Paleo Lab 10 - Reptiles and Birds

Paleo Lab 10 - Reptiles and Birds - PALEO LABORATORY 10...

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PALEO LABORATORY # 10, PAGE 1 PALEO LAB # X – REPTILES, SYNAPSIDS AND BIRDS CLASS REPTILIA The oldest-known reptiles are found in Lower Carboniferous (Mississipian)-age deposits from Scotland and from the Mid-Carboniferous (Pennsylvanian) of Nova Scotia. These "stem reptiles" possessed labyrinthine infolding in their teeth and assumed the sprawled posture of their labyrinthodont amphibian (Seymouriamorph) ancestors. However, even the earliest reptiles showed vast improvements over the Amphibia in their adaptation to land-dwelling through the evolution of internal fertilization and development of the amniotic egg. This type of egg could be laid on land and through its development the reptiles freed themselves from dependence on the aquatic environment. A couple of groups of these “stem reptiles”, the captorhinids and palaeothyrids, are evidently close to the ancestry of the later “diapsid” reptiles. By middle Mesozoic times, reptiles completely dominated terrestrial environments and other members of the group reinvaded the oceans and developed powers of flight. Reptile evolution involves a number of distinct fossil and modern groups. The classification of the reptiles into major categories is primarily based on the position and numbers of temporal openings on the sides of the skull. The anapsids, which include the turtles and primitive reptile groups such as the procolophonids, pareiasaurs and captorhinids, lack temporal openings. Diapsids, including dinosaurs, the ancient flying pterosaurs and all modern reptiles (except turtles) primitively have two temporal openings. The euryapsids, including the ancient swimming plesiosaurs and ichthyosaurs, had a single upper temporal opening. The synapsids, including the fin-backed pelycosaurs and “mammal-like reptiles” (therapsids), had a single lower temporal opening. Although they have been placed within the reptiles in previous classifications, the synapsids are now considered to belong to a distinct class of vertebrates. EXERCISE # 1 - Observe the skull illustrations provided and the lab specimens of amphibians, primitive reptiles, and advanced archosauromorphs. Describe the changes seen within this "structural lineage" of skulls in terms of bones lost, bones reduced, and subsequent changes in skull proportions. EXERCISE # 2 - Using the illustrations provided, identify the types of reptile temporal openings in specimens TSU VP 051, VP 071, VP 157, VP 163 and VP 229. EXERCISE # 3 - Observe the skull of the captorhinid Labidosaurus (TSU VP 069; on Shelf E4) from the Lower Permian Arroyo Formation of Baylor County, Texas. A. What feature of the skull makes this specimen an anapsid? B. What is the evolutionary relationships of the captorhinids versus other reptile groups, both ancient and modern? The Pareisaurs were large anapsid herbivores from the Middle to Upper Permian of
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Paleo Lab 10 - Reptiles and Birds - PALEO LABORATORY 10...

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