The Khwaresmian language
 
Group Iranian (with Persian, Kurdish etc.), East Iranian (with Sogdian, Ossetic, Pashto etc.)
Geography & History The area where Khwaresmian was spoken lies by the lower Amudarya, in the oasis called Khwaresm. The oldest documents date from the 3rd century BC; a century later, it began flourishing as the language of the kingdom with the same name. Khwaresmian words and phrases are mentioned in Arabic sources of Central Asia until the 14th century. Apparently by the 16th century Khwaresmian became extinct replaced in colloquial speech by Turkish tongues, in written - by Arabic.
Phonetics The language had five pairs of vowels, long and short, but long o did not have its short analogue, becoming a "schwa" [@]. Five nasal vowels were used. The system of consonants included two sets of affricates, faryngal h; the sound [n] was unstable after a vowel. Some consonants became very dissimilar to those existing in the Common Iranian language (*d > dj, *rs > š, *-f- > -š-)
Morphology The morphological structure combined both new analytic and ancient synthetic forms. Three inflected noun cases, two genders, two numbers, the definite article. Personal pronouns used a number of suppletive forms (i.e. formed by different roots). Verbs used -r- in the 3rd person plural (the feature which unified Khwaresmian with Avestan and Sacian); the past tense was formed from the present stem of the verb. Khwaresmian had a peculiar trait of syntax which cannot be found in any other Iranian language: the wide usage of pronominal and adverbial suffixes which were shaping the verb (e.g. cáy-ta-hi-wa-ber - "he came there before him", literally "he came him there above"). 
Writing Aramaic based alphabet (until the 1st century AD), Arabic based alphabet
Close Contacts Turkish languages of Central Asia
Sample  
Picture Shahrisabz, Uzbekistan
More info