Number Of Presacral Vertebrae Research Articles

Variability in vertebral numbers does not contribute to sexual size dimorphism, interspecific variability, or phenotypic plasticity in body size in geckos (Squamata: Gekkota: Paroedura).

Body size is a fundamental trait correlated with nearly every aspect of animal life. It is influenced by numerous genetic and non-genetic factors. Despite its central importance, proximate mechanisms of intra- and interspecific variability in body size are still not well understood even in such a largely studied group as reptiles. For our study, we concentrated on the gecko species Paroedura picta. We investigated whether differences in sexual size dimorphism and in final and asymptotic snout-vent length (induced by a range of incubation and rearing temperatures) are correlated with differences in the number of presacral vertebrae. Moreover, we tested whether changes in this number were associated with evolutionary changes in sexual size dimorphism and body size in the genus Paroedura. We found that the variation in the number of presacral vertebrae is very limited both intra- and interspecifically, ranging between 26 and 28 vertebrae with most individuals possessing the modal number of 27. We conclude that changes in the number of vertebrae do not contribute to developmental plasticity or evolutionary changes in body size nor, in contrast to some other squamate lineages, to sexual size dimorphism.

Proximate cause, anatomical correlates, and obstetrical implication of a supernumerary lumbar vertebra in humans.

Three issues are considered on variation in number of presacral vertebrae (PSV) in humans: (1) sexual difference in number of PSV, (2) inactivation of Hoxd-11 gene as etiology for a supernumerary lumbar vertebra, and (3) anatomical correlates of a supernumerary lumbar vertebra, including lumbar-sacral nearthrosis, and pelvic size. Sample was 407 skeletonized females and 1,318 males from United States; ages at death were 20 to 49 years. Two subsamples of males were used: (1) 98 with modal numbers of cervical, thoracic, lumbar, and sacral vertebrae (PSV = 24) and (2) 45 with a supernumerary lumbar vertebra but modal numbers for other vertebral segments (PSV = 25). Measurements were taken of ulna, second metacarpal, vertebrae, femur, and pelvis; presence of lumbar-sacral nearthrosis was observed. Although 90% of females and males have 24 PSV, females have higher frequency of 23 PSV and males have higher frequency of 25 PSV. Compared to males with 24 PSV, males with 25 PSV and supernumerary lumbar vertebra show (1) no difference in anatomies associated with inactivation of Hoxd-11, and (2) higher frequency of lumbar-sacral nearthrosis and smaller pelvic inlet circumference. Sexual difference in number of PSV may be due to tempo of somite formation and Hox gene activation. Hypothesis is not supported that a supernumerary lumbar vertebra is due to inactivation of Hoxd-11. The presence of a supernumerary lumbar vertebra is associated with small pelvic inlet circumference, which can be obstetrically disadvantageous.

Comparative skeletal osteology of three species of Scincid lizards (Genus: Ablepharus) from Turkey

Despite the abundance and diversity of lizards in the family Scincidae, descriptions of their cranial and postcranial osteologies are almost nonexistent. Here, we provide detailed descriptions of adult skeletal morphologies in three scincid species: Ablepharus kitaibelii, A. chernovi and A. budaki. The skeletal elements of these lizards are described on cleared and double-stained specimens. The general pattern of the cranial and postcranial skeletons in the three scincid species is characterized by the absence of the palatal teeth, presence of thirteen scleral ossicles in each eye, pattern of fore- hindlimb, and shape of the clavicle and interclavicle. Additionally, there are some remarkable variations regarding the number, size and position of the bones. These include the size and shape of the nasal, the degree of fusion or separation of the postfrontal and postorbital and the number of presacral vertebrae and marginal teeth.

The postcranial skeleton of the aquatic parareptile Mesosaurus tenuidens from the Gondwanan Permian

ABSTRACT The postcranial skeleton of Mesosaurus tenuidens, a reptile from the Lower Permian of eastern South America and southern Africa, is redescribed and illustrated in detail. The number of presacral vertebrae varies in M. tenuidens from 29 to a maximum of 33, which falls just short of the maximum (34–35 presacrals) known in its close relative Stereosternum tumidum. A cleithrum is reported for the first time in a mesosaur. The head of the interclavicle is triangular, rather than diamond-shaped as in other basal reptiles, including S. tumidum. The carpus of M. tenuidens is apomorphic in that the intermedium and the lateral centrale are coossified. The lateral centrale pedis is absent. Reappraisal of the aquatic adaptations of M. tenuidens suggests strongly that this reptile was fully dedicated to an aquatic lifestyle. Pervasive pachyostosis of the postcrania probably allowed animals to maintain neutral buoyancy in the uppermost 3–4 m of the water column. Additionally, such pachyostosis may have helped to control rolling at the surface, or perhaps served to maintain forward momentum during periods of gliding while moving underwater. Limited movement at the elbow and the ankle suggests that M. tenuidens could not walk on land, but individuals may have been able to push themselves across terrestrial substrates, perhaps in a manner analogous to that seen in female extant marine turtles on nesting beaches.

