was a cynodont
Cynodontia or cynodonts are a taxon of therapsids which first appeared in the Late Permian and were eventually distributed throughout all seven continents by the Early Triassic . This clade includes modern mammals and their extinct close relatives. They were one of the most diverse groups of...
from the Late Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
. It is considered to be one of the earliest and most basal
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
cynodonts. Remains of Procynosuchus
have been found in Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
Zambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....
and South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. It was 60 cm (2 ft) long.
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 have been interpreted 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, 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 is a bony arch on the underside of a tail vertebra of a vertebrate.The hole so formed is the haemal canal.It sometimes has a haemal spine on.The blood vessels to and from the tail run through the arch....
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.
was named by South African paleontologist Robert Broom
Professor Robert Broom was a Scottish South African doctor and paleontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University of Glasgow...
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 is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...
(ICZN), these two names take precedence over Procynosuchus
because they were erected earlier. The names Cyrbasiodon
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 is a scientific name that has specific nomenclatural protection. Nomen conservandum is a Latin term, meaning a "name which should be conserved"...
, making Cyrbasiodon
and Parathrinaxodon nomina rejecta
, or rejected names. IN 2010, the ICZN formally made Procynosuchus
a nomen conservandum