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The purpose of this study was to develop new standards for determining the sex of fragmentary human skeletal remains. We measured height, width, and length of the mastoid process in medieval to early modern Japanese skeletons, from the Yuigahama-minami and Hitotsubashi sites, in order to provide a metric standard for the diagnosis of sex using the mastoid process. We calculated discriminant functions based on these measurements; the accuracy of sex classification was over 80% using a single variable, and reached 82-92% with two variables, mastoid height and width. This accuracy is equal to or better than that reported by some previous studies of sex determination using the cranium. However, when we examined intra-and interobserver errors in the mastoid process measurements, we found a high level of errors, and this highlights the difficulty involved in intraobserver repeatability and interobserver reproducibility. Our results imply that, in order to achieve reliable results of sex determination using the mastoid process, the measurement methods need to be carefully determined and executed.

The great-gray kangaroo (Macropus giganteus) belongs to the Diprotodontia suborder (herbivorous marsupials of Australia) of the order of marsupials. We dissected the masticatory muscles in the great-gray kangaroo and classified them based on their innervation. Three (two male and one female) adult great-gray kangaroos (M. giganteus), fixed with 10% formalin, were examined. The masseter muscle of the great-gray kangaroo was classified into four layers (superficial layers 1, 2, 3, and a deep layer), all innervated by masseteric nerves. Layer 1 of the masseter muscle was well developed and the deep layer inserted into the masseteric canal. The zygomaticomandibular muscle, which belongs to both the masseter and temporalis muscles, was innervated by both the masseteric nerve and posterior deep temporal nerve, and the temporalis muscle was innervated by the anterior and posterior deep temporal nerves. The medial pterygoid muscle, which was innervated by the medial pterygoid nerve, was divided into superficial and deep portions. The lateral pterygoid muscle was divided into superior and inferior heads by the buccal nerve. We propose that the relationship of the masticatory muscles in the kangaroo has evolved by passive anterior invasion of the deep layer of the masseter by the medial pterygoid muscle via the masseteric canal, associated with the development of an anteroposterior mode of mastication. Anat Rec 290: 382-388, 2007. 2007 Wiley-Liss, Inc.

The tongue and lingual papillae of the Japanese Insectivora, the Shinto shrew (Sorex caecuiens saevus), the long-clawed shrew (S. unguiculatus), the dsinezumi shrew (Crocidura dsinezumi dsinezumi) and the Japanese water shrew (Chimarrogale himalyica platycephala), were observed by scanning electron microscope. The tongue of these animals had two vallate papillae. In two species of the Sorex a papilla in the vallate papilla was surrounded by two separated trenches, but in the other species it was surrounded by only a continuous trench and a clear vallum. The fungiform papillae in the Sorex were less developed than those of the other species. In the Sorex and Crocidura, there was no filiform papilla on the lingual apex. These genera, however, have papillary projections in the margin of the lingual apex. The results of this investigation suggest that the Sorex and Crocidura indicate an ancient form of the mammalian tongue. These characters, furthermore, were compared among seven species in six genera added three species observed by Kobayashi et al. (1983) to this study.

