and so do you). Vertebrates are Dinosaur skulls also have multiple pairs of large animals that have two special kinds of skeletal openings. The nares (singular: naris) are the adaptations: skulls and vertebrae. Vertebrae pair of openings for the nostrils. The orbits are (singular: vertebra) are structures made the pair of openings for the eyes. In some primarily of bone and/or cartilage that surround animals, like turtles, there are no other large a portion of the spinal nerve cord. Together, skull openings, but dinosaurs have several. vertebrae interlock with each other in a series These additional skull openings are called and form the vertebral column. Fish, fenestrae. The word “fenestrae” (singular: amphibians, turtles, snakes, birds, and fenestra) is Latin for “windows”. Behind each mammals are all examples of vertebrates. The orbit, dinosaurs have two fenestrae: the first vertebrates were aquatic animals that 2 University of Alberta - PALEO 200/201 fenestrae on the lateral sides of the skull are called the centrum. Above the centrum is the called the laterotemporal fenestrae and the neural arch, which covers the neural canal. The fenestrae on the top of the skull are called the neural canal is the opening in each vertebra, supratemporal fenestrae. Both the through which the spinal nerves run. A vertebra laterotemporal fenestrae and the may also have processes extending from the supratemporal fenestrae provide extra room for centrum or neural arch. Vertebral processes large jaw muscles. Between each orbit and provide attachment surfaces for muscles and naris, dinosaurs have a third fenestrae pair, sometimes provide articulation surfaces for called the antorbital fenestrae. The function of ribs. Two common types of vertebral processes the antorbital fenestra is unclear. They may are transverse processes, which extend from have simply been adaptations that made the lateral sides of the vertebrae, and spinous dinosaurs skulls lighter, or they may have also processes, which extend upwards from the housed large sinus cavities that helped warm neural arch. the air that dinosaurs breathed. Throughout the vertebral column of any animal, the shapes of individual vertebrae vary. In many animals, like most fish, this variation in vertebral shape is slight. However, in animals like dinosaurs and mammals, vertebrae in different regions of the vertebral column have strikingly different shapes. Vertebrae in the neck are called cervical vertebrae. Cervical vertebrae often have extra-large openings for blood and nerve channels and are adapted to support the weight of an animal’s head. Vertebrae in the back are called dorsal vertebrae. Dorsal vertebrae often have tall spinous processes and large rib articulation surfaces. Vertebrae in the hips are called sacral vertebrae. Because the pelvic bones in Tyrannosaurs rex skull showing different terrestrial vertebrates serve as solid anchors for fenestrae. Original image by Scott Hartman, powerful leg muscles, the pelvic bones (later modified by M. Vavrek. discussed in detail) are fused to the sacral vertebrae. To further increase the strength of the hips, the sacral vertebrae are also fused The Axial Skeleton with one another and form a single solid bone The vertebral column, or spinal column, is structure called the sacrum. Finally, vertebrae comprised of a series of interlocking vertebrae in the tail are called caudal vertebrae. that begins with the first vertebra in the neck Underneath caudal vertebrae are bones called and ends with the last vertebra in the tail. chevrons. Chevrons protect a large blood and Nearly all vertebrae share a basic form. A nerve channel and provide support for tail vertebra has a spool- or disk-shaped body, muscles. 3 University of Alberta - PALEO 200/201 In dinosaurs, cervical, dorsal, sacral and caudal Between the shoulder and elbow is the largest vertebrae may all support ribs (although, in the bone in the forelimb, called the humerus. tail, ribs are usually only present at the base Between the elbow and the wrist are two and are tightly fused to vertebrae). The largest parallel bones, called the radius and ulna. In ribs are those that connect to the dorsal most tetrapods, the radius is the thinner of the vertebrae and form the ribcage. In dinosaurs, all two. The bones in the wrist are called carpals. dorsal vertebrae connect with ribs; however, in The bones between the wrist and fingers