Shark faunas from the Late Jurassic—Early Cretaceous of northeastern Thailand

Abstract

A revision of the freshwater shark fauna from the Phu Kradung Formation in NE Thailand allows the recognition of a new species of Acrodus, which represents the youngest occurrence of the genus and confirms its displacement in freshwater environments after the Toarcian. The rest of the shark fauna includes teeth of Hybodus sp., aff. Hybodus sp., hybodontid dermal denticles, Jiaodontus sp., Lonchidion sp. A, Lonchidion sp. B, Heteroptychodus cf. H. kokutensis and dorsal fin spines. The presence of Jaiodontus and of unusual hybodontid dermal denticles suggests a Jurassic age for most of the Phu Kradung Formation, whereas the presence of Heteroptychodus suggests an Early Cretaceous age for the top of the Formation. However, the age of the Phu Kradung Formation is still uncertain, with contradictory signals coming from palynology, detrital zircon thermochronology and vertebrate palaeontology. In any case, it appears that this is the oldest occurrence of the genus Heteroptychodus, and suggests a Thai origin for this genus, which may have replaced Acrodus in the Thai freshwater palaeoecosystems. Together with Acrodus, the presence of Lonchidion sp. A suggests some European affinities for the shark fauna from the Phu Kradung Formation.

A new freshwater teleosaurid from the Jurassic of northeastern Thailand

“…Although palynological analyses point to an Early Cretaceous age for the Phu Kradung Formation, a Late Jurassic age for its lower part could not be ruled out by Racey and Goodall (2009). In the case of Phu Noi, because the locality is located within the lower part of the Phu Kradung Formation, a Late Jurassic (?Tithonian) age was recently proposed (Liard and Martin, 2011;Cuny et al, 2014;Liard et al, 2015;Martin et al, 2016). Nevertheless, the age of Phu Noi is not settled, in part because most of its faunal content is still under study since the discovery of the site in 2008.…”

“…The deposit shows evidence of aerial exposure with paleosol development and insect burrows (Martin et al, 2016) and in addition to the teleosaurids, contains a known fauna of both aquatic and terrestrial vertebrates. These include hybodont sharks (Cuny et al, 2014), the ginglymodian fish Isanichthys lertboosi , the xinjianchelyid turtle Phunoichelys thirakhupti (Tong et al, 2015) an undescribed freshwater turtle, ornithopods (Buffetaut et al, 2014), theropods (Chanthasit, 2011), and undescribed remains of sauropod dinosaurs, temnospondyls, and pterosaurs (Buffetaut et al, 2015).…”

A late Permian ichthyofauna from the Zechstein Basin, Lithuania-Latvia Region

“…Morphological similarities of the crown can be detected with Acrodus kalasinensis tooth from the Late Jurassic-Early Cretaceous of northeastern Thailand [42]. Also, similar teeth but evidently bigger were found and described as Acrodus spitzbergensis teeth from the Lower Triassic of Spitsbergen [43].…”

A new species of the ginglymodian fish Isanichthys (Actinopterygii, Holostei) from the Late Jurassic Phu Kradung Formation, northeastern Thailand

“…The Khorat Group comprises post-Triassic deposits on the Khorat Plateau and adjacent areas, and it has long been regarded as Late Jurassic, but palynological studies now suggest Early Cretaceous ages for most of the vertebrate-bearing horizons, i.e., the Phra Wihan, Sao Khua, Phu Phan and Khok Kruat formations (Racey et al 1994(Racey et al , 1996. The dating of the Phu Kradung Formation is still problematic, but a recent synthesis suggests a Late Jurassic age for its lowermost part, in which the Phu Noi locality is located, and a basal Cretaceous (Berriasian) age for the upper part (Racey 2009;Cuny et al 2013).…”

“…1). Although also exposing the Phu Kradung Formation, the new locality is at an older stratigraphical level than Phu Nam Jun (Cuny et al 2013). Phu Noi has yielded an array of tetrapods, as well as isolated shark teeth and some ginglymodian remains.…”