搜索结果：crocodile

The population biology of the American crocodile (Crocodylus acutus) was studied in southern Florida during 1977-1982. Crocodiles occur primarily in inland mangrove swamps protected from wave action. Females use the open waters of Florida Bay only for access to nesting sites. Individuals have large (86-262 ha), overlapping activity areas. Nesting occurs in spring and summer, avoiding the cold and the wet seasons, either of which can affect incubation. Clutches averaging 38 eggs were laid both in mounds and in holes in the ground, either singly or communally. Available data cannot support the view that the number of nests has decreased in recent years. Hatching failure occurred as a result of infertility, predation, and embryonic mortality from desiccation and flooding. Hole and creek nests were most susceptible to embryonic mortality. Seventy-eight percent of nests hatched some young. We found no evidence of adults defending nests or young, but nest opening by adults was essential for hatching. Disturbance at nest sites caused females to abandon the site. All expected age classes occurred in the population. Size at maturity was 2.25 m TL for females. Documented mortality of adults and subadults of approximately 2 crocodiles per year was predominantly human-caused. At least 45 crocodiles have been released into southern Florida in 17 years. We estimate the southern Florida population to be about 220 ? 78 adults and subadults. The northernmost population of the American crocodile (Crocodylus acutus) occurs on the extreme southern tip of the Florida peninsula, USA. The range of this tropical species has always been limited, probably by temperature constraints (Kushlan and Mazzotti, 1989). Early reports of crocodiles in Florida are notices and discussions of its occurrence (Wyman, 1870; Hornaday, 1891; Smith, 1896; Barbour, 1923); Moore (1953) provided the first detailed account of its status. Ogden (1978) documented aspects of its nesting biology. More recently, Gaby et al. (1985) reported on the population biology of a small number of crocodiles living in a power plant cooling system. 3 Present Address: Department of Wildlife and Range Sciences, University of Florida, 3245 College Avenue, Davie, Florida 33314, USA. st population of the Ameriil ( ocodylus acutus) oc urs on the e tip of the Florida peninsula, e of this tropical species has alli ite , probably by temperature ( s la and az ot i, 1989). Early iles in Florida are notices and its occurrence ( yman, 1870; ; S ith, 1896; Barbour, 1923); ) ided the first detailed ac ount . e (1978) documented aspects i iolog . ore recently, Gaby et te on the population biology er of crocodiles living in a powli s ste . ess: epart ent of Wildlife and s, iversity of Florida, 3245 College Many crocodilian populations are endang red because their effective population sizes h ve been reduced by human-related factors such as as hunting and habitat loss. Small poplations, particularly when isolated, risk extirpation because of the action of natural or artificial forces that erode their numbers. The Florida population of the American crocodile is thought to be of limited size (Ogden, 1978), and therefore susceptible to chance and human inerference. As a result it has long been considred to be endangered (Barbour, 1923; Hines et al., 1984). Unfortunately, limited information has inhibited understanding of its population biology, and therefore of its true status or appropriate conservation needs. In this paper we discuss the population biology of the the American crocodile based on a five-year study of the population in the core of its northernmost range, northeastern Florida crocodilian populations are endanbecause their e fective opulation sizes een reduced by human-related factors as as hunting and habi at loss. Small popi s, particularly when isolated, risk extiri because of the action of natural o arti7 This content downloaded from 157.55.39.162 on Thu, 11 Aug 2016 05:12:47 UTC All use subject to http://about.jstor.org/terms J. A. KUSHLAN AND F. J. MAZZOTTI Bay. Where appropriate, we compare information from studies conducted simultaneously and cooperatively with our own on other segments of the population (Gaby et al., 1975; P. Moler, pers. comm.). Other aspects of our overall study program are discussed elsewhere (Behler, 1978; Hall et al., 1979; Dunson, 1982; Lutz and Dunbar-Cooper, 1984; Stoneburner and Kushlan, 1984; Kushlan, 1988; Mazzotti et al., 1988; Kushlan and Mazzotti, 1989).

