BACKGROUND More than 30 different lineages of amphibians, reptiles, birds, and
mammals have independently invaded oceans ecosystems. Prominent examples include …

The neck is a critical portion of the avian spine, one that works in tandem with the beak to act
as a surrogate forelimb and allows birds to manipulate their surroundings despite the lack of …

Dating the tree of life is a core endeavor in evolutionary biology. Rates of evolution are
fundamental to nearly every evolutionary model and process. Rates need dates. There is …

The ecological origin of snakes remains amongst the most controversial topics in evolution,
with three competing hypotheses: fossorial; marine; or terrestrial. Here we use a geometric …

Hox genes regulate regionalization of the axial skeleton in vertebrates,,,,,,, and changes in
their expression have been proposed to be a fundamental mechanism driving the evolution …

A unique characteristic of mammals is a vertebral column with anatomically distinct regions,
but when and how this trait evolved remains unknown. We reconstructed vertebral regions …

The incompleteness of the fossil record obscures the origin of many of the more derived
clades of vertebrates. One such group is the Ichthyopterygia, a clade of obligatory marine …

The origin of the turtle shell has perplexed biologists for more than two centuries [1]. It was
not until Odontochelys semitestacea [2] was discovered, however, that the fossil and …

Complexity, defined as the number of parts and their degree of differentiation, is a poorly
explored aspect of macroevolutionary dynamics. The maximum anatomical complexity of …

Mammals show a very low level of variation in vertebral count, particularly in the neck.
Phenotypes exhibited at various stages during the development of the axial skeleton may …