Topic questions

Who invented the term Dinosauria What was his idea about dinosaur metabolism 2. In relation to paleontology, what is meant by the edge and the wedge 3. Describe a dinosaur as imagined by Victorian paleontologists. What changed our ideas from the Victorian conception 4. Describe the kinds of vertebrate faunas that existed just before dinosaurs became the most abundant and diverse terrestrial vertebrates. 5. What were the dramatic revolutions that changed the face of paleontology after the 1960s...

Intraspecfic Competition Of Marginocephalians

Marginocephalia consists of the bipedal Pachycephalosauria, the dome-headed ornith-ischians, and the quadrupedal Ceratopsia, the horned, parrot-beaked, frilled ornithischians. The group was largely restricted to the Cretaceous of Asia and North America, and is diagnosed by the presence of a variably-sized shelf that formed along the back of the skull. Figure 6.31. Cladogram of ceratopsians superimposed on a map of North America and Asia, showing migration of more derived forms to North America....

Prehistoric Creatures Life Dinosaurs Genera

Although there has been considerable speculation about what happened to the non-avian dinosaurs at 65.5 Ma, any meaningful hypothesis must operate within the bounds of science it must be testable and it must explain as much of the data as possible. Given those constraints, only one hypothesis matches what is known about the K T extinction the hypothesis that an asteroid hit the Earth 65.5 million years ago and killed many organisms, including the non-avian dinosaurs. The evidence for a large...

Dinosaurs all wrong for mass extinctions

What are some of the problems with reconstructing changes in dinosaur populations over time For one thing, dinosaurs are, by comparison with foraminifera for example, large beasts and, more importantly, not particularly common.1 For this reason, the possibility of developing a statistically meaningful database is impractical, and rigorous studies of dinosaur populations are very hard to carry out. Just counting dinosaurs can be difficult. Mostly, one doesn't find complete specimens, and...

The skinny on skin

Until recently, most researchers thought that all (non-avian) theropods were covered with scales of some sort. The only direct information on theropod skin came from the South American neoceratosaur Carnotaurus, whose skin was covered with an array of tubercles, or bumps of modest size surrounded by smaller rounded scales. When birds and other exceptionally well-preserved fossils began showing up in China in the mid 1990s, paleontologists recognized apparent feathers and feather-like structures...

Terrestrial record

For better or worse, virtually all of what we know of the K T boundary on land also comes from the Western Interior of North America (Figure 15.11). There, several well-studied, complete sections have provided the best insights available into the dynamics of the extinction. Figure 15.11. The K T boundary in eastern Montana, USA. The boundary is midway up the butte, right at the dotted line. Below is the dinosaur-bearing latest Cretaceous Hell Creek Formation above is the Tertiary Fort Union...

A unique conceptual approach

Dino factoids - names, dates, places, and features - are available in zillions of books and websites. We depart from a Who What Where approach to dinosaurs, instead building a broad understanding of the natural sciences through the power of competing scientific hypotheses. Unique among dinosaur textbooks, Dinosaurs is rooted in phylogenetic systematics. This follows current practice in evolutionary biology, and allows students to understand dinosaurs as professional paleontologists do. The...

Triceratops spoils or spoiled Triceratopsl

Lambe ofthe Geological Survey ofCanada suggested that Gorgosaurus was not so much an aggressive predator, but instead maintained its sustenance by scavenging. The basis for his remarks was the apparent absence of heavy wear on the teeth of this theropod - these animals therefore must have fed primarily on the softened flesh of putrefying carcasses. This interpretation has appeared on and off again in discussions oftheropod diet and hunting behavior, frequently enough to be...

When did dinosaurs live and how do we know

Fossils, including dinosaur remains, are found in layers of rock, commonly called strata. The field of stratigraphy is the geological specialty that tells us how old or young particular strata are thus, stratigraphy is a means of learning the age of dinosaur fossils. Stratigraphy is divided into chronostratigraphy or time stratigraphy (chronos - time), lithostratigraphy or rock stratigraphy (lithos - rock), and biostratigraphy or stratigraphy as indicated by the presence of fossils (bios -...

Archaeopteryx as a bird

Archaeopteryx was immediately recognized as a fossil of the most primitive bird known. The feathers identified it as a bird, as indeed many other features, particularly the stance, legs and feet, were remarkably bird-like, and, together with living birds, Archaeopteryx forms a monophyletic Avialae (Figure 10.6). But where did Archaeopteryx come from Figure 10.5. A reconstruction of Archaeopteryx, surrounded by photographs taken from the actual specimens. (a) Skull, seen from right side, note...

Young Turks and old turkeys

It's funny, University of Oregon paleopedologist Greg Retal-lack once said, how quickly today's 'Young Turks' become tomorrow's old turkeys. The young, fire-breathing revolutionaries themselves become advocates of established dogma, as, even in their own lifetimes, their ideas are challenged and swept aside by a righteous, new, young, aggressive generation of scientists. It was that way in Richard Owen's day, and it is that way now. Here we highlight the careers of four of the currently active...

Sauropoda

Sauropoda is supported by more than a dozen unique features, many of which relate to the attainment of great size and weight on land (Figure 8.20). Evolution within Sauropoda has only recently been evaluated using cladistic approaches. As currently understood, sauropods consist of several primitive taxa (among them Blikanasaurus, Vulcanodon, and Kotasaurus) on the one hand, and the more derived clade Eusauropoda on the other. Eusauropods are diagnosed by many features (Figure 8.20). The most...

Weighing in

There are two commonly used ways to estimate the weight of a dinosaur. The first is based upon a relationship between limb cross-sectional area and weight. This relationship has some validity, because obviously, as a terrestrial beast becomes larger, the size (including cross-sectional area) of its limbs must increase. The question is, does it increase in the same manner for all tetrapods If so, a single equation could apply to all. It is clear, however, that it cannot. As noted by J. O....

