Male rock hyraxes that maintain an isochronous song rhythm achieve higher reproductive success.

Rhythmic stability (nonrandom temporal structure) is required for many neural and physiological functions, whereas rhythmic irregularities can indicate genetic or developmental deficiencies. Therefore, rhythmic courtship or contest signals are widespread in nature as honest advertisement displays. Examination of bird songs revealed the pervasiveness of categorical rhythmic patterns that can be described as small integer ratios between sequential inter-call intervals. As similar rhythmic profiles are prevalent in human music, it was suggested that a shared functionality could drive both animal songs and human musical rhythms, facilitating synchrony between signallers and enabling easy identification of performance errors. Here we examined whether the rhythmic structure and the rhythmic stability of vocal displays are related to reproductive success in male rock hyraxes (Procavia capensis), which presents an unusual case of a terrestrial singing mammal. We combined long-term parentage analysis of 13 male hyraxes (22 male/years) with an analysis of an audio library of 105 hyrax songs. Male annual reproductive success was determined by the number of offspring that survived to the age of 1 year. The frequency of singing events was used to determine the seasonal singing effort for each male. Songs were analysed for rhythmic structure, focusing on the presence of categorical rhythms and the contribution of rhythmic stability to annual reproductive success. We found that male hyraxes that sing more frequently tend to have more surviving offspring and that the rhythmic profile of hyrax songs is predominantly isochronous with sequential vocal element pairs nearly equally spaced. The ratio of isochronous vocal element transitions (on-integer) to element transitions that deviate from an isochronous pattern (off-integer) in hyrax songs is positively correlated with male reproductive success. Our findings support the notion that isochronous rhythmic stability can serve as an indication of quality in sexually selected signals and is not necessarily driven by the need for multiple caller synchronization. The relative scarcity of nonisochronous rhythmic categories in individually performed hyrax songs raises the question of whether such rhythmic categories could be a product of collective, coordinated signalling, while being selected against in individual performance.

A reproducible and repeatable digital method for quantifying nasal and sinus airway changes following suture palatine expansion.

PURPOSE: The airway complex is modified by palatine expansion. Computer tomography has been used in the past to determine the change in volume, but there was a lack of a specific, reproducible method for this purpose. The present study sought to determine the accuracy, reproducibility, and repeatability of an innovative digital measurement technique for analyzing the volume of maxillary and nasal sinus airways following suture palatine expansion performed with the Hyrax disyuntor appliance. METHODS: Patients underwent preoperative and postoperative cone-beam computed tomography (CBCT) scans. The datasets were subsequently uploaded into a digital treatment planning software to record the volume of the right and left maxillary sinus, as well as the nasal and maxillary sinus airway complex. The Gage Repeatability & Reproducibility statistical analysis methodology was used to evaluate the repeatability and reproducibility of this measurement technique when measuring the volume of maxillary and nasal sinus airways following suture palatine expansion with the Hyrax disyuntor appliance. Additionally, comparative analysis between preoperative and postoperative measures was performed using Student's t-test for statistical analysis. RESULTS: In 5 patients, paired t-tests found statistically significant differences before and after treatment in the volumes of the left maxillary sinus (p = 0.002), right maxillary sinus (p = 0.001), and nasal and maxillary sinus airway complex (p = 0.005) after suture palatine expansion with the Hyrax disyuntor appliance. CONCLUSION: The proposed digital technique is an accurate, repeatable, and reproducible measurement technique for analyzing the volume of maxillary and nasal sinus airways following suture palatine expansion using the Hyrax disyuntor.

Effects of Calcitonin Administration on the Amount of Bone Formation After Sutural Expansion Using Micro-CT.

