page_title: Kenomagnathus
section_title: Evolutionary history
hierarchical_section_title: Kenomagnathus / Classification / Evolutionary history
caption_attribution_description: English: ROM 43608, holotype of Kenomagnathus scottae, gen. et sp. nov., close-up of anterior maxilla in medial aspect, from latero-ventral (above) and lateral (below). Scale bars equal 2 cm.
context_page_description: Kenomagnathus is a genus of synapsid belonging to the Sphenacodontia, which lived during the Pennsylvanian subperiod of the Carboniferous in what is now Garnett, Kansas, United States. It contains one species, Kenomagnathus scottae, based on a specimen consisting of the maxilla and lacrimal bones of the skull, which was catalogued as ROM 43608 and originally classified as belonging to "Haptodus" garnettensis. Frederik Spindler named it as a new genus in 2020.
context_section_description: Modern mammals (except whales) commonly exhibit heterodont teeth, or teeth of several different types. Among the extinct relatives (stem group) of mammals, there is a gradient from animals with isodont (uniform) teeth to animals with heterodont teeth, associated with the development of distinct "zones" along the tooth row. Canine-like teeth — double canines like that of Kenomagnathus in particular — are common among basal synapsids and also other basal amniotes, along with the enlargement of the first premaxillary tooth at the front of the skull. There is a morphological gap between basal synapsids like "Haptodus" garnettensis, which have precanine teeth but less tooth variation over all, and therapsids (which are closer to mammals), which have no precanine teeth, only one set of canines, and more subtle tooth variation. Precanine teeth are often replaced by a large diastema in therapsids.
  Kenomagnathus had both precanine teeth and a diastema, which fills the gap between basal synapsids and therapsids to some extent. It reflects what would have been an ongoing transition, which other stem-mammals with diastemata would also have gone through. Spindler hypothesized that the diastema initially developed as a consequence of the maxilla and premaxilla being angled against each other by the precanine step, which would have prevented the precanine teeth from growing longer; this is seen as an "initial diastema" in "H." garnettensis, Ianthasaurus, and Ianthodon. This would have allowed the corresponding canines on the lower jaw to grow longer and fill the gap, which in turn would have led to a full diastema. However, Spindler also noted that the relationship between the development of the precanine step, tooth loss, and the diastema was unclear, and that the feeding styles of these animals may also have had an effect.
caption: Closeup showing the diastema of Kenomagnathus
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