A new species of Xinpusaurus (Thalattosauria) from the Upper Triassic of China

ABSTRACT A new species of Xinpusaurus Yin in Yin et al., 2000 (Thalattosauria, Thalattosauridae), is described from the Wayao Member of the Falang Formation (Tuvalian, Carnian, Upper Triassic) of Guanling County in Guizhou, southwestern China. It is the third thalattosaur species known from the Guanling faunal assemblage of marine reptiles. The type and only specimen consists of an entire skeleton, including a complete skull. It differs from the type species, X. suni, by its smaller adult size, the larger nasal, the more slender angular and low retroarticular process, the shape of the cervical neural spines, the number of presacral vertebrae, the large size of the scapula, the shape of the radius, the presence of a well ossified carpus, the more slender femur, the smaller hindfin, the presence of a complete row of distal tarsal ossifications, and the proportions of the metatarsals. It is consequently referred to a new species, Xinpusaurus kohi. A new analysis of thalattosaur interrelationships based on 30 cranial and postcranial characters corroborates a sister-group relationship between Xinpusaurus and Nectosaurus from the Carnian of California.

Axial skeletal and Hox expression domain alterations induced by retinoic acid, valproic acid, and bromoxynil during murine development.

Retinoic acid (RA) alters the developmental fate of the axial skeletal anlagen. "Anteriorizations" or "posteriorizations," the assumption of characteristics of embryonic areas normally anterior or posterior to the affected tissues, are correlated with altered embryonal expression domains of Hox genes after in utero RA treatment. These "homeotic" changes have been hypothesized to result from alterations of a "Hox cod" which imparts positional identity in the axial skeleton. To investigate whether such developmental alterations were specific to RA, or were a more general response to xenobiotic exposure, CD-1 pregnant mice were exposed to RA, valproic acid (VA), or bromoxynil (Br) during organogenesis. Additionally, the expression domains of two Hox genes, Hoxa7 and Hoxa10, were examined in gestation day (GD) 12.5 embryos obtained from control, RA, VA, or Br, treated gravid dams exposed on GD 6, 7, or 8. The anterior expression boundary of Hoxa7 is at the level of the C7/T1 vertebrae and that of Hoxa10 is at L6/S1. Compound-induced changes in the incidence of skeletal variants were observed. These included supernumerary cervical ribs (CSNR) lateral to C7, 8 vertebrosternal ribs, supernumerary lumbar ribs (LSNR) lateral to L1, extra presacral vertebrae, and the induction of vertebral and/or rib malformations. RA and VA administration on GD 6 caused posteriorization in the cervico-thoracic region (CSNR) while GD 8 exposure to any of the three compounds resulted in anteriorizations in the thoraco-lumbar area (LSNR and an increase in the number of presacral vertebrae). These effects occurred across regions of the axial skeleton. Analysis of gene expression demonstrated changes in the anterior boundaries of Hoxa7 expression domains in embryos treated on GD 6 and 8 with RA. VA and Br did not induce any statistically significant alterations in Hoxa7 and none of the compounds caused alterations in Hoxa10 expression domains. The studies indicate that RA GD 6 treatment-induced Hoxa7 shifts were rostral (posteriorization) while the RA-induced GD 8 anterior expression boundary shift was caudal (anteriorization), correlating with the axial skeletal changes noted. These data suggest that xenobiotic compounds such as VA and Br may induce similar axial skeletal changes by affecting different components of the developmental processes involved in the patterning of the axial skeleton.

