Pronunciation: sih-BEE-ro-TIE-tan
Meaning: Siberian giant
Author/s: Averianov et al. (2017)
Synonyms: None known
First Discovery: Siberia, Russia
Acta Ordinal: #948
Sibirotitan astrosacralis
A northern giant in a land of long winters, Sibirotitan astrosacralis hails from Siberia in the transcontinental country of Russia, and represents one of the earliest titanosauriform sauropods known from Asia. Its bones come from the Shestakovo locality along the Kiya River—an ecosystem of mixed conifer–fern floodplains inhabited by stegosaurs, ankylosaurs, small theropods, early birds, turtles, crocodilians, and the abundant ceratopsian Psittacosaurus sibiricus, all thriving along the shifting channels and seasonal wetlands of the Early Cretaceous-aged Ilek Formation, far from the equatorial warmth usually associated with sauropods.
The species name astrosacralis refers to the animal's most striking feature: a "star-burst" sacrum — a block of fused hip vertebrae, literally "the sacred bone" — in which the ribs radiate outward from the centre in a pattern unlike that of any other dinosaur. The second neck vertebra — the axis — bears a broad, flat, rectangular underside and a pair of deep, sharply bordered hollows at the rear, framed by upward-sweeping ridges. Other parts of the skeleton add further distinctive traits, including an unusually tall ridge on the back bones and a sacrum composed of only five vertebrae. Taken together, those features mark Sibirotitan as unique among its kind, while the simplified architecture of its neck vertebrae, with a distinctive airy inner texture, aligns it with Somphospondyli — a group of sauropods whose name literally means "spongy vertebra".
The species name astrosacralis refers to the animal's most striking feature: a "star-burst" sacrum — a block of fused hip vertebrae, literally "the sacred bone" — in which the ribs radiate outward from the centre in a pattern unlike that of any other dinosaur. The second neck vertebra — the axis — bears a broad, flat, rectangular underside and a pair of deep, sharply bordered hollows at the rear, framed by upward-sweeping ridges. Other parts of the skeleton add further distinctive traits, including an unusually tall ridge on the back bones and a sacrum composed of only five vertebrae. Taken together, those features mark Sibirotitan as unique among its kind, while the simplified architecture of its neck vertebrae, with a distinctive airy inner texture, aligns it with Somphospondyli — a group of sauropods whose name literally means "spongy vertebra".
(Siberian Giant with a Star?Shaped Sacrum)Etymology
Sibirotitan is derived from "Siberia" (where it was found) and the Greek "titan" (for the Titans: the giant Greek gods that preceded Zeus and his Olympians).
Two years before its official description, the press had nicknamed it "Sibirosaurus".
The species epithet, astrosacralis, is derived from the Greek "astro" (star) and the Latin "os sacrum" (sacred bone), referring to the ribs of the sacrum (a block of fused hip vertebrae) which, when viewed from above, radiate from the centre out, like the rays of a star.
Discovery
The remains of Sibirotitan were discovered in the Ilek Formation at the Shestakovo 1 locality, on a 20–35-m-high cliff on the right bank of the Kiya River, which extends 800 m northwest from the village of Shestakovo, Chebula District, Kemerovo Province, Russia. The cliff is divided by a ravine into two unequal parts: the northern Bol'shoi Yar ("Big Cliff"), which is longer and higher, and the southern Malyi Yar ("Small Cliff"), which—funnily enough—has yielded most of the remains.
The holotype (PM TGU 120/10-Sh1-22) is a back vertebra, excavated from the Bol'shoi Yar cliff in 2011.
Referred specimens include neck vertebrae (PM TGU 120/4-Sh1-1; PM TGU 120/8-Sh1-3, excavated in 2008; and PM TGU 120/8-Sh1-4), a fused sacrum and ilium (PM TGU 120/8-Sh1-1), and nine isolated teeth (LMCCE 105/4 and 108/4 to 115/4), which were all found between 1994 and 2011, and a partial foot (PM TGU 16/0-81-88) first described by Alifanov et al. in 2002. A smaller neck vertebra (the axis), PIN, no. 929/14, discovered by local teacher G.A. Chudova and now stored at the Borissiak Paleontological Institute of the Russian Academy of Sciences (PIN) in Moscow, was assigned to Sibirotitan by Averianov et al. in 2022. In the early 1960s, fossils of a large dinosaur were found at Shestakovo 1 and reported by Bulynnikova and Trushkova in 1967. They might have belonged to the same individual of Sibirotitan, but they were apparently washed away by the river and have been lost.
