| Futalognkosaurus | |
|---|---|
 | |
| Mounted replica skeleton,Royal Ontario Museum | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauria |
| Clade: | †Lognkosauria |
| Genus: | †Futalognkosaurus Calvoet al.,2007 |
| Type species | |
| †Futalognkosaurus dukei Calvoet al.,2007 | |
Futalognkosaurus (/ˌfuːtəˌlɒŋkoʊˈsɔːrəs/FOO-tə-long-ko-SAW-rəs;[2] meaning "giant chief lizard") is agenus oftitanosauriandinosaur. Theherbivorous[3]Futalognkosaurus lived approximately 93.5 to 85.8 million years ago[1] in thePortezuelo Formation, in what is now Argentina, of theConiacian stage of the lateCretaceous Period. The fish and fossilized leaf debris on the site, together with other dinosaur remains, suggest a warm tropical climate inPatagonia during this period.
Fossils ofFutalognkosaurus were found in theNeuquén province ofArgentina in 2000, and were scientifically described in 2007, alongside sauropods,Megaraptor,Unenlagia, iguanodonts, peirosaurids, and pterosaurs. The holotype was found near the margins of a river. The holotype was hypothesised to have been washed into the river after its death. Due to its giant size the carcass likely acted as a barrier, altering the course of the river around it, lasting long enough for fish and bivalves to live in it, and eventually leaving an oxbow lake behind.[4]
The genus name is derived from the local indigenous languageMapudungun and is pronounced foo-ta-logn-koh-sohr-us: "futa" means "giant" and "lognko" means "chief".[4] It is based on three fossil specimens, yielding an estimated 70% of the skeleton in total. The fossil team described the find as "the most complete giant dinosaur known so far".
Theholotype of thetype species,Futalognkosaurus dukei, was originally estimated at 32 to 34 metres (105 to 112 ft) in length.[4] In 2008 this was downsized to 26 metres (85 ft).[5] In 2012Holtz estimated it at 28 metres (92 ft) long and with an approximate weight of 43.5 to 51 tonnes (48-56 short tons).[6][7] An estimate byGregory S. Paul in 2016 was thatFutalognkosaurus had a maximum length of 30 metres (98 ft) and a weight of 50+ tonnes (55 short tons) .[8] In 2016, using equations that estimate body mass based on the circumference of the humerus and femur of quadrupedal animals, it was given an estimated weight of 38.1 tonnes (42 short tons).[9] In 2019,Paul estimated the weight of the holotype specimen, (MUCPv-323) at 29 tonnes (32 short tons),[10] and later, in 2020, Molina-Pérez and Larramendi estimated its length at 24 metres (79 ft), and its weight at 30 tonnes (33 short tons).[11] In 2024, Paul estimated its length at 24 metres (79 ft), and its weight at 29.5 tonnes (32.5 short tons).[12]
Its long neck contained 14 vertebrae, and was overa meter deep in places due to its extremely tall neural spines which had a distinctive"shark-fin" shape. The hips were also extremely large and bulky, reaching a width of nearly 3 metres (9.8 ft).[13]
In their phylogenetic analysis, Calvo and colleagues foundFutalognkosaurus to be a member of theTitanosauridae (orLithostrotia, depending on the definitions being used), and most closely related toMendozasaurus. They defined a newclade for the group containing bothFutalognkosaurus andMendozasaurus, their common ancestor, and all descendants, which they named theLognkosauria.[4] The authors foundMalawisaurus to be the sister group of this new clade. Another, much later member of Lognkosauria is the colossalPuertasaurus,[14] which may be the biggest dinosaur so far known. BesidesFutalognkosaurus, otherfauna was discovered in the Futalognko site, including two further undescribed sauropod taxa, specimens ofMegaraptor,Unenlagia and somepleurodiranturtles.
The followingcladogram shows the results of an analysis by Calvoet al. in 2007, where they placedFutalognkosaurus within the groupTitanosauria, more precisely the clade Lognkosauria:[4]