OBJECTIVE: Calcitonin injections were used in this investigation to see whether they influenced the quantity of bone formation after a rabbit model was subjected to micro-computed tomography expansion. MATERIALS AND METHODS: Research was conducted on a total of 16 white male rabbits. Randomly, 4 groups of 4 rabbits each had their bone-borne expanders triggered by the Hyrax appliances as follows: In the first group (the control), the expansion was (0.5) mm per day for 12 days. In the second group, the same expansion protocol was used with 3 subcutaneous injections of calcitonin). In the third group, the expansion was (2.5) mm per day for 7 days followed by (0.5) mm per day for 7 days. In the fourth group, the same expansion protocol was used with 3 subcutaneous injections of calcitonin. As a result, all groups had their Hyrax devices expanded by 6 mm in total. Sutural separation and new bone growth were examined by micro-computed tomography after 6 weeks of retention. To end the experiment, the rabbits were given a high dosage of phenobarbitone (90 mg/kg). RESULTS: In the calcitonin-receiving group, there was a significant increase in anterior and posterior sutural separation, when compared with non-calcitonin-receiving groups. In the (2.5) mm instant expansion protocol, there was a significant increase in anterior and posterior sutural separation, when compared with the (0.5) mm instant expansion protocol. CONCLUSION: Calcitonin and the instant expansion protocol enhance new bone formation in rabbits.

Effects of novel microimplant-assisted rapid palatal expanders manufactured by 3-dimensional printing technology: A finite element study.

INTRODUCTION: The expansion effects of several new microimplant-assisted rapid palatal expanders (MARPEs) manufactured by 3-dimensional printing technology were evaluated by finite element analysis (FEA). The aim was to identify a novel MARPE suitable for treating maxillary transverse deficiency. METHODS: The finite element model was established using MIMICS software (version 19.0; Materialise, Leuven, Belgium). First, the appropriate microimplant insertion characteristics were identified via FEA, and several MARPEs with the above insertion patterns were manufactured by 3-dimensional printing technology. Then, the stress distribution and displacement prediction of the 4 MARPEs and hyrax expander (model E) were evaluated via FEA: bone-borne (model A), bone-tooth-borne (model B), bone-mucous-borne (model C), bone-tooth-mucous-borne (model D). RESULTS: Monocortical microimplants perpendicular to the cortical bone on the coronal plane resulted in better expansion effects. Compared with a conventional hyrax expander, the orthopedic expansion of each of the 4 MARPEs was far larger, the parallelism was greater, and the posterior teeth tipping rate was lower. Among them, the expansion effects of models C and D were the best; the von Mises peak values on the surfaces of the microimplants were smaller than those of models A and B. CONCLUSIONS: This study may demonstrate that the 4 MARPEs obtained more advantageous orthopedic expansion effects than a hyrax expander. Models C and D obtained better biomechanical effects and had better primary stability. Overall, model D is the recommended expander for treating maxillary transverse deficiency because its structure acts like an implant guide and is beneficial for the accurate insertion of the microimplant.

Dento-skeletal effects of different rapid maxillary expanders for growing patients-which is better?

