|
UPPER
TRIASSIC CHITONS FROM THE ITALIAN DOLOMITES
The
species Lepidopleurus
davolii n.sp., Lepidopleurus
dellangeloi n.sp., Mesochiton
dolomiticus n.sp., Crenatolorica
zardinii Laghi 1981, Schizoproctus
prior n.gen.n.sp. and Panarthron
triadicum n.gen.n.sp. are illustrated and discussed. The
valves collected are generally broken and of very small size; Mesochiton
dolomiticus is the more frequent species. The studied
material comes from the higher part of the S.Cassiano Fm. (Upper
Julic). The majority of the recorded species have the articulamentum
of lepidopleurid type. Moreover Crenatolorica
zardinii shows a crenature at the lorìca edge here
interpreted as a miscarried manner of binding of the shell to
the mantle in chitons. Moreover, Panarthron triadicum
uses an other additional manner of binding of the shell
to the mantle by means of an expansion of the articulamentum
(Haleya type),
interpreted as the new feature allowing the subsequent radiation
of the Iscnochitonida. The anal sinus of Scizoproctus
prior is here intepreted as a functional feature analogous
(or homologous) of the marginal slit in the Archeogastropoda and
therefore it is considered useful only at the generic level. |
