Alectrosaurus

Abstract: The giant fossil eggs,Macroelongatoolithus xixiaensis,laid by huge tyrannosaurs were recently discovered from Late Cretaceous Chichengshan Formation(approximately 92Ma) in Tiantai County of Zhejiang Province,though some of their fossil skull or skeleton has not yet been found in eastern China so far.Based on the taxonomy of tyrannosaurs at present,the taxonomy of their fossil egg can be proposed accordingly,i.e.Suborder: Theropoda Marsh,1881——Elongatoolithineae oosubord.nov.Superfamily: Tyrannosauroidea Osborn,1905——Macroelongatoolithoidea oosuperfam.nov.Family: Tyrannosauridae Osborn,1905——Macroelongatoolithidae oofam.nov.Elongatoolithineae oosubord.nov.Diagnosis——elliptic elongated eggs were laid in pairs and arranged abreast around a circle in a nest.Horizon——The Triassic to Cretaceous Macroelongatoolithoidea oosuperfam.nov.Diagnosis——giant flat and elliptic elongated eggs were laid in pairs and arranged abreast around a circle in a nest.Horizon——Cretaceous Macroelongatoolithidae oofam.nov.Diagnosis and Horizon——As for oosuperfamily.Oogenus Macroelongatoolithus Li et al.,1995 Type oospecies Macroelongatoolithus xixiaensis Li et al.,1995 Synonymy.2000 Macroelongatoolithus zhangi Fang et al.Which is the tyrannosaur laid the giant Macroelongatoolithus xixiaensis? Of excavated fossil tyrannosaurs from eastern Asia,an adult Guanlong and an adult Dilong were apparently too small,only 3m and 1.6m long respectively,to lay giant eggs,and it was of old age,approximately 160Ma and 130Ma respectively.An adult Alectrosaurus and an adult Alioramus were 5 m~6m long respectively,and perhaps not huge enough to lay such enormous eggs.No other than a Tarbosaurus,which an adult was more than 10 m long,was an imaginabale suspect laid these giant eggs.However all known Tarbosaurus were from terminal Cretaceous Maastrichtian(71Ma~65Ma),and were not identical with Macroelongatoolithus from early Late Cretaceous Turonian(approximately 92Ma).It is possible that the period of Tarbosaurus perhaps was extended to 92Ma,or other unknown huge tyrannosaurs laid these giant eggs in 92Ma.The binate Macroelongatoolithus xixiaensis presented in a nest indicated that the adult female tyrannosaur produced two eggs once in her nest as other theropod,i.e.they had a pair of functional oviducts.All of Macroelongatoolithus xixiaensis,furthermore,were flat oval and suggested that their eggshell were flexible as that of some modern reptiles.These eggs would be transmogrified by gravity,especially giant eggs as Macroelongatoolithus xixiaensis.