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Angel Brown
Angel Brown

Animus Rar

Raranimus is an extinct genus of therapsids of the Middle Permian. It was described in 2009 from a partial skull found in 1998 from the Dashankou locality of the Qingtoushan Formation, outcropping in the Qilian Mountains of Gansu, China. The genus is the most basal known member of the clade Therapsida, to which the later Mammalia belong.[1]

Animus rar

According to a phylogenetic analysis conducted along with its initial description, Raranimus is considered to be the basalmost therapsid.[1] There has been some controversy as to whether Tetraceratops is a therapsid or a more basal pelycosaur. If Tetraceratops is a therapsid, as has recently been proposed, it would be the oldest and most basal one known, surpassing Raranimus in age by several million years.[3] However, later studies have questioned the placement of Tetraceratops within Therapsida, and the 2009 phylogenetic analysis using Raranimus places the genus outside of the clade.[1][4][5]

With the general absence of therapsid remains from Olson's Extinction, different hypotheses have developed in order to explain the group's origins and initial diversification. One theory suggests that therapsids diversified quickly through rapid apomorphy accumulation sometime during the gap, while the other proposes that therapsids evolved gradually over the course of up to 35 Ma.[7][10] Only recently have remains of basal therapsids such as Raranimus been found from China that occur during Olson's Extinction. Other therapsids that are known to have existed during the gap include Sinophoneus and Stenocybus.[11]

However, I recently came across the Early Permian Stereophallodon (Brinkman and Eberth 1986), described as a basal ophiacodontid with double canines. That made me think about Raranimus, described as a basal therapsid with double canines. Here (Fig. 1) they are together for the first time.

Stereophallodon (Earliest Permian) was described by Brinkman and Eberth (1986) as an ophiacodontid more primitive than Ophiacodon (Fig. 2), a taxon nesting at the base of the Therapsida in the large reptile tree. Raranimus (Early Middle Permian) was described by Liu, Rubidge and Li (2009) as a basal therapsid. Funny, they both had double canines, a trait not present in other basal therapsids, or ophiacodontids. 041b061a72


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