From fish to modern humans - comparative anatomy, homologies and evolution of the head and

R. DIOGO; V. ABDALA; N. LONERGAN AND B. WOOD

JOURNAL OF ANATOMY

Blackwell Publishing

Año: 2008 vol. 213 p. 391 - 424

0021-8782

In a recent paper Diogo reported the results of the first part of a research project on the comparative anatomy, homologies and evolution of the head and neck muscles of osteichthyans (bony fish + tetrapods).That report mainly focused on actinopterygian fish, but also compared these fish with certain nonmammalian sarcopterygians. This paper, which reports the second part of the research project, focuses mainly on sarcopterygians, and particularly on how the head and neck muscles have evolved during the transitions from sarcopterygian fish and non-mammalian tetrapods to monotreme and therian mammals and namely to modern humans. The data obtained by our dissections of the head and neck muscles of representative members of groups as diverse as sarcopterygian fish, amphibians, reptiles, monotremes and therian mammals such as rodents, tree-shrews, colugos and primates, including modern humans, are compared with the information available in the literature. Our observations and comparisons indicate that the number of mandibular and true branchial muscles (sensu this work) present in modern humans is smallerthan that found in mammals such as tree-shrews, rats and monotremes, as well as in reptiles such as lizards.Regarding the pharyngeal musculature, there is a clear increase in the number of muscles at the time of the evolutionary transition leading to therian mammals, but no significant increase during the transition leading to the emergence of higher primates and modern humans. The number of hypobranchial muscles is also somewhat constant within the therian mammals we examined, although in this case modern humans do have more muscles than other mammals. The number of laryngeal and facial muscles present in modern humans is greater than that found in most other taxa. Interestingly, modern humans have various peculiar laryngeal and facial muscles that are not present in the vast majority of the other mammalian taxa; this seems to corroborate the crucial role played by vocal communication and by facial expressions in primate and namely in human evolution. It is hoped that by compiling, in one paper, data about the head and neck muscles of a wide range of sarcopterygians, the present work could be useful to comparative anatomists,evolutionary biologists and functional morphologists and to researchers working in other fields such as developmental biology, genetics and/or evolutionary developmental biology.