López-Torres and Silcox—European Paromomyidae


paromomyid to have ever been found in northwestern Europe. Hooker and Insole (1980) tentatively reported BMNH.M 44945 as pertaining to Phenacolemur cf. P. fuscus, making this specimen the first known representative of Arcius outside continental Europe. Since then, the specific classification of this specimen has been problematic; it has been suggested to pertain to either A. fuscus (Hooker, 1996, 1998) or A. lapparenti (Aumont, 2003, Hooker, 2010). Hooker (2010) noted that the English specimen has a smallM3 that falls within the size range of A. fuscus for that tooth. He also noted that the M2, although not strictly falling within the size range for that tooth reported by Aumont (2003, 2004), is closer in size to that of A. lapparenti than to that of A. fuscus. This suggests differences in terms of the relative proportions of these two teeth, but there are no speci- mens known for either A. lapparenti or A. fuscus in which the M2 and M3 are preserved in series to assess this possibility. Hooker (2010) also pointed out the presence of two entoconids on the M3, a trait never seen in paromomyids before. When considered alongside the contrasts newly noted here (listed in the diagnosis), it seems as though the best solution is to consider the English specimen to pertain to a new species. See also Table 2 for diagnostic comparisons.


Arcius ilerdensis new species Figure 9


2012 Arcius sp. Marigó et al. Holotype.—IPS 57510, right M2.


Diagnosis.—Larger M2 than A. rougieri, larger M2 than A. zbyszewskii, similar areas of M2 to A. hookeri n. sp., and smallerM2 than A. lapparenti. Absence of distal cingulid onM2, unlike A. fuscus, A. lapparenti, and A. rougieri. Differs from all other species of Arcius in lacking a buccal cingulid on M2 and having a short buccal cingulid on the M3 trigonid. Paraconid present on M2, but weakly expressed. Mesial inflection of the trigonid onM2 weaker than any other species of Arcius, with the trigonid being completely vertical. Differs from all other species of Arcius, except A. hookeri n. sp., in having a taller metaconid


929


than the protoconid on M2 and M3. Further differs from A. zbyszewskii in not having a paraconid on M3.


Horizon and locality.—Masia de l’Hereuet (MP10?), Lleida, Spain.


Biostratigraphy.—Marigó et al. (2012) described this site as MP8+ 9, but most genera found in Masia de l’Hereuet usually appear in younger deposits (e.g., Eogliravus, MP10-13 [Escarguel, 1999]; Lophiodon, MP 10 and later [Cuesta, 1994], although it is present but rare in MP8+9 [Checa, 1997]).


Description.—Arcius ilerdensis n. sp. is represented only by four isolated teeth: two left M2 (one of which is damaged; IPS57509), a right M2, a right M3. It shares with other Arcius species features such as taller cusps than in Ignacius, trigonids not as inclined as in other paromomyid genera, and the presence of a simple, rounded hypoconulid lobe on M3 (instead of the bilobed hypoconulid lobe seen in other paromomyids; Fig. 2). The M2 (IPS57508) has a strong postparacrista and pre- metacrista, with deep basins. A very small paraconule and metaconule are present, typical of paromomyids (Silcox and Gunnell, 2008). The distal margin of the tooth is straight, with a distolingual basin that is fairly expanded, but less so than in Phenacolemur, a typical Arcius trait. The buccal cingulum is broad. The parastylar region is expanded, forming a parastyle, but no metastyle is present. A precingulum is present, but short (Marigó et al., 2012). The M2 (IPS57510) exhibits a trigonid and talonid of similar width and a concave postvallid on the trigonid. The protoconid is lower than the metaconid, and the paraconid is reduced, as is typical of paromomyids (Silcox and Gunnell, 2008). On the talonid, the hypoconulid and the entoconid are poorly distinguishable (Marigó et al., 2012). The M3 (IPS57511) has a more buccally positioned cristid obliqua than on the M2, with more clearly demarcated entoconid and hypoconid (Marigó et al., 2012). It lacks a paraconid and has a very broad hypoconulid lobe, which are typical features of paromomyids (Silcox and Gunnell, 2008).


Table 2. Diagnostic characters for Arcius Godinot, 1984 species. Question marks indicate nonobservable characters. A. rougieri A. fuscus


Parastylar region on M1 Parastylar region on M3 Distolingual basin on M3


Highest cusp on I1 Anterocone Mediocone


Expanded buccally


Expanded buccally


Number of crests on the P4 postvallid 2 Mesial border of the P4 protoconid


Size of M1 paraconid


Stepped postvallid on M1 Metaconid/protoconid on M2 Paraconid on M3


Entoconid on M3


Slightly Medium


Cingulid on the buccodistal aspect ofM1-2 Present ?


Present


Mesial inflection of lower molars Highest point of the alveolar ridge


? ?


Weak


Between P4 andM1


A. lapparenti Mediocone


Not expanded Not expanded Not expanded Not expanded


Not expanded Expanded 3


concave


Concave Large


Absent Present


Protoconid taller than metaconid


Absent Simple


Somewhat expanded


2


Absent Present


Protoconid taller than metaconid


Absent Simple


Flat


A. zbyszewskii ?


? ?


A. hookeri ?


? ?


Somewhat expanded ? ?


Mostly straight ? Large


Small


Absent Absent ?


Present Simple


Somewhat weak Somewhat weak Somewhat weak ?


?


? ?


? ?


Absent


Metaconid taller than protoconid


Absent Double


A. ilerdensis ?


? ? ? ?


? ?


? Absent


Metaconid taller than protoconid


Absent Simple


Somewhat weak Very weak Flat


?


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