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Dinos and Mesozoic birds--some new papers but no new taxa
Polar Dinosaurs
Thomas H. Rich, Patricia Vickers-Rich, Roland A. Gangloff.
Polar Dinosaurs. Science (295): 979-980 (Feb. 8, 2002)
During the past 20 years, much evidence for dinosaurs that
lived in polar regions has been unearthed. These dinosaurs
may have been particularly adapted to extreme conditions,
but establishing exactly what these conditions were is
fraught with difficulties. In their Perspective, Rich et
al. chart what is known about polar dinosaurs and their
habitat, particularly in southeastern Australia and
Alaska.
Mohabey, D.M. 2001. Indian dinosaur eggs: A review.
JOURNAL OF THE GEOLOGICAL SOCIETY OF INDIA. 58 (6): 479-
508 (DEC 2001)
Review of the available work on Indian dinosaurs shows
that the majority of Indian dinosaur fossils are better
known from Late Cretaceous sediments (Lameta and
equivalents) than from the older pre-Late Cretaceous
sediments or Gondwana Group (Triassic to Late Jurassic).
Dinosaur eggs are so far unknown in the pre-Lameta
dinosaur-bearing sediments represented by Maleri
(Carnian), Dharamaram (Norian to Rhaetian) and Kota
(Liassic) Formations. Of these, the Kota Formation has
yielded near-complete skeletons of Barapasaurus tagorei (a
primitive sauropod) and Kotasaurus yamanapalliensis (a
transitional prosauropod to early sauropod), which are at
present the only two mounted dinosaur skeletons in
India.The present article provides a brief historical
review of the work on Indian dinosaurs. The stratigraphy,
geology and geographical distribution of dinosaur-bearing
sediments are discussed. The systematics of the Indian
dinosaur species are briefly described. As the present
author is mostly involved with the study of Indian
Cretaceous dinosaurs and their eggs, it would only be apt
in this article to place emphasis on Late Cretaceous
dinosaurs and their eggs. A wide diversity is observable
in the Indian dinosaur eggs, which are parataxonomically
assigned to oofamily Megaoolithidae, Elongatoolithidae and
Spheroolithidae. The problems involved in relating the
varied Indian egg oospecies to their parent dinosaur are
very challenging. However, based on the existing
knowledge, the megaloolithid and elongatoolithid eggs can
be attributed to titanosaurid and abelisaurid dinosaurs.
Nesting behaviour of these dinosaurs is discussed in this
paper. Evidences suggest that the environment during Late
Cretaceous in India provided an ideal niche for the
preferred habitat of these dinosaurs having an acme of
their breeding and nesting. However, these reptiles
struggled to survive the initial onslaught caused by the
Deccan volcanic eruption near the end of Cretaceous.
G. P. Ericson; Les Christidis; Alan Cooper; Martin
Irestedt; Jennifer Jackson; Ulf S. Johansson; Janette A.
Norman Source. 2002. A Gondwanan origin of passerine birds
supported by DNA sequences of the endemic New Zealand
wrens. Proceedings of the Royal Society of London:
Biological Sciences (269: 1488): 235 -- 241.
Zoogeographic, palaeontological and biochemical
data support a Southern Hemisphere origin for passerine
birds, while accumulating molecular data suggest that most
extant avian orders originated in the mid-Late Cretaceous.
We obtained DNA sequence data from the nuclear c-myc and
RAG-1 genes of the major passerine groups and here we
demonstrate that the endemic New Zealand wrens
(Acanthisittidae) are the sister taxon to all other extant
passerines, supporting a Gondwanan origin and early
radiation of passerines. We propose that (i) the
acanthisittids were isolated when New Zealand separated
from Gondwana (ca. 82-85 Myr ago), (ii) suboscines, in
turn, were derived from an ancestral lineage that
inhabited western Gondwana, and (iii) the ancestors of the
oscines (songbirds) were subsequently isolated by the
separation of Australia from Antarctica. The later spread
of passerines into the Northern Hemisphere reflects the
northward migration of these former Gondwanan elements.
Schweitzer, M.H. & Marshall, C.L. 2001. A molecular model
for the evolution of endothermy in the Theropod-Bird
lineage. JOURNAL OF EXPERIMENTAL ZOOLOGY. DEC 15 2001; 291
(4) : 317-338
Ectothermy is a primitive state; therefore, a shared
common ancestor of crocodiles, dinosaurs, and birds was at
some point ectothermic. Birds, the extant descendants of
the dinosaurs, are endothermic. Neither the metabolic
transition within this lineage nor the place the dinosaurs
held along the ectothermic-endothermic continuum is
defined. This paper presents a conceptual model for the
evolution of endothermy in the theropod-bird lineage. It
is recognized that other animals (some fish, insects,
etc.) are functionally endothermic. However, endothermy in
other clades is beyond the scope of this paper, and we
address the onset of endothermy in only the theropod/bird
clade. The model begins with simple changes in a single
gene of a common ancestor, and it includes a series of
concomitant physiological and morphological changes,
beginning perhaps as early as the first archosaurian
common ancestor of dinosaurs and crocodiles. These changes
continued to accumulate within the theropod-avian lineage,
were maintained and refined through selective forces, and
culminated in extant birds. Metabolic convergence or
homoplasy is evident in the inherent differences between
the endothermy of mammals and the endothermy of extant
birds. The strength and usefulness of this model lie in
the phylogenetic, genetic, evolutionary, and adaptive
plausibility of each of the suggested developmental steps
toward endothermy. The model, although conceptual in
nature, relies on an extensive knowledge base developed by
numerous workers in each of these areas. In addition, the
model integrates known genetic, metabolic, and
developmental aspects of extant taxa that phylogenetically
bracket theropod dinosaurs for comparison with information
derived from the fossil record of related extinct taxa.
Dyke, G.J. 2001. The evolutionary radiation of modern
birds: Systematics and patterns of diversification.
Geological Journal. 2001; 36(3-4): 305-315
The timing of the evolutionary radiation of the
modern, or neornithine, birds is controversial. The fossil
record has indicated that the radiation occurred mainly in
the aftermath of the Cretaceous-Tertiary (KT) extinction
event. However, recent estimates of lineage divergengce
times calculated from molecular data have instead
indicated that most of the major clades of modern birds
originated in the Cretaceous. Because the known Mesozoic
fossil record of modern birds is poor, fossils from the
early Tertiary provide the first opportunity to document
the pattern of the radiation. The limited phylogenetic
hypotheses produced to date and including this post-KT
fossil material suggest that only some of the 'more basal'
clades of modern birds were, most likely, present during
the Mesozoic Era, and that the radiation of the 'more
derived' landbird group of clades occurred in the early
Tertiary.