Cervical Centra Research Articles

The elasmosaurid plesiosaur Aristonectes Cabrera from the latest Cretaceous of South America and Antarctica

ABSTRACT Aristonectes parvidens Cabrera, 1941, and Morturneria seymourensis (Chatterjee and Small, 1989), two plesiosaurs from the Maastrichtian of South America and Antarctica whose phylogenetical position is controversial, are reviewed and found to be congeneric and conspecific. Most differences between the two type specimens are interpreted as related to ontogenetic growth: Morturneria is based on an immature, whereas Aristonectes is based on an adult, probably an old individual. Aristonectes exhibits an unique set of characters among Plesiosauria: a low and wide ogival skull, a paired vomeronasal fenestra, a mandible high anteriorly with a very short and high symphysis, a homodont dentition composed of numerous, strongly outwardly directed and poorly ornamented teeth (dental formula: 10–13 premaxillary, at least 51 maxillary and probably 60–65 dentary teeth, depending upon individual ontogeny). Moreover, Aristonectes shares several synapomorphies with the elasmosaurid clade, mainly strongly binocular-shaped and platycoelous cervical centra with lateral ridges. In contrast to cryptoclidids, it retains some plesiomorphic characters (e.g., horizontal jugal and poorly ventrally excavated cheek, glenoid fossa at about the same level as the alveolar row). The dental morphology and peculiar occlusal pattern, forming an interlocking trap, suggest that Aristonectes strained a diet of small, soft organisms from the water.

The detailed anatomy of Rhamphorhynchus : axial pneumaticity and its implications

Abstract An acid- and transfer-prepared, juvenile Rhamphorhynchus muensteri , despite some fragmentation, is in an excellent state of three-dimensional preservation, exposing exquisite anatomical details hitherto unknown in other pterosaurs. Here we describe the axial pneumatizations of the cervical and anterior dorsal vertebrae and the sternum. The interior of the cervical centra is subdivided into a pair of large camerae, presumably by air sacs entering by large pleurocoels in the sides of the centra. This so-called ‘camerate’ type of pneumatization is hitherto unknown in pterosaurs. Another excavation enters from the ventral side into the base of the neural arch and stretches between the pre- and postzygapophyses. This type of cavity also penetrates from the ventral side into the base of the first few transverse processes of the dorsal vertebrae, although these lack central pleurocoels. The cristospine also has a complex pneumatic foramen. Skeletal pneumaticity is most probably a result of a highly derived pulmonary system, as in extant birds. Morphologically similar pneumatic features are present in most saurischian dinosaurs and it is possible that they are the result of convergence. Because basal members of the various groups, including Triassic pterosaurs, appear to lack skeletal pneumaticity, convergence seems likely, although the stem-ornithodiran parsimoniously possessed a more bird-like than ‘reptile’-like pulmonary system, albeit non-invasive. This points to possible tachymetabolism in these forms, which is in accord with the distribution of other factors such as integumentary structures and bone histology. It is concluded that evolution of this suite of advanced features, surprisingly, was among the earliest events in the ornithodiran lineage soon after it split off from its crocodilian sister-group.

Developmental toxicity evaluation of inhaled toluene diisocyanate vapor in CD rats.

