EDIT

Taxon synonymy contains a homotypic-synonymy-group div even if this is empty.

This causes an extra separator line (border-bottom) to be shown and adds extra space.

<div class="homotypic-synonymy-group">
  <ul class="homotypicSynonyms">
  </ul>
  <ul class="footnotes">
    <li class="footnotes footnotes-taxon_page_synonymy-annotations ">
    </li>
    <li class="footnotes footnotes-taxon_page_synonymy ">
    </li>
  </ul>
</div>