Rivista Italiana di Paleontologia e Stratigrafia

Key-uords: TetractineÌla trigonella, Tetractinella bexagonalis,

Brachiopoda, Athyridida, Middle Triassic, internal characters, ultra-structure. S.E.M.. 3-D recon\trucrion.

Riassunto. Sono analizzate le specie Tbtractinella trígonella(Schlotheim, 182A) e Tbtractinella bexagonalis (Bittner, 1890). Esem-plari della prima provengono dall'Anisico di diverse località delSudalpino e dall'area-tipo di Tarnowitz (Slesia, Polonia). La seconda è

stata studiata su esemplari del Sudalpino. Allo studio tassonomico e

all'analisi morfologica e biometrica dei caratteri esterni, è seguitaun'analisi morfologica dei caratteri interni, mediante sezioni seriate.

Ove possibile, si è condotta un'analisi dell'ultrastruttura dei caratteriinterni al microscopio elettronico a scansione (S.E.M.). Tale analisi ha

messo in luce nuovi elementi nella struttura delle coste dr T trigonellae ha fornito nuovi dati sui caratteri interni di T. bemgonalis. lnfíne,sono state ottenute ricostruzioni in tre dimensioni partendo dai datiottenuti dalle sezioni seriate, consentendo in questo modo il supera-mento del limite bidimensionale imposto dai peels.

Abstract. The species Tètractinella trigonella (Schlotheim, 1 820)

and Tetractinella bexagonalis (Bittner, 1890) are described. The formerhas been studied on specimens from several localities of the Anisian ofSouthern Alps (Italy) and from the type-area of Tarnowitz (UpperSilesia, Poland). The second has been analysed on specimens from theSouthern Alps.

Taxonomic description and morphologic and biometricalanalyses of external characters were followed by a morphologic analy-sis of internal structures using transverse serial sections. The ultra-structural analysis of internal characters provided new informationabout the structure of the ornamentation of T. trigonella (the presence

of tabulae within costae) and new data about the poorly known îbexagonalis. Finallg the internal characters of T. trigoneLla were re-examined using software for l-D reconstruction from serial sectionsto complement rhe tradirional method of study.

Introduction.

The genus Tetractinella Bittner, i890 is a wide-spread brachiopod genus in the Middle Triassic of the\flestern Tethys and of the Germanic Basin. Several

species have been attributed to this genus, î me|y T.

trigonella (Schlotheim, 1820) (type-species), T. bexago-

nalis (Bittner, 1890), T. cornutula (Bittner, 1,9A3), T.

biplicatula (Bittner, 1903) , T. dyactis Bittner (1 890) , and

pagrne 37-50

THE GENUS TETRACTINELLA BITTNER, 1890:MORPHOLOGY, UTTRASTRUCTURE, AND 3D RECONSTRUCTION

NADIA MANTOVANI'

Receioed. Jwly 13, 2A01; accepted January 3, 20A2

T. cislonensis (Bittner, 1890). They are most abundant inthe Pelsonian substage of the Anisian, from where thefirst four species have been reported. They graduallyvanish through the Illyrian and the genus seems to be

represented in the Ladinian only by T. dyactis. The enig-matic species T. cislonensls could straddle the boundarywith the Carnian.

In the presenr paper, the two most abundantspecies of the genus Tetractinella, T. tetractinella and T.

hexagonalis are described with emphasis on the internalcharacters and ultrastructure of the shell. T. cornwtulaand biplicatula were described only from the area aroundSarajevo in Bosnia by Bittner (1903). M. Gaetani (pers.

com., 2001) in 1966 spent several days collecting in theBittner's classical localities of Bosnia, but failed to findspecimens of these species. T, dyactis was recentlyredescribed by Siblik (1994) from the Ladinian of Rax-alpe (Austria) but specimens are heayÌ recrystaliized(Siblik, pers. com., 2000) and therefore were not furtherconsidered for an useful SEM study.

These species were mostly studied towards theend of the nineteenth century (Bittner 1890, 1903;

Loretz 1825; Philippi 1896; Tornquist 1898) and no sig-

nificant advancements were obtained later on.Some of the specimens here studied originates

from Tarnowitz (Upper Silesia, Poland) type-locality ofT. trigonella, and noìil are housed in the MuschelkalkMuseum (Ingelfingen, Germany). The others speci-

mens, collected by M. Gaetani, A. Tintori, E. Torrianiand N. Mantovani, are stored in the Museo di Paleon-tologia of the Department of Earth Sciences, lJniversityof Milan IMPUM).

Systematic description

Classification is according to Alvarez et al. (1998)

for the revised edition of the Treatise on Invertebrate

I Dipartimento di Scienze della Terra, Università degli Studi, Via Mangiagalli 34,I-20133 Milano, Italy, e-mail: nadia.mantovani@unimi.itFresent address: via Empoli 9; I-201.62 Milano, Italy, e-mail: brachiopode@libero.it

tavole 2

38 N. Mantocani

Paleontology.

Order ATHYRIDIDA Boucot, Johnson & Staton, 196,1

Suborder ATHYRIDIDINA Boucor,

Johnson & Staton, 1964

Superfamily Athyridoidea Davidson, 1 881

Family Diplospirellidae Schuche fi, 7891

Subfamily Tetractinellinae Grunt, 1986

Genus Tetractinella Bittner, l89O

Ty.pe-species. Ter ebratu lite s tr igon e llus Schlothe j m, 1 82 O.

Emended diagnosis. Small to medium sized biconr.ex sheils,commonll' with {ew, high, sub-rounded (ìn section) cosrre rn corrc-sponding positions on each valr'e, extending the anterior commlssureto variable degrees. Thin but w-ell developed dental plates, usuall,vjoìned to the later:rl walls; r-ery strong articulation consisting of r.elJder.eloped teeth and deep sockets. Jugum joined, forming a rudimen-tary saddle, jugal stem projccting ventrally, bifurcating to form shortaccessorv lamellae.

