Evolution of the mammalian fauces region and the origin of suckling

Citation:

Alfred W. Crompton, Catherine Musinsky, José F. Bonaparte, Bhart-Anjan Bhullar, and Tomasz Owerkowicz. Submitted. “Evolution of the mammalian fauces region and the origin of suckling.” Journal of Mammalian Evolution. Copy at http://www.tinyurl.com/y57e6qtz

Abstract:

Suckling in therian mammals requires synchronous activity in the tensor veli palatini, palatoglossus, mylohyoideus and intrinsic tongue muscles that close the fauces. These muscles draw the dorsal surface of the tongue against a tensed soft palate to form a seal between the oral cavity and oropharynx. Depressing the tongue in front of the seal induces negative pressure and draws milk into the oral cavity. To trace the origin of fauces region in mammals, we studied serial sections of a pouch young marsupial and CT scans of non-mammalian cynodonts, ictidosaurs, mammaliaforms, and extant mammals.In Late Triassic ictidosaurs (Brasilitherium) and mammaliaforms, the origin of a medial slip of the reptilian posterior pterygoideus migrated to the lateral surface of the pterygopalatine boss that supported the lateral edge of a non-muscular soft palate. Suckling arose in early mammals after fibers of this slip migrated into the soft palate to form the tensor veli palatini, and the palatoglossus separated from the pharyngeal constrictors. The added stress on the pterygopalatine boss led to the addition of a hamulus. Once the transverse process of the pterygoid was lost, the lateral posterior pterygoideus differentiated to form the medial pterygoid. Monotreme ancestors modified the fauces region to break down invertebrates between keratinized pads on the posterior tongue and under the ventral surface of a long palatine. They lost the tensor veli palatini and palatoglossus and lack the ability to suckle.

Notes:

See Science Magazine's take on our research: http://science.sciencemag.org/content/361/6399/213
Last updated on 10/04/2018