Oligocene White River fossil Rabbit skull Paleolagus haydeni Wyoming

Description

A fossil rabbit skull,
Paleolagus haydeni
, from the Oligocene White River deposits of Converse County, Wyoming.
The specimen consists of the skull, both jaws, and is 2” long.
The specimen has been consolidated with glue and no restoration has been performed.
The left side of the specimen is nicely preserved with nasals, fenestra (thin lacey bone covering the facial vacuity in front of the orbit) and zygomatic arch.
The right side of the skull was exposed to weathering before discovery and is missing the zygomatic arch.
Both sides are missing the incisors.
The cranium is preserved without the occipital plate or auditory bullae.
Rabbits are in the Order Lagomorpha and Family Leporidae.
The only other family of lagomorphs is Ochotonidae, the pikas.
Rabbits and pikas are not rodents, but Lagomorpha is closely related to the Order Rodentia.
Palaeolagus
was a primitive rabbit and was built more like a pika.
Palaeolagus
had some of the typical rabbit features but did not have large eyes or saltatorial adaptations.
When it ran for its burrow, it scampered like a pika or rat.
It was the size of a cottontail, and its fossils, particularly its teeth, are one of the most common mammal fossils found in White River rock layers.
At the start of the Oligocene (Orellan), rabbits and rodents became important in mammal communities across the Northern Hemisphere.
Lagomorphs are an evolutionarily conservative group --their body plans and lifestyles have changed little since they first evolved.
Palaeolagus
had large middle ear cavities and facial vacuities similar to leptauchenin oreodonts.
The holes in the snout were covered with soft tissue when it was alive and may have acted as shock absorbers for chewing vibrations traveling through the dense skull bone towards the middle ear.
Dampening chewing noise before it reached the middle ear cavities may have improved its ability to hear predators sneaking up.
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This fossil was collected and/or obtained legally and is being sold legally.