Saturday, 9 July 2016
This wee skull of a Microtheriomys brevirhinus from the John Day Formation is an adorable 19 mm. Yeah, he's pretty cute!
Paleontologists Dr William Korth of Rochester Institute of Vertebrate Paleontology and Dr Joshua Samuels of John Day Fossil Beds National Monument are pretty chuffed about some new fossil finds. They have described four new genera and ten new species of prehistoric rodents that lived in what is now Oregon during the Oligocene -- 30- 22 million years ago.
The newly-discovered genera include this wee fellow, the early beaver, Microtheriomys brevirhinus, a dwarf tree squirrel, Miosciurus covensis, a primitive pocket mouse, Bursagnathus aterosseusm the birch mouse Plesiosminthus fremdi, an early relative of beavers, Allotypomys pictus along with bits and pieces of Proapeomys condoni; Apeomys whistleri; Neoadjidaumo arctozophus, Proheteromys latidens & Trogomys oregonensis.
Of these ten new species, four represent completely new genera: Allotypomys, Microtheriomys, Proapeomys, and Bursagnathus.
“This study fills some substantial gaps in our knowledge of past faunas, specifically smaller mammals,” said Dr Samuels, who is a co-author of the paper published in the Annals of Carnegie Museum. “Some of the new species are really interesting in their own right, and will ultimately help improve our understanding of the evolution of beavers and pocket mice.” The new rodents were collected through decades of collaborative work throughout the John Day Formation, Oregon.
Saturday, 2 July 2016
Radiolarians are unicellulars, wee little things with a diameter of 0.1–0.2 mm.
They produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm.Their beautifully elaborate mineral skeletons are usually made of silica. We find radiolaria as zooplankton throughout the ocean and their skeletal remains make up a large part of the cover of the ocean floor as siliceous ooze.
Due to their rapid turnover of species, they represent an important diagnostic fossil from the Cambrian onwards. Because they occur in continuous and well-dated sequences of rock, they act like a yardstick, helping geologists accurately date rock from around the globe.
In the Upper Triassic rocks, which predate the Triassic / Jurassic Mass Extinction event by about 10 million years, radiolarians are preserved in hundreds of forms. Just above them, in the early Jurassic rock layers laid down about the time of the great die-offs, only a fraction of the previous number of forms are represented. The more recent Jurassic rock shows a rebound of radiolarian diversity, though of course, in different forms, a diversity which continues to flourish and expand in today’s oceans.