Gaiasia

Gaiasia Temporal range: Early Permian, ~280 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Skull diagram
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Sarcopterygii
Clade:	Tetrapodomorpha
Genus:	†Gaiasia Marsicano et al., 2024
Species:	†G. jennyae
Binomial name
†Gaiasia jennyae Marsicano et al., 2024

Gaiasia is an extinct genus of stem-tetrapods from the Early Permian of Namibia, containing a single species, Gaiasia jennyae. Gaiasia was a freshwater predator which was exceptional among stem-tetrapods for its combination of relatively enormous size, Southern occurrence, and late survival.^[1]

Gaiasia is known from three fossil specimens, including an incomplete skeleton with a crushed skull and partial vertebral column. Though limb material is not preserved, the skull of Gaiasia indicates that its affinities lie with digit-bearing stem-tetrapods (early amphibians, in the broad sense). It was a close relative to the colosteids, a family of aquatic stem-tetrapods with long bodies and small limbs. Most digit-bearing stem-tetrapods, including the colosteids, go extinct by the Carboniferous rainforest collapse near the end of the preceding Carboniferous Period. Gaiasia is one of the few to survive into the Permian alongside crown-tetrapods (the groups directly ancestral to living amphibians, mammals, and reptiles).^[1]

Gaiasia is the largest known digit-bearing stem-tetrapods, with an estimated maximum skull length reaching 60 centimetres (24 in). It was found in the Gai-As Formation, a rock unit corresponding to cold temperate lake environments located near the South Pole (around 55° South) in the Permian. Other digit-bearing stem tetrapods were significantly smaller (skulls under 40 centimetres (16 in) in length), and nearly all were restricted to the tropics of Euramerica, a low-latitude region equivalent to present-day Europe and North America. Gaiasia hints that stem-tetrapods in Southern latitudes continued to persist and evolve through the Late Paleozoic icehouse interval, even as low-latitude species died out and were supplanted by crown-tetrapods.^[1] Gaiasia's genus name references the Gai-As Formation, while the species name honors the late Jenny Clack, an expert in early tetrapods.^[1][2]