Cricodon

Cricodon was first discovered in the Tanzanian Manda Beds of South Africa. were the first to describe Cricodon, yet were not able to provide a name for the taxon, which at the time was only known from 5 teeth. Extensive and in-depth descriptions of fossils from the Manda Beds were provided by A. W. Crompton (1955). The Cynognathus Assemblage Zone encompasses the boundary between the late Early and early Middle Triassic period, and has been subdivided into three distinct subzones (Subzone A, Subzone B, and Subzone C) based primarily on the spatial and temporal ranges of key temnospondyl index taxa. ==Description==

Skull of Cricdon metabolus with tool provided for size reference|alt=|left Cranial bones recovered from the Manda Beds consist of a badly crushed orbito-ethmoidal region, a practically complete right mandible, two fragments of the left mandible, several loose teeth, a portion of the occiput, and several unidentified fragments. The newfound discovery in regards to the thickened enamel has many ecological implications. In Cricodon metabolus, the enamel layer of the gomphodont tooth is around 11.5 times thicker than the sectorial tooth. The postcanine gomphodont teeth (labiolingually expanded teeth with large occlusal surfaces) were used for chewing, crushing, and grinding fibrous plant material, meaning that they were under higher loads and apically oriented stresses. Sectorial teeth on the other hand were used to shear plant material and were not subjected to the same types of occlusal stresses, therefore the enamel thickness was not maintained. Another reason proposed by Hendrickx, Abdala, and Choiniere (2016) to explain the thin enamel in sectorial teeth is due to replacement timing and patterns, as they will be sequentially replaced by gomphodont teeth. Another characteristic that was observed in the gomphodont teeth were enamel and dentine incremental lines. The enamel and dentine incremental lines, odontoblast tubules in dentine, and discontinuous columnar divergence units in enamel support the consistent presence of synapsid columnar enamel in Cynognathia. Postcranial skeleton bones of Cricodon metabolus Twenty-five vertebrae were discovered which belong to the dorsal and sacral regions with only one vertebra having a well preserved neural arch from the sacral region. There are additional apophyses below the posterior zygapophysis which articulate with concavities on the lateral surface of the neural arch, posterior and inferior to the anterior zygapophysis. Cricodon metabolus has the typical cynodont expanded ribs of which thirteen dorsal ribs were discovered. The entire humerus was 12.5 cm long and had typical cynodont characterizations such as the twisted bone and the plane of the distal end forming an angle of 40 degrees with that of the proximal. The discovered femur was 12.5 cm long with the capitulum directed at an angle of 45 to 50 degrees to the main axis of the slender shaft. Another characteristic of the femur noted is that it projects well forward from the main body of the shaft. Although little is known of the hand of cynodonts, it is believed that Cricodon metabolus has a phalangeal formula of 23443, with the second phalange reduced in digits three and four. == Classification ==

Below is a cladogram from Gao et al. (2010) showing the phylogenetic relationships of one part of the Cynodontia relative to Cricodon: }} ==See also==