The Nile crocodile (Crocodylus niloticus) is an ancient icon of both cultural and scientific interest. The species is emblematic of the great civilizations of the Nile River valley and serves as a model for international wildlife conservation. Despite its familiarity, a centuries-long dispute over the taxonomic status of the Nile crocodile remains unresolved. This dispute not only confounds our understanding of the origins and biogeography of the 'true crocodiles' of the crown genus Crocodylus, but also complicates conservation and management of this commercially valuable species. We have taken a total evidence approach involving phylogenetic analysis of mitochondrial and nuclear markers, as well as karyotype analysis of chromosome number and structure, to assess the monophyletic status of the Nile crocodile. Samples were collected from throughout Africa, covering all major bioregions. We also utilized specimens from museum collections, including mummified crocodiles from the ancient Egyptian temples at Thebes and the Grottes de Samoun, to reconstruct the genetic profiles of extirpated populations. Our analyses reveal a cryptic evolutionary lineage within the Nile crocodile that elucidates the biogeographic history of the genus and clarifies long-standing arguments over the species' taxonomic identity and conservation status. An examination of crocodile mummy haplotypes indicates that the cryptic lineage corresponds to an earlier description of C. suchus and suggests that both African Crocodylus lineages historically inhabited the Nile River. Recent survey efforts indicate that C. suchus is declining or extirpated throughout much of its distribution. Without proper recognition of this cryptic species, current sustainable use-based management policies for the Nile crocodile may do more harm than good.

Captivity is an important measure for conservation of an endangered species and it is becoming a hot topic in conservation biology, which integrates gut microbiota and endangered species management in captivity. As an ancient reptile, the crocodile lizard (Shinisaurus crocodilurus) is facing extreme danger of extinction, resulting in great significance to species conservation in the reserve. Thus, it is critical to understand the differences in gut microbiota composition between captive and wild populations, as it could provide fundamental information for conservative management of crocodile lizards. Here, faecal samples of crocodile lizards were collected from two wild and one captive populations with different ages (i.e. juveniles and adults), and were analyzed for microbiota composition by 16S rRNA gene amplicon sequencing. This study showed that the lizard gut microbiota was mainly composed of Firmicutes and Proteobacteria. The gut microbiota composition of crocodile lizard did not differ between juveniles and adults, as well as between two wild populations. Interestingly, captivity increased community richness and influenced community structures of gut microbiota in crocodile lizards, compared with wild congeners. This was indicated by higher abundances of the genera Epulopiscium and Glutamicibacter. These increases might be induced by complex integration of simple food resources or human contact in captivity. The gut microbiota functions of crocodile lizards are primarily enriched in metabolism, environmental information processing, genetic information processing, and cellular processes based on the KEGG database. This study provides fundamental information about the gut microbiota of crocodile lizards in wild and captive populations. In the future, exploring the relationship among diet, gut microbiota, and host health is necessary for providing animal conservation strategies.

Empirical field data describing daily and seasonal cycles in body temperature (Tb) of free-ranging Crocodylus porosus (32-1010 kg) can be predicted by a mathematical analysis. The analysis provides a mechanistic explanation for the decreased amplitude of daily cycles in Tb and the increase in 'average' Tb with increasing mass. Assessments of 'average' daily Tb were made by dividing the integral of the difference between measured values of Tb and minimum operative temperature by the period of integration, to yield a thermal index expressing relative 'warmth' of crocodiles. The average daily Tb of a 1010 kg crocodile was 3.7 degreesC warmer than that of a 42 kg individual in summer and 1.9 degreesC warmer than that of a 32 kg individual in winter. The success of this mathematical approach confirms that crocodiles are simple ectotherms and that there is unlikely to be a significant contribution to their thermal biology from physiological mechanisms. Behaviour, however, is very important even in large individuals. Crocodiles in the field typically move daily between land and water in cycles that vary seasonally. We predicted Tb for the reverse of these behavioural cycles, which more than doubled seasonal fluctuations in Tb compared with the observed fluctuations. We were also able to predict the Tb of very large, dinosaur-sized crocodiles in a similar climate to that at our study site. A 10 000 kg 'crocodile', for example, would be expected to have a Tb of 31 degreesC in winter, varying by less than 0.1 degreesC during a day when operative temperatures varied by nearly 20 degreesC, from 20 to 38 degreesC. The study confirms that, in low latitudes at least, large dinosaurs must have had an essentially high and stable value of Tb, without any need for endothermy. Also, access to shade or water must have been crucial for the survival of large dinosaurs at low latitudes. Furthermore, the finding of increasing 'average' Tb as ectotherms grow larger may have implications for the metabolic rates of very large reptiles, because the Q10 effect could counteract the downscaling of metabolic rate with mass, an effect that seems not to have been recognised previously.

