A new titanosauriform sauropod (Dinosauria: Saurischia) from the Lower Cretaceous of Hyogo, Japan

Abstract

A new genus and species of titanosauriform sauropod is erected based on a partial skeleton found in the Lower Cretaceous Sasayama Group of Hyogo Prefecture, SW Japan. The new taxon is here named as Tambatitanis amicitiae gen. et sp. nov., which is diagnosed by the following features of the caudal vertebrae, chevrons and braincase: the postzygapophysis and the summit of the neural spine of the anterior caudal vertebrae are located beyond the posterior border of the centrum, the spine of the anterior caudal vertebrae is curved strongly anteriorly and bow-shaped in lateral view, the summit of the neural spine is expanded and hemispherical with its anterior face excavated by the posterodorsal extension of a deep and narrow SPRF, the transverse process of the anterior caudal vertebrae are short and L shaped, the anterior chevron is the longest among sauropods in proportion to body size, the distal ends of the anterior chevrons are rod-shaped, the distal ends of the mid chevrons are transversely thin and anteroposteriorly long without cranial processes, and the dorsal border of the shaft of the paroccipital process that forms the ventral margin of the posttemporal fenestra is short mediolaterally and V-shaped in posterior view. A phylogenetic analysis suggests that T. amicitiae is a basal titanosauriform, possibly belonging to the East Asian endemic clade Euhelopodidae. The caudals and chevrons are described in detail in order to document highly autapomorphic features of the new taxon as well as potentially phylogenetically informative characters. The discovery of T. amicitiae suggests that East Asian basal titanosauriforms were diverse not only in the number of the taxa but also in the morphological variation of the caudal elements.

An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America's last giant sauropod

“…14A) (Sereno 1998;Wilson 2002Wilson , 2005 (Fig. 14B) (Salgado et al 1997;Calvo & Gonz alez Riga 2003;Mannion et al 2013;Saegusa & Ikeda 2014), or in an unresolved basal Figure 12. BIBE 45958, Alamosaurus sanjuanensis.…”

Dinosaur eggshell assemblage from Japan reveals unknown diversity of small theropods

“…Although bones and teeth from the Kamitaki locality have been identified as ankylosaur, basal hadrosauroid, titanosaur (Tambatitanis amicitiae), basal tyrannosauroid, therizinosauroid, and indeterminate theropods (Saegusa and Ikeda, 2014), the eggshells confirm the presence of at least one small ornithopod and four small theropods, likely oviraptorosaurs, troodontids, Table 6 Estimates of egg mass in selected non-avian theropod ootaxa/eggs. Egg size and eggshell thickness represent mean or median values.…”

“…Since 1978, about 20 dinosaur-bearing localities have been found, which have yielded mainly isolated bones and teeth (for review see Kobayashi et al, 2006), with the exception of a few partial skeletons (Kobayashi and Azuma, 2003;Ohashi and Barrett, 2009;Azuma and Shibata, 2010;Saegusa and Ikeda, 2014;Shibata and Azuma, 2015). Although dinosaur skeletal remains have been the subject of detailed descriptions (Azuma and Currie, 2000;Kobayashi and Azuma, 2003;Azuma and Shibata, 2010;Saegusa and Ikeda, 2014;Shibata and Azuma, 2015), other fossils that potentially belong to non-avian dinosaurs, such as eggshells, have been mentioned only briefly (Azuma, 2003;Hirayama et al, 2003) and have yet to be described. In this paper, we provide the first description of a dinosaur eggshell assemblage from Japan from a new locality in the Sasayama Group in the Hyogo Prefecture.…”

“…1). This locality has since yielded skeletal remains of anurans, lizards, and nonavian dinosaurs (i.e., a basal hadrosaurid, ankylosaur, titanosauriform sauropod, tyrannosauroid, therizinosauroid, and indeterminate theropods) (Saegusa and Ikeda, 2014), as well as numerous fossil eggshells. The eggshell fragments (n > 90) were collected from a relatively small area (11 Â 10 m) in a bonebed layer that contains articulated anuran skeletons, as well as isolated bones and/or teeth of the aforementioned dinosaurs.…”

“…The eggshell fragments (n > 90) were collected from a relatively small area (11 Â 10 m) in a bonebed layer that contains articulated anuran skeletons, as well as isolated bones and/or teeth of the aforementioned dinosaurs. The bone layer is contained within a reddish mudstone, interpreted to be a floodplain deposit (Saegusa and Ikeda, 2014). The layer is stratigraphically located in the lower part of the 'Lower Formation' of the Sasayama Group (Fig.…”