Borghi, E. 2013. Mazettia (Maretiidae) un caratteristico echinoide del Miocene dell'Emilia-Romagna. Notiziario naturalistico della Societé Reggiana di Scienze Naturali 2013, 9-20.

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Newly referred topo-typic material from the Langhian Pantano Formation (Roveri, 1966) of the Northern Apennines enables to complete the morphological description of Mazettia pareti (Manzoni, 1879), the type-species of the genus Mazettia Lambert & Thiery in Lambert, 1915, an endemic echinoid of the Italian Miocene. The structures of the apical system and of the plastron, the subanal fasciole, the spines and other morphological particulars which were still unknown or unclear, due to the poor preservation of the fossil material so far available to study, are herein described and illustrated. The apical disc (Pl. 1, fig. 5) is ethmolytic, with four gonopores in the interior part of the plates. The anterior ambulacrum is narrow, with vertically arranged pore-pairs (Pl. 1, fig. 4). Paired petals weakly bowed, extending almost to ambitus, commonly converging distally and with wide interporal zone at mid-length (Pl. 1, figs. 1-2a,b). Labral plates narrow and elongate (Pl. 1, fig. 3), extending to the third adjacent ambulacral plate, with labrum slightly projecting. Episternal plates (Pl. 2, fig. 6) strongly indented to rear by three enlarged ambulacral plates (plates 6-8). Periproct adorally framed by interambulacral plates 5a/b and located in the short posterior test face. A thin peripetalous fasciole is present, running around the margin. The subanal fasciole (Pl. 2, fig. 6) is shield-shaped. Spines are rather long (22-28 mm) with thin and smooth shaft and large crenulate base. Mazettia is considered (Smith & Stockley, 2005) as immediate sister group of Linopneustes A. Agassiz, 1881, a genus consisting only of Recent species living in the Caribbean Sea and the Indo-Pacific. The newly referred morphological features confirm the close affinity of Mazettia with Linopneustes. Paired petals converging distally in Mazettia, rather than remaining broadly open as in Linopneustes, was so far considered as the main distinctive feature between the two genera. But in a part of the examined specimens (20%) the paired petals are open distally (Pl. 2, figs. 1-2), whereas in L. longispinus (Agassiz, 1879) they are short and almost distally closed (Mortensen, 1950). Mazettia is herein separated from Linopneustes also by the depressed and slightly arched lateral profile (Pl. 1, fig. 2b) and the elongate and posteriorly restricted test outline. Among extant species of Linopneustes, M. pareti shows closest affinities with L. longispinus, by the slightly projecting labrum and the tubercles present in the oral ambulacra near the ambitus, thus confirming the strong affinities between the bathyal echinofauna of the Mediterranean Miocene and the actual Caribbean Sea, as highlighted by Smith & Gale (2009). Based on the associated fossil echinoid fauna and by comparison with living sister taxa and their bathymetric ranges, Mazettia was likely an epifaunal echinoid inhabiting deep muddy bottoms. Its geographic and stratigraphical distribution ranges from the Aquitanian of Sardinia to the early Langhian of Emilia-Romagna and Marche.

Italy

Echinoidea

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