DESIGN: Single-blind, two-arm parallel-group randomised controlled trial. CASE SELECTION: Patients aged 11-14 years old attending for comprehensive orthodontic treatment between January and July 2018. All subjects needed to have the following: present upper first premolars and first permanent molars; transverse maxillary deficiency; unilateral or bilateral posterior crossbite. The exclusion criteria was: cleft lip or palate, previous orthodontic treatment; congenital deformity; absent permanent teeth. INTERVENTION: Rapid maxillary expansion via two techniques were used and placed by the same orthodontist. Group A were treated via the tooth-bone-borne Hybrid Hyrax expander, Group B had the tooth-borne (hyrax) expander. CBCT scans of the maxilla were taken before treatment and 3 months after the activation phase when the appliances had been removed. DATA ANALYSIS: Analysis of the dental and skeletal changes was completed via measuring pre and post treatment CBCT scans using Dolphin software for Group A and Group B. Measurements included: specific naso-maxillary widths in the first premolar region (i.e. nasal cavity, nasal floor, maxilla, palate), naso-maxillary widths in the first molar region, premolar/molar inclination, buccal cusp distance, and apices distance, as well as suture maturation. Baseline characteristic data was compared using one-way ANOVA. Intergroup comparison of changes was analysed using ANCOVA. P < 0.05 (5%) was considered statistically significant. Inter-rater reliability was assessed using correlation coefficient. RESULTS: Skeletal effects: The Hybrid Hyrax patients (HHG) showed a significantly higher increase in dimensions in the nasal cavity, nasal floor and maxilla in the premolar region only, of 1.5 mm, 1.4 mm and 1.1 mm, respectively, compared to the Hyrax expander patients (HG), to a 5% significance level. The HHG showed a significantly higher increase in dimensions in the nasal cavity of 0.9 mm, in the molar region, compared to the HG. Dental effects: Premolar inclination was significantly higher in the HG, with the difference being -3.2 degrees on the right 1st premolar and -2.5 degrees on the left 1st premolar. The higher the amount of activation, the higher the nasal skeletal changes in the Hybrid Hyrax group. CONCLUSIONS: The Hybrid Hyrax (tooth-bone-borne expander) resulted in increased skeletal dimension changes (i.e. in the nasomaxillary structures in the first premolar region, and nasal cavity in the first molar and first premolar region) and only minimal premolar inclination/tipping compared to the Hyrax (tooth-borne expander). There were however no differences between the expanders for position of premolar or molar apices, or molar crowns.

Dentoskeletal changes due to rapid maxillary expansion in growing patients with tooth-borne and tooth-bone-borne expanders: A randomized clinical trial.

OBJECTIVES: To compare, using cone-beam computed tomography, the dentoskeletal changes in rapid maxillary expansion with tooth-bone-borne (Hybrid Hyrax) and tooth-borne (Hyrax) appliances. SETTING AND SAMPLE POPULATION: Forty-two patients who met the eligibility criteria (aged 11-14 years; transverse maxillary deficiency, posterior crossbite, and presence of upper first premolars and molars) were screened and allocated into two groups: HHG (treatment with Hybrid Hyrax) and HG (treatment with Hyrax). MAIN OUTCOME MEASURES: The primary outcomes included nasomaxillary dimensional changes. CBCT was performed before and 3 months after the activation phase. Measurements were performed using Dolphin® . Baseline data were compared using one-way ANOVA. For intergroup comparison, ANCOVA was used to analyze the initial age, appliance activations (mm), and mid-palatal suture maturation data as covariates. Statistical significance was set at 5%. RESULTS: The premolar region in HHG showed increased skeletal changes than in HG, with the difference being 1.5 mm (0.5; 2.6) in the nasal cavity (P = .004), 1.4 mm (0.3; 2.5) in the nasal floor (P = .019), and 1.1 mm (0.2; 2.1) in the maxilla (P = .022). The molar region in HHG showed increased skeletal changes with the difference being 0.9 mm (0.2; 1.5) in the nasal cavity (P = .005), and 0.9 mm (0; 1.8) in the maxilla (P = .042) than in HG. Premolar inclination was higher in HG. CONCLUSION: Hybrid Hyrax showed more skeletal changes and fewer dental side effects, especially in the first premolar region. The amount of activation influenced the higher nasal skeletal changes in the Hybrid hyrax group.

HYDROMETRA IN ROCK HYRAX (PROCAVIA CAPENSIS) UNDER MANAGED CARE.

In zoos, rock hyrax (Procavia capensis) are commonly maintained in groups and population control is necessary. Here we report on hydrometra prevalence in a group of rock hyraxes. Prevalence of hydrometra in this small group (4/8) far exceeds reproductive pathology prevalence previously reported for this species under managed care. Affected females were nulliparous, but had not been contracepted; instead they were maintained as a single-sex group. The first case presented as sudden death and three additional cases were diagnosed antemortem via ultrasound. Two of these underwent ovariohysterectomy to treat the severe hydrometra. The last case was a mild hydrometra and during follow-up exam was found to have spontaneously resolved. Detailed information regarding clinical presentation, diagnostics and surgical techniques are provided.