are mammals, the dorsal vertebrae close to the hips called metacarpals. Finger bones are called do not. Also unlike mammals, some dinosaurs phalanges. The arrangement of bones in the had gastralia, or “belly ribs”. Gastralia are small hindlimbs is very similar to that in the forelimbs. ribs positioned across a dinosaur’s underbelly, Between the hip and knee is the largest bone in underneath the ribcage. the hindlimbs, called the femur. Between the knee and the ankle are two parallel bones, The Appendicular Skeleton called the fibula and tibia. The tibia is the bone Dinosaurs, mammals, reptiles, and amphibians that forms our shin. If you've ever broken a all belong to a special group of vertebrates bone in your leg or ankle, there's a good chance known as tetrapods. “Tetrapod” means “four that you broke your fibula, which is the thinner feet”. Tetrapods are animals that evolved from or the two lower leg bones. The bones in the an ancient ancestor with four feet and four ankle are called tarsals. The bones between the limbs. Most tetrapods still have four feet and ankle and toes are called metatarsals. Finally, limbs, although some, like humans, have hands the bones in the toes are called phalanges (the instead of front feet and some, like snakes, same name as the bones in the fingers). have lost their limbs altogether. The same pattern of bones in the limbs is The limbs of a tetrapod are connected to the shared by nearly all tetrapods. Changes in the rest of the skeleton by limb girdles. The proportions of the limbs, or in the proportions forelimbs connect to the pectoral girdle, also of particular limb bones, or in limb posture can called the shoulder girdle. The scapula, or have a major impact on how a tetrapod moves. shoulder blade, is the largest bone in each side For instance, when we human stand and walk, of the pectoral girdle. The hindlimbs connect to our heels touch the ground. When dinosaurs the pelvic girdle, or hip bones. Each side of the stood and walked, only their toes touched the pelvic girdle is composed of three bones that ground. The metatarsals of dinosaurs (which are tightly connected to one another. The upper hip located in the flat of our feet) were tilted bone is called the ilium. It is to the ilium that upwards and contributed to the length of a the sacral vertebrae are fused. Below the ilium dinosaur’s leg. This helped dinosaurs to take are the pubis and the ischium. The pubis is longer steps and probably allowed many positioned in front of the ischium, nearer the species of dinosaurs to run much faster than belly, and the ischium is positioned behind the humans can. pubis, nearer the tail. The acetabulum is the depression or (as in dinosaurs) the hole in the pelvic girdle into which the hind limb articulates. 4 University of Alberta - PALEO 200/201 Learning objective 1.3: Identify the two their ancestor, others have changed it. For major types of pelves in dinosaurs. instance, despite being the namesake of term “ornithischian”, birds are not ornithischians -- Skeletal differences and similarities are used to birds are not “bird-hipped” dinosaurs! Birds are sort dinosaurs into groups. There are two major part of a special group of saurischian dinosaurs groups of dinosaurs: saurischians and that changed their pubis from extending ornithischians. Within each of these two major forward to extending backwards (unrelated to groups there are many smaller groups. the similar hip shape of the ancestor of Saurischian dinosaurs are those that share an ornithischian dinosaurs). Here is another evolutionary ancestor that had a pubis that potential complication: saurischians and extended downwards and forwards, towards ornithischians share a common ancestor with the ribcage. Ornithischian dinosaurs are those each other, and palaeontologists are not sure that share an evolutionary ancestor that had what this ancestor was like, whether it had both a special beak-forming bone in the upper more ornithischian or saurischian traits, or jaw (called the predentary) and a pubis that some mosaic of the two. extended downwards and backwards, towards the tail. Learning objective 1.4: Identify the Be careful. “Saurischian” and “ornithischian” major bony features of general dinosaur groups. are basic and very old terms, but they can be confusing. “Saurischian” means “lizard hipped”, and “ornithischian” means “bird hipped”. These Saurischians terms were used