Pliosaurs
| Pliosaurs | ||||||||||||
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Live artistic representation of Plesiopleurodon |
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| Temporal occurrence | ||||||||||||
| Rhaetium ( Upper Triassic ) to Maastrichtian ( Upper Cretaceous ) | ||||||||||||
| 208.5 to 66 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Pliosauroidea | ||||||||||||
| Welles , 1943 |
The pliosaurs (Pliosauroidea) are a group of extinct marine reptiles that lived from the late Upper Triassic to the end of the Cretaceous and became extinct at the same time as the dinosaurs . In the Jurassic and the Cretaceous they were the dominant marine predators and occupied a similar position in the food pyramid as the theropods at the same time in terrestrial ecosystems. They belong to the plesiosaurs and differ from the plesiosaurs in the strict sense ( Plesiosauroidea ) mainly by their generally larger heads and shorter necks.
The name Pliosaurus ( Greek pleion - "more"; Greek sauros - "lizard") was coined in 1842 by Richard Owen , an important naturalist of the Victorian age , and means something like "more lizard". Owen gave the name because he assumed that the fossils available to him were closer to the lizards and represented a transitional form between crocodiles and the other marine reptiles known until then (plesiosaurs and ichthyosaurs ).
features
Pliosaur reached body lengths of 3 ( umoonasaurus ) to 12 ( Kronosaurus , Liopleurodon ) or 15 meters as of 2006 to Spitsbergen from the team led by Jørn Hurum found Pliosaurus funkei . The so-called " Monster of Aramberri ", a fragmentary fossil that was found in 1984 by a student in the La Casita Formation ( Kimmeridgium ) near Aramberri in Nuevo León , Mexico , possibly even reached a total length of 20 meters.
Head and neck
The head of the pliosaur was large and could reach a length of about three meters in large forms such as Kronosaurus , almost a quarter of the total length. The small brain was only 1% of body weight. The skull and flat snout were extended, the mandibular symphysis longer than in Plesiosauroidea. The mouth was studded with strong, conical fangs that were structured and keeled by a vertical groove, had broad bases and often showed signs of wear at the tip. The teeth of the plesiosaurs (plesiosaurs in the narrow sense ), on the other hand, are often narrow and needle-like, typical for fish-eaters. The premaxillary of the pliosaurs was occupied with 5 pairs of teeth, in the lower jaw there were 25 to 40 pairs of teeth.
The eyes were relatively large and surrounded by a scleral ring, which enabled the animals to keep the eyeballs in shape, as their large eyes were exposed to varying water pressures while swimming. The part of the eyes that is closer to the muzzle was exposed to greater water pressure than the one further back. The nostrils, closer to the eyes than the tip of the snout, were small - too small to be used for breathing. Breathing was probably on the surface of the water with the mouth open. Pliosaurs could swim with their mouths slightly open, small amounts of water flowed through openings in the roof of the mouth, past the olfactory organs and exited through the outer nostrils.
The neck was short and thick in most cases, the number of cervical vertebrae was still over twenty in most forms, and the short necks were supported by vertebrae with short vertebral bodies. Later, the number of cervical vertebrae was reduced to only 13 in more advanced forms, for example in Brachauchenius , the genus with the shortest neck, which measured only 75% of the head length.
limbs
As an adaptation to the aquatic way of life, the extremities of the pliosaurs had developed fins up to 3 meters long. The four limbs were long, with the femur (thighbone) longer than the humerus (humerus), and both bones were mostly longer than those of comparable sized plesiosauroidea. In the course of the evolution of these specialized limbs, there was an increase in finger bones ( hyperphalangia ) with up to 16 individual bones in one digit. Laterally flattened vertebrae in the caudal spine of Archaeonectrus suggest that it and perhaps other pliosaurs had a vertical caudal fin.
Way of life
Pliosaurs were inhabitants of the open ocean and their skull and jaw anatomy was adapted to hunt larger prey, to snap shut with great force and to hold onto the prey. Biomechanical studies suggest that the skull and jaws were strong enough to make vigorous twisting motions that could tear meat from their prey, similar to what is still the case with crocodiles today. The prey was detected visually or olfactorily . An echolocation , as with the toothed whales , was not possible for them because the ears were not acoustically isolated from the skull and spatial hearing was therefore impossible.
Their prey may have included large bony and cartilaginous fish , large cephalopods , including ammonites , ichthyosaurs and smaller plesiosaurs. In the body region of a Pliosaurus brachyspondylus fossil, three horn scales underlaid with osteoderms were found that came from an armored ornithic , i.e. an ankylosaur or stegosaur . This Pliosaurus probably ate from a dead dinosaur floating in the sea shortly before its own death. Pachycostasaurus had a hard-built skeleton, similar to today with manatees can be found who spend much of their time eating on seagrass beds. Like other pliosaurs, it had typical carnivorous teeth. Since the skull, however, slightly built and had a fight with a big prey too fragile, it is believed, is that Pachycostasaurus by midsize benthic fish, crustaceans and cephalopods fed does.