Developmental origins and homologies of the hyracoid dentition.

Understanding the origins of morphological specializations in mammals is a key goal in evolutionary biology. It can be accomplished by studying dental homology, which is at the core of most evolutionary and developmental studies. Here, we focused on the evolution and development of the specialized dentition of hyraxes for which dental homologies have long been debated, and could have implications on early placental evolution. Specifically, we analysed dental mineralization sequences of the three living genera of hyraxes and 17 fossil species using X-ray computed microtomography. Our results point out the labile position of vestigial upper teeth on jaw bones in extant species, associated with the frequently unusual premolar shape of deciduous canines over 50 Ma of hyracoid evolution. We proposed two evolutionary and developmental hypotheses to explain these original hyracoid dental characteristics. (a) The presence of a vestigial teeth on the maxilla in front of a complex deciduous canine could be interpreted as extra-teeth reminiscent of early placental evolution or sirenians, an order phylogenetically close to hyracoids and showing five premolars. (b) These vestigial teeth could also correspond to third incisors with a position unusually shifted on the maxilla, which could be explained by the dual developmental origin of these most posterior incisors and their degenerated condition. This integrative study allows discussion on the current evolutionary and developmental paradigms associated with the mammalian dentition. It also highlights the importance of nonmodel species to understand dental homologies.

Social context mediates testosterone's effect on snort acoustics in male hyrax songs.

Testosterone affects physical and motivational states, both of which may strongly influence vocalization structure and acoustics. The loud complex calls (i.e., songs) of male rock hyraxes (Procavia capensis) are used as honest signals for advertising physical and social states. The snort, a low frequency, noisy element of the song, encodes information on the singer's age and social rank via harshness, as measured by jitter (i.e., acoustic frequency stability) and duration; suggesting that the snort concomitantly advertises both vocal stability and aggression. Our past findings revealed that testosterone levels are related to both vocal elements and social status of male hyraxes, suggesting that hormonal mechanisms mediate the motivation for aggressive and courtship behaviors. Here we examined whether long-term androgen levels are related to snort acoustics and song structure by comparing levels of testosterone in hair with acoustic and structural parameters. We found that songs performed by individuals with higher testosterone levels include more singing bouts and longer, smoother snorts, but only in those songs induced by external triggers. It is possible that hyraxes with higher levels of testosterone possess the ability to perform higher-quality singing, but only invest in situations of high social arousal and potential benefit. Surprisingly, in spontaneous songs, hyraxes with high testosterone were found to snort more harshly than low-testosterone males. The context dependent effects of high testosterone on snort acoustics suggest that the aggressive emotional arousal associated with testosterone is naturally reflected in the jittery hyrax snort, but that it can be masked by high-quality performance.

MANDIBULAR SQUAMOUS CELL CARCINOMA IN A ROCK HYRAX ( PROCAVIA CAPENSIS).

A 9-yr-old, entire female captive rock hyrax ( Procavia capensis) was presented with a 1-wk history of sialorrhea. On clinical examination, a mass was identified, encompassing the rostral mandible and intermandibular area, with associated mucosal ulceration, marked gingival recession, and loosening or loss of adjacent teeth. Skull radiography and cytology of fine-needle aspirates of the mass were suggestive of squamous cell carcinoma. Based on a suspected poor prognosis, the animal was humanely euthanized. Postmortem histological examination of samples confirmed a diagnosis of oral squamous cell carcinoma with invasion of mandibular bone. Neoplasia is uncommonly reported in hyraxes, which has led to the assumption that they may share mechanisms of cancer resistance with elephants, their closest extant relatives. This is the first report of squamous cell carcinoma in this species.

Life on the rocks: Multilocus phylogeography of rock hyrax (Procavia capensis) from southern Africa.

