Remarkable preservation of undigested muscle tissue within a Late Cretaceous tyrannosaurid coprolite from Alberta, Canada.

Exceptionally detailed soft tissues have been identified within the fossilized feces of a large Cretaceous tyrannosaurid. Microscopic cord-like structures in the coprolitic ground mass are visible in thin section and with scanning electron microscopy. The morphology, organization, and context of these structures indicate that they are the fossilized remains of undigested muscle tissue.

Operant behavior and the galvanic skin potential under DRL schedule.

Motor and galvanic skin potential (GSP) activity were investigated during the conditioning, extinction, and reconditioning of motor responses under a differential reinforcement of low rate (DRL) schedule of reinforcement. Interresponse time (IRT) distributions for motor responses during conditioning and reconditioning gradually stabilized at a peak just beyond the minimal IRT required for reinforcement. Few unreinforced motor responses and "bursts" of motor responses were observed during conditioning and reconditioning.