Articulatory Positions Research Articles

The impact of Playdough games on the development of oral motor skills in preschool children with childhood apraxia of speech

The relevant challenges are the use of innovative approaches that conserve both the speech therapist’s and the child’s resources while addressing multiple goals in speech therapy. The authors of this article have adopted such an approach to develop oral motor skills, which are crucial for speech development in preschoolers, particularly those with childhood apraxia of speech. This study aimed to evaluate the effectiveness of an author-developed therapy using Playdough games for preschool children with childhood apraxia of speech. A controlled design with repeated measures was employed. The primary diagnosis of CAS was established based on clinical assessment. A comparative evaluation of two groups (control and experimental) was conducted using a developed methodology for assessing the level of manual and oral motor skills in preschool children before and after the author-developed therapy using Playdough games. Researchers discovered that the systematic use of their author-developed Playdough games positively impacted the motor skills of children with CAS. Children in the experimental group, who participated in Playdough therapy, demonstrated significant improvements in both manual and oral motor skills, increased precision and focus in movement execution, and enhanced accuracy and speed of articulatory movements. There was a reduction in delays and incorrect movement sequences during finger movement tasks. Children required less additional time and significantly less assistance from the speech therapist, indicating a positive impact of using Playdough in therapy. The following skills improved: transitions between articulatory positions, which helped children avoid coarticulation difficulties; planning of movement sequences; and smooth transitions between sounds and syllables. The practical significance of this study lies in the effectiveness of using Playdough games for significantly improving oral motor skills, movement precision, and concentration in children with childhood apraxia of speech, thereby reducing the need for additional speech therapy support

Comparison the Voice Onset Time (VOT) of Postlingual Cochlear Implant Users and Normal Peers in the CAPE_V Sentences as Continues Speech Task

BackgroundAuditory perception plays a crucial role in speech and language development, emphasizing concerns about hearing loss. While cochlear implantation nearly tackles challenges associated with post-lingual hearing loss in adults, the importance of "auditory feedback" and acoustic assessment becomes crucial for evaluating speech disorders and devising effective treatments. This study aims to address the gap in assessing Voice Onset Time (VOT) as an indicator of nuanced variations in the speech of cochlear implant users during a continuous speech task. MethodRecordings of Persian CAPE-V sentences were obtained from 25 cochlear implant (CI) users and 25 healthy speakers, with a mean age of 33.2 years (SD=11.5, range=18-55 years). Ten words, incorporating both voiced and voiceless consonants, were selected from the CAPE-V sentences. VOT measurements for the specified stop consonants at the initial syllables of these chosen words were computed using PRAAT. A comparative analysis between the two age- and gender-matched groups was conducted using an independent sample t-test. Subsequently, ANCOVA was employed to examine the influence of demographic factors on VOT values among CI participants. ResultsUnvoiced consonant /p/ in /po/, /pɑ/, /pe/, and /pa/ syllables had higher VOT values in the healthy group, while the voiced consonant /d/ in /da/ and /di/ syllables demonstrated higher VOT values in the CI group. (P<0.05) Apart from /po/ and /di/ syllables, no significant impacts of demographic factors on VOT values were observed (P≥0.8). ConclusionDespite the improvement in speech quality after cochlear implantation, subtle differences persist. The motor theory, which underscores the impact of auditory inputs on temporal coordination, highlights the role of VOT in speech discrimination. Various linguistic factors affect VOT, including articulation position, vowel context, and raised vowels. While CI enhances syllable distinction, challenges in articulation for adults suggest a need for targeted training in rehabilitation programs, ultimately enhancing the quality of life for CI users.

