2011年

8月

21日

論文紹介

Mannion, Philip D. & Calvo, Jorge, O. 2011. Anatomy of the basal titanosaur (Dinosauria, Sauropoda) *Andesaurus delgadoi* from the mid-Cretaceous (Albian--early Cenomanian) Rio Limay Formation, Neuquen Province, Argentina: Implications for titanosaur systematics. _Zoological Journal of the Linnaean Society_ 163(1):155-181.
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00699.x/abstract


Abstract:
"Titanosauria is a taxonomically and morphologically diverse clade of sauropod dinosaurs that appeared in the Middle Jurassic and radiated in the mid?Late Cretaceous; however, its intrarelationships are poorly understood. The mid-Cretaceous Argentinean sauropod *Andesaurus delgadoi* has repeatedly been recovered at the base of Titanosauria, and thus represents a crucial taxon for determining the evolutionary history of this clade; yet it has only received a brief description. Here, we re-describe the holotype, comprising dorsal, sacral, and caudal vertebrae, as well as limb and pelvic elements. Detailed comparisons are made with a global array of titanosauriforms. *Andesaurus* is a valid genus and can be diagnosed by five autapomorphies: (1) posterior dorsal neural spine height greater than twice centrum height (autapomorphic within Macronaria); (2) square-shaped anterior?middle caudal centra in lateral view; (3) anteroposteriorly elongate fossa present on the anterodorsal corner of the lateral surface of middle?posterior caudal centra; (4) ridge along the midshaft of the ventral surface of metacarpal I, close to the ventromedial margin; (5) prominent ventromedial ridge along the distal half of metacarpal V. Other remains previously attributed to *Andesaurus* cannot be referred to this genus. Sixteen putative titanosaur synapomorphies can be recognized in *Andesaurus,* including: (1) lateral pneumatic foramina in dorsal vertebrae situated within fossae; (2) anterior?middle caudal vertebrae with ventrolateral ridges either side of a ventral midline hollow; and (3) lateral bowing of metacarpal I. This revision provides an important foundation for future phylogenetic analyses of titanosaurs, and adds to our growing understanding of this enigmatic clade. Lastly, we recommend the disuse of the coordinated suprageneric rank taxa of *Andesaurus* (Andesaurinae, Andesauridae, and Andesauroidea), at least until titanosaur intrarelationships are better elucidated."

 

Norman, David B., Crompton, Alfred W., Butler, Richard J., Porro, Laura B. & Charig, Alan J. 2011. The Lower Jurassic ornithischian dinosaur *Heterodontosaurus tucki* Crompton & Charig, 1962: Cranial anatomy, functional morphology, taxonomy, and relationships. _Zoological Journal of the Linnaean Society_ 163(1):182-276.
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00697.x/abstract

Abstract:
"The cranial anatomy of the Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962 is described in detail for the first time on the basis of two principal specimens: the holotype (SAM-PK-K337) and referred skull (SAM-PK-K1332). In addition several other specimens that have a bearing on the interpretation of the anatomy and biology of *Heterodontosaurus* are described. The skull and lower jaw of *Heterodontosaurus* are compact and robust but perhaps most notable for the heterodont dentition that merited the generic name. Details of the cranial anatomy are revealed and show that the skull is unexpectedly specialized in such an early representative of the Ornithischia, including: the closely packed, hypsodont crowns and ?warping? of the occlusal surfaces (created by progressive variation in the angulation of wear on successive crowns) seen in the cheek dentition; the unusual sutural relationships between the bones along the dorsal edge of the lower jaw; the very narrow, deeply vaulted palate and associated structures on the side wall of the braincase; and the indications of cranial pneumatism (more commonly seen in basal archosaurs and saurischian dinosaurs). Evidence for tooth replacement (which has long been recognized, despite frequent statements to the contrary) is suggestive of an episodic, rather than continuous, style of tooth replacement that is, yet again, unusual in diapsids generally and particularly so amongst ornithischian dinosaurs. Cranial musculature has been reconstructed and seems to conform to that typically seen in diapsids, with the exception of the encroachment of M. adductor mandibulae externus superficialis across the lateral surface of the temporal region and external surface of the lower jaw. Indications, taken from the unusual shape of the occlusal surfaces of the cheek dentition and jaw musculature, are suggestive of a novel form of jaw action in this dinosaur. The taxonomy of currently known late Karoo-aged heterodontosaurids from southern Africa i!
s reviewe
cated by the inadequate nature of much of the known material, it is concluded that two taxa may be readily recognized: *H. tucki* and *Abrictosaurus consors.* At least one additional taxon is recognized within the taxa presently named *Lanasaurus* and *Lycorhinus*; however, both remain taxonomically problematic and their status needs to be further tested and may only be resolved by future discoveries. The only other named taxon, Geranosaurus atavus, represents an invalid name. The recognition of at least four distinct taxa indicates that the heterodontosaurids were speciose within the late Karoo ecosystem. The systematics of *Heterodontosaurus* and its congeners has been analysed, using a restricted sample of taxa. A basal (nongenasaurian) position within Ornithischia is re-affirmed. There are at least four competing hypotheses concerning the phylogenetic placement of the Heterodontosauridae, so the evidence in support of the various hypotheses is reviewed in some detail. At present the best-supported hypothesis is the one which places Heterodontosauridae in a basal (non-genasaurian) position; however, the evidence is not fully conclusive and further information is still needed in respect of the anatomy of proximate outgroups, as well as more complete anatomical details for other heterodontosaurids. Heterodontosaurids were not such rare components of the late Karoo ecosystem as previously thought; evidence also suggests that from a phylogenetic perspective they occupied a potentially crucial position during the earliest phases of ornithischian dinosaur evolution."


Worthy, Trevor H. 2011. Descriptions and phylogenetic relationships of a new genus and two new species of Oligo-Miocene cormorants (Aves: Phalacrocoracidae) from Australia. _Zoological Journal of the Linnaean Society_ 163(1):277-314.
http://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00693.x/abstract

Abstract:
"Tertiary cormorant fossils (Aves: Phalacrocoracidae) from Late Oligocene deposits in Australia are described. They derive from the Late Oligocene ? Early Miocene (26?24 Mya) Etadunna and Namba Formations in the Lake Eyre and Lake Frome Basins, South Australia, respectively. A new genus, *Nambashag* gen. nov., with two new species (*Nambashag billerooensis* sp. nov., 30 specimens; *Nambashag microglaucus* sp. nov., 14 specimens), has been established. Phylogenetic analyses based on 113 morphological and two integumentary characters indicated that *Nambashag* is the sister taxon to the Early Miocene *Nectornis miocaenus* of Europe and all extant phalacrocoracids. As *Nambashag*, *Nectornis*, and extant phalacrocoracids constitute a strongly supported clade sister to *Anhinga* species, the fossil taxa have been referred to Phalacrocoracidae. Sulids and Fregata were successive sister taxa to the Phalacrocoracoidea, i.e. phalacrocoracids + *Anhinga*. As phalacrocoracids lived in both Europe and Australia during the Late Oligocene and no older phalacrocoracid taxa are known, the biogeographical origin of cormorants remains unanswered. The phylogenetic relationships of extant taxa were not wholly resolved, but contrary to previous morphological analyses, considerable concordance was found with relationships recovered by recent molecular analyses. *Microcarbo* is sister to all other extant phalacrocoracids, and all *Leucocarbo* species form a well-supported clade."

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