ostertagia ostertagi , commonly known as the medium or brown stomach worm , is an important parasitic nematode ( round worm ) of cattle .

o. ostertagi can also be found to a lesser extent in sheep , goats , wild ruminants and horses .

the species causes ostertagiosis , which is potentially fatal in cattle .

it is found worldwide and is economically important to cattle industries , particularly those found in temperate climates .

the abomasal nematode o. ostertagi is a clade v nematode of the order strongylida , the family trichostrongylidae and genus ostertagia .

ransom first described the genus ostertagia in 1907 , which currently contains approximately 15 species .

all species of the genus ostertagia infect domestic or wild ruminants .

these species form a large and complex group , the taxonomy of which has not been fully elucidated .

ostertagia ostertagi

aspects of the biology of ostertagia ostertagi in relation to the genesis of ostertagiasis .
the pathology following single infections of ostertagia ostertagi in calves . - pubmed - ncbi
pathophysiological and parasitological studies on ostertagia ostertagi infections in calves . - pubmed - ncbi
development of immunity to ostertagia ostertagi ( trichostrongylidae : nematoda ) in pastured young cattle .
comparative morphology of ostertagia mossi and ostertagia dikmansi ( trichostrongylidae ) from odocoileus virginianus and comments on other ostertagia spp . from the cervidae
effect of experimental ostertagia ostertagi infection or chronic pentagastrin treatment on abomasal pathophysiology and morphology of goats .
comparative morphology of ostertagia mossi and ostertagia dikmansi ( trichostrongylidae ) from odocoileus virginianus and comments on other ostertagia spp . from the cervidae | springerlink
aspects of the biology of ostertagia ostertagi in relation to the genesis of ostertagiasis . - pubmed - ncbi
ostertagia and teladorsagia spp , parasitic brown stomach worms of cattle , sheep and goats . biology , prevention and control . ostertagiasis . ostertagia lyrata , ostertagia ostertagii , teadorsagia circumcincta , teladorsagia pinnata , ostertagia circumcincta
development of immunity to ostertagia ostertagi ( trichostrongylidae : nematoda ) in pastured young cattle . - pubmed - ncbi
fox mt ( 1993 ) pathophysiology of infection with ostertagia ostertagi in cattle . vet parasitol 46 : 143–158 .
ostertagia species are found throughout temperate and subtropical areas of the world . the cattle species , ostertagia ostertagi is particularly important in temperate areas wherever cattle are raised .
armour j , bruce rg . inhibited development in ostertagia ostertagi infections - - a diapause phenomenon in a nematode .
analysis of the translationally controlled tumour protein in the nematodes ostertagia ostertagi and caenorhabditis elegans suggests a pivotal role in egg production .
michel jf , lancaster mb , hong c , berrett s . plasma pepsinogen levels in some experimental infections of ostertagia ostertagi in cattle .
analysis of the translationally controlled tumour protein in the nematodes ostertagia ostertagi and caenorhabditis elegans suggests a pivotal role . . . - pubmed - ncbi
michel jf , lancaster mb , hong c ( 1973 ) ostertagia ostertagi : protective immunity in calves . the development in calves of a protective immunity to infection with ostertagia ostertagi . exp parasitol 33 : 179–186 . 0014 - 4894 ( 73 ) 90023 - 4 [ pii ] .
assessing the agreement between ostertagia ostertagi elisa tests performed using the crude adult antigen and the adult and larval stage 4 excretory / secretory antigens .
ostertagia ostertagi in various stages of development . a unembryonated egg . b early embryonated egg . c embryonated egg . d first - stage larvae , l1
assessing the agreement between ostertagia ostertagi elisa tests performed using the crude adult antigen and the adult and larval stage 4 excretory . . . - pubmed - ncbi
michel jf , lancaster mb , hong c : ostertagia ostertagi : protective immunity in calves . the development in calves of a protective immunity to infection with ostertagia ostertagi . exp parasitol . 1973 , 33 ( 1 ) : 179 - 186 . 10 . 1016 / 0014 - 4894 ( 73 ) 90023 - 4 .
fenbendazole ( white drench ) and levamisole ( clear drench ) against ostertagia ostertagi was less than fully effective on 43 % and 53 % of farms tested , respectively .
pge occurs when parasitic infestations in the abomasum and intestines result in inflammation of the gastrointestinal mucosa . in the uk ostertagia ostertagi is of biggest concern with cooperia contributing to disease .
ritchie jd , anderson n , armour j , jarrett wf , jennings fw , urquhart gm . experimental ostertagia ostertagi infections in calves : parasitology and pathogenesis of a single infection .
disease caused by o . ostertagi is divided into two forms , type i and type ii .
identification and mean number of each species of abomasal nematode identified are presented in table 4 . ostertagia leptospicularis ( o . l ) 67 % and spiculopteragia asymmetrica ( s . a . ) 26 % were the predominant ostertagia - type species present . present but in lower numbers were spiculopteragia spiculoptera ( s . s ) 5 % and ostertagia ostertagi ( o . o ) 2 %
ross jg , dow c : the course and development of the abomasal lesions in calves experimentally infected with the nematode parasite ostertagia ostertagi . brit vet j . 1965 , 121 : 228 - 233 .
trefoil factor 3 immunofluorescent staining ( green ) , combined with dapi staining ( blue ) . formalin fixed , paraffin - embedded abomasum sections of holstein cows after ostertagia ostertagi infection were stained . ( a ) negative control , ( b ) exposed to o . ostertagi for 60 days . original magnification 20× .
these worms are often called ‘osties’ or ‘osters’ , short for ostertagia . however , the worm was reclassified in the early 1990s , with the genus name changing from ostertagia to teladorsagia . while ostertagia is a name still commonly used , they are also now called “tellies” , short for teladorsagia .
ostertagia ostertagii infects mainly cattle , but also sheep , goats and other domestic and wild ruminants .
markovits , judit eva ,
effect of experimental ostertagia ostertagi infection or chronic pentagastrin treatment on abomasal pathophysiology and morphology of goats .
( 1986 ) . lsu historical dissertations and theses . 4193 . urltoken
the datasets supporting the conclusions of this article are included within the article and its additional files . ostertagia ostertagi its2 sequence : genbank accession number ab245021 . 2 | : 1 , 036–1 , 126 bp .
vercauteren , isabel , peter geldhof , iris peelaers , et al . “defining the composition of ostertagia ostertagi excretory - secretory products . ” molecular and cellular biology of helminth parasites , abstracts . 2002 . print .
this report is about the identification of parasite ostertagia ostertagi in cattle with persistent diarrhea . a farmer brought the fecal samples to national veterinary laboratories , islamabad from the village “charaa” , islamabad . he was having total of four animals including one cattle and three calves . cattle approximately 8 year old and have persistent diarrhea with the interval of 2 months after microscopic fecal examination it was conformed that animal was infested by ostertagia ostertagi .
efficacy of levamisole , moxidectin oral , moxidectin injectable and monepantel against ostertagia - type nematodes in deer .
our main objective was to assess whether feeding sainfoin has an effect on pathophysiological and parasitological measurements in calves experimentally infected with the most pathogenic and prevalent gin of cattle in temperate regions : ostertagia ostertagi and cooperia oncophora .
vercauteren i , geldhof p , peelaers i , claerebout e , berx g , vercruysse j . defining the composition of ostertagia ostertagi excretory - secretory products . molecular and cellular biology of helminth parasites , abstracts . 2002 .
predilection sites of adult ostertagia and teladorsagia worms are the stomach ( abomasum ) and the upper small intestine .
disease is caused by maturation of ostertagia ostertagi larvae ( ostertagiosis ) in the abomasum ( fourth stomach ) . unlike disease caus + ed by lungworm and liver fluke , pge does not usually cause clinical disease in adult cattle .
the following table summarizes the relevant information about ostertagia ostertagi , a nematode parasite of cattle found commonly throughout temperate areas of the world , and haemonchus contortus a nematode of sheep found throughout the world in warm temperate and subtropical areas .
' type ii ostertagiasis : ostertagia ostertagi may become hypobiotic in the autumn and if these infestation are heavy , lots of hypobiotic larvae reactivate in the spring . this causes severe acute gastritis ( fibrinous or haemorrhagic ) , and even sudden death .
vercauteren , isabel , peter geldhof , iris peelaers , edwin claerebout , g berx , and jozef vercruysse . 2002 . “defining the composition of ostertagia ostertagi excretory - secretory products . ” in molecular and cellular biology of helminth parasites , abstracts .
lectin staining with ueai ( a - l - fucosyl terminals ) . carnoy ' s fixed , paraffin - embedded abomasum sections of holstein cows after ostertagia ostertagi infection were stained . ( a and c ) negative control , ( b and d ) exposed to o . ostertagi for 21 days . original magnification 20× ( left panels ) , 40× ( right panels ) .
citation : li rw , wu s , li w , huang y , gasbarre lc ( 2011 ) metagenome plasticity of the bovine abomasal microbiota in immune animals in response to ostertagia ostertagi infection . plos one 6 ( 9 ) : e24417 . urltoken
as already mentioned , ostertagia and teladorsagia are the most damaging worms of cattle in regions with temperate and cool climate .
as leaders in parasite control bimeda have a range of anthelmintics which can be used to successfully treat ostertagia and cooperia .
deer , anthelmintic resistance , anthelmintic efficacy , gastrointestinal parasites , ostertagia , levamisole , moxidectin injection , moxidectin oral , monepantel .
