Claudiosaurus
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''Claudiosaurus'' (''claudus'' is Latin for 'lameness' and ''saurus'' means 'lizard') is an extinct
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
of
diapsid Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years ...
reptiles from the
Permian The Permian ( ) is a geologic period and 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 251.9 Mya. It is the last period of the Pale ...
Sakamena Formation of the Morondava Basin,
Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
. The pattern of the vertebrate, girle, and limbs indicates that ''Claudiosaurus'' and '' Thadeosaurus'' share a common ancestor.


History and discovery

''Claudiosaurus'' is known from the Sakamena Formation of Madagascar. ''Claudiosaurus'' is found from the
Late Permian Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...
. Although a paper mentions that they have been also found in
Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a ...
deposits of Madagascar, citation does not mention that ''Claudiosaurus'' is from Triassic.


Biology and description

''Claudiosaurus'' was one of the first members of the
Neodiapsida Neodiapsida is a clade, or major branch, of the reptilian family tree, typically defined as including all diapsids apart from some early primitive types known as the araeoscelidians. Modern reptiles and birds belong to the neodiapsid subclade S ...
, a group of reptiles containing diapsids more derived than the primitive Araeoscelidia. It had a relatively long body and neck, reaching on overall length of about . It is presumed to have been partially
ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth and contains 97% of Earth's water. An ocean can also refer to any of the large bodies of water into which the wo ...
ic, living its life in a way similar to the modern
marine iguana The marine iguana (''Amblyrhynchus cristatus''), also known as the sea iguana, saltwater iguana, or Galápagos marine iguana, is a species of iguana found only on the Galápagos Islands (Ecuador). Unique among modern lizards, it is a marine repti ...
. The main reason for this theory is that the skeleton included substantial amounts cartilage, instead of
bone A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, an ...
, indicating it had trouble supporting its weight on land. In particular, the
sternum The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. ...
was poorly developed, which would have made walking difficult out of water. Instead, it probably swam by undulating its body and tail, and holding its legs close to the body to increase streamlining. A more recent study however indicates that its vertebral column tail and leg proportions are closer to those of terrestrial reptiles, though it is noted that
marine iguana The marine iguana (''Amblyrhynchus cristatus''), also known as the sea iguana, saltwater iguana, or Galápagos marine iguana, is a species of iguana found only on the Galápagos Islands (Ecuador). Unique among modern lizards, it is a marine repti ...
s similarly only differ from terrestrial counterparts very subtly. The mean vertebral is approximately twice of '' Hovasaurus''. ''Claudiosaurus'' have a more slender tail than '' Hovasaurus''. The frontal contributes the dorsal orbital margin. This prevents the prefrontal from contacting the post frontal. The post frontal is ventrally expanded posteriorly and contributes to the orbital rim. The anterior process of the pterygoid is straight. The closest skull comparison can be with the genus ''
Anarosaurus ''Anarosaurus'' is an extinct genus of pachypleurosaurs that lived in the Middle Triassic period (Anisian) and has been found in the Jena Formation and the Karlstadt Formation of Germany and the Winterswijk Quarry ( Lower Muschelkalk) of The Neth ...
''. ''Claudiosaurus'' differs from '' Acerosodontosaurus'' and ''Hovasaurus'' in the presence of a proportionately long neck.


Behavior


Locomotion

It is theorized that ''Claudiosaurus'' was semi-aquatic. The discovery of pachyostotic thickening of the limb bones and vertebrae supports this theory. The margins of contact in the carpals are poorly defined and therefore retained a lot of cartilage, providing a greater ‘degree of flexibility’ that would be beneficial for swimming.


Feeding ecology

There is evidence of aquatic feeding habits. Supporting this is the small size of the skull, nature of the palate and marginal dentition and the long neck.


Classification

''Claudiosaurus'' is recovered as a relative of turtles by Li ''et al.'' (2018), forming a clade with the basal neodiapsid '' Acerosodontosaurus''. Although another study in 2020 specifically disputed these conclusions.


Paleoenvironment

The Lower Sakamamena Formation was deposited in a wetland environment situated within a North-South orientated
rift valley A rift valley is a linear shaped lowland between several highlands or mountain ranges created by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear de ...
, perhaps similar to
Lake Tanganyika Lake Tanganyika () is an African Great Lake. It is the second-oldest freshwater lake in the world, the second-largest by volume, and the second-deepest, in all cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. T ...
. The climate at the time of deposition was temperate, warm, and humid, with seasonal rainfall and possible monsoons. Flora from the formation includes the equisetalean '' Schizoneura'', the glossopterid gymnosperm ''
Glossopteris ''Glossopteris'' tymology: from Ancient Greek γλῶσσα (glôssa, " tongue ") + πτερίς (pterís, " fern ")is the largest and best-known genus of the extinct Permian order of seed ferns known as Glossopteridales (also known as Arber ...
'', and seed fern '' Lepidopteris.'' Other vertebrates known from the Lower Sakamena Formation include the palaeoniscoid fish '' Atherstonia'', the
procolophonid Procolophonidae is an extinct family of small, lizard-like parareptiles known from the Late Permian to Late Triassic that were distributed across Pangaea, having been reported from Europe, North America, China, South Africa, South America, Antar ...
parareptile '' Barasaurus'', the gliding
weigeltisaurid Weigeltisauridae is a family of gliding neodiapsid reptiles that lived during the Late Permian, between 258 and 252 million years ago. Fossils of weigeltisaurids have been found in Madagascar, Germany, Great Britain, and Russia. A possible weigelt ...
reptile '' Coelurosauravus'', the neodiapsids '' Hovasaurus, Thadeosaurus'', and '' Acerodontosaurus'', fragments of
rhinesuchid Rhinesuchidae is a family of tetrapods that lived primarily in the Permian period. They belonged to the broad group Temnospondyli, a successful and diverse collection of semiaquatic tetrapods which modern amphibians are probably descended from. ...
temnospondyls, an indeterminate
theriodont The theriodonts ( clade Theriodontia) are a major group of therapsids which appeared during the Middle Permian and which includes the gorgonopsians and the eutheriodonts, itself including the therocephalians and the cynodonts. Naming In 1876, R ...
therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented mor ...
and the
dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivorous animals with a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typica ...
'' Oudenodon''.


References


Further reading

* * * * * {{Taxonbar, from=Q2703352 Prehistoric neodiapsids Lopingian reptiles of Africa Lopingian genera Fossils of Madagascar Permian Madagascar Fossil taxa described in 1981 Prehistoric reptile genera