Hecticoceratinae is a subfamily of
oppeliids from the Middle and Upper
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...
typically with strong falcoid or falcate ribbing that covers whorl sides completely. Venters are usually keeled and may be tricarinate.
[Treatise on Invertebrate Paleontology Part L, ''L276'' (Ammonoidea)]
The Hecticocerainae, which has its origin in the
Oppeliinae, give rise to the
Distichoceratinae near the beginning of the Middle Jurassic
Callovian
In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...
, and to the
Glochiceratinae early in the Upper Jurassic
Oxfordian.
[Classification of Jurassic Ammonitina, D.T. Donovan, et al., Systematics Assoc., 1981] Neither apparently gave rise to any subsequent groups.
Genera
''Hecticoceras'', ''Brightia'', ''Eochetoceras'', ''Hecticoceratoides'', ''Lunuloceras'', ''Kheraites'', ''Proheticoceras'', ''Pseudobrightia'', and ''Pseudobrightia'', listed as separate genera in the
Treatise
A treatise is a formal and systematic written discourse on some subject, generally longer and treating it in greater depth than an essay, and more concerned with investigating or exposing the principles of the subject and its conclusions."Treat ...
[ are regarded as subgenera of '']Hecticoceras
''Hecticoceras'' is an ammonite genus belonging to the haploceratoid family Oppeliidae, that lived during the Middle and Late Jurassic, from the Callovian. ''Hecticoceras'' may be seen as a series of some nine subgenera, beginning with the lowe ...
''
References
Oppeliidae
Jurassic ammonites
Bathonian first appearances
Late Jurassic extinctions
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