the main roundworm of cattle is ostertagia ostertagi , known commonly as the brown stomach worm . control of ostertagia will incidentally control other roundworms of lesser importance such as the smallå intestinal worm ( cooperia sp ) . occasionally , the stomach hairworm ( trichostrongylus . axei ) can be the predominant parasite but , more importantly , it is the only roundworm species that infects both sheep and cattle .
brown stomach worm occurs in most sheep and goat areas of australia and is a major parasite in winter rainfall districts . it is relatively rare in queensland . the brown stomach worm of cattle , ostertagia ostertagi is known to infect angora goats , but not sheep .
lectin staining , subjectively described from + + ( very strong ) to - ( absent ) during a primary infection with o . ostertagi .
purewal a , fox mt , shivalkar p , carroll ap , uche ue , vaillant c , watkinson a ( 1997 ) effects of ostertagia ostertagi on gastrin gene expression and gastrin - related responses in the calf . j physiol 498 ( pt 3 ) : 809–816 .
there are two types of disease caused by ostertagia . the signs of each type result from the same damage to the abomasum :
ostertagia and teladorsagia spp , parasitic brown stomach worms of cattle , sheep and goats . biology , prevention and control . ostertagiasis .
acquired immunity against cooperia spp . and ostertagia spp . in calves : effect of level of exposure and timing of the midsummer increase
although there are a number of nematode parasites known to be present in wa cattle only the two species that make up the bulk of typical worm burdens are reported here . these two species are cooperia oncophora ( hair worm ) and ostertagia ostertagi ( brown stomach worm ) .
the mcdonnell genome institute and collaborators are sequencing the bovine stomach worm , ostertagia ostertagi . this is the most economically important parasite of cattle throughout temperate regions of the world . globally , these small reddish brown worms are the major cause of parasitic gastritis ( ostertagiosis ) of ruminants .
claerebout e , hilderson h , meeus p , de marez t , behnke j , huntley j , vercruysse j : the effect of truncated infections with ostertagia ostertagi on the development of acquired resistance in calves . vet parasitol . 1996 , 66 ( 3–4 ) : 225 - 239 .
in this paper we describe molecular characterization of opa , an ostertagia polyprotein , and its potential to induce protection against homologous infection in cattle .
there were four ostertagia - type nematode species identified in the deer on this farm . the two spiculopteragia species of ostertagia - type nematodes ( s . spiculoptera and s . asymmetrica ) present are host specific to deer . ostertagia leptospicularis is a deer species but it has been reported in both sheep and cattle in new zealand ( mckenna 1997 ) . ostertagia ostertagi is an important cattle nematode previously only observed in white - tail deer in new zealand ( mckenna 1997 ) but made up 2 % of the ostertagia - type species present in these deer and 3 % on another te anau deer farm ( lawrence et al 2012 ) . it is worthy of note that the sheep ostertagia - type nematode ( teladorsagia ) was not present on this farm and in fact has never been identified in farmed deer in new zealand to date . on this farm moxidectin pour on was not evaluated and all of the ostertagia - type species were well controlled by moxi . spiculopteragia asymmetrica was the species showing the least efficacy to moxo on this farm . technically resistance to an anthelmintic can only be claimed if the dose rate to provide efficacy has been determined . the dose rate in deer for moxo has not been determined and therefore we cannot claim spiculopteragia asymmetrica is resistant on this farm . interpretation of the efficacies of oxo and levo is not appropriate in light of previous discussion regarding the need to determine / re - evaluate the correct dose of these anthelmintics in deer . previous reports on new zealand deer farms indicated ostertagia - type species exhibiting resistance to macrocyclic lactone anthelmintics . ostertagia leptospicularis was resistant to moxidectin pour on ( lawrence et al 2012 ) , ostertagia leptospicularis and spiculopteragia spiculoptera to moxidectin pour on and moxi ( lawrence 2011 ) , and ostertagia leptospicularis resistant to moxidectin pour on and ostertagia leptospicularis , spiculopteragia spiculoptera and spiculopteragia asymmetrica to ivermectin oral ( hoskin et al 2005 ) .
the internal transcribed spacer 2 ( its2 ) is a candidate diagnostic marker of the pathogenic cattle nematode ostertagia ostertagi . the aims of this study were : ( i ) to document and quantify how the development of o . ostertagi eggs affects its2 copies under different storage conditions , and ( ii ) to suggest optimal storage conditions for faecal samples in a diagnostic pipeline that involves detection and semi - quantification by real - time semi - quantitative polymerase chain reaction ( qpcr ) .
li rw , hou y , li c , gasbarre lc : localized complement activation in the development of protective immunity against ostertagia ostertagi infections in cattle . vet parasitol . 2010 , 174 ( 3 - 4 ) : 247 - 256 . 10 . 1016 / j . vetpar . 2010 . 08 . 037 .
some of the drenches in group 1 ( benzimidazoles ) have lesser and a more variable effect on the immature and inhibited stages of ostertagia than previously thought .
data ( mean ± sd ) representing worm burden by sieving , percentage males and female fecundity based on the number of eggs in utero from 16 female worms per animal . the calves were experimentally infected with ostertagia ostertagi and cooperia oncophora and fed a tannin - rich diet ( group sf ) or a control diet ( group co )
the common stomach worms of cattle are haemonchus placei ( barber’s pole worm , large stomach worm , wire worm ) , ostertagia ostertagi ( medium or brown stomach worm ) , and trichostrongylus axei ( small stomach worm , see trichostrongylus sp in horses ) . in some tropical countries , mecistocirrus digitatus , a large worm up to 40 mm long , is present . h placei is primarily a parasite in tropical regions , whereas o ostertagi and , to a lesser extent , t axei are found in more temperate climates . adult male haemonchus are up to 18 mm long , females up to 30 mm . ostertagia adults are 6–9 mm long , and trichostrongylus , ~ 5 mm .
the objectives of this study were first to molecularly characterize the ostertagia polyprotein allergen ( opa ) ( e . g . , to determine the genomic organization , expression pattern , and immunolocalization ) and then to investigate the protective capacities of both purified native opa ( nopa ) and recombinant opa ( ropa ) in cattle challenged with o . ostertagi .
its2 copies of four developmental stages of ostertagia ostertagi . sample mean of its2 copies ( molecules μl - 1 ) illustrated on the y - axis plotted against each developmental stage ( x - axis ) . error bars indicate standard error of the mean ( sem ) . asterisks denote statistical significance : * * * = p < 0 . 0001
vercauteren , isabel , geldhof , p . , peelaers , i . , claerebout , e . , berx , g . , & vercruysse , j . ( 2002 ) . defining the composition of ostertagia ostertagi excretory - secretory products . molecular and cellular biology of helminth parasites , abstracts . presented at the molecular and cellular biology of helminth parasites .
li rw , hou y , li c , gasbarre lc ( 2010 ) localized complement activation in the development of protective immunity against ostertagia ostertagi infections in cattle . vet parasitol 174 : 247–256 . s0304 - 4017 ( 10 ) 00492 - 9 [ pii ] ; 10 . 1016 / j . vetpar . 2010 . 08 . 037 [ doi ] .
external structural changes of adult ostertagia ostertagi recovered from calves fed sainfoin for 58 days . scanning electron microscopy of representative worms recovered 42 days post - infection from control group ( co ) ( a , b ) or sainfoin group ( sf ) ( c , d ) . left column : tail of the female worm ; right column : close view of the cuticle
at present , the control of ostertagia ostertagi infections in cattle largely depends on the use of chemical antihelminthic drugs . residues of introduced chemicals in foodstuffs and the environment have become a serious consumer concern . reports of resistance to antiparasitic drugs for a closely related parasite , cooperia species , in cattle ( 5 , 31 ) make the development of alternative control systems even more urgent .
the predominant worm type present in all 6 con deer was ostertagia - type and interestingly there were no cooperia present . the large intestinal parasite oesophagostomum was present in 3 of the six deer . table1 ; faecal larval culture ( flc ) worm type control group averagehaemonchus - ostertagia - type 69 % trichostrongylus 11 % cooperia - oesophagostomum / chabertia 20 % nematodirus -
early attempts to protect cattle against the abomasal nematode o . ostertagi with irradiated larval vaccines ( 2 ) or with crude somatic ( 12 ) and excretory - secretory ( es ) products ( 13 ) were not successful . moderate levels of protection were obtained in calves immunized with gut membrane glycoproteins of o . ostertagi ( 24 ) . recently , it was shown that vaccination of cattle with es products of adult ostertagia worms enriched for cysteine proteinases by thiol - sepharose chromatography reduced the fecal egg counts by 60 % compared to the counts in the control group ( 11 ) .
transcript expression in different developmental stages . this figure represents the number of transcripts expressed in each stage and the percent of those transcripts that are constitutively - expressed in c . oncophora ( a ) and o . ostertagi ( b ) . ( c ) c . oncophora and ( d ) o . ostertagi depict the number of transcripts up - regulated , down - regulated and specific to a given stage .
table 2 : group mean total worm counts for adult and immature ostertagia - types . anthelmintic treatment group efficacy against ostertagia - type adults . oster - type adults oster - type larvacontrol 1495 17moxi % efficacy 0100 % 67moxo % efficacy 3297 . 9 % 173oxo 42271 . 8 % 173levo 42371 . 7 % 118moxi + oxlevo 0100 % 14 . 5zolo 20086 . 6 % 14
concurrent with the diarrhea of o ostertagi and t axei infections , and with the anemia of heavy haemonchus infection , there is often hypoproteinemia and edema ( rare in o ostertagi infections ) , particularly under the lower jaw ( bottle jaw ) and sometimes along the ventral abdomen . heavy infections can result in death before clinical signs appear . other variable signs include progressive weight loss , weakness , rough coat , and anorexia .
note that routine treatment of adult cows after their second calving is not needed . individual cows in this group may be treated if they are scouring or losing condition because of infection with ostertagia .
a lot of research has been carried out on vaccines , but so far no really effective one is available against ostertagia and / or teladorsagia worms . to learn more about vaccines against parasites of livestock and pets
no fluorescence was detected in sections of ostertagia developed with preimmune rabbit serum ( fig . 2i ) or with the irrelevant rabbit serum ( antiscabies serum ) or in the conjugate controls ( data not shown ) .
cooperia oncophora and ostertagia ostertagi are among the most important gastrointestinal nematodes of cattle worldwide . the economic losses caused by these parasites are on the order of hundreds of millions of dollars per year . conventional treatment of these parasites is through anthelmintic drugs ; however , as resistance to anthelmintics increases , overall effectiveness has begun decreasing . new methods of control and alternative drug targets are necessary . in - depth analysis of transcriptomic data can help provide these targets .
most infections are mixed with other gastrointestinal roundworms ( e . g . cooperia spp , haemonchus spp , nematodirus spp , trichostrongylus spp , etc . ) which worsen the damage caused by ostertagia and / or teladorsagia worms .
