A peer-reviewed open-access journal ZooKeys 483:The 59–80 paleoenvironments (2015) of azhdarchid pterosaurs localities in the Late Cretaceous... 59 doi: 10.3897/zookeys.483.9058 RESEARCH ARTICLE http://zookeys.pensoft.net Launched to accelerate biodiversity research The paleoenvironments of azhdarchid pterosaurs localities in the Late Cretaceous of Kazakhstan Alexander Averianov1,2, Gareth Dyke3,4, Igor Danilov5, Pavel Skutschas6 1 Zoological Institute of the Russian Academy of Sciences, Universitetskaya nab. 1, 199034 Saint Petersburg, Russia 2 Department of Sedimentary Geology, Geological Faculty, Saint Petersburg State University, 16 liniya VO 29, 199178 Saint Petersburg, Russia 3 Ocean and Earth Science, National Oceanography Centre, Sou- thampton, University of Southampton, Southampton SO14 3ZH, UK 4 MTA-DE Lendület Behavioural Ecology Research Group, Department of Evolutionary Zoology and Human Biology, University of Debrecen, 4032 Debrecen, Egyetem tér 1, Hungary 5 Zoological Institute of the Russian Academy of Sciences, Universi- tetskaya nab. 1, 199034 Saint Petersburg, Russia 6 Department of Vertebrate Zoology, Biological Faculty, Saint Petersburg State University, Universitetskaya nab. 7/9, 199034 Saint Petersburg, Russia Corresponding author: Alexander Averianov ([email protected]) Academic editor: Hans-Dieter Sues | Received 3 December 2014 | Accepted 30 January 2015 | Published 20 February 2015 http://zoobank.org/C4AC8D70-1BC3-4928-8ABA-DD6B51DABA29 Citation: Averianov A, Dyke G, Danilov I, Skutschas P (2015) The paleoenvironments of azhdarchid pterosaurs localities in the Late Cretaceous of Kazakhstan. ZooKeys 483: 59–80. doi: 10.3897/zookeys.483.9058 Abstract Five pterosaur localities are currently known from the Late Cretaceous in the northeastern Aral Sea region of Kazakhstan. Of these, one is Turonian-Coniacian in age, the Zhirkindek Formation (Tyulkili), and four are Santonian in age, all from the early Campanian Bostobe Formation (Baibishe, Akkurgan, Buroinak, and Shakh Shakh). All so far collected and identifiable Late Cretaceous pterosaur bones from Kazakhstan likely belong to Azhdarchidae: Azhdarcho sp. (Tyulkili); Aralazhdarcho bostobensis (Shakh Shakh); and Samrukia nessovi (Akkurgan). These latter two taxa, both from the Bostobe Formation might be syno- nyms. Azhdarcho sp. from the Zhirkindek Formation lived in a tropical-to-subtropical relatively humid climate on the shore of an estuarine basin connected to the Turgai Sea. Known fossils were collected in association with brackish-water bivalves and so the overall paleoenvironment of this pterosaur was likely an estuarine marsh as indicated by the dominance of conifers and low relative counts of ferns and an- giosperms. Aralazhdarcho bostobensis, from the Bostobe Formation, lived on a coastal fluvial plain along the Turgai Sea. This paleoenvironment was either floodplain (Akkurgan, Buroinak, and Shakh Shakh) or Copyright Alexander Averianov et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 60 Alexander Averianov et al. / ZooKeys 483: 59–80 (2015) estuarine (Baibishe). In the Santonian – early Campanian, shallow waters near this coastal plain were sites for the intensive accumulation of phosphates under upwelling conditions caused by strong winds from the ancient Asian landmass. These winds also caused significant aridization of the climate during this time. We speculate that pterosaurs may have been attracted to this area by the abundant resources in the bio- productive estuaries and nearshore upwelling waters. Keywords Pterosauria, Azhdarchidae, Late Cretaceous, Kazakhstan, distribution, paleoenvironments Introduction In Kazakhstan two regions are known to have yielded the skeletal remains of ptero- saurs: 1) the Upper Jurassic (Oxfordian-Kimmeridgian) Karabastau Formation in the Karatau Mountains of southern Kazakhstan, and; 2) several sites within the Late Cre- taceous Zhirkindek (Turonian-Coniacian) and Bostobe (Santonian – lower Campa- nian) formations in the northeastern Aral Sea region of western Kazakhstan (Fig. 1). Of these, the latter has yielded isolated bones of large pterodactyloid pterosaurs while the former is a Konservat-Lagerstätte known to contain exceptionally well-preserved skeletons with soft tissues of the non-pterodactyloid pterosaurs Batrachognathus volans and Sordes pilosus (Riabinin 1948; Sharov 1971; Unwin and Bakhurina 1994). The first pterosaur bones from the northeastern Aral Sea region of Kazakhstan were described by Nesov (1984). Subsequently, two taxa have been described from the Figure 1. Map to show the northeastern Aral Sea region of Kazakhstan and the approximate positions of known Late Cretaceous pterosaur localities (1 Tyulkili 2 Baibishe 3 Akkurgan 4 Buroinak 5 Shakh- Shakh). The lakes in the western part of the map are remnants of the Aral Sea, relics of the Turgai Strait that once connected the Tethys and Arctic oceans. The paleoenvironments of azhdarchid pterosaurs localities in the Late Cretaceous... 