934


Journal of Paleontology 92(5):920–937


which is inferred to be of nearly equivalent age to Sotteville-sur- Mer (i.e., PE II according to Hooker, 2015) and is quite distant in space. Iberia was isolated from continental Europe by the Carcassonne Strait already by the earliest Eocene (Marandat et al., 2012), and the intercontinental dispersal of paromomyids is argued to have occurred during thePETM(Hooker, 2015), making the dispersal of A. zbyszewskii into southwestern Europe rather difficult. However, other sources (Plaziat, 1981; Badiola et al., 2009) illustrate a land connection between Iberia and continental Europe during the early Eocene, suggesting that faunal dispersal from continental Europe into Iberia might have been possible by the earliest Eocene. In any case, the broad biogeographic range of Arcius zbyszewskii across western Europe suggests that this species might have undergone rapid dispersal across the continent in a short period of time. Even if the fossils from Silveirinha and Normandy did not belong to the same species, it would be one of the first cases of finding similar species in northern and southern Europe, which goes against the strong trend of north–south regionalism in this continent (Marandat, 1997). In terms of the origins of Arcius, the phylogenetic results


Figure 12. Paleogeography of Western Europe and Greenland during the earliest Eocene and location of some selected paromomyid-bearing locations (modified from Eberle and Greenwood, 2012, fig. 3; Marandat et al., 2012, fig. 1; and Hooker, 2015, fig. 8). (1) Eureka Sound Group, Canada; (2) Abbey Wood, UK; (3) Sotteville-sur-mer, France; (4) Paris Basin, France; (5) Palette, France; (6) Masia de l’Hereuet, Spain; (7) Silveirinha, Portugal.


However, to assess this question more fully, additional North American paromomyid species should be included in the analysis of the family.


Biogeographic implications.—The results of the phylogenetic analyses, which consistently support the monophyly of Arcius, would suggest that there was only one dispersal event of paromomyids between North America and Europe. This dis- persal would have been possible through land bridges between North America and Europe. The volcanic activity and regional uplift in eastern Greenland closed the Greenland Strait (or Denmark Strait) between Europe and Greenland, making it much narrower during the Paleocene and Eocene (Knox, 1998). In addition, the English Channel was bridged, allowing dispersal between the British Isles and continental Europe, and in particular with France (King, 2006). One of the oldest occurrences of Arcius comes from the site


of Sotteville-sur-Mer in Normandy, France. That region of Normandy could have been the entry point to continental Europe from the Greenland land bridge (Fig. 12), which would be consistent with finding the oldest representative of the genus in that area. However, Arcius zbyszewskii is also found at Silveirinha,


unequivocally support the existence of a long ghost lineage. The oldest member of the Phenacolemur-Ignacius-Acidomomys clade is Ignacius cf. I. fremontensis from Torrejonian 2 (To2; Rose, 1981;Silcox and Williamson, 2012).Therefore, the Arcius lineage is inferred to have branched off prior to To2. The absence of Arcius-like species in the well-sampled western North American record during the Torrejonian, Tiffanian, and Clarkforkian suggests that the evolution of this lineage might have happened inmore northern latitudes and closer to the land bridges thatwould later connect North America with Europe. In fact, undescribed Ignacius-like paromomyids have been reported from the Eocene of Ellesmere Island, in the Canadian Arctic (West and Dawson, 1977; Eberle and Greenwood, 2012), hinting at the potential of this region, and of other areas in the Greenland land bridge (e.g., the east coast of Greenland; Larsen et al., 2001, 2002), to rewrite our understanding of paromomyid evolution and biogeography.


Conclusions


A new revision of the paromomyids from Europe (after Aumont, 2004) prompts the rediagnosis of the genus Arcius based on a significant collection of previously unpublished material, redefining Arcius fuscus and Arcius lapparenti after identifying the mix of specimens in the original taxonomic study by Russell et al. (1967), and the description of two new species: Arcius hookeri n. sp. and Arcius ilerdensis n. sp. Our phylogenetic analysis shows that Arcius is mono-


phyletic. This is consistent with previous work done by Aumont (2003) but differs from her results in the precise relationships among species of Arcius. Our tree suggests that Arcius zbyszewskii is the most basal species of Arcius, in line with Estravís’s (2000) inferences. Our results further differ from Aumont’s (2003) in finding the clade Phenacolemur-Ignacius- Acidomomys as the sister clade to the European paromomyids, instead of just Acidomomys. When the more fragmentary taxa were added to the phylogenetic analysis, the results are consistent with the inference that the Normandy specimen belongs to Arcius zbyszewskii and that Arcius hookeri belongs to an independent lineage. The phylogenetic relationships of


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