Understanding the role of geography and climatic cycles in determining patterns of biodiversity is important in comparative and evolutionary biology and conservation. We studied the phylogeographic pattern and historical demography of a rock-dwelling small mammal species from southern Africa, the rock hyrax Procavia capensis capensis. Using a multilocus coalescent approach, we assessed the influence of strong habitat dependence and fluctuating regional climates on genetic diversity. We sequenced a mitochondrial gene (cytochrome b) and two nuclear introns (AP5, PRKC1) supplemented with microsatellite genotyping, in order to assess evolutionary processes over multiple temporal scales. In addition, distribution modelling was used to investigate the current and predicted distribution of the species under different climatic scenarios. Collectively, the data reveal a complex history of isolation followed by secondary contact shaping the current intraspecific diversity. The cyt b sequences confirmed the presence of two previously proposed geographically and genetically distinct lineages distributed across the southern African Great Escarpment and north-western mountain ranges. Molecular dating suggests Miocene divergence of the lineages, yet there are no discernible extrinsic barriers to gene flow. The nuclear markers reveal incomplete lineage sorting or ongoing mixing of the two lineages. Although the microsatellite data lend some support to the presence of two subpopulations, there is weak structuring within and between lineages. These data indicate the presence of gene flow from the northern into the southern parts of the southern African sub-region likely following the secondary contact. The distribution modelling predictably reveal the species' preference for rocky areas, with stable refugia through time in the northern mountain ranges, the Great Escarpment, as well as restricted areas of the Northern Cape Province and the Cape Fold Mountains of South Africa. Different microclimatic variables appear to determine the distributional range of the species. Despite strong habitat preference, the micro-habitat offered by rocky crevices and unique life history traits likely promoted the adaptability of P. capensis, resulting in the widespread distribution and persistence of the species over a long evolutionary period. Spatio-temporal comparison of the evolutionary histories of other co-distributed species across the rocky landscapes of southern Africa will improve our understanding of the regional patterns of biodiversity and local endemism.

Benzophenone and Fimetarone Derivatives from the Coprophilous Fungus Delitschia confertaspora.

Studies of the genome-sequenced, flutimide-producing coprophilous fungus Delitschia confertaspora (ATCC 74209), originally obtained from a sample of rock hyrax (Procavia capensis) dung collected in Namibia, led to the discovery of three new highly aromatic natural products named delicoferones A-B (1-2) and fimetarone B (3). The new benzophenone derivatives 1 and 2 have a somewhat unusual skeleton that incorporates three aromatic rings linked via two ketone carbonyl groups, while 3 contains a spiro[chroman-3,7'-isochromene]-4,6'(8'H) skeleton reported only once previously. The structures of these compounds were assigned mainly by analysis of 2D NMR and HRESITOFMS data.

DETECTION OF MYCOBACTERIUM AVIUM SUBSPECIES PARATUBERCULOSIS IN ROCK HYRAXES ( PROCAVIA CAPENSIS) IMPORTED FROM SOUTH AFRICA.

Mycobacterium avium subspecies paratuberculosis (MAP) causes chronic, progressive, and consecutively fatal enteritis, especially in ruminants. MAP distribution among wildlife is not yet clear. In this study, three wild-born rock hyraxes ( Procavia capensis) had been imported from South Africa to a German zoological garden. During the quarantine period, four young animals were born. The wild-born animals showed symptoms of mild diarrhea shortly after their arrival in the zoological garden, but all routine parasitological and bacteriologic tests performed were negative. Therefore, the animals were additionally tested for MAP infection. MAP DNA was detected by seminested PCR (snPCR) in a pooled fecal sample of the seven animals. Subsequent PCR analysis of the individual feces samples confirmed the excretion of MAP in two rock hyraxes (one wild-born and one born in captivity). Sequence analysis of the corresponding 278-bp amplicons revealed 100% homology to the reference MAP-K10 IS900 sequence. No antibody response against MAP was detected in the individual serum samples. MAP-specific postmortem lesions were not observed by gross pathology and histology, neither after death nor after euthanization of the animals. Nevertheless, MAP was detected by snPCR and culture in the gastrointestinal tract, urogenital tract, cardiovascular system, and/or respiratory system of three other animals of the group (one wild-born and two born in captivity). This study is the first report confirming MAP occurrence in rock hyraxes. Therefore, it is recommended that veterinarians and zoo employees consider rock hyraxes as a possible source of MAP infection for domestic livestock in South Africa and the valuable animal stock of zoological facilities.

