Number Of Vertebrae Research Articles

A Morphological Description and the Biology of Poorly Known Deep-Sea Skates of the Genus Bathyraja Ishiyama, 1958 (Rajidae) from the Northwestern Pacific Ocean

A morphological description of the rare deep-sea skates Bathyraja fedorovi, B. andriashevi, and B. tzinovskii from the northwestern Pacific Ocean is presented and data on their biology are considered. The structures of the neurocranium, scapulocoracoid, and pterygopodia are described; data on the number of abdominal and caudal vertebrae, rows of teeth, and coils of the spiral valve in the intestine are provided.

New Moray Eel Species of Strophidon genus (Muraenidae) from Vietnam

A new species, Strophidon dawydoffi sp. n., from Nha Trang Bay (South China Sea, Vietnam) was described. The new species is well distinguished from the cooccurring S. sathete species by a thinner and elongated body, tail lobiform-extended at the end, external absence of vertical fins, a much smaller number of preanal vertebrae, elongated vertebral centra in the middle portion of the caudal region of the vertebral column, the structure of neural arches and parapophyses, variegated coloring of the body and oral cavity, a larger number of teeth in the inner rows on maxillare and dentale, and two or three rows of papillae on the lips. Differences in the number of infraorbital pores and in the shape of the snout between S. sathete specimens are associated with individual variability.

A Fossil Melamphaid Fish of the Genus Scopelogadus (Teleostei: Melamphaidae) from the Neogene Deposits of Sakhalin Island, Russia

The skeleton of a berycomorph fish of the Melamphaidae family was found in sediments of the Middle-Upper Miocene of the Kurasi Formation of Sakhalin Island, Russia. Morphological features, such as a short tall body with a large head, the presence of one dorsal fin with a short base, 19 principal caudal rays, a small number of vertebrae, and single-row jaw teeth in combination with very large cycloid scales enable the assignment of this fossil to the modern genus Scopelogadus. This is the second known record of a fossil skeleton for both the genus Scopelogadus and the family Melamphaidae. The fossil locality is placed approximately 17 degrees north of the range of extant species of the genus. The presence of scopelogadus fish in the Kurasi Formation complex suggests that the accumulation depth of its deposits was at least 200 m.

Resegmentation is an ancestral feature of the gnathostome vertebral skeleton.

The vertebral skeleton is a defining feature of vertebrate animals. However, the mode of vertebral segmentation varies considerably between major lineages. In tetrapods, adjacent somite halves recombine to form a single vertebra through the process of 'resegmentation'. In teleost fishes, there is considerable mixing between cells of the anterior and posterior somite halves, without clear resegmentation. To determine whether resegmentation is a tetrapod novelty, or an ancestral feature of jawed vertebrates, we tested the relationship between somites and vertebrae in a cartilaginous fish, the skate (Leucoraja erinacea). Using cell lineage tracing, we show that skate trunk vertebrae arise through tetrapod-like resegmentation, with anterior and posterior halves of each vertebra deriving from adjacent somites. We further show that tail vertebrae also arise through resegmentation, though with a duplication of the number of vertebrae per body segment. These findings resolve axial resegmentation as an ancestral feature of the jawed vertebrate body plan.

Morphology and genetic investigation of flatfish interspecies hybrids (Pleuronectes platessa X Platichthys flesus) from the Baltic Sea

Plaice (Pleuronectes platessa) and flounder (Platichthys flesus) are economically valuable flatfishes found on the European shelf that are known to naturally and artificially hybridize. Putative hybrids have intermediate coloration which suggest an interspecies status between plaice and flounder. To further investigate this hybridization process, genetic testing was performed on individuals from morphologically identified hybrid samples from the Baltic Sea. Morphological examinations indicate that putative hybrids are morphologically more similar to plaice than flounder. Putative hybrids are difficult to differentiate from plaice without thorough morphological examination. However, the number of vertebrae and scale thrones can morphologically differentiate plaice, flounder, and putative hybrids. Purebred plaice and flounder samples were well-discriminated by nuclear markers TMO-4c4, pthrP, and microsatellites. The analysis results showed that the genetic status of some putative hybrids were in an intermediate position between their parent species populations, which confirmed their hybrid identities. Mitochondrial marker COI results suggest uni-directional maternal material contributions from plaice for this hybridization process. Despite consistent sampling effort at all study sites, putative hybrids were only observed along the western edge of the Baltic Sea and not found in the further west or northern sampling locations.