Chains of fuels the mechanics of metabolism

We all know that somehow we get energy from the family of carbon-based molecules called carbohydrates (think candy bar ). Not quite as familiar, perhaps, is how this works. Simply put, the energy originally stored in the bonds of carbohydrates is transferred to energy stored in the bonds of molecule called ATP (adenosine triphosphate). Then, we - and all living organisms - access that energy by breaking the ATP molecule to produce a closely related molecule called ADP (adenosine diphosphate)...

The recapitation of Brontosaurus

With the discoveries of dinosaurs in the Western Interior of the USA during the late nineteenth century, box-car-loads of brand-new, but often incomplete, sauropod skeletons were shipped back east to places such as New Haven and Philadelphia. It was Yale's O. C. Marsh who described one ofthese new sauropods as Apatosaurus in 1877. With further shipments of specimens and more studies, Marsh again named a new sauropod in 1879 - Brontosaurus. Years went by and - thanks to the burgeoning popularity...

The rise and fall of Dinosauria

Willi Hennig (1913-1976) of the Deutsches Entomologisches Institut, the German entomologist who was the father of cladistic analysis (phylogenetic systematics). Figure 14.11. Willi Hennig (1913-1976) of the Deutsches Entomologisches Institut, the German entomologist who was the father of cladistic analysis (phylogenetic systematics). Ideas about the rise of dinosaurs underwent considerable rethinking during the second half of the twentieth century. But before turning to these,...

Selected readings

Dinosaur renaissance. Scientific American, 232, 58-78. Bakker, R. T. 1986. The Dinosaur Heresies. William Morrow and Company, New York, 481pp. Bakker, R. T. and Galton, P. M. 1974. Dinosaur monophyly and a new class of Vertebrates. Nature, 248, 168-172. Barrick, R. E., Stoskopf, M. K. and Showers, W. J. 1997. Oxygen isotopes in dinosaur bone. In Farlow, J. O. and Brett-Surman, M. K. (eds.), The Complete Dinosaur. Indiana University Press, Bloomington, IN, pp. 474-490. de...

Evolution of Aves

For all of its limitations, the Mesozoic record provides for us insights into the transition from primitive theropods, through eumaniraptorans, to Avialae (including Archaeopteryx), and finally to Aves. The first part of the long evolutionary sequence - the part that ran from primitive theropods to avialans - was detailed in Chapters 9 and 10. The second part, the evolution of Aves from the primitive avialan condition, represented by Archaeopteryx, through the remarkable avian discoveries...

Counting a birds fingers which is which

Recall that the carpometacarpus of living birds is a fused structure composed of three fingers. Paleontology clearly tells us which three fingers these are if Avialae is real, then the fingers must in fact be I, II, and III, since the fingers in avialan theropods, including Archaeopteryx, are I, II, and III. But because the fingers fuse into the carpometacarpus as the hand forms during a living bird's development, since the 1870s embryologists have studied the hand of modern birds as the...

To the student

Dinosaurs A Concise Natural History has been written to introduce you to dinosaurs, amazing creatures that lived millions of years before there were humans. Along with acquainting you with these magnificent beasts, reading this book will give you insights into natural history, evolution, and the ways that scientists study Earth history. What were dinosaurs like Did they travel in herds What were the horns for Did the mothers take care of their babies Was T. rex really the most fearsome...

Mr Bones

There have been dinosaur collectors there have even been extraordinary dinosaur collectors, and then, in a league quite by himself, there is the legendary Barnum Brown (Figure B14.6.1). Born in 1873, and named after the then-popular circus showman P. T. Barnum, Brown had an extraordinarily long and stunningly productive career. He virtually single-handedly turned the American Museum of Natural History (AMNH) from a place with not a dinosaur on the premises to perhaps the world's greatest...

The shape of tetrapod diversity

For more than 20 years, the University ofBristol's M. J. Benton has been compiling a comprehensive list of the fates of tetrapod families through time. We see several interesting features of the curve that results from this compilation. Note the drop in families during Middle Jurassic time (Figure B13.1.1). This, as we have seen, is an artifact that is, a specious result. This particular one comes from the lack of find localities more than from a true lack of families during the Middle...

In the beginning

Western tradition usually identifies the beginning of dinosaur paleontology as 1822, when Mary Ann Mantell, wife of English physician Gideon Mantell, found large teeth along a Sussex country lane while her husband was busily tending patients (Figure 14.1). Gideon was something of a fossil collector, and the discovery baffled him, because the teeth looked very much like those of the living herbivorous lizard Iguana, but were ominously much, much bigger (Figure 14.2). But of course the Mantells...

Ornithischia and Saurischia

In 1887, the English paleontologist Harry Seeley first recognized a fundamental division among dinosaurs. Ornithischia (ornis - bird ischia - hip) were all those dinosaurs that had a bird-like pelvis, in which at least a part of the pubis runs posteriorly, along the lower rim of the ischium (Figure 4.19). Saurischia (sauros - lizard) were those that had a pelvis more like a lizard, in which the pubis is directed anteriorly, and slightly downward (Figure 4.20). This pelvic distinction has held...

Every breath you take

For prosauropods and especially sauropods, the trachea (wind-pipe) would have been exceptionally long, approximately the same length as the arteries carrying blood from the heart to the brain. The trachea brings oxygen into contact with the alveoli in the lungs, sites where oxygen is transmitted to the blood and where carbon dioxide is passed back to the air. In animals that pass air bidirectional into and out of the lungs (that is, during inhalation and exhalation) like a bellows (mammals,...