Mated female CD (Sprague-Dawley) rats, 25/group, were exposed to toluene diisocyanate (TDI) vapor, for six h/day on gestational days (gd) 6 through 15, at 0.00, 0.02, 0.10, or 0.50 p.p.m.. Maternal clinical signs, body weights, and feed and water consumption were recorded throughout gestation. At termination (gd 21), maternal body, gravid uterine, and liver weights were recorded. Corpora lutea were counted, and implantation sites were identified: resorptions and dead and live fetuses. All live fetuses were examined for external alterations. One-half of the live fetuses/litter were examined for visceral (including craniofacial) alterations. The remaining intact fetuses/litter were stained with alizarin red S and examined for ossified skeletal alterations. Maternal toxicity at 0.50 ppm consisted of reduced body weights, body weight gains, feed consumption, and clinical signs of toxicity. Water consumption was unaffected. Gestational parameters exhibited no significant treatment-related changes, including pre- and postimplantation loss, sex ratio/litter, or fetal body weights/litter. Incidences of individual malformations, malformations by category (external, visceral, and skeletal), total malformations, individual external and visceral variations, variations by category, and total variations were unaffected. Of 111 skeletal variants observed, only 1, incidence of poorly ossified cervical centrum 5, was increased at 0.50 ppm, indicating possible minimal fetotoxicity, although it occurred in the absence of any other indications of developmental toxicity. Therefore, exposure to TDI vapor by inhalation, during major organogenesis in CD rats, resulted in maternal toxicity and minimal fetotoxicity at 0.50 ppm no observed adverse effect level (NOAEL) for maternal and developmental toxicity was 0.10 ppm. No treatment-related embryotoxicity or teratogenicity was observed.

Remains of Sauropoda (Reptilia, Saurischia) in the Lower Cretaceous (Upper Hauterivian/Lower Barremian) Limestones of SW Istria (Croatia)

Remains belonging 10 sauropod dinosaurs have recently been discovered in Upper Hauterivian/Lower Barremian (Lower Cretaceous) limestones of SW Istria (Croatia). The material consists of a complete cervical vertebra, a nearly complete cervical centrum, fragmcnls of poss ible cervical ribs, three partial dorsa! and five more or less incomplete caudal vertebrae, parts of caudal neural spines, a chevron, the distal pari of a femur, the proximal portion of a tibia and other fragments of bones. The bones were collected randomly from the sea bottom, therefore despite the fact that they come from the same outcrop, the same level and probably the same bed, they cannot be assigned with certainty to the same taxon. Their vastly different sizes indicate the presence of several individuals while different morphologies suggest the probable presence of more than one taxon. The complete cervical and the anterior 10 mid-caudal vertebrae present a more strict affinity with Brachiosauridae, a proximal cervical centrum resembles those of Cholldros(eosourtls, and a caudal neural spine is similar to those of the camarasaurids. The dorsal vertebrae have peculiar features (a very tall neural arch, well developed laminar complex, etc.) and characters suggesting their assignation to basal Titanosauriformes and, possibly, to Diplodocimorpha. A posterior dorsal vertebra testifies the presence of a new Diplodocimorph similar to Rehbachisollrlls but more primitive.

Developmental toxicity study in Fischer 344 rats by whole-body exposure to N,N-dimethylethanolamine vapor.

Timed-pregnant Fischer 344 rats were exposed whole body to N,N-dimethylethanolamine vapor for 6 h per day on gestational days 6-15 at mean (+/- SD) analytically measured concentrations of 10.4 +/- 0.86, 29.8 +/- 2.14 and 100 +/- 4.9 ppm. Dams were sacrificed on gestational day 21. There was no maternal mortality in any exposed groups. Maternal toxicity observed in the 100 ppm group included reduced body weight during and after exposures, reduced weight gain during exposure and ocular changes (darkened, cloudy and hazy eyes, slight corneal vascularization and fixed, dilated pupils). Ocular effects were also noted in the other two exposure groups; the effects were quite marked at 30 ppm but only minimal and transient at 10 ppm. There were no effects of treatment on any gestational parameters, including pre- and postimplantation loss or sex ratio. Fetal body weights per litter were statistically significantly increased at 100 ppm relative to controls. There were no increases in the incidences of total malformations by category (external, visceral or skeletal) or individually. The incidence of six skeletal variations out of 120 noted differed in exposed groups relative to that of control. Four of these variations were decreases in incidence; only one fetal variation, the split (bipartite) cervical centrum, was elevated at 100 ppm relative to controls. In the absence of any other indications of delayed ossification or fetal body weights, the observed fetal variation does not suggest a consistent pattern of fetal toxicity. Hence, the no-observed-adverse-effect level is around 10 ppm for maternal toxicity and at or above 100 ppm for embryofetal toxicity and teratogenicity.

