[D] Levnesovia transoxiana [sG] [T]
Sues & Averianov 2009
Cretaceous Late Turonian
Ornithischia Ornithopoda Hadrosauridae
Bissekt Formation (Bissekty Formation), Dzharakuduk, Navoi Viloyat (district), central Kyzylkum Desert, Uzbekistan
Levnesovia transoxiana is the oldest well-documented taxon referable to Hadrosauroidea sensu Godefroit et al. It differs from a somewhat younger and closely related Bactrosaurus from Inner Mongolia (China) by a tall sagittal crest on the parietals and the absence of club-shaped dorsal neural spines in adult specimens. Levnesovia, Bactrosaurus and possibly Gilmoreosaurus represent the earliest radiation of Hadrosauroidea, which took place during the Cenomanian–Turonian and possibly in North America. The second, Santonian-age radiation of Hadrosauroidea included Aralosaurus, Hadrosauridae and lineages leading to Tanius (Campanian) and Telmatosaurus (Maastrichtian). Hadrosauridae appears to be monophyletic, but Hadrosaurinae and Lambeosaurinae originated in North America and Asia, respectively.
The newtaxon is named forLevNessov (1947–1995), using the most accurate English-language spelling of his surname as transliterated from the Cyrillic, and Transoxiana, an ancient name of the lands beyond (trans) the Amu Darya River (Oxus), corresponding to present-day Uzbekistan.
USNM 538191, postorbital region of skull roof with nearly complete braincase
ZIN PH 1306/16, subadult skull roof fragment; ZIN PH 1307/16, adult skull roof fragment; USNM538126, partial braincase and skull roof; CCMGE 565/12457, 566/12457 and ZIN PH 306/16, almost complete adult braincases; USNM 538121, subadult braincase; many isolated cranial and postcranial bones in the collections of: the National Museum of Natural History, Smithsonian Institution, Washington,DC(USNM); Chernyshev’s CentralMuseum of Geological Exploration, Saint Petersburg (CCMGE); the Zoological Institute, Russian Academy of Sciences, Saint
Petersburg (ZINPH); and the Institute ofZoology,National Academy of Sciences of Uzbekistan, Tashkent (IZANUZ). All referred specimens come from the same locality and horizon (Bissekty Formation at Dzharakuduk). The additional braincases and skull roof fragments are morphologically indistinguishable from the holotype, and the remaining skeletal elements are documented, in most cases, by numerous specimens that show no taxonomically significant variation and thus are referred to a single taxon.
Locality and horizon
Dzharakuduk, Navoi Viloyat (district), central Kyzylkum Desert, Uzbekistan. Bissekty Formation; Late Cretaceous (Middle–Late Turonian).
A basal hadrosauroid iguanodontian that differs from known non-hadrosauroid iguanodontians in the following features: ectopterygoid–jugal contact absent; predentary gracile and shovel-shaped, with gently rounded anterior margin; surangular foramen absent; and dentary tooth crowns with one primary ridge and faint (if any) secondary ridges. Differs from Bactrosaurus (Gilmore 1933) in presence of tall sagittal crest on parietals, absence of lacrimal process on prefrontal, and absence of clubshaped neural spines on dorsal vertebrae in adults. Differs from Gilmoreosaurus (Brett-Surman 1979) by shorter contribution of frontal to orbital rim, longer diastema between first dentary tooth and predentary (equivalent to more than one-fifth of tooth row length), and nearly vertical coronoid process of dentary. Differs from more derived Hadrosauroidea in absence of well-developed continuous ectopterygoid ridge on maxilla; dentary tooth row and posterior end of dentary terminating at apex of coronoid process; and dentary tooth row bowed lingually in occlusal view.