Acteosaurus
Encyclopedia
Acteosaurus is an extinct
genus
of aquatic lizard
that lived in the upper Cretaceous period. Its species, A. tommasinii and A. crassicostatus, were described in 1860 and 1993. Though A. crassicostatus is probably a junior synonym for Adriosaurus suessi
, A. tommasinii was found to be similar to coniasaurs, mosasauroids, and a sister taxon to modern snakes in 2010.
(icon; Greek: ), a famous Theban
hero
who was hunted and killed by the goddess
Artemis
. The second part of the name is the Greek
word sauros (σαυρος), which means "lizard
" or "reptile
". The type species was named after the botanist Muzio Giuseppe Spirito de Tommasini
(1794—1879), the Podestà
—or magistrate—of Trieste
under the Habsburgs.
. There exist two known species of Acteosaurus: A. crassicostatus and A. tommasinii. The latter is the type species
, while A. crassicostatus was discovered in 1993.
A 2010 redescription of the type species found "monophyly
of the clade
Ophidiomorpha". This included the Dolichosauridae, Pontosaurus
, Aphanizocnemus
, and Adriosaurus
. Acteosaurus was found to be a basal ophidiomorph (similar to Adrisaurus) and sister taxon to the Ophidia, or modern snakes.
The holotype
, when it was discovered, was unfortunately missing its head. So, while Meyer was unable to come up with an exact number, he noted that Acteosaurus has at least 10 cervical vertebrae
, and 27 dorsals
. There are small articular processes
on the trunk vertebrae, and it has long, narrow neural spines, and posteroventrally
positioned, unfused haemal arch
es on the vertebrae of the tail. There is no pachyostosis
, or bone thickening, in the vertebrae and ribs. The limbs are reduced in size, and though the forelimb
s of Acteosaurus are fully developed, they are smaller than the hind limbs. Acteosaurus pelvic bone is flattened, has square-shaped pubic process, and a rectangular descending ramus.
Both Acteosaurus tommasinii and A. crassicostatus were found in the upper section of karst
Cenomanian
platy limestone
, in Komen
, Slovenia
. Komen is part of Istria
, a peninsula on the Adriatic sea
, and also a section of the Kras plateau. During the late Cretaceous, most of Europe was an island chain in the Tethys ocean
, and Acteosaurus aquatic nature and similarity to mosasauroids suggests that it lived on the coast of one of these islands.
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of aquatic lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
that lived in the upper Cretaceous period. Its species, A. tommasinii and A. crassicostatus, were described in 1860 and 1993. Though A. crassicostatus is probably a junior synonym for Adriosaurus suessi
Adriosaurus
Adriosaurus is an extinct genus of aquatic lizard that lived about 95 million years ago. It was snake-like and grew 10 to 12 inches. This is the first fossil record of vestigial limbs in lizards, and gives scientists a glimpse back to the time when terrestrial lizards evolved to be limbless...
, A. tommasinii was found to be similar to coniasaurs, mosasauroids, and a sister taxon to modern snakes in 2010.
Etymology
The primary portion of Acteosaurus name comes from ActaeonActaeon
Actaeon , in Greek mythology, son of the priestly herdsman Aristaeus and Autonoe in Boeotia, was a famous Theban hero. Like Achilles in a later generation, he was trained by the centaur Chiron....
(icon; Greek: ), a famous Theban
Thebes, Greece
Thebes is a city in Greece, situated to the north of the Cithaeron range, which divides Boeotia from Attica, and on the southern edge of the Boeotian plain. It played an important role in Greek myth, as the site of the stories of Cadmus, Oedipus, Dionysus and others...
hero
Hero
A hero , in Greek mythology and folklore, was originally a demigod, their cult being one of the most distinctive features of ancient Greek religion...
who was hunted and killed by the goddess
Goddess
A goddess is a female deity. In some cultures goddesses are associated with Earth, motherhood, love, and the household. In other cultures, goddesses also rule over war, death, and destruction as well as healing....
Artemis
Artemis
Artemis was one of the most widely venerated of the Ancient Greek deities. Her Roman equivalent is Diana. Some scholars believe that the name and indeed the goddess herself was originally pre-Greek. Homer refers to her as Artemis Agrotera, Potnia Theron: "Artemis of the wildland, Mistress of Animals"...
. The second part of the name is the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word sauros (σαυρος), which means "lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
" or "reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
". The type species was named after the botanist Muzio Giuseppe Spirito de Tommasini
Mutius von Tommasini
Muzio Giuseppe Spirito de' Tommasini, sometimes referred to as Muzio Tommasini or as Mutius von Tommasini; was a botanist and politician born in Trieste under Austria-Hungary....
(1794—1879), the Podestà
Podestà
Podestà is the name given to certain high officials in many Italian cities, since the later Middle Ages, mainly as Chief magistrate of a city state , but also as a local administrator, the representative of the Emperor.The term derives from the Latin word potestas, meaning power...
—or magistrate—of Trieste
Trieste
Trieste is a city and seaport in northeastern Italy. It is situated towards the end of a narrow strip of land lying between the Adriatic Sea and Italy's border with Slovenia, which lies almost immediately south and east of the city...
under the Habsburgs.
