Abstract
ABSTRACT: The muscles of the Amazonian manatee are described and compared with those of other manatees and the dugong. Maps of muscle attachments and data on weights of muscles are included. The manatee species differ in the forms of the mm. rectus capitis lateralis and biceps brachii. The mechanisms of protrusion of upper-lip bristles and opening of the nostrils are described. The jaw apparatus is uniquely specialized, with a very large temporalis muscle constituting more than half the adductor muscle mass, and development of a joint between the pterygoid process and the mandible which probably braces the mandible during transverse chewing. The center of mandibular rotation in transverse chewing probably lies posteromedial to the pterygoid process on the active side: the contralateral temporalis is dominant in transverse chewing. Trichechus inunguis is more specialized for surface-feeding and for swimming than T. manotus.
Highlights
Os músculos esqueléticos do peixe-boi da Amazônia (Trichechus inunguis) são descritos, ilustrados e comparados com prévias descrições dos sistemas musculares dos peixes-bois e do dugong
The specimens used in this study all had 6 cervical,15 thoracic, and 25 or 26 postthoracic vertebrae, and 15 pairs of ribs, ofwhich 3 attached to thte sternum, except in INPA-PB 6 where only two were attached. (In INPA-PB 8, the third costal cartilage ended about halfway to the sternum and was connected to it only by a ligament.) As there is no welldefined ligament connecting the ischium with, and thereby serving to identify, a sacral verte bra, I have avoided trying to distinguish between lumbar, sacral, and caudal vertebrae
INSERTION : Passes aft from above at tachments as single broad sheet of parallel fibers extending from ventral midline out to beyond tips of ribs; abaft flipper, lateral edge of muscle descends posteroventrad across flank
Summary
The myology of the Amazonian Manatee, Trichechus inunguis (Natterer) (Mammalia : Sirenia) Acta Amazônica, Manaus, 8(2) : Suplemento (1) j u n .
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