Fibulariidae

Duncan, 1889, p.144

Genre type : Fibularia Lamarck, 1816, p.16

Description succinte de la famille : pas de piliers de renfort internes. Péristome et périprocte, séparés seulement par deux rangées de plaques post-basicoronales dans l'interambulacre. Sillons nourriciers absents.


 

Genre  Fibularia Lamarck, 1816, p.16

Histoire des animaux sans vertèbres

Espèce type  Fibularia ovulum Lamarck, 1816, par désignation subséquente, résolution ICZN, 1950, p.519.

Extension stratigraphique (bibliographique, non vérifiée) : Eocène - Actuel

Syn.

  • Fibulina Tornquist, 1904, p. 327, espèce type Fibulina gracilis Tournquist, 1904 ; synonyme subjectif plus récent

  • Tarphypygus Clark, 1927, espèce type Tarphypygus ellipticus Clark, 1927 ; synonyme subjectif plus récent

 
 

Fibularia damensis Kier,1972

 
 

Fibularia damensis Kier, new species

Plate 59 : figures 2-10 ; Plate 60 : figure 1

Echinocyamus sp., Steineke, Bramkamp, Sander, 1958: 1313.—Powers, Ramirez, Redmond, and Elberg 1966: D92, 093, D95, D97

     DIAGNOSIS. — Species characterized by well-developed petals and low test with height equal to 54.6 percent of the length of the test.

     MATERIAL. — Hundreds of specimens but description based on 38 specimens from one locality.

     SHAPE. — Test 4.5-10.0 mm long with mean of 7.1 mm, greatest width at apical system or anterior, width 86.6 percent L (S.D. 3.5, C.V. 4.1, N-37) ; great­est height anterior to apical system, height 54.6 percent L (S.D. 4.9, C.V. 8.9, N-38) ; adapical sur­face flat or slightly inflated, petals flush on some specimens, slightly inflated on others, apical system slightly inflated; marginal outline oblong on most smaller specimens, subpentagonal on larger with an­terior pointed; periproct flush, peristome slightly depressed only along immediate edge of opening; adorai surface slightly depressed to slightly convex.

     APICAL SYSTEM. — Central to slightly anterior, dis­tance from anterior margin of test to anterior genital pores 46.7 percent L (S.D. 2.3, C.V. 4.8, N-37) ; width of apical system as measured across posterior genital pores 7.3 percent L (S.D. 1.3, C.V. 17.6, N-37) ; four genital pores arranged in trapezoid with anterior pair doser together; hydropore in furrow (Plate 59: figure 2).

     AMBULACRA. — Petals long and broad, extending al­most to margin, of approximately equal length; length of petal III 40.6 percent L (S.D. 2.9, C.V. 7.2, N-38), width 18.6 percent L (S.D. 1.9, C.V. 10.6, N-37) ; greatest width of petals near midlength or slightly distal; interporiferous zones expanding dis­tally (Plate 59: figure 2), poriferous zones narrowing distally; pores conjugate (conjugation grooves visible only on well-preserved specimens), opening circular; smallest specimen 4.5 mm long with 8 porepairs in single poriferous zone in petal 1, 6 in petals II and III, largest specimen 9.8 mm long with 12 in petal I, eleven in petals II, III; average of 8.8. porepairs in ail measured specimens in petal I, 7.1 in II, 8.5 in III with mean of 1.2 porepairs in single poriferous zone for each millimeter of length of test in petal I, 1.0 in petal II, 1.2 in petal III.

     PERISTOME. - Central, subcircular to subpentagonal, slightly higher than wide (Plate 59: figure 4), height 13.5 percent L (S.D. 1.6, C.V. 12.1, N-38).

     PERIPROCT. - Situated nearer peristome than pos­terior margin, at distance from peristome equal to 9.7 percent L (S.D. 1.6, C.V. 16.5, N-38) ; oblong, height greater than width, opening smaller than peristome.

     INTERNAL STRUCTURES. - No internal structure (Plate 60: figure 1) ; auricles interradial.

     COMPARISON WITH OTHER SPECIES. - This species is easily distinguished from most species of Fibularia by its well-developed petals. It is most similar to Fibularia dubarensis Kier from the Miocene of British Somaliland in having similarly shaped petals, and my first impression was that the Arabian specimens be­longed to this species. When I described the Somali-land species I did not make an adequate number of measurements and therefore could not make a definitive comparison of the Arabian and Somaliland speci­mens. I borrowed from the Sedgwick Museum 86 specimen and have now made the necessary measure­ments, the compilation of which follows this paragraph. The Arabian species is distinguished from the Somaliland F. dubarensis by its lower test with a height equal to 54.6 percent the length as opposed to 65.8 percent in F. dubarensis. A student t-test shows that the chances are far less than one in a thousand that the specimens came from one population.

