Phragmoceratidae
family of molluscs
The Phragmoceratidae is a family of extinct nautiloid cephalopods from the Order Discosorida that lived during the latter part of the Silurian.
Diagnosis
Phragmoceratids are characterized by generally compressed, upwardly curved endogastric shells with slit-like apertures for egress and ventral siphuncles with broadly expanded segments, thick connecting rings, and small to vestigial bullettes.
Phragmoceratids are morphologically similar in regards to their constricted apertures to the more cylindrical and orthoconic Mandaloceratidae, also discosorids, and to the oncocerid Hemiphragmoceratidae (Sweet 1964); both which also come from the Silurian.
Derivation
The Phragmoceratidae are derived from the Ordovician Cyrtogomphoceratidae which are also endogastric but with open, unconstricted apertures and well-developed bullettes in the siphuncle.
Phylogeny
The family has its beginning with the Middle Silurian Protophragmoceras, known from a gradually and evenly expanding endogastric shell with an unrestricted aperture, like that of its cyrtogomphoceratid ancestors, deep sharp hyponomic sinus for the water-jet funnel, and ventral siphuncle, phragmoceratid in character.
Protophragmoceras gave rise to the Middle Silurian Phragmoceras, which gave rise to the closely related Middle Silurian Tubiferoceras and to the Upper Silurian Pristeroceras and Phragmocerina. Protophagmoceras also gave rise to the less characteristic but still included Middle Silurian Endoplectoceras and Sthenoceras, which extends into the Lower Devonian.
Genera
Phragmoceras, type genus, is known by its moderately large, strongly curved, rapidly enlarging, endogastric and compressed shell with a vertically constricted aperture that opens up at either end. The siphuncle is close to the concave ventral margin, segments broadly expanded, connecting rings thick, bullettes identifiable.
Tubiferoceras is similar to Phragmocreas except that the dorsal expansion of the aperture sits on a tubular extension and the shell is straighter and more rapidly expanding.
This brief starts where responsible research should: with the source description of “Phragmoceratidae” as family of molluscs. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the general reference register because the source frames it as family of molluscs. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Aug 29, 2026. The linked authority identifier is Q7188048. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1964.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Phragmoceratidae”, its source revision and the description used here.
- Expand the search: follow Phragmoceratidae primary sources, Phragmoceratidae archive and Phragmoceratidae research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Phragmoceratidae”?
- Which institution is responsible for the underlying evidence?
- Which cited source is closest to the event, object or claim?
Search terms from this dossier
This entry incorporates text from “Phragmoceratidae” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.