Acteosaurus

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Acteosaurus
Temporal range: 99.6–89.3  Ma
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Clade: Pythonomorpha
Genus: Acteosaurus
Meyer, 1860
Species
  • Acteosaurus tommasinii type Meyer, 1860
  • (?)A. crassicostatus Calligaris, 1993

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. [1]

Contents

Etymology

The primary portion of Acteosaurus' name comes from Actaeon ( /ækˈtən/ ; Greek: Άκταίων), 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 magistrateof Trieste under the Habsburgs. [2]

Taxonomy

Hermann von Meyer (1801-1869) Hermann von Meyer.jpg
Hermann von Meyer (1801-1869)

As a genus, Acteosaurus was described in 1860 by German paleontologist Christian Erich Hermann von Meyer. 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". [1] This included the Dolichosauridae, Pontosaurus , Aphanizocnemus , and Adriosaurus . Acteosaurus was found to be a basal ophidiomorph (similar to Adriosaurus) and sister taxon to the Ophidia, or modern snakes. [1]

Description

Acteosaurus is described as slender or snake-like, similar to other dolichosaurids. [3] Its shortened forelimbs and long tail help to distinguish it from other genera, and its vertebral column is similar to more modern varanid lizards. [3]

The holotype, when it was discovered, was unfortunately missing its head. [3] 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 arches 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 forelimbs of Acteosaurus are fully developed, they are smaller than the hind limbs. [2] Acteosaurus' pelvic bone is flattened, has square-shaped pubic process, and a rectangular descending ramus. [1]

Distribution and habitat

The Istrian peninsula Istria.png
The Istrian peninsula

Both Acteosaurus tommasinii and A. crassicostatus were found in the upper section of karst Cenomanian platy limestone, in Komen, Slovenia. [2] [4] Komen is part of Istria, a peninsula on the Adriatic sea, and also a section of the Karst Plateau. During the late Cretaceous, most of Europe was an island chain in the Tethys ocean, [5] and Acteosaurus' aquatic nature and similarity to mosasauroids suggests that it lived on the coast of one of these islands. [2]

See also

Related Research Articles

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Ophidia is a group of squamate reptiles including modern snakes and all reptiles more closely related to snakes than to other living groups of lizards.

Mosasaur Extinct marine lizards of the Late Cretaceous

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<i>Antarctosaurus</i> Sauropod dinosaur genus from Late Cretaceous

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<i>Aeolosaurus</i> Extinct genus of dinosaurs

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<i>Cetiosauriscus</i> Genus of reptiles (fossil)

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<i>Nipponosaurus</i> Hadrosaurid dinosaur genus from Late Cretaceous Japan

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Pythonomorpha Clade of lizards

Pythonomorpha was originally proposed by paleontologist Edward Drinker Cope (1869) as a reptilian order comprising mosasaurs, which he believed to be close relatives of Ophidia (snakes). The etymology of the term Pythonomorpha comes from the Greek Python and morphe ("form"), and refers to the generally serpentine body plan of members of the group. Cope wrote, "In the mosasauroids, we almost realize the fictions of snake-like dragons and sea-serpents, in which men have been ever prone to indulge. On account of the ophidian part of their affinities, I have called this order Pythonomorpha." Cope incorporated two families, the Clidastidae and the Mosasauridae.

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Judeasaurus is an extinct genus of small, aquatic varanoid lizard related to the mosasauroids. The only known specimen is from the Late Cretaceous of the Middle East, though its exact provenance is uncertain.

<i>Adriosaurus</i> Extinct genus of lizards

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<i>Kaganaias</i> Extinct genus of lizards

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Anguimorpha Order of lizards

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<i>Eupodophis</i> Extinct genus of snakes

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<i>Tethysaurus</i> Extinct genus of lizards

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<i>Yaguarasaurus</i> Extinct genus of lizards

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Andreas Kornhuber

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References

  1. 1 2 3 4 Palci, Alessandro; Caldwell, Michael (2010). "Redescription of Acteosaurus tommasinii von Meyer, 1860, and a discussion of evolutionary trends within the clade Ophidiomorpha". Journal of Vertebrate Paleontology. 30: 94–108. doi:10.1080/02724630903409139.
  2. 1 2 3 4 Wright, T. (1860). "On the Subdivisions of the Inferior Oolite in the South of England, compared with the Equivalent Beds of that Formation on the Yorkshire Coast". Quarterly Journal of the Geological Society. 16: 1–48 [35, 31]. doi:10.1144/GSL.JGS.1860.016.01-02.06.
  3. 1 2 3 Gorjanovic-Kramberger, Carl. Trans, John D. Scanlon. AIGIALOSAURUS: A new lizard from the Cretaceous slates of the Island of Lesina with consideration of the previously described lacertids of Comen and Lesina. 1892"Rad" der südslavischen Akademie der Kunst und der Wissenschaft 109: 96-123, Pl. I, II.
  4. Jurkovšek, Bogdan; Kolar-Jurkovšek, Tea (2007). "Fossil assemblages from the Upper Cretaceous Komen and Tomaj Limestones of Kras (Slovenia)" (PDF). Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 245: 83–92. doi:10.1127/0077-7749/2007/0245-0083.
  5. "Dinosaurs Rule the World: Late Cretaceous Period." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. Pp. 103-104. ISBN   0-7853-0443-6.