The crocodile lizard is a critically endangered reptile, and serious diseases have been found in this species in recent years, especially in captive lizards. Whether these diseases are caused by changes in the gut microbiota and the effect of captivity on disease remain to be determined. Here, we examined the relationship between the gut microbiota and diet and disease by comparing the fecal microbiota of wild lizards with those of sick and healthy lizards in captivity. The gut microbiota in wild crocodile lizards was consistently dominated by Proteobacteria (~56.4%) and Bacteroidetes (~19.1%). However, the abundance of Firmicutes (~2.6%) in the intestine of the wild crocodile lizards was distinctly lower than that in other vertebrates. In addition, the wild samples from Guangdong Luokeng Shinisaurus crocodilurus National Nature Reserve also had a high abundance of Deinococcus-Thermus while the wild samples from Guangxi Daguishan Crocodile Lizard National Nature Reserve had a high abundance of Tenericutes. The gut microbial community in loach-fed crocodile lizards was significant different from the gut microbial community in the earthworm-fed and wild lizards. In addition, significant differences in specific bacteria were detected among groups. Notably, in the gut microbiota, the captive lizards fed earthworms resulted in enrichment of Fusobacterium, and the captive lizards fed loaches had higher abundances of Elizabethkingia, Halomonas, Morganella and Salmonella, all of which are pathogens or opportunistic pathogens in human or other animals. However, there is no sufficient evidence that the gut microbiota contributes to either disease A or disease B. These results provide a reference for the conservation of endangered crocodile lizards and the first insight into the relationship between disease and the gut microbiota in lizards.

Summary 1. Lake Rudolf, nothern Kenya, has one of the largest undisturbed populations of the Nile Crocodile. In 1965 the Kenya Game Department initiated the Lake Rudolf Crocodile Research Project. Central Island, where the crocodiles live under undisturbed conditions, was chosen for studying breeding behaviour and ecology of the reptile. Eight months were spent on the island. 2. On the island most of the crocodile population was confined to a crater lake, Lake C, which supported up to 500 animate at the height of the 1965‐66 breeding season. 3. The 1200 m shoreline of Lake C was shared out between about a dozen large males each guarding his territory by patrolling up and down the shore. The territorial shore lengths ranged from 60 to 230 m. The territories extended about 50 m into the water. 4. The crocodiles were first seen courting on 10.10.65 in Lake C. The territorial males exhibited a “courtship splash display”. Copulation ranged from 30 to 100 seconds; eleven copulations averaged 58 seconds. 5. The factors important in site selection for nesting are shade, suitable soil, proximity to water and the degree of slope of the shore. Because the shores of a second crater lake, Lake A, satisfied these conditions they had the largest number of nests. The fully exposed sites on Lake C, and the Lake Rudolf shores, had very few nests. 6. The females dig the nests with their forelimbs, using them in turn. The hind limbs and the belly are used to push away the soil collecting at the mouth of the burrow. The female guards the nest constantly throughout the incubation period of three months against monitor luzards. Laying began in the third week of November, 1965 reaching its peak during the second week of December. The crocodile egg is oblong, measuring 55.5 to 89.0 mm in length and 43.0 to 54.0 mm in width. Mean weights of the eggs from 15 clutches ranged from 83.7 to 126.6 g. Clutch sizes on Central Island varied from 14 to 46 eggs, giving a mean of 33 eggs per clutch. When the young are about to hatch, the mother releases them by digging up the nest. The young when they hatch are about 31.0 cm long and weigh about 76.8 g. They are guarded by the mother for at least six weeks. Infant mortality is probably very considerable.

