Blikanasaurus: the Triassic sauropodomorph with a heavy foot

Blikanasaurus cromptoni is a Late Triassic sauropodomorph from South Africa, known chiefly from the lower part of a hind leg and a foot. The foot is so short and broad that it has often been used to picture an early, heavily built quadruped. Yet the fossil includes neither the front limbs nor the backbone. A permanently four-legged posture is therefore not demonstrated by the type skeleton.

Quick facts

Expedition to Blikana Mountain

The holotype SAM-PK K403 was collected during a British–South African expedition in 1962 near the village of Blikana, about 25 kilometres east-southeast of Sterkspruit in South Africa’s Eastern Cape. The bones come from the Lower Elliot Formation. The age of this part of the formation has been discussed in regional stratigraphic work and is generally placed in the Late Triassic, around the Norian; precise placement can vary with the age model used.

Peter Galton and Jacques van Heerden named Blikanasaurus cromptoni in 1985. The genus name refers to the locality and the species name honours palaeontologist Alfred W. Crompton, who led field work on vertebrate fossils in the Elliot deposits. Before formal description, the remains had been known informally as the “Blikana dinosaur”.

The type is an associated lower hind limb and foot, preserving the tibia, fibula, ankle elements and much of the pes, with a few toe bones missing. A separate right first metatarsal, BP/1/5271a, was later referred to the genus from the Damplaats farm in the Free State. It is an isolated element rather than part of the articulated type. A possible ilium has also been proposed tentatively and should not be used as though it were securely diagnostic.

A remarkably robust foot

The first metatarsal is unusually broad, with its transverse width reported at roughly 90 per cent of its length. The third metatarsal is short relative to the tibia, while the claw-bearing first toe is longer than the first metatarsal. The upper end of the tibia is also expanded. Together these proportions make the known foot conspicuously more robust than those of many early sauropodomorphs.

This is direct evidence about the bones that were found. It supports the conclusion that the hind foot was built to bear substantial loads, but a robust foot alone does not determine the body mass or posture of the entire animal. The comparison with Massospondylus is informative because that animal preserves more of its skeleton, allowing posture to be assessed from several regions instead of one limb.

Family names and changing relationships

Galton and van Heerden established the family name Blikanasauridae for the genus, and some early interpretations placed it close to the first true sauropods. Later phylogenetic analyses have not consistently supported that exact position. Depending on the analysis and the anatomical sample, Blikanasaurus has been treated as a robust basal sauropodomorph or as a form closer to the sauropod line.

The problem is not simply that classifications change. The type preserves very little anatomy compared with a complete skeleton, and its most conspicuous feature – a stout foot – may be influenced by body support as well as shared ancestry. Similar proportions can evolve in separate branches. The genus is recognisable by the unusual hind-limb material, but its exact branch position remains less secure than its name and type specimen.

Work on the Lower Elliot Formation also cautions against combining every bone of similar size from different farms. The region contains several sauropodomorph forms. A second, isolated metatarsal was assigned to Blikanasaurus because of its small size and robust proportions, but it was collected in a surface scatter that may contain bones from more than one animal or taxon. Such material expands the record cautiously; it does not supply a second complete skeleton.

Locomotion without a settled answer

A short, broad foot is compatible with supporting a relatively heavy body and seems unlike the foot of a lightly built fast runner. This encouraged reconstructions of Blikanasaurus as a slow quadruped. But the forelimbs are absent, and they would be essential for demonstrating habitual support on all fours. A bipedal sauropodomorph with powerful hind limbs remains possible.

Trackways from Triassic deposits of similar age show that early sauropodomorphs used both bipedal and quadrupedal gaits. No trackway has been securely linked to Blikanasaurus, so those tracks describe the wider locomotor repertoire rather than this genus specifically. Neither speed nor total mass can be calculated reliably from the tibia and foot alone.

The fossils reveal no complete neck, forelimb or trunk. Plant eating is inferred from its position among sauropodomorphs and the broader anatomy of the group, rather than from preserved teeth or gut contents. Neck length, hand shape, skin, colour and other soft tissues are unknown. Any complete animal shown in a reconstruction combines the type foot with a conservative body plan borrowed from relatives.

Why this fragment matters

Blikanasaurus matters because it records a distinctive experiment in hind-foot construction among early sauropodomorphs. Its robust metatarsals help document the diversity of body-support strategies before the appearance of later giant sauropods. They do not, by themselves, prove that the genus was their direct ancestor or that it was already a fully quadrupedal sauropod.

A skull, forelimbs and more of the backbone would transform the comparison. Until such material is known, the clearest account separates the solid evidence – an associated lower hind limb and unusually stout foot – from less certain claims about posture and family placement. Other taxa and the limits of their evidence can be compared in the dinosaur catalogue.