Microbrachis pelikani (Fritsch 1875) Middle Pennsylvanian, Late Carboniferous ~300 mya, ~15 cm in length, was originally and subsequently considered a microsaur and a sister to Utaherpeton. Here Microbrachis was derived from a sister to Utegenia and phylogenetically preceded the microsaurs, Pantylus, Ptyonius and Scincosaurus.
Distinct from Utegenia, the skull of Microbrachis had a larger orbit and sharper teeth. The tabular and supratemporal remained distinct and unfused. The frontals were narrower. The prefrontal and postfrontal met over each orbit. The internal nares were smaller. The dentary produced a coronoid process and the dentary tip was elevated. The pterygoids extended to the cheeks.
40 presacral vertebrae were present, up from 26 in Pantylus. The tail was larger on larger specimens, just the opposite of the tadpole condition in frogs.
The pectoral girdle was poorly ossified. The limbs were shorter and less robust, nearly vestigial. The manus included only three digits.
The pelvis was smaller overall with a more erect ilium. The hind limb was also short with poorly ossified tarsals.
Microbrachis retained larval gills into adulthood. The present skull reconstruction differs from that of Vallin and Laurin (2004). |
