Cisuralian in the context of "Paleocontinent"

William Diller Matthew FRS (February 19, 1871 – September 24, 1930) was a vertebrate paleontologist who worked primarily on mammal fossils, although he also published a few early papers on mineralogy, petrological geology, one on botany, one on trilobites, and he described Tetraceratops insignis, which was much later suggested to be the oldest known (Early Permian) therapsid.

Matthew was born in Saint John, New Brunswick, the son of George Frederic Matthew and Katherine (Diller) Matthew. His father was an amateur geologist and paleontologist who instilled his son with an abiding interest in the earth sciences. Matthew received an A.B. at the University of New Brunswick in 1889 and then earned his Ph.D. at Columbia University in 1894.

Mesosaurus (meaning "middle lizard") is an extinct genus of reptile from the Early Permian of southern Africa and South America. Along with it, the genera Brazilosaurus and Stereosternum, it is a member of the family Mesosauridae and the order Mesosauria. Mesosaurus was long thought to have been one of the first marine reptiles, although new data suggests that at least those of Uruguay inhabited a hypersaline water body, rather than a typical marine environment. In any case, it had many adaptations to a fully aquatic lifestyle. It is usually considered to have been anapsid, although Friedrich von Huene considered it to be a synapsid. Recent study of Mesosauridae phylogeny places the group as either the basal most clade within Parareptilia or the basal most clade within Sauropsida (with the latter being the less supported position) despite the skull of Mesosaurus possessing the "Synapsid condition" of one temporal fenestra.

The Guadalupian is the second and middle series/epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 274.4 ± 0.4 – 259.51 ± 0.21 Mya. The series saw the rise of the therapsids, a minor extinction event called Olson's Extinction and a significant mass extinction called the end-Capitanian extinction event. The Guadalupian is also known as the Middle Permian.

Palaeobranchiostoma hamatotergum is an extinct chordate from the Early Permian-aged Whitehill Formation in South Africa. It is known from a single, 11 mm long specimen found in black shale. The body shows the presence of a notochord-like structrure running along the length of the body, gill slits, and several unpaired fins, including a tail (caudal) fin with rays that is round and small, a pronounced pelvic fin and a humped dorsal fin covered in spikes. In its original description it was considered to be a cephalochordate (also known as a lancelet), though some other authors have considered its placement in the group as not definitive, due to a number of aspects of its anatomy like the fins being strongly divergent from living lancelets.

In the geologic timescale, the Artinskian is an age or stage of the Permian. It is a subdivision of the Cisuralian Epoch or Series. The Artinskian likely lasted between 290.1 and 283.3 million years ago (Ma) according to the most recent revision of the International Commission on Stratigraphy (ICS) in 2024. It was preceded by the Sakmarian and followed by the Kungurian.