Haimeicyclus haimei ( Chapuis and Dewalque, 1853 )

Stolarski, Jarosław & Russo, Antonio, 2002, Microstructural diversity of the stylophyllid (Scleractinia) skeleton, Acta Palaeontologica Polonica 47 (4), pp. 651-666 : 653-656

Haimeicyclus haimei ( Chapuis and Dewalque, 1853)

Figs. 2–5 .

Montlivaltia haimei sp. nov.; Chapuis and Dewalque 1853: 263–264, pl. 38: 5.

Montlivaltia haimei Chapuis and Dewalque ; Duncan 1867: 35, pl. 10: 24–32.

Montlivaltia haimei Chapuis and Dewalque ; Quenstedt 1881: 576, pl. 164: 32.

Montlivaltia haimei Chapuis and Dewalque ; Lejeune 1935: pl. 1: 3, 9, 17, pl. 2: 4,

Montlivaltia haimei ChapuisandDewalque ; Joly1936:166,pl.3:1–7.

Montlivaltia haimei var. alta Chapuis and Dewalque ; Joly 1936: 166–167, pl. 3: 8–10.

Haimeicyclus haimei Chapuis and Dewalque ; Alloiteau 1957: 105.

Montlivaltia haimei ChapuisandDewalque ; Beauvais1976:72,pl.16:5.

? Haimeicyclus haimei Chapuis and Dewalque ; Beauvais 1986: 54.

Material.— 81 specimens representing various ontogenetic stages, ranging from early juveniles ca. 0.5 mm in diameter having twelve septa to adults ca. 30 mm in diameter with six incomplete septal cycles (IPUM−Sic.3, 14–93); see Fig. 3 .

Description.—Corallum discoidal, circular, free in adult stage. Proximal side of adult coralla may bear no traces of substrate but often various bivalve shell fragments or flat, often washed away substrate can be observed ( Fig. 2E 2 ). Juveniles can also be attached to the adult coralla ( Fig. 4B 1 , B 2, D 2 –D 4 ). Initial portions of adult coralla, exposed by light etching ( Fig. 4C ) and initial or early juvenile specimens attached to adult coralla ( Fig. 4B 1 , B 2 ) are twelve−septate and have a similar diameter. Juvenile coralla attached to the same small−sized substratum may adhere to themselves ( Fig. 2A 1 , A 2 ). Such double calices possess independent epithecate walls in their contact zone (arrow in Fig. 2A 1 ). Seemingly similar coralla with two calices may develop from a single but regenerated calice ( Fig. 2D 1 , D 2 ). In contrast to the “adhering” specimens, two “regenerated” calices share some skeletal elements, e.g., septa of higher cycles (arrow in Fig. 2D 4 ) and do not develop an epithecate wall in the contact zone between calices. Calices disintegrated into several, not clearly defined zones ( Fig. 2C ), showing asymmetrical constriction ( Fig. 5A, B ), or constricted repeatedly two or more times ( Fig. 2G ) have also been observed.

In adults, septa hexamerally arranged in 6 incomplete cycles according to the formula S1–2ẐS3>S4>S5>S6. Septa S1–3 reach calicular center; S4 extend to ca. 3/4 of the calicular radius; S5 to the half of the calicular radius, and S6 are developed only at calice periphery. All septa consist of spines that lower in fossa are covered with sclerenchyme and form a compact septum. In lower cycle septa (S1–3), individual spines are recognizable only on their distal edge whereas septa of higher cycles, especially of ultimate or penultimate cycles, composed of spines individualized in distal and proximalpartsofcalice( Fig.5B,C ).Surfaceofspinescoveredwith dense granulations ca. 40–50 µm in diameter. Lower in calice, septal faces covered with thicker layers of sclerenchyme and become smoother, except for places with septal spines still projecting through sclerenchymal deposits. Skeleton completely recrystallized, calcitic (confirmed by X−ray diffraction). Epithecate wall spread on entire proximal side and in largerspecimensslightlymorecylindrical,bendingupwards.

Remarks.—InmostScleractiniathelengthoftheseptacorrelates with the order of their appearance. Septa of the first cycle, inserted at the beginning of the coral skeletogenesis are usually much longer and thicker in comparison to the septa of higher cycles inserted later in ontogeny (however, one of the exceptions is Schizocyathus fissilis Pourtalès, 1874 with S2<S 3 in adult coralla. S 2 in S. fissilis degenerate during corallum growth, most likely because of functional involvement in corallum longitudinal division; see Stolarski 2000). On the other hand, in Zardinophyllum zardinii Montanaro−Gallitelli, 1975 (representative of pachythecaliines—supposed rugosan descendants), the first 6 initial septa are not inserted simultaneously and this is reflected in their unequal length and thickness ( Stolarski 1996, 1999). Because the first twelve septa of initial and early juvenile coralla of H. haimei ( Fig. 4B 1 , B 2 , C) have similar length and thickness, one may infer that they were inserted simultaneously and thus the early ontogeny follows a cyclic pattern recognized in typical scleractinians.