A comparative analysis of the surgical treatment of preschool children with congenital spinal deformation and isolated hemivertebra from the combined and dorsal approaches

Background. Currently, there are many studies on the evaluation of the results of surgical intervention and the comparative analysis of various surgical techniques for treating children with congenital spinal deformities. However, there is no consensus regarding the choice of surgical access to the abnormal vertebra that considers the duration of surgery, the volume of intraoperative blood loss, the degree of correction achieved during the intervention, the length of metal fixation, and the preservation of the result in the long-term observation period.
 Aim. The goal is to identify the advantages and disadvantages of the dorsal and combined approaches to the surgical treatment of preschool children with congenital deformities of the thoracic and lumbar spine against the background of an isolated violation of the vertebral formation.
 Materials and methods. A retrospective analysis of 56 patients under the age of five with congenital spinal deformities and a history of an isolated hemivertebra in the thoracic and lumbar regions who underwent one-stage hemivertebral extrusion from a dorsal approach (1st group: n = 30) or from a combined approach (2nd group: n = 26) was conducted.
 Results. All patients showed improvement in the sagittal and frontal profiles of the spine. However, during separation in the first group of patients, a progression of the kyphotic component of the deformity in the lumbar spine from 19 to 8 was noted, while the correction value of the curvature of the scoliotic component remained stable. Intraoperative blood loss in the first group of patients was less (234 mL) compared with that in the second group (319 mL), while the duration of surgery was longer (310 min and 185 min, respectively). On average, in the first group, a longer metal structure was used to correct the spinal deformity compared with the second group.
 Conclusions. The correction of the patients congenital spinal deformities with a single hemivertebra from a combined access approach allows a complete correction of the congenital curvature, the fixation of a smaller number of vertebrae, and the maintenance of a stable result in the long-term observation period compared with the dorsal approach. Isolated dorsal access to the hemivertebral body is characterized by less intraoperative blood loss compared with the combined approach, although the length of surgical intervention is increased.

Diaphragm thickness and stiffness in patients with hyperkyphosis due to osteoporotic vertebral fracture: an ultrasonographic and elastographic study.

PurposeThe objective of this study was to evaluate the thickness and stiffness of the diaphragm, using ultrasound (US) and strain elastography (SE) in patients with hyperkyphosis due to osteoporotic vertebral fracture.Material and methodsThis prospective and case-control study was conducted between October 2019 and December 2019. Diaphragm thickness, SE, and strain ratio values of patients with hyperkyphosis due to osteoporotic vertebral fracture were compared with those of the control group.ResultsThere were 42 patients (14 males, 28 females) with a mean age of 81.10 ± 6.3 years in the kyphosis group and 36 subjects (11 males, 25 females) with a mean age of 81.00 ± 5.5 years in the control group. End-inspirium thickness, change level, and thickening ratio of the diaphragm were significantly higher in the control group (p < 0.001 for all). Strain ratio values were significantly higher in the kyphosis group, and the rate of hardest colour code was significantly higher in the control group. The diaphragm thickness at end-inspirium and thickening ratio values correlated positively with the forced expiratory volume in the first second (FEV1, %) and forced vital capacity (FVC, %) values. The strain ratio values correlated inversely with the FEV1 (%) and FVC (%) values. The diaphragm thickness at end-inspirium and thickening ratio values correlated inversely with the Cobb values and number of vertebra fractures. A positive correlation was determined between the strain ratio values and the Cobb values and number of vertebra fractures.ConclusionsUltrasonography is a promising imaging tool to evaluate and quantify the diaphragm function and stiffness in relevant patients.