' type i ostertagiasis : ostertagia ostertagi is ingested by calves in their first year at grass . the parasites colonise the gastric glands of the fundus and pylorus and then 17 - 21 days after ingestion , the parasites reach maturity and emerge from the gastric glands . emergence in sufficient numbers causes extensive pathological changes - chronic gastritis . a thickened , hyperplastic , non - functional gastric mucosa is formed , meaning impaired function in the gut resulting in diarrhoea and hypoalbuminaemia .
in an experiment in which 2 plots of pasture were contaminated , one at the end of september and the other in mid - december , with larvae of ostertagia ostertagi and cooperia oncophora , it was found that the ability of these larvae to interrupt their parasitic development increased and then decreased at much the same rate on either plot . seasonal effects , which might have been expected to accelerate these changes in larvae put on the pasture in december , were minimal .
schematic overview of the study design . anaerobic samples ( n = 9 × 2 ) contained 10 g of freshly recovered faeces with ostertagia ostertagi eggs and stored in vacuum bags under anaerobic conditions . samples were subjected to either 4 °c or 25 °c for duration of 0 to 336 h . to stop egg development the samples were frozen at - 20 °c . subsequently , o . ostertagi were isolated and differentiated to developmental stage . finally , 25× o . ostertagi eggs or l1 were counted and transferred to a clean petri dish . this was done in triplicates of each sample and its2 copies were quantified by qpcr . aerobic samples ( n = 9 × 2 ) were produced identically to anaerobic samples but eggs were isolated from faeces before storage and differentiated immediately at each time point . a total of 108 biological replicates were subjected to qpcr semi - quantification . abbreviations : epg , eggs per gram ; its2 , internal transcribed spacer 2 ; qpcr , real - time semi - quantitative polymerase chain reaction
that infect cattle , sheep and goats and other wild ruminants . worms of these genera are also called brown stomach worms . in the past most species were considered as belonging to the genus ostertagia . they have very similar features and life cycles .
ostertagia and other roundworms of cattle have a simple direct life cycle , as shown in figure 1 . an important feature of this life cycle is that it consists of two stages ; the free - living stage on pasture and parasitic stage in cattle .
the con group slaughtered on the 16th october had an average of 1495 ostertagia - type adults ( range 250 – 2650 ) . based on this result , the trial proceeded . all treated deer were slaughtered on the 31st october . the anthelmintics had the following efficacy against the adult ostertagia - type nematodes : moxi 100 % , moxo 97 . 9 % , oxo 71 . 8 % , levo 71 . 7 % , moxi + oxlevo 100 % and zolo 86 . 6 % ( table 2 ) .
pelleted sainfoin as a sole feed significantly reduced the population of o . ostertagi in young calves . our promising results confirm the potential value of sainfoin and perhaps other tannin - rich forages with a high percentage of prodelphinidins in integrated control of bovine ostertagiosis . although o . ostertagi is the main species responsible for reduced productivity in grazing calves , the apparent lack of effect against c . oncophora is a drawback and may hamper the practical use of sainfoin as a “broad - spectrum” anthelmintic forage . more research is needed to address the background of the lacking effect against c . oncophora .
abubucker s , zarlenga ds , martin j , yin y , wang z , mccarter jp , gasbarree l , wilson rk , mitreva m : the transcriptomes of the cattle parasitic nematode ostertagia ostartagi . vet parasitol . 2009 , 162 ( 1–2 ) : 89 - 99 .
clustering of stages based upon the number of transcripts in a stage containing a specific interpro domain . ( a ) c . oncophora ; ( b ) o . ostertagi . a lower - range scale ( 0 to 3 + ) was used to better illustrate the similarities and differences between the stages .
pre - type 2 phase : calves at end of first grazing season ( from october ) accumulate large population ( greater than 100 , 000 ) of ostertagia el4 ( arrested stage ) . disease is caused by l3 ingested in late autumn . there are usually no clinical signs .
ostertagia ostertagi . the nematode grows and develops in the gastric glands of the abomasum which it leaves just before it becomes an adult , approximately 17 - 21 days after infection . during its time in a gastric gland , the nematode grows about 100 fold . therefore we can predict that this growth will result in erosion of the secretory epithelium and also that swelling of the gland will occur . in heavy infections these erosive effects can be widespread resulting in heavy losses of secretory cells and significant reductions in the output of hcl and pepsinogen . these changes are summarized in the table below .
distribution of kegg categories associated with up - regulated transcripts . the number of up - regulated transcripts in free - living and parasitic life stages associated with kegg categories is compared in ( a ) c . oncophora and ( b ) o . ostertagi . * indicates significance ( p < 0 . 05 ) .
additional file 2 : figure s1 : length distribution of peptides with and without homologues in other species . description : histogram of the length of peptides that have homologues in other species and those that do not have homologues i . e . are unique to either c . oncophora or o . ostertagi . ( tiff 249 kb )
on sections of ostertagia parasites clear red fluorescence was observed in the intestinal cells of l3 animals ( fig . 2b ) , in the cuticle of l4 animals ( fig . 2d ) , and in the cuticle and hypodermis of both male and female adult worms ( fig . 2f and h ) .
the aims of this study were : ( i ) to document and quantify how the development of o . ostertagi eggs affects its2 copies under a multitude of storage conditions , and ( ii ) to suggest optimal storage conditions for faecal samples / bovine nematode eggs in a diagnostic pipeline that involves detection and semi - quantification by molecular methodologies .
simcock dc , joblin kn , scott i , burgess dm , rogers cw , pomroy we , simpson hv ( 1999 ) hypergastrinaemia , abomasal bacterial population densities and ph in sheep infected with ostertagia circumcincta . int j parasitol 29 : 1053–1063 . s0020 - 7519 ( 99 ) 00065 - x [ pii ] .
ivermectin is a cost effective treatment for gastrointestinal roundworms . at the therapeutic dose ivermectin will successfully treat the inhibited stage of ostertagia making it an excellent choice . bimeda provide ivermectin in an injectable and pour - on form and also in combination with clorsulon ( bimectin plus ) which can be used to treat liver fluke .
histochemical staining of carnoy ' s fixed , paraffin - embedded abomasum sections of holstein cows after ostertagia ostertagi infection . pas ( a - d ) stained mucins in pink ; ab - pas ph 2 . 5 ( e - h ) stained neutral mucins in magenta and acidic mucins in blue ; hid - ab ( i - n ) stained sialylated mucins in blue and sulphated mucins in brown . ( a , e , i ) negative control , ( b , f , l ) infected for 14 days , ( c , g , m ) infected for 21 days , ( d , h , n ) exposed for 60 days . original magnification 10× .
the amino acid sequences of all visible bands , as determined by maldi - tof mass spectrometry analysis , showed that all of the protein bands represented nopa or ropa . the nopa band , however , comprised traces of a protein homologous to a 17 - kda l3 es antigen of ostertagia ( embl accession no . aj318472 ) .
go term associations with transcripts expressed in each stage . for each phase of the life cycle ( free - living or parasitic ) several prevalent go terms are listed . * indicates a given term is significantly - enriched in that life cycle stage ( p < 0 . 05 ) . ( a ) c . oncophora ; ( b ) o . ostertagi .
fifteen jersey male calves ( 2–4 month - old ) were allocated into two groups and fed isoproteic and isoenergetic diets mainly composed of sainfoin pellets ( group sf ; n = 9 , three pens ) or concentrate and grass - clover hay ( group co ; n = 6 , two pens ) . after 16 days of adaptation , all animals were experimentally infected with 10 , 000 and 66 , 000 third - stage larvae of ostertagia ostertagi and cooperia oncophora , respectively . egg excretion , blood parameters and bodyweights were recorded throughout the study . worms were harvested by sieving for quantification and scanning electron microscopy ( sem ) 42 days post - infection ( dpi ) when the calves were necropsied .
moxidectin pour on has been the formulation of moxidectin which has consistently shown resistance by ostertagia - type nematodes on all deer farms evaluated to date ( n = 6 ) . with this knowledge and the desire to evaluate additional treatment groups , budget restraints meant that moxidectin pour on was not included as a treatment option in this trial .
