| Suchoolithus | |
|---|---|
 | |
| Holotype clutch, containing 13 eggs | |
Egg fossil classification | |
| Basic shell type: | †Crocodiloid |
| Oofamily: | †Krokolithidae |
| Oogenus: | †Suchoolithus Russoet al.,2017 |
| Oospecies | |
Suchoolithus is anoogenus (fossil egg genus) ofcrocodylomorph eggs from the lateJurassic ofPortugal. They are notable for their small size, and for being among the oldest known crocodylomorph eggs.
Suchoolithus is known from a single, well-preservedegg clutch of 13 eggs. The eggs have a blunt, ellipsoid shape, and are quite small (measuring only 42 mm (1.7 in) long by 26 mm (1.0 in) across). All but two of the eggs are arranged horizontally in the clutch.[1] The eggshell is only 163 μm thick,[2] and is sculpted with tiny, irregular bumps on its outer surface. Like other crocodylian eggs, its shell is composed of thousands of tiny calcium carbonate crystal units; inS. portucalensis, these eggshell units are trapezoidal, tightly packed, and wider than they are tall. Russoet al. 2017 did not observe any pores openings on the eggshell's surface,[1] though a possible pore canal was observed in one section of the shell.[3]
Fossil crocodylian eggs are generally rare, though they have been discovered worldwide (exceptingAntarctica andAustralia). In 2008, the Portuguese paleontologistOctávio Mateus discovered a fossilizedegg clutch at theLourinhã Formation of Portugal that would later becomeholotype ofSuchoolithus.[1] These eggs were first described in 2014 by Russo, Mateus, Balbino, and Marzola, who at the time tentatively referred them toKrokolithes, but noted their similarities to the KrokolithidBauruoolithus.[2] In 2016, João Russo, working withOctávio Mateus as his supervisor and Balbino as co-supervisor, completed his Master's Thesis atFaculdade de Ciências e Tecnologia da Universidade Nova de Lisboa, in which he named the oogenus and oospeciesSuchoolithus portucalensis (meaning "crocodile egg stone from Portugal").[3] The next year, Russo, Mateus, Marzola, and Balbino published the description ofSuchoolithus inPLOS One.[1]
Suchoolithus is known exclusively from the upperTithonian of the Late JurassicLourinhã Formation of Portugal, making it (alongsideKrokolithes dinophilus) the oldest known crocodylomorph egg.[1] This formation, representing the deposits ofriver deltas andalluvial fans, has similar fauna and flora to the contemporaneousMorrison Formation in the United States and theTendaguru Formation in Tanzania.[4] Several types of crocodylomorphs are known from the late Jurassic of Portugal, but given the small size of the eggs, it is most likely thatSuchoolithus were laid by one of the smaller species (perhaps less than 1 m (3.3 ft) long), such asBernissartia,cf.Alligatorium,Lisboasaurus,Lusitanisuchus, orTheriosuchus.[1]