Dr. June Liu, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, and his collaborators, recently describe a new large predatory synapsid, Raranimus dashankouensis gen. et sp. nov., from the Middle Permian of Dashankou in China which has a unique combination of therapsid and sphenacodontid features.

The Middle Permian Dashankou fauna from Gansu Province, China is known to have produced a wide variety of basal tetrapod fossils (Battail 2000; Li 2001). This specimen, comprising the partial snout of a tetrapod, was discovered at the Dashankou locality and contributes to the diversity of this fauna. Although fragmentary, the fossil reveals a unique combination of therapsid and sphenacodontid features. This find helps us understand the morphological transition from sphenacodonts to therapsids and provides new insight into the long−standing debate on whether basal therapsids had a Laurasian or Gondwanan origin.

The distant evolutionary ancestry of mammals is documented by a rich therapsid fossil record. While sphenacodontid synapsids are considered the sister−group of therapsids, the place of origin of therapsids is an enigma, largely because of a long standing morphological and temporal gap (Olson’s Gap) in their fossil record. This specimen is of great significance as it is a basal therapsid which is the sister taxon to all other therapsids. The fact that it was found in association with Early Permian tetrapods (Anakamacops and Belebey) suggests that it is the oldest therapsid and provides the first evidence of therapsid−bearing rocks which cover Olson’s Gap. It further supports that therapsids may have had a Laurasian rather than Gondwanan origin.

The original paper was published in Acta Palaeontol. Pol. 54 (3): 393–400, 2009