The genomes of warm-blooded vertebrates are characterized by a strong heterogeneity in base composition, with GC-rich and GC-poor isochores. The GC content of sequences, especially in third codon positions, is highly correlated with that of the isochore they are embedded in. In amphibian and fish genomes, GC-rich isochores are nearly absent. Thus, it has been proposed that the GC increase in a part of mammalian and avian genomes represents an adaptation to homeothermy. To test this selective hypothesis, we sequenced marker protein genes in two cold-blooded vertebrates, the Nile crocodile Crocodylus niloticus (10 genes) and the red-eared slider Trachemys scripta elegans (6 genes). The analysis of base composition in third codon position of this original data set shows that the Nile crocodile and the turtle also exhibit GC-rich isochores, which rules out the homeothermy hypothesis. Instead, we propose that the GC increase results from a mutational bias that took place earlier than the adaptation to homeothermy in birds and before the turtle/crocodile divergence. Surprisingly, the isochore structure appears very similar between the red-eared slider and the Nile crocodile than between the chicken and the Nile crocodile. This point questions the phylogenetic position of turtles as a basal lineage of extant reptiles. We also observed a regular molecular clock in the Archosauria, which enables us, by using a more extended data set, to confirm Kumar and Hedges's dating of the bird-crocodile split.

<title>Abstract</title> This book was written for veterinarians, scientists, wildlife officials, students and crocodile farmers. The gathered data was based on years of work with farmed Nile crocodiles, some with wild and wild-caught African dwarf crocodiles in the Congo Republic, as well as on information from available literature. This book is a comprehensive reference on the biology, management and health of crocodiles, alligators and gharials. Emphasis is on diagnosis, treatment, and prevention of diseases as these occur on crocodile farms; clinical aspects of disease are also discussed. Photographs depicting various cases and conditions have been compiled. Anatomy, physiology, biochemistry, behaviour, nutrition, rearing, breeding, slaughter and welfare are also covered.

The threat of coronavirus disease 2019 to health systems in sub-Saharan Africa (SSA) can be compared metaphorically to a lake in Africa infested with a bask of crocodiles and the saying "the eye of the crocodile." In the lake, only the eyes of the crocodile appear on the surface while the rest of the body is submerged in water. In this Viewpoint, the eyes and the body of the crocodile represent the public health preparedness and health systems, respectively, in SSA. SSA has had multiple epidemics, including, in the last 3 decades, HIV and Ebola virus. Interestingly, HIV, Ebola virus, and SARS-CoV-2 are all of zoonotic origin. HIV resulted from cross-species transfer of simian immunodeficiency virus from chimpanzees, found in eastern and central Africa, to humans (1). Ebola virus was discovered in humans during concurrent outbreaks in the Democratic Republic of Congo and the Sudan in 1976 (2, 3). It is believed that bats are the natural hosts of Ebola virus. SARS-CoV-2 also originated from bats found in caves in China. Although HIV and Ebola originated in Africa, SARS-CoV-2 was imported from China. This Viewpoint discusses the potential impact of the COVID-19 epidemic on already-fragile health systems in SSA and forecasts lessons likely to be learned from COVID-19 in SSA.

These study reports the results derived from a pilot research study based on a phenomenographic research approach with 50 respondents in the Northern Territory of Australia. The data permitted a perceptual map to be drawn which identifies tourist fascination with crocodiles as being based on attributes of potential threat, danger, power, links with the prehistoric, and survivorship. However the study also found that when asked to describe the Northern Territory, crocodiles did not immediately come to mind, even though, arguably, the reptile is etched upon the ethos of the 'Top End'. However prompted responses quickly elicited mention of crocodiles. There was also a preference to see crocodiles within their natural terrain. Some evidence of a minority of tourists being prepared to mitigate their behaviours was also found, and hence this study may have wider implications.

