SALT GLANDS IDENTIFIED IN A LATE CRETACEOUS POLYCOTYLID

MARTIN, Y & M. FERNÁNDEZ

Bristol, Inglaterra

Congreso; 69 th Anual Meeting Society of Vertebrate Paleontology; 2009

In 2007, a new polycotylid plesiosaur, Pahasapasaurus haasi, from western South Dakota was described. The specimen is housed in the Adams Museum, Deadwood (AMM 98.1.1), and was derived from the early late Cenomanian Orman Lake Member at the base of the Greenhorn Limestone north of the Black Hills in Butte County. The holotype is represented by a relatively complete cranium, which is broken away in antorbital area, revealing paired natural casts of lobulated structures preserved in concretionary ferruginous marl. These structures are clearly separated from the exposed infilling of the nasal capsule and must have been covered in the living marine reptile dorsally by extensions of the maxillae, the premaxillae, and probably the anterior frontals. The position and lobate structures resemble salt glands of other extant marine reptiles like the iguana Amblyrhynchus and do not resemble normal sedimentological structures. Reptiles that have reinvaded the marine habitat require a means to remove the excess of salt to prevent lethal osmotic dehydration. Such salt glands in plesiosaurs had been expected, but this specimen possesses the first actual evidence for these structures.Pahasapasaurus haasi, from western South Dakota was described. The specimen is housed in the Adams Museum, Deadwood (AMM 98.1.1), and was derived from the early late Cenomanian Orman Lake Member at the base of the Greenhorn Limestone north of the Black Hills in Butte County. The holotype is represented by a relatively complete cranium, which is broken away in antorbital area, revealing paired natural casts of lobulated structures preserved in concretionary ferruginous marl. These structures are clearly separated from the exposed infilling of the nasal capsule and must have been covered in the living marine reptile dorsally by extensions of the maxillae, the premaxillae, and probably the anterior frontals. The position and lobate structures resemble salt glands of other extant marine reptiles like the iguana Amblyrhynchus and do not resemble normal sedimentological structures. Reptiles that have reinvaded the marine habitat require a means to remove the excess of salt to prevent lethal osmotic dehydration. Such salt glands in plesiosaurs had been expected, but this specimen possesses the first actual evidence for these structures.Amblyrhynchus and do not resemble normal sedimentological structures. Reptiles that have reinvaded the marine habitat require a means to remove the excess of salt to prevent lethal osmotic dehydration. Such salt glands in plesiosaurs had been expected, but this specimen possesses the first actual evidence for these structures.