What if anything is a reptile
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...
Selected readings Yyb
Barsbold, R. and Osmolska, H. 1990a. Ornithomimosauria. In Weishampel, D. B., Dodson, P. and Osmolska, H. eds. , The Dinosauria, 2nd edn. University of California Press, Berkeley, pp. 225-244. Barsbold, R. and Osmolska, H. 1990b. Oviraptorosauria. In Weishampel, D. B., Dodson, P. and Osmolska, H. eds. , The Dinosauria, 2nd edn. University of California Press, Berkeley, pp.249-258. Clark, J. M., Maryaiiska, T. and Barsbold, R. 2004, Therizinosauroidea. In Weishampel, D. B., Dodson, P. and...
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
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
Before burial. 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
Skull. 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...
Sauropoda
Getting really big takes some serious evolution, and sauropods were really big dinosaurs. Yet, the sophisticated sauropod design, once it appeared, remained unique and little changed during their 140 million years on Earth Figure 8.8 . The skull itself was distinctive the tooth row was not inset, as one sees in mammalian and ornithischian herbivores. The teeth, depending upon the sauropod, had simple crowns Figure 8.9. Dorsal view of the skull of a Brachiosaurus and b Diplodocus. Note the...
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
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....
Selected readings Gpp
Butler, R. J., Smith, R. H. M. and Norman, D. B. 2007. A primitive ornithischian from the Late Triassic of South Africa and the early evolution and diversification of Ornithischia. Proceedings of the Royal Society Series B, 274, 2041-2046. Butler, R. J., Upchurch, P. and Norman, D. B. 2008. The phylogeny of the ornithischian dinosaurs. Journal of Systematic Palaeontology, 6, 1-40. Hopson, J. A. 1975. The evolution of cranial display structures in hadrosauridian dinosaurs. Paleobiology, 1,...
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
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
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
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
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,...
IProposed 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
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
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
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...
Prosauropoda
Prosauropods are a group of relatively primitive dinosaurs with small heads, long necks, large bodies, and long tails, known from the Late Triassic through early Jurassic, from all continents except Australia see Figure 8.2 . In general, the front limbs were somewhat shorter than the hindlimbs, and all had five digits. Prosauropod hands were equipped with a large, half-moon-shaped thumb claw Figure 8.5 . Whether for food procurement, defense, or some unspecified social activity, the function of...
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...
Stance its both who you are and what you do
Tetrapods that are most highly adapted for land locomotion tend to have an erect stance. This clearly maximizes the efficiency ofthe animal's movements on land, and it is not surprising that, for example, all mammals are characterized by an erect stance. Tetrapods such as salamanders which are adapted for aquatic life display a sprawling stance, in which the legs splay out from the body nearly horizontally. The sprawling stance seems to have been inherited from the original position ofthe limbs...
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
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
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...
Selected readings Kch
Butler, R. J., Upchurch, P. and Norman, D. B. 2008. The phylogeny of the ornithischian dinosaurs. Journal of Systematic Paleontology, 6, 1-40. Norman, D. B., Witmer, L. M. and Weishampel, D. B. 2004. Basal Ornithischia. In Weishampel, D. B. and Dodson, P. eds. , The Dinosauria, 2nd edn. University of California Press, Berkeley, pp. 325-334. Sereno, P. C. 1986. Phylogeny of the bird-hipped dinosaurs Order Ornithischia . National Geographical Research, 2, 234-256. Introduce Thyreophora,...
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
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 1
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
Figure 5.13. 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,...
Topic questions Lzs
1. Define Chordata, notochord, gnathostome, Sarcopterygii, skull, mandible, girdles, neural arch, centrum, process, ilium, ischium, pubis, acetabulum, sternum, humerus, femur, radius, ulna, tibia, fibula, phatanges, ungual, metacarpals, metatarsals, metapodials, occipital condyle, foramen magnum, stapes, skull roof, tympanic membrane, nares, orbit, palate, amniote, anamniote, amnion, anapsid, synapsid, diapsid, upper temporal fenestra, lower temporal fenestra, archosaur, Archosauromorpha,...
Collecting
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...