Hi Mickey,
It's been a while without a definitive answer from a native speaker, so I'll risk giving my two cents: My Russian is far from perfect, but I majored in it in undergrad and have published some literary translations. "Джиракудукский" ("of Dzhirakuduk") refers to a fossil site in Uchquduq District, central Uzbekistan, not to Jalaquduq District in far eastern Uzbekistan. Sues and Averianov (2016) note a bunch of variant spellings: "The most fossiliferous strata are those of the Bissekty Formation, which crop out along an approximately 8 km long escarpment near the small settlement of Dzharakuduk (variously given in the literature as Dzhara-Kuduk, Dzhirakuduk, Dzhyrakuduk, Bissekty, and Kul'beke) in the central Kyzylkum Desert."
To my eye, "Джиракудукский" ("of Dzhirakuduk") and "пока не описанный" ("yet undescribed") are both just adjectives describing "вид" ("species") - the line could be translated as "The undescribed species of Dzharakuduk sauropod or segnosaur had paradoxically heavy skeletal pneumatization."
Hope this helps - and I'll be happy to be corrected if anyone knows better!
Sues, Hans-Dieter, & Averianov, Alexander (2016). "Therizinosauroidea (Dinosauria: Theropoda) from the Upper Cretaceous of Uzbekistan,"
Cretaceous Research, 59, 155-78.