it is important to stress that an ostertagia vaccine in cattle needs to be an antifecundity vaccine ( 30 ) . as the number of worm eggs shed during the first part of the grazing season determines the number of infective larvae in the pasture in the second half of the grazing season , reduction in egg excretion should be the target . also , because the fecundity of ostertagia is highly regulated by host immunity ( 23 ) and fecal egg output can be strongly reduced without a reduction in the number of worms ( 9 , 4 ) , the number of eggs per gram is the best parameter for evaluation of the protective efficacy of ostertagia antigens ( 30 ) . analogous with observations on the effects of antihelminthic boli on gastrointestinal nematodes in cattle ( 8 ) , it can be stated that vaccination with nopa that results in a 60 % reduction in the number of eggs per gram for at least 2 months is sufficient to protect first - grazing - season calves from ostertagiosis without interfering with the development of natural immunity .
in order to create anaerobic conditions , faeces containing o . ostertagi eggs were vacuum - packed using an easily available kitchen machine . while purified o . ostertagi eggs will quickly disrupt due to pressure if they are vacuum - packed ( data not shown ) , storage of eggs in faeces was essential to secure the integrity of the parasites and maintain a realistic evaluation of the vacuum packing strategy . thus , faeces were only present during storage of the anaerobic samples but not during storage of aerobic samples , and therefore the outcome may potentially have been influenced by other factors such as e . g . ph and humidity rather than oxygen tension . incorporation of an inhibition control by spiking a non - related target to the samples could confirm any presence of potential inhibitors .
distribution of protein homologues in free - living nematodes , strongylida parasites , and non - strongylida parasites . the percent of homologues in each of the three databases as well as the overlap between the databases is shown . ( a ) . c . oncophora ; ( b ) . o . ostertagi . for species included in each of the three databases please see the materials and methods .
the numbers of ostertagia - type larvae present in the control group was very low and as a result no conclusions can be drawn as to efficacy of the various anthelmintics against larvae from this trial . trichostrongylus nematodes were present in the con but in low numbers ( average 23 ) . all treatment groups were clear except the levo group ( average 2 ) .
the pour - on formulations of levamisole have also given variable results in adult cattle in winter . the concentration of the drug in these formulations has been increased in response to these findings , but the lack of effect of levamisole on the inhibited larvae of ostertagia means that levamisole - based drenches are not ideally suited for use in beef cattle over 12 months old .
young animals are more often affected , but adults not previously exposed to infection frequently show signs and succumb . ostertagia and trichostrongylus infections are characterized by profuse , watery diarrhea that usually is persistent . in haemonchosis and mecistocirrus infection , there may be little or no diarrhea but possibly intermittent periods of constipation . anemia of variable degree is a characteristic sign of both these infections .
in an attempt to dissect mechanisms underlying protective immune responses to ostertagia ostertagi infections in cattle , which develops very slowly and requires a prolonged exposure before becoming effective , we developed partially immune animals using multiple drug - attenuated infections . while host mechanisms underlying the development of long - term protective immunity have recently been discussed [ 4 ] , the gut microbiota of ruminants has not been systematically characterized until recently [ 8 ] – [ 10 ] . three - way interactions between the host , its microbiota and parasites are little understood . in this study , we characterized the bovine abomasal microbiota using metagenomic tools . our results provided the first piece of evidence that a minimal disruption in the bovine abomasal microbiota by the parasitic nematode may contribute equally to the restoration of gastric function in immune animals .
hertzberg h , guscetti f , lischer c , kohler l , neiger r , et al . ( 2000 ) evidence for a parasite - mediated inhibition of abomasal acid secretion in sheep infected with ostertagia leptospicularis . vet j 159 : 238–251 . 10 . 1053 / tvjl . 1999 . 0475 [ doi ] ; s1090 - 0233 ( 99 ) 90475 - 6 [ pii ] .
the organization of the coding sequence of opa in genomic dna of ostertagia could indicate that there is only one copy of the opa gene . this is the case for the genes encoding npas of other nematodes , such as dirofilaria immitis ( 6 ) , brugia pahangi ( 27 ) , brugia malayi ( 27 ) , and d . viviparus ( 1 ) . the nopa antigen was located in the intestinal cells of ostertagia l3 and in the cuticle and hypodermis of l4 and adult parasites . similarly , immunostaining of di5 antigen , the opa homologue of d . immitis , was apparent in the hypodermis and the cuticle of the parasite ( 22 ) . in caenorhabditis elegans , npas have been found to bind fatty acids and retinol ( reviewed in reference 15 ) . in parasitic nematodes however , the major function of npas is to alter the host tissue environment to the parasites ' advantage ( 16 ) . the results of the immunolocalization analysis together with the western blot results indeed suggest that opa is secreted . release of opa into the environment could occur directly from the gut with the l3 stage or from the cuticle via the hypodemis with ostertagia l4 and adults .
the third - stage larvae ( l3 ) cannot feed , because they retain the cuticle (
skin
) from the second stage ( l2 ) as a protective sheath , but can survive for long periods within the dung pat . they can also move some distance away from the dung pat . the parasitic stage of the life cycle of ostertagia begins when a beast ingests l3 larvae .
this study characterized transcriptomes from multiple life stages from both c . oncophora and o . ostertagi . these data represent an important resource for studying these parasites . the results of this study show distinct differences in the genes involved in the free - living and parasitic life cycle stages . the data produced will enable better annotation of the upcoming genome sequences and will allow future comparative analyses of the biology , evolution and adaptation to parasitism in nematodes .
immunolocalization of opa . sections of l3 ( a and b ) , l4 ( c and d ) , and male ( e and f ) and female ( g and h ) adult o . ostertagi parasites were incubated with monospecific antibodies to opa , and antibody binding was detected by using alexa fluor - conjugated anti - rabbit immunoglobulin . female adult o . ostertagi parasites were also incubated with negative ( preimmune ) rabbit serum ( at a 1 / 2 , 000 dilution in 2 % hs ) ( i ) . panels a , c , e , and g are phase - contrast micrographs , and panels b , d , f , h , and i are fluorescence microscopy micrographs ( signal indicated by red fluorescence except in panel i ) . ic , intestinal cells ; i , intestine ; g , gonads ; h , hypodermis ; c , cuticle . bars = 25 μm .
generally , es products are considered to be essential for the development and survival of the parasite within the host and are targets for vaccine development ( 17 ) . immunoscreening of cdna libraries of both larvae ( third - stage larvae [ l3 ] and l4 ) and adults of ostertagia with polyclonal rabbit serum raised against es products led to identification of 15 genuinely secreted proteins with potential protective capacities ( 28 ) .
adult parasites of o . ostertagi were microscopically - selected from abomasal contents from animals killed 28 days post infection . cooperia oncophora eggs , l1 , l2 , l3sh and l3ex were also collected as described above . the l4 were obtained by baermannization of intestinal contents and washings from animals euthanized 10 days post infection ; adult worms were microscopically collected from animals euthanized 21 days post infection and further partitioned into male [ m ] and female [ f ] worms .
this occurs when ostertagia ostertagi infective larvae ( l3 ) are ingested by calves in their first or second year at grass . the parasites then take refuge in the gastric glands of the abomasum in order to undergo their period of development . if many worms emerge simultaneously then it can cause severe physical damage to the lining of the abomasum resulting in chronic gastritis . disease is observed in late summer / early autumn and is accountable to the ‘mid - summer rise’ when temperatures increase and many larvae quickly develop . affected calves will present with a decreased / total loss of appetite accompanied by a sudden onset profuse , green diarrhoea . generally many animals within the group are affected . these calves will suffer a severe loss of body condition ( 20 - 60kg ) which will greatly increase the time taken to finish ( up to three months extra ) . one paper suggests losses of up to £100 per head .
o . ostertagi infections can prompt protective immunity to ostertagiosis , making the species a good candidate for vaccine development . having a whole genome sequence for the species could also help with the development of novel methods to control these parasites in livestock , including defining the mechanisms underlying drug susceptibility and resistance with the possibility of extending the useful life of existing drugs and improving diagnostics in this area , as well as providing the means to study the host - parasite interaction in whole animals .
haemonchus contortus . in this example , unlike ostertagia , the parasite matures on the mucosal surface of the the abomasum . therefore its growth and development has little effect on the mucosa and makes no contribution to its pathogenic potential . despite the fact that adult haemonchus are no more than 1cm long , they are voracious blood feeders and it is this blood loss that is entirely responsible for the pathophysiological changes and clinical signs we see in haemonchosis .
although these findings indicate the presence of resistance in the ml group in cooperia oncophora on more than half of farms tested , it is unlikely that farmers using ml drenches are experiencing a major effect in terms of worm disease or production loss . this is because cooperia is considered to have a relatively less severe effect than most other species . importantly , the injectable mls were fully effective against ostertagia , which is the more important of the species .
friesian calves given a low level infection of the abomasal parasite ostertagia ostertagi over a six week period displayed a mild diarrhoea with high faecal egg counts and elevated plasma pepsinogen values . at necropsy on day 23 abomasal lesions characteristic of ostertagiasis were widespread . at 42 and 84 days oedema and congestion were also prominent . total worm burdens on days 23 and 42 were similar but a marked decrease had occurred by day 84 . feed digestibility and nitrogen economy were not markedly affected but radioisotopic measurements demonstrated an increase in albumin disappearance and catabolic rates , and plasma faecal clearance during the course of the infection . prior administration of a morantel sustained release bolus to a group of similarly infected calves reduced the total worm burdens to less than 50 per cent of those recorded in the infected calves on days 23 and 42 and this fell to 3 per cent on day 84 . abomasal damage and the adverse pathophysiological changes associated with infection were prevented in this group .
