Estonioceratidae

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Estonioceratidae
Temporal range: L Ordovician
Estonioceras ariense 01.jpg
Estonioceras ariense
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Nautiloidea
Order: Tarphycerida
Family: Estonioceratidae
Hyatt in Zittel, 1900

The Estonioceratidae are a family of loosely coiled tarphycerids in which the inner side of the whorls, which forms the dorsum, is rounded or flat with no impression, and in which the siphuncle, composed of thick tubular segments, is located ventrally. The Estonioceratidae seem to form a link between the ancestral Bassleroceratidae and the more tightly coiled Tarphyceratidae. [1] [2]

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<span class="mw-page-title-main">Ordovician</span> Second period of the Paleozoic Era, 485–444 million years ago

The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period 485.4 Ma to the start of the Silurian Period 443.8 Ma.

<span class="mw-page-title-main">Nautilida</span> Order of cephalopods

The Nautilida constitute a large and diverse order of generally coiled nautiloid cephalopods that began in the mid Paleozoic and continues to the present with a single family, the Nautilidae which includes two genera, Nautilus and Allonautilus, with six species. All told, between 22 and 34 families and 165 to 184 genera have been recognised, making this the largest order of the subclass Nautiloidea.

<span class="mw-page-title-main">Nautiloid</span> Extant subclass of cephalopods

Nautiloids are a group of marine cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living Nautilus and Allonautilus. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. They flourished during the early Paleozoic era, when they constituted the main predatory animals. Early in their evolution, nautiloids developed an extraordinary diversity of shell shapes, including coiled morphologies and giant straight-shelled forms (orthocones). No orthoconic and only a handful of coiled species, the nautiluses, survive to the present day.

<span class="mw-page-title-main">Chitinozoan</span> Group of marine microfossils

Chitinozoa are a group of flask-shaped, organic walled marine microfossils produced by an as yet unknown organism. Common from the Ordovician to Devonian periods, the millimetre-scale organisms are abundant in almost all types of marine sediment across the globe. This wide distribution, and their rapid pace of evolution, makes them valuable biostratigraphic markers.

The Ellesmerocerida is an order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.

<i>Aphetoceras</i>

Aphetoceras is a genus of tarphycerid cephalopod within the Estonioceratidae; loosely coiled without an impression along the dorsal margin; early whorls barely reaching, separating then diverging in the final mature whorl; weakly ribbed in some. The cross section of Aphetoceras is higher than wide, making it compressed in form. The dorsum, along the inner curve, is more broadly rounded than the venter which lies along the outer curve. The siphuncle is relatively large, located near but not at the ventral margin; lined with secondary deposits. Chambers are empty.

<span class="mw-page-title-main">Tarphycerida</span> Extinct order of molluscs

The Tarphycerida were the first of the coiled cephalopods, found in marine sediments from the Lower Ordovician to the Middle Devonian. Some, such as Aphetoceras and Estonioceras, are loosely coiled and gyroconic; others, such as Campbelloceras, Tarphyceras, and Trocholites, are tightly coiled, but evolute with all whorls showing. The body chamber of tarphycerids is typically long and tubular, as much as half the length of the containing whorl in most, greater than in the Silurian Ophidioceratidae. The Tarphycerida evolved from the elongated, compressed, exogastric Bassleroceratidae, probably Bassleroceras, around the end of the Gasconadian through forms like Aphetoceras. Close coiling developed rather quickly, and both gyroconic and evolute forms are found in the early middle Canadian.

<span class="mw-page-title-main">Actinocerida</span> Extinct order of molluscs

The Actinocerida are an order of generally straight, medium to large cephalopods that lived during the early and middle Paleozoic, distinguished by a siphuncle composed of expanded segments that extend into the adjacent chambers, in which deposits formed within contain a system of radial canals and a narrow space along the inner side of the connecting ring known as a paraspatium. Septal necks are generally short and cyrtochoanitic, some being recumbent, some hook shaped. Most grew to lengths of about 60 to 90 cm but some, like the Huroniidae of the Silurian grew significantly larger.

<span class="mw-page-title-main">Lituitida</span> Order of molluscs

Lituitida is an order of orthoceratoid cephalopods. They correspond to the family Lituitidae of the Treatise, reranked as an order and combined with other orthoceratoids. They are considered to be more closely related to the Orthocerida than to the Ascocerida or Pseudorthocerida which are also included.

