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::: Info Dinosauria :::

Noticias, resúmenes e información

martes, septiembre 20, 2005

Cavidad endocranial en dinosaurios ornitisquios. Nueva evidencia

New evidence on brain−endocranial cavity relationships in ornithischian dinosaurs

DAVID C. EVANS Evans, D.C. 2005. New evidence on brain−endocranial cavity relationships in ornithischian dinosaurs. Acta Palaeontologica Polonica 50 (3): 617–622.

Discussions of brain morphology and relative brain size in nonavian dinosaurs have been complicated by uncertainty in the extent to which the brain filled the endocranial cavity.Recently reported vascular imprints (valleculae) on the endocranial surfaces of the braincase suggest that nonavian maniraptoriform theropods had brains that tightly fit the endocranium. Similar impressions of the intracranial vascular system are reported here in two ornithischian clades, Hadrosauridae and Pachycephalosauridae. These structures are more widespread in dinosaurs than previously thought, and suggest that the brain closely fit the endocranium in some regions of the forebrain through hindbrain in several distantly related dinosaur groups.

Primer Saurópodo en Shan-Thai, Asia


First dinosaur from the Shan-Thai Block of SE Asia: a Jurassic sauropod from the southern peninsula of Thailand

Eric Buffetaut, Varavudh Suteethorn, Haiyan Tong, Adrijan Kosir. Journal of the Geological Society. May 2005.Vol.162 Part 3.pg. 481, 4 pgs

A vertebra collected from the Jurassic non-marine Khlong Min Formation of southern Thailand is referred to the family Euhelopodidae, a group of sauropod dinosaurs that apparently was endemic to eastern Asia during the Jurassic and Early Cretaceous, at a time when that part of the world was isolated from other land masses. The occurrence of a euhelopodid in the Jurassic of the Shan-Thai Block supports the idea of a collision of the Shan-Thai Block with the Indochina Block, thus establishing connections with 'mainland Asia', early in the Mesozoic, probably before the Jurassic.

Nuevo Pterosaurio de la Isla de Wight


A new pterodactyloid pterosaur from the Wessex Formation (Lower Cretaceous) of the Isle of Wight, England

Lorna Steel, David M. Martill, David M. Unwin and John D. Winch

Abstract: A new pterosaur specimen comprising a partial skull and associated postcranial elements from the Lower Cretaceous Wessex Formation of Yaverland, Isle of Wight, southern England, is assigned to a new genus and species of ornithocheirid pterosaur, Caulkicephalus trimicrodon gen. et sp. nov., based on several unique features including a heterodont dentition in which the fifth, sixth and seventh teeth are reduced in size compared with those at positions 1e4 and 8e9; the presence of a frontoparietal crest and maxillopremaxillary crest that do not unite over the antorbital fenestra or cranium; a palatal ridge that extends no further forward
than the eighth to ninth tooth pairs. The new taxon is the second species of pterosaur from the Wealden Group of the Wessex Basin.

lunes, septiembre 19, 2005

Tomografía computarizada del endocráneo de Ceratosaurus


The endocranium of the theropod dinosaur Ceratosaurus studied with computer tomography

Sanders, R. Kent, & David K. Smith, 2005.
Acta Palaeontologica Polonica 50 (3): 601-616


Abstract: A well preserved specimen of the theropod Ceratosaurus has
from the Upper JurassicMorrison Formation of western Colorado was
recently described and given the name C. magnicornis. The systematics
of the genus is outside the scope of the present study but, as a
generally accepted basal tetanuran, the braincase was CT scanned to
provide a description of the endocranium, inner ear, pneumatic, and
venous sinus systems in a primitivemember of this clade. Fivemajor
subregions of the theropod endocranium are distinguished for the
purpose of simplifying cranial computed tomographic interpretation and
to provide a systematic means of comparison to other endocrania. The
skull morphology of Ceratosaurus influences the overall braincase
morphology and the number and distribution of the major foramina. The
low pontine angle and relatively unflexed braincase is considered a
more primitive character. The orientation of the horizontal
semicircular canal confirms a rather horizontal and unerect posture of
the head and neck.As in birds, the narrower skullmorphology of
Ceratosaurus is associated with fewer cranial nerve foramina.
Additionally, the maxillary dominated dentigerous upper jaw of
Ceratosaurus is felt to share with the alligator a large rostrally
directed maxillary division of the trigeminal nerve and a small
ophthalmic branch. The upper bill of birds, being dominated by the
premaxillary and lacking teeth, is innervated predominantly by the
ophthalmic division of the trigeminal nerve. For this reason,
avian−based cranial nerve reconstructions are felt to be inappro−
priate for basal theropods. Ceratosaurus skull pneumatization and
possible evidence of olfactory conchal structures is on the other hand
very avian in character. Based on computed tomography, Ceratosaurus is
determined to have possessed a typical basal theropod endocranium and
bipedal vestibular system similar to Allosaurus.

viernes, septiembre 09, 2005

18 Metros de Pterosaurio !!


Fragmentos de huesos encontrados en Israel, Rumanía y Brasil permiten dimensionar la envergadura de este Pterosaurio en mas o menos 18 metros.
Los hallazgos fueron presentados en Dublín para la reunión anual de la Asociación Británica para el Avance de la Ciencia.

martes, septiembre 06, 2005

Distribución espaciotemporal de saurópodos primitivos (resúmen)


Integrating ichnofossil and body fossil records to estimate locomotor posture and spatiotemporal distribution of early sauropod dinosaurs: a stratocladistic approach
Jeffrey A. Wilson

Abstract: Fossil vertebrate distributions are typically based on body fossils, which are often poorly sampled at the margins of their true temporal and spatial ranges. Because vertebrate ichnofossils can be preserved in great abundance and in different environments than vertebrate body fossils, inclusion of ichnofossil data may improve sampled ranges. However, if ichnofossils are to serve as an independent source of distributional data, then their attribution to a body fossil group (i.e., trackmaker identification) cannot rely on temporal and spatial coincidence. Ichnofossils identified by synapomorphies can act as an independent source of distributional data that can modify spatial, temporal, and character distributions, which in turn may influence hypotheses of locomotor evolution.
In this paper I evaluate the spatial, temporal, and character distributions of early sauropod dinosaurs by using a combined ichnofossil and body fossil data set. Sauropod ichnofossils supplement the spatiotemporal distributions of early sauropods and provide important information on early sauropod foot posture that is rarely preserved or can only be inferred from body fossils. The presence of derived features in early-appearing ichnofossils challenges previous hypotheses of character transformation, implying either parallelism, reversal, or ghost lineages. Stratocladistics can be used to resolve conflicting character and temporal distributions frombody fossils and ichnofossils. Stratocladistic analysis of a combined ichnofossil and body fossil data set suggests a richer, more widely distributed diversity of early sauropods than currently recognized in body fossils and suggests that several locomotor characters originatedmuch earlier than implied by body fossils.

Jeffrey A. Wilson. Museum of Paleontology & Department of Geological Sciences, University of Michigan, 1109 Geddes Road, Ann Arbor, Michigan 48109-1079.