Early sauropodomorph systematics have undergone numerous revisions during the last several years, and many scientists disagree where exactly Massospondylus lies on the dinosaur evolutionary tree.

[3] Owen erected three new species from this material based on differences in their supposed tail vertebrae: Massospondylus carinatus, Pachyspondylus orpenii, and Leptospondylus capensis.

Lydekker furthermore proposed that Owen's description was invalid and that his own publication should instead be considered the source of the name Massospondylus carinatus, and selected a neck vertebra and a toe bone as types (representative specimens on which a taxon is based on).

[9][8] At the beginning of World War II, the basements of the Hunterian Museum were strengthened to protect specimens from German bombing raids, and several collections were moved to remote locations.

[11] In 2004, Hans-Dieter Sues and colleagues provided a more comprehensive description of the same four skulls, and proposed the first diagnosis of Massospondylus carinatus (the set of distinguishing traits).

[12][8] The specimen, nicknamed "Big Momma" although its sex is unknown, was found in March 1980 on a farm near Clocolan, South Africa, by Lucas Huma and James Kitching.

[13] During the 21th century, two additional massospondylid genera were identified in southern Africa, raising the question of whether all of the previous identifications of Massospondylus specimens were correct.

In 2011, Yates and colleagues considered it to be a probable synonym of Massospondylus,[14] but cladistic analyses led by Kimberley Chapelle in 2018 and 2019 recovered it as a distinct taxon of massospondylid.

[12][15] The second genus, Ngwevu, was described in 2019 by Chapelle and colleagues based on a complete skull with a fragmentary skeleton that had been discovered in 1978 and was previously assigned to Massospondylus carinatus.

This species was based on two neck, two back, and three tail vertebrae as well as femora and toe bones that were discovered north of the Witteberg by Mr. Alfred Brown.

[25][8]: 173–174  One year later, in 1912, Broom erected Gryponyx transvaalensis from two foot bones (an ungual and a metatarsal) discovered in the Bushveld Sandstone Formation in Limpopo Province.

[29][8]: 173–174  Aristosaurus erectus was named by van Hoepen in 1920 based on a nearly complete skeleton of a small and potentially juvenile individual found by quarry workers in the Clarens Formation near Rosendal.

[36] A single autapomorphy (distinguishing feature) is found in the skull: the basipterygoid processes, a pair of bony extensions that braces the braincase against the palate, form an angle of ca.

[24] In 1986, Crompton and Attridge described skulls of Massospondylus as possessing pronounced overbites and suggested the presence of a horny beak on the tip of the lower jaw to make up the difference in length.

[24] The distal (front) end of the pubis was expanded in side view, but this expansion affected only its posterior margin, while the bone was flat anteriorly, which is an autapomorphy.

[8]: 119, 165  The forelimbs were only half the length of the hind limbs[40] but quite powerful, as indicated by a broad flange on the upper portion of the humerus called the deltopectoral crest, which provided attachment areas for a large arm musculature.

Owen, however, did not recognize the finds as dinosaurian, and instead attributed them to "large extinct carnivorous Reptiles" of uncertain classification, noting similarities with crocodilians, lizards, and dinosaurs.

[9] In 1914, von Huene instead erected a new family, Massospondylidae, to accommodate M. carinatus, M. harriesi, and Aetonyx palustris, but in 1932 returned to his former classification of Massospondylus within Thecodontosauridae.

[45] Galton and Upchurch (2004) included Ammosaurus, Anchisaurus, Azendohsaurus, Camelotia, Coloradisaurus, Euskelosaurus, Jingshanosaurus, Lessemsaurus, Lufengosaurus, Massospondylus, Melanorosaurus, Mussaurus, Plateosaurus, Riojasaurus, Ruehleia, Saturnalia, Sellosaurus, Thecodontosaurus, Yimenosaurus and Yunnanosaurus in a monophyletic Prosauropoda.

Scientists speculate that Massospondylus could have used its large pollex (thumb) claw in combat, to strip plant material from trees,[40] digging, or for grooming.

[60] Gastroliths (gizzard stones) have been found in association with three Massospondylus fossils from the Forest-Sandstone in Zimbabwe,[61] and with a Massospondylus-like animal from the Late Triassic of Virginia.

[55] Until recently, scientists believed that these stones functioned as a gastric mill to aid ingestion of plant material, compensating for its inability to chew, as it is the case in many modern birds.

However, Wings and Sander (2007) showed that the polished nature and the abundance of those stones precluded a use as an effective gastric mill in most non-theropod dinosaurs, including Massospondylus.

However, a recent discovery shows that Massospondylus possessed well-developed clavicles that were joined in a furcula-like arrangement, acting like a clasp between the right and left shoulder blades and prohibiting any rotation of these bones.

[10] This was contradicted in a recent study, noting that only the basalmost cervicals show inclined zygapophyses, allowing sufficient horizontal movement of the neck as a whole.

[67] The eggshells were very thin (about 0.1 mm), allowing gas exchange even in a low oxygen and carbon dioxide rich environment, which indicates that the eggs were at least partly buried in the substrate.

[56] This discovery therefore "sheds some light in the evolutionary pathways through which the peculiar adaptations of giant dinosaurs were attained", stated French paleontologist Eric Buffetaut.

[68] Many saurischian dinosaurs possessed vertebrae and ribs that contained hollowed-out cavities (pneumatic foramina), which reduced the weight of the bones and may have served as a basic 'flow-through ventilation' system similar to that of modern birds.

One study in 2007 concluded that basal sauropodomorphs like Massospondylus likely had abdominal and cervical air sacs, based on the evidence for them in sister taxa (theropods and sauropods).

[73] The 6-metre-(20 ft-) long[78] carnivorous theropod Dracovenator lived during the same period (Hettangian to Sinemurian stages) as Massospondylus and has also been found in the Elliot Formation of South Africa.