SYNOPSIS, The movements of 100 crocodiles (0.3-4.3 m) were followed over 3 years by mark-recapture, spotlight survey and radiotelemetry at Ngezi, Zimbabwe. Home ranges were based on frequency of occurrence of animals in 100 m grid squares. Most crocodiles were nocturnal, but adults occasionally moved in daylight. Animals 0.4-2.2 m had home ranges of similar sizes, but dispersed at 1.2 m. Smaller crocodiles were restricted to the river (the only nesting area) whereas all larger animals occupied the lake into which the river flowed. From 2.2 m the range of movement increased until large subadult females (2.7 m) travelled widely without distinct home ranges. Subadults were still largely excluded from the river and the smallest nesting female migrated out of the river after each breeding season. Large breeding females (>2.8 m) had small home ranges near prime nest sites. There appeared to be no difference in the behavior of the sexes up to 2.2 m. There are few data on larger males, but four mature animals (>3.2 m) had distinct home ranges. Home ranges of small juveniles increased in size in the hot season, but for adults the effects of climate and breeding were confused. The different behavior of the various categories of crocodiles resulted in the marked separation of breeding females with their last few season's offspring from immature animals 1.2-2.2 m. Dispersal appears to occur at the same stage in other crocodilians with similar scaling parameters because adults become increasingly intolerant of intermediate-sized animals. It is suggested that size-class separation is part of a general density-dependent regulating mechanism in crocodilian populations.

BACKGROUND: The morphological peculiarities of turtles have, for a long time, impeded their accurate placement in the phylogeny of amniotes. Molecular data used to address this major evolutionary question have so far been limited to a handful of markers and/or taxa. These studies have supported conflicting topologies, positioning turtles as either the sister group to all other reptiles, to lepidosaurs (tuatara, lizards and snakes), to archosaurs (birds and crocodiles), or to crocodilians. Genome-scale data have been shown to be useful in resolving other debated phylogenies, but no such adequate dataset is yet available for amniotes. RESULTS: In this study, we used next-generation sequencing to obtain seven new transcriptomes from the blood, liver, or jaws of four turtles, a caiman, a lizard, and a lungfish. We used a phylogenomic dataset based on 248 nuclear genes (187,026 nucleotide sites) for 16 vertebrate taxa to resolve the origins of turtles. Maximum likelihood and Bayesian concatenation analyses and species tree approaches performed under the most realistic models of the nucleotide and amino acid substitution processes unambiguously support turtles as a sister group to birds and crocodiles. The use of more simplistic models of nucleotide substitution for both concatenation and species tree reconstruction methods leads to the artefactual grouping of turtles and crocodiles, most likely because of substitution saturation at third codon positions. Relaxed molecular clock methods estimate the divergence between turtles and archosaurs around 255 million years ago. The most recent common ancestor of living turtles, corresponding to the split between Pleurodira and Cryptodira, is estimated to have occurred around 157 million years ago, in the Upper Jurassic period. This is a more recent estimate than previously reported, and questions the interpretation of controversial Lower Jurassic fossils as being part of the extant turtles radiation. CONCLUSIONS: These results provide a phylogenetic framework and timescale with which to interpret the evolution of the peculiar morphological, developmental, and molecular features of turtles within the amniotes.

The complete mitochondrial genome of the alligator, Alligator mississippiensis, was sequenced. The size of the molecule is 16,642 nucleotides. Previously reported rearrangements of tRNAs in crocodile mitochondrial genomes were confirmed and, relative to mammals, no other deviations of gene order were observed. The analysis of protein-coding genes of the alligator showed an evolutionary rate that is roughly the same as in mammals. Thus, the evolutionary rate in the alligator is faster than that in birds as well as that in cold-blooded vertebrates. This contradicts hypotheses of constant body temperatures or high metabolic rate being correlated with elevated molecular evolutionary rates. It is commonly acknowledged that birds are the closest living relatives to crocodiles. Birds and crocodiles represent the only archosaurian survivors of the mass extinction at the Cretaceous/Tertiary boundary. On the basis of mitochondrial protein-coding genes, the Haemothermia hypothesis, which defines birds and mammals as sister groups and thus challenges the traditional view, could be rejected. Maximum-likelihood branch length data of amino acid sequences suggest that the divergence between the avian and crocodilian lineages took place at approximately equal to 254 MYA.

Crocodiles and ostriches are very sensitive to stress, and the ideal conditions for intensive rearing have not yet been established. Consequently, mortality is often directly linked to conditions on the farm. Crocodile and caiman pox, adenoviral hepatitis, mycoplasmosis, chlamydiosis and coccidiosis are crocodile-specific infections with reservoirs in wild populations and adult wild-caught breeding stock. Other important conditions are salmonellosis, non-specific septicaemia, trichinellosis, the nutritional diseases osteomalacia, fat necrosis and gout, as well as winter sores. The only ostrich-specific transmissible disease is libyostrongylosis. Other important conditions are Newcastle disease, avian influenza, fading chick syndrome, tibiotarsal rotation and enteritis. No cases of coccidiosis in ostriches have ever been confirmed.

