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Jurassic Forum » JURASSIC references & paper reviews » Jurassic around the world » Parent et al. (2008) (Sexual phenomena in Late Jurassic Aspidoceratidae)
Parent et al. (2008)
mhornДата: Monday, 12.01.2009, 23:47 | Сообщение # 1
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Parent H., Scherzinger A., Schweigert G. (2008) Sexual phenomena in Late Jurassic Aspidoceratidae (Ammonoidea). Dimorphic correspondence between Physodoceras hermanni (BERCKHEMER) and Sutneria subeumela SCHNEID, and first record of possible hermaphroditism // Paleodiversity. Vol.1. P.181-188.

Pdf: http://www.palaeodiversity.org/pdf/Palaeodiversity_1_12_181-188.pdf

New collections of the dimorphic ammonite species Physodoceras hermanni (Berckhemer) [M] and Sutneria subeumela Schneid [m] from the Upper Jurassic (Beckeri Zone, Subeumela Subzone, subsidens horizon) of Swabia demonstrates first time evidence of intra-sexual polyphenism in Aspidoceratidae. In the macroconchs two size classes demonstrate different times of maturity, leading to small and large adults. In the microconchs, besides a continuous size range of adults, a unique case of possible sexual change in a subadult stage is observed that could point to the occurrence of hermaphroditism in ammonites.


Middle Jurassic - Lower Cretaceous ammonites & aptychi
 
mhornДата: Saturday, 17.01.2009, 22:05 | Сообщение # 2
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Authors describe very interesting example of Sutneria which joined features of [m] and [M] within one specimen. Perhaps, it is one of the strong evidences for sexual nature of such kind of ammonite dimorphism.

Two size classes inferred in macroconchs Physodoceras hermanni resembling occurrences of such size classes in many modern coleoids, which differ in time of hatching, longevity of life and spawning season. The same phenomena occur also among other Kimmeridgian and Tithonian aspidoceratids. For example, Hantzpergue (1989) recognized such morphs within lineage of the Kimmeridgian aspidoceratids as possible succession of micro-and macroconchs. Two size classes also present in the Upper KImmeridgian aspidoceratinds of the Volga area: both morphs ammonites frequently occur in the top of the Eudoxus zone (Asp. quercynum) and basal Autissiodorensis Zone (Schaireria cf. fluegeli) of the Gorodischi and Murzicy sections. The same classes were recognized in the both ammonites S. neoburgense and their aptychy of the Gorodischi section (see Rogov 2004, pdf: http://rogov.zwz.ru/Rogov%202004%20Volgian%20aptychi.pdf )


Middle Jurassic - Lower Cretaceous ammonites & aptychi
 
Jurassic Forum » JURASSIC references & paper reviews » Jurassic around the world » Parent et al. (2008) (Sexual phenomena in Late Jurassic Aspidoceratidae)
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