Tetractinella trigonella (Schlotheim, 1820)

Text-figs. 1-12; Pl. 1, figs. 1-6,9 -12; Pl.2, figs. 1-6

1820 Terebratulites trigonell.us Schlotheim, p. 2/1.1875 Rhynchonella tetrdctis Lctrerz, p. 800, pl. 2i, fig. a

1890 Spirigeratrigonella - Bittner, p. 17, pI.36, fig.8-31.1896 Spirigera trigonella r,ar. robusta Philippi, p.721,, pL.21, fig. 4 a-c.

1899 Spirigera trigonelÌa - Tornquìst, p. 256.

1903 Spirigera (Tctractinella) trigonella - Bittner, p. 5a7, 532, 567, pl.ZJ, Irg. iJ, i ltg. l+.

Fig. 1 - T. trigoneLla (specimenMPUM 8440). Detaiì of a

costa with two rransverse

tabulae, consisting of second-

arv fibers.

non Trg. l)-lb.1906 Spirigera trigonella - Arthaber, pl. 35, fig. / a, b.

1906 Spirigera (TetractinelLal trígonella - Martelli, p. 1 1/.1912 Spirigera trigonella Ndr. tetrdctis - De Toni, p. 18, pl. 1., fig.1.2 a-

d.

192A Tetractinella trigonella - Diener, p. 63.

1938 Spirigera (Tetractinella) trìgonella - Selli, p. 16, pl. 50, fig. 10-12.

1958 Tetractinella uigonella - Pantìc, p. 60, pl. 1, fig. 1.

1958 Tetractinella trigonella - Sacchi Vialli & Vai, p. 49.

1967 Tetractinella tigonella - Specialc, p. 1087, pl. 79, fig. 'f a, e.

1967 TetractineLLa trigonella - Casatj 3r Gnaccolini, p. 123, pl. 9, fig.10.

1972 Tetractinellatigonella - Siblik, p. 189, text-fig. 11, pl.61, fìg. 1,

Z-8, non fig. 6.

1971 TetractineÌla trígonella - Dagvs, p. 159, text-fig. 10/, pl. 15, fig.I a-d.

1981 Tetractinella trigonella - Giovannoni, p. 211, pi. 5, fig. a,6.? 1.982 Tetractinella trigonella - Kochanor.a &. Pevn,v, p. la, pl. 7, lig. 2.

1,991 TetractineLla trigonella - Siblik, p. 16E, pl. 1, fig. f :r, b.

1993 TenactineLlatrigonella - Iordan, p.51, pl. 1, fig. a.

1993 Tetractinella *ìgonella - Angiolini, p.287, p|. 1, fig. 3-1.1997 Tetracrinella trígonella Tortì & Angiolini, p. 158, pl. i, fig. 11.

1999 Tetractinella trigonella - Sulser, p. 1 16.

Type- locality. Schlotheim based his Térebratulites trigonellus onspecimens from Stubcndorf, Tarnowitz and in the Friedrichsgrube at

Tarnor-itz. All these localitìes rre in the eàsrern prrr of Upper Silesia

(Poland).

Material. 96l decorticated specimens, MPUM 844A (LC/22),MPUM 8441 (TT1/2), MPUM 8442 (TT1le), MPUM s443 (CPA/1),MPUM 8414 (CPA/3), MPUM 8445 (VAF/1), MPUM 8,+46

(vAF/106), MPUM 8447 (YAF/172), MPUM 8418 (G360/2),x'tPUM 8449 (G2231479), MPUM 845A (G223146s), MPUM 8451(.G223 I 48 1), MPUM 81 52 (.G223 / 1 -67 ; G3 6a I 1,3 ; G460/1 3 8, 1 s2,55 8-

569; G51l6a-64) , MPUX{ 8453 (TT1/1,3-8, 10-28; TT3; CPrl;CPA/1,3), l,fPUM 8151 (AF/1-13; VAF/ 2-105, Ia7-176,178-369),

Tbe genws Tetractinella Bittner 39

Fig. : - T. tigonclla (specimen MPUM 8aa0). The roof of a costawith a transverse tabula. The secondan'la;'er thickness is

' major at the roof of cosra.

MPUr,r 84ss (P/1-2), MPUM 84s6 (G6711.-34), MPUM 84s7(G131/1-4; G128/!-4), Mlr{I 1a52/2-112, MHI 1s81/1-165, MHI1723/ 1-22, MHI 1724/ 1-1A, MHI 17251 1-1 1, MHi 17261 1-42, MF{I1727 / 1, M}JI t 728 I I-t3, MFII t729 I 1-51.

The specimens come from the top oI the Cllcare di Angolo(Banco a Brachiopodi - Peisonian, Anisian) of several localities of theGrigna Group (Canalone Porta, Valle dell'Acqua Fredda, Valle deiGrassi Lunghi), from the PeÌsonian of Monte Rite (Cadore, Italy),from Rovegliana near Recoaro, and from the Pelsonian - low-er Illyri-an of Rugialdbach near La Valle (Dolomites). The material at rheMuschelkalk Museum (lngelfingen, German,v) comes from theAnisian of the t,vpe-area of Tarnonitz.

Description

External'characters. Small to medium sizcd bicon-vex shell, outline from sub-pentagonal to sub-oval or

sub-triangular. In the sub-pentagonal specimens, widthexceeds iength and maximum width occurs ar aboutl/z ofmaximum length. In the sub-oval specimens, lengthexceeds width and maximum width occurs at about %-

2/3 of maximum length. In the sub-triangular speci-mens, length exceeds width and maximum width occursat about 2/3 of maximum length.

