Cynodont - Wikipedia
CynodontFrom Wikipedia, the free encyclopedia (Redirected from
)Suborder of Therapsids
("dog teeth") (
that first appeared in the
). The cynodonts include modern
) as well as their extinct ancestors and close relatives, but not all cynodonts were mammals.
named Cynodontia in 1861, which he assigned to
as a family.
(1913) reranked Cynodonia as an infraorder, since retained by others, including Colbert and Kitching (1977), Carroll (1988), Gauthier
(1989), and Rubidge and
Olson (1966) assigned Cynodontia to Theriodonta, Colbert and Kitching (1977) to
, and Rubridge and Sidor (2001) to
William King Gregory
(1910), Broom (1913), Carroll (1988), Gauthier
(1989), Hopson and Kitching (2001) and Botha
(2007) all considered Cynodontia as belonging to Therapsida. Botha
(2007) seems to have followed Owen (1861), but without specifying taxonomic rank.
James Allen Hopson
e.a. defined a
Cynodontia as the most inclusive group containing
needs additional citations for
Evolution of mammals
from the Early Triassic of South Africa
Together with the extinct
, the cynodonts themselves are part of a group of therapsids called
The oldest and the most basal cynodont yet found is
). Other basal cynodonts were the
, a family that includes
. Cynodonts were among the few groups of synapsids that survived the
Permian–Triassic extinction event
and had a slow recovery after the extinction.
The most derived cynodonts are found within the
, which also contains the members of
. Representative genera of nonmammalian cynodonts include the large
, the equally large herbivorous
, and the small mammal-like
. The presence of
suggests a rapid metabolism and possibly
, the number of cynodont
bones reduced. This move towards a single bone for the mandible paved the way for other bones in the jaw, the
, to migrate to the cranium, where they function as parts of the mammalian hearing system.
Cynodonts also developed a
in the roof of the mouth. This caused air flow from the nostrils to travel to a position in the back of the mouth instead of directly through it, allowing cynodonts to chew and breathe at the same time. This characteristic is present in all mammals.
Early cynodonts have many of the skeletal characteristics of
. The teeth were fully differentiated and the braincase bulged at the back of the head. Outside of some
mammals (notably the
), all cynodonts probably laid eggs. The
were much larger than those of their ancestors, and the widening of the
in a more mammal-like skull would have allowed for more robust jaw musculature. They also have the
that other primitive therapsids lacked, except the
, who were the closest relatives of cynodonts. (However, the secondary palate of cynodonts primarily comprises the maxillae and palatines as in mammals, whereas the secondary palate of the therocephalians primarily comprises the maxillae and the vomer.) The
was the largest bone in their lower jaw.
The cynodonts probably had some form of
metabolism. This has led to many reconstructions of cynodonts as having
. Being endothermic they may have needed it for
, but fossil evidence of their fur (or lack thereof) has been elusive. Modern mammals have
secreting lipids to coat their fur, but the telltale imprint of this structure is only found from the
Nonetheless, recent studies on
show that more basal therapsids had fur,
and at any rate fur was already present in
Marks in the upper and lower jaw of cynodonts have been interpreted as channels that supplied blood vessels and nerves to
Whiskers may have been typical of cynodontia as a whole, or have evolved in this group.
Derived cynodonts developed
bones. These served to strengthen the torso and support abdominal and hindlimb musculature, aiding them in the development of an erect gait, but at the expense of prolonged pregnancy, forcing these animals to give birth to highly altricial young as in modern
, and perhaps
, would lose these.
A specimen of
does indeed demonstrate that at least tritylodontids already had a fundamentally marsupial-like reproductive style, but produced much higher litters at around 38 perinates or possibly eggs.
Cynodonts are the only known synapsid lineage to have produced aerial locomotors, with gliding and flying being known in
and various mammal groups.
