a parietal foramen located near of the fronto-parietal suture, a triangular surface of the parietal with two medial depressions and 22 caudal vertebrae. E. coellensis was larger, with its type specimen, IGM p 881237, measuring long and weighing . This specimen had a long skull and lacked a complete tail. Still, it is remarkable for having remains of soft tissue in the ear region, the neck, thoracic and the abdominal region. Under the pygal vertebrae and the seventeenth dorsal vertebra there is a series of 20 small vertebrae centra and a flattened bone, that together measure in length. It have features of the mosasauroids, with three vertebrae with haemal arches and procoelic centra, that suggest the possibility that these small bones belong to an embryo of this species, although the lack of diagnostic fossils like the skull or teeth prevents a complete identification. In any case, it will be consequent with the ovoviviparism previously reported in mosasauroids like Carsosaurus. Classification Like many mosasaurs, this genus has a complicated taxonomic history. The type specimen (UPI R 163, Uppsala University Palaeontological Institute, Uppsala, Sweden), a nearly complete skeleton, was originally referred to the genus Clidastes by Wiman and then to Halisaurus by Russell. Hence, Clidastes sternbergii became Halisaurus sternbergii. Although some agreed with this generic attribution, other paleontologists suggested that while H. sternbergii did not belong to Clidastes, its designation under Halisaurus is questionable; Lingham-Soliar (1996) referred H. sternbergii to C. sternbergii again, but this has found no acceptance in other researchers. In 2005, Halisaurus sternbergii was reassigned to its own genus, Eonatator by Nathalie Bardet and colleagues along with the description of Halisaurus arambourgi and the creation of the subfamily Halisaurinae. In the same year, Lindgren and Siverson suggested that Eonatator is an invalid junior synonym and should be classified as H. sternbergii, but this has found no acceptance in other researchers who used the genus name Eonatator instead. Below is a cladogram following an analysis by Takuya Konishi and colleagues (2016) done during the description of Phosphorosaurus ponpetelegans, which showcases the internal relationships within the Halisaurinae. The analysis excluded the dubious Halisaurus onchognathus and the genus Pluridens. References Further reading Lindgren J, Siverson M. 2005. Halisaurus sternbergii, a small mosasaur with an intercontinental distribution. Journal of Paleontology 79 (4): 763–773. External links Kansas Mosasaurs in Sweden: the type specimen of Eonatator (Halisaurus) sternbergi Wiman 1920 @ Oceans of Kansas, very