Project 2791: K. T. Smith, B.-A. S. Bhullar, G. Koehler, J. Habersetzer. 2018. The only known jawed vertebrate with four eyes and the Bauplan of the pineal complex. Current Biology. 28 (7):1101-1107.
Specimen: † Saniwa ensidens (YPM:613)
View: medial


The pineal and parapineal organs are dorsal outpocketings of the vertebrate
diencephalon that play key roles in orientation and in circadian and annual cycles. Lampreys are four-eyed in that both pineal and parapineal form eyelike photosensory structures, but the pineal is the dominant or sole median photosensory structure in most lower vertebrate clades. The pineal complex has been thought to evolve in a single direction by losing photosensory and augmenting secretory function in the transitions from three-eyed lower vertebrates to two-eyed mammals and archosaurs. Yet the widely accepted elaboration of the parapineal instead of the pineal as the primary median photosensory organ in Lepidosauria (lizards, snakes and tuataras) hints at a more complex evolutionary history. Here we present evidence that a fourth eye re-evolved from the pineal organ at least once within vertebrates, specifically in an extinct monitor lizard, Saniwa ensidens, in which pineal and parapineal eyes were present simultaneously. The tandem midline location of these structures confirms in a striking fashion the proposed homology of the parietal eye with the parapineal organ and refutes the classical model of pineal bilaterality. It furthermore raises questions about the evolution and functional interpretation of the median photosensory organ in other tetrapod clades.

Read the article »

Article DOI: 10.1016/j.cub.2018.02.021

Project DOI: 10.7934/P2791,
This project contains
  • 4 Media
  • 1 Document
  • 1 Taxon
  • 5 Specimens
Total size of project's media files: 4.22M

Download Project SDD File
Currently Viewing:
MorphoBank Project 2791

    This research
    supported by

    Authors' Institutions

    • Yale University

    • Senckenberg Research Institute (Forschungsinstitut Senckenberg)


    member name taxa specimens media
    Krister Smith
    Project Administrator

    Project has no matrices defined.

    Project views

    type number of views Individual items viewed (where applicable)
    Total project views8046
    Project overview1049
    Media views2808Media search (1555 views); M475757 (255 views); M475748 (438 views); M475759 (281 views); M466455 (1 view); M466317 (278 views);
    Specimen list1648
    Taxon list599
    Documents list495
    Views for media list1066

    Project downloads

    type number of downloads Individual items downloaded (where applicable)
    Total downloads from project189
    Media downloads12M475748 (2 downloads); M475759 (6 downloads); M466317 (2 downloads); M475757 (2 downloads);
    Project downloads177