Potentiating effect of caffeine on the teratogenicity of acetazolamide in C57BL/6J mice

Pregnant C57BL/6J mice were treated with 0 or 50 mg of caffeine (CAFF) per kg, and 0, 200 mg/kg (L) or 1,000 mg/kg (H) of acetazolamide (ACZM) during day 9 of gestation (9DPC). Individual fetuses were examined for gross morphological abnormalities and skeletal variations. The increase in fetal malformations seen, especially right forelimb electrodactyly, was augmented at both dose levels of acetazolamide by concomitant exposure to caffeine. Both frequency and severity of ectrodactyly were potentiated by caffeine. Skeletal examination revealed a reduction of the number of ossified cervical and caudal vertebral centra among litters exposed to ACZM at either dose. In either case (ACZM-H, ACZM-L) that effect was augmented by co-administration of CAFF. The first cervical vertebra (C1) appeared to provide the most sensitive index of teratogenic exposure. This study provides evidence that a subteratogenic dose of caffeine can potentiate the teratogenic effect of acetazolamide in C57BL/6J mice when dams are treated on day 9 of gestation. In addition, skeletal examination provided evidence that simultaneous treatment with both agents delayed fetal development. Many litters exposed to ACZM or both agents displayed a reduction in skeletal ossification even in the absence of gross morphological abnormalities, suggesting that ossification can be used as an indicator of prenatal exposure to potentially harmful substances in the C57BL/6 mouse strain.

Developmental toxicity of pentostatin (2′‐deoxycoformycin) in rats and rabbits

The developmental toxicity of the potent adenosine deaminase (ADA) inhibitor, pentostatin (2'-deoxycoformycin), was investigated in pregnant rats and rabbits administered daily iv doses during organogenesis. Rats received 0, 0.01, 0.10, or 0.75 mg/kg on gestation days 6-15 and rabbits received 0, 0.005, 0.01, or 0.02 mg/kg on gestation days 6-18 and maternal and fetal parameters were evaluated on gestation day 21 (rats) or 30 (rabbits). Live fetuses were examined for external, visceral, and skeletal malformations and variations. In rats, maternal body weight gain and food consumption were significantly suppressed at doses of 0.10 and 0.75 mg/kg during the treatment period but returned to control levels during posttreatment. Increased postimplantation loss and decreased numbers of live fetuses, litter size, and fetal body weight were observed at 0.75 mg/kg. A statistically significant increase in the incidence of vertebral malformations occurred at 0.75 mg/kg. The incidence of certain skeletal variations (extra presacral vertebrae, extra ribs, hypoplastic vertebrae) was also increased at 0.75 mg/kg. Ossification of cervical centra was reduced at 0.75 mg/kg compared with controls. In rabbits, marked maternal toxicity (death, body weight loss, and decreased food consumption) and reproductive toxicity (abortion and premature delivery) occurred in all pentostatin-treated groups. However, there were no significant effects on number of live fetuses, pre- or postimplantation loss, litter size, or fetal body weights in the animals with live litters. There was also no apparent increase in the incidence of malformations or variations in the live fetuses of pentostatin-treated rabbits. Thus, these studies demonstrate developmental toxicity of pentostatin in rats and rabbits, and teratogenicity in rats, at maternally toxic doses.

Prenatal ossification as an indicator of exposure to toxic agents.