Vertebrae-Based Body Length Estimation in Crocodylians and Its Implication for Sexual Maturity and the Maximum Sizes.

SynopsisBody size is fundamental to the physiology and ecology of organisms. Crocodyliforms are no exception, and several methods have been developed to estimate their absolute body sizes from bone measurements. However, species-specific sizes, such as sexually mature sizes and the maximum sizes were not taken into account due to the challenging maturity assessment of osteological specimens. Here, we provide a vertebrae-based method to estimate absolute and species-specific body lengths in crocodylians. Lengths of cervical to anterior caudal centra were measured and relations between the body lengths (snout–vent and total lengths [TLs]) and lengths of either a single centrum or a series of centra were modeled for extant species. Additionally, states of neurocentral (NC) suture closure were recorded for the maturity assessment. Comparisons of TLs and timings of NC suture closure showed that most extant crocodylians reach sexual maturity before closure of precaudal NC sutures. Centrum lengths (CLs) of the smallest individuals with closed precaudal NC sutures within species were correlated with the species maximum TLs in extant taxa; therefore, the upper or lower limit of the species maximum sizes can be determined from CLs and states of NC suture closure. The application of the current method to noncrocodylian crocodyliforms requires similar numbers of precaudal vertebrae, body proportions, and timings of NC suture closure as compared to extant crocodylians.

Polymorphism of Candidate Genes Related to the Number of Teat, Vertebrae and Ribs in Pigs

Polymorphism of Candidate Genes Related to the Number of Teat, Vertebrae and Ribs in Pigs

Increasing Dietary Fish Oil Reduces Adiposity and Mitigates Bone Deterioration in Growing C57BL/6 Mice Fed a High-Fat Diet

Intake of total fat is linked to obesity and inversely associated with bone density in humans. Epidemiologic and animal studies show that long-chain n-3 (ω-3) PUFAs supplied as fish oil (FO) are beneficial to skeletal health. This study tested the hypothesis that increasing dietary FO would decrease adiposity and improve bone-related outcomes in growing obese mice. Male C57BL/6 mice at 6 wk old were assigned to 6 treatment groups and fed either a normal-fat diet (3.85 kcal/g and 10% energy as fat) or a high-fat diet (HF; 4.73 kcal/g and 45% energy as fat) containing either 0%, 3%, or 9% energy as FO (0FO, 3FO, and 9FO, respectively) ad libitum for 6 mo. Bone structure, body composition, and serum bone-related cytokines were measured. The HF diet increased the expression of the adipose tissue tumor necrosis factor α (Tnfa) and serum concentrations of leptin and tartrate-resistant acid phosphatase (TRAP), and decreased serum concentrations of osteocalcin and bone-specific alkaline phosphatase (P<0.05). FO decreased fat mass (P<0.05), serum TRAP (P<0.05), and adipose tissue Tnfa expression (P<0.01). Bone content of long-chain n-3 PUFAs was increased and n-6 PUFAs were decreased with the elevation in dietary FO content (P<0.01). Compared with mice fed 9FO, animals fed 3FO had higher femoral bone volume/total volume (25%), trabecular number (23%), connectivity density (82%), and bone mass of second lumbar vertebrae (12%) and lower femoral trabecular separation (-19%). Mice fed the 3FO HF diet had 42% higher bone mass than those fed the 0FO HF diet. These data indicate increasing dietary FO ≤3% energy can decrease adiposity and mitigate HF diet-induced bone deterioration in growing C57BL/6 mice possibly by reducing inflammation and bone resorption. FO at 9% diet energy had no further beneficial effects on bone of obese mice.

Long-term Results of Spine Stapling for AIS to Skeletal Maturity and Beyond.

