EDIT

         <dynamic

               class="eu.etaxonomy.taxeditor.view.CdmViewerContextMenu"

               id="eu.etaxonomy.taxeditor.editor.descriptive.cdmViewerContextMenu">

         </dynamic>

         <separator

               name="eu.etaxonomy.taxeditor.editor.separator1">

         </separator>

         <separator

               name="eu.etaxonomy.taxeditor.taxonDescriptionEditor.separator3"

               visible="true">

         </separator>

         <menu

               label="%menu.label.1">

            <dynamic

                  class="eu.etaxonomy.taxeditor.editor.view.descriptive.handler.DynamicFeatureMenu"

                  id="eu.etaxonomy.taxeditor.dynamicFeatureMenu">

            </dynamic>

            <visibleWhen

                  checkEnabled="true">

               <or>

                  <reference

                        definitionId="isDescription">

                  </reference>

                  <reference

                        definitionId="isDescriptionElement">

                  </reference>

                  <reference

                        definitionId="isFeatureNodeContainer">

                  </reference>

               </or>

            </visibleWhen>

         </menu>

      <handler

            class="eu.etaxonomy.taxeditor.editor.view.derivate.handler.OpenDerivativeEditorForDescriptionElement"

            commandId="eu.etaxonomy.taxeditor.editor.openSpecimenEditor">

         <activeWhen>

            <with

                  variable="activePartId">

               <equals

                     value="eu.etaxonomy.taxeditor.editor.view.descriptive">

               </equals>

            </with>

         </activeWhen>

      </handler>

         <commandParameter

               id="eu.etaxonomy.taxeditor.editor.openSpecimenEditor.uuid"

               name="Specimen Uuids"

               optional="true"

               typeId="eu.etaxonomy.taxeditor.uuidParameterType">

         </commandParameter>

      <viewCommandMapping

            commandId="eu.etaxonomy.taxeditor.editor.openSpecimenEditor"

            selection="eu.etaxonomy.cdm.model.description.IndividualsAssociation"

            viewerName="Derivative Editor">

      </viewCommandMapping>

package eu.etaxonomy.taxeditor.editor.view.derivate.handler;

import java.util.Collections;

import java.util.UUID;

import org.eclipse.core.commands.ExecutionEvent;

import org.eclipse.ui.PartInitException;

import eu.etaxonomy.cdm.api.service.IDescriptionService;

import eu.etaxonomy.cdm.model.description.DescriptionElementBase;

import eu.etaxonomy.cdm.model.description.IndividualsAssociation;

import eu.etaxonomy.cdm.model.occurrence.SpecimenOrObservationBase;

import eu.etaxonomy.taxeditor.editor.EditorUtil;

import eu.etaxonomy.taxeditor.editor.handler.OpenDerivateViewHandler;

import eu.etaxonomy.taxeditor.editor.view.derivate.DerivateViewEditorInput;

import eu.etaxonomy.taxeditor.handler.defaultHandler.DefaultOpenHandlerBase;

import eu.etaxonomy.taxeditor.model.MessagingUtils;

import eu.etaxonomy.taxeditor.store.CdmStore;

public class OpenDerivativeEditorForDescriptionElement extends DefaultOpenHandlerBase<IndividualsAssociation> {

    @Override

    protected IndividualsAssociation getEntity(UUID uuid) {

        DescriptionElementBase descriptionElement = CdmStore.getService(IDescriptionService.class).loadDescriptionElement(uuid, null);

        if(descriptionElement.isInstanceOf(IndividualsAssociation.class)){

            return (IndividualsAssociation) descriptionElement;

        }

        return null;

    }

    @Override

    protected void open(ExecutionEvent event, IndividualsAssociation entity) {

        SpecimenOrObservationBase associatedSpecimenOrObservation = entity.getAssociatedSpecimenOrObservation();

        if(associatedSpecimenOrObservation!=null){

            UUID specimenUuid = associatedSpecimenOrObservation.getUuid();

            try {

                EditorUtil.open(new DerivateViewEditorInput(Collections.singletonList(specimenUuid)));

            } catch (PartInitException e) {

                MessagingUtils.error(OpenDerivateViewHandler.class, "Derivative Editor could not be opened", e);

            }

        }

    }

}