Description of Schizobrissus obradori sp. nov. (Brissidae, Spatangoida) from the Upper Miocene of Menorca (Balearic Islands, Western Mediterranean)

[eng] The study of the Tortonian calcarenites located in the Algendar ravine (Ferreries,
Menorca) has hallowed the identification of eleven species of echinoids, among
which the spatangoids clearly dominate, with eight species included in five genera, in
addition to two genera of echinolampadidae and one clypeasteroid. Among the
spatangoids, it is worth higlighting the presence of two species of the genus
Schizobrissus Pomel, 1869, one of which (Schizobrissus obradori sp. nov.) is
described for the first time. The genus Schizobrissus is known in the late Miocene of
Europe and North Africa by a single species (Schizobrissus cruziatus [Agassiz in
Agassiz et Desor, 1847]), so that the description of a new species (with a relatively
large size) in the Mediterranian basin is somewhat surprising, given the extensive
palaeoechinological tradition existing in Europe and due to the fact that the echinoids
of the Upper Miocene of Menorca have been known since the end of the 19th and the
beginning of the 20th, thanks above all to the studies carried out by the French
echinologist Jules lambert. Schizobrissus obradori sp. nov. is described from the
calcarenitic facies diposited in the lower part of the infralittoral zone of the Algendar
ravine, of Tortonian age (included in the Lower Bar Unit) and the Messinian Reef
Unit of Ciutadella de Menorca. The new species differs from the other species
included in the genus Schizobrissus (S. cruziatus and its possible synonyms, S. latus
[Wrigth, 1855], S. mauritanicus Pomel, 1887 and S. locardi [Cotteau in Locard,
1877]) by a more anteroposterior compressed test. The greatest similarities are
established between Schizobrissus obradori sp. nov. and Schizobrissus sp. from the
Lutecien (Middle Eocene) of Alfaz del Pi (Alicante, east of the iberian peninsula).
Emphasis is placed on the need for a thorough revision of the genus Schizobrissus in
order to understand its origin and distribution, geographically as well as
chronologically.