Initial Stop Acquisition in Typically Developing Children Aged 1- to 2-Year-Olds

Objectives: This study investigated the articulatory characteristics of initial stops in the speech of 1-2-year-old children.Methods: A total of 35 typically developing children aged 1-2 years participated in the study. The participants performed a naming task using nine monosyllabic words containing initial stops. The accuracy of consonants in the initial stops, as well as errors in articulation position and voicing features were analyzed among children in the late 1-year-old and early 2-year-old age groups. Consonant accuracy, articulation position and voicing error ratios were compared between the two age groups. Additionally, the study investigated patterns of voicing errors observed in each age group in detail.Results: Findings revealed that the articulatory characteristics of initial stops were prominent in voicing errors observed in both age groups. Consonant accuracy was significantly higher in the early 2-year-old group compared to the late 1-year-old group. The most prevalent error observed in both late 1-year-old and early 2-year-old children was voicing errors. Examining the patterns of voicing errors, it was found that late 1-year-olds exhibited all possible error patterns in voicing features, while early 2-year-olds showed a reduction or disappearance of some voicing error patterns, excluding errors related to aspiration.Conclusion: This study investigated the articulatory characteristics of initial stops in the speech production of children in the late age of 1 and the early age of 2, presenting information on the acquisition process of initial stops. Error patterns in voicing features were commonly observed in the younger age group before the late age of 2.

세종대왕 관점에서 바라본 『훈민정음해례본』 재해석

Hunminjeongeum[Korean alphabet published by King Sejong in September 1446, meaning : the proper sound for the instruction of the people] is a very creative character in human history, but there is a lot of controversy over the creation principle of Hunminjeongeum because the Neo-Confucian interpretation of 『Hunminjeongeum Haeryebon』[An explanatory booklet on how Korean alphabet was created based on what principles] is not clear in sound. It is even known that the creator of Hunminjeongeum was not King Sejong, and Hunminjeongeum is regarded as a character that imitates Sanskrit or Phags-pa character.&#x0D; Therefore, by reinterpreting 『Hunminjeongeum Haeryebon』 from the perspective of King Sejong, it is revealed that Hunminjeongeum is an original character created through music.&#x0D; In that way, it is necessary not only to prove the arrangement of ‘basic consonants’ and ‘Gung-Sang-Gak-Chi-Woo[Traditional 5-Note Scale which had been used in Joseon dynasty]’ that refer to music in 『Hunminjeongeum Haeryebon』 but also to present the ‘the proper sound’ of all consonants and vowels of Hunminjeongeum.&#x0D; As a result, Hunminjeongeum has a different phonetic system from other letters. currently, the articulation position of consonants is only determined by the shape of the mouth and the position of the tongue, and the articulation method of consonants is divided into 'voice echo' and 'sound intensity'. And vowels are classified into 'lip shape', 'tongue position', and 'the degree to which the mouth opens'. On the other hand, the consonant articulation position of Hunminjeongeum is determined by the positions of the lips and tongue are fit the scale of 'Gung-Sang-Gak-Chi-Wu', and the articulation method is classified in consideration of the volume of the mouth. Vowels are classified only as the location where the sound is ringing.&#x0D; In addition, the creation principle of Hunminjeongeum, which is difficult to understand, including the ternary method[Cho-Jung-Jong Seong] and the special upper or side point over the character, can be briefly explained by Geomungo, a string instrument. From this point of view, Hunminjeongeum, which contains musical elements, is a unique ‘music character’ that can express all sounds in the world. Therefore, the reinterpretation of Hunminjeongeum Haeryebon from the perspective of King Sejong is the basis for being listed on UNESCO as a cultural heritage for people around the world. [Only the Humminjeongeum Haeryebon is registered as a UNESCO Memory of the World, and Hunminjeongeum has not yet been registered.]

Quick speech motor correction in the absence of auditory feedback.

