HORSE EVOLUTION – In-lab Worksheet Remember to be careful with the fossils. Be patient if you have to wait for other teams to look at a particular fossil. Part 1: Qualitative observations. Your TA will assign a specific trait for your group to concentrate on as you make your observations. Teams will circulate the room to make qualitative observations of the fossils. For this portion of the lab you just need to concentrate on general characteristics, you will not be taking any measurements. Thinking about differences in lifestyle (e.g. running speed vs. maneuverability, browsing vs. grazing diets) and make comparative observations on the fossils. Consider things like: - Relative size vs. absolute size. - The size and shape of the head and lower jaw; - The total number of teeth, different tooth types, and occlusal surfaces of the teeth; - The construction of the limbs (i.e. consider the number of joints in the length of the leg, or number of toes touching the ground). - Relative vs absolute size (think about the proportion of the different parts of the fossils). Place your observations in the attached chart (Table 1) and use this information to identify the major evolutionary trends in the horse lineage. This qualitative observations serve as a hypothesis that can be tested with the quantitative data you will collect during this lab. Moreover, these evolutionary changes can be connected to changes in the habitat or diet of these equine species. 1. From the observations recorded in the table, make a hypothesis about how changes in environment select for changes in traits related to feeding or locomotion, in particular skull, teeth, or leg skeletal features. ____________________________________________________________________________________________________________________________________________________________ 2. How would you test that hypothesis? Briefly describe what measurements you would take on the fossils: __________________________________________________________________________________________________________________________________________________________________________________________________________________________________________Table 1. Chart for recording qualitative observations of horse fossil specimens Species Skull Characters Dental Characters Limb Characters Hyracotherium Mesohippus Merychippus Early Equus Equus ________________________ Part 2: Quantitative Measurements You will calipers to take measurements on limb, teeth or skull characters (Your TA will assign a specific trait for your group to concentrate on). There are laminated pages with instructions for each measurement. Use the attached tables (Tables 2-4) to fill in your data and enter your group’s data on the Smartboard computer. Collect data for other traits from the class charts. 1. Describe how the locomotion of horses probably changed in relation to changes in limb morphology 2. Briefly describe how skull characters have changed over the five horse series. 3. Summarize how the size and shape of the premolars changed over the five horse series. 4. Summarize how the types of dental material exposed at the occlusal surface and the topography of enamel ridges changed over the five horse series. How does this reflect chewing mode (up and down vs side to side) and efficiency?Table 2. Charts for recording Limb measurements. Species (1) Central metatarsal Length (2) Central metatarsal Width (CMW) (3) CMW/CML (4a) Number of toes Hyracotherium Mesohippus Merychippus Early Equus Equus . Species (4b) Which Toes Touch the Ground? (4c) Hoof Development on Any Toes? (5a) Outer Metatarsal Length (OML) (5b) OML/CML Hyracotherium Mesohippus Merychippus Early Equus EquusTable 3. Charts for recording Skull Measurements Species (1a) Skull Length (1b) Skull Length/CML (2a) Rostrum Length (2b) Rostrum Length/Skull Length Hyracotherium Mesohippus Merychippus Early Equus Equus Species (3a) Length of Masseter (3b) Length of Masseter/CML (4) Mandible Depth (From group A) Central Metatarsal Length (CML) Hyracotherium Mesohippus Merychippus Early Equus EquusTable 4. Charts for recording Jaw and Tooth Measurements Species From Group B Mandible Depth (1a) Crown Height (1b) Tooth Height (mandible depth + Crown height) Tooth Length (TL) Hyracotherium Mesohippus Merychippus Early Equus Equus Species (2) Number of Cheek Teeth (3) Relative Size/Shape of Premolars to Molars (4a) Types of Dental Material Exposed (1d) Hypsodonty Index (1b/1c) Hyracotherium Mesohippus Merychippus Early Equus