because in a lizard’s hips the There are two major groups of saurischian pubis extends downwards and forwards and in dinosaurs: sauropodomorphs and theropods. a bird’s hip the pubis extends downwards and Sauropodomorphs were large herbivores with backwards. Remember, these groups are based elongated necks and relatively small heads. on the pubis shape of a shared ancestor. The Prosauropods were an early group of groups were named before it was recognized sauropodomorphs and were the first group of that birds are living dinosaurs. While some large-bodied herbivorous dinosaurs to evolve. dinosaurs still have the same pubis shape as Massospondylus by Joy Ang 5 University of Alberta - PALEO 200/201 Diplodocus by Joy Ang Sauropods were a later group of Theropods were bipedal saurischian dinosaurs sauropodomorphs. Many sauropods attained that shared a carnivorous ancestor. Many truly gigantic size, and the group includes the theropods were carnivorous and have serrated largest animals to ever walk the earth. blade-like teeth and sharp hooked claws, but Sauropods stood on four robust and column- some were herbivorous and a few lack teeth like legs. Sauropod vertebrae (particularly the altogether. Birds are a kind of theropod, making cervical vertebrae) are filled with complex air theropods the only group of dinosaurs that is sacks, which helped to reduce weight. The teeth not completely extinct. of sauropods are usually simple and peg-like. Gorgosaurus by Joy Ang. Ornithischians that created more space in the ribcage. This The backwards extending pubis, which gives extra space was probably filled by extra-large ornithischians their name, was an adaptation digestive organs. Plant matter is much harder to 6 University of Alberta - PALEO 200/201 digest than meat, and most herbivores need larger stomachs and intestines than do carnivores. All known ornithischian dinosaurs are thought to have been primarily herbivorous. The beaks, which all ornithischians possess, are also herbivorous adaptations that helped ornithischians to chop off large mouthfuls of Corythosaurus by Joy Ang vegetation. There are five major groups within the ornithischians: ornithopods, Pachycephalosaurs were bipedal with short pachycephalosaurs, ceratopsians, stegosaurs, arms, unusually stout and strong tails, and and ankylosaurs. armored skulls. Some pachycephalosaurs have thick, domed skull roofs and backwards- Ornithopods include a wide range of dinosaurs pointing horns. The function of that lack armor and that either walked bipedally pachycephalosaur skull armor will later be all the time or assumed a bipedal stance when discussed in detail, but it has long been running. Many ornithopods are small antelope- speculated that pachycephalosaurs may have sized dinosaurs, but some, like the iguanodonts rammed predators or have butted heads with and hadrosaurs, grew to be multi-ton giants. each other in competitions for territory or Iguanodonts are large ornithopods with a spike- mating rights. Pachycephalosaurs have sharp shaped claw on each hand. conical teeth in the front of their mouths, behind their beaks, and leaf-shaped teeth in the rear. These front teeth have led some palaeontologists to hypothesize that pachycephalosaurs might have been omnivores (adapted to eat meat as well as plants). Iguanodon by Joy Ang Another group of large ornithopods, hadrosaurs, are the famous “duckbilled dinosaurs”. Hadrosaurs evolved late in the history of dinosaurs, but were highly successful. Some hadrosaurs have elaborate boney crests, Pachycephalosaurus by Joy Ang and all hadrosaurs have strikingly large beaks in the front of their mouths and dense, tightly Ceratopsians are another group that evolved packed rows of small teeth in the rear of their late in the history of dinosaurs. Ceratopsians mouths. Together, these teeth form large have large parrot-like beaks and skulls that are chewing surfaces and are collectively referred greatly expanded in the rear. In most to as dental batteries. ceratopsians, this rear skull expansion is taken to an extreme and a large boney frill, or neck 7 University of Alberta - PALEO 200/201 shield, is present. Many ceratopsians have large Ankylosaurs are the most heavily armored of all horns and also possess dental batteries. dinosaurs. Ankylosaurs are quadrupedal with Triceratops is easily the most famous of the short legs and wide ribcages. The backs and ceratopsians and is