Angelone et al.—A new endemic leporid from the early Pleistocene of Sardinia


not undertake direct comparison with the BM of their forebears because, given the present state of the art, they are unknown or their postcranial material is not (well)-preserved. As for insular leporids, they also seem to increase their BMcompared to their continental ancestors, but in varying degrees. The western Mediterranean area offers some remarkable case studies. Nuralagus rex is considered the largest lagomorph ever with an averageBM~8250 g (see Quintana et al., 2011; Moncunill-Solé et al., 2015), whereas Hypolagus balearicus is quite small (BM: ~1300–2700 g, Quintana and Moncunill-Solé, 2014a). The average weight of the species described in this paper, Sardolagus obscurus n. gen. n. sp., is ~1650 g (i.e., similar to H. balearicus and the two extant insular leporids Nesolagus netscheri [Schlegel, 1880] [~1500 g; Sumatra Island] and Pen- talagus furnessi [Stone, 1900] [~2000–2800 g; Kawauchi, Sumiyo, Amami-Ohshima Island], Yamada and Cervantes, 2005). For the moment, it is not possible to undertake direct comparison with its ancestor (see above and below). Jointly with changes in BM, insular species endure other


biological adaptations (Van der Geer, 2014). Morphologically, insular lagomorphs are characterized by a stiff vertebral column, low sacropelvic angles, and other traits that enable a low gear locomotion (Yamada and Cervantes, 2005; Quintana et al., 2011). Moreover, several investigations have noticed that insular lago- morphs show a life history shift towards the slow end (Yamada and Cervantes, 2005; Riyahi et al., 2011; Köhler et al., 2015; Moncunill-Solé et al., 2016a). The material of Sardolagus obscurus n. gen. n. sp. is too poor and we can only make some preliminary inferences about its biology. The allometric analysis evidenced a large distal diameter of the humerus (high humeral epicondylar index). This trait is related with fossorial or burrower lifestyle (digging and scrabbling the ground, or digging holes for habitation) in both rodents (Samuels and van Valkenburgh, 2008) and lagomorphs (Reese et al., 2013). A large distal diameter of the humerus is also substantial in other extinct insular mammals (e.g.,N. rex and the rodents Hypnomys morpheus and Canariomys bravoi; see Bover et al., 2010; Quintana et al., 2011; Michaux et al., 2012; Quintana and Moncunill-Solé, 2014b). For the moment, the fossorial or burrower lifestyles of insular dwellers have been interpreted as the requirement of searching for alter- native food sources under the low-resource conditions of islands (Köhler, 2010). It is interesting to highlight that the analysis of teeth size,


particularly p3 measurements, is a very common methodology to compare fossil European leporids, due to the abundance of well-preserved dental remains with respect to jaws and postcranials. Such method must be carefully weighted as far as insular endemic lagomorphs are concerned, because of the higher allometric response of dental elements (and especially of the p3) to body size variations with respect to postcranials (Moncunill-Solé et al., 2015, 2016a, b). For this reason, all the procedures of BM estimations of Sardolagus obscurus n. gen. n. sp. were carried out with postcranial material.


Sardolagus in the context of European leporid record.—The appearance of stem Leporidae in Eurasia is a result of the late Miocene migration(s) from NorthAmerica via the northern land connection of Beringia (López Martínez, 2008; Flynn et al., 2014). The oldest record appears to be a species of Alilepus


517


(Čermák et al., 2015). Hypolagus is encountered in Eurasia somewhat later in the fossil record (Čermák, 2009). The rela- tively rapid spread of leporids across the Old World at ~8 Ma was an important Turolian event and is called the “Leporid Datum” (Flynn et al., 2014). The MN13 record of Leporidae in Europe is relatively rich and available throughout the continent in many localities, but already in the MN12 the record is rela- tively rare, and limited only to Leporinae. Only a few, very fragmentary findings, undoubtedly indicate the appearance of advanced leporids in Europe before MN12 (Flynn et al., 2014; Čermák et al., 2015). There are also a few, still questionable fossil occurrences suggesting that leporids were present in Europe prior to MN11. Nevertheless, in most cases the rela- tionship of such “early leporid findings” with the accompanying faunal assemblages is not clear or doubtful, making a further evaluation of their age and taxonomy necessary (see Flynn et al., 2014). It is particularly noteworthy that the leporid reports from Sansan (France, MN6, López Martínez, 2012) and Can Poncic (Spain, MN9; López Martínez, 1989) are distinctly anomalous in age. Such occurrences of relatively advanced leporids in the mid-Miocene are not fully compatible with present state of the art on evolution and paleobiogeography of Old World leporids and must be evaluated by future works. At any rate, this record pro tempore, suggests two possible hypotheses (Flynn et al., 2014): (Hh1) in the mid-Miocene of southwestern Europe some archaic lagomorphs could have developed some derived features typical of leporids independently to North American genera; and (Hh2) the “early European leporids” derive from a limited dispersal of leporids into Eurasia prior to the successful late Miocene influx (indeed, advanced leporids could have crossed Beringia before the late Miocene invasion [~8 Ma], leaving only a scattered record. As for the first hypothesis (Hh1), the relatively rich


Miocene record does not support evidence of the independent appearance in Europe of forms with “leporine” characters. The second hypothesis (Hh2) seems the more likely between the two. However, mammalian dispersals from North America into Eurasia were uncommon during Miocene compared to those in the opposite direction (Dawson, 1999), thus the migration of advanced leporids into Eurasia prior to the “Hipparion datum” (see Sen, 1989 for details) seems to be extremely improbable. More- over, the FADs of North American taxa phenotipically matching European ones (see Dawson, 1958, 2008; White, 1988, 1991; Voorhies and Timperley, 1997) do not fitinthismodel. The European record of Leporidae, including Archaeolaginae


and Leporinae subfamilies, comprises the seven genera listed below accompanied by their FADs in Europe: Alilepus—reliable from MN12 (Čermák et al., 2015); Hypolagus—reliable from MN13 (Averianov, 1996; Čermák, 2009);


Trischizolagus—reliable since MN14; the genus has been reported from ?MN13 (with PR0/A1/Pa0 morphotype), however the late Miocene appearance is very poorly recorded and still remains questionable (López Martínez et al., 2007; Čermák and Wagner, 2013);


Nuralagus—recorded from the early Pliocene type locality only (Quintana et al., 2011);


Pliopentalagus—exclusively limited to MN15, though known also from late MN13 in Eastern Asia (Tomida and Jin, 2009);


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192  |  Page 193  |  Page 194  |  Page 195  |  Page 196  |  Page 197  |  Page 198  |  Page 199  |  Page 200  |  Page 201  |  Page 202  |  Page 203  |  Page 204  |  Page 205  |  Page 206  |  Page 207  |  Page 208  |  Page 209  |  Page 210  |  Page 211  |  Page 212  |  Page 213  |  Page 214  |  Page 215  |  Page 216  |  Page 217  |  Page 218  |  Page 219  |  Page 220