Hinge curved and anterior commissure rectimar-ginate. Flanks usually very steep and sub-orthogonal tothe commissural plane. For this reason the lateral com-missure is rectimarginate.

Ventral valve, similar in dimensions and in con-vexity to the dorsal valve, convex near the umbonal area,

flattening anteriorly. Short ventral umbo, terminaily notpointed and incurved. Foramen medium sized and sub-circular in outline. Palintrope reduced. Dorsal valve witha very short umbo. A median sulcus is present in bothvalves.

Ornamentation. Radial ornamentarion consists of4 costae on each valve. The costae, sub-squared torounded in section, appear very high, becomingstronger and heavy near the anterior margin. The costae,with rery wide interspaccs, are in corresponding posi-tion on the two valves and .they extend the anteriorcommissure. In several specimens lateral costae definethe flanks of the shell, except for the specimens collect-ed at Monte Rite.

In well preserved specimens collected atTarnowitz (type-area), the costae arevery high and rein-forced internally by transverse structures (similar totabulae) (Figs. 1-2). In decorticated specimens the tab-ulae are lost. Internai tabulae support mainly the high-er part of the costa and begin one ar a rime, at about 1/z

of the maximum length of shell. The number increasesin the direction of the anterior margin and the maxi-mum number occurs anteriorly to the anterior commls-sure (Figs. 3-4). The ultrastrucrure of a costa in thespecimen (MPUM 8440) was investigated in a trans-verse section. The primary layer consists of small crys-tallites oriented perpendicularly to the shell layers. Itsmaximum thickness is 22.2,um. The thickness of thesecondary layer ranges from 38.1 pm near the transversetabula to 209.5 p,m at the roof of the costa. The sec-

ondary layer consists of fibres with a keel ancl saddleprofile. The maximum width of the secondary fibres intransverse section is about 1.5-1.7 p.m and the thicknessis 2-6 p.m (Fig. 5A). tansverse tabulae are built up bylow density secondary fibres. The last seems to lack thecharacteristic keel and saddle profile. The thickness ofeach tabula is variable, ranging from 34.3 pm to 45.7 p,m

(Fig. sB).Dimensions. The width and thickness parameters

are directly proportional to the length of the shell (Fig.6).

Internal characters: morphology and ultrastructure(Fig. Z). S.E.M. analysis of the internal structures on 12

4Q N. Mantooant

Commissuralplane

Fig. 3 - The number of tabulae increases towards the anterior mar-gin: near the umbo the transverse tabulae have not been

observed (Fig. 3.1); at about '/z ol the maximum length ofthe shell transversal tabulae occur (Fig. 3.2, 3.3); the high-est number occurs anteriorly the anterior commissure (Fig.

3.4).

complete specimens (MPUM 8440, MPUM 8441,

MPUM 8442, MPUM 8443, MPUM 8445, MPUM8446, MPUM 8448, MPUM 8449 and MH'I 1723/1.,

MIJI 1,052/2, MHI 1581/1,-2) was performed. Thespecies has shell substance impunctate and it is charac-

terised by the following internal structures:I. Thin but well developed dental plates weakly

curved and partially joined to the lateral walls of thevalve (Fig. 8A). Myotest present along the dental plates,from the ventral valve floor to the dorsal part of the

valve. Dental plates not very long, disappearing at about1.9 - 2.5 mm from the umbo. The secondary fibres ofthe dental plates have a sub-orthogonal trend withrespect to the ventral valve floor.

Ii. Loq short and sub-triangularlyshaped dental flanges that disappear at about 2.3 - 3.0

mm from the umbo.IIi. Very thick ventral valve floor. The maximum

thickness corresponds to the radial ornamentation,where the secondary fibres secretion is greater.

IV A delthyrial plate is present in the first onto-genetic stages (Fig. 7, sections 5-6), but disappears at

about 0.9 - 1.5 mm from the umbo, when the cardinalprocess begins to enter the central umbonal cavity ofthe ventral valve.

V Very wide central umbonal chamber sub-squarein shape (Fig. 7, sections 1-15).

VI. Strong and high cardinal process protruding inthe ventral central cavity (Fig. 7, sections 9-12). Cardi-nal plate wide, weakly concave to the dorsal valve floorand composed of parallel secondary fibres (Fig. 7, sec-

tions 9-12). A "spherical structure" composed of closedcardinal lamellae is noticeable. At about 1.8 - 2.3 mmfrom the umbo, cardinal lamellae begin to open allowingthe attachment of diductor muscles (lamellae are totallyopen at abost 2.6 mm from the umbo and number about11 each side). The aperture direction is from the planeof symmetry to the internal walls of the valve (Fig. 8B).

VII. Dorsal central cavity rather wide (Fig. 8C).The interior of the dorsal valve shows a flat high and

well developed cardinal plate bearing sockets at its side.

VIII. High, rather long (present at a distance of 3

mm from umbo) sub-triangularly shaped myophragm(Fig. 8D), composed of secondary fibres shovzing a con-vex trend towards the ventral part of the dorsal vaive.

IX. Articulation composed of a pair of strong

N2

PLATE 1

All x 1.5, except when specified.

Fig. 1 a-b-c - Tetractinella trigonella (Schlotheim, 1820). Specimen MPUM 8447 (a, ventral valvel b, dorsal valve; c, anterior commissure with ven-

tral valve below).Fig. 2 a-b - Tètractinella trigonella (Schlotheim, 1820). Specimen MPUM 8444 (a, ventral valve; b, dorsal vali'e).

