Keichousaurus
hui
Reptilia:
Sauropterygia: Nothosauria: Pachypleurosauroidea
Triassic
Age (Scythian or early Triassic - the Spathian Age of China, 241.9 million
years ago - lasting for 0.2 million years)
Henan Province,
China
Dimensions:
10 in x 4 in
Keichousaurus is a Pachypleurosaur in the Nothosaur family. Its legs were in transition between land and water dwelling. It was not yet well adapted to aquatic life so it primary used its tail for propulsion and its legs as paddles. However, the bones in the limbs are very large when compared to other nothorsaurs, indicating that it spent considerable time on land, probably in marshy areas. It would not have been graceful due to its evolution for swimming.The Pachypleurosaurs were small, lightly built lizard-like reptiles, generally less than a meter (the smallest about 20 cm). They were clearly related to the Nothosaurs, with which they were contemporary. For a long time the Pachypleurosaurs were included with the Nothosaurs, and originally even placed under the same family Nothosauridae. It is now coming to be realised that they represent a distinct group that was only related, via a primitive Sauropterygian common ancestor. The neck is long but, unlike the Nothosauria the head is very small (like the eosuchian Claudiosaurus), so pachypleurosaurs probably fed on very small fish and crustacea. Relatively small dorsal temporal openings in the skull also clearly distinguish the Pachypleurosaurs from the Nothosaurian genera such as Lariosaurus, Ceresiosaurus, Corosaurus, Paranothosaurus and Simosaurus, in all of which the upper temporal openings are much larger than the orbits. The tail is deep and would have been used as a swimming organ. The legs were semi-flattened to serve as paddles, but the hips and shoulders were still powerful and functional enough to provide support on land. It is likely that these animals were able to crawl about on land like modern seals, dragging themselves by their strong forelimbs. As with the nothosaurids they were semi-aquatic forms, mostly lagoonal but also venturing out to sea, perhaps not unlike the modern marine iguana in that respect. Their small size meant however they probably did not venture out far, being primarily near-shore forms. 5 Keichousaurus shows the elongated skull and long serpentine neck and tail, and general features of the typical Pachypleurosaur. However the ulna (outermost bone of the foreleg/forearm) is massive, quite unlike that of any of the European genus (Young 1958) 5
Keichousaurus (KEE-chi-o-SAUR-us): The Keishousauridae were amphibious reptiles. They lived in a beach-like environment. They have a small body with a long neck and a triangle head bone with teeth in a single line. The eye bone is large and circular. The vertebral column consists of a neck section (22 vertebra); back section (19 vertebra); tail section (more than 37 vertebra). They were equipped with four legs with fin shaped hands and feet. 3 An early reptile that lived during the Triassic period, roughly 210 million years ago. Keishousaurus was about 6-11 inches (15-29 cm) long and had a long neck, a long tail, five-toed feet with long digits, and a pointed head with sharp teeth. It may have lived in the water. This quadruped had sturdy legs. Fossils have been found in Guanglin, Guizhou Province, China. 11 Discovered in mid-1957 this specimen represents the first marine dinosaur reptile fossil found that evolved into a separate genus in the China area. They are named after their discovery site near Tachai village in S.W. Keichow province. This first find of a primitive Asian Sauropterigia, clearly related to a European species, helped establish how the ancient Thethys Sea connected Europe and China by way of Asia Minor. 12
Functional analysis of swimming (drag-based rather than subaquatic flyer) & allometrics. (Rieppel, O. & Lin, K., 1998, 23, 24)
Pachypleurosauridae 5
Ecological niche - estuarine and near-shore marine carnivores
Habitat: estuarine, coastal marine, semiaquatic
Breeding: return to land to breed
Time and Place: Spathian of East Pangea (China)
Ladinian to early Carnian of the Tethys Sea
Ancestors: Claudiosauridae
Descendents: Nothosaurs, Pistosaurs
Food: small fish, crustacea
Enemies: large nothosaurs, large ichthyosaurs, sharks
Taxonomic status: official, paraphyleticThe two Chinese pachypleurosaurs, Keichousaurus and Hanosaurus, form two consecutive sister-groups to European pachypleurosaurs, strengthening the Asiatic affinities. (O Rieppel, Journal of Vertebrate Paleontology, 1998 - 22)
Pachypleurosauridae:
Range: mT (Anisian-Ladinian) of Eur, China. Phylogeny: Sauropterygia:::: Eusauropterygia + *.
