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Kubo T.,Fukui Prefectural Dinosaur Museum | Kubo M.O.,University of Tokyo
Paleobiology | Year: 2012

Bipedalism evolved more than twice among archosaurs, and it is a characteristic of basal dinosaurs and a prerequisite for avian flight. Nevertheless, the reasons for the evolution of bipedalism among archosaurs have barely been investigated. Comparative analysis using phylogenetically independent contrasts showed a significant correlation between bipedality (relative length of forelimb) and cursoriality (relative length of metatarsal III) among Triassic archosaurs. This result indicates that, among Triassic archosaurs, bipeds could run faster than quadrupeds. Bipedalism is probably an adaptation for cursoriality among archosaurs, which may explain why bipedalism evolved convergently in the crocodilian and bird lineages. This result also indicates that the means of acquiring cursoriality may differ between archosaurs and mammals. © 2012 The Paleontological Society. All rights reserved. Source


Kubo T.,Fukui Prefectural Dinosaur Museum | Mitchell M.T.,Royal Tyrrell Museum of Palaeontology | Henderson D.M.,Royal Tyrrell Museum of Palaeontology
Journal of Vertebrate Paleontology | Year: 2012

A new elasmosaurid plesiosaur, Albertonectes vanderveldei, gen. et sp. nov., is described on the basis of an almost complete postcranial skeleton from the upper Campanian, Bearpaw Formation in Alberta, Canada. The new taxon is distinguished by a unique set of characters76 cervicals, lateral longitudinal ridge on posterior-most cervicals, relatively wide clavicular arch, tapered ventral projection at the median symphysis of coracoids, pointed anterolateral projection of pubis, fused posterior-most caudal vertebrae, and a relatively slender humerus. Ninety-seven chert gastroliths were also recovered with the specimen, and their mean diameters range from <1 to 13.5 cm. Shape analysis indicates that most of the gastroliths were ingested in the vicinity of a beach environment. Evidence that the carcass was scavenged by sharks includes a tooth-marked coracoid, two shed Squalicorax sp. teeth, and small, localized disruptions to the skeleton. Preliminary phylogenetic analysis confirms the inclusion of Albertonectes in a clade comprised of middle to Late Cretaceous, long-necked elasmosaurid plesiosaurs. The number of cervical vertebrae associated with different elasmosaur genera does not show any correlation with phylogeny. Both neck and total body length of Albertonectes are the longest among known elasmosaurs, and highlight the morphological extremes attained by this group of plesiosaurs. © 2012 Copyright Taylor and Francis Group, LLC. Source


Kubo T.,Fukui Prefectural Dinosaur Museum | Kubo M.O.,University of Tokyo
Palaios | Year: 2013

Fossilized trackways have rarely been analyzed quantitatively to examine major trends and patterns in evolution despite their potential utility, especially in understanding locomotory evolution. In the present study, trackways of Triassic archosauriforms were analyzed. The analyses showed foot and stride lengths of archosauriforms increased from the Early to Middle Triassic, especially those of dinosauromorphs, which tripled. Dinosauromorphs were much smaller in foot length and stride length compared to other archosauriforms during the Early Triassic. They reached similar stride length compared with other archosauriforms during the Middle Triassic and similar foot length in the Late Triassic. Stride/foot ratio is significantly higher in dinosauromorphs compared to other archosauriforms throughout the Triassic. This relatively long stride length of dinosauromorphs is attributed to either faster speed or higher relative hip height that was probably caused by their digitigrade foot posture. Analyses of trackway data sets, especially in combination with precise trackmaker assignment and age determination, would bring us more thorough knowledge about locomotory evolution of tetrapods that complements body fossil evidence. © 2013 SEPM (Society for Sedimentary Geology). Source


Ichishima H.,Fukui Prefectural Dinosaur Museum
Memoir of the Fukui Prefectural Dinosaur Museum | Year: 2011

The mammalian ethmoid is situated between the walls of the orbits and is bounded dorsally by the frontal, laterally by the maxilla, and ventrally by the vomer and palatine. It consists of four parts: a horizontal or cribriform plate, forming part of the internal cranial base; a median perpendicular plate, constituting part of the nasal septum; and two lateral masses or labyrinths. The perpendicular plate of the ethmoid is also referred to as the mesethmoid. The mesethmoid has widely been recognised in odontocetes, regardless of extant or extinct, but previous studies showed that the mesethmoid was absent in some groups of mammals. The close examination of bones and cartilages forming the internal cranial base of neonatal and perinatal dolphins, infant wild boars, and a newborn calf reveals that it is most likely that the cetaceans have no mesethmoid. © by the Fukui Prefectural Dinosaur Museum. Source


Kubo T.,Fukui Prefectural Dinosaur Museum
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

The body mass of extinct animals have never been estimated from footprints, despite its potential utility. To redeem this situation, the relationship between body mass and the areas of footprints was derived from 17 species of modern tetrapods. Body mass of seven ichnospecies of pterosaur tracks were estimated, because pterosaur body weight is an intriguing topic with reference to their flying ability. Estimated body weights of pterosaurs range from 110. g to 145. kg. The result provides evidence that large pterosaurs are about 10 times heavier than the heaviest modern bird. © 2010 Elsevier B.V. Source

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