Jainosaurus

History

The dinosaur Jainosaurus septentrionalis has a tangled scientific backstory, closely linked to the problematic genera Titanosaurus and Antarctosaurus. The first fossil piece, a humerus labeled GSI K22/754, was found in 1871 or 1872 by Henry Benedict Medlicott. The main set of bones, the holotype, was dug up by Charles Alfred Matley between 1917 and 1920 near Jabalpur in the Lameta Formation. In 1933, Friedrich von Huene and Matley named these remains Antarctosaurus septentrionalis. The species name means "northern" in Latin, because it was found in the Northern Hemisphere, while the genus name Antarctosaurus means "saurian from the Southern Hemisphere," referring to its Argentine type species. The genus name Jainosaurus honors Indian paleontologist Sohan Lal Jain, who studied cranial nerve impressions in a skull and published his findings in 1982. Ironically, Jain himself thought these bones belonged to Titanosaurus when he described Isisaurus in 1997. However, Wilson and Upchurch rejected that idea in 2003, because Titanosaurus itself is a poorly defined genus. In 1995, Hunt and colleagues, believing Antarctosaurus was a dicraeosaurid, made the clearly titanosaurian Antarctosaurus septentrionalis the type species of a new genus, Jainosaurus. They chose the braincase GSI IM K27/497 as the lectotype, and further separated Jainosaurus from Antarctosaurus based on braincase details. A detailed 2009 study by Jeffrey Wilson and others confirmed Jainosaurus septentrionalis as a valid species. They showed that the postcranial bones, once thought lost, were mostly still in the Geological Survey of India collection in Calcutta. These include dorsal rib fragments, a caudal vertebra, four chevrons, casts of both shoulder blades, a sternal plate, a humerus, a radius, and an ulna. In 1996, Sankar Chatterjee assigned a second braincase, ISI R162, to this species. Some fossils from Pakistan and from the Chota Simla region, now in the Natural History Museum, might also belong to Jainosaurus, though the Chota Simla specimen is smaller than the holotype.