Like all plesiosaurs, the pliosaurs were almost certainly viviparous (live-bearing) and only gave birth to one or a few young per litter.
External system
The pliosaurs belong to the plesiosaurs (Plesiosauria). Their sister group are the Plesiosauroidea (plesiosaurs in the sense ), which were rather long-necked and had short heads. Together with a few species-poor groups from the Triassic , the Plesiosauria form the group of the fin lizard (Sauropterygia), which are probably related to today's scaled crawfish (Squamata), i.e. the lizards and snakes, than the dinosaurs and the pterosaurs .
Internal system
The pliosaurs are divided into two sub-taxa , which have the rank of families in the classical systematics : The Pliosauridae , medium-sized and large pliosaurs with large skulls and long snouts, and the Rhomaleosauridae , small to large pliosaurs with smaller skulls, shorter snouts and longer necks with 26 to 30 vertebrae. Brachauchenius and Kronosaurus are classified by some authors within a third family, the Brachauchenidae, which phylogenetically belongs to the Pliosauridae and thus makes them paraphyletic . There are also some basic genera with a more or less unclear systematic position.
The following cladogram comes from the first description of Marmornectes from 2011, a Pliosaurid from Great Britain.
| Pliosauroidea |
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- Pliosauroidea
Remarks
swell
literature
- Michael J. Benton : Paleontology of the vertebrates. Translation of the 3rd English edition by Hans-Ulrich Pfretzschner. Pfeil, Munich 2007, ISBN 978-3-89937-072-0 .
- Richard Ellis : Sea Dragons. Predators of the Prehistoric Oceans. University Press of Kansas, Lawrence KS 2003, ISBN 0-7006-1269-6 .
Individual evidence
- ↑ Ben Creisler: Plesiosauria Translation and Pronunciation Guide. Archived from the original on July 10, 2011 ; Retrieved July 9, 2012 .
- ^ Ellis 2003, p. 166.
- ↑ a b Sea reptile is biggest on record . BBC News, Feb. 27, 2008.
- ↑ Marie-Celine Buchy, Eberhard Frey , Wolfgang Stinnesbeck, José Guadalupe López-Oliva: First occurrence of a gigantic pliosaurid plesiosaur in the late Jurassic (Kimmeridgian) of Mexico. In: Bulletin de la Societe Geologique de France. Vol. 174, No. 3, 2003, ISSN 0037-9409 , pp. 271-278, doi : 10.2113 / 174.3.271 .
- ↑ Ellis 2003, p. 169 and 172.
- ^ Ellis 2003, p. 183.
- ↑ a b Palaeos: Pliosauroidea .
- ↑ a b c The Plesiosaur Directory: Pliosauroidea .
- ^ Alfred Sherwood Romer : Vertebrate Paleontology. 3rd edition, 4th imprint. The University of Chicago Press, Chicago IL 1974, ISBN 0-226-72488-3 , p. 196.
- ^ Ellis 2003, p. 168.
- ^ Benton 2007, page 41.
- ^ Ellis 2003, p. 172.
- ^ Ellis 2003, p. 166.
- ↑ Ellis 2003, pp. 170-171.
- ^ Ellis 2003, p. 191.
- ^ Frank R. O'Keefe, Luis M. Chiappe : Viviparity and K-Selected Life History in a Mesozoic Marine Plesiosaur (Reptilia, Sauropterygia). In: Science . Vol. 333, No. 6044, 2011, pp. 870-873, doi : 10.1126 / science.1205689 .
- ^ Benton 2007, p. 419.
- ^ Ellis 2003, p. 192.
- ^ A b Hilary F. Ketchum, Roger BJ Benson: A new pliosaurid (Sauropterygia, Plesiosauria) from the Oxford Clay Formation (Middle Jurassic, Callovian) of England: evidence for a gracile, longirostrine grade of Early-Middle Jurassic pliosaurids. In: Special Papers in Palaeontology. Vol. 86, 2011, ISSN 0038-6804 , pp. 109-129, online .
- ^ The Plesiosaur Directory: Pliosauridae
- ^ Sven Sachs and Benjamin P. Kear. 2017. A Rare New Pliensbachian Plesiosaurian from the Amaltheenton Formation of Bielefeld in northwestern Germany. Alcheringa. DOI: 10.1080 / 03115518.2017.1367419
- ↑ Zulma Gasparini: A New Oxfordian Pliosaurid (Plesiosauria, Pliosauridae) in the Caribbean Seaway. In: Palaeontology. Vol. 52, No. 3, 2009, ISSN 0031-0239 , pp. 661-669, doi : 10.1111 / j.1475-4983.2009.00871.x .
- ^ The Plesiosaur Directory: Rhomaleosauridae
Web links
- The Paleobiology Database: Pliosauroidea