Characters: S-M size (<1m). Similar to nothosaurs. Skull unusually small; jaws not elongated; pterygoids expanded to completely cover braincase ventrally; upper fenestra smaller than large orbit; strong upper bar; no lower fenestra; post-orbital skull short; quadrate embayed & slender stapes (impedence-matching ear for airborne vibrations & thus amphibious?); long (18 cervicals) neck; 3 sacral vertebrae; dorsoventral extension of vertebral spines near base of tail; dorsal verts have low neural spines, thickened and dense (pachyostosis -- see Notes); pachyostosis extends to ribs in more derived species; girdles poorly ossified (thus obligate marine?); limbs not highly derived for aquatic life; restricted to epicontinental & coastal areas. Appear to have originated in China (Keichousaurus is basal) and migrated to Europe via the northern border of Tethys Sea. 20The current belief is that Pachypleurosaur line forms part of the bridge between the Sauropterygian stem (e.g. Placodonts) and the Eusauropterygia (e.g. Plesiosaurs). The connection is an admittedly difficult one to make, but the fossil record gives few options. To make this phylogenetic region yet stranger, a prolonged stare at the pachypleurosaurs tends to bring turtles to mind -- yet another taxon of still-uncertain affinities. Look, for example, at the way the dorsal and caudal ribs seem to rise up above the level of the sacrum (the fused area of bone at the intersection of the pelvis and the spine) in the many available photographs of Keichousaurus. Turtles are the only group of vertebrates with both sets of limb girdles inside the rib cage. Yet it would take little modification to give this unique character to a pachypleurosaur. The pachyostosis of the ribs, from which the group derived its name, is similar to the broad, heavy ribs of turtles. Although pachypleurosaurs themselves are unarmored, one group of Placodonts has strikingly turtle-like armor. This relationship between Sauropterygians and turtles was widely defended at the end of the last century. It seemed to fall apart, on details of skull anatomy among other things. However, the concept has recently been revived by Olivier Rieppel and others. The idea has also gained some support from DNA cladistics which tends to place the turtles up above the Diapsid split, although their placement is sometimes (perhaps embarrassingly) closer to Archosaurs than to Lepidosaurs. However, given the total absence of (other) living Sauropterygians, a little uncertainty is only to be expected. 21
The Stone Culture Museum opened 1/1/2001 in Guizhou province (Xiaohe District of Guiyang City). Has more than 800 fossils including 100 sea lily fossils and 100 fossils keichousaurus and ichyosaurus (Himalayasaurus Tibetensis).
Phylogenetic Tree Sauropterygian
- from Finnish Museum of Natural History, Mikko Haaramo's, Sauropterygians: (ref: 13, 13, 15, 16, 17, 18)o †SAUROPTERYGIA Owen, 1860
|?- †THALATTOSAURIFORMES sensu Rieppel, 1997
`--+?- †PLACODONTIA Cope, 1871 sensu Rieppel, 2000
`--o †EOSAUROPTERYGIA Rieppel, 1994
`--o †EUSAUROPTERYGIA Tschanz,1989 sensu Rieppel,1997&Rieppel&Hagdorn, 1997
`--+?- †Sanchiaosaurus dengi
|--o NOTHOSAUROIDEA
| |--o †PACHYPLEUROSAUROIDEA Huene, 1956
| | `--o Pachypleurosauridae Nopcsa, 1928
| | |?- †Anarosaurus multidentatus
| | |?- †Lambrosauroides goepperti
| | |-- †Psilotrachelosaurus
| | |-- †Hanosaurus hupehensis
| | |--o †Keichousaurus
