Page 1 - A_new_subtropical_temperate-Borghi2016
P. 1

Journal of Systematic Palaeontology, 2016

Downloaded by [vittorio garilli] at 22:43 08 June 2016  A new subtropical-temperate brooding echinoid with no marsupium: the first
                                                            Mediterranean and the last European Temnopleuridae from the Early
                                                                                             Pleistocene of Italy

                                                                                                     Enrico Borghia and Vittorio Garilli b*

                                                                      aSocieta Reggiana di Scienze Naturali, Via Tosti 1, I-42100 Reggio Emilia, Italy; bAPEMA-Paleosofia,
                                                                                   Research and Educational Service, Via Alla Falconara 34, I-90136 Palermo, Italy

                                                                                                 (Received 24 November 2015; accepted 25 February 2016)

                                                          The regular echinoid Placentinechinus davolii gen. et sp. nov. is described from eight Early Pleistocene
                                                          (GelasianÀCalabrian) sites in north and south Italy. It is the most recent record known for the family Temnopleuridae in
                                                          the European domain and the first in the Mediterranean area. A review of temnopleurid palaeobiogeography, and
                                                          morphological comparisons, suggest that P. davolii was derived from a marsupiate brooder that lived in the north-east
                                                          Atlantic during MessinianÀmiddle Gelasian time. This indicates a brooding reproductive strategy for P. davolii, although
                                                          it does not bear any evidence of a marsupium. The stratigraphy and climatic setting inferred for the study sites indicate that
                                                          Placentinechinus represents a significant southward shift of the European Temnopleuridae, triggered by a progressive
                                                          cooling that changed the Mediterranean climate from tropical to subtropical-temperate. A further climatic deterioration,
                                                          perhaps that at about 0.8 Ma with the onset of the 100 kyr-controlled Ice Ages, caused its extinction. The palaeoecology of
                                                          Placentinechinus, as deduced from palaeoenvironmental reconstructions of the study sites, indicates that it lived in
                                                          shoreface to shallow offshore, moderately agitated waters, often together with the scallop-polychaete Aequipecten-Ditrupa
                                                          association. It tolerated more or less marked conditions of turbidity, but flourished in trophically well-structured
                                                          palaeocommunities. The main morphological characters distinguishing Placentinechinus are the very depressed test and
                                                          the extremely large apical opening, up to 82% of the test diameter, which is so far the largest known for an adult
                                                          echinacean echinoid. The statistically exhaustive morphometric data collected from more than 100 Placentinechinus tests
                                                          indicate that inferring sexual dimorphism for Temnopleuridea echinoids based only on the apical disc width could be
                                                          misleading. For P. davolii, both climate and environmental stability, in terms of sedimentation rate and nutrient supply,
                                                          may have been concurrent drivers of its evolutionary history.


                                                          Keywords: Echinoidea; Temnopleuridae; brooding; Mediterranean; Early Pleistocene; palaeoclimate

                                                        Introduction                                                                     examples of change within echinoid assemblages from the
                                                                                                                                         Atlanto-Mediterranean Neogene may be traced in the dis-
                                                        The intricate climatic evolution that followed the late                          appearance of the sand dollar Amphiope Agassiz, 1840 in
                                                        Miocene palaeogeographical change associated with                                the early Messinian (Stara & Borghi 2014), and of the
                                                        Mediterranean desiccation (Ruggieri 1967; Hsu€ et al.                            genera Clypeaster Lamarck, 1801, Hypsoclypus Pomel,
                                                        1973) led to significant shifts in the faunal assemblages of                      1869 and Echinoneus Leske, 1778 in the Gelasian
                                                        the Atlanto-Mediterranean domain (e.g. Malatesta & Zar-                          (Neraudeau et al. 2001). As shown here, a few shallow-
                                                        lenga 1986; Loubere & Moss 1986; Cronin et al. 1993;                             water taxa, such as Echinolampas Gray, 1825 and Schize-
                                                        Head 1998; Cronin et al. 1999; Monegatti & Raffi 2001;                            chinus Pomel, 1869, disappeared in the early Calabrian.
                                                        Taviani 2002; Wood 2009; Garilli 2011; Vertino et al.                            The main changes in the deeper-water assemblages
                                                        2014). Compared to other groups, there are little data con-                      include the disappearance of Histocidaris Mortensen,
                                                        cerning the NeogeneÀQuaternary faunal change within                              1903, Stirechinus Desor, 1856 and Cidaris margaritifera
                                                        echinoids (Roman & Soudet 1990; Neraudeau et al. 2001;                          Meneghini, 1862, whose last Mediterranean record dates
                                                        Kroh 2007; Borghi et al. 2014), which are one of the most                        back to the early Calabrian of Sicily (Borghi et al. 2014).
                                                        successful marine groups due to their various reproductive                       All these genera, or their closely related living taxa, today
                                                        strategies (Gillespie & McClintock 2007). Significant                             inhabit warm temperate/tropical areas.

                                                        *Corresponding author. Email:

                                                        Ó The Trustees of the Natural History Museum, London 2016. All Rights Reserved.
   1   2   3   4   5   6