Call Controller by Ajax in Magento Admin 1.9

<form action=" id="mass_forms">
<input name="form_key" type="hidden" value="<?php echo Mage::getSingleton('core/session')->getFormKey() ?>" />
<select id="mainStatus" onChange="getSubStatus()">
<option value=''>Select Status</option>
<?php
foreach($item_Status as $itemstatus){?>
<option value='<?php echo $itemstatus['id'] ?>'><?php echo $itemstatus['value'] ?></option>
<?php }
?>
</select>
</form>

////////////////////////////////////////////////////////////////////////////////
Script:
<script>



function getSubStatus(){
var posdata = jQuery("#mass_forms").serializeArray();
var url =  "<?php echo $this->getUrl('marketplaceadmin/adminhtml_orderview/getsubstaus');?>";
jQuery.ajax({
type: "POST",
url: url,
datatype: "text",
data: posdata,
success: function(data)
{

alert(data);
}
});


}

</script>
//////////////////////////////////////////////////////////////////////////
controller:
public function getsubstausAction(){
// $statusId=$this->getRequest()->getParam("statusId");
echo 'ankur';
}