Branchierpeton: a small gilled temnospondyl of Pangaea

Branchierpeton was a small dissorophoid temnospondyl in the family Micromelerpetidae. Its fossils are known from Central Europe and, following the description of B. saberi, Morocco. Some exceptionally preserved specimens retain impressions interpreted as external gills. These remains show an aquatic animal, but developmental changes make it difficult to compare juveniles and adults by size alone. It is one of the distinct early tetrapod lineages in the ancient amphibian catalogue.

Quick facts

A small temnospondyl, not a salamander

Branchierpeton belongs to Micromelerpetidae, a family within Dissorophoidea among temnospondyl amphibians. These were early tetrapods with varied body plans and life histories. Some micromelerpetids had long trunks and tails, small limbs and aquatic adaptations that can look salamander-like in reconstructions. The resemblance does not place them within modern Caudata; it reflects a separate branch of tetrapod evolution.

The genus has a long taxonomic history. Its species have been distinguished using combinations of skull proportions, ornament on the skull roof and postcranial characters. However, the anatomy changed as individuals grew. Juvenile bones may be less ossified and have different proportions from those of larger animals. A small fossil is not automatically a distinct small species.

The genus-level record includes species named from European localities and the Moroccan B. saberi. The number and validity of species have been revised as researchers compared new specimens and growth stages. The most useful approach is to keep each described species and locality attached to its own evidence rather than treating all specimens as one uniform population.

External gills and development

Some well-preserved fossils retain delicate branching impressions beside the back of the head. Researchers interpret these as external gills. Unlike a reconstruction based only on related animals, an actual impression provides direct evidence that soft gill structures were present in that individual when it was buried. Their precise colour, vascular pattern and movement are not preserved.

External gills indicate aquatic respiration during at least part of the animal’s life. In many living amphibians, gills characterize larvae, but some salamanders retain larval traits into adulthood. For Branchierpeton, deciding between delayed metamorphosis and paedomorphosis requires evidence about maturity, not just a gill trace. Skeletal ossification and size can help, yet do not by themselves establish reproductive status.

Fossil samples that include different body sizes offer a way to study growth. Changes in skull proportions, vertebral ossification and limb development may separate stages of one species from genuinely different taxa. Direct eggs or a complete reproductive sequence have not been tied securely to the genus, so breeding season, clutch size and parental care remain unknown.

From European lakes to Carboniferous Morocco

Central European fossils come from fine-grained deposits that preserve small skeletons and, in some cases, soft-tissue traces. Such settings were freshwater environments where rapid burial could protect delicate remains. The sediments describe the place of preservation, while local water conditions and seasonal changes remain broader environmental interpretations.

In 2019, fieldwork in Late Carboniferous, Kasimovian continental beds of Morocco’s Souss Basin produced two small micromelerpetid skeletons. The authors named them Branchierpeton saberi, diagnosing the species with a combination of cranial characters and distinct humerus and interclavicle shapes. This represented the first African record of Micromelerpetidae and an early documented tetrapod occurrence in the Maghreb.

The Moroccan fossils suggest that small, primarily aquatic temnospondyls could disperse across regions of late Paleozoic Pangaea. They do not reveal the route, timing or frequency of migration. A broad geographic distribution is consistent with movement through connected habitats, but a pair of skeletons cannot map the dispersal process by itself.

Feeding and reconstruction limits

The small teeth and body size fit feeding on modest aquatic prey such as invertebrates or small vertebrates. No stomach contents establish a particular food list for the genus. Claims about active pursuit, ambush tactics or a specific prey species go beyond the preserved evidence.

The reconstructed body uses the known elongated proportions, short limbs and long tail of micromelerpetids. External gills are included where supported by fossil impressions. Skin pattern, colour, eye appearance and exact swimming motion are not preserved. Unlike a giant river temnospondyl such as Archegosaurus, Branchierpeton represents a much smaller aquatic form whose life history is best understood through growth and gill evidence.

Its record matters both for anatomy and biogeography. Rare gill impressions preserve a feature that usually disappears, and the Moroccan species widened the map of a family once known chiefly from Europe. At the same time, the changing skeleton through growth cautions against making taxonomic decisions from size or one incomplete bone.