IEEE 802.11 DCF is the MAC protocol currently used in wireless LANs. However, due to idle and collision times, 802.11 DCF performs poorly when it comes to channel utilization, system throughput, and channel access time. To overcome these sources of inefficiency in 802.11 DCF, in this paper, we propose a distributed and dynamically adaptive MAC protocol for wireless networks, called Token-DCF. Main focus of our approach is on reducing idle and collision times by introducing an implicit token passing algorithm. In Token-DCF, a transmitting station schedules one of its neighboring stations for the next transmission epoch using a distributed opportunistic algorithm. Furthermore, packet overhearing is employed to exchange scheduling information across the network. Our simulation results show that Token-DCF achieves more than 2X improvement in system throughput and channel access delay compared to 802.11 DCF for most network configurations.