A sauropterygian which could reach a length in excess of three meters diagnosed by the following unique combination of characters: plesiosaurian massive atlas-axis complex made of eight sutured elements with double atlas and axis intercentra meeting ventrally; atlas centrum subequal in lateral extension to the atlantal arch and intercentrum, excluded both from the ventral margin of the complex and the lateral margin of the cotyle, with a fused, thorn-like axial rib; neural spines of anterior cervicals with wide, arched prespinal lamiae, features found in some plesiosaurians but never in pistosaurids or other stem-group sauropterygians; posterior expansion in the mid-shaft of each dorsal rib forming a broad and blunt uncinate process (convergent in the placodont Paraplacodus Peyer, 1931); plesiosaurian, spade-.shaped pubis with convex ventromedial margin lacking both an obturator foramen and an articulation to the ilium, associated with a stout, "hourglass-shaped" ilium with twisted shaft.
Bobosaurus has the following autapomorphies: cervical centra "pear-shaped" in anteroposterior view and higher than wide; presence of infraprezygapophysis and "infrapostzygapophysis" from the pectoral vertebrae 3-4 up to the first "caudal" vertebra and possibly as far posterior as "caudal" 11 like those found in the dorsals of Simosaurus but with a reversed anteroposterior polarity; tall neural spines on all cervical to caudal vertebrae including the axis; spines of the anterior cervicals at least 1.5 times the centrum height; spines of the dorsal vertebrae up to three times the centrum height; spines of mid-anterior caudal vertebrae 2.3-2.8 times the centrum height; neural spines of "sacral" vertebrae 4-9 to mid-caudal vertebrae with a bottle-shaped profile in lateral view; distal and backward-turned segments of the shafts of mid-posterior cervical ribs shorter or as short as the proximal segment and with a distally rounded, striated distal tips; lightened skeleton (hollow neural spines, coarsely spongy arches and cervical and possibly anterior dorsal ribs, spongy centra); large humerus (9 times the length of mid-dorsal centrum)

after Roman name Forum Julii of the Fruilian part of the Region Fruili Venezia Giulia