| Efraasia | |
|---|---|
 | |
| Reconstructed skull | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Bagualosauria |
| Genus: | †Efraasia Galton, 1973 |
| Type species | |
| †Efraasia minor (von Huene, 1907–1908 [originallyTeratosaurus minor]) | |
| Synonyms | |
| |
Efraasia (pronounced "E-FRAHS-ee-A") is agenus ofbasalsauropodomorphdinosaur. It was aherbivore which lived during the middleNorian stage of theLate Triassic, around 210 million years ago, in what is nowGermany. It was named in 1973 afterEberhard Fraas, who during the early twentieth century collected what were the originaltype specimens. The specimens were at first assigned to three already existing genera and so became divided among three separate species:Teratosaurus minor,Sellosaurus fraasi andPaleosaurus diagnosticus. In 2003, these were combined into a single valid species:Efraasia minor.[1]Efraasia was a lightly built, medium-sized sauropodomorph, about 6 to 7 metres (20 to 23 ft) long.
Efraasia has had a complicatedtaxonomic history involving several genera and species. Material now known underEfraasia first came to light after Albert Burrer,Hofsteinmetzmeister ("Court master stonemason") atMaulbronn, in 1902 began to exploit theWeiße Steinbruch, a quarry nearPfaffenhofen inWürttemberg. To reach the layer of hard whitesandstone Burrer wanted to use for his building projects a 6 metres (20 ft) thickoverburden of softermarl had to be removed. Many vertebrate fossils proved to be present in it. Thisstratum was part of theStubensandstein Member of the lowerLöwenstein Formation, dating to theNorian. From 1906 until 1914 when the quarry closed, Burrer donated the finds topaleontologist Professor Fraas of thekönigliche Stuttgarter Naturalienkabinett.
A specimen of a basal sauropodomorph, SMNS 11838, was first described byFriedrich von Huene in 1907–1908 and named as a new species ofTeratosaurus:T. minor. At the time,Teratosaurus was thought to be atheropod dinosaur; it was only established as arauisuchian non-dinosaur in the 1980s. Thespecific name referred to the fact that the specimen was smaller thanTeratosaurus suevicus. The fossils consisted of a fewvertebrae from the hip, the right hindlimb, and apubic bone. Elsewhere in the same publication he gave the nameSellosaurus fraasi to a partial skeleton, SMNS 12188-12192, from slightly older rocks of the same formation, as a second species of his new genusSellosaurus (the genus is today considered to be a synonym ofPlateosaurus).[2]
In 1912,Eberhard Fraas reported on two partial skeletons, SMNS 12667 and SMNS 12684 collected in 1909, which he assigned to a new species ofThecodontosaurus:T. diagnosticus.[3] He would never describe them due to his failing health, and thus this name remained anomen nudum. Von Huene adopted the specific name years later, after Fraas' death, redescribing Fraas' specimens asPaleosaurus (?) diagnosticus in 1932.[4] The question mark indicates that von Huene considered the reference as provisional only. In 1959Oskar Kuhn pointed out that the namePaleosaurus Riley & Stutchbury 1836 was preoccupied and renamed the genusPalaeosauriscus.[5]Allen Charig in 1967 was the first to use the combinationPalaeosauriscus diagnosticus for the German material.[6] However, the new generic name was itself a junior homonym ofPalaeosauriscus fraserianus Cope 1878.
Peter Galton reassigned Fraas' specimens to the new genusEfraasia in 1973, becausePalaeosaurus, apart from the homonymy problems, was a nondiagnostic tooth genus. The generic name was a contraction of "E. Fraas". The new species name combination thus becameEfraasia diagnostica.[7] However, Galton andRobert Bakker later (1985) recommended thatEfraasia be considered ajunior synonym of anotherprosauropod,Sellosaurus gracilis.[8][9]
In 2003,Adam Yates published a study incorporating these and other fossils from the Late Triassic of Germany.[10] He found that the "Sellosaurus" material fell into two clusters. One included the originalSellosaurus gracilis, which he assigned toPlateosaurus asP. gracilis. The other included "Teratosaurus"minor, "Sellosaurus"fraasi, and "Palaeosaurus"diagnosticus.Efraasia was the oldest valid generic name for these fossils. The specific name could not be determined as simply, as bothTeratosaurus minor andSellosaurus fraasi had first appeared in von Huene's 1908 book. Because the former name had page priority, Yates choseminor as the specific name, providing for thetype speciesTeratosaurus minor the new combinationEfraasia minor, which is thus the single valid species name of thetaxon.[9] Yates did not take into account two other species based by von Huene on very fragmentary German basal sauropodomorph material,Teratosaurus trossingensis andThecodontosaurus hermannianus, though Galton had considered them junior synonyms ofEfraasia diagnostica in 1990.[11]
Apart from the specimens mentioned above, mostly consisting of rather complete skeletons preserved in large slabs, though not fully prepared from the rock matrix, several other fossils have been found. Together they allow for a good impression of what the animal looked like.
Efraasia was once thought to be a relatively small dinosaur, about 2 to 3 metres (6.6 to 9.8 ft) long, but this was because the most complete known fossils are from juvenile animals. Yates in 2003 has estimated the adult length at 6.5 metres (21 ft); the largest specimen is SMNS 12843 with afemur length of 627 millimetres (24.7 in).Efraasia was lightly built for its size, with gracile hands and feet. Like many "primitive" sauropodomorphs,Efraasia might have been partially bipedal and partly quadrupedal. It had long fingers and mobile thumbs, with which it would have been able to grasp food, but the shape of its wrists might have allowed it to walk easily on all fours.[12] Some researchers however, contend that the lower arm did not allowpronation, a rotation of theradius around theulna, so that the hand could not be directed downward, making the animal an obligate biped.
The skull is small, pointed and triangular. There are four teeth in thepremaxilla. The neck is only moderately elongated but thin. The neural spines of the tail are low. The second finger is longer than the third finger. The first toe is not strongly reduced. Von Huene identified a cluster of stomach stones (gastroliths) in association to specimen SMNS 12667.
Yates identifies two unique derived traits (autapomorphies): the presence of a raised crescent-like ridge on the upper part of the inner side of the pubis shaft; and the presence of a vaulted bony web between two lower extensions of a braincase bone, theprocessus basipterygoidei, with a raised central bony platform on top of the vault.
Von Huene continued interpreting these forms as predatory dinosaurs, in 1932 assigning them to a separate family,Palaeosauridae, as part of theCarnosauria. Only in 1965, Charig established they were plant-eating sauropodomorphs.[13]
In 1973, Galton assignedEfraasia to theAnchisauridae, but he used this name as aparaphyletic group encompassing all "prosauropods" that were notmelanorosaurids. Modernphylogenetic analysis has indicated thatEfraasia is a basal sauropodomorph, somewhat more derived thanThecodontosaurus, but less than either theProsauropoda (includingPlateosaurus) or theSauropoda. The genus is sometimes recovered as the sister taxon to thelast common ancestor of both larger groups.
