Spathicephalus

Spathicephalus is an extinct genus of stem tetrapods (early four-limbed vertebrates) that lived during the middle of the Carboniferous Period. The genus includes two species: the type species S. mirus from Scotland, which is known from two mostly complete skulls and other cranial material, and the species S. pereger from Nova Scotia, which is known from a single fragment of the skull table. Based on the S. mirus material, the appearance of Spathicephalus is unlike that of any other early tetrapod, with a flattened, square-shaped skull and jaws lined with hundreds of very small chisel-like teeth. However, Spathicephalus shares several anatomical features with a family of stem tetrapods called Baphetidae, leading most paleontologists who have studied the genus to place it within a larger group called Baphetoidea, often as part of its own monotypic family Spathicephalidae. Spathicephalus is thought to have fed on aquatic invertebrates through a combination of suction feeding and filter feeding.

==History of study== The type species of Spathicephalus, S. mirus, was named by paleontologist D. M. S. Watson in 1929. Watson described seven fossil specimens from an outcrop of the Rumbles Ironstone in the town of Loanhead in Midlothian, Scotland. The ironstone dates to the late Namurian stage (earliest Upper Carboniferous) and is part of the Limestone Coal Group. These specimens were discovered in the 1880s and include a mostly complete skull with the palate exposed, an impression of the underside of a skull roof, a right portion of the back of a skull, and various jaw fragments. At the time, Spathicephalus and other tetrapods from the Namurian of Scotland were some of the oldest tetrapods known, predating the better-known Late Carboniferous tetrapod assemblages of the British Coal Measures. In November 1974, Scottish paleontologist Stanley P. Wood discovered additional skull and jaw fragments of Spathicephalus in an open-pit mine (the Dora Open Cast Mine) near the town of Cowdenbeath in Fife. Wood found these fossils in a layer of siltstone that is the same age as the ironstone in Loanhead.