1  definition  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Vertebra  \Ver"te*bra\,  n.;  pl  {Vertebr[ae]}.  [L.  vertebra,  fr 
  vertere  to  turn,  change.  See  {Verse}.] 
  1.  (Anat.)  One  of  the  serial  segments  of  the  spinal  column. 
 
  Note:  In  many  fishes  the  vertebr[ae]  are  simple  cartilaginous 
  disks  or  short  cylinders,  but  in  the  higher  vertebrates 
  they  are  composed  of  many  parts  and  the  vertebr[ae]  in 
  different  portions  of  the  same  column  vary  very 
  greatly.  A  well-developed  vertebra  usually  consists  of 
  a  more  or  less  cylindrical  and  solid  body,  or  centrum, 
  which  is  surmounted  dorsally  by  an  arch,  leaving  an 
  opening  which  forms  a  part  of  the  canal  containing  the 
  spinal  cord.  From  this  dorsal,  or  neural,  arch  spring 
  various  processes,  or  apophyses,  which  have  received 
  special  names:  a  dorsal,  or  neural,  spine,  spinous 
  process,  or  neurapophysis,  on  the  middle  of  the  arch; 
  two  anterior  and  two  posterior  articular  processes,  or 
  zygapophyses;  and  one  or  two  transverse  processes  on 
  each  side  In  those  vertebr[ae]  which  bear 
  well-developed  ribs,  a  tubercle  near  the  end  of  the  rib 
  articulates  at  a  tubercular  facet  on  the  transverse 
  process  (diapophysis),  while  the  end  or  head,  of  the 
  rib  articulates  at  a  more  ventral  capitular  facet  which 
  is  sometimes  developed  into  a  second  or  ventral, 
  transverse  process  (parapophysis).  In  vertebrates  with 
  well-developed  hind  limbs,  the  spinal  column  is  divided 
  into  five  regions  in  each  of  which  the  vertebr[ae]  are 
  specially  designated:  those  vertebr[ae]  in  front  of  or 
  anterior  to  the  first  vertebra  which  bears  ribs 
  connected  with  the  sternum  are  cervical;  all  those 
  which  bear  ribs  and  are  back  of  the  cervicals  are 
  dorsal;  the  one  or  more  directly  supporting  the  pelvis 
  are  sacral  and  form  the  sacrum;  those  between  the 
  sacral  and  dorsal  are  lumbar;  and  all  those  back  of  the 
  sacral  are  caudal,  or  coccygeal.  In  man  there  are  seven 
  cervical  vertebr[ae],  twelve  dorsal,  five  lumbar,  five 
  sacral,  and  usually  four  but  sometimes  five  and  rarely 
  three  coccygeal. 
 
  2.  (Zo["o]l.)  One  of  the  central  ossicles  in  each  joint  of 
  the  arms  of  an  ophiuran. 

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