| | | |-- †K. hui
| | | |-- †K. yuananensis
| | | `-- †K. lusiensis, CORROY 1928 & GONZUI 1978)
| | `--+-- †Dactylosaurus
| | `--+-- †Serpianosaurus
| | `-- †Neusticosaurus pusillus
| `--o †NOTHOSAURIA
| |-- †Simosaurus gaillardoti [Simosauridae]
| `-- †Nothosauridae Baur, 1889
`--o †PISTOSAUROIDEA Zittel, 1887
|--+-- †Corosaurus alcovensis Case, 1936
| |-- †Chinchenia sungi
| `-- †Kwangsisaurus orientalis
`--o †PISTOSAURIA Zittel, 1887 sensu Rieppel, 1998
|-- †Augustasaurus hagdorni
|--o †Cymatosaurus [Cymatosauridae]
| |?- †C. stensioeii(Haas,1963)[Micronothosaurus stensioeii
| | Haas, 1963]
| |?- †C. erythreus
| `-- †C. multidentatus
`--+--o †Pistosaurus [Pistosauridae Zittel, 1887]
| |?- †P. grandaevus
| `-- †P. longaevus
`-- †PLESIOSAURIA [Plesiosauroidea] (joutsenliskot)References:
1. http://www.geoscience-enterprises.com/dinosaur.htm
2. http://www.geoscience-enterprises.com/Products/Saurus/ku9922.htm
3. http://www.stonecompany.com/fossils/vertebrate/reptiles/keichousaurus/information.html
4. http://www.fossil-gallery.ch/dino1.htm
5. http://www.kheper.auz.com/gaia/biosphere/vertebrates/sauropterygia/Pachypleurosauria.html
6. http://www.kheper.auz.com/gaia/Mesozoic/Triassic/Triassic.htm (time reference)
7. http://www.sin-am.com/dinosaurmuseum.htm
8. C.C. Young, 1958 - "On the new Pachypleurosauroidea from Keichow, South-west China",Vertebrata PalAsiatica, 2(2)
9. C.C. Young, 1965 - "On the new Nothosaurs from Hupeh and Kweichou, China", Vertebrata PalAsiatica, 9(4)
10. http://www.plesiosaur.com/taxonomy/pachypleurosauridae.htm - Plesiosaur Site - Pachypleurosauridae
11. http://www.zoomwhales.com/subjects/dinosaurs/glossary/indexk.shtml - ZoomDinosaurs
12. http://www.fireandiceinc.com/fossils.htm - Fire & Ice, Fossils
13. http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Reptilia/Sauropterygia/Sauropterygia.htm
Finnish Museum of Natural History, Mikko Haaramo's Phylogenetic Trees, Sauropterygians
14. http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Reptilia/Sauropterygia/Pachypleurosauroidea.htm Finnish Museum of Natural History, Mikko Haaramo's Phylogenetic Trees, Pachypleurosaurs
15. Carroll, R. L., 1988: Vertebrate paleontology and evolution. --W. H. Freeman and company, New York, 1988. 698.
16. Carroll, R. L., 1988: Appendix. 594-648. in Carrol, R. L. 1988: Vertebrate paleontology and evolution.
17. Rieppel, O., 1997: Part II: Sauropterygia - Introduction. 107-119 in Callaway, J. M. & Nicholls, E. L., (eds.) 1997
18. Rieppel, O. & Hagdorn, H., 1997: Paleobiogeography of Middle Triassic Sauropterygia in Central and Western Europe. 121-144
19. Dr A. H. Müller, Lehrbuch der Paläozoologie, vol.II - Vertebrates - part 2 , 1968 pp.151-2
20. http://home.houston.rr.com/vnotes/unit3.3.html - Pachypleurosauridae, The Vertebrate Notes
21. http://home.houston.rr.com/vnotes/notes/pachypleurosauroidea.html - Pachypleurosaur Notes, The Vertebrate Notes
22. O Rieppel, Journal of Vertebrate Paleontology, 1998, 18(3): 545-557 - Journal of Vertebrate Paleontology Society of Vertebrate Paleontology (SVP), "The systematic status of Hanosaurus hupehensis (Reptilia, Sauropterygia) from the Triassic of China" http://www.vertpaleo.org/jvp/18-545-557.html
23. Rieppel, Olivier 1987. The Pachypleurosauridae: An annotated bibliography. With comments on some lariosaurs.
24. Rieppel, O. & Lin, K., 1998. Functional morphology and ontogeny of Keichousaurus hui (Reptilia, Sauropterygia).