Taxonony
As a genus, Acteosaurus was described in 1860 by German paleontologist Christian Erich Hermann von MeyerChristian Erich Hermann von Meyer
Christian Erich Hermann von Meyer was a German palaeontologist.He was born at Frankfurt am Main.In 1832 von Meyer issued a work entitled Palaeologica, and in course of time he published a series of memoirs on various fossil organic remains: molluscs, crustaceans, fishes and higher vertebrata,...
. There exist two known species of Acteosaurus: A. crassicostatus and A. tommasinii. The latter is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, while A. crassicostatus was discovered in 1993.
A 2010 redescription of the type species found "monophyly
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
of the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Ophidiomorpha". This included the Dolichosauridae, Pontosaurus
Pontosaurus
Pontosaurus is a now extinct genus of pythonomorph from the Late Cretaceous period. It was originally named Hydrosaurus, but that name was preoccupied by an agamid lizard, so it was renamed....
, Aphanizocnemus
Aphanizocnemus
Aphanizocnemus is an extinct genus of varanoid lizard from Lebanon. It is a marine lizard that lived during the Late Cretaceous. It is often classified in the family Dolichosauridae as a close relative of snakes, although some studies have placed it as an even closer relative to snakes than...
, and Adriosaurus
Adriosaurus
Adriosaurus is an extinct genus of aquatic lizard that lived about 95 million years ago. It was snake-like and grew 10 to 12 inches. This is the first fossil record of vestigial limbs in lizards, and gives scientists a glimpse back to the time when terrestrial lizards evolved to be limbless...
. Acteosaurus was found to be a basal ophidiomorph (similar to Adrisaurus) and sister taxon to the Ophidia, or modern snakes.
Description
Acteosaurus is described as slender or snake-like, similar to other dolichosaurids. Its shortened forelimbs and long tail help to distinguish it from other genera, and its vertebral column is similar to more modern varanid lizards.The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
, when it was discovered, was unfortunately missing its head. So, while Meyer was unable to come up with an exact number, he noted that Acteosaurus has at least 10 cervical vertebrae
Cervical vertebrae
In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...
, and 27 dorsals
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
. There are small articular processes
Articular processes
The articular processes or zygapophyses of a vertebra, two superior and two inferior, spring from the junctions of the pedicles and laminæ...
on the trunk vertebrae, and it has long, narrow neural spines, and posteroventrally
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
positioned, unfused haemal arch
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 on the vertebrae of the tail. There is no pachyostosis
Pachyostosis
Pachyostosis is a condition in vertebrate animals in which the bones experience a thickening, resulting in unusually solid bone structure with little to no marrow. It occurs in both terrestrial and aquatic vertebrates, such as manatees and dugongs, plesiosaurs, and members of the Dinocephalia...
, or bone thickening, in the vertebrae and ribs. The limbs are reduced in size, and though the forelimb
Forelimb
A forelimb is an anterior limb on an animal's body. When referring to quadrupeds , the term foreleg is often instead used....
s of Acteosaurus are fully developed, they are smaller than the hind limbs. Acteosaurus pelvic bone is flattened, has square-shaped pubic process, and a rectangular descending ramus.
Distribution and habitat
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
Cenomanian
Cenomanian
The Cenomanian is, in the ICS' geological timescale the oldest or earliest age of the Late Cretaceous epoch or the lowest stage of the Upper Cretaceous series. An age is a unit of geochronology: it is a unit of time; the stage is a unit in the stratigraphic column deposited during the corresponding...
platy limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
, in Komen
Komen
Komen is a settlement and a municipality in Slovenia. It is located on the Kras plateau in the Slovenian Littoral.-History:In the Middle Ages, it was first part of the Duchy of Friuli and in the 13th century it was included in the County of Gorizia. Komen was first mentioned in a document from 1247...
, Slovenia
Slovenia
Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...
. Komen is part of Istria
Istria
Istria , formerly Histria , is the largest peninsula in the Adriatic Sea. The peninsula is located at the head of the Adriatic between the Gulf of Trieste and the Bay of Kvarner...
, a peninsula on the Adriatic sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...
, and also a section of the Kras plateau. During the late Cretaceous, most of Europe was an island chain in the Tethys ocean
Tethys Ocean
The Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.-Modern theory:...
, and Acteosaurus aquatic nature and similarity to mosasauroids suggests that it lived on the coast of one of these islands.
See also
- List of Mosasaurs
- EidolosaurusEidolosaurusEidolosaurus was a genus of mosasauroid from the Late Cretaceous period....
- Introrsisaurus
- PontosaurusPontosaurusPontosaurus is a now extinct genus of pythonomorph from the Late Cretaceous period. It was originally named Hydrosaurus, but that name was preoccupied by an agamid lizard, so it was renamed....
External links
- http://paleodb.org/cgi-bin/bridge.pl?action=checkTaxonInfo&taxon_no=36381&is_real_user=1Acteosaurus at the Paleobiology DatabasePaleobiology Database' is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.-History:The Paleobiology Database was founded in 2000. It has been funded by the National Science Foundation and the Australian Research Council...
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