We looked at long-term follow-up of spine stapling with Nitinol Staples. This was a cohort of all adolescent idiopathic scoliosis (AIS) patients with curves at high risk to progress based on curve magnitude, premenarchal status in all females, failure of brace treatment, and skeletal immaturity. This is a single surgeon retrospective review of consecutive AIS patients treated with Nitinol staples for progressive scoliosis. Fourteen patients, 16 curves from 2005 to 2008 were eligible. Minimum curve for stapling was 30 degrees. Standard preoperative, intraoperative, and postoperative data were collected. All patients were followed for a minimum of 36 months and to skeletal maturity. Three groups were: improved (group 1), correction of any amount; minimal progression (group 2), progression ≤10 degrees; and failure (group 3), ≥10 degrees of progression. A total of 13 thoracic curves and 2 compensatory lumbar curves met the inclusion criteria (94%). Average follow-up was 61 months. The mean preoperative main thoracic curve was 35 degrees. All but 1 patients progressed at least 9 degrees in a brace prior to stapling. Females were all premenarchal, 10 patients were Risser 0 and 3 Risser 1. The average number of vertebrae stapled per curve was 6. Group 1 included 6 curves (40%). Group 2, 5 curves (33%). Group 3, 4 curves (27%). Three patients went on to uncomplicated fusion. Final curve measurement at the end of follow-up or before fusion (P=0.0037), curve progression (P≤0.001), and percentage of coronal correction on first postoperative standing radiograph (P=0.042) were the significant differences between groups 1+2 (successful) versus group 3 (failures). In total, 73% of this group either progressed ≤10 degrees or improved. This is the first study that follows AIS patients treated with spine stapling to skeletal maturity. Staples likely changed natural history in some of our patients. Initial percentage of correction on first standing postoperative PA x-rays was the only predictor of success. Stapling was safe without any long-term complications. Level III-retrospective study.

Radiological evaluation of anatomical changes in implant and adjacent segments after rigid fusion

Aim: We aimed to determine the anatomical remodeling seen after lumbar spine stabilization in detail. Using magnetic resonance images, it is also aimed to reveal this remodeling is not only limited to the adjacent segment and also happens in the upper instrumented vertebra region. At the end of this study, it is suggested to develop new radiological parameters to predict the changes in the adjacent segment and upper instrumented vertebra regions.Materials and Methods: Twenty cases operated for degenerative lumbar stenosis were included in our study. Quantitative data were obtained by radiological measurements by a radiologist and neurosurgeon. On magnetic resonance images, the anatomical structures changed by remodeling were compared before and after the operation during (6-26 months) postoperative period. Unlike previous studies, anterior, middle and posterior disc heights; Cobb angle in the adjacent segment, spinal canal area, bilateral neural foramen, facet joint areas and flavum thicknesses were evaluated.Results: From the sixth month after lumbar fusion, it was observed that angles and anatomical structures were changed in adjacent segment. Also, it was observed that the areas with neural structures expanded in the upper instrumented vertebra region. The degeneration in adjacent segment and relaxation in the upper instrumented vertebra region were found to be statistically significant. A statistically strong positive correlation was found between the number of vertebrae included in the lumbar fusion and the mean height of the adjacent segment disc (r: 0.526, p: 0.017).Conclusion: After comparing the measurements in adjacent segment and upper instrumented vertebra regions before and after the operation, it was concluded that the remodeling was statistically significant. We suggest that the parameters in our study can be used as a scoring method for early detection of adjacent segment degeneration and/or disease. Thus, it will be possible to create follow-up indicators findings after fusion.

Augmented Reality Surgical Navigation in Spine Surgery to Minimize Staff Radiation Exposure.