Fig. 3 a-b - Tetractinella trigonella (Schlotheim, 1820). Specimen MPUM 8451 (a, ventral r'.rlve; b, dorsai valve).

Fig. 4 a-b - Tetractinella trigonella (Schlotheim, 1820). Specimen MF{I 1052/3 (a, ventral valve; b, dorsal valve). Muschelkalk Museum (Ingelfin-gen, Germany),

Fig. 5 a-b - Tbtractinella trigonella (Schlotheim, 1820). Specimen MPUM 8450 (a, ventral valve; b, dorsal valve).

Fig. 6 - Tètractinella trigonella (Schlotheim, 1 820). Ventral valve. Specimen MF{I 1727 /1. Muschelkalk Museum (Ingelfingen, Germany) (x1).

Fig.7 a-b - Tetractinella hexagonalìs (Bittner, 1890). Specimen MPUM 8460 (a, ventral valve; b, dorsal valve).

Fig. 8 a-b - Tètractinelk hexzgonalis (Bittner, 1890). Specimen MPUM 8461 (a, ventral valve; b, dorsal valve).

Fig. 9 a-b - Tetractinella trigonella (Schlotheim, 1820). Specimen MIHI 1723/2 (a, ventral valve; b, dorsal valve). Muschelkalk Museum (Ingelfin-gen, Germany) (x2).

Fig. 1 O a-b - Tb*actinella trigonella (Schlotheim, 1 820) . Specimen MIHì 1052/ + (a, ventral valve; b, dorsal valve) . Muschelkalk Museum (Ingelfrn-

gen, Germanv).Fig. 1 1 a-b - Tetractinelk trigonella (Schlotheim, 1 820). Specimen MIHI 1052/5 (a, ventral valve; b, dorsal valve). Muschelkalk Museum (Ingelfin-

gen, Germany).Fig. 12 a-b-c - Tetractinella trigonella (Schlotheim, 1820). Specimen MHI 1581/3 (a, ventral valve; b, dorsal valve; c, a detaìl of the flank orthog-

onal to the commissural plane). Muschelkalk Museum (Ingelfingen, Germany).

PÌ. 1 The genus Tetractinel/a Bittner 41

42 N. Mantopant

teeth, sub-squared in outline, supported b1'two ventrallateral wails and partially by dental plates. They helps tocontrol torsional movement between the two valves.Dorsal surface of the teeth smooth. Deep and sub-ovalshaped sockets (Fig. 7);

X. Internal tabulae ranging in number from one to5-6, supporting the high part of the costae (Figs. 1-4,58).

3-D reconstruction. External and internal struc-tures of a complete specimen from the type-area ofTarnowitz (MHI 1052/2) were reconstructed from seri-aì sections (Figs. 9- I 11.

Three-dimensional reconstructions are used tocomplement the traditional merhod of study, as it was

Fìe. I - T. r,tgonellt l.pecimenMPUlvf 8440). The sectìon

shows the four median costae

in corresponding positions oftwo valves, anteriorll' to the

anterior commissure (where

the number of tabulae is

highest).

suggested by Sandy (1986). This new perspective allowsa better understanding of the main internal characters ofventral and dorsal valves and their evolution from umboto the anterior margin, overcoming the two-dimension-al limitation of peels. The software chosen and thetechniques used are described in Mantovani & Olivini(2001, submitted) . The three-dimensional reconstruc-tion illustrates the following internal characters:

I. Internal surface of valves (r'entral and dorsalvalve floor, roof and lateral walls) (Figs. 9-10) .

II. Delthyrial plate, present in the first ontogenet-ic stages as well (Figs. 9-11).

III. Dental plates (adminicula and dental flanges)(Fis. e).

Fì9. 1

PLATE 2

- Tbtractinellrt trigonella (Schlotheim, 1820). Specimen MPUM 8446. Section at 0.9 mm frorn umbo, showing the delthyrirì pl;rte.- Tetractinella trígonella (Schlotheìm, 1820). Specimen MPUM 8'1.19. Section at 2.3 mm from umbo, showing a detail of an aclminicu-

lum.- Tetracrinella trigonella (Schlotheìm, 1820). Specimen MIHI 1.723/1. Section at 3.6 mm from umbo, shon-ing the secondarv fibres near

the transverse tabula. Muschelkalk X{useum (Ingelfingen, Germanl.).'Tetractinella trigonella (Schlotheìm, 182C). Specrmen MPUM 8149. The articulation composed by verl' strong teeth and deep sock-

CtS.

- Tetractinella trigonelÌa (Schlotheim, 1820). Specimen MPUM t.1.11. Section at 2.15 from umbo, showing the cardrnal process withthe numerous cardinal lan.rellae for the attach of diductor muscles.

- TetractìnelLa trigonella (Schlotheim, 1 820). Specimen MPUN{ 8'{42. Section at 2.1 mm fron umbo, showing the cardinal process. ThecarcLinal lamellae are completely open.

Fio 1

Fio 4

Fio a

Pl. 2 The gettus Tetractincl/d IJittncr 43

"""fÌfr-

1l N. Manto,uani

T. trigonella (specimen MPUM 8+40). A - transverse section of a costa showing the primary and secondary layers. The secondary fibresshow the keel and saddle profile; B - detail of a transverse tabula showing uncompacted secondary fibres.

IV Myophragm (Figs. 9-1 1).

V Cardinal process with cardinal plate (Figs. 9-11).

VI. Articulation between valves (Fig. 11).Intraspecific variability. Intraspecific variability was

observed in the outline (sub-pentagonal or sub-triangu-lar), depending on the length/width ratio; in the maxi-mum length and width of the shell; in the lateral costaeposition (lateral costae may or may not underlie theflariks of the shell); and in the flank inclination withrespect to the commissural plane (from about 9Oo toabout 40'-45'). Specimens collected from Monte Riteare characterised by variability in outline (from sub-pentagonal to sub-oval) and lateral cosrae not underly-ing flanks. The last are nor inclined and not orthogonalwith respect to the commissural plane.

