Macroelongatoolithus

Macroelongatoolithus is an oogenus of large, fossil theropod eggs (probably representing a giant oviraptorid). They are known from Asia and from North America. Fossil Macroelongatoolithus eggs have been found in the United States, China, and South Korea, ranging in age from Early Cretaceous to Maastrichtian. More specifically, it is known from the Cedar Mountain, Dakota, and Kelvin Formations of Utah, from the Wayan Formation of Idaho, the Blackleaf Formation of Montana, the Thomas Fork Formation of Wyoming, from the Liangtoutang and Chichengshan Formations in Tiantai County, Zhejiang Province, from the Gaogou, Sigou, Majiacun, and Zoumagang Formations in Henan Province, China, and from the Goseong Formation near Tongyeong, South Korea. Macrooelongatoolithus eggs are most notable for their large size. They are at least 34 centimetres (13 in) long by 11 centimetres (4.3 in), but the largest specimens are over 60 centimetres (24 in) long. They are also very elongated, usually roughly three times longer than they are wide. They are often found in large clutches of up to 26 eggs, with the eggs forming a ring 2–3.3 metres (6.6–10.8 ft) in diameter. The shell is typically between 1.38 mm and 4.75 mm thick. Like other elongatoolithids, Macroelongatoolithus's eggshell is divided up into two structural layers, and the outer layer (called the continuous layer) is not divided up into distinct shell units, unlike other oofamilies. In Macroelongatoolithus, the boundary between the continuous layer and the mammillary layer (the inner layer of the eggshell, also called the cone layer) is wavy, but clearly defined. The ratio of the thickness of the two layers varies from 2:1 to 8:1. The surface ornamentation of the eggshells is variable, even on a single egg. It is usually lineartuberculate (nodes forming linear ridges), ramotuberculate (nodes forming irregular, meandering chains), or dispersituberculate (scattered nodes). Macroelongatoolithus specimens are extremely variable in size, shape, and microstructure, even in eggs laid by a single individual. For example, within a single clutch, the egg lengths can vary by several centimeters. The high amount of variability is probably due to their large size. Historically, several oospecies have been assigned to Macroelongatoolithus, however they are all now considered to be a single oospecies: M. carlylensis. 'Oolithes' carlylensis was described in 1970 by James Jenson. In 1998, O. carlylensis was moved to a new oogenus, Boletuoolithus, which was then classified as a Spheroolithid. Macroelongatoolithus was first described in 1995 by Li et al., with a single oospecies: M. xixiaensis. It was classified in the oofamily Elongatoolithidae. Later in the same year, Wang and Zhou described Longiteresoolithus xixiaensis, which they placed into a new oofamily, Macroelongatoolithidae. These three oospecies are now considered synonymous, and generally classified in Elongatoolithidae. Since M. carlylensis was named first, it has priority, but the name was corrected to M. carlylei to follow ICZN provisions.