Temporal range: Lower Triassic ~248 mya
|Specimen AGM CHS-5|
It was closer in time and form to Cymbospondylus and Mixosaurus than to more advanced genera like Ichthyosaurus. It did not have the dolphin-like form of later ichthyosaurs, but it was fully aquatic. The tail fin is wide-based and short. The neck is rather long, whereas later ichthyosaurs have no neck. There is no dorsal fin.
It was one of the smallest ichthyosaurs, about 70 to 180 cm long. Its weight was about 10 kg.
Reproduction[change | change source]
A recent study of Chaohusaurus shows an early example of live birth. A remarkable feature was a baby close to emerging head-first. The authors comment:
- "Its headfirst birth posture... strongly indicates a terrestrial origin of viviparity, in contrast to the traditional view. The tail-first birth posture in derived ichthyopterygians, convergent with the conditions in whales and sea cows, therefore is a secondary feature". They comment "obligate marine amniotes appear to have evolved almost exclusively from viviparous land ancestors".
References[change | change source]
- Some authorities call these early types ichthyosaurs, and some call them ichthyopterygians.
- Xiaohong Chen P. et al (2013). "A new Triassic primitive ichthyosaur from Yuanan, South China". Acta Geologica Sinica (English Edition) 87 (3): 672–677. http://www.geojournals.cn/dzxben/ch/reader/view_abstract.aspx?file_no=201303004&flag=1.
- Motani, Ryosuke et al 2014 Terrestrial origin of viviparity in Mesozoic marine reptiles indicated by early Triassic embryonic fossils. PLoS One