Discussion. T. trigonella is probably the mostwidespread brachiopod species of the Anisian of theWestern Tethys and Germanic Basin. Loretz (1825)erected the new species Rhynchonella tetractis fromAusserprags (Braies Dolomites). De Toni (1,91,2), pre-ferred to consider tetractis as a variety of Spirigeratrigonella. The analysed specimens from Monte Rite are

very similar to specimens illustrated lsy Loretz (1825)and De Toni (1912). The general morphology and theinternal structures of two specimens (MPUM 8448 andMPUM 8449) does not show significant difference incomparisons to the other analysed specimens. Thereforethe species Rhynchonella tetractis Loretz, 1875 is consid-ered as synonym of T. trigonella.

The specimens illustrated by Bittner (1,903, pI. 23,fig. 2a-26) and collected from Studenkovic (Sarajevo

TetractineÍla trigonella (Schlotheim, 1820)

Adlò

A

25

20

15

AWtrTh

Fig.6 - T trigonella. Constant rela-

tionship between width,thicknes' and ìength of rhe

shell.

10

B---./

Length (1)

\t-4/,'----. IV^l

Sez. 1 (10)0.1 mm

/'---1./' .-'----\ \/ \ Li\r-rl \[>/

\\\ /!./\-.-ZSez.8 (x11.5)

1.1mm

È---'i1r' I t. -/ /--l \\ r lrt) \.1 \r I\\^.2 \al9/

Sez.3(x11) Scz.4(x11.5)o-6 mm 0.75 mm

-/ .,^'. \é / \ \vv.'( )r/\'' li-/\-le-lL-l,^(.-r

Scz. 9 {x13)1.2 mm

^-^,/ /^---l \\-1r )1,\''" ,l l') \q-.. p "(-,

fr/ " \.\-F4Ar-\Y " Sez. 13 (xl 1)

1.6 mm

,''>l\vt )È;\\ tll//\ \ l"/U):(-'

\zri-Sez. 10 (x15)

1.3 mm

The genus TetractinelLa Bittner 45

f'.'---'^\,/--\--- I \ t--.\l^r/ ln- i

\\ lt//\./,

Sez. 7 (x12)1.05 m

Fig. 8 - T trigonella. A (specimen

MPUM 8445). Dental plates

weakly curved and partially

.joined to the lateral walls; B

(specimen MPUM 8443).

Detail of the cardinalprocess: the black arrowsindìcare rhc opening dìrec-

tion of the cardinal lamellae;

C (specimen MPUM 844i).Dorsal r;lre nith rery high

myophragm: ! lspecimenMPUM 84,11). Detail of the

myophragm [ormed by rec-

ondary fibres.

,|------''\,/ r-\ \(-..-'/ / \ \-,

\. \t l-',\\\ il,"'\\, it'/t\ /i( \\v2 / I,.,4/-r. S./Àq,xti\

Scz. 12 (x12)1.5 mm

Frg.7 - Serial sections of T trigonella (specimen MHI 1052/2 from rhe type locrlity of Tarnowitz). Distance from the umbo in mm

Sez. 15 (x14)L9 mm

N. Mantotani

Fi- q 3D rcconstructionn'igonelld (spccir.nen

1C52./2). Frontal vien'ing the main intcrn:rltures of ventral and

r';th'es.

o[ T.

MHIshos-struc-dorsal

VENTRAL VALVts

;;:':;

Dentalplate

Delthyrialplate

Articulation

Myophragm

DORSAL VALVE

- 3D reconstruction of 7l

ligonella (specirnen MHIlO5l l;. A dct.r.il of delrhl ri-.rl pi.rte, concJte cardin.rlplate, articulation and dorsalvalve.

Fig. 10

Fig. 1 1 - 3D reconstrucrion of Itrigonella (spccirnen llHI1A52/2). Front;rl viev' shos-ing detail of the artjculationbetn'een the vrlves.

4The genus Tbtactinella Bittner

flg. ll

47

T. trigonella: the separationbetween excurrenr and incur-rent flor-s.

Excurrentflow

sulcus and dorsal fold are thoughr ro separare the planeof anterior excurrenr flow from the plane of lateralincurrent flow, increasing the efficiency of the currenrin the lophophore (Emig 1992). In Z trigonella, theincurrenr flow is thought to be separated from theexcurrent flow by the median costae on the two valves.The couple of the median cosrae defines the excurrentflow area and the lateral costae the incurrent flow areas(Fig. 12).

The flanking position of the lateral costae (sub-orthogonal ro the commissural plane) reduced the aper-ture degree of the sheil opening, allowing the selectionof particle-size that in other brachiopods was obtainedby a"zig-zag" commissure as shown by nud-;ck (197A).

