Hylonomus

Life image of Hylonomus lyelli

• North America (Canada )

Hylonomus lyelli (German wood mouse ) is an extinct Reptilart. She lived in the Upper Carboniferous to around 315 million years in the Canadian province of Nova Scotia and is one of the first amniotes, the first "real" land vertebrates, dar. Hylonomus was discovered by Sir John William Dawson in 1851. The Style epithet lyelli chose Dawson after his teacher, Sir Charles Lyell, who accompanied him on his expedition.

Locality

So far, the only locality of Hylonomus is Coal Mine Point in the world famous cliffs of Joggins in Canada. The cliff consists of 315 million years old sand -, silt - and mudstones, including low- mighty coal seams of the Westphalian A ( Bashkirian ). Many Hylonomus specimens are very well preserved. So can demonstrate intact scales and smallest intact bone some fossils. Hylonomus fossils were mostly found in fossilized tree stumps, which are allocated to the club moss - green Sigillaria.

This circumstance could be as follows have come about: When floods the trees died, leaving behind hollow tree stumps, in which accumulated organic material such as plant remains. This in turn attracted insects, which Hylonomus followed. The 20 cm long animal plunged into it and did not come out why it died of hunger. There was then buried by mud, which turned into millions of years and under high pressure into shale.

In such Joggins fossil tree stumps were exposed over thirty.

Properties

Hylonomus was one of the first creatures that were fully adapted to life on land, and laid their first eggs with a protective, hard shell and an amniotic membrane ( amnion ). This form of eggs enabled them farther away from water than any other animal of their time. As the oldest, previously found fossil amniotes Hylonomus is thus a milestone in the evolution.

Hylonomus was about 20 cm long, lived in a tropical climate and fed probably by insects ( Insektivor ), which he crushed with its conical teeth. Some of the teeth in the front row were longer than the behind, which is a feature for higher reptiles. Much of his skeleton was very similar to an amphibian (eg, the head, shoulders, pelvis, and the "transitional teeth " and vertebrae ). The rest of the skeleton was that of a reptile: Strong muscles of mastication, no palatal fangs and no eardrum.

Classification

With features such as the teeth or the windowless ( Anapside ) skull shape could be shown that this lizard a reptile was already more than an amphibian. In 2006 it was therefore decided that Hylonomus, is the oldest reptile light of present knowledge. Westlothiana from Scotland is older, but rather a core group representatives of the amniotes, which is not yet part of it. Hylonomus is therefore the first type of amniotes, including dinosaurs, birds and mammals belong.