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Redescription of neoceratopsian dinosaur Archaeoceratops and early evolution of Neoceratopsia

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You H., Dodson P.

Acta Palaeontologica Polonica

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2003

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tom 48

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nr 2

Archaeoceratops oshimai Dong and Azuma, 1997 is a basal neoceratopsian from the late Early Cretaceous of Mazongshan area, Gansu Province, northwest China. Here we provide a detailed description on Archaeoceratops oshimai based on both the holotype, which consists of a well preserved, nearly complete skull, partial vertebral column, and partial pelvis, and the paratype, which consists of a partial vertebral column including a nearly complete tail, a partial pelvis, fragmentary hind limb bones, and a complete pes. Cladistic analysis shows that Archaeoceratopsis the sister group to all currently known Late Cretaceous Neoceratopsia, and Late Cretaceous Neoceratopsia diverged into two clades: the Asian Protoceratopsidae and the North American Ceratopsoidea, indicating a dual evolution for the two major groups of horned dinosaurs in two landmasses of Late Cretaceous. A suite of derived features characterizes Ceratopsoidea, such as a round−shaped external naris, a long caudolateral process of the rostral bone, and ventrally curved premaxillary ventral edge.

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A new diplodocoid sauropod dinosaur from the Upper Jurassic Morrison Formation of Montana, USA

100%

Harris J. D., Dodson P.

Acta Palaeontologica Polonica

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2004

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tom 49

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nr 2

A partial skeleton of a new sauropod dinosaur from the Upper Jurassic Morrison Formation (?Tithonian) of Montana is described. Suuwassea emilieae gen. et sp. nov. is diagnosed by numerous cranial, axial, and appendicular autapomorphies. The holotype consists of a premaxilla, partial maxilla, quadrate, braincase with partial skull roof, several partial and complete cranial and middle cervical, cranial dorsal, and caudal vertebrae, ribs, complete scapulocoracoid, humerus, partial tibia, complete fibula, calcaneus, and partial pes. It displays numerous synapomorphies of the Diplodocoidea, including characters of both the Diplodocidae (Apatosaurus + (Diplodocus + Barosaurus)) and Dicraeosauridae (Dicraeosaurus + Amargasaurus). Preliminary phylogenetic analysis indicates that Suuwassea is a diplodocoid more derived than rebbachisaurids but in a trichotomy with both the Diplodocidae and Dicraeosauridae. Suuwassea represents the first well−supported, North American, non−diplodocid representative of the Diplodocoidea and provides new insight into the origins of both the Diplodocidae and Dicraeosauridae.

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Bone Microstructure and Relative Age of the Holotype Specimen of the Diplodocoid Sauropod Dinosaur Suuwassea emilieae

81%

Hedrick B. P., Tumarkin-Deratzian A. R., Dodson P.

Acta Palaeontologica Polonica

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2014

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tom 59

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nr 2

We present the first study of bone microstructure in Suuwassea emilieae, a diplodocoid sauropod from the Morrison Formation. Although the holotype of Suuwassea was recently identified as a subadult, bone histology demonstrates that this individual had reached sexual maturity at approximately 75–80% of maximum adult size. The smaller size of the holotype of Suuwassea relative to contemporary sauropods is due to ontogeny rather than a true reflection of adult size. A fully adult individual would have likely been similar in size to a fully adult specimen of Apatosaurus. Suuwassea has a number of plesiomorphic characters that might have been explained by its supposed early ontogenetic status, and would then have called the validity of the taxon into question. However, our demonstration that it was an adult confirms that these features represent retention of plesiomorphic character states or evolutionary reversals in a derived animal. Additionally, the specimen shows extensive cortical drift and secondary osteon formation related to skeletal loading, which is often obscured by complete remodeling of Haversian systems in sauropod taxa. There are substantial differences in the microstructure across the bone, which could make histologic samples not based upon complete cross sections problematic. Suuwassea is one of four currently recognized dicraeosaurid taxa, and this study contributes potential taxonomic characters in sauropod bone microstructure.

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New data on cranial anatomy of the ceratopsian dinosaur Psittacosaurus major

80%

You H. L., Tanoue K., Dodson P.

Acta Palaeontologica Polonica

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2008

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tom 53

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nr 2

An exceptionally preserved skull and mandible of ceratopsian dinosaur Psittacosaurus major revealed many anatomical details such as the existence of an elliptical median interpremaxillary foramen, a prominent neurovascular canal on the internal wall of the beak, long, slightly divergent basipterygoid processes developed as vertical blades with a deep cleft between them, and horizontally oriented vomer. The new specimen shows two autapomorphies of Psittacosaurus major, the transversely narrow dorsal skull roof and very prominent dentary flanges, confirming the presence of two large−skulled psittacosaur species in the Lujiatun Bed of the Lower Cretaceous Yixian Formation in Beipiao City, western Liaoning Province, China, the longand narrow−skulled P. major, and broad−skulled P. lujiatunensis.

Ograniczanie wyników

4 Acta Palaeontologica Polonica

4 Dodson P.

1 Harris J. D.

1 Hedrick B. P.

1 Tanoue K.

1 Tumarkin-Deratzian A. R.

1 You H.

1 You H. L.

1 2014

1 2008

1 2004

1 2003

Redescription of neoceratopsian dinosaur Archaeoceratops and early evolution of Neoceratopsia

A new diplodocoid sauropod dinosaur from the Upper Jurassic Morrison Formation of Montana, USA

Bone Microstructure and Relative Age of the Holotype Specimen of the Diplodocoid Sauropod Dinosaur Suuwassea emilieae

New data on cranial anatomy of the ceratopsian dinosaur Psittacosaurus major