A quick correction mechanism of the tongue has been formerly experimentally observed in speech posture stabilization in response to a sudden tongue stretch perturbation. Given its relatively short latency (< 150 ms), the response could be driven by somatosensory feedback alone. The current study assessed this hypothesis by examining whether this response is induced in the absence of auditory feedback. We compared the response under two auditory conditions: with normal versus masked auditory feedback. Eleven participants were tested. They were asked to whisper the vowel /e/ for a few seconds. The tongue was stretched horizontally with step patterns of force (1 N during 1 s) using a robotic device. The articulatory positions were recorded using electromagnetic articulography simultaneously with the produced sound. The tongue perturbation was randomly and unpredictably applied in one-fifth of trials. The two auditory conditions were tested in random order. A quick compensatory response was induced in a similar way to the previous study. We found that the amplitudes of the compensatory responses were not significantly different between the two auditory conditions, either for the tongue displacement or for the produced sounds. These results suggest that the observed quick correction mechanism is primarily based on somatosensory feedback. This correction mechanism could be learned in such a way as to maintain the auditory goal on the sole basis of somatosensory feedback.

Skeletal taphonomy of the water frogs (Amphibia: Anura) from the Pit 7/8 of the Pliocene Camp dels Ninots site (Caldes de Malavella, NE Spain)

ABSTRACT The Pliocene lacustrine infill of Camp dels Ninots maar (Girona, Spain) hosts an exceptional record of complete articulated skeletons. Here we present the taphonomical description of 22 fossil water frogs recovered from the Pit 7/8 of Can Argilera Sector. Description of their skeletal taphonomy is done on the basis of their distribution, completeness, articulation and limb position, and by establishing comparisons with the late Miocene site of Libros (Spain). Microscopic examination shows no evidence of digestion and absence of weathering. Mass mortality or any environmental stress-induced factors cannot be ruled out, but natural death seems to be the most probable. Limited time of decay prior burial seems to be the main pattern explaining the relatively high degree of articulation and completeness. Floatation is not to be disregard for some more (proximally) disarticulated specimens. Taphonomical patterns document two types of sub-environments inside a cool and deep lake, suggesting a more complex depositional scenario for Camp dels Ninots than the ones described in others similar Konservat-Lagerstätten.

Automatic Multiple Articulator Segmentation in Dynamic Speech MRI Using a Protocol Adaptive Stacked Transfer Learning U-NET Model.

Dynamic magnetic resonance imaging has emerged as a powerful modality for investigating upper-airway function during speech production. Analyzing the changes in the vocal tract airspace, including the position of soft-tissue articulators (e.g., the tongue and velum), enhances our understanding of speech production. The advent of various fast speech MRI protocols based on sparse sampling and constrained reconstruction has led to the creation of dynamic speech MRI datasets on the order of 80-100 image frames/second. In this paper, we propose a stacked transfer learning U-NET model to segment the deforming vocal tract in 2D mid-sagittal slices of dynamic speech MRI. Our approach leverages (a) low- and mid-level features and (b) high-level features. The low- and mid-level features are derived from models pre-trained on labeled open-source brain tumor MR and lung CT datasets, and an in-house airway labeled dataset. The high-level features are derived from labeled protocol-specific MR images. The applicability of our approach to segmenting dynamic datasets is demonstrated in data acquired from three fast speech MRI protocols: Protocol 1: 3 T-based radial acquisition scheme coupled with a non-linear temporal regularizer, where speakers were producing French speech tokens; Protocol 2: 1.5 T-based uniform density spiral acquisition scheme coupled with a temporal finite difference (FD) sparsity regularization, where speakers were producing fluent speech tokens in English, and Protocol 3: 3 T-based variable density spiral acquisition scheme coupled with manifold regularization, where speakers were producing various speech tokens from the International Phonetic Alphabetic (IPA). Segments from our approach were compared to those from an expert human user (a vocologist), and the conventional U-NET model without transfer learning. Segmentations from a second expert human user (a radiologist) were used as ground truth. Evaluations were performed using the quantitative DICE similarity metric, the Hausdorff distance metric, and segmentation count metric. This approach was successfully adapted to different speech MRI protocols with only a handful of protocol-specific images (e.g., of the order of 20 images), and provided accurate segmentations similar to those of an expert human.

Rapid movements at segment boundaries.