Occurrence. Tetractinella trigonella occurs in theAnisian (Pelsonian and lowermost Illyrian) of theSouthern Alps. It is frequent in the "Banco a brachiopo-di" of Calcare di Angolo from the Grigna Group in ìheWest to the Giudicarie in the Easr, in Lombardy andTrentino. Occasionaliy a few specimens may be collect-ed in the lower part of the Calcare diprezzo. It is alsoabundant in the Recoaro Limestone of the Recoaro area,in the uppermosr parr of the Serla Fm. in the M. Rite(Dolomites), in the Dont/Braies Fms. of the Eastern(Dolomites), in the Anisian of the Northern Alps ofGermany and Austria, in the Lower and UpperMuschelkalk of the Germanic Basin, in the Anisian ofHungary (Balaton Highland), Dinarides, Balkanidesand in the Upper Ladinian of Aghdarband (Iran) (Siblikie88).

lncurrentflow

area, Bosnia) differ from the analysed specimens for dif_ferent number of cosrae. Especiaily the specime., of fig.26 seems to be more similar rc T. dyactis.In the presentpaper, the robustu variety erected by philippi (1g96, pl.21, {ig. 4) from M. Cavallo (Grigna Group) isconsidered to enrer into the intraspecific variability. Thespecimen of Sibllk (1972, pl. 61., fig. 6) is rejectedbecause, more similar to T. dyactis. The single specimendescribed and illustrated by Kochan ova &. pevny (19g2,pI. 7, fig.29) is most probably a parhogenic specimen.

Remarks on the functional morphology of costae. Apeculiar feature of the species are the internal transver-sal tabulae of the costae. I suggest the interpretationthat they have the function to stabilize and reinforce thevery high cosrae in medium energy environmenrs whereornamenrarion is likely to collapse. In fact, the numberof tabulae increases progressively in the direction of theanterior margin, reaching the maximum number (5_6)beyond the main anterior commissure, where the costaeapPear weakest.

Rudnick (1965, 197A), pointing our rhe resem_blance between Tbtractin e lla trigonella and C h e irothyrisflewriausa (d'Orbigny), suggested costae are used as sen-sory "antennae" which carried the sensitive mantleedges, and hence provided the brachiopods with earlywarning. The presence of the inrernal tabulae void thehypothesis proposed by Rudwick. I suggest rhat thecostae extend the anterior commissure, having a similarfunction ro rhe median sulcus and dorsal fold in someSpiriferids. In these Spiriferid brachiopods, the ventral

48

Tetracrinella hexagonalís (Bittner, 1 890)

*)?xr**^ ^ ^

fr-"#a-ro--#fEr-Tft 'n

lt

t€neth (l)

Tetractinella hexagonalis (Bittner, 1890)

Text-figs. 13-14; Pl. 1, figs. 7-8

1890 Spirigera bexagonalis Bittner, p. 156, Pl. 37, lig. 27-28.

1903 Spirigera (EuractinellaT) bexagonalis - Bittner, p. 510, pl. 24,

fig. l3-18, non fig. 19.

1904 Spirigera bexagonalis - Martclli, p. 1 16, pl. 5, fig. /a, b.

1912 Spirigera hexagonalis - De Toni, p. 3,34.

Holotype. Not selected.

Type-locality. The original material described and illustrated

b1. Bittner (1890) cornes from Nagv-Víszonr,- in Hungary Bittnerreported it as orieinating frorn the Trider.rtinus beds. This stratigraph-

ic position is questionablc, because in the Southern Alps the species is

exclusivelv Pelsonian.

Material. 201 specimens decorticated and deformed, MPUM84s8 (G460/475), MPUM 8459 (G460/1e1), MPUM 8460

(G46a1435), MPUM 8461 (Gs1/9e), MPUM 8462 (G46a/426-431,

43 6-47 1, 47 6-49A, 492-5 46: G51/84-98, I 00- 1 65).

Occurrence. All specimcns come from the topmost part ofthe Serla Formation (Anisian, Pelsonian substage) of Monte Rite(Cadore, Veneto, Italf (Farabegoli 6i Guasti 1980, fig. l, for the loca-

tion).

Description

External characters. Small biconvex and sub-

hexagonal shell in outline. Width exceeds length and

maximum width occurs at about l/3-112 of maximumlength. Short and straight hinge sometimes with rMeakly

winged and angular (obtuse angle) cardinal extremities.Anterior commissure more or less uniplicate. Fold

semi-circular in profile.Median sulcus in the ventral valve, starting near

the umbo and becoming larger and deeper towards the

anterior margin. Small ventral umbo not pointed termi-

N. Mantooant

Fio l1 T. bexagonalis. The diagram

shoqs the constJnt relation-

ship bcr*een width, thick-ness and length of the shell.

AWtrTh

nally and not incurved. The Medium sized foramen,

sub-circular to sub-oval in outline. Very reduced ventral

palintrope.Dorsal valve more convex than ventral valve in

particular near the umbonal region. Small sized dorsal

umbo. Fastigium weak.

Ornamentation. The radial ornamentation consists

of four low and rounded costae in corresponding posi-

tion on the two valves. The costae begin at the umbones

and become larger and heavier near the anterior margin.

The lateral costae, less strong than the central costae,

underline the flanks only in some specimens. The Pres-ence of transversal tabulae like in Tetractinella triPonella

s'as not observed.ln some specimens. an ornamentation consisting

of weak growth lamellae occurs in the anterior half ofthe shell. The growth lamellae are denser near the ante-

rior commissure. Micro-ornamentation not observed.

Dimensions. \flidth and thickness parameters are

directly proportional to length (Fig. 13).

Internal characters: morphology and ultrastructure

(Fig. t+). Shell substance impunctate. S.E.M. analysis ofinternal structures on 2 complete specimens (MPUM8458 and MPUM 8459) was performed. The species is

characterised by the following internal structures:I. Very thin and short dental plates (they disap-

pear rt 0.9 mm from the umbo) that are completelyfused to the lateral walls. A myotest along dental plates

is observable.Ii. A delthyrial plate is present at a dis-

tance of about 0.1 mm - 0.3 mm from the umbo.III. Strong and high cardinal Process protruding

in the ventral central cavity.