Chew on this

One important quality of ornithischians is that, to a greater or lesser extent, all ornithischians apparently chewed their food. Because humans and many other mammals chew, it can be surprising to learn that most vertebrates don't chew that teeth are really most commonly used only for biting off chunks of whatever is being eaten. The fundamental act of chewing - of grinding food down to a paste that can be digested relatively efficiently - is, as we shall see in the following chapters, done by...

Hanging with the big boys

The many now-famous mass accumulations in the Morrison Formation in the USA (see Figure 8.13), the Tendaguru bonebeds of Tanzania (see Box 14.7), the Lower Jurassic sauropod sites of India, and most recently the Middle Jurassic of Sichuan, China, together with the vast sauropod footprint assemblages, all speak loudly to the existence of gregariousness of sauropods, including Shunosaurus, Diplodocus, and Camarasaurus. Sauropods living in large groups must have been capable of wreaking severe...

Dexterity And Grasping Ability Of The Therapods Dinosaurs

Describe the general features of theropods. 2. Describe how we know that running - cursoriality - was a key feature of theropod behavior. 3. What features of the theropod hand strongly suggest dexterity and grasping ability 4. What kinds of evidence exist for what theropods ate 5. Can a toothless animal be carnivorous 6. Describe the range of skull and tooth design in theropods. How do those relate to our understanding of how theropods bit and killed 7. What are the key clues that suggest that,...

Dinosaur endothermy the evidence

All non-avian dinosaurs had a fully erect stance. Among living vertebrates, a fully erect stance occurs only in birds and mammals, both of which are endothermic. The fully erect limb position in dinosaurs is therefore suggestive of endothermy. But is there a causal relationship between stance and endothermy The original idea was that the fine neuromuscular control necessary to maintain a fully erect stance would only be possible within the temperature-controlled environment afforded by...

Mass extinctions

Prehistoric Bivalvia

Mass extinctions involve large numbers of species and many types of species undergoing global extinction in a geologically short period of time. None of these has a truly precise definition, because there are no fixed rules for mass extinctions. Indeed, how do we know that there even were mass extinction events and how can we recognize them A compilation of invertebrate extinctions through time Figure B15.1.1 shows that, although extinctions characterize all periods it is these that are termed...

Prosauropoda

Prosauropods were once thought to be the early, primitive forebears of sauropods. Now, the group is commonly reckoned to be too specialized to have been directly ancestral to sauropods rather, they retain many of the characters of the common ancestor of prosauropods and sauropods, an unidentified animal that likely must have lived in the Late Triassic. Prosauropods are monophyletic, and thus united by a suite of diagnostic characters. Recent phylogenetic work indicates that Prosauropoda can be...

Describe Chewing As Practice By Cerateopsian Dinasaurs

What are the diagnostic characters of Marginocephalia How are marginocephalians related to other ornithischians 3. What are the diagnostic characters of Pachycephalosauria 4. What are the diagnostic characters of Ceratopsia 5. Describe chewing as practiced by ceratopsian dinosaurs. 6. What do we know about ceratopsian egg-laying and nesting 7. Give a brief history of ceratopsian biogeography. 8. What is sexual selection Intraspecific competition 9. What is in the inferred function of the...

Summary

Fossils, the buried remains of organic life, are divided into two types body and trace fossils. The body fossils include bones, shells, and other organic remains trace fossils consist of tracks, trackways, and other impressions in the form of molds and casts. Fossilization is a process that occurs after the organism dies. It consists of burial, and commonly involves a variety of types of replacement, in which the original organic and mineral material of the once-living organism is naturally...

Background extinctions

Although background extinctions are less glamorous than mass extinctions, they are essential to biotic turnover University ofTennessee paleobiologist M. L. McKinney has estimated that as much as 95 of all extinctions can be accounted for by background extinctions. Isolated species disappear from a variety of causes, including out-competition the edge , depletion of resources in a habitat, changes in climate, the growth or weathering of a mountain range, river channel migration, the eruption of...

The evolution of Ornithopoda

Cladogram of basal Ornithopoda. Derived characters include at 1, subcircular external antorbital fenestra, distal offset to apex of maxillary crowns, strongly constricted neck to the scapular blade, ossification of sternal ribs, hypaxial ossified tendons in the tail at 2, rectangular lower margin of the orbit, widening of the frontals, broadly rounded predentary, dentary with parallel dorsal and ventral margin, absence of premaxillary teeth, 10 or more cervical vertebrae, 6 or more...

Indiana Jones and the Central Asiatic Expedition of the American Museum of Natural History

He stands in the middle ofthe remote, rugged, Mongolian desert high leather riding boots, riding pants, broad-brimmed felt hat, leather-holstered sidearm hanging from a glittering ammunition belt. He carries a rifle and knows how to use it. Nobody else dresses like him, but then nobody else is the leader ofthe American Museum's Central Asiatic Expeditions to Mongolia a place which, at the time of the expeditions, the 1920s, could have been the moon . He is Roy Chapman Andrews, who 50 years...

Sauropodomorpha

Sauropodomorphs sauros - lizard pod - foot morpho - form were extremely large, not too bright, and now extinct. Isn't that what dinosaurs are all about But what about mighty and majestic These dinosaurs pushed the extremes of terrestrial body size - to the tune of 75,000 kg and possibly more Figure 8.1, p. 159 . In doing so, they taxed biomechanical and physiological design - weight support, neural circuitry, respiration, digestion, everything - to the limit. Viewed from that perspective,...

What if anything is a reptile

Temporal Opening

Organisms are commonly classified according to the biological classification system, first developed by the Swedish naturalist Carolus Linnaeus 1707-1778 . His hierarchical system is the very famous or infamous ranking of groups of organisms in groups of decreasing size kingdom, phylum, class, order, family, genus, species. Individuals are generally referred to by italicized generic genus and specific species names, for example in the case of a famous large dinosaur Tyrannosaurus rex. Any name...