Prospective observational study. To assess staff and patient radiation exposure during augmented reality surgical navigation in spine surgery. Surgical navigation in combination with intraoperative three-dimensional imaging has been shown to significantly increase the clinical accuracy of pedicle screw placement. Although this technique may increase the total radiation exposure compared with fluoroscopy, the occupational exposure can be minimized, as navigation is radiation free and staff can be positioned behind protective shielding during three-dimensional imaging. The patient radiation exposure during treatment and verification of pedicle screw positions can also be reduced. Twenty patients undergoing spine surgery with pedicle screw placement were included in the study. The staff radiation exposure was measured using real-time active personnel dosimeters and was further compared with measurements using a reference dosimeter attached to the C-arm (i.e., a worst-case staff exposure situation). The patient radiation exposures were recorded, and effective doses (ED) were determined. The average staff exposure per procedure was 0.21 ± 0.06 μSv. The average staff-to-reference dose ratio per procedure was 0.05% and decreased to less than 0.01% after a few procedures had been performed. The average patient ED was 15.8 ± 1.8 mSv which mainly correlated with the number of vertebrae treated and the number of cone-beam computed tomography acquisitions performed. A low-dose protocol used for the final 10 procedures yielded a 32% ED reduction per spinal level treated. This study demonstrated significantly lower occupational doses compared with values reported in the literature. Real-time active personnel dosimeters contributed to a fast optimization and adoption of protective measures throughout the study. Even though our data include both cone-beam computed tomography for navigation planning and intraoperative screw placement verification, we find low patient radiation exposure levels compared with published data. 3.

Biometrical parameters and biological indices of the migratory species Conger conger (Linnaeus, 1758) from the northern coastal waters of Tunisia (Mediterranean Sea) / Paramètres biométriques et indices biologiques de l’espèce migratrice Conger conger (Linnaeus, 1758) des eaux côtières du nord de la Tunisie (mer Méditerranée)

The European conger eel Conger conger represents an important economic resource. Previous studies have provided some information about the biometry of C. conger. This paper presents the first research on biometrical parameters and biological indices of this species in Tunisia. Our sample includes 353 specimens, among them 66.57% females, 32.29% of undetermined sex and only 1.13% males. The length and weight of specimens ranged from 25.5 to 135 cm and from 17.26 to 5087 g, respectively. For the meristic characteristics, the number of pre-pectoral pores was 6, the total number of pre-anal pores ranged between 44 and 47 and the total number of vertebrae varied between 148 and 154. Five allometric relationships were examined. The comparisons of slope and intercept show differences between individuals of determined sex (males and females grouped) and those of undetermined sex. Analysis of the weight-length relationship showed a positive allometric growth. Our data provided the first investigation on the seasonal variation of three bio-physiological indices ; the condition factor does not show variations among seasons, the gonadosomatic index variation reinforces the hypothesis that sexual maturation of C. conger females occurs during the migration from coastal waters towards spawning areas in the deep sea and the hepatosomatic index was highest in spring for females. Since C. conger is widely distributed in the Mediterranean Sea and the Atlantic Ocean, our contribution allows useful comparisons and clarifies the morphological and bio-physiological aspects of this species.

Gulper, ripper and scrapper: anatomy of the neck in three species of vultures.

The head-neck system of birds is a highly complex structure that performs a variety of demanding and competing tasks. Morphofunctional adaptations to feeding specializations have previously been identified in the head and neck, but performance is also influenced by other factors such as its phylogenetic history. In order to minimize the effects of this factor, we here analyzed the anatomy of three closely related vultures that distinctly differ in feeding strategy. Vultures, as obligate scavengers, have occupied a special ecological niche by exclusively feeding on carrion. However, competition among sympatric vultures led to ecological differences such as preference of certain types of food from a carcass. Via comparative dissections we systematically described the craniocervical anatomy in the Griffon vulture (Gyps fulvus), the Cinereous vulture (Aegypius monachus) and the Hooded vulture (Necrosyrtes monachus) that exploit the same food resources in different ways. Our results revealed differences in the number of cervical vertebrae, in the morphology of the atlas-axis complex as well as in the neck musculature despite overall similarities in the musculoskeletal system. Gulpers, rippers and scrappers adopt specific postures while feeding from a carcass, but the cervical vertebral column is indispensable to position the head during all kinds of behavior. The great range of demands may explain the conservation of the overall muscle topography of the neck across the studied taxa.

Is variation in tail vertebral morphology linked to habitat use in chameleons?