Tbe genus Tetractinella Bittner

Sez.3 (x24)0.4 mm

49

.r'V""".,i\,iit;',/

Sez. | (x22)0.2 mm

Sez.4 (x22)0.5 mm

Sez. 7 (x12)1.0 mm

Sez. 8 (xll)7.2mm

4\ r-f t

[J1Sez.2 (x22)

0.3 mm

Sez. 5 (x13) Sez' 6 (xl2)0.7 mm 0.8 mm

Fig. 14 - T. hexagonalis (specimen MPUM 8459): internal characters of

IV Articulation between the valves very srrong,like in T. trigonella.

V Low and sub-triangularly shaped myophragm.' Intraspecific variability. Tbtractinella hexagonalis

shows intraspecific variability in the outline, sub-hexag-onal to sub-hexagonally extended along the plane ofsymmetry; in the hinge length, which is longer in thespecimens sub-hexagonal along the transverse direction;in the median sulcus, deeper in the specimens withstronger central costae.

Discussion. The specimen illusrrated by Bittner(1903, pl. 24, fig.19) is rejected because of the presenceof small fastigium. The specimens analysed are very sim-ilar to specimens described by Martelli (1906) and col-lected from Skala Vucetina (Montenegro) in shell lengthand width but are thicker. The specimens described byDe Toni (1,91,2, p. 334) are put doubtfully in synonymybecause they are not illustrated.

Occurrence. Tetractinella bexagonalis beyond thetype-locality occurs in the Middle Pelsonian of MonteRite (this paper) and of Monte Cucco and Monte Tersa-

ventral and dorsal valves. Distance from the umbo in mm.

dia (Friuli, Italy) (Metzeltìn,1,973), in the Anisian stage

of Studenkovic and Blizanac (Sarajevo area, Bosnia),Pocmin (Dalmatia), and Skala Vucetina (Montenegro),

Achnouledgernents. I am deeply grateful to M. Gaetani for hisinterest, help and valuable advice. I am also deeply grateful to M. Sib-lik and M. Sandy for their valuable advices and revisions. Dr. H. Hag-dorn kìndly allowed me to access to the Muschelkalk Museum collec-tions. I am also deeply grateful to R. Gourvennec for help with refer-ences, to S. Renesto and C. Malinverno for their technical assistance.

A very special thanks to A. Rizzi and G. Chiodi for the S.E.M. analy-sis, the photographs of specimens and their fundamental help andfriendship. The three-dimensional reconstruction from the serial sec-

tions could not have been accomplished without the work of G.Olivini.

A

50 N. ,l[antor:ani

REFERENCE,S

Alvarez F., RongJia-Yu & Boucot A.J. (1998) - The classifica-

tion of Athvridid brachiopods. J. Paleont.,72: 827-855,Iol.a Citv .

Angiolini L. (1993) - lJltrastrr:cture of some Pcrnrian and Tri-assic Spirifericle and Athyridida (tsrachiopoda,l. Rio. It.Paleont. Strat., 99: 281-306, Milano.

Arthrbcr G. r'on (1906) - Die alpine Trias des Mediterrrn-Gebictes. Lethtrea geog/tosticd, F. Frech (ed.), 2 Theil-Das Mcsozoicum, 1 (Tri;rs), 223-472, Stutts,rrt.

Bìttnr'r A. (f 890) - Br,rcl.riopoder.r der Alpinen Trtas. Abh. K. K.

GtuÌ. Rcithstttst., l7: l-115, Wicn.Bittner A. (1903) - Brachiopodcn und L;rrnellibrrnchiaten aus

der Trias von Bosnicn, Drlmrticn und Venctien. - ,40lr.

Ib. K. K. Geol. Reichs,otst.,52: 195-612, Wien.Brunton C. H. C. (1990) - Shr-rt tigl.rtlr rrnd protected. MrcK-

innon D.I., Lee D. E. & Campbell J.D. (eds.), lirachiopods througb timc: 197-2a1, Rotterd:rnr.

Casati P & Gnaccolini M. (1967) - Gcokrqia dcllc Alpi Orobìeoccidentrli. Rr",. It. Paleont. Strat., 73: 26-162, Milrno.

Dagys A. (1974) - Triassic Bracl-riopods (nrorphologl', classifi-cation, phvlogcn\,, stratigràphical signifìcar.rce and bio-gcogrrrphv). 'll'ansact. Inst. Geol. Geoph., Ac,ttl. 5ci.,211:1-385, Nor-osibirsk.

De Toni A. (1912) - Brrrchiopodi della Zona a Cer,ttites trinodosus dt Monte Rite in Cadore. lletn. Ist. GeoÌ. R. Uni'-.Padoca, l: 317-351, Padov:r.

Diener C. (1920) - Brachiopoda tiadica. Fossiliurn Cat:rlogusI Animalia, 1O: 1-108, Berlin.Ernig C. C. (1992) - Function,rl disposition of thelophophore in living Brachiopoda. Lethaírr, 25 291-302,

Oslo.Far:rbegoli E. & Guasti M. (1980) - Anisian lithostratigrtrphl'

and paleoeeogr:rphrr of M. Rite (Cadore, SoutheasternDolomites). Ria. It. Paleont. Strdt.,85: 909-930, Milrrno.

GiovannoniM. A. (1981) - Revisionc critica di rlcr.rne specie dibrachiopodi mesoz-oici europei conscr'\'ati ncl Museo del

Serviz.icr Geologico d'Italia. Boll. Ser.-. Geol. It., Ia2:199-224, Roma.

Iordan N{. (1993) - Trirssic brrchiopods of Romania. Pílfv J. &Vóròs A. (eds.), Mesoz-oic Brachiopods of Alpine Europe:.{9-58, Budapcst.

Koch:.Lnoví M. & Pelni J. (1982) - Bivalves and brechiopodsfrom \flettcrstein linrestones of Ostri vrch (MaléKarpatl' Mts.). Zúp. Karpaty Paleont., 8: 7 -1a, Bratislavr.