Coelophysoidea Neoeratosauria and Tetanurae

At its base, Theropoda is the wellspring of the three major groups of descendants Coelophysoidea named after Coelophysis and including some related, less well-known forms , Neoceratosauria named after one of its members, the Jurassic Ceratosaurus and including some other bad boys, including the formidable Cretaceous-aged Carnotaurus and Tetanurae tetanus - stiff uro - tail . It was in Tetanurae that some of the most remarkable theropod evolution took place. Members of this group, whose record...

Marginocephalia

Marginocephalia margin - edge kephale - head . It's not a name you'll hear from the local 5-year-old dino-it-all. Yet, the name Marginocephalia reflects an important connection between two major, superficially different-looking, groups of dinosaurs Pachycephalosauria pachy - thick and Ceratopsia kera - horn ops - face . Together with Ornithopoda Chapter 7 , marginocephalians make up the taxon known as Cerapoda Figure 6.1 . Figure 6.1. Cladogram of Ornithischia, emphasizing Cerapoda and Margino...

Saurischia the big picture

Saurischia Ornithischia

What makes a saurischian a saurischian Figure III.1. Cladogram of Dinosauria, emphasizing the monophyly of Saurischia. Derived characters include at 1, fossa expanded into the anterior corner of the external naris, the development of a subnarial foramen, a concave facet on the axial intercen-trum for the atlas, elongation of the centra of anterior cervical vertebrae, hyposphene-hypantrum articulation on the dorsal vertebrae, expanded transverse processes of sacral vertebrae, loss of distal...

Making body fossils

Consider what might happen to a dinosaur - or any land-dwelling vertebrate -after it dies Figure 1.1 . Carcasses are commonly disarticulated dismembered , often by predators and then by scavengers ranging from mammals and birds to beetles. As the nose knows, most of the heavy lifting in the world of decomposition is done by bacteria that feast on rotting flesh. Some bones might be stripped clean of meat and left to bleach in the sun. Others might get carried off and gnawed....

Anatomy of Archaeopteryx

The skull of Archaeopteryx Figure 10.5a is tyically archosaurian, with nasal, antor-bital, and eye openings. Some specimens preserve a sclerotic ring, a series of plates that supported the eyeball. The temporal region is poorly known but hints of lower and upper temporal fenestrae are preserved. Archaeopteryx has blade-like, unserrated, recurved teeth. Arms and hands. The arms are quite long about 70 of the length of the legs . The hands are about as large as the feet, and each hand...

Back at the ranch

Once the fossil dinosaur bone is out of the field and back where it can be studied, the jacket must be cut open, and the fossil prepared, or freed from the matrix. This runs from simple brushing, to scraping with dental needles, to sophisticated treatments such as acid removal 2. Notice that the term dinosaur dig is a misnomer. Nobody digs into sediment to find bones bones are found because they are spotted weathering out of sedimentary rocks. Figure 1.10. Jacketing. a A fossil is found...

Chronostratigraphy

Geologists generally signify time in two ways in numbers of years before present, and by reference to blocks of time with special names. For example, we say that the Earth was formed 4.6 billion years before present, meaning that it was formed 4.6 billion years ago and is thus 4.6 billion years old. Unfortunately, determining the precise age in years of a particular rock or fossil is not always easy, or even possible. For this reason, geologists have divided time into intervals of varying...

Tetrapoda

Tetrapoda is diagnosed by the appearance of limbs with the distinctive arrangement of bones shown in Figure 4.4. So now let's take a closer look at Tetrapoda and, because we're interested in dinosaurs, we'll try to understand the part that's generally best preserved the skeleton. Figure 4.5 shows a typical tetrapod skeleton - in this case a prosauropod dinosaur - blown apart. Not surprisingly because they're monophyletic , tetrapods are all built in the same way a vertebral column is sandwiched...

Running for life

All theropods were obligate bipeds, unable to walk or run on anything but their hind legs. The body was balanced directly over the pelvis, with the vertebral column held nearly horizontally see Figure 9.5 . Evidence from the skeleton and trackways indicates that the hind legs were held close to the body, feet so close to the midline that it appears that one foot was placed ahead of the other, rather than along its side. The trackways, as well as skeletal material, also indicate that the foot...

Late Cretaceous

Antarctica South America Land Bridge

The global positions of continents during the Late Cretaceous would be almost familiar to us Figure 2.7 . North America became nearly isolated, connected only by a newly emergent land connection across the modern Bering Straits to the eastern Asiatic continent see Figure 6.31 . Although best known from the last Ice Age 100,000 years ago, this land bridge has come and gone several times since the Cretaceous. Africa and South America were fully separated, the former retaining its satellite,...

Mesozoic birds

Archaeopteryx, as we have seen, had many features that are far from the condition found in living birds, including teeth, an unfused hand, a bony tail, no synsacrum, and gastralia. How and when did the changes take place that distinguish living birds from Archaeopteryx Here our interest will be within Avialae, the clade that includes Archaeopteryx, Aves living birds , and everything in between. Within Avialae, very close to Archaeopteryx is Rahonavis from the Late Cretaceous of Madagascar....

Finding fossils

So, if the fossils are buried, how is it that we find them The answer is really in the luck of geology if fossil-bearing sedimentary rocks happen to be eroded, and a paleontologist Figure 1.5. Photograph from Shar-tsav, Gobi Desert, Mongolia, showing the tracks of a medium-sized theropod dinosaur among those of a pack of smaller theropods. Our drawing suggests one interpretation, consistent with the evidence the trackway could record a pack of Velocwaptm hunting down a single Gallimimus. Figure...

Cladograms are science

Cladograms are hypotheses concerning phylogenetic relationships. They make predictions about the distributions of characters in organisms. Any organism - living or extinct - can test an existing cladogram-based phylogenetic hypothesis. With living organisms, not only do we use their anatomy on the cladogram we can also use their genetic material. Parsimony is then used to determine which cladogram most likely approximates to the course of evolution. As will become evident, cladograms are among...