The Tarphyceratidae are tightly coiled, evolute Tarphycerida with ventral siphuncles. The dorsum is characteristically impressed where the whorl presses against the venter of the previous. The Tarphyceratidae are derived from Bassleroceras or possibly from some member of the Estonioceratidae.

<span class="mw-page-title-main">Trocholitidae</span> Extinct family of nautiloids

The Trocholitidae are Tarphycerida with whorls in close contact as with the Tarphyceratidae, but in which the siphuncle, similar in structure, becomes dorsal. The Trocholitidae are derived from the Tarphyceratidae, perhaps from different tarphyceratids.

<span class="mw-page-title-main">Lituitidae</span> Family of molluscs

The Lituitidae are a family of evolved tarphycerids characterized by a long orthoconic section that follows a coiled juvenile portion at the apex, along with a generally tubular siphuncle, which like that of the barrandeocerids is composed of thin connecting rings.

<span class="mw-page-title-main">Eldoniid</span> Extinct clade of disc-shaped animals

Eldoniids or eldonioids are an extinct clade of enigmatic disc-shaped animals which lived in the early to middle Paleozoic. They are characterized by their "medusoid" (jellyfish-shaped) bodies, with the form of a shallow dome opening below to an offset mouth supplemented by filamentous tentacles. Internally, they have a distinctive C-shaped cavity encompassing the gut, as well as hollow radial (radiating) structures arranged around a central ring canal. Most eldoniids are soft-bodied and can only be preserved in lagerstätten, but a few species may have hosted mineralized deposits. Historically, the affinities of eldoniids was enigmatic; recently, they been assessed as cambroernid deuterostomes. Their lifestyle is still an unresolved question; some authors reconstruct eldoniids as free-floating planktonic predators similar to jellyfish, while others argue that they were passive detritivores, embedded within the seabed for much of their life.

The cephalopods have a long geological history, with the first nautiloids found in late Cambrian strata.

<span class="mw-page-title-main">Rhynchonelliformea</span> Subphylum of brachiopods

Rhynchonelliformea is a major subphylum and clade of brachiopods. It is roughly equivalent to the former class Articulata, which was used previously in brachiopod taxonomy up until the 1990s. These so-called articulated brachiopods have many anatomical differences relative to "inarticulate" brachiopods of the subphyla Linguliformea and Craniformea. Articulates have hard calcium carbonate shells with tongue-and-groove hinge articulations and separate sets of simple opening and closing muscles.

<span class="mw-page-title-main">Rhynchonellata</span> Class of marine lamp shells

The Rhynchonellata is a class of Lower Cambrian to Recent articulate brachiopods that combines orders from within the Rhynchonelliformea with well developed pedicle attachment. Shell forms vary from those with wide hinge lines to beaked forms with virtually no hinge line and from generally smooth to strongly plicate. Most all are biconvex. Lophophores vary and include both looped and spiraled forms. Although morphologically distinct, included orders follow a consistent phylogenetic sequence.

<i>Alaskoceras</i>

Alaskoceras is a genus of lower Ordovician coiled nautiloid cephalopods; the shell moderately expanded, ribbed, with a divergent living chamber; whorl section more broadly rounded ventrally than dorsally; siphuncle marginal at maturity, septal necks short, almost achoanitic; connecting rings thick, layered.

<span class="mw-page-title-main">Paleontology in Illinois</span> Paleontological research in the U.S. state of Illinois

Paleontology in Illinois refers to paleontological research occurring within or conducted by people from the U.S. state of Illinois. Scientists have found that Illinois was covered by a sea during the Paleozoic Era. Over time this sea was inhabited by animals including brachiopods, clams, corals, crinoids, sea snails, sponges, and trilobites.

<span class="mw-page-title-main">Paleontology in Missouri</span> Paleontological research in the U.S. state of Missouri

Paleontology in Missouri refers to paleontological research occurring within or conducted by people from the U.S. state of Missouri. The geologic column of Missouri spans all of geologic history from the Precambrian to present with the exception of the Permian, Triassic, and Jurassic. Brachiopods are probably the most common fossils in Missouri.

Charactoceras is a tarphycerid genus cephalopod which lived during the Late Ordovician.

References

  1. Flower, R. H. 1976. Ordovician Cephalopod Faunas and Their Role in Correlation in The Ordovician System: proceedings of a Palaeontological Association symposium, Sept 1974.
  2. Furnish, W. M, and Glenister, Brian F. 1964. Nautiloidea – Tarphycerida; Treatise on Invertebrate Paleontology, Part K, Geol. Soc. of America, Teichert and Moore (eds.)