[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Ichthyosaurus and Temnodontosaurus in Nottinghamshire, England + lizard breathing + fish evolution



Ben Creisler
bcreisler@gmail.com

A number of recent non-dino papers that may be of interest:


Dean R. Lomax & Benjamin J.A. Gibson (2015)
The first definitive occurrence of Ichthyosaurus and Temnodontosaurus
(Reptilia: Ichthyosauria) in Nottinghamshire, England and a review of
ichthyosaur specimens from the county.
Proceedings of the Geologists' Association (advance online publication)
doi:10.1016/j.pgeola.2015.05.006
http://www.sciencedirect.com/science/article/pii/S0016787815000656

The occurrence of ichthyosaurs from Nottinghamshire is poorly
documented. Here, we report on at least 67 specimens from museum and
university collections. The specimens range from isolated elements to
nearly complete skeletons. Preservation varies, but some are
three-dimensional. The identification of both Ichthyosaurus and
Temnodontosaurus in the county adds additional localities for the
occurrence of those genera. Nottinghamshire is one of only a few
counties to have yielded a fairly substantial number of ichthyosaur
specimens. They are from localities in the Upper Triassic (Penarth
Group) and Lower Jurassic (Lower Lias Group) that can no longer be
accessed.

==


C. G. Farmer (2015)
Unidirectional flow in lizard lungs: a paradigm shift in our
understanding of lung evolution in Diapsida.
Zoology (advance online publication)
doi:10.1016/j.zool.2015.06.001
http://www.sciencedirect.com/science/article/pii/S0944200615000549



Conventional wisdom has held that unidirectional pulmonary airflow is
unique to birds and is an adaption enabling high rates of gas
exchange, essential for sustaining flight as well as an endothermic
metabolism. Recent visualizations and measurements of flow in the
lungs of monitor and iguanid lizards show a bird-like pattern of
unidirectional flow in these lineages. These findings call for a
paradigm shift in our understanding of lung evolution in diapsids.
This pattern of flow is not unique to birds. It is much older than
previously believed, and it may be advantageous to the low-energy
lifestyles typical of ectothermic animals.

====




Guillaume Guinot and Lionel Cavin (2015)
‘Fish’ (Actinopterygii and Elasmobranchii) diversification patterns
through deep time.
Biological Reviews (advance online publication)
DOI: 10.1111/brv.12203
http://onlinelibrary.wiley.com/doi/10.1111/brv.12203/abstract



Actinopterygii (ray-finned fishes) and Elasmobranchii (sharks, skates
and rays) represent more than half of today's vertebrate taxic
diversity (approximately 33000 species) and form the largest component
of vertebrate diversity in extant aquatic ecosystems. Yet, patterns of
‘fish’ evolutionary history remain insufficiently understood and
previous studies generally treated each group independently mainly
because of their contrasting fossil record composition and
corresponding sampling strategies. Because direct reading of
palaeodiversity curves is affected by several biases affecting the
fossil record, analytical approaches are needed to correct for these
biases. In this review, we propose a comprehensive analysis based on
comparison of large data sets related to competing phylogenies
(including all Recent and fossil taxa) and the fossil record for both
groups during the Mesozoic–Cainozoic interval. This approach provides
information on the ‘fish’ fossil record quality and on the corrected
‘fish’ deep-time phylogenetic palaeodiversity signals, with special
emphasis on diversification events. Because taxonomic information is
preserved after analytical treatment, identified palaeodiversity
events are considered both quantitatively and qualitatively and put
within corresponding palaeoenvironmental and biological settings.
Results indicate a better fossil record quality for elasmobranchs due
to their microfossil-like fossil distribution and their very low
diversity in freshwater systems, whereas freshwater actinopterygians
are diverse in this realm with lower preservation potential. Several
important diversification events are identified at familial and
generic levels for elasmobranchs, and marine and freshwater
actinopterygians, namely in the Early–Middle Jurassic (elasmobranchs),
Late Jurassic (actinopterygians), Early Cretaceous (elasmobranchs,
freshwater actinopterygians), Cenomanian (all groups) and the
Paleocene–Eocene interval (all groups), the latter two representing
the two most exceptional radiations among vertebrates. For each of
these events along with the Cretaceous-Paleogene extinction, we
provide an in-depth review of the taxa involved and factors that may
have influenced the diversity patterns observed. Among these,
palaeotemperatures, sea-levels, ocean circulation and productivity as
well as continent fragmentation and environment heterogeneity (reef
environments) are parameters that largely impacted on ‘fish’
evolutionary history, along with other biotic constraints.