Old wives tales and feathers

Pneumatic bones and feathers are singled out as marvelous adaptations to maintain lightness and permit flight. Well, they surely maintain avian lightness, and feathers work well for flight. The question is, did pneumatic bones and feathers evolve for lightness and flight, respectively In both cases, now that we have a sense of bird ancestry, the answer is No. Hollow bones are a theropod character recall that even the name Coelurosauria contains a reference to the hollow bones in these dinosaurs...

What if anything is a bird

Cursorial Hypothesis

Clearly, the old equation feathers bird won't fly there are now many examples of feathered, non-flying dinosaurs below Avialae on the cladogram. Likewise, the equation warmblooded bird also doesn't work these feathered dinosaurs were surely warm-blooded. Should Aves - traditionally birds - be restricted to all those organisms bearing the distinctive suite of characters of living birds That would, of course, exclude Archaeopteryx, which certainly has a plausible claim on the designation bird....

Dinosaur smarts

Encephalization Quotient Dinosaurs

How can we measure the intelligence of dinosaurs 1 The short answer is Not easily. However, it is clear that, at a very crude level, there is a correlation between intelligence and brain body weight ratios. Brain body weight ratios are used because they allow the comparison of two differently sized animals that is, brain body weight ratios allow comparison of chihuahua and St Bernard dogs . The correlation suggests that, in a general way, the larger the brain body weight ratio, the smarter the...

Teeth and jaws and turds

Carnotaurus Skull Size

As with many carnivorous animals, theropod heads tended to be proportionately large. In the case of the biggest, the heads could be upward of 1.75 m in length. In general, theropod skulls are rather primitive, reminiscent of those of many non-dinosaurian ornithodirans. Yet a Struthiomimus, b Tyrannosaurus, and a Struthiomimus, b Tyrannosaurus, and there are differences tyrannosauroids had robust, deep-jawed skulls, suggesting a powerful bite. Other theropods - even large ones like...

Birds are dinosaurs

We don't mean that they are related to dinosaurs - although, if they are dinosaurs, they must be related them. We don't mean that they come from dinosaurs -although they obviously evolved from something that was itself a dinosaur. We mean that birds are dinosaurs, a statement that, as this chapter unfolds, will be no more radical than saying that humans are mammals. So how do we figure out who birds are related to The same way that we explored in Chapter 3 using diagnostic...

Paws and claws

As in modern birds, the grasping, powerful, clawed feet must have been an important part of the theropod arsenal Figure 9.9 . This character reached unparalleled sophistication in dromaeosaurids and troodontids, in which the claw on the second digit of the foot was especially huge, curved, and sharp, and capable of a very large arc of motion. During normal walking and running, it was held back or up, to protect it from abrasion or breakage. But, when needed, it could be brought forward and,...

Proposed biotic causes

a Slipped disks in the vertebral column causing dinosaur debilitation 1 Overactive pituitary glands leading to bizarre and non-adaptive growths 2 Hormonal problems leading to eggshells that were too thin, causing them to collapse in on themselves in a gooey mess c Decrease in sexual activity e A variety of diseases, including arthritis, infections, and bone fractures f Biting insects carrying diseases that did dinosaurs in over hundreds of thousands to millions of years g Epidemics leaving no...

Ornithischia the big picture

The fundamental split of Ornithischia is between the very primitive ornithischian Lesothosaurus and everything else ornithischian Figure II.5 . Lesothosaurus was a small, long-limbed Early Jurassic herbivore from South Africa Figure II.6 . It had a typical suite of diagnostic ornithischian characters including a jaw joint lower than the tooth row see Figure II.4 . That character hints at chewing but mere hints won't be necessary for the rest of Ornithischia. Figure II. 5. Cladogram of...

Fish and chips

Bird Occipital Bone

As 1978 turned to 1979, a provocative and entertaining letter and reply were published in the scientific journal Nature, discussing the relationships of three gnathostomes the salmon, the cow, and the lungfish.1 English paleontologist L. B. Halstead argued that, obviously, the two fish must be more closely related to each other than either is to a cow. After all, he argued, they're both fish A coalition ofEuropean cladists disagreed, pointing out that, in an evolutionary sense, a lungfish is...

Plants and dinosaurian herbivores

Triassic Plants Pictures

As in most extant terrestrial mammalian communities, the majority of dinosaurs were herbivorous. If dinosaurs were numerous enough, and their impact on terrestrial ecosystems was important enough, there ought to be some relationship between herbivorous dinosaur evolution and plants. Most paleobotanists - people who study extinct plants - recognize two major groupings of Mesozoic plants. The first is a non-monophyletic cluster of plants including ferns, lycopods, and sphenopsids Figure 13.8 ....

Baron Franz von Nopcsa nationalism Transylvanian dinosaurs and espionage

Robert Bakker

There was never anyone quite like him before and it is very unlikely that his kind will be seen again. Baron Franz von Nopcsa Figure B14.8.1 was one ofthe first paleontologists who saw to it that dinosaurs were interpreted in their full biological context. For this, he is generally regarded as the founder of the field of paleobiology. From him, we've learned about the unusual dinosaur fauna from Transylvania, that part of western Romania where his noble family's estate was located. This...

Archaeopteryx as a dinosaur

Higher relationships of Archaeopteryx. Archaeopteryx has an antorbital opening therefore Archaeopteryx and thus modern birds is an archosaur. In the hind foot of Archaeopteryx and living birds, three toes point forward digits II, III, and IV , and the fourth digit I is reduced the toes are symmetrical around digit III, and all toes are clawed Figure 10.5d . This condition is diagnostic of ornithodirans see Figures 4.11 and 10.7 . All living birds as well as Archaeopteryx have a fully erect...

