Laying to rest an unusual and confusing member of the cougar family, the FWS has officially declared the eastern cougar extinct .
Although the eastern cougar has been on the endangered species list since 1973, its existence has long been questioned. The U.S. Fish and Wildlife Service (Service) conducted a formal review of the available information and, in a report issued today, concludes the eastern cougar is extinct and recommends the subspecies be removed from the endangered species list.
Genetic testing in the last decade has shown that there was not much if any difference between eastern and western cougars. Even when setting a formal recovery plan in 1981, wildlife biologist were uncertain about how an eastern cougar would differ from a western cougar. For instance, the recovery plan is available here  and on page 8 the author states:
The lack of reference specimens from a substantial portion of T.C. couguar's range could cause some taxonomic confusion as to the subspecific identity of any cougar found within the accepted range of F.C. couguar. It is uncertain how animals from the southern and western portions of the eastern cougar's range would differ morphologically from those of the northeast. ... The proper subspecific identification of any cougar found in the east may be difficult.