Following exposure to bromodeoxyuridine (BUDR), acetazolamide (ACZM), trypan blue (TRBL), cortisone (CORT), or diphenylhydantoin (DPH), alizarin-stained, cleared fetuses were examined at 18 days postcoitus for unossified cervical vertebral centra; number of ossified caudal vertebrae; number of ribs; and ossification of sternebrae, metatarsals, metacarpals, and phalangeal rows. At all teratogenic doses, in no vehicle-treated groups, and rarely in lower-dose groups, there were significant increases in frequency of unossified cervical centra, the first vertebra (C1) being most often affected, and C7 least often affected. In the high-dose CORT group, there was a significant correlation between unossified C1 and cleft palate. No association between abnormality and reduced ossification of cervical vertebrae was seen in other series examined, nor was there any correlation between litter size and abnormality. With minor complications, the number of ossified caudal vertebrae was significantly reduced after exposure at teratogenic dose levels to all compounds except DPH. Although caudal and cervical ossification were correlated with each other in those series examined, neither was correlated with abnormality. Frequency of 14 ribs was increased in BUDR, ACZM, and TRBL but not CORT or DPH. Other parameters were essentially unaffected. Significantly increased frequency of abnormality, when contrasted with untreated or vehicle-treated groups, was seen at high-dose levels in all but DPH treatments, and mortality was increased in ACZM D9-11, TRBL, and CORT. These studies show that reduced ossification of cervical centra is an excellent indicator of prenatal exposure to noxious substances, and caudal vertebrae appear to be useful as well. Increased frequency of 14 ribs occurred for all strong teratogens utilized if they were administered on day 7 or day 8 postcoitus.

The effects of cyclopiazonic acid on pregnancy and fetal development of Fischer rats.

To assess the potential effect of cyclopiazonic acid (CPA) on pregnancy and fetal development, Fischer-344 rats were dosed daily with 0, 1, 5, or 10 mg CPA/kg body weight on either d 8-11 or d 12-15 of pregnancy (sperm day = d 1). There were significant (p less than 0.05) decreases in feed consumption by high-dose dams of both groups. One high-dose rat in each group died prior to term, and signs of toxicity were observed in other high-dose animals. Animals that died had histologic lesions in the liver, spleen, kidney, and other organs. Remaining dams were killed on d 21. Compared to controls, there were no significant differences in pup weights, percentage pre- or postimplantation losses, or fetal deaths. Significant differences in skeletal development included retardation of ossification of cervical centra (d 12-15) and caudal vertebrae (d 8-11) in the two highest dose groups. Retardations of development were the most common manifestations of embryotoxicity. Since significant maternal toxicity occurred at the highest dose level in the absence of fetal malformations, the teratogenic potential of CPA is low.

Relation of dosage and time of administration of diphenylhydantoin to its teratogenic effect in mice.

AbstractDiphenylhydantoin was teratogenic and caused prenatal death in Swiss‐Webster mice. Most deaths resulted after single treatment on days 10, 11, 12, 14, and 15. Fetal body weight was significantly reduced in a dose‐related manner after single treatment on days 9 to 15. Single injections of diphenylhydantoin produced open eye, ectrodactyly, cleft lip, cleft palate, hydronephrosis, and internal hydrocephalus. Skeletal defects noted were incomplete ossification of sternebrae or cervical centra, unfused sternebrae, and fused vertebrae. Long bones were shortened in a day‐ and dosage‐dependent fashion. Mortality, teratogenesis, and effect on fetal growth were day‐ and dosage‐dependent as was the spectrum of anomalies produced.

PARTITION OF THE GENUS CLEMMYS AND RELATED PROBLEMS IN THE TAXONOMY OF THE AQUATIC TESTUDINIDAE

On the basis of presence or absence of a muscular apophysis of the basisphenoid in the floor of the recessus scalae tympani, contact of the angular bone with Mackel's cartilage, nature of the joint between the fifth and sixth cervical centra, and pygal pattern, the testudinid subfamily Emydinae as currently recognized may be divided into two subfamilies, the Batagurinae and the Emydinse. The Batagurinae are almost entirely Old‐World, but have one New‐World genus, Rhinoclemys (the New‐World turtles generally referred to Geoemyda). The Emydinae are almost entirely New‐World, with a single Old‐World genus, Emys. The genus Clemmys is emydine and entirely North American: the Old‐World species usually referred to Clemmys are batagurines and are here referredto two genera: Mauremys Gray for caspica, japonica and mutica [‐nigrieans of most authors most of the time], and Sacalia Grey for bealei. A reclassification of the genera of Batagurinae and Emydinae is presented: the classification is based mainly on skull characters. Annamemys and Pseudocadia are considered synonyms of Mauremys mutica.