Phylogenetic systematics enters the fray

Amid all of this intellectual ferment, yet another revolution was not-so-quietly taking place. This was the cladistic revolution see Chapter 3 . The idea was not so new although not nearly as old as that of endothermic dinosurs the basics had first been articulated by a German entymologist, Willi Hennig, in 1950 Figure 14.11 . English translations of Hennig's ideas appeared in 1966 and again in 1979. Hennig's great insight was, as we've seen in Chapter 3, to Figure 14.9. John H. Ostrom...

In the tracks of dinosaurs

Trackways, the most tangible record of locomotor behavior, provide evidence for one aspect of an animal's walking and running capabilities, and the only independent test of anatomical reconstructions. When footprints are arranged into alternating left-right-left-right patterns, they demonstrate that all dinosaurs walked with a fully erect posture. But how can trackways also give us an indication of locomotor speed We begin with stride length that is, the distance from the planting of a foot on...

Tendaguru

Tendaguru, located in the hinterland ofTanzania on the eastern coast of Africa and today monotonously formed of broad plateaus blanketed by dense torn trees and tall grass thick with tse-tse flies, was formerly the site of perhaps the greatest pale-ontological expedition ever assembled, and much - thousands of millennia - before that the place where dinosaurs came to die. Let's go back to 1907, when Tanzania was part of German East Africa. This was the era of massive western European...

Louis Dollo and the beasts of Bernissart

Louis Antoine Marie Joseph Dollo, a Belgian paleontologist with a name almost as luxuriant as his moustache, gave us our first true picture of dinosaurs, through an incredible preservation of articulated Iguanodon skeletons in Belgium Figure B14.4.1 . Born in Lille, France, in 1857, Dollo first pursued a career in civil engineering, but soon was hired by the Musee Royal d'H sto re Naturelle in Brussels, Belgium. Here he was in charge of the study and museum exhibition of these specimens. In...

The real reason the dinosaurs became extinct

Reasons Dinosaurs Became Extinct

Not every published hypothesis has been serious. In 1964, for example, E. Baldwin suggested that the dinosaurs died of constipation. His reasoning went as follows. Toward the end ofthe Cretaceous, there was a restriction in the distribution of certain plants containing natural laxative oils necessary for dinosaur regularity. As the plants became geographically restricted, those unfortunate dinosaurs living in places where the necessary plants no longer existed acquired stopped plumbing and died...

Sir Richard Owen brilliance and darkness

Richard Owen Figure B14.2.1 was the dean of natural historians in Victorian times, that iconic age of natural history. In his day, he was among the most powerful and influential scientists in England. His personality was at once brilliant, irascible, politically astute, ruthless, and condescending, and it would not be going too far to call him a liar. He was, to say the least, a man of contradictions. Owen looked the part. He was tall and gaunt with high cheekbones and, as he grew older,...

Asteroid impact

In the late 1970s, geologist Walter Alvarez and a team of co-workers Figure 15.1 were studying K T marine outcrops now exposed on land near a town called Gubbio, in Italy. They were struck by the fact that the lower half of the Gubbio outcrop is composed of a rock made up entirely of thin beds of the microscopically sized shells of Cretaceous marine organisms. The upper half of the exposure was almost exclusively of thin beds of the microscopic shells of Tertiary marine organisms. Between the...

Cladograms as tools in understanding the evolution of organisms

So how does this apply to evolution Using character hierarchies portrayed on cladograms, we establish clades or monophyletic groups2 groups that have evolutionary significance because the members of each group are more closely related - by genealogy - to each other than they are to any other creature. If a group is monophyletic, it also implies that all members of that group share a more recent common ancestor with each other than with any other organism. The cladogram in Figure 3.6 suggests...

Characters

Bear Dog Cat Cladogram

Identifying the features themselves is a prerequisite to establishing life's hierarchy, so we need to look more closely at what we mean by features. Observable features of anatomy are termed characters. Unique bones or unusual morphologies would all be characters. On the other hand, observable features would not include what something does - or how it does it. So, for example, bites hard is not a character, but perhaps big jaw muscles would be. Characters acquire their meaning not as a single...

Warmbloodedness to have and to have hot

Although endothermy is characteristic of birds and mammals, it is by no means restricted to these groups. For some time, physiologists have known of plants that can regulate heat in a variety ofways, the most common being to decouple meta bolism described in Box 12.1 from respiration, so that energy from the breakdown ofATP is simply released as heat. Several snakes are known to generate heat while brooding eggs, although this is accomplished by muscle exertion. Certain sharks and tunas can...

How to read evolution in the cladogram

We identified monophyletic groups using derived characters, and that the hierarchies of characters designate hierarchies of groups. So, looking at Figure 3.9, the distribution of shared, derived characters suggests that humans and gorillas are more closely related to each other than either is to a bear. It also suggests that all three are more closely related to each other than they are to something that does not possess the derived character of bearing fur or hair. And how does that apply to...

Thyreophora

Scutellosaurus

In life as in games, offense and defense are strategies, each with its own advantages and disadvantages. Thyreophora thyreo - shield phora - bearing or carrying literally, armor bearers went with defense, evolutionarily opting for fortress-like protection and armor. And the strategy paid off these dinosaurs did very well during their approximately 100 million years on Earth, spawning upward of 50 species. All thyreophorans are characterized by parallel rows of special bones, embedded in the...

Convergent evolution in large theropods

Looking within Tetanurae, we see a striking quality of theropod evolution. Superficially, big thero-pods all resemble each other they were once all united as carnosaurs . Clearly, as theropods evolved to large sizes, lineages independently developed some of the same features. Such similar, although independent, evolution is called convergent. In the case of large theropods, features such as proportionally large heads and a tendency toward shorter arms occurred convergently. The same features...