Aspects of the morphology and reproductive biology of the Australian Earless Dragon LizardTympanocryptis tetraporophora

In the small Australian dragon (agamid) lizard Tympanocryptis tetraporophora mean snout-vent length (SVL) does not differ significantly between the sexes within the species as a whole. However, in a large sample from Sturt National Park, in northwestern New South Wales, males are larger than females both in snout-vent length and in mass. Large specimens are notably lacking from collections made during the coolest time of year.The number of premaxillary teeth is not correlated with head size. However, the number of acrodont teeth on the maxilla and dentary increases with head size.The modal number of presacral vertebrae is 23. There is no sexual dimorphism in either the number of postsacral vertebrae or the number of postsacral vertebrae with transverse processes. Hyperphalangy occurs in 3.2% of specimens. Gross variation in the sacral vertebrae occurs in 5.3% of specimens.For allometric analysis, two samples were considered: specimens from Stud National Park and all other specimens. Head length and hind l...

Observations on Limb Reduction in the Scincid Lizard Genus Chalcides

The relationships between several mensural and morphological variables are examined in the limb-reduced lineage of scincid lizards, Chalcides. There is a close linear relationship between the relative length of the body and the relative length of the head, the number of phalanges in the manus and in the pes, the relative length of the front and of the rear limb, and the relative length of the body and the number of presacral vertebrae. There is apparently only a loose association between snout-vent length and the number of presacral vertebrae and the number of pre- and postsacral vertebrae. There is a strongly inflected relationship between the number of phalanges and the relative length of the limb, the total number of phalanges, and both the number of presacral vertebrae and the relative length of the body, and the number of sternal + mesosternal ribs and both the relative length of the front limb and the number of parasternal chevrons. The inflected relationships may indicate a shift in emphasis from limbed locomotion to trunk locomotion (lateral undulation). However this supposition can only be tested when more is known of the ecology and behavior of the genus.

Miniaturization and Elongation in Eumeces (Sauria: Scincidae)

Relationships among size, number of presacral vertebrae, morphology and life history in members of the Pariocela section of the genus Eumeces were investigated. Presacral vertebral counts range from 26 in the largest, most stout-bodied species to 33 in the smallest, most elongate species. Female abdominal growth is positively allometric in all species, but strength of allometry is inversely correlated with size. Small, elongate Mexican montane species achieve a level of morphological development typical of subadults of larger forms, and reach sexual maturity in less time. They are thus progenetic (larger, slower maturing forms showing the primitive condition), and small size is proposed to be an adaptation to the short montane growing season. Abdominal elongation is interpreted as a means of maintaining a minimum critical clutch size, given a functionally constrained minimum neonate size and physical limitations on abdominal volume in a juvenile-sized adult.

The pachypleurosaurids (Reptilia: Nothosauria) from the middle triassic of Monte San Giorgio (Switzerland) with the description of a new species.

The largest and most diverse collection of Pachypleurosauridae (Nothosauria, Reptilia) comes from Monte San Giorgio, Switzerland. Several hundred complete skeletons were collected from four distinct horizons of bituminous limestones and shales of Anisian-Ladinian boundary to early Ladinian age (Middle Triassic). Serpianosaurus mirigiolensis comes from the oldest strata, the Grenzbitumenzone Beds. The three younger strata, all in the Lower Meride Limestone, yield three species of Neusticosaurus. Neusticosaurus pusillus comes from the Cava Inferiore horizon, Neusticosaurus peyeri, new species, from the Cava Superiore horizon, and Neusticosaurus edwardsii, new combination, from the Alla Cascina horizon. Neusticosaurus pusillus is biostratigraphically important because it is one of the rare species reported from both the Germanic and the Alpine Triassic. Neusticosaurus pusillus and N. peyeri are small and very similar in their anatomy. Neusticosaurus species are easiest separated by their number of presacral vertebrae. Ornamentation of the bone surface is distinctive for all four pachypleurosaurids. Soft parts are rarely preserved, except for one partial squamation. The biological age of Neusticosaurus individuals can be determined by skeletochronology (aging by bone annuli). Small species of Neusticosaurus were sexually mature after three to four years and lived for six to nine years. Taphonomic analysis of the small species indicates attritional mortality and suggests weak bottom currents in the Monte San Giorgio basin during early Ladinian times. Morphometric comparison of all four pachypleurosaurids indicates that the changing vertebral numbers between species are largely due to a change in number of segments. All Monte San Giorgio pachypleurosaurids are sexually dimorphic in forelimb development. Sex x has poorly differentiated and relatively short humeri whereas sex y has well differentiated and relatively long humeri. The sexes are of about the same size and represented in roughly equal numbers. Identification of gender was not possible. Good growth series, especially of Neusticosaurus peyeri, from embryo to large adult permitted qualitative and quantitative study of ontogeny. The skull grows with negative allometry; the humerus grows isometrically or with positive allometry, depending on sex and species; the femur grows isometrically. The adult size range in N. peyeri is considerably larger than in modern reptiles. The Monte San Giorgio pachypleurosaurids are a monophyletic group. The phylogeny of this group is congruent with the stratigraphic distribution of its members.