Loretz H. r'on (1875) - Einige Petrefacten der alpinen Trias aus

den Sùdalpen. Z. deutsch. seol. Ges., 27: 784-841,

Berlin.Mantovani N. & Olivini G. (200 1) - Three-dimensional recon-

structions frorn seriaÌ sections of some Triessic Spir-iferids ar-rd Athyridids (Subr.nittccl to Lethaia, Oslo).

Martelli A. (1906) - Contributo rrl Muschelkalk supcriore dclMontenegro. Paheont. It.. 12: 116-117, Pisa.

Metzeltin S. (1973) - Stratigrafia clel Trias rnedio rrcl rn:rssiccio

del M. Tersadi:r (Carnia). Ri'-. It. PaÌ. Strat.,79:27140A,Milano.

Pantic S. (1958) - Brakhiopodska Fauna sa Planine Bjclirsice(Crna Gora). Bull. Sen'. Géol. Géoph1:s. R. P Serbie,l6:5Z-78, Beograd.

Philippi E. r'on (1896) - Bcitrag zur Kenntniss des Aufbruesund der Schichtcnfolgc inr Crisneqel.tilge. Z. tleutsch.

geol. Ges.,47 : 665-731,Berlin.Rr.rds.ick M.J.S. (1965) - Adaptative honrocolnorphl in the

br;rchiopods Ten'actinc/la Bittncr lnd Cheirothl,ris Rol-her. PalaontoIogiscbe Zeitscbríft, 39 1-262, Stuttgirrt.

Rudn-ick M.Ì.S. (1970) - Living and Fossil Br,rchiopods. V of199 pp. Hutchinson Libr., London.

S.rcchi Virlli G. & Vri A. (1958) - Revisione della faunr trirssi-ca bresciantr: l:r fauna dell'Anisico. Axi Ist. Geol, Unic.PrtLia, 8: -1 [-9 | , P.rr i.r.

Sandl'M. R. (1986) - Brachiopod svstenatics rrnd the trans-

r.ersc serial sectionin g method: some recofiu'nenclationsfor this technique ancl cl:,Lrific:rtion of a tirxonomic prob-lcnr rssistecl br- this rrcthod. R,rcheboer-rf PR. & En'rie

C.C. (eds.), Les Bracltiopoctes fòssiles et itctuels. Biostratig]rFl)ie ,lrr Ptltt,tzoi,lttc: l-1j- 150. Brett.

Schlotheinr E,. F. r'on (1820) - Die Petrefaktenkunde auf ihremjctzigen St.rndpunktc durch die Beschrcibunq seiner

Samrrlung versteinertcr und fossiler' Úberreste des

Thier- und Pflanzenrcichs der Vornelt crlàutcrt i'on E.

F. Baron i'on Schlotheim. S.I, 62: 1-430, Gotl.r:r.

Sclli R. (1918) - Faune dell'Anisico Inferiore dell,r Vallarsa

(Trentino). Giornale di Geologia,2: 1-86, Bologna.

Siblik M. (1972) - Anisian Spiriferidrr and Tcrcbratulida frornthe Slor.ak Kirrs Re gion. Geol. pracé Sprae1,,59: 179-2a2,

Bratislava.Siblik M. (19S8) - Brachiopocla Triadica. Catalogus Fossiliurn

Austriae, Vc 2a: Br:-Lchiopodrr Mesozoica, 1-131, Wicn.Siblik M. (i991) - Triassic Brachiopods fron.r Aghdarband

(NE-Iran). Abh. Geol. Il. A.,38:165-174, Wicn.Sibl;k M. (1994) - The Brachiopod Fauna of the \X/etterstein

Limestonc of the Rrrxalpe (Austria)./aúrb. Geol. Bund.,137:365-381, Wien.

Speciale A,. (\967) - Il Trias in Lornb:rrdia (studi geologici c

paleontoiouici) XXI. Fossili del Trias medio delle velli

Trorrpia e Sabbja. Ric. It. Paleont. Strat.,73: 1055-1 l.+0,

Milano.Sulser H. (1999) - Die fossilien Brachiopodcn der Sch*'eiz und

der angrenzenden Gebiete Jurrgebirgc und Alpen, 315

pp., Tschudv H. & Co. AG (eds.), Zurich.Tornquist A. (189ti) - Neue Beitrage zur Geolor:ie und Palîon-

tologie der Unleebung von Iìecoaro und Schio (imVicentin). Dic Subnodosus Schichten. Z. deutsch. geol.

Gcs., 50: 637-694, Bcrlin.Torti V & Angiolini L. (1997) - Middle Trassic Brachiopods

from Val Prrina, Bersar-nasc Alps, Ital1,. Rir. It. Pttleont.

Snzr., 103: l+9-172, Milano.Urosevic D., Radr-rlor,ic V & Pesic L. (1992) - Middlc Triassic

br,rchiopods from thc Yugoshr.irn Carpatho-Balka-nides. Ret'ue de PaléobiologLe, I l: 469-481, Genèi'e.

Willian-rs A., Rorvcll A.J., Muir-Wood H.N{., Pitrat C.\\{,Schmidt H., Stehli F.G, Agcr D.\X{, Wright A.D., ElliotG.F., Amsdcn T.W, Rudrvick M.J.S., Hrtai K., BiernatG., Mclarcrr D.J., Bor-rcot A.J., Johnson J.G., Steton

R.D., Grant R.E. E Jope H.M. (1965) - Ti"etttise on

In'"'ertebrate Palec,ntolog'. Pt. H: Brachiopode, pp. Hl-H927. Moore R.C. (eds.), L:rlrence, Krtnsrs.