518


Journal of Paleontology 92(3):506–522


Oryctolagus—reliable from the early MN16 (López Martínez, 2008);


Lepus—reliable from the late MN17 (López Martínez, 2008).


Arrival of Sardolagus obscurus in Sardinia: an open issue.— Sardinian faunal assemblages were mainly the result of several migrations fromthe mainland. Early Eocene findings probably are continental endemic taxa whose differences from mainland ones were due to ecological (?filtering) barriers (Kotsakis, 1986, p. 28; reprised in Palombo, 2009, p. 379). Evidence of a late Oligocene migration from the mainland can be recognized in Corsica (Ferrandini et al., 2000), but not in Sardinia, due to the lack of fossil evidence. In Sardinia, the first known migration should have occurred ~20 Ma (MN3), based on the study of the vertebrates from Oschiri (Van der Made, 2008). It must be noted though that the assemblage from Oschiri includes elements of multiple migrations and, very likely, elements that could have been pas- sively transported (e.g., the talpids, De Bruijn and Rümke, 1974) during rotation of the plate. According to Van der Made (2008), the next immigration recorded in Sardinian territory should have occurred ~11 Ma, correlating with a pronounced regression. Other immigrations possibly occurred during the several middle Miocene marine lowstands, however the hiatus in the Sardinian mammalian fossil record between ~20–11 Ma prevents a ver- ification of this possibility (Van der Made, 2008). An earliest late Miocene immigration is recorded by the fossil assemblages refer- able to the Tusco-Sardinian paleobioprovince, including territories today corresponding to Sardinia and part of Tuscany. The Tusco-Sardinian paleobioprovince remained isolated until the Messinian, apart from some occasional arrivals from the mainland. Several arrivals are recorded in the Baccinello-Cinigiano Basin between 8.3 Ma and 6.7 Ma (Rook et al., 2011; Benvenuti et al., 2015). According to Van der Made (2008), the migrational wave that occurred at ~8 Ma was of particular importance. Because the Tusco-Sardinian PB probably was fragmented in an archipelago (Engesser, 1989), inputs from the mainland did not always reach all the islands, especially the territories corresponding to modern Sardinia (see also Casanovas-Vilar et al., 2011). During the Mes- sinian, Tuscany connected to Italianmainland; in fact, the endemic insular species gave way to continental species, although the region maintained some degree of continental isolation, as demonstrated by the presence of new endemic non-insular species (Angelone and Rook, 2011 and references therein). Sardinia received a wave of continental immigrants during the Messinian and during the early/late Pliocene transition (Angelone and Kotsakis, 2001; Angelone et al., 2015). Later migrations are hypothesized by Palombo (2009) to have occurred during the Piacenzian regressive phase (~2.9 Ma) and at the end of the Gelasian (possibly ~2.1 Ma; extrapolated from Palombo, 2009, p. 369, fig. 2). The first reports of the canid Cynotherium at ~1.2Macome out in favor of the presence of a landbridge between Sardinia and mainland due to the ecological requirement of carnivorans. Other mammals appear in Sardinia together with or sligthly after Cynotherium, reinforcing the evidence of a migrational wave from the mainland. The arrival of Mammuthus lamarmorai (Forsyth-Major, 1883), which occurred at the end of the Middle Pleistocene, probably did not require a fully emerged land connection. Indeed, M. lamarmorai is the only “foreign” terrestrial taxon that appears in Sardinia in that


period (the other new occurrences are lutrins; Palombo and Rozzi, 2014). Lagomorphs need a landbridge to reach isolated domains


(Angelone, 2007). There is no trace of leporids in Sardinia before Leporidae indet. from Capo Mannu D1, however this does not exclude their presence. In the improbable hypothesis that Sardolagus n. gen. is related to pre-Turolian leporids, the ~11Ma regression could be the moment of its immigration. If we relate instead Sardolagus n. gen. to modern leporids (which appeared in Europe ~8 Ma; Flynn et al., 2014), we could link the arrival in Sardinia of its ancestor to one of the following.


(1) The major migration episode reported at ~8 Ma (Van der Made, 2008). However, in the Turolian Tusco-Sardinian paleobioprovince, lagomorphs seem completely missing from the Sardinian record (i.e., Fiume Santo; Casanovas- Vilar et al., 2011) and the Tuscanian record is monopolized by Paludotona.


(2) The Messinian desiccation of the Mediterranean. It is common opinion that the endemized taxa present in the earliest late Pliocene assemblage of Capo Mannu D1 (the murid Apodemus mannu and the glirid Tyrrhenoglis aff. T. figariensis), could have arrived during the Messinian (Angelone and Kotsakis, 2001 and references therein). In this case, a relationship of Sardolagus n. gen. with European continental Alilepus (whose record is proven since MN12) or Hypolagus (proven since MN13) or a taxon closely related to Oryctolagus stock (the first record of Oryctolagus is at ~3.5; López Martínez, 2008) could be invoked.Afavored migration path could have been through the Italian peninsula, whose Messinian record accounts for some leporids (Alilepus meini and the leporid from Brisighella provisionally classified as Trischizolagus cf. maritsae), which could represent the source of Sardolagus n. gen. However, PR1 and PR2 p3 patterns, typical of Trischizolagus, are completely lacking in the sample of Sardolagus n. gen., thus excluding any close affinity to typical Trischizolagus, which also has a more advanced and more variable P2.


(3) The early–late Pliocene regression (~3.6 Ma, age of Capo Mannu D1 assemblage, in which a leporid is recorded). Sardolagus n. gen. ancestor could have colonized Sardinia together with the ochotonid Prolagus sorbinii Masini, 1989 from mainland Italy (Angelone et al., 2015). The Capo Mannu D1 leporid does not provide any additional weight to this hypothesis, being a sole, broken, non-diagnostic tooth. Nevertheless, though not strictly testable, a direct relationship between Leporidae indet. from Capo Mannu D1 and Sardolagus n. gen. is the most parsimonious hypothesis. From the taxonomic perspective discussed above, the most probable continental ancestor in this case should be sought among the earliest forms or an ancestral stock of Oryctolagus, whose first appearance should be at ~3.5 Ma (López Martínez, 2008). In this case, the evolutionary scenario would imply a reversal of morpho- clines.


Considering the phylogenetic relationship between


Leporidae indet. from Capo Mannu D1 and Sardolagus n. gen. as the most probable scenario, we consider extremely unlikely


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