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Origin of teeth and other non-dino papers



From: Ben Creisler
bcreisler@gmail.com


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

Duncan J. E. Murdock,  Xi-Ping Dong,  John E. Repetski,  Federica
Marone, Marco Stampanoni & Philip C. J. Donoghue (2013)
The origin of conodonts and of vertebrate mineralized skeletons.
Nature  (advance online publication)
doi:10.1038/nature12645
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12645.html



Conodonts are an extinct group of jawless vertebrates whose tooth-like
elements are the earliest instance of a mineralized skeleton in the
vertebrate lineage, inspiring the ‘inside-out’ hypothesis that teeth
evolved independently of the vertebrate dermal skeleton and before the
origin of jaws. However, these propositions have been based on
evidence from derived euconodonts. Here we test hypotheses of a
paraconodont ancestry of euconodonts using synchrotron radiation X-ray
tomographic microscopy to characterize and compare the microstructure
of morphologically similar euconodont and paraconodont elements.
Paraconodonts exhibit a range of grades of structural differentiation,
including tissues and a pattern of growth common to euconodont basal
bodies. The different grades of structural differentiation exhibited
by paraconodonts demonstrate the stepwise acquisition of euconodont
characters, resolving debate over the relationship between these two
groups. By implication, the putative homology of euconodont crown
tissue and vertebrate enamel must be rejected as these tissues have
evolved independently and convergently. Thus, the precise ontogenetic,
structural and topological similarities between conodont elements and
vertebrate odontodes appear to be a remarkable instance of
convergence. The last common ancestor of conodonts and jawed
vertebrates probably lacked mineralized skeletal tissues. The
hypothesis that teeth evolved before jaws and the inside-out
hypothesis of dental evolution must be rejected; teeth seem to have
evolved through the extension of odontogenic competence from the
external dermis to internal epithelium soon after the origin of jaws.



News release:

http://www.bristol.ac.uk/news/2013/9830.html

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Vladimir Dinets  (2013)
Long-Distance Signaling in Crocodylia.
Copeia 2013(3):517-526
doi: http://dx.doi.org/10.1643/CE-12-125
http://www.bioone.org/doi/abs/10.1643/CE-12-125





Long-distance signals such as bellows, roars, headslaps, and
infrasound pulses are important components of crocodilian behavioral
repertoire, yet there is little or no published information on
signaling for many species. Here, original data augmented with a
compilation of published and unpublished sources are presented for 24
species of crocodilians. Their analysis shows that crocodilians adapt
their signal composition to habitat structure by choosing physically
different components. Flexible multi-component composition might
partially explain the extraordinary evolutionary longevity of
crocodilian signaling. Comparative analysis provides novel evidence
for solving the long-standing debate about the phylogeny of the genus
Tomistoma, supporting its affinities with crocodiles rather than true
gharials. It also suggests that the absence of species with adult male
length of less than 120 cm among extant crocodilians might be caused
by the necessity of producing infrasound as an honest signal of
status.


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Soichiro Kawabe, Tatsuro Ando & Hideki Endo (2013)
Enigmatic affinity in the brain morphology between plotopterids and
penguins, with a comprehensive comparison among water birds.
Zoological Journal of the Linnean Society (advance online publication)
DOI: 10.1111/zoj.12072
http://onlinelibrary.wiley.com/doi/10.1111/zoj.12072/abstract

Plotopterids (Aves: Plotopteridae) are extinct flightless birds that
were endemic to the North Pacific Ocean. As flightless, wing-propelled
diving birds they exhibit similar skeletal morphology to
Sphenisciformes (penguins), especially in their wings. In contrast to
the similarity, Plotopteridae have been placed in (traditional)
Pelecaniformes in most palaeontological and phylogenetic studies,
based on shared characters that are absent in penguins. The
postcranial morphology of Plotopteridae has been well studied, but
little is known about the cranial morphology, particularly the nervous
system. The brain morphology of Plotopteridae, compared with other
water birds, could prompt a reconsideration of those previous
phylogenetic hypotheses, as the cranial morphology is conservative and
could provide powerful signals for the phylogenetic reconstruction. In
order to compare the brain morphology of Plotopteridae with that in
other water birds (Ciconiiformes, Pelecaniformes, Suliformes,
Procellariiformes, and Sphenisciformes), we generated virtual
endocasts of Plotopteridae and extant water birds. We investigated the
brain morphology of those birds using three-dimensional geometric
morphometric and linear measuring methods. The width of the cerebellum
and the length of the floccular lobe varied considerably among water
birds, and the relative lengths separate Procellariiformes +
Sphenisciformes from Ciconiiformes + Pelecaniformes + Suliformes. The
former group had a relatively wider cerebellum and longer floccular
lobe, whereas the latter group had a relatively narrower cerebellum
and shorter floccular lobe. The relative width of the cerebellum and
length of the floccular lobe in Plotopteridae was comparable with that
of the former group, in addition to many morphological similarities to
the Sphenisciformes brain. On the basis of brain morphology alone, we
dare not conclude that Plotopteridae forms a clade with, or belongs
to, Sphenisciformes; however, the brain configuration of Plotopteridae
is distinctly close to that of penguins, and could possibly reflect
their phylogenetic relationship.