there was a total of 1393 transcripts identified as encoding putatively - secreted peptides of which 538 were enriched in at least one stage . it was determined that free - living stages tended to have more of these transcripts in common with each other than with the parasitic stages . parasitic stages tended to have a common pool of secreted peptides as well . the exception to this was c . oncophora l4 which shared more secreted peptides with the free - living stages than with the other parasitic stages . the 5 % of domains most prevalent in the secreted peptides were very similar between the two species . transthyretin - like , metridin - like shk toxin , saposin b , and cap domains were among the most prevalent for secreted proteins in both species . two insulin domains were among the most prevalent in secreted peptides of c . oncophora but were absent from o . ostertagi . ves allergen was found in 16 secreted peptides of o . ostertagi but was found in only one secreted peptide of c . oncophora .
eggs of ostertagia ostertagi were obtained from fresh faeces and stored at 4 °c or 25 °c under aerobic or anaerobic ( vacuum packing ) conditions . development was monitored by microscopy for up to 336 h , and the its2 copies were determined by qpcr from a fixed number of parasites . under aerobic conditions at 25 °c , embryonation and a significant increase of its2 copies ( p < 0 . 0001 ) were observed after 12 h . at 4 °c , embryonation occurred after 168 h with a trend towards increased its2 copies . anaerobic conditions inhibited egg development at both temperatures and no significant increase in its2 copies was noticed ( p = 0 . 90 ) . its2 copies were analysed for each parasite stage : first - stage larvae ( l1 ) exhibited significantly higher copy numbers ( 20 , 353 ± 1 , 950 ) than unembryonated eggs ( 568 ± 168 ; p < 0 . 0001 ) with lower coefficient of variation ( 33 vs 266 % ) .
log - transformed its2 copies plotted against developmental stages of ostertagia ostertagi throughout the four sub - experiments . a 4 °c under aerobic conditions . b 25 °c under aerobic conditions . c 4 °c under anaerobic conditions . d 25 °c under anaerobic conditions . the x - axis indicates storage time . distributions ( % ) of developmental stages are plotted on left y - axis ( white bar : unembryonated eggs ; brown bar : early embryonated eggs ; green bar : embryonated eggs ; yellow dotted bar : l1 larvae ; shaded bar : decomposed parasites ) . developmental stage was determined from photographs of 15 randomly selected eggs from each of nine time points . log - transformed its2 copies are plotted on right y - axis and are indicated by a black line . its2 copies were obtained from qpcr analysis of biological triplicate samples containing dna from 25 parasites ( eggs or larvae ) . error bars indicate standard error of the mean ( sem ) of log - transformed its2 copies
table 4 : mean worm count and anthelmintic efficiency by ostertagia - type species o . o o . l s . a s . scontrol 30 1002 389 75moxi 0 0 0 0 % efficacy 100 % 100 % 100 % 100 % moxo 0 0 32 0 % efficacy 100 % 100 % 91 . 8 % 100 % oxo 0 333 42 42 % efficacy 100 % 66 . 8 % 44 % 44 % levo 0 186 152 85 % efficacy 100 % 81 . 4 % 60 . 9 % 0 %
type 2 occurs when the ostertagia ( l3 ) ingested in late autumn do not emerge immediately and instead remain in the gastric glands in a hypobiotic state . these larvae are stimulated to emerge in the late winter / early spring ( feb - may ) and if the infestation is heavy then they will cause great damage as they do so . this causes an acute gastritis and in severe cases sudden death . routine treatment at housing and or when housed will prevent this which is preferable as response to treatment is generally very poor .
species - level microbial composition in the bovine abomasal microbiota was analyzed using cd - hit - otu ( wu et al . , 2011 , submitted ) . a total of 90 . 3±2 . 9 otu were identified in each abomasal microbial community . seventy two otu were present in the abomasal microbial communities of all 6 immune animals and likely represented the core microbiome of the abomasal microbial community . the community was dominated by 4 otu , which accounted for approximately 50 % of all 16s rdna sequences in control animals . among them , 2 otu ( otu # 1 , 22 . 9 % and otu # 7 , 8 . 1 % ) were annotated to the genus prevotella while the rest 2 otu belonged to bacteroidales and succinivibrio . ostertagi ostertagi infection significantly impacted only 2 otu in immune animals ( unadjusted p value < 0 . 05 ) . the relative abundance of otu # 32 ( lineage : catabacteriaceae ) was increased from 0 . 4 % in control to 1 . 0 % in infected animals while the relative abundance of otu # 25 decreased from 0 . 3 % in control to 0 . 1 % in infected animals ( p < 0 . 05 ) .
worms can readily be seen and identified in the abomasum , and small petechiae may be visible where the worms have been feeding . the most characteristic lesions of ostertagia infection are small , umbilicated nodules 1–2 mm in diameter . these may be discrete , but in heavy infections they tend to coalesce and give rise to a “cobblestone” or “morocco leather” appearance . nodules are most marked in the fundic region but may cover the entire abomasal mucosa and may be accompanied by a rise in gastric ph to 6–7 . as a result , pepsinogen will no longer be converted to pepsin and may leak across the damaged epithelium , leading to high plasma levels . there is also evidence that adult ostertagia can cause direct hypersecretion of pepsinogen . the increased abomasal ph may also stimulate production of gastrin and thus hypergastrinemia , which is closely associated with the inappetence that may accompany infection . this parasite - associated drop in intake has been shown to be largely responsible for impaired weight gain . edema is often marked and , in severe cases , may extend over the abomasum and into the small intestine and omentum .
aerobic storage of o . ostertagi eggs at 25 °c led to a significant increase in its2 copies after 12 h due to embryonation and subsequent hatching . in contrast , anaerobic storage ( vacuum packing ) at 25 °c completely inhibited egg development and any undesirable semi - quantification bias for up to 336 h . hence , vacuum packing is an optimal storage strategy prior to molecular diagnostic analyses . alternatively , aerobic storage at 4 °c for up to 72 h can be used . due to high copy numbers and lower genetic variation , the l1 stage may be considered for diagnostics and further molecular research .
aerobic storage of o . ostertagi eggs at 25 °c led to a significant increase in its2 copies from 12 h due to embryonation and subsequent hatching . in contrast , anaerobic storage ( vacuum packing ) at 25 °c completely inhibited egg development and any undesirable semi - quantification bias for up to 336 h . hence , vacuum packing is an optimal storage strategy prior to molecular diagnostic analyses . alternatively , aerobic storage at 4 °c for up to 72 h can be used . due to high copy numbers and less genetic variation , the l1 stage may be considered for diagnostics and further molecular research .
the objective of this study was to determine the agreement between elisa tests conducted using three o . ostertagia antigens : crude adult worm , larval stage 4 ( l4 ) excretory / secretory ( es ) and adult es . this study was carried out on 289 holstein cows from five herds in prince edward island and one herd in nova scotia . composite milk samples of these cows were collected ( between may and september 2002 ) from the respective provincial laboratories and sent to the atlantic veterinary college where each sample was tested for antibodies to o . ostertagi using an indirect microtitre elisa test . results were expressed as optical density ratio ( odr ) values . each milk sample was tested with three elisa tests , with each test using a different o . ostertagi antigen . there was a slight rise in odr values of both adult antigens , between may and august , with higher values obtained using the adult es antigen . l4 es odr values were generally higher than those for both adult antigens during the study period , except for may . there was a more dramatic rise in l4 es odr values between may and august . rises in odr in may and end of july coincided with periods of mass maturation of l4 to adult worms . the results of the study showed that the concordance correlation coefficient ( ccc ) between tests performed using both es and the crude antigens were low ( crude adult versus adult es = 0 . 31 , crude adult versus l4 es = 0 . 30 ) . the highest ccc was observed between tests done using both es antigens ( ccc = 0 . 56 ) . generally , the study results suggest that the antibody response ( detectable by the elisa ) is mainly directed against es antigens ( especially l4 ) than the crude adult worm antigen .


dallasaurus ( " dallas lizard " ) is a basal mosasauroid from the upper cretaceous of north america .

along with russellosaurus , dallasaurus is one of the two oldest mosasauroid taxa currently known from north america .

this small semi-aquatic lizard measured less than a meter in length , compared to such gigantic derived mosasaurs as tylosaurus and mosasaurus , each exceeding 14 meters .

dallasaurus

# dallasaurus has a great evolutionary importance as it is considered to be the most basal # mosasaur . dallasaurus is considered to be the most dista… | pinteres…
fossil study suggests that dallasaurus possessed movable flippers resembling limbs . this indicated that this animal possessed a semi aquatic life style . dallasaurus was thus considered to be among the earliest tetrapods .
a model of dallasaurus turneri sits in front of a mosasaur at the dallas museum of natural history .
caudal vertebrae of dallasaurus turneri ( tmm 43209 - 1 ) ; a - c – anterior . . . | download scientific diagram
turner took the remains to paleontologists at the dallas museum of natural history , but it took several years before scientists dubbed the find dallasaurus turneri .
dallasaurus has a great evolutionary importance as it is considered to be the most basal mosasaur . dallasaurus is considered to be the most distant ancestor to the fierce and sleek marine reptiles that were predators of the ocean . they were believed to be preying on the fish and other marine fauna .
turner took the remains to paleontologists at the dallas museum of natural history , but it took several years before scientists dubbed the find dallasaurus turneri .
dallasaurus retained complete limbs , hands and feet suitable for walking on land , whereas later mosasaurs evolved their limbs into flippers , the new study reports .
the ancient lizard , named dallasaurus turneri , measured three feet ( about a meter ) long and lived 92 million years ago in shallow seas that covered what is now texas .
until the discovery of dallasaurus , however , only five primitive forms with land - capable limbs were known , all of them found in the middle east and the eastern adriatic .
