Westlothiana: the small tetrapod called Lizzie

Westlothiana lizziae was a small, long-bodied tetrapod from Early Carboniferous Scotland, about 345 million years ago. Its outline looks lizard-like, but it lived long before true lizards appeared. Its place on the tree remains disputed: analyses have placed it either among the earliest amniotes or just outside that group. The near-complete skeleton is unusually informative, yet it cannot preserve the soft egg membranes that would settle the question. The ancient amphibian catalogue also includes early tetrapods whose place near this boundary remains debated.

Quick facts

“Lizzie” from East Kirkton

Scottish collector Stan Wood found the best-known skeleton in the 1980s at East Kirkton Quarry near Bathgate. It became known informally as “Lizzie” because its small body and long tail looked like those of a lizard. The nickname is not a statement about sex, which cannot be determined from the fossil. Timothy Smithson announced the animal in 1989, and Smithson and William Rolfe formally named Westlothiana lizziae in 1990.

The holotype, NMS G.1990.72.1, is split between a slab and counterslab and is held by National Museums Scotland. It preserves much more of one animal than most early tetrapod finds. A second skeleton was later described and helped test whether some apparent features of the holotype were genuine or the result of damage and compression.

The genus name refers to West Lothian. The species name follows the nickname Lizzie. There is one generally accepted species, so the taxonomic history is chiefly about its position among early tetrapods rather than a long list of named species.

A lizard-like body before lizards

The skull was small and low. The skeleton lacks the prominent otic notch found in many temnospondyls, and its teeth were small and conical rather than deeply folded. Numerous vertebrae supported a long trunk and tail. The limbs were short, with bones sufficiently ossified to suggest that they could bear weight against a firm surface.

The most complete specimen measures about 20 centimetres. That is the preserved animal's size, not a body length extrapolated from a relative. No larger individual is known, but a small fossil sample cannot establish a maximum size for the species. The tail's end and some fine details of the feet are also incomplete.

Near the amniote boundary

The first description interpreted several skull, vertebral and limb characters as evidence that Westlothiana was an early reptile, in the historical sense of an amniote. Later studies questioned some of those characters and found that others were shared more widely among reptiliomorphs. Current analyses therefore place it either on the amniote stem or close to, but outside, crown Amniota.

That distinction cannot be settled by its outline. The amniote egg and its membranes are not preserved, and bone anatomy supplies only indirect clues about reproductive biology. The later Hylonomus is usually treated as one of the earliest secure amniotes, but the two genera do not document a direct ancestor-descendant sequence. They represent different parts of a diverse early Carboniferous fauna.

Lake deposits and a possible way of life

East Kirkton limestone formed around a small lake in a volcanically active landscape. Mineral-rich hot springs entered the water, and the unusual chemistry helped preserve delicate fossils in fine sediment. The same locality contains other tetrapods, scorpions, millipedes, eurypterids and an early harvestman. Some terrestrial remains may have washed or fallen into the lake, so co-occurrence does not mean every animal lived in the water.

Westlothiana had relatively developed limbs and proportions compatible with life on land or along a shore. Small teeth make invertebrates a plausible food source, but no stomach contents identify prey. The broader transition is described in the account of vertebrates moving onto land; neither that context nor this skeleton proves a particular behaviour for Lizzie.

What a reconstruction must supply

The bones establish a small tetrapod with a long trunk and tail, short limbs and a compact skull. They do not preserve skin, colour, scales, eggs or soft organs. A scaly covering in artwork is a comparative choice, not a direct observation. Even if the animal was close to amniotes, it need not have had the same skin as a modern lizard.

The fossil's importance is not that it is a perfect “missing link”. It shows a distinctive animal near a major evolutionary boundary where soft-tissue traits are especially hard to recover. Its exact placement remains a question for anatomical comparisons, not something that its familiar silhouette can answer.