| Buriolestes | |
|---|---|
.jpg) | |
| Block containing the holotype fossil | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Genus: | †Buriolestes Cabreiraet al. 2016 |
| Species: | †B. schultzi |
| Binomial name | |
| †Buriolestes schultzi Cabreiraet al. 2016 | |
Buriolestes is a genus of earlysauropodomorphdinosaurs from theLate TriassicSanta Maria Formation of theParaná Basin in southernBrazil. It contains a single species,B. schultzi, named in 2016. The type specimen was found alongside a specimen of thelagerpetiddinosauromorphIxalerpeton.[1]
Theholotype specimen, ULBRA-PVT280, was discovered in 2009 in the Buriol ravine inSão João do Polêsine,Brazil.[1][2] These rocks are part of theSanta Maria Formation, which dates to theCarnian epoch. The specimen consists of a single skeleton preserving parts of the skull, vertebrae, left forelimb, and left hindlimb. Another set of smaller bones is also present, which may belong to a juvenile or a different taxon altogether. Two individuals ofIxalerpeton were also preserved close by.[1]
Additional remains were discovered in 2015 and published in 2018.[2][3] These include a mostly complete skeleton, CAPPA/UFSM 0035, which preserves a complete skull and most bones apart from tail vertebrae. Additional dinosaur bones from the Buriol locality may also belong toBuriolestes, but their assignment is uncertain. They include a femur (ULBRA-PVT289), a portion of an individual's hip and hindlimbs (ULBRA-PVT056), and a loneaxis vertebra (CAPPA/UFSM 0179). These new finds have madeBuriolestes among the most complete Triassic dinosaurs known, comparable toEoraptor,Herrerasaurus, andCoelophysis.[3]
In 2016, the holotype specimen was described and given thegeneric nameBuriolestes, after the Buriol family; the suffix-lestes is Greek for "robber." Thespecific name honors palaeontologist Cezar Schultz.[1] The well-preserved additional specimens were described in 2018,[3] with the braincase of CAPPA/UFSM 0035 being described in more detail in 2020.[2][4]
AlthoughBuriolestes superficially resembles predatorytheropod dinosaurs, with jaws lined by finely serrated and slightly curved teeth well-adapted to a carnivorous diet, possibly preying on small vertebrates and soft invertebrates, it is in fact an early member of the otherwise-herbivorousSauropodomorpha, the group that gave rise to the giantsauropods.[1] Characteristically sauropodomorph traits seen inBuriolestes include a downturned jaw tip and a long deltopectoral crest on thehumerus. However,Buriolestes also lacks a small head and enlarged nostrils,[2] which are typical among sauropodomorphs, and themedial condyle on the end of its tibia projects backwards, a distinctive feature (autapomorphy) unique to this animal.[1]
InBuriolestes, the shaft of thepubis is straight, in contrast to later sauropodomorphs, where it has been modified into an expanded "apron", theropods, where it forms a "boot," and allornithischians, where it is reversed and is parallel to theischium. Additional traits differentiateBuriolestes from both later and contemporary sauropodomorphs: the front expansion (preacetabular ala) of theilium is relatively tall, the outer edges of the pubis are bevelled, thetrochanter of the femur forms a shelf, and themetatarsal of the fifth digit on the foot is relatively long.[1]
Skeletally mature specimens ofBuriolestes exhibit intraspecific variation through size disparity, with one robust individual weighing over 15.4 kg (34 lb) and others weighing between 6.4–7.2 kg (14–16 lb). This robust specimen is collected from the Piche site, which makes it the firstBuriolestes specimen outside the type locality.[5]
A 2020 study by Rodrigo T. Müller et al. that analysedBuriolestes' endocranial anatomy indicated a similar brain morphology to crocodiles. Furthermore, the well-developed optic lobe suggests thatBuriolestes was a sight-based predator, as its olfactory bulb was comparatively underdeveloped. The volume of the brain endocast additionally suggests a higherencephalisation quotient than sauropods such asDiplodocus,Nigersaurus, andBrachiosaurus. The well-developed flocculus is similar toSaturnalia, and the authors infer this to be the ancestral condition for sauropodomorpha.[6]
In 2022, Aureliano and colleagues performed a mirco-computed tomography scan on the postcranial skeletons of some of the earliest saurischian dinosaurs that lived during the lateCarnian includingGnathovorax with sauropodomorphsPampadromaeus andBuriolestes, which showed that the invasive air sac system was absent and that their bones were not pneumatised. These results indicate that pneumatisation in archosaur groups (pterosaurs,theropods andsauropodomorphs) are not homologous, but are traits that independently evolved at least 3 times.[7]
A phylogenetic analysis conducted in 2016 affirmed thesauropodomorph affinities ofBuriolestes. Part of the phylogenetic tree from the study is shown below.[1]
Five variants of phylogenetic analyses published earlier were used along with the description of the new specimens in 2018. One of these analyses, based on Langeret al. (2017)[8] placedBuriolestes in a clade of early sauropodomorphs, alongsideEoraptor,Panphagia,Pampadromaeus, andSaturnalia. Another analysis, which used the dataset ofBuriolestes' original description with the added parameter ofimplied weighting, placed it as the sister taxon toEoraptor, with theBuriolestes+Eoraptor clade sister to a clade connectingPanphagia andPampadromaeus. The other three analyses, which also corresponded to the original description's dataset, agreed with that study's placement ofBuriolestes as the single most basal sauropodomorph.[3]
The shape of the teeth ofBuriolestes suggest that it was a carnivore which fed on small vertebrates and invertebrates, which provides evidence thatsauropodomorphs - and likely allsaurischians anddinosaurs as a whole - were ancestrally carnivorous, and that sauropodomorphs,ornithischians, and various groups oftheropods independently became herbivorous.[1]
The co-occurrence ofBuriolestes andIxalerpeton parallels the simultaneous presence of dinosaurs and non-dinosaurdinosauromorphs at other sites (such as theIschigualasto[9] andChinle[10] Formations), suggesting that, after their initialevolutionary radiation, dinosaurs did not rapidly replace their dinosauromorph precursors.[1]
