''Procynosuchus'' (Greek: "Before dog crocodile") is an extinct genus of

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s from the Late

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...

. It is considered to be one of the earliest and most basal cynodonts. It was 60 cm (2 ft) long. Remains of ''Procynosuchus'' have been found in

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

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and

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.T. S. Kemp: ''The Origin and Evolution of Mammals'' Oxford University Press, 2005.

Paleobiology

As one of the earliest cynodonts, ''Procynosuchus'' has many primitive features, but it also has features that distinguish it from all other early therapsids. Some of these features were interpreted by Kemp (1980) as adaptations for a semi-aquatic lifestyle. For example, the wide zygapophyses of the vertebrae allow for a high degree of lateral flexibility, and ''Procynosuchus'' may have used

anguilliform locomotion Fish locomotion is the various types of animal locomotion used by fish, principally by swimming. This is achieved in different groups of fish by a variety of mechanisms of propulsion, most often by wave-like lateral flexions of the fish's body a ...

, or eel-like undulation, to swim through the water. The tail of ''Procynosuchus'' is also unusually long for a cynodont. The long

haemal arch A haemal arch, also known as a chevron, is a bony arch on the ventral side of a tail vertebra of a vertebrate. The canal formed by the space between the arch and the vertebral body is the haemal canal. A spinous ventral process emerging from the ha ...

es would have given the tail a large lateral surface area for greater propulsion through the water. Relatively flat foot bones may also have been an adaptation toward swimming, as the feet may have been used like paddles. Ridges on the femur are an indication of strong flexor muscles that could have stabilized the leg during limb-driven swimming. When the thigh is pulled back in the water, the lower leg tends to bend forward. Strong flexor muscles would have pulled the lower leg back with the femur, providing the powerful backward thrust that is needed to swim.

Discovery

Diictodon galeops and Procynosuchus delaharpae models

''Procynosuchus'' was named by South African paleontologist

Robert Broom Robert Broom Fellow of the Royal Society, FRS FRSE (30 November 1866 6 April 1951) was a British- South African medical doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University ...

in 1937. Broom also named the cynodont ''Cyrbasiodon'' in 1931. Another genus, ''Parathrinaxodon'', was named by Parrington in 1936. These genera are now regarded as synonyms of ''Procynosuchus'', as they represent the same animal. Under the

International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted Convention (norm), convention in zoology that rules the formal scientific name, scientific naming of organisms treated as animals. It is also informally known as the I ...

(ICZN), these two names take precedence over ''Procynosuchus'' because they were erected earlier. The names ''Cyrbasiodon'' and ''Parathrinaxodon'' were rarely used after their erection, while the name ''Procynosuchus'' has since become widespread in scientific literature. In a case brought to the ICZN in 2009, some scientists proposed that ''Procynosuchus'' should be a ''nomen conservandum'', or

conserved name A conserved name or ''nomen conservandum'' (plural ''nomina conservanda'', abbreviated as ''nom. cons.'') is a scientific name that has specific nomenclatural protection. That is, the name is retained, even though it violates one or more rules wh ...

, making ''Cyrbasiodon'' and ''Parathrinaxodon'' ''nomina rejecta'', or rejected names. In 2010, the ICZN formally made ''Procynosuchus'' a ''nomen conservandum''.

References

External links

Cynodontia

{{Taxonbar, from=Q134240 Cynodontia Lopingian life Transitional fossils Lopingian synapsids of Europe Permian Germany Fossils of Germany Permian Russia Fossils of Russia Lopingian synapsids of Africa Permian South Africa Fossils of South Africa Permian Tanzania Fossils of Tanzania Fossil taxa described in 1937 Taxa named by Robert Broom