This paper reports on a one-to-one aspect of the articulatory-acoustic relationship, explaining how acoustic segment boundaries are a result of the rapid movements of the active articulators. In the acceleration profile, these are identified as acceleration peaks, which can be measured. To test the relationship, consonant and vowel segment durations are compared to articulatory posture intervals based on acceleration peaks, and time lags are measured on the alignment of the segment boundaries to the acceleration peaks. Strong relationships and short time lags are expected when the acceleration peaks belong to crucial articulators, whereas weak relationships are expected when the acceleration peaks belong to non-crucial articulators. The results show that lip posture intervals are indeed strongly correlated with [m], and tongue tip postures are strongly correlated with [n]. This is confirmed by the time lag results, which also reveal that the acoustic boundaries precede the acceleration peaks. Exceptions to the predictions are attributed to the speech material or the joint jaw-lip control unit. Moreover, the vowel segments are strongly correlated with the consonantal articulators while less correlated with the tongue body, suggesting that acceleration of crucial consonantal articulators determines not only consonant segment duration but also vowel segment duration.

Speech biomarkers in Huntington's disease: A cross-sectional study in pre-symptomatic, prodromal and early manifest stages.

Motor speech alterations are a prominent feature of clinically manifest Huntington's disease (HD). Objective acoustic analysis of speech can quantify speech alterations. It is currently unknown, however, at what stage of HD speech alterations can be reliably detected. We aimed to explore the patterns and extent of speech alterations using objective acoustic analysis in HD and to assess correlations with both rater-assessed phenotypical features and biological determinants of HD. Speech samples were acquired from 44 premanifest (29 pre-symptomatic and 15 prodromal) and 25 manifest HD gene expansion carriers, and 25 matched healthy controls. A quantitative automated acoustic analysis of 10 speech dimensions was performed. Automated speech analysis allowed us to differentiate between participants with HD and controls, with areas under the curve of 0.74 for pre-symptomatic, 0.92 for prodromal, and 0.97 for manifest stages. In addition to irregular alternating motion rates and prolonged pauses seen only in manifest HD, both prodromal and manifest HD displayed slowed articulation rate, slowed alternating motion rates, increased loudness variability, and unstable steady-state position of articulators. In participants with premanifest HD, speech alteration severity was associated with cognitive slowing (r=-0.52, p < 0.001) and the extent of bradykinesia (r=0.43, p=0.004). Speech alterations correlated with a measure of exposure to mutant gene products (CAG-age-product score; r=0.60, p < 0.001). Speech abnormalities in HD are associated with other motor and cognitive deficits and are measurable already in premanifest stages of HD. Therefore, automated speech analysis might represent a quantitative HD biomarker with potential for assessing disease progression.

The orbitotemporal region and the mandibular joint in the skull of shrews (Soricidae, Mammalia)

Modern phylogenetics place the Soricidae (shrews) into the order Lipotyphla, which belongs to the relatively new superorder clade Laurasiatheria. Their most derived skull feature is the unusual position and shape of the jaw articulation: Whereas in all other mammals the glenoid region of the squamosum is more or less tightly attached to the otic capsule or petrosal, respectively, in the soricids it is attached to the nasal capsule. This new position of the jaw articulation becomes possible by the posterior extension of the nasal capsule and the rostral shift of the glenoid fossa. By the study of dated postnatal ontogenetic stages of Crocidura russula and Sorex araneus, we show that the glenoid part of the squamosal becomes fixed to the nasal capsule by the ossified alae orbitalis and temporalis. The ala orbitalis is displaced laterally by the expanded cupula nasi posterior; this posterior expansion is well documented by the lamina terminalis, which incorporates parts of the palatinum and alisphenoid. Both alae consist largely of ‘Zuwachsknochen’ (‘appositional bone’) and are then named orbitosphenoid and alisphenoid. By the forward move of the pars glenoidea and of the alisphenoid, the foramen lacerum medium (‘fenestra piriformis’) also expands rostrally. Functionally, the forward shift of the jaw joint helps to keep the incisal biting force high. Biomechanically the jaws can be considered as a tweezer, and the rostral position of the jaw joints makes the interorbital pillar and the shell-like walls of the facial skull a lever for the highly specialized incisal dentition.

