The dwarf elephant Palaeoloxodon mnaidriensis from Puntali Cave, Carini (Sicily; late Middle Pleistocene): Anatomy, systematics and phylogenetic relationships

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Abstract

The Pleistocene fauna of Sicily includes two endemic elephant taxa of different body sizes: the dwarf Palaeoloxodon falconeri and the medium-sized Palaeoloxodon mnaidriensis. P. mnaidriensis is the younger of the two elephant taxa and occurs in faunal assemblages dated from the late Middle to the late Pleistocene. This paper presents a systematic and morphometric study of P. mnaidriensis based on material from the late Middle Pleistocene Puntali Cave (Carini), representing the largest and best preserved sample of this taxon.

The morphological revision supports the hypothesis that P. mnaidriensis from Sicily is indeed a separate species with respect to mainland Palaeoloxodon antiquus and not just a smaller insular form of the latter. P. mnaidriensis from Puntali Cave has a mean estimated shoulder height of about 1.8 m and a mean body weight of about 1100 kg, representing a body mass reduction of nearly 90% with respect to the ancestral form. The observed morphological differences between P. mnaidriensis and P. antiquus are in part related to dwarfing but also suggest a different ecological adaptation of the insular form. The grouping of P. mnaidriensis with Palaeoloxodon recki atavus, Palaeoloxodon recki recki, Palaeoloxodon naumanni, P. antiquus and Palaeoloxodon namadicus in the monophyletic genus Palaeoloxodon is supported by three cranial synapomorphies.

Introduction

Dwarf elephants are among the most emblematic components of the Pleistocene endemic faunas of the Mediterranean insular area (Palombo, 2004). On some islands (e.g., Sicily, Malta, Crete), more than one elephant species, showing various degrees of body-size reduction, have been described. They are of interest for their biochronological and paleobiogeographical significance and also because their rich fossil record allows for a thorough study of the so-called “island rule” (i.e., insular dwarfing) in large mammalian herbivores (Foster, 1964; Palombo, 2001, Palombo, 2007; Raia et al., 2003). The fossil fauna of Sicily includes at least two elephant species, representing two successive Palaeoloxodon colonizations of the island: the dwarf Palaeoloxodon falconeri Busk and the medium-sized Palaeoloxodon mnaidriensis Adams (Palombo and Ferretti, 2005). P. mnaidriensis is the younger of the two species and occurs in faunal assemblages dated from the late Middle to the late Pleistocene (Bonfiglio et al., 2002). Isolated remains of a large-sized elephant were retrieved from Via Libertà at Palermo, within shallow marine sediments dated to the Middle Pleistocene (Fabiani, 1932; Bonfiglio and Insacco, 1992). The elephant from Via Libertà was referred by Aguirre (1969) to a new endemic subspecies of the straight-tusked elephant, Palaeoloxodon antiquus leonardii, characterized by a moderate body-size reduction with respect to the mainland form. However, the validity of this taxon has been questioned by some authors, arguing that the Via Libertà remains may actually represent very large (male) individuals of P. mnaidriensis (Burgio, 1999; Chilardi, 2001). Further revision of the Via Libertà elephant is needed in order to resolve this problem.

The fossil remains from the Puntali Cave, near Carini (Fig. 1), represent the largest and best preserved sample of P. mnaidriensis. The site was excavated by G.G. Gemmellaro between 1868 and 1870 resulting in a large collection of elephant remains, including complete skulls and isolated postcranials, most of which are stored in the Museo di Paleontologia of the University of Palermo (Burgio et al., 1983). Part of the Gemmellaro collection was described by Pohlig (1893), Vaufrey (1929) and Ambrosetti (1968). Piccoli et al. (1970) provided additional information on the anatomy of the skull of the elephant from the Puntali Cave based on material acquired by the Museum of Paleontology of the University of Padova. Since the Piccoli et al. monograph, there has been no further detailed study on the skeletal anatomy of P. mnaidriensis. Moreover, the Gemmellaro collection at Palermo was never described and illustrated in its entirety. It is the aim of this paper to present a new description and comparison of the osteology of P. mnaidriensis from Puntali Cave in order to highlight the systematic and phylogenetic information of this material, with a special emphasis on cranial features. The results allow a revision of the skeletal characters of the Eurasian Palaeoloxodon species.

