Titanosauriform teeth from the Cretaceous of Japan

Abstract

Sauropod teeth from six localities in Japan were reexamined. Basal titanosauriforms were present in Japan during the Early Cretaceous before Aptian, and there is the possibility that the Brachiosauridae may have been included. Basal titanosauriforms with peg-like teeth were present during the "mid" Cretaceous, while the Titanosauria with peg-like teeth was present during the middle of Late Cretaceous. Recent excavations of Cretaceous sauropods in Asia showed that multiple lineages of sauropods lived throughout the Cretaceous in Asia. Japanese fossil records of sauropods are conformable with this hypothesis.

Ornithischian dinosaur material from the Kuwajima Formation (Tetori Group: Lower Cretaceous) of Ishikawa Prefecture, Japan

“…Taking all of this information into account, i.e. an Hauterivian date from the formation itself, Hauterivian -Aptian dates for one lateral equivalent (Okurodani Formation) and a ?late Hauterivian -Barremian date for another lateral equivalent (Itsuki Formation), an Hauterivian -Barremian age seems most likely for the Kuwajima Formation (see also Saegusa and Tomida 2011).…”

“…Almost all of the vertebrate material collected from this unit thus far was recovered due to the construction of a road tunnel at the Kaseki-Kabe locality during 1997 -2000 . The tunnelling debris generated by this project was searched systematically for fossil material and this led to the recovery of a diverse vertebrate fauna that includes fish (Yabumoto 2005(Yabumoto , 2008(Yabumoto , 2014Yabumoto et al 2006), tritylodontid synapsids (Setoguchi et al 1999;Matsuoka and Setoguchi 2000), mammals (Rougier et al 2007;Kusuhashi 2008), lizards (Evans et al 2006;Manabe 2008, 2009), choristoderes (Matsumoto et al 2007(Matsumoto et al , 2015 and dinosaurs (Manabe et al 1989;Hasegawa et al 1995;; Barrett et al 2002;Ohashi and Barrett 2009;Saegusa and Tomida 2011). Other groups are also known from the area (amphibians, pterosaurs, various turtle and dinosaur taxa), but have so far been listed only in faunal summaries, conference abstracts or unpublished reports (e.g.…”

“…Although an Early Cretaceous age has been widely accepted for the Kuwajima Formation for some time (Maeda 1961), its exact age within this interval has been contentious as no marine intercalations are present and, until recently, the formation had not yielded any reliable radiometric dates (see discussions in Matsukawa and Obata 1994;Kusuhashi et al 2002;Fujita 2003;Saegusa and Tomida 2011). However, U -Pb radiometric dates from detrital zircons have been obtained from several tuff layers within the laterally equivalent Okurodani Formation of neighbouring Gifu Prefecture, which range in age from 132.9^0.9 Ma (Valanginian/Hauterivian boundary) to 117.5^0.7 Ma (Aptian) .…”

“…However, U -Pb radiometric dates from detrital zircons have been obtained from several tuff layers within the laterally equivalent Okurodani Formation of neighbouring Gifu Prefecture, which range in age from 132.9^0.9 Ma (Valanginian/Hauterivian boundary) to 117.5^0.7 Ma (Aptian) . Detrital zircons from a tuff bed within the Kuwajima Formation itself yielded a U -Pb age of 130.7^08 Ma (Hauterivian) ), but the position of this tuff bed relative to the bone-bearing horizons of the formation is unclear (Saegusa and Tomida 2011). Nevertheless, some biostratigraphical evidence has also suggested a Hauterivian age for the Kuwajima Formation (Fujita 2003).…”

“…Published reports include descriptions of an indeterminate theropod tooth (Manabe et al 1989), theropod footprints (Manabe et al 1989), a maniraptoran theropod ungual , titanosauriform sauropod teeth (Barrett et al 2002;Saegusa and Tomida 2011), heavily worn and partially resorbed iguanodontian teeth (Hasegawa et al 1995) and, the most complete dinosaur specimen yet recovered, a partial and semi-articulated skull of the small-bodied cerapodan ornithischian Albalophosaurus yamaguchiorum (Ohashi and Barrett 2009). Other dinosaur specimens, including numerous ornithischian and additional theropod teeth, as well as rare cranial elements, have been mentioned and figured in an unpublished report and in a general faunal overview , but have not been described in detail.…”