Name: GEOL 104 Dinosaurs: A Natural History Anatomy, Taxonomy, Evolution & Systematics Assignment DUE: Mon. October 1 Part I. Comparative Anatomy Below is the skull of the early primitive meat-eating dinosaur Herrerasaurus ischigualastensis. Herrerasaurus ischigualastensis For 1-7: Using the handout from class and the website, label the bones indicated on the skull above by the thin arrows. There are 7 bones to label. Write the name of the bone at the end of the thin arrow. For 8-11, you will identify the four openings in the skull indicated by the thick bold arrows. Use the information below to recognize the different openings: • Antorbital fenestra: anterior to the orbit, posterior to the naris, surrounded by the maxilla, lacrimal, and nasal bones • Infratemporal fenestra: posterior to the orbit, ventral to the supratemporal fenestra, surrounded by the jugal, quadratojugal, squamosal, and postorbital bones • Mandibular fenestra: within the mandible (lower jaw), surrounded on the anterior end by the dentary and the posterior end by the surangular and angular bones • Supratemporal fenestra: posterior to the orbit, dorsal to the infratemporal fenestra, surrounded by the squamosal, postorbital, frontal, and parietal bones 1Name: Gorgosaurus libratus (juvenile) In the skeleton above, identify by name or number the following bones (the handouts will help with this): 12) A Cervical (neck) Vertebra 13) A Dorsal (back) Vertebra 14) A Caudal (tail) vertebra 15) A Rib 16) A Gastralium 17) Scapula 18) Ilium 19) Ischium 20) Pubis 21) Humerus 22) Femur 23) Tibia 24) Fibula 25) Manus (the hand) Extra Credit) This dinosaur is in [ dorsal | right lateral | left lateral | left medial ] view. Part II. Taxonomy 26) Euoplocephalus tutus was named in 1910; Scolosaurus cutleri was named in 1928. If later studies indicate that these are two different species within the same genus, what would be the name of each of these two species? 27) If, instead, Euoplocephalus tutus and Scolosaurus cutleri are discovered to be different specimens of the same species, what would be the complete name of this single species? Extra Credit) What is the ONLY proper abbreviation of Tyrannosaurus rex? 2Name: Part III. Evolutionary Patterns Evolutionary biologists, including paleontologists, have observed a number of different patterns that occur throughout the history of life. Some of the major ones are: • Divergence: From a single common ancestral population, two or more different descendant lineages each evolve their own different specializations over time. Thus, while early members of each lineage were similar (having changed little from their common ancestor), the later descendants get more and more different. • Convergence: Sometimes different lineages of organisms evolve similar traits, appearances, and behaviors independently, as the ancestors of each “hit upon” (that is, are selected for) the same or similar evolutionary solutions to problems. This is very common when the adaptations have to do with mechanical processes (feeding, locomotion, etc.), but can occur in other situations as well. The basic pattern is that the ancestors were different from each other, but the descendants become more and more similar. • Sexual Selection: Since evolutionary fitness is simply whose genes are represented the most in the next generation, than traits that lead to more successful mating (i.e., that are “attractive”) will tend to be favored. • Correlated Progression: As a lineage evolves traits for a particular way of life, new traits that continue to enhance that form of existence and work well together will be selected for, and those traits that counter that adaptive trend will be selected against. • Adaptive Radiation: When an ancestor arrives in a previously uncolonized region, or has its competitors wiped out, or evolves an adaptation that allows it to live in an entirely new way, than many divergent lineages from that common ancestor are likely to survive. Therefore, in a geologically very short period of time, many different descendants radiate from a single ancestral population. • Niche Partitioning: When species with similar habits live in the same region, those variants that do not have quite the same habits as other species will tend to do better, while the other variants (who are in greater competition with other species) will do worse. So over time, each species will “split up” their resource base: in other words, evolve features for particular sub-habits within the larger ecological niche. • Living Fossils: Evolutionary change does happen at the same pace for all lineages. Some groups of organisms do very well in some specific niche, and so are unchanged for vast periods of geologic time. • Exaptation: Evolution does not always work by developing entirely new structures or behaviors. Instead, it is far more common for a structure of behavior that was adapted (“fit for”) to some other context to be exapted (“fit from” or “fit out of”) to a new function. • Heterochrony: Evolutionary change can also occur by changing the timing of development of the organism. This could either be by retaining the juvenile traits of the ancestor into adulthood (paedomorphosis) or by evolving extremes beyond the adult stage of the ancestor (peramorphosis). For this section, identify which of the above evolutionary phenomena/patterns best describes each of the scenarios given: 3Name: 28) Below are a set of high-spined fossil animals, and beneath each is the ancestral condition from which they evolved. By comparison the ancestors (below) to each other, and the descendants (on top) to each other, the evolution of high neural spines is an example of what evolutionary pattern? 29) The sails in each of the cases above are formed by a simple elongation (stretching out) of the neural spines, a structure already present in the vertebrae of ancestors. In the ancestors the neural spine serves as an anchor for back muscles, but the sail may have been used for display and/or to help regulate body temperature. In any given example, this change in function is an example of which evolutionary pattern? 30) The skulls of baby prosauropods was very short, while the adult skulls had big snouts. The sauropods (descendants of prosauropods) had short snouts even as adults. This is an example of which evolutionary pattern?