one of the largest. Most skulls of most ankylosaurs are covered in spikey large ceratopsians were quadrupedal and have protective osteoderms. Some anklosaurs also short tails. have large osteoderms on the ends of their tails, forming a mace or “tail club”. Unlike their relatives, the stegosaurs, most ankylosaurs have short snouts and broader, rounded beaks. Triceratops by Joy Ang Stegosaurs are a group of quadrupedal Anodontosaurus by Joy Ang dinosaurs with rows of projecting osteoderm plates down their backs and long osteoderm spikes on their tails. Osteoderms are bones that develop within the skin and are a common component of animal armor. Some stegosaurs Learning objective 1.5: Discuss the soft also have osteoderm spikes on their backs and tissues of dinosaurs. over their shoulders. Stegosaur front limbs are much shorter than their hind limbs. Stegosaurs As has already been discussed, bones are the were probably not fast runners, but they could most common dinosaur fossils because bones probably pivot quickly and could rear up and decay less rapidly than do softer tissues. This stand on their hind legs. Stegosaur heads are makes it difficult to know what a dinosaur’s small relative to their bodies and their snouts integument (body covering) was like. However, are narrow. under exceptional circumstances softer tissues can be fossilized. Fossil footprints are natural foot molds that were originally made in soft, fine-grained sediments. Sometimes, a footprint may include more than just the rough outline of a dinosaur’s foot and may have impressions of foot scales. Skin impressions from other regions of a dinosaur’s body can be preserved if a dinosaur was covered by mud shortly after it died and before its flesh rotted away. Direct fossilization of skin and other soft parts is also Stegosaurus by Joy Ang possible, but such instances are exceedingly rare. 8 University of Alberta - PALEO 200/201 Dinosaur specimens that include a lot of skin A major breakthrough in the study of dinosaur fossils are often called “mummies”. The first integument came in 1996, when a small mummified dinosaurs were hadrosaur theropod specimen with fossil feathers was specimens, found in Wyoming in 1910. These discovered in Liaoning, China. This little revealed that hadrosaurs were covered with carnivorous dinosaur was called scales and that scales from different regions of Sinosauropteryx. The feathers had been the body often had different shapes. Fossil preserved, because the dinosaur’s body was scales are also known from specimens of buried suddenly by extremely fine ash from a theropods, sauropods, ceratopsians, stegosaurs, volcano. Since this first discovery of dinosaur and ankylosaurs. The scaly skin of dinosaurs has feathers, many other have been made in a slightly better chance of being fossilized than Liaoning. We now know that lots of small would our own skin, because scales are coved theropods had a covering of simple hair-like by a substance called keratin. Keratin is a tough feathers and some, like Microraptor, had but flexible material that also composes hair, feathered wings. In 2012, feathers were first feathers, fingernails, and the outside of claws, reported from the large tyrannosauroid beaks, and horns. Yutyrannus. At over a ton in weight, Yutyrannus is the largest known feathered dinosaur. Yutyrannus copyright Lida Xing, used with permission. 9 University of Alberta - PALEO 200/201 Reconstruction of Kulindadromeus, a fluffy ornithischian dinosaur from Russia. Fossils show that Kulindadromeus had a variety of integumentary structures: thin, fluffy filaments on its neck and back, feather-like structures on its upper arms and legs, unusual ribbon-like structures on its lower legs, and more typical scales on the feet and tail. Art by Tom Parker and used under the CC-BY-SA 4.0 license. Theropod dinosaurs had feathers and dinosaurs might have had some combination of filamentous integument, but what about other scales, fluffy filaments or quills, and true dinosaurs? Could ornithischians have been feathers. fluffy as well? A few tantalizing specimens unearthed over the last few years have suggested that some ornithischians might also have had feather-like integument. A specimen of the early ceratopsian Psittacosaurus preserved unusual long, stiff, bristle-like structures on its tail, but it was unclear if these were related to the feathers of birds and theropods. In 