Below is a
from Ruta, Botha-Brink, Mitchell and Benton (2013) showing one hypothesis of cynodont relationships:
Cynodonts have been found in South America, India, Africa, Antarctica
and North America
Permian–Triassic extinction event
Triassic-Jurassic extinction event
Classification of R. Owen 1861
Classification of B. S. Rubidge and C. A. Sidor 2001
R. Broom. 1913. A revision of the reptiles of the Karroo. Annals of the South African Museum 7(6):361–366S. H. Haughton and A. S. Brink. 1954. A bibliographical list of Reptilia from the Karroo Beds of South Africa. Palaeontologia Africana 2:1–187James A. Hopson and James W. Kitching, 2001, "A Probainognathian Cynodont from South Africa and the Phylogeny of Nonmammalian Cynodonts" pp 5-35 in: PARISH A. JENKINS, JR., MICHAEL D. SHAPIRO, AND TOMASZ OWERKOWICZ, EDITORS, STUDIES IN ORGANISMIC AND EVOLUTIONARY BIOLOGY IN HONOR OF A. W. CROMPTON Bullettin of the Museum of Comparative Zoology. Harvard University 156(1)Ruben, J.A.; Jones, T.D. (2000).
"Selective Factors Associated with the Origin of Fur and Feathers"
. American Zoologist. 40 (4): 585–596.
"Microbiota and food residues including possible evidence of pre-mammalian hair in Upper Permian coprolites from Russia". Lethaia.
.Brink, A.S. (1955). "A study on the skeleton of Diademodon". Palaeontologia Africana. 3: 3–39.Kemp, T.S. (1982). Mammal-like reptiles and the origin of mammals. London: Academic Press. p. 363.
.Michael L. Power, Jay Schulkin. The Evolution of the Human Placenta. pp. 68–.Jason A. Lillegraven, Zofia Kielan-Jaworowska, William A. Clemens, Mesozoic Mammals: The First Two-Thirds of Mammalian History, University of California Press, 17 December 1979 – 321Eva A. Hoffman; Timothy B. Rowe (2018). "Jurassic stem-mammal perinates and the origin of mammalian reproduction and growth". Nature. 561 (7721): 104–108. doi:10.1038/s41586-018-0441-3.
.Qing-Jin Meng; David M. Grossnickle; Di Liu; Yu-Guang Zhang; April I. Neander; Qiang Ji; Zhe-Xi Luo (2017). "New gliding mammaliaforms from the Jurassic". Nature. in press. doi:10.1038/nature23476.Ruta, M.; Botha-Brink, J.; Mitchell, S. A.; Benton, M. J. (2013).
"The radiation of cynodonts and the ground plan of mammalian morphological diversity"
. Proceedings of the Royal Society B: Biological Sciences. 280 (1769): 20131865.
.Abdala, Fernando; Ribeiro, Ana Maria (2010).
"Distribution and diversity patterns of Triassic cynodonts (Therapsida, Cynodontia) in Gondwana"
. Palaeogeography, Palaeoclimatology, Palaeoecology. 286 (3–4): 202–217.Lucas, Spencer G. (2001).
Chinese Fossil Vertebrates
New York City
: Columbia University Press. p. 133.
. Retrieved 30 November 2019.Fraser, Nicholas C.; Sues, Hans-Dieter (1997). In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods. Cambridge University Press.Sues, Hans-Dieter; Olsen, Paul E.; Carter, Joseph G. (1999).
"A Late Triassic Traversodont Cynodont From the Newark Supergroup of North Carolina"
(PDF). Journal of Vertebrate Paleontology. 19 (2).Further reading[
]Hopson, J.A.; Kitching, J.W. (2001). "A probainognathian cynodont from South Africa and the phylogeny of non-mammalian cynodonts". Bull. Mus. Comp. Zool. 156: 5–35.Davis, Dwight (1961). "Origin of the Mammalian Feeding Mechanism". Am. Zoologist, 1:229–234.External links[
Phylogeny of Theriodonts and Cynodonts
Bennett and Ruben 1986. The Metabolic and Thermoregulatory Status of Therapsids
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Extant Permian first appearances
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