*Feeding habits haven’t always been what they are today*
The feeding habits of mammals haven’t always been what they are today, particularly for omnivores.
Some groups of mammals almost exclusively eat meat–take lions and tigers and other big cats as examples.
Other mammals such as deer, cows and antelope are predominantly plant-eaters, living on a diet of leaves, shoots, fruits and bark. (more…)
Conventional wisdom holds that during the Mesozoic Era, mammals were small creatures that held on at life’s edges. But at least one mammal group, rodent-like creatures called multituberculates, actually flourished during the last 20 million years of the dinosaurs’ reign and survived their extinction 66 million years ago.
New research led by a University of Washington paleontologist suggests that the multituberculates did so well in part because they developed numerous tubercles (bumps, or cusps) on their back teeth that allowed them to feed largely on angiosperms, flowering plants that were just becoming commonplace. (more…)
*The hotter it gets, the smaller the animal?*
When Sifrhippus sandae, the earliest known horse, first appeared in the forests of North America more than 50 million years ago, it would not have been mistaken for a Clydesdale.
It weighed in at around 12 pounds–and it was destined to get much smaller over the ensuing millennia.
Sifrhippus lived during the Paleocene-Eocene Thermal Maximum (PETM), a 175,000-year interval of time some 56 million years ago in which average global temperatures rose by about 10 degrees Fahrenheit. (more…)
*Studies of diving beetles suggest sperm evolution may be driven by changes in female reproductive organs, challenging the paradigm of post-mating sexual selection being driven mostly by competition among sperm.*
Studying female reproductive tracts and sperm in diving beetles (Dytiscidae), researchers from the University of Arizona and Syracuse University have obtained a glimpse into a bizarre and amazing world of sperm that can take on a variety of forms – including joining together into conglomerates that navigate the twisted mazes of the female reproductive tract.
Analyses of the evolutionary relationships among diving beetles reveal that sperm form appears to follow function dictated by female reproductive organs. (more…)