2009, a very primitive ornithischian from China called Tianyulong was Psittacosaurus by Rachelle Bugeaud. described, and this ornithischian was covered in long filaments over most of its body. The most exciting specimen, however, was just described Recall that osteoderms are bones that develop in the summer of 2014. Kulindadromeus was an within the skin, so these bones also count as early and primitive ornithischian dinosaur from integumentary structures. Osteoderms Russia, and it preserves not just simple, bristle- comprise the armor covering of many types of like filaments like those found in Psittacosaurus modern animals, including armadillos, and Tianyulong, but branching, feather-like crocodilians, and some lizards. Among structures as well! It seems likely that many dinosaurs, large osteoderms formed the plates 10 University of Alberta - PALEO 200/201 and spikes of stegosaurs and the armor and tail- Based on analyses of fossil melanosomes, it is club ends of ankylosaurs. Some sauropods also thought that the dinosaur Microraptor was a have osteoderms, although it has been glossy black, and the dinosaur Anchiornis is hypothesized that the osteoderms of sauropods thought to have been black and white with were less important for protection and more some reddish-brown on its head. important as mineral reserves. What color dinosaurs were has always been a mystery. Recently, a clever new approach has begun to try and solve this mystery, at least for some feathered dinosaurs. Feather colors are not directly preserved in fossilized feathers; however, studies of modern birds have shown that feather color is influenced by the shape and arrangement of melanosomes -- pigment cells within a feather. Under microscopic examination, melanosomes can be observed in some fossil feathers, and they give clues to a dinosaur’s true colors. Black and gray colors result from long and narrow melanosomes. Brown and reddish colors come from short and wide melanosomes. White feathers have no melanosomes. Iridescence or ‘glossiness’, like the shiny black and blue feathers of crows and magpies, corresponds to narrow melanosomes that are aligned in the same direction. Above: Bohemian waxwings (Bombycilla garrulus) in the University of Alberta Zoology Museum. Photo and diagram by V. Arbour. Left: Black-billed magpie (Pica hudsonia) in the University of Alberta Zoology Museum. Photo and diagram by V. Arbour. 11 University of Alberta - PALEO 200/201 Anchiornis by Joy Ang, colourized by V. Arbour Muscles are sophisticated tissues that produce Supplementary Materials force by contracting. Understanding dinosaur muscles is critical to understanding how Laelaps: Biggest Dinosaur Ever? Maybe. Maybe Not. dinosaurs moved. Unfortunately, muscles [Blog post] seldom fossilize. Recall, however, that one of Sauropod Vertebra Picture of the Week: Tutorial 15: the major functions of bones is to provide the bones of the sauropod skeleton, Tutorial 15a: attachment surfaces and a rigid frame work for the bones of the theropod skeleton, and Tutorial muscles. Consequently, the shapes of bones 15c: the bones of the ornithischian skeleton. [Blog often correspond to particular muscle shapes, posts] and muscles often leave behind scars on the surfaces of bones where they attached. Like the Dinosaur Tracking: The dinosaurs they are a- pattern of bones in the skeleton, the overall changin’. [Blog post] pattern of muscle arrangement is largely the same across all tetrapods. Dinosaur Tracking: Dinosaur division is all in the hips. [Blog post] Information about other soft tissues in Dinosaur Tracking: Microraptor was a glossy dinosaurs is very scarce. One exceptional dinosaur. [Blog post] specimen of a small theropod dinosaur from Italy, called Scipionyx, actually preserves the Laelaps: Fluffy dinosaur raises questions over the mineralized remains of the trachea (windpipe) origin of dinofuzz. [Blog post]. Plus, check out the in the throat, and the intestines. A red smudge high-resolution images of Kulindadromeus at Dave in the front of the belly region might represent Hone's Archosaur Musings [Blog post]. the decayed remains of the heart, liver, or spleen. Some of the muscles were also Phenomena – Surprise! Well-studied dinosaur actually had a Cock's comb. [Blog post]. Plus, see preserved, as were the keratinous sheaths over how we studied this specimen in Peering inside a the claws. dinosaur mummy [Video]. 12