Cladograms

Cladograms klados - branch gramma - letter are simply branching diagrams that show hierarchies of diagnostic characters. But, as we'll see, they're not just visual aids, they're the keys to understanding who's related to whom. To understand how a cladogram works, we begin with two familiar animals say, a cat and a dog. A cladogram of a cat and a dog is shown in Figure 3.5. So we're looking for diagnostic characters for these animals. Here, we choose 2. possession of a backbone and 3. possession...

Eurypoda Ankylosauria mass and gas

Panoplosaurus Fossils

Euoplocephalus, the armored, club-tailed ankylosaur. Figure 5.15. Dorsal view of the body armor of Sauropelta. Figure 5.15. Dorsal view of the body armor of Sauropelta. back, and tail Figures 5.13, 5.14, and 5.15 . In many cases, it covered the top of the head, cheeks, and even eyelids. Under all that armor, ankylosaurs were round and very broad see Figure 5.13 clearly their girth accommodated a large gut. The head was low and broad Figure 5.16 , and equipped with simple,...

Collecting

Oryctodromeus Fossils

The romance of dinosaurs is bound up with collecting exotic and remote locales, heroic field conditions and the manly extraction of gargantuan beasts see Chapter 14 . But ultimately dinosaur collecting is a process that draws upon good planning, a strong geological background, and a bit of luck. The steps are 2. prospecting that is, hunting for fossils 3. collecting, which means getting the fossils out of whichever usually remote locale they are situated and 4. preparing and curating them that...

Wristwatches when is a watch a watch

We've used cladistic techniques to infer the history of the biota. Here we'll try something different we'll use cladistic techniques to infer the evolutionary history of watches. Analog and digital timepieces are comonly called watches. Implicit in the term watches is some kind of evolutionary relationship that these instruments have a common heritage beyond merely post-dating a sundial. But is this really so Consider three types of watch a wind-up watch, a digital watch, and a watch with a...

Dinosaurs in the Mesozoic

Mesozoic Dinosaurs

Throughout much of this book, we have considered dinosaurs as individuals who they were, what they did, and how they did it. Now we'll step back and take a look at the large-scale ebb and flow of dinosaur evolution. Before we can do that, though, we need to think about what might be missing. Table 13.1 shows the distribution of dinosaurs among the continents through time. The paucity of dinosaur remains from Australia and Antarctica, however, is surely more a question of local preservation and...

Marginocephalia Pachycephalosauria In Domes We Trust

Pachycephalosaurs

Pachycephalosaurs were bipedal ornithischians with thickened skull roofs Figure 6.2 . In the North American pachycephalosaurs, this took the form of high domes, but several Asian varieties had flattened, thickened skulls Figure 6.3 some, however, are considered to be juvenile forms of fully adult dome-headed pachycephalosaurs. Figure 6.4 shows the distinctive Northern Hemisphere distribution of pachycephalosaur sites. Figure 6.2. The flat-headed, thickheaded Homalocephale, best-known of all...

Eumaniraptora

Ornitholestes

The remainder of non-avian Theropoda, non-avian eumaniraptorans, were more closely related to birds than to the others Figure 9.32 . The group consists of those highly predaceous and intelligent carnivores, Deinonychosauria and Avialae. Deinonychosaurs rightly ought to Figure 9.30. Left lateral view of the skull and skeleton of Ornitholestes. Figure 9.30. Left lateral view of the skull and skeleton of Ornitholestes. Figure 9.31. The therizinosaur Nothronychus meets its skeleton. Figure 9.31....

Mapping the course of evolution with the cladogram

Warm-bloodedness fur- or hair-bearing Figure 3.8. A cladogram showing humans within the larger group Mammalia. Mammalia is diagnosed by warm-bloodedness and possession of fur or hair many other characters unite the group as well. Carnivora, a group of mammals that includes bears and dogs among others is shown to complete the cladogram. Carnivores all uniquely share a special tooth the carnassial and humans all uniquely share, among many other features of the skull and skeleton, a large cranium....

Dinosaurs

Dimorphodon

This climb up the cladogram leaves us wheezing and gasping for air, but at long last situated at Figure4.i2. An archosaur skull with the diagnostic antorbital fenestra. Figure 4.13. A candidate for closest relative to Dinosauria Pterosauria as represented by Dimorphodon, from the Upper Jurassic of Europe. Figure 4.13. A candidate for closest relative to Dinosauria Pterosauria as represented by Dimorphodon, from the Upper Jurassic of Europe. Figure 4.14. Cladogram of Ornithodira showing the...

The poetry of dinosaurs

Dinosaurs have been subjects of doggerel virtually since the time oftheir earliest discovery. Most have contrasted their enormity with their putative lack of brain power and, no doubt, social graces , with few recent efforts to balance such dismal views. The most famous dinosaurian poem celebrates the mental achievements of Stegosaurus, in particular the cerebral gymnastics supplied by its double brains. The piece, by Bert L. Taylor, a columnist in the 1930s and 1940s for the Chicago Tribune,...

Hierarchy

Dna Evolutionary Hierarchy

All features in the natural world are organized in a hierarchy, which can be understood to be a successive ranking of subsets within sets. A familiar hierarchy, for example, is rank within Figure 3.3. A tree of life. This particular one is a satire by Matt Groening. The image of evolution as a tree, however, is completely familiar. From the Big Book of Hell Matt Groening. All Rights Reserved. Reprinted by permission of Pantheon Books, a division of Random House, Inc., NY. Figure 3.3. A tree of...

