Gomphos, Oryctolagus and Ochotona

Ochotona princeps (originally Lepus dauuricus Pallas, 1776; Link 1795; Richardson 1828) is the extant pika, a rock-dwelling herbivore nesting between Henkelotherium and rabbits. Pikas live in mountainous areas in Asia and North America. Distinct from Henkelotherium, Ochotona is larger, with a near complete loss of the tail. Both have spreading metatarsals and four upper molars. In pikas the second incisors are posteromedial to the first incisors, creating a larger cheek area.

Fossil pikas are known from the Miocene, 16mya, to the recent, but Henkelotherium goes back to the Late Jurassic.

Gomphos elkema (Gervais 1877) Paleocene ~55 mya was described as the earliest and most complete ancestor to modern rabbits. Derived from a sister to Henkelotherium, and Plesiadapis, Gomphos phylogenetic preceded Oryctolagus, a living rabbit genus.

Distinct from Plesiadapis, the skull of Gomphos had a slightly downturned forehead and rostrum. Incisors 1 and 2 worked together against the lower two incisors. The jugal was more robust. A unique small process topped the orbit. The orbit was larger. The angular process of the mandible was large and descended with a large hook.

The forelimb and scapula were more gracile. The metacarpals were longer. The unguals were larger.

The ilium was longer. The femur was shorter and the tibia was both larger and longer. The foot was larger and longer with an elongated calcaneal heel.

Click here for Glires skulls compared.

Oryctolagus cuniculus (Linnaeus 1758) extant, is the modern European rabbit. It was derived from a sister to Gomphos.

Distinct from Gomphos, the skull of Oryctolagus had a longer rostrum, a larger orbit and a shorter postorbital region. The mandible was shallower anteriorly and deeper posteriorly. The ear opening was raised in a tube to the level of the cheekbone. The occiput angle was less vertical.

The cervicals were longer. The lumbars were longer and more robust. The sacrals and caudals were both shorter and the tail bones were vestigial beneath that bit of fluff. The rib cage was more gracile and slightly longer.

The scapula is triangular and the ventral portion has a small, sharp posterior process. The unguals were not as tall.

The pelvis was shorter, but the hind limb was virtually identical with the fibula fused to the tibia.

Asher RJ, Meng J, McKenna MC, Wible JR, Dashzeveg D, Rougier G, and Novacek MJ 2005. Stem Lagomorpha and the antiquity of Glires. Science 307:1091–1094.

Link HF 1795. Über die Lebenskräfte in naturhistorischer Rücksicht und die Classification der Säugthiere. - Beyträge zur Naturgeschichte (Rostock, Leipzig) 2: 1-41.

Meng et al. 2004. Gomphos elkema (Glires, Mammalia) from the Erlian Basin: Evidence for the Early Tertiary Bumbanian Land Mammal Age in Nei-Mongol, China. American Museum Novitates 3425: 1-24.

wiki/Oryctolagus
wiki/Gomphos
American Museum of Natural History/Gomphos
wiki/Pika