This articlerelies largely or entirely on asingle source.(February 2017) |
Polyclonoolithusis anoogenusoffossildinosaur egg.It is from theEarly CretaceousofGansu,China. They have distinctive, branching eggshell units, which may represent the original form ofspheroolithids.[1]
| Polyclonoolithus Temporal range:
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|---|---|
Egg fossil classification
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| Basic shell type: | †Dinosauroid-spherulitic |
| Oofamily: | †Polyclonoolithidae |
| Oogenus: | †Polyclonoolithus Xieet al.,2016 |
| Oospecies | |
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Distribution
editPolyclonoolithusis known exclusively fromYangjiagou,a small town inGansu.The only known fossil specimen is from theLower CretaceousHekou Group,part of the larger Lanzhou-Minhe Basin.[1]
Discovery
editDinosaurbody fossilsandichnitesare common at the Hekou Group, but fossilized eggs are rare.[1]The first fossil eggs found there were collected byChinese Academy of Geological SciencesinZhongpuin2009,but were never formally described. In2012,a team of paleontologists from theGansu Geological Museum,theInstitute of Vertebrate Paleontology and Paleoanthropologyand theInstitute of Geologyonce again discovered fossil eggs in the Lanzhou-Minhe Basin. In2016,their discovery was described as a new oogenus and oospecies,Polyclonoolithus yangjiagouensis,by Chinese paleontologists Xie Jun-Fang, Zhang Shu-Kang, Jin Xing-Sheng, Li Da-Qing, and Zhou Ling-Qi.[1]
Description
editPolyclonoolithusis only known from one specimen: ZMNH M1849, an incomplete egg (made up of several fragments) housed in theZhejiang Museum of Natural History.Due to the poor preservation, the size and shape of a complete egg are unknown, butPolyclonoolithuswas likely less than 10 centimetres (3.9 in) in diameter. The eggshell ranges from 1.84 to 2.05 millimetres (0.072 to 0.081 in) in thickness. The cone layer has radiating structure and makes up roughly 1/7 the total width of the eggshell.[1]
Polyclonoolithusis distinctive for having branching shell units, with irregular pore canals between them. The branches of the eggshell units fuse together towards the outer surface of the shell.[1]
Parataxonomy
editPolyclonoolithusis classified inits ownoofamily,Polyclonoolithidae.Its branching eggshell units set it apart from all other oofamilies, except forDendroolithidae,Dictyoolithidae,andSimilifaveoloolithidae.It lacks the reticulate structure seen in dictyoolithids, and unlike similifaveoloolithids and dendroolithids, the eggshell units vary in thickness. It furthermore differs from dendroolithids in that the eggshell units are not totally fused together at the outer surface of the eggshell, however this could only be due to erosion.[1]
There is also some similarity between the branching eggshell units ofPolyclonoolithusto the superimposed eggshell units found inSpheroolithidae,leading to the hypothesis by Xieet al.that the shell units of polyclonoolithids may represent a primitive form of those found in spheroolithids.[1]
Polyclonoolithuscontains only a single oospecies:P. yangjiagouensis.[1]