Published in RIVISTA ITALIANA DI PALEONTOLOGIA E STRATIGRAFIA VOL. 116 (2), JULY 2010
A NEW SPECIMEN OF NOTHOSAURUS FROM THE LATEST ANISIAN (MIDDLE TRIASSIC) BESANO FORMATION (GRENZBITUMENZONE) OF ITALY
A nearly complete but disarticulated skeleton of a small sized nothosaur is described. The specimen was collected in 2003 from an outcrop of the Besano Formation (Grenzbitumenzone of Swiss authors) of latest Anisian (Middle Triassic) age, in the Monte San Giorgio Area, northern Italy. The osteology of the postcranial skeleton supports the assignment to the genus Nothosaurus, and also excludes its belonging to Nothosaurus giganteus/Paranothosaurus amsleri already known from coeval localities of the Besano Formation in the Swiss part of the Monte San Giorgio area. Despite the lack of most of the skull, which contains diagnostic characters at the species level for Nothosaurus, the few preserved cranial elements suggest similarities with N. juvenilis which skull, and only known part, is also of comparable size. This specimen is particularly significant because it improves the knowledge of the osteology of N. juvenilis and because the second Nothosaurus species, smaller than N. giganteus/P. amsleri, suggests coexistence of sympatric species characterized by size and, probably, trophic differentiation within the genus Nothosaurus in the Monte San Giorgio area as occurred in the coeval Germanic Basin.
Photographs (left) and sketches (right) of the four small slabs showing the position of most relevant bones, abbreviations are: c) carpal bone (unidentified), cl) clavicle, co) coracoid, cv) cervical vertebrae (both isolated centra and neural arches), h) humerus, mc) metacarpals, na) neural arches, r) ribs, ra) radius, rp) retroarticular process of the lower jaw, u) ulna. Scale bars equal 50 mm.
A) Photographs and B) sketch of the larger, composite slab showing the position of most relevant bones, Abbreviations are: as) astragalus, ca) calcaneum, cdv) caudal vertebrae, cr) caudal ribs, f) femur, il) ilium, is) ischium, mt) metatarsals, p) pubis, ph) phalanges, sr) sacral ribs, sv) sacral vertebrae, ti) tibia, 3dt) fourth distal tarsal. Scale bars equal 50 mm.
Skull and vertebral elements. A) retroarticular processes of the lower jaw, portion of the quadrate ramus of the pterygoid, of the quadrate in anatomical connection with the lower jaw, several disarticulated cervical vertebrae are visible between the two retroarticular processes Scale bar 0.5cm
A) Sketch of preserved elements of the skull (light grey) and of the lower jaw (dark grey), along with disarticulated cervical centra (outlined). B) detailed drawing of the right articular area. Scale bar 1cm.
A) cervical centrum B) cervical neural arch, ventral view; C) dorsal neural arch, dorsal view; D) dorsal neural arch and spine, cranial view; E) caudal neural arch and spine, lateral view. Scale bars equal 1 cm
Girdle and limb bones. Scale bars 1 cm.
Home Research Triassic Reptiles