Chameleons (Chamaeleonidae) are known for their arboreal lifestyle, in which they make use of their prehensile tail. Yet, some species have a more terrestrial lifestyle, such as Brookesia and Rieppeleon species, as well as some chameleons of the genera Chamaeleo and Bradypodion. The main goal of this study was to identify the key anatomical features of the tail vertebral morphology associated with prehensile capacity. Both interspecific and intra-individual variation in skeletal tail morphology was investigated. For this, a 3D-shape analysis was performed on vertebral morphology using μCT-images of different species of prehensile and nonprehensile tailed chameleons. A difference in overall tail size and caudal vertebral morphology does exist between prehensile and nonprehensile taxa. Nonprehensile tailed species have a shorter tail with fewer vertebrae, a generally shorter neural spine and shorter transverse processes that are positioned more anteriorly (with respect to the vertebral center). The longer tails of prehensile species have more vertebrae as well as an increased length of the processes, likely providing a greater area for muscle attachment. At the intra-individual level, regional variation is observed with more robust proximal tail vertebrae having longer processes. The distal part has relatively longer vertebrae with shorter processes. Although longer, the small size and high number of the distal vertebrae allows the tail to coil around perches.

Readmission following complex spine surgery in a prospective cohort of 679 patients – 2-years follow-up using the Spine AdVerse Event Severity (SAVES) system

BACKGROUND CONTEXTRecent studies suggest that prospective registration more accurately reflects the true incidence of adverse events (AEs). To our knowledge, no previous study has investigated prospectively registered AEs' influence on hospital readmission following spine surgery. PURPOSETo determine the frequency and type of unplanned readmissions after complex spine surgery, and to investigate if prospectively registered AEs can predict readmissions. DESIGNThis is a prospective, consecutive cohort study. PATIENT SAMPLEWe conducted a single-center study of 679 consecutive patients who underwent complex spine surgery defined as conditions deemed too complicated for surgery at a secondary institute, or patients with severe comorbidities requiring multidisciplinary observation and treatment. OUTCOME MEASURESThe outcomes in this study were (1) readmission to any hospital department within 30 days of discharge and (2) readmission to a surgical spine center at any time in follow-up. METHODSAll patients undergoing complex spine surgery, at our tertiary referral center, were consecutively, and prospectively, included from January 1 to December 31, 2013. Demographics and perioperative AEs were registered using the Spine AdVerse Events Severity (SAVES) system. Patients were followed for a minimum of two years. A competing risk survival model was used to estimate rates of readmissions with death as a competing risk. Patient characteristics, surgical parameters and perioperative AEs were analyzed to identify factors associated with readmission. Analyses of 30-day readmission were performed using logistic regression models. A proportional odds model, with death as competing risk, was used for readmissions to a spine center at any time in follow-up. Results were reported as odds ratios with 95% confidence intervals (95% CI). RESULTSWithin 2 years of index discharge, 443 (65%) were readmitted. Only 20% of readmissions were to a spine center. Cumulative incidence (95% CI) of readmission was estimated to 13% (10%–16%) at 30 days, 26% (23%–30%) at 90 days, 50% (46%–54%) at 1 year, and 59% (55%–63%) at 2 years following discharge. Rates were markedly lower for readmissions to a spine center. Increased odds of 30-day readmission were correlated to intraoperative hypotension (p=.02) and major intraoperative blood loss (p<.01). Readmission to a spine center was associated with the number of instrumented vertebrae (p=.047), major intraoperative AE (p=.01), and intraoperative hypotension (p<.01). CONCLUSIONSTo the best of our knowledge, this is the first study to analyze prospectively registered AEs' association to readmission up to 2 years after complex spine surgery. We found that readmissions were more frequent than previously reported when including readmissions to any department or hospital. Factors related to major intraoperative blood loss were associated to increased odds of readmission. This should be considered during planning of postoperative observation and care.

Aegicetus gehennae, a new late Eocene protocetid (Cetacea, Archaeoceti) from Wadi Al Hitan, Egypt, and the transition to tail-powered swimming in whales.

