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Avian egg from Lower Cretaceous of Zhejiang Province, China

Ben Creisler

A new paper:

Daniel R. Lawver, Xingsheng Jin, Frankie D. Jackson & Qiongying Wang (2016)
An avian egg from the Lower Cretaceous (Albian) Liangtoutang Formation
of Zhejiang Province, China
Journal of Vertebrate Paleontology (advance online publication)
http: // www.tandfonline.com/doi/full/10.1080/02724634.2016.1100631

Mesozoic avian eggs are rare, especially from the mid-Cretaceous
basins of Zhejiang Province, China. Here we report an avian egg from
the Lower Cretaceous (Albian) Liangtoutang Formation. The specimen
(JYM F0033) measures 50 mm × 32 mm and the 166-µm-thick eggshell
consists of three structural layers of calcite. The mammillary layer
(ML) and overlying continuous layer (CL) each measure approximately 46
µm, whereas the outermost, external layer (EL) measures 74 µm. Ratios
of these layers are ML:CL:EL = 1:1:1.6. An external layer that exceeds
the thickness of the continuous layer represents an autapomorphy of
this new egg type, which we herein establish as Pachycorioolithus
jinyunensis oogen. et oosp. nov. within Pachycorioolithidae oofam.
nov. Documentation of eggshell features and their first occurrence in
the fossil record provides phylogenetically important information that
may potentially aid in clarifying the evolution of avian reproduction
and biology.

http: //