Hadrocodium

Hadrocodium
Temporal range: Sinemurian
~195 Ma
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Clade: Mammaliaformes
Genus: Hadrocodium
Luo, Crompton, & Sun, 2001
Species

Hadrocodium wui is an extinct mammaliaform that lived during the Sinemurian stage of the Early Jurassic approximately 195 million years ago in the Lufeng Formation in what is now the Yunnan province in south-western China (25°12′N 102°06′E / 25.2°N 102.1°E / 25.2; 102.1, paleocoordinates 34°18′N 104°54′E / 34.3°N 104.9°E / 34.3; 104.9). It is considered as the closest relative of the class Mammalia.

The fossil of this mouse-like, paper-clip sized animal was discovered in 1985 but was then interpreted as a juvenile morganucodontid. Hadrocodium remained undescribed until 2001; since then its large brain and advanced ear structure have greatly influenced the interpretation of the earliest stages of mammalian evolution, as these mammalian characters could previously be traced only to some 150 million years ago. Hadrocodium is known only from a skull 1.2 cm (0.47 in) long, and its body would have measured 3.2 cm (1.3 in) long in total and weighed up to 2 g (0.071 oz), making it one of the smallest Mesozoic mammaliaforms. The specimen is thought to have been that of a mature adult.

The name Hadrocodium alludes to its large cranial cavity, deriving from the Greek word hadrós (ἁδρός 'large, heavy, fullness') and the Latin word codium, from Greek kṓdeia (κώδεια 'head [of a plant]'). The species name, wui, is the Latinized version of discoverer Xiao-Chun Wu's name.

While initially suggested to have possessed a fully mammalian ear akin to those of modern mammals, a 2022 restudy suggested that it actually had a primitive mandibular middle ear similar to those of other primitive mammaliaforms.

Phylogeny

Cynodontia

Dvinia

Procynosuchidae

Epicynodontia

Thrinaxodon

Eucynodontia

Cynognathus

Tritylodontidae

Traversodontidae

Probainognathia

Tritheledontidae

Chiniquodontidae

Prozostrodon

Mammaliaformes

Morganucodontidae

Docodonta

Hadrocodium

Kuehneotheriidae

crown group Mammals

Phylogeny
Mammaliaformes 

 Adelobasileus

 Sinoconodon

 Morganucodon

 Megazostrodon

 Haramiyida

 Haldanodon

 Castorocauda

 Hadrocodium

 Mammalia

See also



This page was last updated at 2024-02-10 11:17 UTC. Update now. View original page.

All our content comes from Wikipedia and under the Creative Commons Attribution-ShareAlike License.


Top

If mathematical, chemical, physical and other formulas are not displayed correctly on this page, please useFirefox or Safari