Various lineages of amniotes display keratinized skin appendages (feathers, hairs, and scales) that differentiate in the embryo from genetically controlled developmental units whose spatial organization is patterned by reaction-diffusion mechanisms (RDMs). We show that, contrary to skin appendages in other amniotes (as well as body scales in crocodiles), face and jaws scales of crocodiles are random polygonal domains of highly keratinized skin, rather than genetically controlled elements, and emerge from a physical self-organizing stochastic process distinct from RDMs: cracking of the developing skin in a stress field. We suggest that the rapid growth of the crocodile embryonic facial and jaw skeleton, combined with the development of a very keratinized skin, generates the mechanical stress that causes cracking.

Zooarchaeologists have long relied on linear traces and pits found on the surfaces of ancient bones to infer ancient hominid behaviors such as slicing, chopping, and percussive actions during butchery of mammal carcasses. However, such claims about Plio-Pleistocene hominids rely mostly on very small assemblages of bony remains. Furthermore, recent experiments on trampling animals and biting crocodiles have shown each to be capable of producing mimics of such marks. This equifinality-the creation of similar products by different processes-makes deciphering early archaeological bone assemblages difficult. Bone modifications among Ethiopian Plio-Pleistocene hominid and faunal remains at Asa Issie, Maka, Hadar, and Bouri were reassessed in light of these findings. The results show that crocodiles were important modifiers of these bone assemblages. The relative roles of hominids, mammalian carnivores, and crocodiles in the formation of Oldowan zooarchaeological assemblages will only be accurately revealed by better bounding equifinality. Critical analysis within a consilience-based approach is identified as the pathway forward. More experimental studies and increased archaeological fieldwork aimed at generating adequate samples are now required.

True crocodiles (Crocodylus) are the most broadly distributed, ecologically diverse, and species-rich crocodylian genus, comprising about half of extant crocodylian diversity and exhibiting a circumtropical distribution. Crocodylus traditionally has been viewed as an ancient group of morphologically conserved species that originated in Africa prior to continental breakup. In this study, these long-held notions about the temporal and geographic origin of Crocodylus are tested using DNA sequence data of 10 loci from 76 individuals representing all 23 crocodylian species. I infer a time-calibrated species tree of all Crocodylia and estimate the spatial pattern of diversification within Crocodylus. For the first time, a fully resolved phylogenetic estimate of all Crocodylia is well-supported. The results overturn traditional views of the evolution of Crocodylus by demonstrating that the true crocodiles are not "living-fossils" that originated in Africa. Rather, Crocodylus originated from an ancestor in the tropics of the Late Miocene Indo-Pacific, and rapidly radiated and dispersed around the globe during a period marked by mass extinctions of fellow crocodylians. The findings also reveal more diversity within the genus than is recognized by current taxonomy.