Spatio-temporal Characteristics of Successive Plosive Consonants in the Same Place of Articulation: An Electropalatographic Study

Objectives: This paper used electropalatography (EPG) to investigate the actual pronunciation when two plosives with the same articulation position appear successively. We aimed to determine the presence of the preceding consonant (C₁) in two successive consonants (VC₁C₂V) with the same articulation place.Methods: Tongue-to-palate contacts were recorded during the pronunciation of 8 words and 4 sentences containing those words by 5 normal adults and the closure duration and the maximum contact frame for utterance units (word, sentence), meanings (real word, nonword), and syllable structures (VC₁C₂V, VCV) were analyzed.Results: The closure duration in the syllable structures and the maximum contact frame in the meanings showed significant differences. The closure duration of the VC₁C₂V structure was significantly longer than that of the VCV structure in case of words; however, the difference reduced in the case of sentences. The maximum contact frame of the real words was significantly higher than that of non-words.Conclusion: Since the temporal characteristics between VCV and VC₁C₂V structure was distinguished and the tensification of C₂ indirectly showed the existence of C₁. These result support the fact that the preceding consonant is not deleted in two successive consonants with the same articulation place.

Risk Factors for the Development of Persistent Stuttering: What Every Pediatrician Should Know.

Early identification and adequate treatment of children who stutter is important, since it has an impact on speech development. Considering the importance of aiding pediatricians to recognize children at risk for developing persistent stuttering, the aim of the present study was to correlate speech fluency characteristics of children, whose parents reported stuttering behaviors, to the risk factors of persistent stuttering. The participants were 419 children aged 2:0 to 11:11 years, who were divided into two groups: children with stuttering complaints (CSC), composed of children whose parents reported the presence of stuttering behaviors; and children with no stuttering complaint (CNSCs), composed of children with no stuttering behaviors. Risk variables were gathered based on a questionnaire answered by parents involving the following variables: sex, presence of family history of stuttering, whether stuttering behaviors were observed for more than 12 months, whether stuttering behaviors began before 5 years of age, increased effort to speak (i.e., syllable and sound repetitions and fixed articulatory positions), negative family attitude towards the child’s speech, and negative attitude towards the child’s own speech. The diagnosis of stuttering was determined by a formal speech assessment by a pathologist (SLP). The risk analysis indicated that increased effort to speak, negative family attitude towards the child’s speech, and complaints of stuttering for more than 12 months were associated with a higher risk of stuttering in children. Therefore, when pediatricians are faced with complaints about the presence of stuttering behaviors and these factors are present, they should immediately refer the patient to an SLP for specific assessment.

Understanding anticipatory speech postures: does coarticulation extend outside the acoustic utterance?

Multiple studies strongly suggest that anticipatory coarticulation has a planned component. Speakers forced to begin an acoustic utterance before knowing all details of how it will unfold show reduced coarticulatory influences from those initially unknown speech segments. Therefore, anticipatory coarticulation as we currently understand it may reflect a more general process whereby speech acts that are currently planned, but whose acoustic consequences remain in the future, bias current articulator positions. This more general process could be in effect even before an utterance is acoustically active. The present talk will review the author’s recent work in anticipatory speech postures. Specifically, these findings suggest that speakers bias their lips to anticipate utterances yet to be acoustically initiated, in a way that tracks currently available information. In laboratory tasks, speakers primed with just the initial consonant or nuclear vowel of an upcoming monosyllabic utterance shape their lips to reflect this priming. Similarly, speakers in natural conversation produce anticipatory lip postures while awaiting their turn, but only when the intended utterance is quite short. The conceptual links between these findings and anticipatory coarticulation will be discussed.