Limb Reduction in the Lizard Genus Lerista. 1. Variation in the Number of Phalanges and Presacral Vertebrae

The sandswimming, Australian scincid lizard genus Lerista is the best example of limb reduction in tetrapods in that it comprises an extensive and finely graded morphocline within a group of 51 closely related species. This paper analyzes variation in the number of phalanges and presacral vertebrae within populations and among species. Within populations, phalangeal number varies little and variation is usually symmetrical within individuals. The number of presacral vertebrae is sexually dimorphic, with females averaging 0.4-2.0 more than males. Among species there is a strong, curvilinear, inverse relationship between the number of phalanges and the number of presacral vertebrae. The interspecific morphoclines of phalangeal complements based on the total number of phalanges show that digits in both the manus and pes are lost in the order 1 > 5 > 2 > 3 > 4. Such morphoclines are perfectly linear except at one point in the pes where the series branches to accommodate two mutually exclusive configurations. If these morphoclines represent phylogenetic reductions and if phylogenetic reductions are hypothesized to be globally arrested stages of a basic developmental pattern, then one of these pes configurations must constitute an exception to this generalization. At least one other observed configuration is also likely to be outside a basic, global ontogenetic sequence for the genus.

Osteology and Anuran Systematics: Intrapopulational Variation in Hyla Lanciformis

Trueb, L. (Museum of Natural History and Department of Systematics and Ecology, The University of Kansas, Lawrence, Kansas 66045) 1977. Osteology and anuran systematics: Intrapopulational variation in Hyla lanciformis. Syst. Zool. 26:165-184.-Although osteological features are utilized frequently in comprehensive systematic reviews of anuran taxa, no serious attempt has been made to quantify the data and assess its variation other than in a descriptive context. Such assessments first must be made at the population level; thus, 119 osteological were madeon a of adult males and females of the Neotropical frog Hyla lanciformis (Anura: Hylidae). The results of this study show that nearly 50% of these characters demonstrate relatively low levels of variation in both sexes within the population. This suggests that osteological features can be quantified, and selected characters can be utilized to generate an osteological profile of a taxon to be used in concert with other numerical data for subsequent analyses. [Osteology; intrapopulational variation; Anura; Hyla lanciformis.] To a great extent the history of anuran classification -represents a chronology of investigations of anuran osteology. In the earliest classification of anurans (Wagler, 1830; Dumeril and Bibron, 1841), frogs were divided into two groups depending upon the presence (Phaneroglossa) or absence (Aglossa) of a tongue. The utility of the latter classification and others which followed (e.g. Thomas, 1854; Bruch, 1863; L'Isle, 1877) based on pupil shape and amplectic type were not accepted widely once Cope (1864, 1865) defined arcifery and firmisterny and designated two primary anuran groups on the basis of apparent dichotomous pectoral girdle structure. Boulenger (1882) perpetuated Cope's designations by describing series (Arcifera and Firmisternia) within the order Anura. This classification prevailed until Noble (1922) established five suborders of anurans predicated on differences in thigh musculature and, principally, the structure of vertebral centra. Noble's conclusions largely stood unchallenged until recent reassessments by Griffiths (1963), Inger (1967), Kluge and Farris (1969), Starrett (1973), Sokol (1975), and Duellman (1975). A glance at more recent work at familial and generic levels (e.g. see Zweifel, 1956, on pelobatids; Lynch, 1971, on leptodactylids; Tihen, 1962, on bufonids; Duelhman, 1970, on hylids; Trueb, 1970, on hylids; Laurent, 1940, 1941 a and b, 1943, and 1944, on ranids and rhacophorids; Parker, 1934, on microhylids) demonstrates the pervasiveness of osteological criteria in studies of anuran relationships. Scarcely a species description exists which does not specify snout-vent length. Moreover, morphometric assessments of head width, and hind limb length are presented, usually, as a matter of procedure and frequently are expressed as proportions of the snout-vent length. Among other characters commonly encountered are the shape of the snout, various cranial features (e.g. condition of dermal bone and presence or absence of cranial elements and dentition), fusion of limb bones, development of prehallux and prepollex, and number of presacral vertebrae. It is patently obvious that these characters are osteological as are the standard measurements of head, body and limb dimensions. Another issue of paramount importance in understanding the relationships among modem anurans is the fossil record, the interpretation of which is contingent almost exclusively on osteological criteria. All too

Variation in the number of presacral vertebrae in Bantu-speaking South African Negroes.