Abstract The unique holotype of Hallopus victor (Marsh), from the Upper Jurassic of Garden Park, Colorado, is redescribed. The bones previously identified as pubes (Marsh 1890) or ischia (von Huene 1914) are regarded here as the left radius and ulna, and the ‘ ulna5 and ‘radius5 of previous workers are considered to be the left radiale and ulnare. Marsh’s identification (1890) of the ischium and his orientation of the scapula and femur (1896) are upheld. The presence of a humerus on the larger slab is confirmed. Hallopus is interpreted as a highly specialized, cursorial crocodilian, with slender, hollow bones, a greatly elongated radiale and ulnare, and a roller-like joint between these and the metacarpals. The manus is pentadactyl with a symmetrical distribution of lengths about the central axis and some proximal wedging-out of the metacarpals. The iliac blade is elongated and resembles that of Orthosuchus, the ischium is reminiscent of that of Protosuchus. The femur has a lesser trochanter, a fourth trochanter and a ‘pseudointernal' trochanter, but no greater trochanter. The tibia is longer than the femur. The tarsus is basically crocodilian in pattern, but greatly compressed and specialized. The first metatarsal is reduced to an elongated splint, permanently recessed into metatarsal II. Metatarsals II to IV are symmetrical in length with III longest, metatarsal V is reduced, pointed, and lacks phalanges. The interpretation put forward provides a consistent explanation of the peculiarities of the skeleton of Hallopus as a variant on the basic crocodilian plan. The details of the articulation of the carpal and tarsal joints are described as far as preservation permits, and possible movements are considered. The carpometacarpal and tarsal joints are simple hinges, but the proximal carpal joint appears to have been relatively immobile and the elongation of the radiale and ulnare is viewed as a device to compensate for the increase in length of the tibia. The femur has an off-set, ball-like head and evidently moved essentially in a parasagittal plane. The pes is functionally tridactyl, with the metatarsals locked together proximally. It is concluded that both fore- and hind-feet were digitigrade during movement, although in a stationary pose the metatarsus may have been in contact with the ground. Some aspects of the pelvic and hind-limb musculature are briefly discussed. Functional analogies from the locomotory point of view are limited by the lack of cursorial quadrupedal archosaurs for comparison. It is concluded that a hare-like bounding gallop was the most probable type of fast locomotion in Hallopus. Although no skull bones have been identified, evidence from the postcranial skeleton is adduced to show that Hallopus is of pedeticosaurid descent. The relationships of early crocodilomorphs are discussed, and it is deduced that two basic stocks diverged from a common ancestry during the middle part of the Trias. These two groups are included in an expanded Order Crocodylomorpha. The Suborder Crocodylia has the Triassic Stegomosuchidae as its radicle and contains ‘ normal ’ crocodiles (including the Sebecosuchia but not the Baurusuchidae). The suborder Paracrocodylia is proposed for mainly cursorial forms, to include the infraorders Pedeticosauria, Baurusuchia and Hallopoda. Diagnoses for these groupings are presented. An origin for both stocks from a form close to Cerritosaurus is postulated. Erpetosuchus and Dyoplax are not now regarded as crocodilomorphs. The possibility of an early cursorial phase in crocodilian evolution is briefly discussed, and it is tentatively suggested that the gallop occasionally observed in young crocodiles (Cott 1961) may be a relic of a primitive type of locomotion in the group. The significance of this to the emergence of the crocodilian type of shoulder-girdle is considered.

Sauria is the crown-group of Diapsida and is subdivided into Lepidosauromorpha and Archosauromorpha, comprising a high percentage of the diversity of living and fossil tetrapods. The split between lepidosauromorphs and archosauromorphs (the crocodile-lizard, or bird-lizard, divergence) is considered one of the key calibration points for molecular analyses of tetrapod phylogeny. Saurians have a very rich Mesozoic and Cenozoic fossil record, but their late Paleozoic (Permian) record is problematic. Several Permian specimens have been referred to Sauria, but the phylogenetic affinity of some of these records remains questionable. We reexamine and review all of these specimens here, providing new data on early saurian evolution including osteohistology, and present a new morphological phylogenetic dataset. We support previous studies that find that no valid Permian record for Lepidosauromorpha, and we also reject some of the previous referrals of Permian specimens to Archosauromorpha. The most informative Permian archosauromorph is Protorosaurus speneri from the middle Late Permian of Western Europe. A historically problematic specimen from the Late Permian of Tanzania is redescribed and reidentified as a new genus and species of basal archosauromorph: Aenigmastropheus parringtoni. The supposed protorosaur Eorasaurus olsoni from the Late Permian of Russia is recovered among Archosauriformes and may be the oldest known member of the group but the phylogenetic support for this position is low. The assignment of Archosaurus rossicus from the latest Permian of Russia to the archosauromorph clade Proterosuchidae is supported. Our revision suggests a minimum fossil calibration date for the crocodile-lizard split of 254.7 Ma. The occurrences of basal archosauromorphs in the northern (30°N) and southern (55°S) parts of Pangea imply a wider paleobiogeographic distribution for the group during the Late Permian than previously appreciated. Early archosauromorph growth strategies appear to be more diverse than previously suggested based on new data on the osteohistology of Aenigmastropheus.