| Volkheimeria | |
|---|---|
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Genus: | †Volkheimeria Bonaparte,1979 |
| Species: | †V. chubutensis |
| Binomial name | |
| †Volkheimeria chubutensis Bonaparte, 1979 | |
Volkheimeria is an extinct genus ofsauropoddinosaurs that lived in what is now Argentina during the Early Jurassic, about 179–178 million years ago. Its type and only species isVolkheimeria chubutensis.
The only known specimen ofVolkheimeria was discovered at the site of Cerro Cóndor Sur, roughly a kilometer west of the village ofCerro Cóndor inChubut Province, Argentina.[2] In1979,José Bonaparte described it as representing a new genus and species,Volkheimeria chubutensis, alongside two other species discovered in the same strata,Piatnitzkysaurus floresi andPatagosaurus fariasi.[3] The genus nameVolkheimeria honors the Argentinean paleontologist Wolfgang Volkheimer.[4]
Only a single specimen ofVolkheimeria chubutensis is known: theholotype PVL 4077, a partial skeleton from theCañadón Asfalto Formation ofArgentina. This specimen consists of a partial cervical vertebra, two complete and two partial dorsal vertebrae, part of the sacrum, several incomplete caudal vertebrae, partial ilia, a pubis, an ischium, a femur, and a tibia.[2] The specimen was not fully grown, but had probably reached sexual maturity.[5] An isolated tooth found in the Cañadón Asfalto Formation, MPEF-PV 10860, may belong toVolkheimeria, though this cannot be proven without more complete specimens.[6]
The size of a fully-grownVolkheimeria is not known, as it is only known from an immature specimen.[7] A tooth that may belong toVolkheimeria is broad and spoon-shaped, with large denticles present on the upper two-thirds of the tooth crown.[6]Pleurocoels, excavations in the side of the vertebrae for air sacs, were present in thecervical vertebrae but not thedorsal vertebrae.[2] The neural arches of the dorsal vertebrae are proportionally short and the neural spines are mediolaterally compressed and have mostly flat lateral surfaces, in both respects differing from more derived sauropods.[3][2] Thecaudal vertebrae are short from front to back, implying the tail as a whole was relatively short as well. Thetibia is fairly short relative to thefemur, at only 58% of its length.[2]
Volkheimeria was originally identified as a primitive sauropod, distinguishable fromPatagosaurus. Some phylogenetic analyses of the taxon have recovered it as aeusauropod,vulcanodontid, or primitive sauropod, though its position is variable due to its incomplete nature. The phylogenetic analysis of Pol and colleagues in 2022 recoveredVolkheimeria as a non-eusauropod based on primitive features of the vertebrae, though alternative placements were identified as closer to eitherAmygdalodon orArchaeodontosaurus, as shown below.
Bonaparte initially regardedVolkheimeria as a primitive member ofCetiosauridae.[3] He considered both it andLapparentosaurus to represent an early stage in cetiosaurid evolution, more advanced thanVulcanodon but more primitive thanPatagosaurus andCetiosaurus.[8][9] In 1990, John S. McIntosh included bothVolkheimeria andLapparentosaurus inBrachiosauridae,[10] albeit without providing anatomical evidence for classifyingVolkheimeria as such.[11] In 2004, Upchurch et al. regarded the affinities ofVolkheimeria as uncertain, due to the lack of aphylogenetic analysis including the taxon.[11] In 2011, Pol et al. included bothVolkheimeria andLapparentosaurus in a phylogenetic analysis, and recovered them as basal eusauropods, more derived thanShunosaurus but more basal thanBarapasaurus, withVolkheimeria more basal thanLapparentosaurus.[12] In 2017, Cerda et al. foundVolkheimeria to be a non-eusauropod sauropod closely related toTazoudasaurus.[5] In 2018, Holwerda and Pol foundVolkheimeria to be a non-eusauropod sauropod, as the sister taxon ofSpinophorosaurus.[13] In 2025, Gomez and colleagues foundVolkheimeria to be a basal sauropod more closely related to eusauropods thanAmygdalodon orGongxianosaurus but not as closely related to eusauropods asVulcanodon andTazoudasaurus.[14]
Volkheimeria lived during theToarcian age of the Early Jurassic, 178-179 million years ago.[2] The beginning of the Toarcian was a time of significant faunal turnover for sauropodomorphs, as all sauropodomorph lineages except for sauropods died out and eusauropods, which became the dominant sauropod group in the Middle Jurassic, began to diversify.[15]Volkheimeria was not a member of the eusauropod radiation, and was probably a representative of a lineage that diverged from other sauropods in the earliest Jurassic or even the Triassic.[2]
The ecosystem represented by the Cañadón Asfalto Formation included at least four sauropods other thanVolkheimeria chubutensis, all of them eusauropods:Bagualia alba,[15]Patagosaurus fariasi, an unnamed basal eusauropod,[16] and a possibleneosauropod.[17]