Articulatory postures and forward models in American Sign Language: Linguistic and neuroscience evidence

Articulatory postures and forward models in American Sign Language: Linguistic and neuroscience evidence

The production of ejectives in German and Georgian

This paper aims to shed light on the textbook description of ejective production through an analysis of the articulatory measures intraoral pressure and larynx height in a data set of phonological Georgian ejectives and epiphenomenal German ejectives. By comparing articulatory mechanisms for ejective production in these two languages, we aim to learn about how ejectives gain phonological status in a language. 14 female German speakers and 13 female Georgian speakers are recorded in a multi-channel experimental set-up. We collect intraoral pressure (IOP) data, an electroglottographic signal and larynx trace using a dual-channel electroglottograph, as well as audio data. We control for place of articulation, vocalic context, word and sentence position, as well as for plosive duration in our analysis. Generalized additive mixed-models are used for statistical analysis. In Georgian, larynx height highly depends on the word and sentence position of the ejective. We find evidence for the hypothesis that pressure buildup after oral closure may be realized by a pulmonic airstream in both Georgian and German ejective production. Sentence-internal Georgian ejectives are produced with lower IOP peak and less steep IOP increase than sentence-initial ejectives. Epiphenomenal ejectives in German are not produced with raised larynx and show lower average IOP than plosives in control conditions.

Tongue position variability in sustained vowels produced by healthy children and young adults with and without a semi-occluded vocal tract: A pilot study

Speech development is a process by which talkers learn, among other things, to coordinate neuromuscular activations of motor units spread across several muscles that effect articulator positioning and movement. This paper presents results from an analysis of tongue position variability during sustained vowel production. Data from two children (7 years 11 months, and 9years 7 months) and two young adults (both 20 years 7 months) are presented. Articulatory data were recorded with a 3D/4D ultrasound system, in two conditions: without a semi-occluded vocal tract (“without straw”) and with a semi-occluded vocal tract (“with straw”). Statistical analyses of tongue position variability revealed a main effect of age, with children showing greater variability than adults. There was no statistically significant main effect of condition, but the main effect of age was driven primarily by the “with straw” condition. We speculate that tongue position variability during sustained vowels may be an index of speech motor control maturity, and that the interaction between age and condition suggests children are less able than adults to rely on learned feed-forward motor programs under conditions of somatosensory perturbation, such as the presence of a straw between the lips.

Significant sensors and parameters in assessment of dysarthric speech

PurposeDysarthria is a neuromotor speech disorder caused by neuromuscular disturbances that affect one or more articulators resulting in unintelligible speech. Though inter-phoneme articulatory variations are well captured by formant frequency-based acoustic features, these variations are expected to be much higher for dysarthric speakers than normal. These substantial variations can be well captured by placing sensors in appropriate articulatory position. This study focuses to determine a set of articulatory sensors and parameters in order to assess articulatory dysfunctions in dysarthric speech.Design/methodology/approachThe current work aims to determine significant sensors and parameters associated using motion path and correlation analyzes on the TORGO database of dysarthric speech. Among eight informative sensor channels and six parameters per channel in positional data, the sensors such as tongue middle, back and tip, lower and upper lips and parameters (y, z, φ) are found to contribute significantly toward capturing the articulatory information. Acoustic and positional data analyzes are performed to validate these identified significant sensors. Furthermore, a convolutional neural network-based classifier is developed for both phone-and word-level classification of dysarthric speech using acoustic and positional data.FindingsThe average phone error rate is observed to be lower, up to 15.54% for positional data when compared with acoustic-only data. Further, word-level classification using a combination of both acoustic and positional information is performed to study that the positional data acquired using significant sensors will boost the performance of classification even for severe dysarthric speakers.Originality/valueThe proposed work shows that the significant sensors and parameters can be used to assess dysfunctions in dysarthric speech effectively. The articulatory sensor data helps in better assessment than the acoustic data even for severe dysarthric speakers.

