Orthildaites Explained

Orthildaites is a genus of ammonites that lived during the lower Toarcian stage of early Jurassic, during Falciferum subzone.

Description

Shell of these ammonites had quadrate whorl section with broad venter and strong keel in the center. Almost straight ribs were curving slightly forward at ventrolateral edge. Coiling has been evolute. It has evolved form genus Hildaites and gave rise to Hildoceras from which it differs in morphology by broader whorls and straight ribs.

Remarks

Orthildaites fossils were found in Europe and north Africa.^[1] Only one (or two) species is known in the Toarcian NW European domain, its diversity is higher in the Mediterranean faunal province.^[2]

Validity of O. orthus is debated, as sometimes it is considered to be valid, while other authors consider it to be a synonym of O. douvillei.^{[3] [4]}

Notes and References

1. M. K. Howarth 2013. Treatise on Invertebrate Paleontology, Part L, Revised, Volume 3B, Chapter 4: Psiloceratoidea, Eoderoceratoidea, Hildoceratoidea.
2. Kovács. Zoltán. 2012. Lower Toarcian Ammonitida fauna and biostratigraphy of the Gerecse Mountains (Hungary).. Fragmenta Palaeontologica Hungarica. 29. 1–48. ResearchGate.
3. HOWARTH, Michael K. The ammonite family Hildoceratidae in the Lower Jurassic of Britain. Monograph of the Palaeontographical Society, 1992, 145.586: 1-106.
4. Bécaud. Marc. 2006. Les Harpoceratinae, Hildoceratinae et Paroniceratinae du Toarcien de la Vendée et des Deux-Sèvres (France).. Documents des Laboratoires de Géologie de la Faculté des Sciences de Lyon. 161. 1–245.