one aspect of polcyn and bell’s research is the revelation that dallasaurus retained complete limbs , hands and feet suitable for walking on land , whereas later mosasaurs evolved their limbs into flippers .
southern methodist university ( smu ) . 2005 . and dallas museum of natural history announce missing fossil link : dallasaurus smu news release november 16 , 2005 . retrieved may 25 , 2008 .
scientists and museum curators hope to reconstruct the more than 100 identifiable skeletal pieces that make up dallasaurus and put them on display within a few years at the dallas museum , which owns them .
polcyn and bell painstakingly pieced together an understanding of the anatomy and natural history of dallasaurus from the bones turner discovered and from some matching skeletal remains at the texas memorial museum at the university of texas in austin .
with the aid of computer science and smu ' s visualization laboratory , polcyn has been able to simulate what dallasaurus looked like , and how , based on skeletal remains , he would swim and move from land to sea . an artist has taken polcyn ' s visualization work even one step further by creating a life - sized model of dallasaurus , a work that is soon to be on display at the museum along with the computer simulation .
word of dallasaurus is now reaching the scientific community with a special issue of the netherlands journal of geosciences , featuring an article by southern methodist university paleontologist michael polcyn and gordon bell jr . of guadalupe national park in texas .
dallasaurus represents a missing link in the evolution of a group of creatures called mosasaurs , prehistoric animals that started out on land , but evolved in the seas and dominated the oceans at the same time dinosaurs ruled the land .
on wednesday , the museum unveiled a model of dallasaurus , not nearly as threatening as its oversized descendant with a slim body and only 3 feet of length . it looks somewhat like a komodo dragon , its closest living relative .
however , we are not concerned with one of the larger species . we are interested in a little three foot long specimen discovered in texas . most mosasaurs have flippers , dallasaurus turneri has limbs similar to other land lizards . from
the reptile , now known as dallasaurus turneri , is identified in a special issue of the netherlands journal of geosciences published this month . the article was written by paleontologists michael polcyn of southern methodist university and gordon bell jr . of guadalupe national park .
they describe dallasaurus , a three - foot long lizard who lived 92 million years ago in the shallow seas and shores of what was then a stretch of texas mostly under water , and also used the fossil to better understand the mosasaur family tree .
so mosasaurs were side - to - side swimmers , and one of the genera taken to represent the early stage of their evolution is dallasaurus . this was not a gigantic sea monster . dallasaurus was small – less than three feet long – and it did not have the highly - modified tail and flippers of the later , open - ocean mosasaurs . for example , the upper arm elements of dallasaurus were relatively long – preserving a more archaic anatomical construction – than the shortened upper arm elements which helped keep the flippers stable for their roles as rudders in later mosasaurs . ( similar modifications of the upper arm can be seen in whales , too . the mechanics of swimming provided the selective pressure for parts of these very difference animals to be adapted in similar ways . )
mosasaurs lived and became extinct alongside dinosaurs . later mosasaurs grew up to 45 feet in length . until the discovery of dallasaurus , however , only five primitive forms with land - capable limbs were known , all of them found in the middle east and the eastern adriatic .
full reference : g . l . bell and m . j . polcyn . 2005 . dallasaurus turneri , a new primitive mosasauroid from the middle turonian of texas and comments on the phylogeny of mosasauridae ( squamata ) . netherlands journal of geosciences 84 ( 3 ) : 177 - 194
further reading - dallasaurus turneri , a new primitive mosasauroid from the middle turonian of texas and comments on the phylogeny of the mosasauridae ( squamata ) . - netherlands journal of geoscience ( geologie en mijnbouw ) 84 ( 3 ) pp . 177 - 194 . - g . l . bell jr . & m . j . polcyn - 2005 .
the lizard is an important link in the evolution of mosasaurs , which lived in the age of dinosaurs and evolved fin - like limbs , polcyn said . dallasaurus , the name given the fossil by polcyn and bell , is unusual because it shows an earlier version of the mosasaur with tiny feet and hands . the marine animals later developed paddles .
dallasaurus was a 3 - foot lizard that lived 92 million years ago in shallow seas and shores of what is now texas . it is a missing link in the evolution of a group of creatures called mosasaurs , prehistoric animals that started out on land , but evolved in the seas and dominated the oceans at the same time dinosaurs ruled the land .
although a small number of primitive mosasaur have been known to retain land - capable limbs , they were thought to be an ancestral group separate from the later fin - bearing forms . dallasaurus represents a clear link to one lineage of the later forms and the first time researchers can clearly show mosasaurs evolved fins from limbs within the different lineages of mosasaurs .
the advanced fin - bearing mosasaurs have been grouped into three major lineages . although a small number of primitive mosasaur have been known to retain land - capable limbs , they were thought to be an ancestral group separate from the later fin - bearing forms . dallasaurus represents a clear link to one lineage of the later forms and the first time researchers can clearly show mosasaurs evolved fins from limbs within the different lineages of mosasaurs .
lizards had nearly 150 million - year - long history on land ; then in the late cretaceous , the final stage of the age of dinosaurs , one group moved into the sea and rose to the very top of the food chain ,
polcyn said wednesday .
starting out as small animals like dallasaurus , they mastered their new marine environment and rose to become the top predator in their ecosystem , the t . rex of the ocean .
however till date scientists are unable to confirm whether dallasaurus was oviparous or viviparous in nature . some schools still believe that both the processes were still missing . fossil studies indicate that the later mosasaurs were too large to return to land to conceive . but again evolution suggests that the reptiles were very quick to adapt to the physiology of live birth . fossil studies of ichthyosaurus have revealed this . the example of keichousaurus can also be mentioned regarding this context . live birth is as a phenomenon that is still observed in some lizards today . sea snakes have been reported to be conceiving by live birth .
name : dallasaurus  ( dallas lizard )  . phonetic : dal - las - ore - rus . named by : g .  l .  bell jr & m .  j .  polcyn  -  2005 . classification : chordata ,  reptilia ,  squamata ,  mosasauridae ,  mosasaurinae . species : d .  turneri ( type )  . diet : carnivore . size : up to 1 meter long . known locations : usa ,  texas ,  dallas county  -  kamp ranch limestone . time period : turonian of the cretaceous . fossil representation : 2 partial specimens ,  together represented by a partial skull and disarticulated post cranial remains .
lindgren and co - authors only looked at four representative mosasaur genera – dallasaurus , clidastes , mosasaurus , and plotosaurus – but together these creatures cover almost the entire span of mosasaur history and provide a rough idea of how the lizards changed through the cretaceous . as might be expected , earlier mosasaurs lived nearer to shore in shallow environments , whereas later , more specialized forms – such as plotosaurus – were open ocean cruisers which have been found in deposits indicating deeper environments . the rough picture is similar to that seen among fossil whales – easing into coastal environments and only later spreading far and wide . the same is true of the way the vertebrae of mosasaurs became evolutionarily modified for swimming . in early mosasaurs , the tail vertebrae were more or less the same and unspecialized . by the time of mosasaurus and plotosaurus , however , the tail had become divvied up into several different functional regions which enhanced swimming ability .
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a lizard whose fossilized bones were discovered near dallas , texas , 16 years ago is a missing link in the evolution of extinct swimming reptiles known as mosasaurs , a new study says .
is unusual , because it had tiny feet and hands suitable for walking on land . later mosasaurs developed fin - like limbs and came to dominate the seas at the time when dinosaurs ruled the land .
this study paints a much more complex picture of the evolution of [ mosasaurs ] than previously thought ,
said michael polcyn , a paleontologist at southern methodist university in dallas .
fossils in 1989 while searching through dirt turned up by bulldozers at a construction site near dallas .
remains of early mosasaurs have been difficult to find . they are only found in areas once covered by water and are quick to deteriorate .
this is the first well - preserved early mosasaur found in north america . only five primitive specimens have been found before , all of them in the middle east and along the adriatic sea .
to have this discovery in our own backyard is a terrific find ,
said anthony fiorillo , curator of the dallas museum of natural history and an smu paleontology professor .
the discovery included more than 100 identifiable skeletal pieces , composing about 80 percent of the animal .
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when amateur fossil hunter van turner discovered a small vertebra at a construction site near dallas 16 years ago , he knew the creature was unlike anything in the fossil record .
scientists now know the significance of turner ' s fossil as the origin of an extinct line of lizards with an evolutionary twist : a land - dwelling species that became fully aquatic .
the creature is just now being described publically in a special issue of the netherlands journal of geosciences by southern methodist university paleontologist michael polcyn and gordon bell jr . of guadalupe national park in texas .
this is pretty close to the beginning of the mosasaur family tree ,
says dallas museum of natural history earth sciences curator anthony fiorillo .
it is the most complete mosasaur retaining all of its limbs found in north america .
the late cretaceous period was a time of very warm temperatures and rising sea levels .
as the earth warmed and the seas rose , small land - dwelling lizards took to the oceans and developed increasing levels of seagoing capabilities , and over 30 million years , eventually evolving into the top predator of their domain before becoming extinct some 65 million years ago
polcyn said .
meanwhile van turner , the amateur , has his legacy securred in the form of the creature ' s last name , turneri .
not all major discoveries are made by highly trained paleontologists ,
said fiorillo .
the observant individual , even kids , can still make an important find .
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elon musk ' s plan to rescue trapped thai boys ? a kiddie submarine that looks like a coffin .
