| Atlantosaurus | |
|---|---|
 | |
| Illustration of the sacrum ofA. montanus | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Superfamily: | †Diplodocoidea |
| Family: | †Diplodocidae |
| Genus: | †Atlantosaurus Marsh, 1877 |
| Species: | †A. montanus |
| Binomial name | |
| †Atlantosaurus montanus (Marsh, 1877) | |
| Other species | |
| Synonyms | |
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Atlantosaurus (meaning "Atlas lizard") is adubiousgenus ofsauropoddinosaur. It contains a single species,Atlantosaurus montanus, from theLate Jurassic upperMorrison Formation ofColorado, United States.Atlantosaurus was the first sauropod to be described during the infamous 19th centuryBone Wars,[1] during which scientific methodology suffered in favor of pursuit of academic acclaim.[2]
Thetype specimen, YPM 1835, found byArthur Lakes in Lakes Quarry Number 1 in theMorrison Formation ofColorado, United States, was named and described byOthniel Charles Marsh, Professor ofPaleontology atYale University (then calledYale College), in July 1877 asTitanosaurus montanus.[3] Marsh soon learned that the nameTitanosaurus had already been used earlier that year byRichard Lydekker to describe a different sauropod from India, so he renamed itAtlantosaurus montanus. Marsh estimated the length of the animal at twenty-four metres, "if built like a crocodile".[4]
The skeletal remains discovered, two or three posterior sacral vertebrae connected to the ilia, were initially distinguished by their immense size and by thepleurocoels (air-filled pockets) in thevertebrae. However, since the time of its discovery, these features have been found to be widespread among sauropods, making it nearly impossible to distinguish the two known vertebrae ofAtlantosaurus from those of its relatives. Since it is unclear whether or notAtlantosaurus montanus actually represents a distinct species, it is considered anomen dubium ("dubious name"),[5] though some researchers have considered it a likely synonym ofApatosaurus ajax.[2][6]
In 1878, Marsh named a second species,Atlantosaurus immanis, "the immense one", based onholotype YPM 1840, a nearly complete postcranial skeleton, also found by Lakes, in Quarry Number 10. Marsh estimated its length at thirty-five metres from a presumed thighbone length of 2.5 metres.[7] Later the femur length was determined at 1.95 metres. "A."immanis was in 2015 identified as a dubious member of theApatosaurinae separate fromApatosaurus andBrontosaurus, but did not examine its relationship withAtlantosaurus montanus.[8]
