TY - JOUR
T1 - Histology of the preparietal
T2 - a neomorphic cranial element in dicynodont therapsids
AU - Marilao, Lianna M.
AU - Kulik, Zoe T.
AU - Sidor, Christian A.
N1 - Funding Information:
for the analysis of NHCC LB840 and support of L.M.M. was provided by NSF EAR-137569 (to C.A.S.). Field work in Zambia in 2018 was supported by NGS-158R-18 (to B. Peecook) and NSF EAR-137569 (to C.A.S.), and we thank team members J. Museba, B. Peecook, S. Tolan, P. Viglietti, and M. Whitney for their assistance and companionship in the field. We gratefully acknowledge the NHCC for granting permits since 2009. Funding for the collection and analysis of IVPP V 22763 as well as support of Z.T.K. was provided by NSF EAR-1713787 (to C.A.S.). We thank J. Liu, K. Angielczyk, and W. Yang, as well as the rest of the 2019 field team, for assistance in Xinjiang. We thank C. Sullivan, J. Liu, and K. Angielczyk for comparative supplementary images and data, as well as P. Viglietti, C. Kammerer, and an anonymous reviewer for their helpful suggestions on the manuscript.
Funding Information:
Funding for the analysis of NHCC LB840 and support of L.M.M. was provided by NSF EAR-137569 (to C.A.S.). Field work in Zambia in 2018 was supported by NGS-158R-18 (to B. Peecook) and NSF EAR-137569 (to C.A.S.), and we thank team members J. Museba, B. Peecook, S. Tolan, P. Viglietti, and M. Whitney for their assistance and companionship in the field. We gratefully acknowledge the NHCC for granting permits since 2009. Funding for the collection and analysis of IVPP V 22763 as well as support of Z.T.K. was provided by NSF EAR-1713787 (to C.A.S.). We thank J. Liu, K. Angielczyk, and W. Yang, as well as the rest of the 2019 field team, for assistance in Xinjiang. We thank C. Sullivan, J. Liu, and K. Angielczyk for comparative supplementary images and data, as well as P. Viglietti, C. Kammerer, and an anonymous reviewer for their helpful suggestions on the manuscript.
Publisher Copyright:
© 2020, by the Society of Vertebrate Paleontology.
PY - 2020
Y1 - 2020
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=85088539980&partnerID=8YFLogxK
U2 - 10.1080/02724634.2020.1770775
DO - 10.1080/02724634.2020.1770775
M3 - Article
AN - SCOPUS:85088539980
SN - 0272-4634
VL - 40
JO - Journal of Vertebrate Paleontology
JF - Journal of Vertebrate Paleontology
IS - 2
M1 - e1770775
ER -