''Prolacerta'' is a genus of archosauromorph from the lower

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

and

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...

. The only known species is ''Prolacerta broomi''. The generic name ''Prolacerta'' is derived from

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

meaning “before lizard” and its species name ''broomi'' is in commemoration of the famous

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

Robert Broom Robert Broom FRS FRSE (30 November 1866 6 April 1951) was a British- South African doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University of Glasgow. From 1903 to 1910, he ...

, who discovered and studied many of the

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s found in rocks of the

Karoo Supergroup The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a peri ...

. When first discovered, ''Prolacerta'' was considered to be ancestral to modern

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...

s, scientifically known as lacertilians. However, a study by Gow (1975) instead found that it shared more similarities with the lineage that would lead to

archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avia ...

s such as

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...

ns and

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s (including

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s). ''Prolacerta'' is considered by modern paleontologists to be among the closest relatives of the Archosauriformes.

History of discovery

''Prolacerta'' was first described by Francis Rex Parrington in 1935 from a single skull recovered near the small town, Middelburg, in the

Eastern Cape The Eastern Cape is one of the provinces of South Africa. Its capital is Bhisho, but its two largest cities are East London and Gqeberha. The second largest province in the country (at 168,966 km2) after Northern Cape, it was formed in ...

. The fossil was recovered from an exposure of rock from the Katberg Formation in the ''Lystrosaurus'' Assemblage Zone. At the time, Parrington described the first ''Prolacerta'' fossil, the early

evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...

ary relationships of

s was even more poorly understood than they are currently. Due to its small size and lizard-like appearance, Parrington subsequently placed ''Prolacerta'' between basal younginids and modern lizards. Parrington's classification of ''Prolacerta'' was accepted for several decades, including by the paleontologist

Charles Lewis Camp Charles Lewis Camp (March 12, 1893 Jamestown, North Dakota – August 14, 1975 San Jose, California) was a palaeontologist and zoologist, working from the University of California, Berkeley. He took part in excavations at the ' Placerias Quarry', ...

who conducted further research on ''Prolacerta''. It was only after more ''Prolacerta'' fossils were found that more in depth research was undertaken on this animal. In the 1970s the close link between ''Prolacerta'' and crown

s was first hypothesized, which lead to numerous

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

analyses being conducted on ''Prolacerta'' and other stem archosaurs from the 1980s onwards.

Description

''Prolacerta'' were small

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchocephalia ...

s that lived during the

Induan The Induan is the first age of the Early Triassic epoch in the geologic timescale, or the lowest stage of the Lower Triassic series in chronostratigraphy. It spans the time between 251.902 Ma and Ma (million years ago). The Induan is someti ...

and

Olenekian In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian is sometimes divided i ...

stages of the lower

. ''Prolacerta'' is arguably the most well-represented stem-

archosauriform Archosauriformes (Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Latest Permian (roughly 252 million years ago). It was defined by Jacques Gauthier ...

, with numerous well preserved specimens housed in various research institutions in

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, and in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

. With the skull of adult specimens ranging between 8 – 10 cm in length, ''Prolacerta'' were considered to have been small, lizard-like animals. However, several

cranial Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

and

postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...

l features set ''Prolacerta'' apart from lizards and instead show that it is an early relative of crown-

s. Some of these notable features include elongated

cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...

with elongate, thickened

neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

, which gave ''Prolacerta'' a slightly elongated neck and a wide range of flexibility.

Cranial Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

features include thecodont teeth, a feature observed in all ancestors of crown

s, which were pointed and

caniniform In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. They can appear more flattened however ...

in shape. ''Prolacerta'' was probably a small, active, terrestrial

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other s ...

insectivore A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores were ...

due to its fang-like teeth of roughly the same size and shape. ''Prolacerta'' is considered to have been a

quadruped Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattuor' ...

, although due to its hind limbs being larger and longer than its front limbs, there is a possibility that it was habitually

bipedal Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...

during high activity. It has been hypothesized that ''Prolacerta'' was capable of cranial kinesis, although research into this possible feature of ''Prolacerta'' remains inconclusive.

Classification

Initially hypothesized to be ancestral to lizards, ''Prolacerta'' was later identified as an archosauromorph by Gow (1975). Gow placed it into a group known as the Prolacertiformes, which also contained "protorosaurs" such as '' Protorosaurus'', ''

Macrocnemus ''Macrocnemus'' is an extinct genus of archosauromorph reptile known from the Middle Triassic (Late Anisian to Ladinian) of Europe and China. ''Macrocnemus'' is a member of the Tanystropheidae family and includes three species''. Macrocnemus ba ...

'', and the long-necked tanystropheids. ''Macrocnemus'' and a few other "prolacertiforms" were allied with ''Prolacerta'' in the family Prolacertidae. However, later studies starting with Dilkes (1998) have split apart the concept of Prolacertiformes, with protorosaurs being placed near the base of Archosauromorpha and ''Prolacerta'' being much closer to Archosauriformes. Prolacertidae was also split by this reassessment, with ''Macrocnemus'' now considered a tanystropheid. Currently, Prolacertidae is restricted to ''Prolacerta'' and its close Australian cousin '' Kadimakara''. Prolacertids are confidently considered to be archosauromorphs within the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

Crocopoda, along with the allokotosaurs,

rhynchosaur Rhynchosaurs are a group of extinct herbivorous Triassic archosauromorph reptiles, belonging to the order Rhynchosauria. Members of the group are distinguished by their triangular skulls and elongated, beak like premaxillary bones. Rhynchosaurs ...

s, and archosauriforms. The following

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

is based on a large analysis of archosauriforms published by M.D. Ezcurra in 2016

References

{{Taxonbar, from1=Q28647877, from2=Q3922862 Prehistoric archosauromorphs Prehistoric reptile genera Induan genera Olenekian genera Early Triassic reptiles of Africa Triassic South Africa Fossils of South Africa Prehistoric reptiles of Antarctica Triassic Antarctica Fossils of Antarctica Fossil taxa described in 1935 Taxa named by Francis Rex Parrington