 

     The following are the statistics of 70 specimens of Fibularia dubarensis Kier, 1957:870, from the Miocene of British Somaliland. These specimens are in the Sedgwick Museum, Cambridge, England.

Length: mean 8.1 mm (S.D. 2.2, C.V. 28.3, N-70). Percent width of L: 87.9 (S.D. 3.1, C.V. 3.5, N-70) . Percent height of L: 65.8 (S.D. 5.8, C.V. 8.7, N-70). Percent length of petal III of L: 45.6 (N-60).

Percent width of petal III of L: 18.5 (S.D. 2.1, C.V. 11.7, N-63).

Percent width of apical system of L: 7.4 (S.D. 1.1, C.V. 15.4, N-66).

Percent distance from apical system to anterior margin of L: 47.5 (S.D. 3.1, C.V. 6.5, N-68).

Percent height of peristome of L: 12.8 (S.D. 1.8, C.V. 14.3, N-61).

Percent height of periproct of L: 10.5 (S.D. 1.2, C.V. 11.5, N-62).

Percent distance from periproct to peristome of L: 9.0 (S.D. 2.3, C.V. 19.6, N-63) .

Ratio of number of porepairs in single poriferous zone to length of test in millimeters.

Petal I: 1.4

Petal II: 1.2

Petal III: 1.5

     Fibularia damensis in general appearance resembles Echinocyamus woodi Currie (1930:172) from the Miocene of British East Africa. Dr. Currie does not state whether her species has internai partitions which would be expected if it was an Echinocyamus. F. damensis differs in having fewer porepairs in its petals. Her figured specimen of E. woodi which is 8.4 mm long has 12-13 porepairs in each poriferous zone, whereas a specimen of similar size of F. damensis has only 7-10.

     TYPE SPECIMENS. - Holotype, USNM 170481; figured paratypes, 170482-170484.

     STRATIGRAPHIC OCCURRENCE AND LOCALITIES. ‑ Miocene, Dam Formation, localities S-137, S-178, S-553, S-568, S-1392.

Extrait planches 59 & 60

 

 

 

 

Fibularia damensis Kier,1972 - Miocène, Dam formation, Doha, Qatar, 13 mm (& 3-6 mm)

 
 
 
 

Fibularia texana (Twitchell,1915)

 
 
diagnose originale de l'espèce par Twitchell,1915
the Mesozoic and Cenozoic Echinodermata of the United States, p.120
 

Echinocyamus texanus Twitchell, n. sp.

Plate LVII, figures 2a-d.

     Determinative characters.—Test very small, ellipsoidal, oval in marginal outline. Upper surface elevated, somewhat flattened in the center; lower surface flattened around the nearly flush peristome. Apical system with four medium-sized genital pores; madreporite tumid. Petals long, the anterior three nearly reaching the margin, wide open at ends. Peristome relatively large, central; periproct very small, close to peristome.

     Dimensions.—Length 5 millimeters; width 4 millimeters; height 2.5 millimeters.

      Description.—Only a single specimen of this new Echinocyamus lias been discovered. It was found by Mr. T. H. Aldrich of Birmingham, Ala., who reports that it was found in the "Lower Claiborne" deposits of Lee County, Tex. The test-is thick-walled, very small (it being one of the smallest of American echinoderms), regularly oval in marginal outline, and ellipsoidal in general form. The upper surface is elevated, somewhat flattened centrally; the lower sur­face flattened near the nearly flush peristome and the periproct.

     The ambulacral petals are rather well defined, relatively long, all of about equal length, the anterior three extending nearly to the margin as seen from above. The poriferous zones diverge in almost straight lines to the ends where they are wide apart; they consist of small round pores in pairs which are apparently not conjugated.

     The apical system is subcentral or very slightly excentric anteriorly, coincident with the apex, with four moderate-sized genital pores set near together, the anterior pair but slightly nearer together than the posterior pair. A small, swollen, button-shaped madreporite just reaches to the genital pores.

 

      The peristome is relatively large, central, nearly flush with the lower surface; periproct very small, about one-third of the diameter of the peristome, and is situated at a distance from the peristome equal to its own diameter.

     Related forms.—E. texanus is most closely related to E. vaughani, but is easily distinguished from it by its less egg-shaped form, smaller size, less pointed anterior end, and less difference between its longitudinal and transverse diameters. E. texanus also resembles E. parvus and E. huxleyanus but differs from both in having its periproct near the peristome. It also differs from E. huxleyanus in being less fragile, less depressed, and less pointed anteriorly.

     Locality.—Lee County, Tex.

     Geologic horizon.—Lower part of Claiborne group, middle Eocene.

     Collection.—Johns Hopkins University (T 2002).

Extrait planche LVII

 

   

 

 
 

Fibularia texana (Twitchell,1915) - Eocène, Mount Seleman fm, San augustine county, Texas, U.S.A., 7 mm