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Crocodylian micro-sense-organs (free pdf) and fruit eating, plus other non-dino papers



From: Ben Creisler
bcreisler@gmail.com

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


Nicolas Di-Poï & Michel C, Milinkovitch (2013)
Crocodylians evolved scattered multi-sensory micro-organs.
EvoDevo (advance online publication)
DOI: 10.1186/2041-9139-4-19
http://link.springer.com/article/10.1186/2041-9139-4-19
Open Access!

Background
During their evolution towards a complete life cycle on land, stem
reptiles developed both an impermeable multi-layered keratinized
epidermis and skin appendages (scales) providing mechanical, thermal,
and chemical protection. Previous studies have demonstrated that,
despite the presence of a particularly armored skin, crocodylians have
exquisite mechanosensory abilities thanks to the presence of small
integumentary sensory organs (ISOs) distributed on postcranial and/or
cranial scales.

Results
Here, we analyze and compare the structure, innervation, embryonic
morphogenesis and sensory functions of postcranial, cranial, and
lingual sensory organs of the Nile crocodile (Crocodylus niloticus)
and the spectacled caiman (Caiman crocodilus). Our molecular analyses
indicate that sensory neurons of crocodylian ISOs express a large
repertoire of transduction channels involved in mechano-, thermo-, and
chemosensory functions, and our electrophysiological analyses confirm
that each ISO exhibits a combined sensitivity to mechanical, thermal
and pH stimuli (but not hyper-osmotic salinity), making them
remarkable multi-sensorial micro-organs with no equivalent in the
sensory systems of other vertebrate lineages. We also show that ISOs
all exhibit similar morphologies and modes of development, despite
forming at different stages of scale morphogenesis across the body.

Conclusions
The ancestral vertebrate diffused sensory system of the skin was
transformed in the crocodylian lineages into an array of discrete
multi-sensory micro-organs innervated by multiple pools of sensory
neurons. This discretization of skin sensory expression sites is
unique among vertebrates and allowed crocodylians to develop a
highly-armored, but very sensitive, skin.

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S. G. Platt, R. M. Elsey, H. Liu, T. R. Rainwater, J. C. Nifong, A. E.
Rosenblatt, M. R. Heithaus & F. J. Mazzotti (2013)
Frugivory and seed dispersal by crocodilians: an overlooked form of saurochory?
Journal of Zoology (advance online publication)
DOI: 10.1111/jzo.12052
http://onlinelibrary.wiley.com/doi/10.1111/jzo.12052/abstract

Saurochory (seed dispersal by reptiles) among crocodilians has largely
been ignored, probably because these reptiles are generally assumed to
be obligate carnivores incapable of digesting vegetable proteins and
polysaccharides. Herein we review the literature on crocodilian diet,
foraging ecology, digestive physiology and movement patterns, and
provide additional empirical data from recent dietary studies of
Alligator mississippiensis. We found evidence of frugivory in 13 of 18
(72.2%) species for which dietary information was available,
indicating this behavior is widespread among the Crocodylia.
Thirty-four families and 46 genera of plants were consumed by
crocodilians. Fruit types consumed by crocodilians varied widely; over
half (52.1%) were fleshy fruits. Some fruits are consumed as
gastroliths or ingested incidental to prey capture; however, there is
little doubt that on occasion, fruit is deliberately consumed, often
in large quantities. Sensory cues involved in crocodilian frugivory
are poorly understood, although airborne and waterborne cues as well
as surface disturbances seem important. Crocodilians likely accrue
nutritional benefits from frugivory and there are no a priori reasons
to assume otherwise. Ingested seeds are regurgitated, retained in the
stomach for indefinite and often lengthy periods, or passed through
the digestive tract and excreted in feces. Chemical and mechanical
scarification of seeds probably occurs in the stomach, but what
effects these processes have on seed viability remain unknown. Because
crocodilians have large territories and undertake lengthy movements,
seeds are likely transported well beyond the parent plant before being
voided. Little is known about the ultimate fate of seeds ingested by
crocodilians; however, deposition sites could prove suitable for seed
germination. Although there is no evidence for a crocodilian-specific
dispersal syndrome similar to that described for other reptiles, our
review strongly suggests that crocodilians function as effective
agents of seed dispersal. Crocodilian saurochory offers a fertile
ground for future research.

==

J. J. Liston & S. D. Chapman (2013)
Alfred Nicholson Leeds and the first fossil egg attributed to a ‘saurian’.
Historical Biology (advance online publication)
DOI:10.1080/08912963.2013.809575
http://www.tandfonline.com/doi/full/10.1080/08912963.2013.809575#.Ue9Lk421EYE

Discovered by the nineteenth century collector Alfred Nicholson Leeds,
the first object to be described (1898) as a fossil reptile egg is a
unique find from the Oxford Clay near Peterborough. It also comes from
one of a very small number of Jurassic localities worldwide that can
claim to have yielded a fossil egg. Given its historical and
contemporary significance, this object is reassessed in the light of
increased understanding of such objects. Data from scanning electron
microscopy, computerised tomography, synchrotron imaging, X-ray
diffraction and petrographic thin sectioning prove inconclusive.
However, the presence of apparent external openings resembling
angusticanaliculate pores – a pore type common only to certain types
of dinosaur eggshell – in both size and sparseness of distribution
prevents its summary dismissal as not being a dinosaurian egg.

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Borja Esteve-Altava, Jesús Marugán-Lobón, Héctor Botella & Diego
Rasskin-Gutman (2013)
Random Loss and Selective Fusion of Bones Originate Morphological
Complexity Trends in Tetrapod Skull Networks.
Evolutionary Biology (advance online publication)
DOI: 10.1007/s11692-013-9245-4
http://link.springer.com/article/10.1007/s11692-013-9245-4


The tetrapod skull has undergone a reduction in number of bones in all
major lineages since the origin of vertebrates, an evolutionary trend
known as Williston’s Law. Using connectivity relations between bones
as a proxy for morphological complexity we showed that this reduction
in number of bones generated an evolutionary trend toward more complex
skulls. This would imply that connectivity patterns among bones impose
structural constraints on bone loss and fusion that increase bone
burden due to the formation of new functional and developmental
dependencies; thus, the higher the number of connections, the higher
the burden. Here, we test this hypothesis by exploring plausible
evolutionary scenarios based on selective versus random processes of
bone loss and fusion. To do this, we have built a computational model
that reduces iteratively the number of bones by loss and fusion,
starting from hypothetical ancestral skulls represented as Gabriel
networks in which bones are nodes and suture connections are links.
Simulation results indicate that losses and fusions of bones affect
skull structure differently whether they target bones at random or
selectively depending on the number of bone connections. Our findings
support a mixed scenario for Williston’s Law: the random loss of
poorly connected bones and the selective fusion of the most connected
ones. This evolutionary scenario offers a new explanation for the
increase of morphological complexity in the tetrapod skull by
reduction of bones during development.

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