61 Bostobe Formation: Aralazhdarcho bostobensis (Averianov 2004, 2007a) and Samrukia nessovi (Buffetaut 2011; Naish et al. 2012). Here we review all previous finds of ptero- saurs from the northeastern Aral Sea region, report on additional specimens collected on our expedition in 2012, and discuss the paleoenvironment of the pterosaurs that lived in this region. Institutional abbreviations: CCMGE, Chernyshev’s Central Museum of Geo- logical Exploration, Saint Petersburg, Russia; SMNK PAL, Staatliches Museum für Naturkunde, Karlsruhe, Germany; WDC, the Wyoming Dinosaur Center, Thermopo- lis, USA; ZIN PH and ZIN PO, Paleoherpetological and Paleoornithological collections of the Zoological Institute of the Russian Academy of Sciences, Saint Petersburg, Russia. Late Cretaceous pterosaur localities in Kazakhstan Tyulkili The Tyulkili [=Tjulkeli] hills (known in the paleobotanical literature as the Kankazgan locality) are located about 80 km north of Dzhusaly railway station in northeastern Kazakhstan (Fig. 1). Here the Zhirkindek Formation is exposed and is composed of sands interbedded with clays and silts (Shilin 1998; Kordikova et al. 2001). The fer- ruginous sandstone at the bottom of the Zhirkindek Formation section at Tyulkili hills has yielded numerous plant remains, including 36 species of fossil angiosperms (Shilin 1982, 1986, 1998). The next bed up-sequence, consisting of yellow-grey and grey clays, represents an ingression of brackish waters. It has produced fossilized wood, numerous remains of crustaceans, shark teeth (Protolamna sp., Scapanorhynchus sp.) and coprolites, the isolated bones of lindholmemydid and trionychid turtles, crocodyliforms, ornitho- pods (Hadrosauroidea indet.), possible sauropods, and laterally compressed teeth of theropods (Tyrannosauroidea indet.) (Nesov 1995, 1997). Indeed, in 2012 the tooth of a marine shark Cretodus longiplicatus was found at this level, a species characteristic of the Cenomanian of the Tethys region (Werner 1989; Kennedy et al. 2008; Underwood et al. 2011). According to Sokolov (1978), this species [=Semiplicatodus sulcatus in his usage] is widely distributed in late Albian – Cenomanian deposits of the Mangyshlak Peninsula and western Turkmenistan but is rare in the Turonian of Kazakhstan. The main fossiliferous horizon at the Tyulkili locality is confined to the middle sandstone bed, about 18 m above the base of the Zhirkindek Formation (Kordikova et al. 2001). In 1982, Nesov collected the remains of plesiosaurs, crocodyliforms, ptero- saurs (cf. Azhdarchidae) and dinosaurs (Ankylosauridae indet., Hadrosauroidea in- det., Neoceratopsia indet., Sauropoda indet., Tyrannosauroidea indet., Ornithomimi- dae indet., and Therizinosauroidea indet.) at this level (Nesov 1995, 1997; Averianov 2007b, 2009; Averianov and Sues 2009). Martinson (1990b, 1997) reported six spe- cies of bivalves (Trigonioidea and Unionoidea) from unspecified levels of the Zhirkind- ek Formation at Tyulkili (Kankazgan). Much later, Kordikova et al. (2001) reported gastropods, bivalves, brachiopods, crustaceans, selachians, osteichthyans, amphibians, 62 Alexander Averianov et al. / ZooKeys 483: 59–80 (2015) varanoid lizards, trionychid turtles, crocodyliforms (cited as “Turanosuchus aralensis” [=Kansajsuchus borealis]) and ornithomimid, tyrannosaurid, and dromaeosaurid thero- pods from this horizon. In 2012, we collected a microvertebrate sample from this level that included shark teeth and spines (Hybodus sp., Polyacrodus sp.), numerous gar scales and bones (Lepisosteidae indet.), rare dinosaur teeth and salamander bones (Skutschas 2013). Further up in the section, at the top part of the middle sandy bed, there are also shark teeth and spines (Hybodontidae indet., Odontaspididae indet., Scapano- rhynchus sp.), holostean (Lepisosteidae indet.), teleostean bones and scales, bones of lindholmemydid and trionychid turtles, crocodyliforms, dinosaurs, and fragments of pterosaur hollow bones (Nesov 1997). The upper part of the Zhirkindek Formation at Tyulkili hills is composed of light grey clays from which abundant plant remains as well a bird feather have been collected (Shilin 1986: fig. 3; Nesov 1992a). The flora known from the lowermost sandstone bed of the Zhirkindek Forma- tion at Tyulkili is dominated by Platanus species and thermophilous conifers (Shilin 1998) and likely corresponds