Ginosaurus (lat.: Jainosaurus) is a genus of herbivorous sauropods from the group of Titanosaurs (Titanosauria), which lived in the late Cretaceous period on the territory of modern India. Jainosaurus septentrionalis is the only known species of Jainosaurus.
In 1933, paleontologists Friedrich von Huene and Charles Alfred Matley, during their joint stay in London, classified the found Ch. Matli in 1917, a fragment of the skull as belonging to a previously unknown species of Antarctosaurus (lat.: Antarctosaurus) Antarctosaurus septentrionalis.
The Latin specific epithet septentrionalis (“northern”) assigned by them to the new dinosaur indicates that this fossil was found much further north than the remains of the species Antarctosaurus wichmannianus (“Wichmann’s Antarctosaurus”) found in Argentina.
The lectotype of Jainosaurus, accession no. GSI IM K27/497, was discovered near the Indian city of Jabalpur in the Lameta formation, which belongs to the Maastrichtian stage. It consists of the skull of a young animal.
Von Huene and Matley also attributed to this species one hyoid bone, the squamous part of one temporal bone, and several other parts of the skeleton. In 1982, the Indian paleontologist Sohan Lal Jain published the results of a study of the brain structure of this dinosaur, which was carried out using a cast of the inside of its skull made by Charles Mutley.
In 1995, Adrian Paul Hunt identified the species in question as a separate genus, Ginosaurus. This generic name is given to the dinosaur in honor of Sohan Jain. Very ironically, Jain himself believes that this is not a separate genus or species, but just an instance of the “Indian Titanosaurus” (lat.: Titanosaurus indicus), known from remains also found in the Lamet Formation.
Fragments of other parts of the skeleton, found in the same place and possibly belonging to the same dinosaur, were discovered only at the beginning of the 21st century in the collections of the Geological Survey of India in Calcutta.
We are talking about fragments of ribs (inv. No. GSI K20/326, K27/425); 1 tail vertebra (inv. No. GSI K20/317), 4 lower processes, or chevrons, of the caudal vertebrae (Inv. Nos. GSI K27/492–494, 496), left and right shoulder blades (only one casting survives); 1 fragment of the sternum (inv. No. GSI K20/647); 1 humerus (no inventory number), 1 radius (inv. No. GSI K27/490) and 1 ulna (Inv. No. GSI K27/491). They were described in 2009 by paleontologist Jeffrey Wilson.
In 1996, Shankar Chatterjee attributed another cranium to this species, inv. No. ISI R162. Several fragmentary remains found in Pakistan are also believed to belong to Jainosaurus.
The length of the dinosaur’s skull is 168 mm, and the length of the humerus is 134 cm. Based on this, the length of the dinosaur’s body is estimated at 18 meters. Most of the morphological features of Jainosaurus combine it with titanosaurs, but at the same time there are a number of unique features that make it possible to distinguish this taxon from related forms.
So, in his cranium there is a noticeable trace of the anterior ear bone, reaching the basipterygoid process. The deltopectoral ridge on the humerus is located closer to the middle of the body of the bone at a right angle to it; the bone around the depression next to the crest is relatively thin. The condyle in the lower part of the humerus, connecting it to the radius, expands from the front side.
Von Huene assigned the species Antarctosaurus septentrionalis to the family Titanosaurids (lat.: Titanosauridae). On the other hand, according to Jeffrey Wilson, we are talking about a very far evolved (derivative) representative of the Titanosaurs group.
Wilson did not reveal a particularly close relationship with the Indian form of Isisaurus (lat.: Isisaurus), but established a relationship between Jainosaurus and South American sauropods such as Pithekunsaurus, Muyelensaurus and Antarctosaurus. With the Malagasy form of Rapetosaurus (lat.: Rapetosaurus) no special connection was found either.