Phylum: Bryozoa
Class: Stenolaemata
Order: Cyclostomata
Genus: Corynotrypa Bassler, 1911
Cincinnatian Species: Corynotrypa delicatula, Corynotrypa inflata

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Type Species: Hippothoa delicatula (James, 1878)Species found in the Cincinnatian, USA

  • Corynotrypa delicatula (James, 1878)
  • Corynotrypa inflata (Hall, 1847)

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Geologic Range
Ordovician – Cretaceous

Stratigraphic Occurrences


Geographic Occurrences

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Sequences (Formations)

  • C6 Sequence (Elkhorn)
  • C5 Sequence (Lower Whitewater, Liberty)
  • C4 Sequence (Arnheim: Oregonia, Sunset)
  • C3 Sequence (Mt. Auburn, Corryville)
  • C2 Sequence (Bellevue, Fairview: Fairmount, Mount Hope)
  • C1 Sequence (Clays Ferry/Kope: McMicken, Southgate, Economy, Fulton)

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Identification in Hand Sample:

  • Branching by bifurcation and/or lateral ramification
  • Zooids monomorphic, entirely exterior-walled, elliptical, clavate or filiform
  • Chambers of zooids in linear series in continuity via a narrow canal
  • Skeletons are composed entirely of exterior wall
  • Runner-like colonies: uniserial zooids encrusting in a branching pattern.

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Taylor and Wilson(1994):

  • Colony encrusting, uniserial, branching by bifurcation and/or lateral ramification primary zone of astogenetic change present in early parts of colonies, secondary zones sometimes developed in lateral branches; zooids monomorphic, entirely exterior-walled, elliptical, clavate or filiform, narrow proximally, distally with a subcircular aperture and variably preserved peristome, sometimes occluded by a terminal diaphragm; chambers of zooids in linear series in continuity via a narrow canal.
  • The scarcity of useful morphological characters for taxonomic purposes in Corynotrypa is apparent from Bassler’s (1911) systematic study of the genus: stratigraphical occurrence rather than morphology was a major factor in species discrimination for Bassler. Nevertheless,Bassler was able to recognize three groups of species, which he termed “sections,” based on zooid shape: 1) a C. delicatula group with extremely slender zooids, 2) a C. inflata group with zooids widening rapidly after a proximal constriction; and 3) a C. dissimilis group with stout zooids little constricted proximally. The present study has not only failed to reveal any additional zooid-level character but has also shown that zooid indicative of the C. delicatula and C. inflata groups can occur in the same colony as C. delicatula as astogenetic variants. Furthermore, colony-level morphological characters, such as position and occupation of budding loci, and branching angle and frequency, do not furnish taxonomically useful characters because they all have high values of within-colony variability that seem to overwhelm subtle differences that may occur between different species (however, thorough morphometric study might perhaps prove otherwise). The prospects for a more refines species-level systematics of Corynotrypa are therefore poor.

Taylor & Wilson (1994):

  • Runner-like colonies (Jackson, 1979), with zooids uniserially arranged along encrusting branches, occur in several groups of bryozoans….. Corynotrypa was founded by Bassler (1911)… assigned the genus 16 species from the Ordovician to Paleocene…. Abundances peak in Ordovician.
  • Zooids of Corynotrypa have a simple morphology; their skeletons are composed entirely of exterior wall, with the living chambers of adjacent zooids in continuity via narrow communication pores at the constricted junctions between the zooids (Boardman & Cheetham, 1973; Brood, 1975). The skeletal simplicity of Corynotrypa, together with its general resemblance to certain uncalcified ctenostome bryozoans, has led to an interpretation of the genus as the most primitive known stenolaemate bryozoa.

Treatise on Invertebrate Paleontology (1953):

  • Like Stomatopora but proximal part of zooecium constricted for union with preceding one.

Bassler (1911):

  • Zoarium adnate, consisting of simple, subtubular zooecia arranged in single-branched series; zooecia over-pyriform to elongate clavate, the proximal end constricted and united with the preceding zooecium by a narrow, tubular stolon of variable length; the distal portion more or less expanded and bearing on its frontal side the aperture which is subterminal, circular, and inclosed by a more or less distinct, slightly elevated peristome; walls finely porous.
  • Genotype, Stomatopora delicatula James. Ordovician of America and Europe. Range of
    genus, base of Ordovician to the close of Mesozoic; probably also Cenozoic.
  • The closest ally of Corynotrypa is undoubtedly the well-known and even more widely distributed and longer-lived Stomatopora. The two genera agree in having an incrusting zoarium composed of simple, porous, tubular zooecia arranged uniserially. Corynotrypa differs from Stomatopora most obviously in the constriction of the proximal end of the zooecium, giving it the characteristic clavate to pyriform shape which causes each to stand out as an individual. In Stomatopora the successive zooecia form a narrow branch with more or less parallel sides in which the individuals are scarcely delimitable except by their apertural opening.
  • Among the species referred to Corynotrypa, the proximal constriction is more evident in those assigned to the C. inflate and the C. delicatula groups discussed later but becomes less marked in such forms as C. canadensis and C. dissimilis. The last two represent a third group in which the generic relationship to Stomatopora is much more obvious. In addition to the shape of the zooecium, the aperture in Corynotrypa likewise presents good generic characters. In typical Stomatopora the aperture is exsert, usually slightly tilted forward, and often almost equals the zoarial branch in diameter. CorynotrypaC. dissimilis group of Corynotrypa, the nearer relation to Stomatopora is again expressed, in that the zooecial apertures are occasionally exsert and of unusual width.
  • Altogether it is believed that the club-shaped zooecia produced by the constriction of the proximal end, and the small, neatly constricted aperture with low peristomes, constitute sufficient characters to justify a new genus, although it is recognized that several intermediate forms exist between this genus and Stomatopora, as here restricted.
  • This new cyclostomatous genus, in its method of growth and general shape of the zooecia is quite similar to genera of other orders, an occurrence which is not unusual in the Bryozoa. Such species as Corynotrypa nitida or C. tenuichorda are exceedingly like elongate, delicate forms of Hippothoa, and might readily be confused. The latter genus, however, a representative of the Chilostomate, has a sinus in the lower margin of the aperture and an occasional well-marked zooecium, as well as a very delicate surface ornamentation quite different, on close examination, from the simple punctate structure of Corynotrypa. Among the Ctenostomata such genera as the recent Arachnidium and the fossil Rhopalonaria are so similar in general shape to Corynotrypa that at least one species of the last genus was originally referred to the second.

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Species Differentiation

C. delicatula

C. inflata