Project 3636: L. M. Marilao, Z. T. Kulik, C. A. Sidor. 2020. Histology of the preparietal: a neomorphic cranial element in dicynodont therapsids. Journal of Vertebrate Paleontology. epub ahead of print:e1770775.
Specimen: † Diictodon (NHCC LB840)
View: Coronal thin section of skull


The preparietal, a neomorphic midline ossification on the skull roof, is thought to have evolved three times in therapsids, but its development and homology remain poorly understood. Here, we provide preliminary data on the histology of this element in specimens referred to Diictodon feliceps and an indeterminate species of Lystrosaurus. The preparietal has previously been noted to vary substantially in its shape on the dorsal surface of the skull in several dicynodonts, and we found similar variation in thin section. In Diictodon, the preparietal forms a prong that embeds itself entirely within the frontals and shows evidence of a midline suture anteriorly. The sectioned specimen of Lystrosaurus shows histological evidence of immaturity and features a well-defined midline suture at the posterior end of the preparietal, although an anterior prong was not present. In both taxa, the anteroventral portion of the preparietal forms a strongly interdigitating suture with the underlying frontals and parietals. More posteriorly, the preparietal is composed of fibrolamellar bone suggestive of rapid posteroventral growth. In large dicynodont species, the dorsal expression of the preparietal appears to show negative allometry compared with other cranial roofing elements during ontogeny, but the significance of this geometry is unclear. In addition, histological work is needed on the preparietal in gorgonopsians and biarmosuchians to determine whether the features characterizing dicynodonts are also seen in the other two groups of therapsids that evolved a preparietal. The therapsid preparietal provides a rare opportunity to study the development and evolution of a neomorphic cranial element in the vertebrate fossil record.

Read the article »

Article DOI: 10.1080/02724634.2020.1770775

Project DOI: 10.7934/P3636,
This project contains
  • 18 Media
  • 2 Taxa
  • 2 Specimens
Total size of project's media files: 548.57M

Download Project SDD File
Currently Viewing:
MorphoBank Project 3636
  • Creation Date:
    12 February 2020
  • Publication Date:
    24 July 2020
  • Project views: 1876

    This research
    supported by

    Authors' Institutions

    • University of Washington


    member name taxa specimens media
    Lianna Marilao
    Project Administrator
    Last logged in 07/24/20
    Zoe Kulik
    Full membership
    Last logged in 02/13/20
    Christian Sidor
    Full membership
    Last logged in 02/12/20
    Christian Sidor
    Full membership
    Last logged in 07/24/20

    Project has no matrices defined.

    Project views

    type number of views Individual items viewed (where applicable)
    Total project views1876
    Project overview173
    Media views1151Media search (300 views); M685218 (47 views); M685219 (47 views); M685220 (43 views); M685221 (49 views); M685222 (51 views); M685223 (45 views); M685224 (43 views); M685225 (44 views); M685226 (49 views); M685227 (50 views); M685228 (50 views); M685229 (45 views); M685230 (47 views); M685231 (46 views); M685232 (53 views); M685233 (50 views); M685234 (46 views); M685235 (46 views);
    Specimen list214
    Taxon list182
    Views for media list96

    Project downloads

    type number of downloads Individual items downloaded (where applicable)
    Total downloads from project34
    Project downloads34