Megazostrodon

Model of Megazostrodon at the Natural History Museum in London.

• Lesotho

Megazostrodon is one of the oldest representatives of mammals or mammal-like animals ( Mammaliaformes ). The animal lived in the Lower Jurassic, its fossils were found in the southern African country of Lesotho.

Description

Megazostrodon was an externally probably shrew -like animal, it reached a length of about 10 centimeters, its weight is estimated at 20 to 30 grams. In his Build it had some transitional features between the synapsids mammalian ancestors and the actual mammals. Thus, the construction of the temporomandibular joint shows the traces of the " reptilian " primary jaw joint between the articular Os and the Os quadratum. On the other hand, these animals already had the typical mammal four different types of teeth ( incisors, canines, premolars and molars ). Compared with the similarly built Morganucodon the sharp cusps of the molars were significantly larger and formed an obtuse triangle. There is also evidence of a one-time change of teeth, another typical feature of mammals. Because of this dentition, it is conceivable that Megazostrodon already nursed their young.

The brain is relatively larger than the older synapsider mammalian ancestors, probably the sense of smell and hearing of these animals were well developed. Eventually it led a nocturnal lifestyle, the diet is likely to have consisted of insects and other small animals.

System

Megazostrodon together with some closely related genera of the family Megazostrodontidae. While many nomenclatures this family fit into the group of Morganucodonta, others maintain a relationship to the Docodonta likely. Today largely discarded, however, is one belonging to the Triconodonta, a group of mammals that was characterized by dreihöckrige molars, but which has turned out to be not a natural group.

These animals had already advanced mammal- animal-like characteristics, but differed in details yet of today's mammals. Whether it is classified matter already in the mammals in the wider sense (sensu lato ) or in the mammal-like animals ( Mammaliaformes ), is controversial and largely definition question.