Sebastian G. DALMAN and Spencer G. LUCAS (2017)
On the dentary in the Fukui Prefectural Dinosaur Museum of Gorgosaurus libratus (Theropoda: Tyrannosauridae) from the Dinosaur Park Formation (Upper Cretaceous) of Alberta, Canada.
Memoir of the Fukui Prefectural Dinosaur Museum 16: 17-27
An isolated right dentary of the tyrannosaurid Gorgosaurus libratus in the Fukui Prefectural Dinosaur Museum found in the Dinosaur Park Formation in southern Alberta, Canada, is described. The referral of the dentary to G. libratus is based on several morphological features, including the lack of the posteroventral transitional point in the anterior step of the lingual bar, the foramen intermandibularis oralis overlaps ventrally the anterior terminus of the Meckelian groove, and the anterior terminus of the Meckelian groove contacts the posterior margin of the dentary symphysis. The excellent preservation of the dentary allows for detailed comparisons with other tyrannosaurids, especially with its close relative Albertosaurus sarcophagus with which G. libratus is often synonymized. The two taxa can be differentiated based on the overall morphology of the anterior step of the lingual bar, position of the foramen intermandibularis oralis with respect to the anterior terminus of the Meckelian groove, the posterior step of the Meckelian fossa, and the articulation facet and notch for the splenial. This work provides further support for recognizing G. libratus as a taxon distinct from and not a synonym of Albertosaurus.Â
Sebastian G. DALMAN, Steven E. JASINSKI and Spencer G. LUCAS (2017)
First occurrence of a Tyrannosauroid dinosaur from the Lower Campanian Merchantville formation of Delaware, USA.
Memoir of the Fukui Prefectural Dinosaur Museum 16: 29-38
This study provides a detailed osteological description of an isolated proximal caudal centrum and two nearly complete isolated metatarsals II and IV of the left foot of a gracile theropod dinosaur from the Lower Campanian of the Merchantville Formation in northern Delaware, USA. The caudal centrum and the metatarsals are referred to Tyrannosauroidea. The centrum is not well preserved, and thus not diagnostic; however, both metatarsals are diagnostic. The referral to Tyrannosauroidea is supported by several morphological features, including extensive surfaces on metatarsals II and IV for the articulation with metatarsal III, and a characteristic low, slightly convex muscle scar on metatarsal IV developed as a thin low ridge located on the posterior surface between the M. gastrocnemius pars lateralis insertion scar and the metatarsal III articular surface. This ridge has been previously interpreted as the plantar ridge, which is present in some derived Late Campanian tyrannosauroid taxa. Additionally, metatarsal IV has a deep medial notch for the accommodation of an "L"â shaped proximal articulation of metatarsal III, and a "U"â shaped proximal articular end. The Merchantville Formation tyrannosauroid exhibits arctometatarsalian metatarsals, as do tyrannosaurids. The Merchantville Formation tyrannosauroid is differentiated from other known basal and derived tyrannosaurids by having a characteristically shaped proximal articular surface of metatarsal II in which the proximal and posterior ends lie on the long axis of the proximal articular surface. However, the posterior proximal articular surface of metatarsal II is not as strongly angled laterally as in more derived tyrannosauroids. The Merchantville Formation tyrannosauroid adds to the record of Appalachian tyrannosauroid, evolution and paleostratigraphic position, and provides new morphological information about the metatarsal anatomy of these iconic theropods.Â
Shin-ichi SANO (2017)
Vertebrate diversity of the Early Cretaceous Tetori biota from Japan, the state of the art.
Memoir of the Fukui Prefectural Dinosaur Museum 16: 1â15ÂÂ
The comprehensive list of vertebrate skeletal fossils (excluding ichnofossils) from the Early Cretaceous Tetori Group is provided. Numbers of species of selected vertebrate taxonomic groups of the Tetori Group are compared with those from several famous Late JurassicâEarly Cretaceous LagerstÃtten to evaluate the vertebrate diversity of the Tetori Biota. Vertebrate fauna of the Tetori Group is characterized by the presence of a tritylodont synapsid, that of both diversified choristoderes and a crocodyliform, remarkably high diversity of the testudines, moderate diversity of mammals, squamates and dinosaurs, and possible low diversity of fish. Most of the vertebrate taxonomic groups recognized in other fauna/biotas are present in the Tetori Biota. The vertebrate diversity of the Tetori Biota can be considered to be comparable to those of the Late JurassicâEarly Cretaceous LagerstÃtten at present, and is expected to be higher in the near future. Further investigation and comparison of vertebrate diversities in almost coeval strata in several regions in East and Southeast Asia probably provide the useful information to reveal the paleo(bio)geographical and palaeoclimatic reconstruction in Asia, and also the evolution of the Mesozoic terrestrial ecosystem.Â