Hypolagus vetus

Overview

Hypolagus vetus is an ancient rabbit from western North America. Its lower jaws, skulls, and small teeth have been studied. Patterns on teeth just a few millimeters across help researchers identify and map the distribution of this extinct rabbit.^[1]

Key facts

Even teeth of the same species can look different in shape and size depending on wear. A 2011 study compared wear and chewing surfaces on two premolars. The depth and direction of small grooves helped distinguish similar rabbits.^[1]

Time and place

The material comes from western North America in the later Cenozoic, millions of years ago. The lower jaw on which the name was based came from the Thousand Creek beds in present-day Nevada, USA. Jaws and teeth from other sites are compared with this reference material.^[1][2]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

The genus Hypolagus is described as a group of medium-sized to large rabbits with a shortened gap between the incisors and cheek teeth. Material of H. vetus includes lower jaws, partial skulls, premolars, and postcranial bones. The groove pattern of the third lower premolar is a particularly important comparative feature.^[1][2]

One study estimated its body mass at approximately 2.9 kg. This offers a way to imagine a fossil rabbit often encountered only through tiny teeth as an animal weighing several kilograms.^[3]

Habitat and reproduction

It is compared with other members of the plant-eating order Lagomorpha. As teeth wear through chewing, their surface patterns and dimensions change. Traces of tooth use can therefore help researchers study the lives of ancient rabbits.^[1]

Fossil discovery

The species was described in 1910 as Lepus vetus and later became the type species of Hypolagus. A 2011 study compared newly examined lower jaws and teeth with material from the type locality in Nevada. Patterns on small premolars helped identify the same species at distant sites.^[1][2]

References

1. 2011 study — Strata and mammal fossils of the Horned Toad Hills
2. Fostowicz-Frelik2003 — Classification and characteristics of the genus Hypolagus
3. Smits (2017), Remodeling the Fossil Record: Analysis of Emergent Evolutionary and Ecological Patterns
4. 2021 study — The skull of Palaeolagus examined with CT

Research questions

How can differences caused by tooth wear be distinguished from differences between species? Researchers compared tooth dimensions, grooves, and stages of wear together. Even tiny teeth can reveal questions about both growth and classification.^[1]

Observation

Picture the gap between the teeth in the jaw and the chewing surfaces of the premolars. Notice how the depths and directions of their grooves provide clues for comparing ancient rabbits.^[1][2]