Craniodental characters and the relationships of Procyonidae (Mammalia: Carnivora) Author Ahrens, Heather E. text Zoological Journal of the Linnean Society 2012 2012-02-28 164 3 669 713 http://dx.doi.org/10.1111/j.1096-3642.2011.00778.x journal article 10.1111/j.1096-3642.2011.00778.x 0024-4082 5406828 APOMORPHIES OF PROCYONIDAE Neither previous morphological analysis attempted to identify features that distinguish procyonids from other carnivorans ( Decker & Wozencraft, 1991 ; Baskin, 2004 ). However, three possible apomorphies were suggested as diagnostic features of Procyonidae , including the presence of a squamosal epitympanic sinus, posterior orientation of the suprameatal fossa, and a distinctly bilobed baculum ( Decker & Wozencraft, 1991 ). The use of HRXCT to investigate internal anatomy has revealed that the epitympanic sinus is also present in Urocyon cinereoargenteus and Martes pennanti , and thus is not an unambiguous synapomorphy of Procyonidae . As I did not include postcranial material, I cannot assess the validity of a bilobed baculum as an apomorphy of Procyonidae . The suprameatal fossa was suggested as a distinctive characteristic of Procyonidae in many previous works (including Segall, 1943 ; Hough, 1948 ; Hunt, 1974 ; Tedford, 1976 ). However, Decker & Wozencraft (1991) identified the posterior orientation of the fossa as the important distinguishing feature of Procyonidae , whereas Schmidt-Kittler (1981) and Wolsan (1993) identified the dorsally expanded roof as the distinguishing feature. Here, the suprameatal fossa (24) is not optimized as a synapomorphy of Procyonidae because Ailurus fulgens is recovered within crown Procyonidae . The position of Ailurus fulgens requires a reversal from the typical procyonid condition to the primitive musteloid condition of a shallow suprameatal fossa (Schmidt- Kittler, 1981). Procyonidae is diagnosed (node 5, Fig. 35 ) by three synapomorphies in this analysis, including presence of an internal shelf on P4 (46), presence of a hypocone on P4 (46), and a hypoconulid present on m2 (76). The clade is not defined by any characters with a CI of 1.0; one character is also present in one outgroup and two are lost within the ingroup. The presence of an internal shelf on P4 was identified as an apomorphy of Procyoninae , which includes Broiliana plus New World procyonids ( Baskin, 2004 ). When excluding Old World procyonids, the internal shelf is recovered as a synapomorphy of Procyonidae . The presence of the hypocone on P4 was previously used to unite Procyonidae ( Mivart, 1885 ) , but the loss of the hypocone in the Potosinae ( sensu Decker & Wozencraft, 1991 ) and its absence in early Bassariscus spp. ( Baskin, 2004 ) suggest that the presence of the hypocone is relatively plastic and is not an ideal diagnostic character. Previously, a posteroexternal hypoconulid was considered primitive for procyonids ( Baskin, 2004 ). Here, the presence of a hypoconulid on m2 also unites Procyonidae , which is secondarily lost in Potos flavus . The loss of the m2 hypoconulid in Potos flavus represents one of many dental autapomorphies of the kinkajou within Procyonidae . Our limited understanding of the relationships within Musteloidea based on morphology warrants more focused studies on the evolutionary relationships of groups within Musteloidea and the evolution of morphological characters within those clades. Further investigation of the character evolution in procyonids, mephitids, mustelids, and Ailurus fulgens may help identify the ancestral morphological condition in each of these groups, and synapomorphies of these different groups.