Rolling of the jaw is essential for mammalian chewing and tribosphenic molar function.

Over the past two centuries, mammalian chewing and related anatomical features have been among the most discussed of all vertebrate evolutionary innovations. Chief among these features are two characters: the dentary-only mandible, and the tribosphenic molar with its triangulated upper cusps and lower talonid basin. The flexible mandibular joint and the unfused symphysis of ancestral mammals-in combination with transformations of the adductor musculature and palate-are thought to have permitted greater mobility of each lower jaw, or hemimandible.

Muscle Logic: New Knowledge Resource for Anatomy Enables Comprehensive Searches of the Literature on the Feeding Muscles of Mammals.

Background: In recent years large bibliographic databases have made much of the published literature of biology available for searches. However, the capabilities of the search engines integrated into these databases for text-based bibliographic searches are limited. To enable searches that deliver the results expected by comparative anatomists, an underlying logical structure known as an ontology is required.

A preliminary analysis of correlations between chewing motor patterns and mandibular morphology across mammals.

The establishment of a publicly-accessible repository of physiological data on feeding in mammals, the Feeding Experiments End-user Database (FEED), along with improvements in reconstruction of mammalian phylogeny, significantly improves our ability to address long-standing questions about the evolution of mammalian feeding. In this study, we use comparative phylogenetic methods to examine correlations between jaw robusticity and both the relative recruitment and the relative time of peak activity for the superficial masseter, deep masseter, and temporalis muscles across 19 mammalian species from six orders. We find little evidence for a relationship between jaw robusticity and electromyographic (EMG) activity for either the superficial masseter or temporalis muscles across mammals.

Masticatory motor programs in Australian herbivorous mammals: diprotodontia.

Movement of the jaw during molar occlusion is determined by the sequence of activity in the adductor muscles and this sequence is one way to define a masticatory motor program. Based on the similarity of molar structure, it is probable that the American opossum and the early Tertiary mammals that gave rise to all Australian marsupials probably shared a common "primitive" masticatory motor program. The distinct and various patterns of movement of the jaw in the major groups of Australian marsupial herbivores (diprotodontids) are achieved by both subtle and substantial shifts in the timing of the primitive sequence.

Ontogenetic changes in Mammalian feeding: insights from electromyographic data.

All infant mammals make a transition from suckling milk to eating solid foods. Yet, the neuromuscular implications of the transition from a liquid-only diet to solid foods are unknown even though the transport and swallowing of liquids is different from that of solids. We used legacy electromyography (EMG) data to test hypotheses concerning the changes in motor pattern and neuromuscular control that occur during the transition from an all-liquid diet to consumption of solid food in a porcine model.

Masticatory motor pattern in the koala (Phascolarctos cinereus): a comparison of jaw movements in marsupial and placental herbivores.

Do closely related marsupial herbivores (Diprotodontia) conserve a common masticatory motor pattern or are motor patterns linked to the structure and function of the masticatory apparatus? We recorded the sequence and duration of activity of the individual jaw closing muscles during rhythmic chewing in koalas and then compared their motor pattern with that of their closest extant relatives, wombats, and their more distant marsupial relatives, macropodoids. These three lineages prove to have fundamentally different motor patterns and jaw movements during mastication. Each motor pattern represents independent modifications of an earlier motor pattern that was probably present in an ancestral diprotodontian.

Development of the movement of the epiglottis in infant and juvenile pigs.

Although backward folding of the epiglottis is one of the signal events of the mammalian adult swallow, the epiglottis does not fold during the infant swallow. How this functional change occurs is unknown, but we hypothesize that a change in swallow mechanism occurs with maturation, prior to weaning. Using videofluoroscopy, we found three characteristic patterns of swallowing movement at different ages in the pig: an infant swallow, a transitional swallow and a post-weaning (juvenile or adult) swallow.

Volume and rate of milk delivery as determinants of swallowing in an infant model animal (Sus scrofia).

The volume transported into the valleculae by the rhythmic tongue movements of suckling is considered the prime factor for initiating pharyngeal swallowing (the movement of milk out of the valleculae and through the pharynx to the esophagus). This study addressed the impact of variation in two factors on sucking (oral phase) and on swallowing (pharyngeal phase) in infant pigs, as a model for mammalian function: (1) the delivery of different-volume aliquots of milk and (2) the delivery of equal-sized aliquots at different frequencies. The number of sucks per second remained constant with change in both aliquot volume and change in the frequency of milk delivery.