Early Jurassic estuarine ecosystem, with Palaeoxyris egg cases attached via tendril to Neocalamites, with hybodonts in the background
Palaeoxyris is a morphogenus of eggs cases, widely thought to have been produced by hybodonts, with a predominant occurrence in ancient freshwater environments. They comprise a beak, a body and a pedicle. They display a conspicuous right-handed spiral of collarettes around the body, and in some cases, the pedicle, resulting in a rhomboidal pattern when flattened during fossilisation.[1] At the end of the beak was a tendril which attached the egg to vegetation during development.[2] The body of the egg ranges in length from 1.2–8.9 centimetres (0.47–3.50 in), depending on the species.[3]
Originally described as plant remains (being named after the plant genus Xyris), it took decades before their true nature as animal eggs was revealed.[4] Nearly 30 different Palaeoxyris species are currently known with a stratigraphic range from the Carboniferous to the Cretaceous.[1][5] Mesozoic Palaeoxyris specimens differ from Paleozoic specimens by having the twisting of the collarette end at the beginning of the pedicle, rather than the spiraling continuing down the pedicle as in Paleozoic specimens.[6] Likely hybodont producers of some of the eggs assigned to the genus include the genus Lonchidion.[5]
^ abRonald Böttcher (2010). "Description of the shark egg capsule Palaeoxyris friessi n. sp. from the Ladinian (Middle Triassic) of SW Germany and discussion of all known egg capsules from the Triassic of the Germanic Basin" (PDF). Palaeodiversity. 3: 123–139.
^Krüger, Ashley; Slater, Sam; Vajda, Vivi (2021-07-03). "3D imaging of shark egg cases ( Palaeoxyris ) from Sweden with new insights into Early Jurassic shark ecology". GFF. 143 (2–3): 229–247. doi:10.1080/11035897.2021.1907442. ISSN 1103-5897.
^Fischer, Jan; Axsmith, Brian J.; Ash, Sidney R. (2010-03-01). "First unequivocal record of the hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 255 (3): 327–344. doi:10.1127/0077-7749/2009/0028. ISSN 0077-7749.
^Jan Fischer & Ilja Kogan (2008). "Elasmobranch egg capsules Palaeoxyris, Fayolia and Vetacapsula as subject of palaeontological research – an annotated bibliography". Freiberger Forschungshefte. C 528: 75–91.
^ abJan Fischer; Sebastian Voigt; Jörg W. Schneider; Michael Buchwitz; Silke Voigt (2011). "A selachian freshwater fauna from the Triassic of Kyrgyzstan and its implication for Mesozoic shark nurseries". Journal of Vertebrate Paleontology. 31 (5): 937–953. doi:10.1080/02724634.2011.601729. S2CID 85753690.
^Fischer, Jan; Licht, Martin; Kriwet, Jürgen; Schneider, Jörg W.; Buchwitz, Michael; Bartsch, Peter (2014-04-03). "Egg capsule morphology provides new information about the interrelationships of chondrichthyan fishes". Journal of Systematic Palaeontology. 12 (3): 389–399. doi:10.1080/14772019.2012.762061. ISSN 1477-2019.
different Palaeoxyris species are currently known with a stratigraphic range from the Carboniferous to the Cretaceous. Mesozoic Palaeoxyris specimens...
cartilaginous fish. Most hybodont egg cases are assigned to the genus Palaeoxyris, which tapers towards both ends, with one end having a tendril which...
Illustration of Neocalamites stems growing in an estuarine environment, with attached hybodont egg cases (Palaeoxyris) and hybodonts in the background...
often found in freshwater and brackish deposits. Hybodont egg cases (Palaeoxyris) associated with juvenile teeth of L. ferganensis in the Triassic lake...
2014). "A Comparative Study of the Australian Fossil Shark Egg-Case Palaeoxyris duni, with Comments on Affinities and Structure". Proceedings of the...
Plagiosuchus, Callistomordax, Nanogomphodon, Batrachotomus, Kupferzellia and Palaeoxyris friessi. "Erfurt Formation". BGR. Archived from the original on 10 February...
(2010-03-01). "First unequivocal record of the hybodont shark egg capsule Palaeoxyris in the Mesozoic of North America". Neues Jahrbuch für Geologie und Paläontologie...
Eocene Egypt A hemigaleid. The type species is Moerigaleus vitreodon. Palaeoxyris alterna Species Valid Fischer Voigt et al. Middle/Late Triassic Madygen...
2015-04-16. Ronald Böttcher (2010). "Description of the shark egg capsule Palaeoxyris friessi n. sp. from the Ladinian (Middle Triassic) of SW Germany and...
Madygen Formation. Two distinctive elasmobranch egg capsule types, i.e. Palaeoxyris, indicating a small Lissodus- or Lonchidion-like hybodont shark and an...