Juvenile coralla (but also serpulid tubes) are occasionally found attached to both sides of adult coralla (e.g., Fig. 4D 1 , D 2 ). Such coralla do not show any defensive reaction against incrustation (e.g., constrictions of the corallum diameter as in Fig. 2C ) and it is clear that juveniles could not grow on the proximal side of adult coralla without inverting position of the latter. Thus, most likely, adult coralla were incrusted while dead, and incrustations on both sides were possible because of occasional rolling on such skeletons. On the other hand, the situation when juveniles are attached only to the substrate that also serves adults ( Fig. 4B 4 ) suggests that only the substrate was rolled and not the adult corallum. Judging by the transitional spectrum of morphologies of incrusting initials and juveniles, and by comparisons with initial and juvenile portions of adult coralla, all juveniles incrusting adult coralla belong to the same species. Attachment of juveniles to the adult coralla of the same species were observed in extant (Gerodette 1981; Fadlallah and Pearse 1982) and fossil corals ( Stolarski 1995). In modern seas, corals that produce such settling larvae are brooders releasing large, benthic crawling planulae. Initial coralla that develop after metamorphosis of such large, benthic planulae often exceed 2 mm in diameter (see Squires 1962; Gerodette 1981; Fadlallah and Pearse 1982). The occurrence of numerous juveniles attached to adults in H. haimei may suggest similar benthic behavior, however, much smaller size (ca. 1 mm in diameter) favors a scenario in which local hydrological conditions forces part of the coral “spat” to settle on available hard substrates, i.e., the adult coralla.

The skeleton of H. haimei is competely recrystallized (calcitic), however, dense and homogenous granulation on septal spines conform to a “coarse” texture observed on septa of the below described Stylophyllopsis cf. rugosa and thus implies similar microstructure (see Discussion).

Occurrence.—Sinemurian of Sicily, Early Jurassic (Hettangian –Sinemurian) of Belgium, Germany, Luxembourg, England.

Figures

Fig.2. Haimeicyclus haimei (ChapuisandDewalque,1853). A.IPUM−Sic.92a,bwithtwocalicesindistal(A1)andproximal−lateral(A2)views.Calicesareseparatedbyepithecalwalls(arrowinA1)andresultedfromgrowthoftwojuvenilesattachedtocommonsubstrate.B.DistalviewofIPUM−Sic.82.TwelveS1–2arrowed. C. Distal view of IPUM−Sic.40 with uppermost part of calice disintegrated into 3 (arrows) independent calicular regions (“rejuvenescence”), and overgrown by serpulid tubes (lower part of picture). D. IPUM−Sic.80 with two calices (D1, distal view) resulted from regeneration of parental calice (D2, basal view). IncontrasttoIPUM−Sic.92a,b(A1,A2),highercycleseptaincontactzonebetweencalicesofIPUM−Sic.80arecommonforbothcalices.E.IPUM−Sic.89indistal (E1), and proximal views (E2, note rhomboidal shape of imprinted substatum); E3, enlargement of corallum edge. F. The largest specimen IPUM−Sic.75. G. Corallum IPUM−Sic.45 with two distinct “rejuvenescence” constrictions (arrows). All from Sinemurian Black Limestones, Longi, Sicily.

Fig. 3. Haimeicyclus haimei (Chapuis and Dewalque, 1853). A. Bivariate biometricplotofcaliculardiameter(CD) versus corallumheight(H).B.Bivariate biometric plot of calicular diameter (CD) versus septal number (S).

Fig. 4. Haimeicyclus haimei (Chapuis and Dewalque, 1853). A. Juvenile specimen IPUM−Sic.93 with 48 septa on polished base (herein in distal view). B. Proximal view of IPUM−Sic.94 attached to the bivalve shell incrusted by juvenile specimen IPUM−Sic.94a with 12 septa (arrows). C. Etched, initial portion of the corallum IPUM−Sic.68 with voids corresponding to position of protosepta (arrows mark position of six septa on half of corallum). D. IPUM−Sic.88 incrusted by serpulid tubes and juvenile scleractinians, in distal (D1) and proximal (D2) views in conventional photographs, and on SEM micrographs (proximal views D3, D4) showing enlargement of twelve septate juvenile (two septa of additional cycle marked with smaller arrows). E. IPUM−Sic.9191 in oblique view (E1) with juvenile (?bud) attached laterally (E2, enlargement). All from Sinemurian Black Limestones, Longi, Sicily.

Fig. 5. Haimeicyclus haimei (Chapuis and Dewalque, 1853), IPUM−Sic.3. A. Distal view with narrowed, “rejuvenated”, calice (arrows on A and B). B. Transverse sections of distal part of calice. C. Proximal part of the calice. D, E. Enlargements of section B). Note “shaggy” surface of transversely sectioned spines (D, E) and spines of first septal cycles embedded in stereome in lower part of corallum (C). Specimen from Sinemurian Black Limestones, Longi, Sicily.

Fig. 1. A. Schematic map of Sicily (Italy) showing geographic position of outcrops with Early Jurassic scleractinians (asterisk). B. Part of geological map of area near Longi village showing position of Sinemurian Black Limestones (asterisk on white bar that indicates geological section showed onC). C.Geologicalsectionshowingstratasampledforcorals(asterisk).B, C after Lentini 1973.