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parent taxon : mosasaurinae according to g . l . bell and m . j . polcyn 2005
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amateur fossil hunter van turner felt certain he had found something important during his search of earth turned up by bulldozers making way for a new subdivision in dallas county .
sixteen years later , scientists finally confirmed that turner had discovered the first well preserved early mosasaur found in north america — a prehistoric lizard that lived 92 million years ago that evolved into what some call the
t . rex of the ocean .
science marches slowly , and my biggest fear all along has been that another specimen of the same animal would be found , and it would be described , and i would lose any first claim to it ,
said turner , an internet technology manager in the central texas town of mason .
that never happened , and it kind of reassured the rarity of the animal .
before this discovery , only five primitive forms of the animal with land - capable limbs were known , and all of them were found over the last century in the middle east and the eastern adriatic , polcyn said .
this is exciting to us . it tells us the origin of mosasaurs ,
said anthony r . fiorillo , curator of earth sciences at the dallas museum of natural history , which displays a much larger reconstructed mosasaur with sharp teeth and a massive jaw .
i call him todd ,
said ross mcmillan , the ponytailed sculptor who worked with polcyn for months to painstakingly construct the lifelike piece .
when you look at his face , doesn ' t he look like a todd ?
fiorillo and polcyn said turner ' s find , made at cedar hill south of dallas , highlights the importance of contributions made by amateur fossil hunters to science .
this just goes to show you that what you want is a lot of people looking for stuff ,
turner said .
you want them to be able to recognize important finds or have the people who can do it .
right now , the skeletal pieces , comprising about 80 percent of the animal , are being kept at smu for study . a similar specimen , also acquired and donated by turner , is at the texas memorial museum at the university of texas at austin .
mosasaurs lived in the shallow seas and shores of a stretch of texas around dallas and fort worth that was mostly under water back then , polcyn said . the animals evolved into the top predator of their domain before becoming extinct 65 million years ago .
the lizard is not related to the 13 - foot oceanic crocodile discovered recently in argentina , polcyn said . the discovery of that creature , given the scientific name dakosaurus andiniensis and nicknamed
godzilla ,
was reported last week in scienceexpress , the online edition of the journal science .
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it was also seen in discovery channel ' s monsters resurrected
t - rex of the deep
.
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type specimen : tmm 43209 - 1 , a partial skeleton ( fragmentary disarticulated skull and significant portions of a postcranial skeleton ) . its type locality is cedar hill , tmm 43209 , which is in a turonian marine limestone in the kamp ranch limestone formation of texas .
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a mosasaur , cf . plotosaurus , from the upper maastrichtian quiriquina formation in central chile
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urltoken
the mosasaurs are species of aquatic reptiles that are related to lizards ( to be more precise the varanoid lizards - of which the komodo dragon is a good example ) . during the upper cretaceous they reached their peak . almost 20 genera are recognized for this period with the largest approaching 30 feet . they were ocean going carnivores that ate almost anything that swam in the sea . below are some representitive species .
i was unable to find any pictures of the fossil , but here is a reconstruction of what it is believed to look like .
afarensis is a 3 . 5 - 2 . 8 million year old hominin from the kada hadar member of the hadar formation in the middle awash , ethiopia . he is approximately 41 inches tall , weighs approximately 60 pounds and has a cranial capacity of a whopping 410 cc ( approximately ) . afarensis is currently considered to be transitional between apes and humans and displays some traits of both . since he spends a lot of time on the couch watching monster movies , some observers question whether he is an obligate biped ( although no one has observed him climbing a tree ) . he also has a blog called
loyalty to petrified opinion never broke a chain or freed a human soul . . .
it isn ' t faith that makes good science . . . it ' s curiosity
this man wishes to be accorded the same privilege as a sponge . he wishes to think !
i want you to grab life by its little bunny ears and get in its face . . .
there are bad laws and cruel laws and the people who enforce them are both bad and cruel . . .
with the first link , the chain is forged . the first speech censored , the first thought forbidden , the first freedom denied , chains us all irrevocably .
jean - luc picard , star trek : the next generation
the whole edifice of the haeckelian program became irrelevant when developmental biologists shifted their efforts to understanding mechanisms of embryonic development . it became explicitly incorrect with the demise of lamarckian heredity in the face of mendalian genetics in the early twentieth century . - rudolf raff , the shape of life : genes , development , and the evolution of animal form
these human foibles is obtained when the proponent of a questionable scientific doctrine endeavors to maintain it against all possible odds by misrepresentation , misinformation and suppression of contradictory data , and by insinuating unfairness in opponents of his views .
unique understanding and potentialities . these he owes to no one but himself , and it is to himself that he is responsible . he is not the creature of uncontrollable and undeterminable forces , but his own master . he can and must decide and manage his own destiny .
whoever fights monsters should see to it that in the process he does not become a monster . and when you look into the abyss , the abyss also looks into you .
but when a long train of abuses and usurpations , pursuing invariably the same object evinces a design to reduce them under absolute despotism , it is their right , it is their duty , to throw off such government , and to provide new guards for their future security .
but i had gradually come , by this time , to see that the old testament from its manifestly false history of the world , with the tower of babel , the rainbow at sign , etc . , etc . , and from its attributing to god the feelings of a revengeful tyrant , was no more to be trusted than the sacred books of the hindoos , or the beliefs of any barbarian .
charles darwin : the autobiography
everhart , m . j . and pearson , g . 2014 . an isolated squamate dorsal vertebra from the late cretaceous greenhorn formation of mitchell county , kansas . kansas academy of science , transactions 117 ( 3 - 4 ) : 261 - 269 . | mike everhart - urltoken
everhart , m . j . and pearson , g . 2014 . an isolated squamate dorsal vertebra from the late cretaceous greenhorn formation of mitchell county , kansas . kansas academy of science , transactions 117 ( 3 - 4 ) : 261 - 269 .
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since the early 1980’s , the story of how whales walked into the sea has become one of the most celebrated of all evolutionary transitions . pakicetus , ambulocetus , rodhocetus , and many , many more – these fossil whales with legs have beautifully demonstrated how land - dwelling mammals became adapted to life at sea . but , between 50 and 40 million years ago or so , whales were just going through a transition that many other vertebrate groups had gone through before . they were not the first vertebrates to return to the sea , nor were they the last , and a paper recently published in paleobiology by paleontologists johan lindgren , michael polcyn , and bruce young has traced the history of how a very different group of animals got their sea legs .
mosasaurs were formidable oceanic predators . take a komodo dragon , put flippers on it , and , in some cases , blow it up until it’s over 40 feet long and you’ll have some idea of what these cretaceous marine lizards were like . their fossil record – stretching over 27 million years – is also relatively well - known , and so the mosasaurs provided lindgren and colleagues with a good opportunity to see how these peculiar animals evolved .
the first thing you need to know about mosasaur evolution is that the way they swam was constrained by their anatomy . whales provide a good counterpoint . the ancestors of whales were wolf - like animals which carried their limbs under their bodies , and when they walked their spines undulated in an vertical plane . that’s why whales swim by beating their tails up and down – their mode of swimming is the product of an anatomical precondition from when their ancestors dwelt on land . the ancestors of mosasaurs , on the other flipper , moved like lizards – that is , their spines were more flexible from side to side . it’s no wonder , then , that mosasaurs swam by beating their tails back and forth , just like fish and that other group of famous marine reptiles , the ichthyosaurs .
a handful of recent discoveries have helped paleontologists better understand just how much some of the later mosasaurs became modified to life at sea . mosasaurs have traditionally been reconstructed with long , thin , lizard - like tails . they did not appear to have any specialized tail fins as seen in the shark - like ichthyosaurs . yet evidence that some mosasaurs had such structures has now been found . skeletons of plotosaurus and platecarpus appear to exhibit downward kinks in the posterior part of the tail which could have supported fleshy tail fins . ( significantly , the part of the tail which supports the tail fin kinks upwards in sharks but downwards in marine reptiles – perhaps as a result of some kind of constraint or contingency . ) these mosasaurs are be another case - with ichthyosaurs and crocodiles - of marine reptiles evolving prominent tail fins independently .
there is far more detail in the paper , of course – the entire thing runs 25 pages – but what strikes me is how very different vertebrates , even those with different anatomical constrains , eased into the seas in similar ways . early whales were up - and - down swimmers , while mosasaurs were side - to - side swimmers , yet they both started off in the shallows and underwent a sequence of modification in which their tails became specialized into specific modules suited for swimming . this is wonderful stuff – when contingency , constraint , and convergence meet together in a great transformation .
top image : a modern restoration of the mosasaur platecarpus by dmitry bogdanov . image from wikipedia .
lindgren , j . , polcyn , m . , & young , b . ( 2011 ) . landlubbers to leviathans : evolution of swimming in mosasaurine mosasaurs paleobiology , 37 ( 3 ) , 445 - 469 doi : 10 . 1666 / 09023 . 1
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dallas , texas , usa : primitive mosasaur fossil found | dear kitty . some blog
when amateur fossil finder van turner discovered a small vertebra at a construction site near dallas 16 years ago , he knew the creature was unlike anything in the fossil record .
scientists now know the significance of turner’s fossil as the origin of an extinct line of lizards with an evolutionary twist : a land - dwelling species that became fully aquatic .
“this is pretty close to the beginning of the mosasaur family tree , ” says dallas museum of natural history earth sciences curator and smu adjunct professor of paleontology anthony r . fiorillo , ph . d .
“it is the most complete mosasaur retaining all of its limbs found in north america . ”
mosasaurs , every bit as prolific , fascinating and nearly as big as some dinosaurs , are becoming more popular for paleontologists to study .
garland – digging for late cretaceous fossils in garland ? that’s exactly what more than two dozen volunteers did sunday while in the hot heat .
the dig began after a garland resident discovered a mosasaur near his home along duck creek .
the dallas paleontological society members worked 400 hours to excavate the bones of the creature .
while mosasaurs weren’t dinosaurs , they were lepidosaurs , which were reptiles with overlapping scales . the carnivorous sea reptiles swam in an ocean that scientists believe covered texas millions of years ago .