The Verb and Proverb in Chinua Achebe’s Things Fall Apart

The present essay surveys the present position of African articulation with respect to its effects on the formulation of the linguistic identity. For this purpose, one puts gloss on Chinua Achebe’s Things Fall Apart that includes an ambiguous devotion to myriad technical and narrative devices to debunk the yoke of the British Empire. The essay argues that, in contrast to classical writers in the field of fiction, the Anglophone novelists have been much more resistant to the colonial doctrines of selective classification. In fact, the African authors do not only fade the conventional rules but they increasingly endorse the public desired narration wherein literariness includes free generic mixed tools. The postcolonial text becomes subversive and creative. The essay exposes a critical discussion of the previous premises of articulation and its bearing upon asserting an independent textual selfhood devoid of the colonial limitations. The gist seems to leave the ground for building a creative local voice with public desired qualities. Thus, the fact of blending the local with the public leaves room for blending the word and the world, the inside and the outside, the Joy and the loss. This paper comprises a conspicuous consideration of Achebe’s notion of African communication through pristine artistic text. Keywords: history, identity, classicism, postcolonial, articulation, artistic, loss

Tibetan Phonology

The germ of Tibetan phonology appeares first in the Sum cu pa composed by Thon mi sambhoṭa (7th century). At the end of the Sum cu pa, Thon mi states that the pronunciation of each syllable (/ka/, /ki/, /ku/, /ke/ etc.) should be learned in accordance with the method of pronouncing phonemes (nga ro, *svara) in the correct position of articulation. However, since Thon mi did not give a detailed explanation of Tibetan phonology in his Sum cu pa, Tibetan grammarians in later periods had to develop a theory of pronunciation of their language with the help of their knowledge of Sanskrit phonology. Among them, Si tu paṇ chen (1699/1700–1774) gives an explanation of Tibetan phonology in his Si tu’i ’grel chen on the basis of the Sanskrit phonology described in Candragomin’s Varṇasūtra. What emerges from Si tu’s explanation is the development of phonological theory that is characteristic to Tibetan but not found in Sanskrit. In addition, he reveals both the applicability of Sanskrit phonology to Tibetan and the limitations of its application. The purpose of this paper is to clarify the major characteristics of Tibetan phonology by examining Si tu’s explanation based on the Varṇasūtra and comparing it with the explanations given by other Tibetan grammarians.

Suboccipital muscle of sharpnose sevengill shark Heptranchias perlo and its possible role in prey dissection.

Skull and head muscles of Heptranchias perlo were studied. Its distinctive features include the suboccipital muscles, described for the first time, the absence of the palatoquadrate symphysis, a longitudinally extended mouth, and teeth unsuited for dissecting prey in typical method of modern sharks, which is cutting motions powered by head shaking from side to side. The palatoquadrate cartilages of H. perlo and closely related Hexanchidae articulate with the neurocranium via orbital and postorbital articulations, which together allow for lateral expansion of the jaws, but restrict retraction and protraction. We interpret these features as an adaptation to a different method of prey dissection, that is, ripping in a backward pull. It employs the specific postorbital articulation together with the suboccipital muscles as force-transmitting devices, and is powered by swimming muscles which produce a rearward thrust of the tail. During this type of dissection, the anterior part of the vertebral column should experience a tensile stress which explains the replacement of rigid vertebral bodies by a collagenous sheath around the notochord in H. perlo. The backward-ripping dissection could have been common among ancient Elasmobranchii based on the similarly developed postorbital articulation, a longitudinally extended mouth, and the absence of the palatoquadrate symphysis. A biomechanical comparison with the extinct Pucapampella indicates that ancient elasmobranchs could be also specialized in the backward-ripping prey dissection, but their mechanism was different from that inferred for H. perlo. We suggest that in the early evolution of sharks this mechanism was replaced by head-shaking dissection and then later was restored in H. perlo on a new morphological basis. A new position of the postorbital articulation below the vertebral axis is fraught with the braincase elevation when backward ripping the prey, and as a counter-mean, requires formation of suboccipital portions of the axial musculature unknown in other sharks. Homology and origin of these portions is considered.