The Whetstone Mountains reach their high point of 2,350 meters (7,711 feet) on Apache Peak. The basal area is relatively high for the Sky Islands beginning firmly in semi-desert or full grasslands. Watersheds on the eastern side drain into the San Pedro River, while those on the western side feed Cienega Creek and eventually flowing into the Rillito River in the Tucson basin, which with the Santa Cruz River shortly thereafter.
The Sierra El Tigre of northeastern Sonora is a rugged Sky Island mountain range. It covers substantial terrain – its basal area spreads out over 600 square miles. Surrounded by the Rio Bavispe valley on three sides, it is somewhat isolated from neighboring high country, except from the south where it is nearly a peninsular extension from the spine of the Sierra Madre Occidental. The Sierra El Tigre is separated from the Sierra Madre by a pass of rugged hills that rise to around 1,200 to 1,600 meters (INEGI, 1998).
The Sierra Pinito are a very nice range that at its upper limit has pure pine forest consisting of Arizona pine (Pinus arizonica). As with many Sky Islands logging took most old growth pine in the 40's and 50's, but in the late 2000's recovery is progressing
Interestingly there are dense forests of willow-leaf oak (Quercus viminea) in the higher oak woodland and lower pine-oak zone. This is near the northward distribution for the species, but this does not seem be poor quality habitat.
The Tumacacori Highlands are an extended area of high country and rolling hills. Two primary named mountains make up most of the highlands - the Atascosa Mountains and the Pajarito Mountains. This area connects to another oak woodland zone in Sonora compoed of the Sierra Cíbuta, Sierra Guacomea, Sierra Las Avispas, and Sierra Esmeralda.
The Sierra Aconchi is remote and little visited range that reaches elevations that support very small, limited stands of pure pine. Most of the range is oak woodland, with some pine/oak at higher elevations. Interesting species to note are apache pine (Pinus engelmannii), Chihuahua pine (Pinus leiophylla var. chihuahuana), Arizona pine (Pinus arizonica), Quercus coccolobifolia, and Texas madrone (Arbutus xalapensis).
The Sierra Mazatán (also known as the Sierra Huerfana by locals) are at the southern edge of the Sky Island in the region. The range is on Sonora's coastal plain and the nearest high country to Hermosillo. It is dominated by thorn-scrub on slopes and oak woodland at higher elevations.
Phrynosoma ditmarsi, rock horned lizard in the Sierra Murrieta, eastern Sonora. Lizard found in oak woodland on a steep, fairly dense, and mesic slope.