930


Journal of Paleontology 92(5):920–937


uncommon among Arcius that the metaconid is clearly taller than the protoconid in lower molars, a feature also seen in A. hookeri n. sp. The lack of a distal cingulid on the buccal half of the distal aspect of the M1-2 also contrasts with the more derived members of the genus (A. fuscus, A. lapparenti, and A. rougieri), suggesting that A. ilerdensis still retains somewhat primitive characters in the Arcius lineage.


Phylogenetic relationships of Arcius


To assess the phylogenetic relationships among the different species of Arcius, and the position of the genus among Paromomyidae,we conducted a cladistic analysis.Acharacter list was created to assess specifically the relationships of Arcius based on character diagnoses from Matthew (1915), Gidley (1923), Russell et al. (1967), Rose and Bown (1982), Godinot (1984), Robinson and Ivy (1994), Estravís (2000), Bloch et al. (2002), Silcox et al. (2008), and Fox et al. (2010) (Table 3). Some of the characters that relate to higher-level relationships among plesia- dapiforms were taken from Silcox’s (2001) matrix for plesiada- piforms. The primitive purgatoriid Purgatorius coracis Fox and Scott, 2011 was chosen as the outgroup for Paromomyidae. The analysis also includes the oldest and most primitive members of every paromomyid genus: Paromomys farrandi, Edworthia lerbekmoi Fox et al., 2010, Phenacolemur archus Secord, 2008, Acidomomys hebeticus,and Ignacius fremontensis Gazin, 1971. The genus Elwynella, which includes only the species Elwynella oreas Rose and Bown, 1982, was excluded from this analysis because it is themost recent genus of paromomyid to appear in the fossil record, and although it exhibits the primitive character of retention of a P3, it sharesmany derivedmolar characters found in the late Wasatchian paromomyid Phenacolemur jepseni,which suggests that it may be nested within a higher-level grouping of paromomyids. A total of 53 dental characters were scored for 13 taxa (Table 3; matrix available on publication from the Dryad Digital Repository; see also Supplemental Data 2). The parsimony analyses were performed using TNT


Figure 9. Micro-CT scan images of Arcius ilerdensis n. sp. (1) IPS 57508, left M2, occlusal view; (2) IPS 57510, lower right M2, holotype, occlusal view; (3) IPS 57511, rightM3, occlusal view. Scale bar=1 mm..


Etymology.—From the Latin Ilerda (ancient name of the city of Lleida), in allusion to its province of origin.


Materials.—IPS 57508, left M2; IPS 57511, right M3.


Remarks.—The Masia de l’Hereuet specimens were described by Marigó et al. (2012) as members of the genus Arcius, but those authors did not give them a specific ascription due to the scarcity of the material. Although we agree with Marigó et al. (2012) that it would be beneficial for more fossils to be recovered from that site, the few fossils known show enough distinctive traits to be discerned from other species. Lower molars of paromomyid species that do not belong to


the genus Arcius have trigonids that are strongly mesially inflected, while Arcius shows weak levels of inflection. However, Arcius ilerdensis has a uniquely vertical trigonid, even relative to other members of the genus. It is also


(Goloboff et al., 2008) with all characters equally weighted. Four of the 53 characters (1, 8, 13, and 39) were ordered, and the rest were left unordered. A heuristic search was implemented with 1,000 repetitions, with 1,000 trees saved per replication. Five cladistics analyses were run: (1) a basic analysis that excluded the poorly sampled taxa from Abbey Wood (UK), Sotteville-sur-Mer (France), and Masia de l’Hereuet (Spain); (2) an analysis that included the Arcius from Abbey Wood; (3) an analysis that included the Arcius from Sotteville-sur-Mer; (4) an analysis that included the Arcius from Masia de l’Hereuet; and (5) an analysis that included all European paromomyid taxa. Analysis 1 is meant to give a general understanding of the relationships of Arcius based on the well-preserved species, whereas analyses 2, 3, and 4 are meant to accurately place the poorly sampled taxa. Analysis 5 is also meant to give a general understanding of the relationships of the genus but including all taxa (both well and poorly sampled). Analyses 1, 2, and 3 yielded only one unequivocal tree each (Fig. 10.1–10.3). Analysis 4 yielded 6 equally parsimonious trees. A strict con- sensus tree was generated in TNT from these trees (Fig. 10.4). Analysis 5 also yielded 6 equally parsimonious trees, and a strict consensus tree was generated in TNT (Fig. 11).


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