Diapsida

Dinosauria Pterosauria

Found only in New Zealand , and birds extinct diapsids include dinosaurs as well as many other forms. Nobody really knows how many members of this clade have come and gone. Diapsida is united by a suite of shared, derived features, including having two temporal openings in the skull roof, and an upper temporal fenestra and a lower temporal fenestra. The upper and lower temporal fenestrae are thought to have provided accommodation for the bulging of contracted jaw muscles, as well as increased...

The evolution of Ceratopsia

Ceratopsian Cladogram

Cladogram of Ceratopsia, emphasizing the monophyly of Psittacosaurus and Neoceratopsia. Derived characters include at 1, rostral bone, a high external naris separated from the ventral border of the premax-illa by a flat area, enlarged premaxilla, well-developed lateral flaring of the jugal at 2, short preorbital region of the skull, very elevated naris, loss of antorbital fossa and fenestra, unossified gap in the wall of the lacrimal canal, elongate jugal and squamosal processes of...

Marginocephalia Ceratopsia horns and all the frills

Juvenile Ceratopsian

From the time of their discovery in the second half of the 1800s to the present day, there has hardly been a group of dinosaurs that has evoked more fascination than ceratopsians Figure 6.15 . Some of these quadrupedal, horned, frilled dinosaurs roamed the Great Plains of North America in the Late Cretaceous. They were rhino-like, ranging upward of 6 or 7 tonnes. Equally famous, but for other reasons, is a host of smaller, lighter 25 and 200 kg non-horned Asian ceratopsians from slightly...

Dino brains

Stegosaurus Dermal Plate

How do we know the size and shape of a dinosaur brain Casts can be obtained of the interior of the braincase. To do this, latex is painted onto the inside of a well-preserved braincase that was not crushed during fossilization. When the latex has dried and is flexible , it can be peeled off the inside ofthe braincase, and pulled through the foramen magnum big hole , the opening through which the spinal cord entered the skull in life. The result is a three-dimensional cast of the region occupied...

Eurypoda Stegosauria hot plates

Stegosaurus Tooth

Stegosaurs were medium-sized dinosaurs, 3-9 m in length and weighing 300-1,500 kg, characterized by osteoderms that developed into spines and plates, as well as by their quadrupedal stance Figure 5.3 . Their profiles sloped strongly forward and downward toward the ground as a result of the hindlimbs being substantially longer than the forelimbs Figure 5.4 . All toes had broad hooves. They seem to have been relatively uncommon dinosaurs, yet clearly had a global distribution Figure 5.5 . Figure...

Ornithopoda

Dinosaurs Cladogram Derived Character

Ornithopods ornitho - bird pod - foot were the cows, deer, bison, wild horses, antelope, and sheep of the Mesozoic Figure 7.1, see p. 133 . Magnificent herbivores all, they were one of the most numerous, diverse and longest-lived groups in all Dinosauria. From the Jurassic, when they first appeared, until the end of the Cretaceous, when they all went extinct, ornithopods evolved nearly 100 species at present count. Ornithopods spread all over the globe. They ranged from near the then-equator to...

Diagnostic features of living birds

Among living vertebrates, birds possess a remarkable and largely unique suite of diagnostic features Figure 10.1 and Table 10.1 . Feathers. All living birds have feathers - complex, distinctive structures that consist of a hollow, central shaft that decreases in diameter toward the tip. Radiating from the shaft are barbs, feather material that, when linked together along the length of the shaft by small hooks called barbules, form the sheet of feather material called the vane Figure 10.1a ....

How Does Sauropodomorpha Relate To Saurischia

What is Sauropodomorpha How does it relate to Saurischia 2. What are the diagnostic characters of Sauropodomorpha Which two groups comprise Sauropodomorpha How do they differ How are they alike 3. Outline what is known of sauropod reproductive strategies. Would you classify them as r-selected, or K-selected Why 4. Describe some features that are associated with large size in sauropodomorphs. 5. What is the evidence that sauropods didn't really chew their food How can sauropods have been...

Dinosaur wars in the nineteenth century boxer versus puncher

Othniel Charles Marsh

One ofthe strangest episodes in the history of paleontology was the extraordinarily nasty and personal rivalry between late-nineteenth-century paleontologists Edward Drinker Cope and Othniel Charles Marsh Figure B14.3.1 . In many respects, it was a boxer versus puncher confrontation the mercurial, brilliant, highly strung Cope versus the steady, plodding, beaurocratic Marsh. Their rivalry resulted in what has been called the Golden Age ofPaleontology, a time when the richness of the dinosaur...

The evolution of Thyreophora

Ankylosaur Temporal Fenestra

We can be reasonably confident that the evolution of thyreophorans embodied increasing size and a return to quadrupedality, because the cladograms show that the quadrupedal eury-podan clades were all derived relative to these primitive forms. The primitive thyreophorans suggest an evolutionary sequence from gracile, small, bipedal creatures like Scutellosaurus to larger, quadrupedal dinosaurs like Scelidosaurus see Figures II.4 and II.5 . It is not difficult to imagine the evolution of an...

The evolution of Pachycephalosauria

Pachycephalosaurs share a host of derived features, most of them cranial Figure 6.13 . Figure 6.14 maps general trends in pachycephalosaur evolution. The most primitive pachycepha-losaurs on the cladogram are Asian, suggesting an Asian origin for the group. Because all but two pachycephalosaurs are from the Late Cretaceous, we infer that they underwent considerable evolution during that time. There was an early tendency to thicken the skull roof as well as develop nerves for the sense of smell....

Hypotheses that didnt float

Maiasaura Juvenile

In the history of the study of ornithopods, habitats and anatomy conspired to put some of these animals in exotic places and give them unusual locomotor skills. For example, hadrosaurids were once regarded as amphibious, in part because the tail was long and deep great for sculling in the water , the hand ap peared webbed, and the jaws were deemed too weak to handle anything but soft aquatic vegetation. Not true in all three cases. In a similar fashion, for over 100 years, a species of...