Background: The mammalian mandible develops around Meckel's cartilage and other secondary cartilages, including the dentary. There have already been many studies of the development of the rat mandible that have employed histological serial sections. However, no previous investigators have captured the three-dimensional features of the developmental process.Methods: In this study, the technique of double staining with alizarin red S and alcian blue was employed directly on whole body specimens to investigate the three-dimensional development of the rat mandible.Results The mandible is the largest and strongest bone of the face, and it is essential for the function of mastication. In mammals, the mandible consists mainly of a dentary bone, but Meckel's cartilage appears transiently during the early stages of development, a period of great interest to anatomists.Following the critical description of Meckel's cartilage (Meckel, 1820), some researchers claimed that it did not ossify or play any role in the development of the mandible (Brock, 1876). Low (1909) reported that Meckel's cartilage ossified partly but did not contribute to mandibular development or growth, whereas Bhaskar et al. (1953) and Frommer and Margolies (1971) stated that the cartilage ossified enchondrally and contributed to the growth of the mandible. The problem of the role of Meckel's cartilage now seems to have been solved for the rat and mouse because it appears to ossify and also plays a part in the development of the mandible.A few studies have been reported on the development of the dentary or second cartilages in the rat (Bhaskar, 1953;Youssef, 1969), but they were based on crosssectional examination of the tissues and the construction of models based on serial sections. These models were not exact or detailed. Because it takes considerable time and effort to make models, it is not possible to observe many specimens or stages. To date, no study has captured the three-dimensional features of the developmental process of the rat mandible.Thus, the aim of this paper was to describe the development of the dentary and second cartilages and of Meckel's cartilage in the rat mandible by using a technique of direct double-staining of whole body specimens. A second goal was to clarify the role of the cartilages in the developmental process. MATERIALS AND METHODSThis study was based on direct observation of doublestained whole body specimens from 2 male and 12 female Wistar rats. The rats were maintained at Kyushu Dental College under the care of the Animal Research Center. All animals were housed singly in a 12-hr light-dark cycle and were given laboratory chow and water. The male rats and the female rats, which were older than 8 weeks and were already sexually mature, were kept together for 12 hr overnight. The next morning, we observed vaginal smears. The day on which sperm was found in the vagina was considered to be day 0. The pregnant rats were anesthetized with ether and then killed by cervical dislocation. The embryos were removed by...

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Summary: An analysis of the laminations of the masseteric, zygomaticomandibular and temporalis muscles of the Red Kangaroo (Macropus Rufus) and all of the masticatory muscles of the Eastern Gray Kangaroo (Macropus Giganteus) was carried out based on their innervation. The masseteric muscle was divided into superficial and deep layers; the superficial layer was further subdivided into three laminae from the rostro-lateral portion to caudo-internal portion. The deep layer was divided into lateral, caudo-internal and rostro-internal laminae. The zygomaticomandibular muscle which was located between the masseteric and temporal muscles was divided into lateral, internal and rostral laminae, on the basis of its innervation. The lateral and internal laminae were innervated by the nerve which arises between the masseteric nerve and the posterior deep temporal nerve. A small rostral portion of the muscle was innervated by masseteric nerves, which passed through the internal lamina of the deep layer of the masseteric muscle. The temporalis muscle was innervated by an anterior deep temporal nerve and posterior deep temporal nerve. Only the most rostrointernal lamina of the temporalis muscle was innervated by the anterior deep temporal nerve. The anterior deep temporal nerve and lateral pterygoid nerve had a common trunk. We believe that the rostro-internal lamina was closely related to the lateral pterygoid muscle. The lateral pterygoid muscle displayed one lamina, whereas the medial pterygoid muscle was divided into internal and lateral laminae. The lateral lamina was further divided into rostro-internal and caudo-lateral laminae.

Published descriptions of the buccinator muscle of the cat (Felis domestica) differ from those for the same muscle in other mammals. Only an oral component of the muscle has been described in cats, not a buccal part. The purpose of this study was to identify the buccinator muscle in the cat and report on its anatomical features in detail. Dissections of the facial muscles were carried out on 12 specimens of adult cats (6 males and 6 females) that had been fixed with 10% formalin. We then observed the facial muscles and traced their innervations, arteries, and veins under a binocular microscope. The buccinator muscle in the cat was identified underneath an orbicularis oris, arising from the lower buccal membrane and from the molar region of the alveolar border of the mandible. It was about 3 mm wide at its origin, 4 mm wide at its insertion, and about 11 mm in length from origin to insertion. This contrasts with humans, in whom the muscle arises not only from the mandible, but also from the maxilla. Apart from this difference, this muscle in cats displays the following similarities to the buccinator muscle of other mammals: 1) it is innervated by the facial nerve; 2) it supports the buccal membrane; 3) it seems to insert into the modiolus; 4) its bundles run antero-posteriorly; 5) the posterior part of the muscle is located medially to the masseter muscle; 6) the parotid duct, facial nerve, artery, and vein run lateral to the muscle; 7) it is located deeper than other facial muscles; and 8) the buccal nerve runs on its surface. These relationships are spatially similar to those of the buccinator muscle in mammals. This muscle may aid in mastication, including suckling, and in expelling air forcibly, like the buccinator in humans. Anat Rec 267: 78-86, 2002.