Detection of Bartonella spp. in wild carnivores, hyraxes, hedgehog and rodents from Israel.

Bartonella infection was explored in wild animals from Israel. Golden jackals (Canis aureus), red foxes (Vulpes vulpes), rock hyraxes (Procavia capensis), southern white-breasted hedgehogs (Erinaceus concolor), social voles (Microtus socialis), Tristram's jirds (Meriones tristrami), Cairo spiny mice (Acomys cahirinus), house mice (Mus musculus) and Indian crested porcupines (Hystrix indica) were sampled and screened by molecular and isolation methods. Bartonella-DNA was detected in 46 animals: 9/70 (13%) golden jackals, 2/11 (18%) red foxes, 3/35 (9%) rock hyraxes, 1/3 (33%) southern white-breasted hedgehogs, 5/57 (9%) Cairo spiny mice, 25/43 (58%) Tristram's jirds and 1/6 (16%) house mice. Bartonella rochalimae and B. rochalimae-like were widespread among jackals, foxes, hyraxes and jirds. This report represents the first detection of this zoonotic Bartonella sp. in rock hyraxes and golden jackals. Moreover, DNA of Bartonella vinsonii subsp. berkhoffii, Bartonella acomydis, Candidatus Bartonella merieuxii and other uncharacterized genotypes were identified. Three different Bartonella strains were isolated from Tristram's jirds, and several genotypes were molecularly detected from these animals. Furthermore, this study reports the first detection of Bartonella infection in a southern hedgehog. Our study indicates that infection with zoonotic and other Bartonella species is widespread among wild animals and stresses their potential threat to public health.

Use of deslorelin acetate implants to control aggression in a multi-male group of Rock Hyrax (Procavia capensis).

Aggression among male animals can be difficult to manage in captive populations, and several strategies including separation, castration, and behavioral modification have been used with varying degrees of success. Many aggression issues are normal sequela from hormonal fluctuations occurring when an animal reaches sexual maturity or during the breeding season, and multi-male groups can be especially problematic as the individuals vie for dominance. In this case, aggression in an all-male group of Rock Hyrax (Procavia capensis) has been managed successfully with serial deslorelin implantation for the past 5 years. Zoo Biol. 35:201-204, 2016. © 2016 Wiley Periodicals, Inc.

UTERINE ADENOMYOSIS AND AN ENDOMETRIAL POLYP IN A ROCK HYRAX (PROCAVIA CAPENSIS).

An 8-yr-old nulliparous, female rock hyrax ( Procavia capensis ) had intermittent mucoid to bloody discharge late winter-early spring for two consecutive years. Fragments of necrotic tissue, suspected to be vaginal or rectal in origin, were passed on two occasions. Physical examination, radiographs, and ultrasound did not identify the source of the tissue. Exploratory laparotomy and ovariohysterectomy were performed. On histopathology, a diagnosis of adenomyosis with a uterine polyp was made. Postsurgical complications included incisional infection and renal compromise that were medically managed and resolved. No further vaginal discharge was observed. This is the first report of uterine adenomyosis and endometrial polyp in a rock hyrax.

Estimating vocal repertoire size is like collecting coupons: a theoretical framework with heterogeneity in signal abundance.

