Polacanthinae

The Polacanthidae or Polacanthinae are a controversial taxon within the group of dinosaurs Ankylosauria.

Ankylosauria traditionally are divided into two groups, and the Ankylosauridae Nodosauridae. The Ankylosauridae are characterized among other things by the broad skull and a bony club at the tail end, while the Nodosauridae have a narrow skull, no tail lobe and an eye-catching, bump-like protrusion of the scapula.

Some Ankylar that were grouped as Polacanthinae exhibited characteristics of both groups to some degree seated on a " nodosauriden " skeleton a " ankylosaurider " skull. Accordingly, the classification of Polacanthinae was controversial, they were led either one or the other traditional group as a subfamily. Complicating the systematic classification was the fact that many representatives only fragmentary fossils are preserved and the skull is often lacking.

Kenneth Carpenter stood by phylogenetic studies in 2001, the Polacanthidae to the rank of a separate family beside Ankylosing and Nodosauridae. Characteristic of this group were in addition to the features mentioned above, a relatively uniform construction of the - existing in all Ankylosauria - armor of bony plates ( osteoderms ) that were approximately triangular and thin. Often beyond bony spike were present and the teeth were relatively unspoilt. According to Carpenter, the Polacanthidae lived in the late Jurassic and the Cretaceous.

The following genera may have belonged to the Polacanthidae:

• Gargoyleosaurus
• Gastonia
• Hoplitosaurus
• Hylaeosaurus
• Mymoorapelta
• Polacanthus

However, other classifications do not recognize this taxon. The phylogenetic studies of M. Vickaryous et al. leads Gargoyleosaurus and Gastonia as basal representatives of Ankylosauridae and classifies the remaining four genera as " incertae sedis Ankylosauria ," meaning there are not enough data for an unambiguous classification available.

The main problem is probably constitutes the most only sparse fossils of many Ankylosauria can until further about the question of whether the Polacanthidae are a valid taxon, not be answered.