“we finally got it to a point to flip the main jacket that contains the skull , ” said rocky manning , dallas paleontological society .
“oh , it’s been interesting” said charles amyx , the man who unearthed the mosasaur bones in january from the river bottom behind his home . “i’ve been taking pictures everyday and built me a path through my yard so people can come down here and see it . ”
“it’s really very fulfilling because a lot of this wouldn’t be recovered without us , ” said pauline maullinex . “the museums don’t have the money or the personnel . ”
the coordinated effort unearthed the animal scientists estimate to be at least 40 feet long .
“this was a particularly nice mosasaur , ” manning said . “it was almost full grown . a full grown mosasaur has a jaw of almost four feet . ”
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the following articles are merged in scholar . their combined citations are counted only for the first article .
this
cited by
count includes citations to the following articles in scholar . the ones marked
museu da lourinhã ; school of earth sciences , university of bristol ; geobiotec , dept . earth sciences
j lindgren , p sjövall , rm carney , p uvdal , ja gren , g dyke , bp schultz , . . .
scientists aim to describe a single ' tree of life ' that reflects the evolutionary relationships of living things . however , evolutionary relationships are a matter of ongoing discovery , and there are different opinions about how living things should be grouped and named . eol reflects these differences by supporting several different scientific ' classifications ' . some species have been named more than once . such duplicates are listed under synonyms . eol also provides support for common names which may vary across regions as well as languages .
mosasaur is any of the various extinct , marine reptiles comprising the family mosasauridae , which were the dominant predators of the earth ' s oceans during the last 25 million years of the cretaceous period . these reptiles were typically characterized by a long , slender , serpentine body , long tails , a conically shaped head , and limbs that served as paddles , with many characterized by very large size ( everhart 2008 ) . two species , one a hainosaurus and one a mosasaurus , reached nearly 17 meters ( 56 feet ) in length . smaller species also occupied other ecological niches ( everhart 2008 ) .
fossils have been found on every continent , including antarctica , indicating a wide distribution in the oceans .
although dominant for a very long time , mosasaurs disappeared around the time when the dinosaurs disappeared , at the end of the cretaceous . however , they played an important role in the food chains of their time , and helped prepare the environment for life today . their discovery was likewise noteworthy , with the first publicized discovery of a fossil in the netherlands in 1780 preceding dinosaur fossil discoveries , drawing the attention of the world to the existence of fossilized animals , and the need to reconcile such findings with existing scientific and religious paradigms .
mosasaurs were reptiles that had a body shape similar to that of modern - day monitor lizards ( varanids ) , but were more elongated and streamlined for swimming . their long slender body shape has also been compared to that of a snake ( everhart 2008 ) . the mosasaur limb bones were reduced in length and their paddles were formed by webbing between their elongated digit - bones . the head region was conical in shape and very narrow and long in some species ( everhart 2008 ) . their tails were flattened laterally and supplied the locomotive power for swimming ( everhart 2008 ) .
all reptiles breathe air using lungs . the noticeably expanded chest region of mosasaurs suggests they may have retained two lungs , unlike snakes ( everhart 2008 ) .
mosasaurs had a double - hinged jaw and flexible skull ( much like that of a snake ) , which enabled them to gulp down their prey almost whole , a snakelike habit that has helped identify the unmasticated gut contents fossilized within mosasaur skeletons . a skeleton of tylosaurus proriger from south dakota included remains of the diving seabird hesperornis , a marine bony fish , a possible shark and another , smaller mosasaur ( clidastes ) . some showed remains of a turtle and a plesiosaur ( everhart 2005a ) . mosasaur bones have also been found with shark teeth embedded in them .
mosasaurs were powerful swimmers , although their body shape suggests they were inefficient for high - speed swimming compared to the rapidly swimming ichthyosaurs and plesiosurs , other marine reptiles whose age of dominance preceded that of mosasaurs . the method of locomotion of mosasaurs may have been similar to that used by the conger eel or sea snakes today . the animal may have lurked and pounced rapidly and powerfully on passing prey , rather than hunting for it ( everhart 2005a ) .
mosasaurs were well - adapted to living in the warm , shallow epicontinental seas prevalent during the late cretaceous period . mosasaurs were so well adapted to this environment that some fossils show evidence that they gave birth to live young , rather than return to the shore to lay eggs , as sea turtles do ( everhart 2005a ) . for example , a fossil of plioplatecarpus had the remains of several unborn in her abdomen ( everhart 2005a ) .
the smallest - known mosasaur was carinodens belgicus , which was about 3 . 0 to 3 . 5 meters long and probably lived in shallow waters near shore , cracking mollusks and sea urchins with its bulbous teeth . larger mosasaurs were more typical : mosasaurs ranged in size up to 17 meters . hainosaurus holds the record for longest mosasaur , at 17 . 5 meters .
the name mosasaur comes from the latin mosa meaning the
meuse river
in the netherlands , and greek sauros meaning
lizard .
the meuse river was the locality were the first mosasaur was found ( everhart 2005a ) .
sea levels were high during the cretaceous , which is expected to correlate with marine transgressions in many parts of the world and caused a great inland seaway in what is now north america .
mosasaur fossils have been found in the netherlands , in sweden , in africa , in australia , in new zealand and on vega island , off the coast of antarctica . in canada and the united states , complete or partial specimens have been found in alabama , mississippi , tennessee , and georgia and in almost all the states covered by the seaway : texas , southwest arkansas , new mexico , kansas ( everhart 2005b ) , colorado , nebraska , the dakotas , montana , and the pierre shale and fox hills formations of north dakota ( getman 1994 ) . mosasaurs are also known from mexico , peru , denmark , and california .
many of the
dinosaur
remains found on new zealand —a volcanic island arc that has never been part of a continent—are actually mosasaurs and plesiosaurs , another group of mesozoic predatory marine reptiles .
the first publicized discovery of a fossil mosasaur preceded any dinosaur fossil discoveries and drew the age of enlightenment ' s attention to the existence of fossilized animals . the specimen was discovered in 1780 by quarry - workers in a subterranean gallery of a limestone quarry in the vicinity of maastricht in the netherlands . maastricht is situated on both sides of the meuse river . the quarry workers quickly alerted doctor c . k . hoffman , a surgeon and fossil - hunter in the dutch city of maastricht , although rights of ownership lay with a canon of maastricht cathedral , as owner of the overlying land .
dr . hoffman ' s correspondence among men of science made the find famous . when the revolutionary forces occupied maastricht , the carefully - hidden fossil was uncovered , betrayed , it is said , by a case of wine , and transported to paris , where georges cuvier was able to describe it for science , although le grand animal fossile de maastricht was not actually described as a mosasaur (
meuse reptile
) until 1822 and not given its official name , mosasaurus hoffmanni , until 1829 . several sets of mosasaur remains , that had been discovered earlier at maastricht but were not identified as mosasaurs until the nineteenth century , have been on display in the teylers museum , haarlem , since about 1770 .
the maastricht limestone beds were rendered so famous by the mosasaur discovery that they have given their name to the final six - million - year epoch of the cretaceous , the maastrichtian .
based on features such as the double row of pterygoid (
flanged
) teeth on the palate , the double - hinged jaw , modified / reduced limbs and probable methods of locomotion , many researchers believe that snakes and mosasaurs have had a common ancestor . this theory was first suggested in 1869 , by edward drinker cope , who coined the term
pythonomorpha
to include them . the idea lay dormant for more than a century , before being revived in the 1990s ( everhart 2005a ; palaeos 2006 ) . there is support for the view that these ferocious marine predators are close relatives of snakes based on cladistic analysis of symptomatic similarities in jaw and skull anatomies ( lee 1997 ) .
during the last 20 million years of the cretaceous ( turonian - maastrichtian ) , with the extinction of the ichthyosaurs and pliosaurs , mosasaurs became the dominant marine predators . the ichthyosaurs declined greatly in the early cretaceous for unknown reasons and are thought to have been extinct by the time of the earliest mosasaurs ( everhart 2005a ) .
everhart , m . j . 2005a . mosasaurs : last of the great marine reptiles oceans of kansas . originally published as everhart , m . j . 2000 . mosasaurs : last of the great marine reptiles . prehistoric times . 44 : 29 - 31 . retrieved may 25 , 2008 .
everhart , m . j . 2005b . enter the mosasaurs . chapter 9 in m . j . everhart , oceans of kansas : a natural history of the western interior sea . bloomington , in : indiana university press . isbn 0253345472 .
everhart , m . j . 2008 . rapid evolution , diversification , and distribution of mosasaurs ( reptilia ; squamata ) prior to the k - t boundary tate 2005 11th annual symposium in paleontology and geology . casper , wy , p . 16 - 27 . retrieved may 25 , 2008 .
getman , m . r . c . 1994 . occurrences of mosasaur and other reptilian fossil remains from the fox hills formation ( maastrichtian : late cretaceous ) of north dakota . st . lawrence university press .
lee , m . s . y . 1997 . the phylogeny of varanoid lizards and the affinities of snakes philosophical transactions of the royal society london 352 : 53 - 91 . retrieved may 25 , 2008 .
mike everhart and david lewis ,
mesozoic marine monsters of the mangahouanga
new zealand fossil fauna .
mike everhart ,
a day in the life of a mosasaur
life in the sea of kansas , illus . by carl buell .
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