Vocal repertoire size is an important behavioural measure in songbirds and mammals with complex vocal communication systems, and has traditionally been used as an indicator of individual fitness, cognitive ability, and social structure. Estimates of asymptotic repertoire size have typically been made using curve fitting techniques. However, the exponential model usually applied in these techniques has never been provided with a theoretical justification based on probability theory, and the model has led to inaccurate estimates. We derived the precise expression for the expected number of distinct signal types observed for a fixed sampling effort: a variation of what is known in the statistical literature as the "Coupon Collector׳s problem". We used empirical data from three species (northern mockingbird, Carolina chickadee, and rock hyrax) to assess the performance of the Coupon Collector model compared to commonly used techniques, such as exponential fitting and repertoire enumeration, and also tested the different models against simulated artificial data sets with the statistical properties of the empirical data. We found that when signal probabilities are dissimilar, the Coupon Collector model provides far more accurate estimates of repertoire size than traditional techniques. Enumeration and exponential curve fitting greatly underestimated repertoire size, despite appearing to have reached saturation. Application of the Coupon Collector model can generate more accurate estimates of repertoire size than the commonly used exponential model of repertoire discovery, and could go a long way towards re-establishing repertoire size as a useful indicator in animal communication research.

Elaboration and Innervation of the Vibrissal System in the Rock Hyrax (Procavia capensis).

Mammalian tactile hairs are commonly found on specific, restricted regions of the body, but Florida manatees represent a unique exception, exhibiting follicle-sinus complexes (FSCs, also known as vibrissae or tactile hairs) on their entire body. The orders Sirenia (including manatees and dugongs) and Hyracoidea (hyraxes) are thought to have diverged approximately 60 million years ago, yet hyraxes are among the closest relatives to sirenians. We investigated the possibility that hyraxes, like manatees, are tactile specialists with vibrissae that cover the entire postfacial body. Previous studies suggested that rock hyraxes possess postfacial vibrissae in addition to pelage hair, but this observation was not verified through histological examination. Using a detailed immunohistochemical analysis, we characterized the gross morphology, innervation and mechanoreceptors present in FSCs sampled from facial and postfacial vibrissae body regions to determine that the long postfacial hairs on the hyrax body are in fact true vibrissae. The types and relative densities of mechanoreceptors associated with each FSC also appeared to be relatively consistent between facial and postfacial FSCs. The presence of vibrissae covering the hyrax body presumably facilitates navigation in the dark caves and rocky crevices of the hyrax's environment where visual cues are limited, and may alert the animal to predatory or conspecific threats approaching the body. Furthermore, the presence of vibrissae on the postfacial body in both manatees and hyraxes indicates that this distribution may represent the ancestral condition for the supraorder Paenungulata.

Paleontological and developmental evidence resolve the homology and dual embryonic origin of a mammalian skull bone, the interparietal.

The homologies of mammalian skull elements are now fairly well established, except for the controversial interparietal bone. A previous experimental study reported an intriguing mixed origin of the interparietal: the medial portion being derived from the neural crest cells, whereas the lateral portion from the mesoderm. The evolutionary history of such mixed origin remains unresolved, and contradictory reports on the presence or absence and developmental patterns of the interparietal among mammals have complicated the question of its homology. Here we provide an alternative perspective on the evolutionary identity of the interparietal, based on a comprehensive study across more than 300 extinct and extant taxa, integrating embryological and paleontological data. Although the interparietal has been regarded as being lost in various lineages, our investigation on embryos demonstrates its presence in all extant mammalian "orders." The generally accepted paradigm has regarded the interparietal as consisting of two elements that are homologized to the postparietals of basal amniotes. The tabular bones have been postulated as being lost during the rise of modern mammals. However, our results demonstrate that the interparietal consists not of two but of four elements. We propose that the tabulars of basal amniotes are conserved as the lateral interparietal elements, which quickly fuse to the medial elements at the embryonic stage, and that the postparietals are homologous to the medial elements. Hence, the dual developmental origin of the mammalian interparietal can be explained as the evolutionary consequence of the fusion between the crest-derived "postparietals" and the mesoderm-derived "tabulars."