Walshina, López-Torres & Silcox & Holroyd, 2018

López-Torres, Sergi, Silcox, Mary T. & Holroyd, Patricia A., 2018, New omomyoids (Euprimates, Mammalia) from the late Uintan of southern California, USA, and the question of the extinction of the Paromomyidae (Plesiadapiformes, Primates), Palaeontologia Electronica (37 A) 21 (3), pp. 1-28 : 11

PHYLOGENETIC RELATIONSHIPS OF WALSHINA GEN. NOV.

In order to assess the phylogenetic position of Walshina gen. nov. among Omomyoidea , we conducted a cladistic analysis based on the study by Ni et al. (2004), as modified by Holroyd and Strait (2008), who revised the coding for two species ( Purgatorius janisae and An. savagei ), and added new data for species of Loveina . We chose this particular matrix rather than more recent studies (e.g., Ni et al., 2013, 2016) because it includes a trogolemurin, Tr. myodes . Having coding from a member of this family available in the original matrix was important to ensure that we were assessing characters in the same way as the original authors. The analysis also includes representative tarsioids, anthropoids, adapoids, crown strepsirrhines, and plesiadapiforms. Scandentia was used as an outgroup to Primates . The rest of the trogolemurin primates were added to the matrix of Holroyd and Strait (2008): Tr. amplior , Tr. fragilis , Tr. leonardi , Sphacorhysis burntforkensis , W. esmaraldensis gen. et sp. nov., W. mcgrewi comb. nov., and W. shifrae comb. nov. The microchoerine Melaneremia bryanti (Hooker, 2007) , and the anaptomorphins An. sublettensis (Gazin, 1952, 1958), An. wortmani (Bown and Rose, 1984) , and An. natronensis (Beard et al., 1992) were added as well. The coding for Tr. myodes was partially reassessed, as was the one for Nannopithex sp. (to include generic variation seen in Na. zuccolae [Hooker, 2007]), and Scandentia was re-coded for character 13. A total of 303 characters (194 dental, 49 craniomandibular, 56 postcranial, and 4 soft tissue and physiological [only coded for extant taxa] characters) were scored for a total of 66 taxa (matrix available on publication from www.morphobank.org under project number P3264).

A parsimony analysis was performed using TNT v. 1.5 (Goboloff and Catalano, 2016) with all characters equally weighted and ordered, following the original analysis (Ni et al., 2004; Holroyd and Strait, 2008). Multiple character states were set to be interpreted as polymorphisms, instead of uncertainties. A traditional search was implemented with 1000 repetitions. The tree-bisection-reconnection (TBR) algorithm was used for branch swapping, with 1000 trees to save per replication.

Results of the Phylogenetic Analysis

The cladistic analysis yielded 90 equally parsimonious trees. A strict consensus tree was generated in TNT v. 1.5 from these trees ( Figure 7 , see also Appendix 2). In the strict consensus tree, Walshina gen. nov. is found to be monophyletic, although the relationships among species of Walshina gen. nov. remain unclear. The tribe Trogolemurini was also recovered as monophyletic.

The inclusion of the rest of trogolemurins and the four additional species of omomyoids, along with the revisions made by Holroyd and Strait (2008) and in the present paper, caused a few changes to the tree with respect to the topology found by Ni et al. (2004). The position of Purgatorius is resolved in our tree, being the sister group to the rest of Primates sensu lato. The rest of Plesiadapiformes (excluding Purgatorius ) form one clade, sister group of Altanius orlovi , as in Ni et al. (2004). However, phylogenetic analyses of plesiadapiforms with greater taxon sampling for that group support the interpretation that this group of primates is paraphyletic and excludes An. orlovi , which is interpreted as a euprimate (Silcox, 2001; Bloch and Boyer, 2002; Bloch et al., 2007, Silcox et al., 2010; Chester and Bloch, 2013; Chester et al., 2015; Ni et al. 2016). The tree differs from the results obtained by Ni et al. (2004) in resolving the position of Donrussellia as the sister taxon to the rest of Euprimates (except for Altanius ). Our tree also resolves Mahgarita and Rooneyia as sister taxa. Although Rooneyia has been considered an omomyoid, it appears as being part of the strepsirrhine radiation, as it did in Ni et al. (2004). All species of Teilhardina appear as basal haplorrhines, with unclear relationships among them. Eosimias appears in our tree as the sister taxon of crown haplorrhines (=Anthropoidea + Tarsius ). Washakiins are monophyletic, although Loveina was found to be paraphyletic (consistent with the results of Holroyd and Strait, 2008). Our tree also resolves a clade that includes omomyins and macrotarsiins, in which omomyins are paraphyletic. Washakiins are resolved as the sister group to a subgroup of anaptomorphins, which include Uintanius, Tetonius, Strigorhysis, Aycrossia, Anaptomorphus, and Absarokius. The rest of anaptomorphins ( Anemorhysis, Tetonoides, and Arapahovius ) form another clade that is the sister group of trogolemurins. However, Anemorhysis does not appear to be monophyletic. The sister group to the clade ( Trogolemurini + Anemorhysis + Tetonoides + Arapahovius ) is the Microchoerinae from Europe. The position of trogolemurins is, therefore, in contrast with their position in the tree found by Ni et al. (2004), in which Trogolemur clustered together with the European microchoerines. Finding trogolemurins to be more closely related to North American anaptomorphins, rather than to European microchoerids is more biogeographically parsimonious, reducing the number of implied dispersal events between North America and Europe.

Figures

FIGURE 7. Hypothesis of relationships of Walshina gen. nov. in the context of the Order Primates. Strict consensus cladogram based on data modified from Holroyd and Strait (2008), including the addition of seven newly-coded trogolemurins (Trogolemur amplior, Tr. fragilis, Tr. leonardi, Sphacorhysis burntforkensis, Walshina esmaraldensis gen. et sp. nov., W. mcgrewi comb. nov., and W. shifrae comb. nov.), a microchoerine (Melaneremia bryanti), and three anaptomorphins (Anemorhysis sublettensis, An. wortmani, and An. natronensis). Trogolemurins are marked in blue.