[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Non-Dino Papers: Marine reptile bone histology, nocturnal Mesozoic mammals
From: Ben Creisler
A few recent non-dino papers and temporarily free articles that may be
Alexandra Houssaye (2012)
Bone histology of aquatic reptiles: what does it tell us about
secondary adaptation to an aquatic life?
Biological Journal of the Linnean Society (advance online publication)
Aquatic reptiles are very diversified in the fossil record. The
description and pooling of certain bone histological features
(collagenous weave and vascular network) of the various groups of
aquatic reptiles highlight what this histological information can tell
us about the process of secondary adaptation to an aquatic life.
Notably, they show the absence of interaction between these
histological features on the one hand and body size, mode of swimming,
type of microanatomical specialization and phylogeny on the other.
These histological features in aquatic reptiles seem to essentially
provide information about the growth rate and basal metabolic rate of
these taxa. The growth rate seems to have been rather high in most
marine reptiles, when compared with terrestrial ectotherms. Moreover,
distinct metabolic abilities are suggested. Indeed, various groups
probably displayed a peculiarly high body temperature, and some show
trends towards endothermy. This study also emphasizes the crucial need
for homologous comparisons in histology and shows that much remains to
be done to better understand the relationship between histological
features, growth rate and metabolism in extant taxa in order to make
inferences in the fossil groups.
Support of mainly nocturnal Mesozoic mammals (pdf is free)
Margaret I. Hall, Jason M. Kamilar and E. Christopher Kirk (2012)
Eye shape and the nocturnal bottleneck of mammals.
Proceedings of the Royal Society B (advance online publication)
Most vertebrate groups exhibit eye shapes that vary predictably with
activity pattern. Nocturnal vertebrates typically have large corneas
relative to eye size as an adaptation for increased visual
sensitivity. Conversely, diurnal vertebrates generally demonstrate
smaller corneas relative to eye size as an adaptation for increased
visual acuity. By contrast, several studies have concluded that many
mammals exhibit typical nocturnal eye shapes, regardless of activity
pattern. However, a recent study has argued that new statistical
methods allow eye shape to accurately predict activity patterns of
mammals, including cathemeral species (animals that are equally likely
to be awake and active at any time of day or night). Here, we conduct
a detailed analysis of eye shape and activity pattern in mammals,
using a broad comparative sample of 266 species. We find that the eye
shapes of cathemeral mammals completely overlap with nocturnal and
diurnal species. Additionally, most diurnal and cathemeral mammals
have eye shapes that are most similar to those of nocturnal birds and
lizards. The only mammalian clade that diverges from this pattern is
anthropoids, which have convergently evolved eye shapes similar to
those of diurnal birds and lizards. Our results provide additional
evidence for a nocturnal ‘bottleneck’ in the early evolution of crown
Springer journals Naturwissenschaften and Journal of Ornithology have
all content temporarily open access.
Also at the Springer site, papers from a conference "Messel and the
terrestrial Eocene" currently are posted in Palaeobiodiversity and
Palaeoenvironments in advance of publication with free pdfs.
Some may be of interest to the DML, in particular this paper about
animal locomotion for comparison with dinosaurs:
Holger Preuschoft and Jens Lorenz Franzen (2012)
Locomotion and biomechanics in Eocene mammals from Messel.
Palaeobiodiversity and Palaeoenvironments (advance online publication)
Eocene mammals from Grube Messel are divided into those that lived
terrestrially on the ground (2D-mammals) or arboreally (3D-mammals).
Their biomechanics and locomotion are discussed on the basis of equids
(Eurohippus, Propalaeotherium) and Leptictidium as examples of
2D-mammals and primates (Europolemur, Darwinius) of 3D-mammals. The
determining factor for lifestyle is the autopodia: 2D-mammals need
nothing more than compression-transmitting balls with reinforced
anterior margins (hooves). These autopodia do not require much energy,
but metapodia and even phalanges can elongate the functional length of
the free limbs. Primates as 3D-animals need prehensile hands and feet,
which can transmit tensile forces and even torques. Their metapodials
are part of the prehensile organ. Their strong and energy-requiring
musculature increases the masses on the distal limb segments and so
influences the locomotor modes.