Aegicetus gehennae is a new African protocetid whale based on a partial skull with much of an associated postcranial skeleton. The type specimen, Egyptian Geological Museum, Cairo [CGM] 60584, was found near the base of the early-Priabonian-age (earliest late Eocene) Gehannam Formation of the Wadi Al Hitan World Heritage Site in Egypt. The cranium is distinctive in having ventrally-deflected exoccipitals. The vertebral column is complete from cervical C1 through caudal Ca9, with a vertebral formula of 7:15:4:4:9+, representing, respectively, the number of cervical, thoracic, lumbar, sacral, and caudal vertebrae. CGM 60584 has two more rib-bearing thoracic vertebrae than other known protocetids, and two fewer lumbars. Sacral centra are unfused, and there is no defined auricular surface on the ilium. Thus there was no weight-bearing sacroiliac joint. The sternum is distinctive in being exceptionally broad and flat. The body weight of CGM 60584, a putative male, is estimated to have been about 890 kg in life. Long bones of the fore and hind limbs are shorter than expected for a protocetid of this size. Bones of the manus are similar in length and more robust compared to those of the pes. A log vertebral length profile for CGM 60584 parallels that of middle Eocene Maiacetus inuus through the anterior and middle thorax, but more posterior vertebrae are proportionally longer. Vertebral elongation, loss of a sacroiliac articulation, and hind limb reduction indicate that Aegicetus gehennae was more fully aquatic and less specialized as a foot-powered swimmer than earlier protocetids. It is doubtful that A. gehennae had a tail fluke, and the caudal flattening known for basilosaurids is shorter relative to vertebral column length than flattening associated with a fluke in any modern whale. Late protocetids and basilosaurids had relatively long skeletons, longer than those known earlier and later, and the middle-to-late Eocene transition from foot-powered to tail-powered swimming seemingly involved some form of mid-body-and-tail undulation.

Giant extinct caiman breaks constraint on the axial skeleton of extant crocodylians.

The number of precaudal vertebrae in all extant crocodylians is remarkably conservative, with nine cervicals, 15 dorsals and two sacrals, a pattern present also in their closest extinct relatives. The consistent vertebral count indicates a tight control of axial patterning by Hox genes during development. Here we report on a deviation from this pattern based on an associated skeleton of the giant caimanine Purussaurus, a member of crown Crocodylia, and several other specimens from the Neogene of the northern neotropics. P. mirandai is the first crown-crocodylian to have three sacrals, two true sacral vertebrae and one non-pathological and functional dorsosacral, to articulate with the ilium (pelvis). The giant body size of this caiman relates to locomotory and postural changes. The iliosacral configuration, a more vertically oriented pectoral girdle, and low torsion of the femoral head relative to the condyles are hypothesized specializations for more upright limb orientation or weight support.

Divergent evolutionary morphology of the axial skeleton as a potential key innovation in modern cetaceans.

Cetaceans represent the most diverse clade of extant marine tetrapods. Although the restructuring of oceans could have contributed to their diversity, other factors might also be involved. Similar to ichthyosaurs and sharks, variation of morphological traits could have promoted the colonization of new ecological niches and supported their diversification. By combining morphological data describing the axial skeleton of 73 cetacean species with phylogenetic comparative methods, we demonstrate that the vertebral morphology of cetaceans is associated with their habitat. All riverine and coastal species possess a small body size, lengthened vertebrae and a low vertebral count compared with open ocean species. Extant cetaceans have followed two distinct evolutionary pathways relative to their ecology. Whereas most offshore species such as baleen whales evolved towards an increased body size while retaining a low vertebral count, small oceanic dolphins underwent deep modifications of their axial skeleton with an extremely high number of short vertebrae. Our comparative analyses provide evidence these vertebral modifications have potentially operated as key innovations. These novelties contributed to their explosive radiation, resulting in an efficient swimming style that provides energetic advantages to small-sized species.