Evidence for Avian Intrathoracic Air Sacs in a New Predatory Dinosaur from Argentina

Background: Living birds possess a unique heterogeneous pulmonary system composed of a rigid, dorsally-anchored lung and several compliant air sacs that operate as bellows, driving inspired air through the lung. Evidence from the fossil record for the origin and evolution of this system is extremely limited, because lungs do not fossilize and because the bellow-like air sacs in living birds only rarely penetrate (pneumatize) skeletal bone and thus leave a record of their presence. Methodology/Principal Findings: We describe a new predatory dinosaur from Upper Cretaceous rocks in Argentina, Aerosteon riocoloradensis gen. et sp. nov., that exhibits extreme pneumatization of skeletal bone, including pneumatic hollowing of the furcula and ilium. In living birds, these two bones are pneumatized by diverticulae of air sacs (clavicular, abdominal) that are involved in pulmonary ventilation. We also describe several pneumatized gastralia (‘‘stomach ribs’’), which suggest that diverticulae of the air sac system were present in surface tissues of the thorax. Conclusions/Significance: We present a four-phase model for the evolution of avian air sacs and costosternal-driven lung ventilation based on the known fossil record of theropod dinosaurs and osteological correlates in extant birds: (1) Phase I—Elaboration of paraxial cervical air sacs in basal theropods no later than the earliest Late Triassic. (2) Phase II—Differentiation of avian ventilatory air sacs, including both cranial (clavicular air sac) and caudal (abdominal air sac) divisions, in basal tetanurans during the Jurassic. A heterogeneous respiratory tract wit

Diseases and Mortalities of Fishes and Other Animals In the Gulf of Mexico

Most mortality results from natural causes including red tide which is primarily restricted to West Florida and cold-kills that have greater influence in the warmer regions of South Texas and South Florida, but also kill a significant amount of fish and other animals in the northern Gulf. With the exception of red tide and other harmful algal blooms, the health of the Gulf has not been systematically studied. Mexico has only recently started to evaluate the health of its coastlines. Mortalities of marine animals, particularly fishes, in the Gulf caused by natural and anthropogenic events seem to interact with infectious disease agents and noninfectious diseases, but the mortalities are often attributed to the disease agents alone. “Events” that cause mortalities include eutrophication; hypoxia; algal blooms; temperature, salinity, and weather extremes; and chemical and sediment pollution. “Diseases” include those caused by infectious agents, parasites, neoplasms, and developmental abnormalities. Interactions of the effects of diseases and stressful events are considered important but little investigated