AbstractVariation in number of presacral vertebrae (PSV) was examined in 462 vertebral columns in four populations drawn from tribal groups of Southern African Negroes. The total incidence of numerical variants (23 PSV and 25 PSV) was 19% in males and 12.1% in females. Males have a higher frequency of 25 PSV and females a higher frequency of 23 PSV, a sex difference reported by previous workers. Significant differences in the incidence of 25 PSV in males were present between S.A. Negroes, American Negroes and other racial groups. The total number of variants (23 PSV and 25 PSV) is significantly higher in S.A. Negro males (and higher but not significantly in females) than in the other groups; owing mainly to the findings in the Nguni‐speaking sub‐samples of the S.A. Negro. These findings support a previous suggestion based on combined‐sex data that the frequency of numerical variations of PSV are characteristic of a population. It is suggested here that such frequencies are even more characteristic when males and females are considered separately.

Numerical variation of the presacral vertebral column in three population groups in North America.

AbstractA total of 1,239 skeletons from among Mongoloid, Caucasoid and Negroid population groups in North America was examined for variations in the number of presacral vertebrae. The overall incidence of variation was 11%; 6% with 23 and 5% with 25 presacral vertebrae. Differences in total variation among the three groups were not significant, but differences in the incidence of 23 and 25 presacral vertebrae among the groups were highly significant. Numerical vertebral variation occurred in 11% of both sexes, but with males having a higher frequency of 25 presacral vertebrae and females having a higher frequency of 23 presacral vertebrae. The incidence of the specific variation of 23 or 25 presacral vertebrae was not significantly different among the males of the three groups studied, whereas 23 presacral vertebrae were found significantly more often in the Negroid females. Numerical variation of vertebrae was not associated with age. The data strongly support the conclusion that the total frequency of variation in the number of presacral vertebrae is a specific characteristic of any particular population group and that there is a tendency in all population groups toward an increase in number in males and a decrease in number in females.

The phylogeny of the salientia.

Summary1. The essentially recent skeletal patterns of fossil Salientia indicates that the evolutionary relationships of the order must continue to be assessed on evidence obtained chiefly from a study of recent forms.2. The morphology and morphogenesis of the more important criteria employed in taxonomic analyses are described. Definitive and developmental features of pectoral and vertebral elements are particularly detailed. It is concluded that: (a) neither the nature of the vertebral articulation nor the arrangement of the thigh complex is a reliable character on which to define major salientian categories; and (b) criteria based on degree of freedom of epicoracoid cartilages are incapable of exact taxonomic application. The Arcifera and Firmisternia are redefined according to the presence or absence of epicoracoid horns. The importance of certain morphogenetic patterns in the analysis of phylogenetic trends is suggested.3. A new scheme is proposed for the definition of recent salientian families. This hinges chiefly on the number of presacral vertebrae, the nature of the definitive centrum and the epicoraco‐sternal complex.4. The status of Protobatrachus (L. Trias) is reviewed. It is concluded that the proanuran stock stemmed from temnospondylid ancestors and that the so‐called ‘saltatory’ trends of modern Salientia evolved primarily for swimming. Fossil footprints from the Ecce formation of South Africa may indicate that the Proanura were already established by the Permian. The role of the urostyle in facilitating the pro‐anuran‐salinetian transition is considered.5. On the evidence of the vertebral column it is suggested that the Salientia are at least diphyletic and that all non‐ascaphid forms stemmed from a pipoid stock. Interrelationships between the non‐ascaphid families are considered.6. The geographic history of the order is reviewed. It is concluded that early salientian evolution was rapid and radiative and that, skeletally at least, the essential features of all the recent families had been established by the Tertiary or, possibly, by the Mesozoic. Discoglossidae, Pipidae and Pelobatidae are interpreted as eco‐1 ogically isolated and the Atelopodidae as Neotropical in both origin and range. Whilst the main ranoid and bufonid stocks almost certainly originated in and radiated from the Old World tropics (as Darlington suggested) some of their derived lines (Rhaco‐phoridae and Microhylidae in particular) may equally well have evolved polycentrically without much subsequent radiation.7. It is suggested that radiation or isolation, in the different families, is a function of locomotory specializations and that these are reflected particularly in the variations of the vertebral centrum and the shoulder girdle.I wish to thank Miss A. G. C. Grandison, Professor Georg Haas, Professor J. P. Lehman, Dr H. W. Parker, the late Dr Malcolm Smith and Dr L. C. Stuart who have assisted me either with helpful discussions and information or with gifts of material. I am also indebted to Dr A. W. Crompton for photographs of the fossil footprints from the Ecce formation.

