Haldanodon


Haldanodon is an extinct mammaliaform, specifically a docodont. It lived in the Upper Jurassic. Its fossil remains have been found in Portugal, in the well-known fossil locality of Guimarota, which is in the Alcobaça Formation. It was an insectivore and may have been semi-aquatic.

Description

Haldanodon was about the size of a desman in length, and may have had a similar ecology. The skull of Haldanodon is well known, and there is a little of the limbones also preserved. The body was compact and the legs were short and robust. The articulation of the distal humerus was particularly expanded, indicating strong muscles for either digging or swimming. The first front paws were relatively short, and the bones were curved and laterally compressed. The roughness of the skull on the nasal bones has been suggested to indicate the presence of a shield of keratin on the head above the eyes. The jaws were robust; in particular, the mandible was equipped with a highly developed coronoid process, which is seen in close relatives of this group.

Classification

This animal belonged to a group called the docodonts: early mammaliaforms with specialised teeth that lived in the Jurassic and Cretaceous. The docodonts were a widespread group in Laurasia, and show interesting ecological diversity. Haldanodon has been found as a sister group to Docodon in many analyses.
;Phylogeny

Lifestyle

Haldanodon may have been a semi-aquatic insectivore similar to the modern desmans. This is indicated by some skeletal features, such as the strong forelimbs and specialized ends. However it may also have been a good digger, and the skull and possible keratin cephalic shield are all adaptations that could indicate both digging and swimming.