Section snippets

Institutional abbreviations

These abbreviations refer to institutions in which specimens studied in this work are housed: IAM, Ice Age Museum, Moscow; IGF, Museo di Storia Naturale di Firenze, Sezione di Geologia e Paleontologia; LBM, Lake Biwa Museum, Kusatsu; LPC, La Polledrara di Cecanibbio Site; MCDG, Museo Civico Doria, Genova; MCSNM, Museo Civico di Storia Naturale, Milano; MCSNV, Museo Civico di Storia Naturale, Verona; MDRSCF, Museo del Dipartimento delle Risorse Naturali e Culturali, University of Ferrara; MGP,

Elephant-bearing faunas of Sicily

The study of the Pleistocene faunal succession of Sicily has allowed separation of four successive faunal units (faunal complexes, FCs; Bonfiglio et al., 2000; Fig. 2). The oldest fauna containing elephants is the so-called P. falconeri FC, dated to the early Middle Pleistocene (Bonfiglio et al., 2000). Fossil-bearing deposits that yielded assemblages belonging to this FC show a disjunct distribution (Bonfiglio and Burgio, 1992), being restricted to the Hyblean plateau in the SE (e.g.,

The Puntali Cave and the G.G. Gemmellaro collection

The Puntali Cave (also known as Piraino or Armetta Cave) is a large karst cavity opened onto an extended limestone cliff (Monte Lungo), near the town of Carini (Palermo), along the NW coast of Sicily (Fig. 1). The entrance of the cave is about 1 km from the present coastal line and is located approximately 90 m above the sea level. The cave has a total length of 110 m and a height of 3 m at the entrance (Mannino, 1978; Burgio et al., 1983). The Puntali Cave has recently been declared a Regional

Taxonomic background

The elephant remains from the Puntali Cave have been referred to various taxa since their discovery. There has been, however, a general consensus in relating the Sicilian material to the largest of the dwarf elephants from Malta, P. mnaidriensis, considered by most of the early authors as a subspecies of P. antiquus. Anca and Gemmellaro (1867), in their monograph of the fossil elephants from Sicily, referred the elephant remains known in great numbers from various caves on the island to the

Material

The Gemmellaro collection in the MGP and OGP forms the basis of the present study. Specimens from Puntali Cave in the MGPP, MDRNCF, MCSNM and MCSNV collections were also used in the analysis. The material includes 17 skulls, of which six nearly complete, 34 mandibles, 25 vertebrae, 12 scapulae, 16 humeri, 11 ulnae, 13 femora, 17 tibiae, 27 isolated tusks and 18 isolated molars. The anatomy and functional morphology of the manus and pes of P. mnaidriensis will be discussed elsewhere. All the

Cranium (Figs. 3–6; Table 2)

The skull of P. mnaidriensis from Puntali Cave (Fig. 3, Fig. 4, Fig. 5, Fig. 6) closely resembles P. antiquus (Pian dell’Olmo, Il Crocefisso, La Polledrara di Ceccanibbio; Maccagno, 1962; Palombo and Ferretti, 2005) and P. namadicus (Narbadda; Osborn, 1942). Specimen MGP 1 is the most complete and one of the largest skulls in the Gemmellaro collection. It has the M3 in use. The squamous part of the occipital is anteriorly bent and the occipito-temporal line (nuchal line) is visible in anterior

Systematic discussion

The Puntali Cave elephant differs from P. antiquus in the following characters: smaller size (see below), infolded POC, zygomatic bones parallel to each other, laterally positioned orbits, more strongly curved tusks, loss of two plates, on the average, in the M3, stronger deltoid tuberosity in the humerus. Other peculiar cranial features possessed by the insular taxon might represent a paedomorphic effect linked to dwarfing: relatively larger orbits and narrower transverse diameter between the

Phylogenetic discussion

The present anatomical study of P. mnaidriensis from Puntali Cave allows a revision of the cranial characters of Palaeoloxodon and of their phylogenetic significance. Compared to primitive elephantines (e.g., Elephas ekorensis, Elephas planifrons), the skull of P. mnaidriensis presents numerous derived characters, such as the anteriorly bent occipital squama, the strong and folded POC reaching almost to the nasals, the transversally enlarged parietals, the transversally expanded retro-tympanic

Conclusions

The present anatomical study of the rich late Middle (or possibly late) Pleistocene Puntali Cave elephant remains has allowed the recognition of a series of skeletal autapomorphies of P. mnaidriensis supporting the hypothesis that this taxon is a bona fide species and not just a small-sized form of mainland P. antiquus. The current knowledge of the mammal succession of Sicily indicates that the colonization of the island by P. antiquus and the dwarfing event that gave origin to P. mnaidriensis

Acknowledgments

I am grateful to all the persons in charge of the collections I have studied: Valerio Agnesi, Carolina di Patti (Palermo), Luca Altichieri (Padova), Benedetto Sala (Ferrara), Paolo Arduini (Milano), Roberto Zorzin (Verona), Paolo Agnelli (Firenze), Elisabetta Cioppi (Firenze), Andrew Currant (London), Keiichi Takahashi (Lake Biwa Museum) and Yoichi Kondo (Nojiriko Museum). I thank Federico Masini, Daria Petruso and Carmela Simonelli for assisting me with the data collection at MGP and OGP, for

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