RIB AND VERTEBRAL NUMBERS IN SWINE.: I. VARIATION OBSERVED IN A LARGE POPULATION

In a population of 10,683 pigs of two breeds and their crosses the number of rib pairs ranged from 13.5 to 17.0 and the number of pre-sacral vertebrae (excluding cervical) from 20 to 23. The breeds and crosses studied overlapped completely in range of variability but differed in relative frequency of the various rib and vertical classes. The average regression or rib number on vertebral number ranged from.62 for Lacombe females to.77 for Yorkshire females. Bilateral asymmety in rib number was observed in 6.5 per cent of all pigs and 41 per cent of the 1,147 litters, examined contained asymmetrical pigs. Within-litter variation in rib and vertebral number (thoracic and lumbar) was frequent with a maximum observed range of 2.5 ribs and 3 vertebrae. Complete uniformity of littermates in rib number, in vertebral number, and in both traits was observed in 23, 31 and 13 per cent respectively of all litters. Males and females were essentially identical in average rib and vertebral number and in frequency of asymmetry. Variation in these skeletal traits was not associated with viability.

Hereditary absence of spleen in the mouse.

THE ‘luxoid’ mutants of the house-mouse form a small and well-defined group with striking limb-defects. In luxate1 (lx) and luxoid2 (lu) homozygotes hind-legs are often twisted, due to reduction or loss of the tibia and distortion of the fibula with associated muscular abnormalities. The femur may also be shortened and fragmented and even the pubic element of the pelvic girdle may be affected in luxates. The hind-feet may show pre-axial poly- or oligo-dactylism, the fore-feet may also be polydactylous in lu lu mice. Heterozygotes may appear normal or may have pre-axial triphalangy or polydactyly of the hind-feet. There are various other skeletal effects (on the number of presacral vertebrae, etc.) while the urogenital system is also involved in luxate homozygotes, with frequent hydronephrosis and hydroureter.

Contributions to the Osteology of the Post-Cranial Skeleton of the Amphisbaenidae

The post-cranial skeleton, unlike the skull of the Amphisbaenidae (Zangerl, 1944), does not exhibit as many characters peculiar to this group of reptiles. In some respects there are similarities with the post-cranial skeleton of the snakes, (e.g., the large number of presacral vertebrae; distally forked ribs in the sacral region; no haemapophyses, but paired ventral processes in the tail region, analogous to haemapophyses), in other respects with that of the lizards (e.g., the structure of the vertebrae lacking zygosphen-zyganthrum connection; the presence of a shoulder girdle and front limbs in the genus Bipes, with a lacertiloid carpus, but a strange phalangeal formula of 3, 3, 3, 3, 3; vestigesl of a shoulder girdle in Blanus cinereus, and other forms). Furthermore there are similarities which the amphisbaenids have in common with the snakes and the limbless forms among the lizards (e.g., lymphapophyses in the sacral region). Practically all of these characters are clearly adaptive and do not suggest a close relationship to either the lizards or the snakes. Scattered information concerning the post-cranial skeleton of the Amphisbaenidae can be found in the literature. Most descriptions and illustrations concern girdle and limb vestiges (Joh. Miuller, 1832; Dumeril and Bibron, 1839, 1854; Gervais, 1853; Fiirbringer, 1870, 1900; Smalian, 1885; Cope, 1892a; K. H. M. Muller, 1900) and need to be revised and expanded.

The Ancestry of the Caudate Amphibia

The Stegoeephala will probably have to be divided into two groups, one of which will be considered as Amphibia and the members of the other group will have to be placed among the Reptilia but eau not all be placed under any single head since they represent divergent types and must be placed in with the reptilian groups to which they have probably given origin. 2. The Branchiosauria are the ancestral forms of at least the caudate Amphibia. The Branchiosauria are first known in the Pennsylvanian of North America and they present characters which separate them clearly from all other groups of the so-called Stegocephala. 3. The characters which the Branchiosauria have in common with the Caudata are: short, straight ribs; stout transverse processes springing from the body of the vertebra; practically the same number of presacral vertebrae; the same skull structure; the degenerate character of the pectoral girdle and the close correspondence of the pelvic girdle; the same number of the digits and the same phala...